Assembly of electronic blocks on printed circuit boards. Assembly of electronic equipment Designs of hermetic terminals of electronic assemblies
Surface mounting technology is not new, but, unfortunately, it is not fully covered in the domestic literature. The proposed series of articles devoted to this topic will help readers to better understand the features of electronic module mounting technologies. This article describes a number of designs of typical electronic modules and features technological process assemblies of each type.
Modern electronic components
The type of mounting of modules is determined primarily by the number of sides on which mounting is carried out (one-sided or double-sided) and the range of components used. Therefore, it is logical to precede the description of mounting types with a brief overview of the components and housings. The main, most important criterion for the technologist for dividing electronic components into groups is the method of mounting them on the board - in holes or on the surface. It is he who basically determines the technological processes that must be used during installation.
The table contains information on the most common component packages: names, images, dimensions, pin pitch. All dimensions, unless otherwise noted, are in mils (1 mil = 0.0254 mm).
| Rice. 1. TNT components |
 |
| Rice. 2. SMD components |
Table
| Through Hole Components | ||||
| Group | Enclosure types in a group | Enclosure dimensions | Pin pitch | Rice. |
| Single row - SIL | TO-92TO-202, TO-220, etc. | 380x190, 1120x135,420x185… | 100 mil | Rice. 1, a |
| With two rows of pins - DIL | MDIP, CerDIP | 250x381…577x2050 | 100 mil | Rice. 1, b |
| With radial leads | TO-3, TO-5, TO-18 | - | - | Rice. 1, in |
| With axial leads | - | - | Rice. 1, g | |
| Lattices - Grid | CPGA, PPGA | 286x286…2180x2180 mil | 20…100 mils | Rice. 1, d |
| Surface Mounted Components | ||||
| With two rows of pins - DIL | "SOT-23, SSOP, TSOP, SOIC" | 55x120…724x315 mil | 25…30 mil | Rice. 2, a-b |
| With terminals on the sides of the square body - Quad Package | LCC, CQJB, CQFP, CerQuad, PLCC, PQFP | 350x350 mil …20x20 mm | 50 mil…0.5 mm | Rice. 2, in |
| Lattices - Grid | BGA, uBGA | - | 0.75mm (uBGA) | Rice. 3, a-b |
The most interesting from a practical point of view, according to the author, are BGA packages, or rather mBGA, which have 672 pins with a pitch of 0.75 mm. The top of the BGA package is not of particular interest, more notable are its bottom and the internals of this component package. On fig. 3, a shows the bottom surface of the BGA package, on which the ball leads are visible, and in fig. 3b is a sectional view of this body.
Rice. 3. BGA package
Above short review of modern components gives an idea of how large the number of possible options for implementing the installation of modules with different arrangement of them on the board. In addition, another group was not presented in the review - the group of non-standard components (odd form components).
Types of mounting can be divided according to various parameters: by the number of board sides used for mounting (single-sided or double-sided), by the types of components used (surface, lead-out or mixed), by their location on a double-sided module (mixed-separated or mixed). Consider the most common of them, as well as the sequence of technological operations for each type of installation.
Mounting types
Surface mounting
Surface mounting on the board can be single-sided or double-sided. The number of technological operations with this type of installation is minimal.
With one-sided mounting (Fig. 4, a), solder paste is applied to the dielectric base of the board by screen printing. The amount of solder applied to the board must provide the required electrical characteristics of the switched elements, which requires appropriate control. After positioning and fixing the components, the soldering operation is performed by reflowing the dosed solder. In conclusion technological cycle soldered joints are monitored, as well as functional and in-circuit control. On fig. 4a depicts surface-mounted components various kinds: relatively difficult to mount components in PLCC and SOIC packages and easy to mount chip components.
Rice. 4. a, b
For double-sided surface mounting (Fig. 4, b), various implementation options are possible. One of them involves the beginning of the technological process with the operation of applying solder paste to the underside of the board. Then, in the places where the components are installed, a calculated dose of glue is applied and the components are installed. After that, the glue polymerizes in the oven and the solder paste is melted. The board is flipped, solder paste is applied and the components are installed on the top side of the board, after which the top side is reflowed. In this case, single-sided heating furnaces are used for soldering components.
In another implementation of double-sided surface mounting, ovens with double-sided heating are used.
An interesting question is the need to apply glue to the board. This operation is performed in order to prevent the components from separating from the board when it is turned over. Existing calculations show that most components will not fall off the board even if it is turned over, as they will be held by the surface tension forces of the solder paste. For this reason, the operation of applying glue cannot be classified as mandatory.
Mixed-separate mounting
In mixed-remote mounting, through-the-hole (THT) components are located on the top side of the board, and surface mount components are located on the bottom side. In this case, the operation of soldering with a double wave of solder is mandatory. Mixed-separated mounting of components is shown in fig. 5.
Rice. 5. Mixed and spaced mounting
The implementation of this type of installation involves the following sequence of operations: glue is applied to the surface of the board with a dispenser, on which SMD components are installed, the glue is polymerized in an oven, after which the components are installed in the holes, the module is flushed, and control operations are performed.
An alternative option is that the assembly begins with the installation of components in the holes of the board, after which the surface-mounted components are placed. It is used when the molding and punching of the leads of ordinary components is carried out using special tools in advance, otherwise the surface-mounted components will make it difficult to cut the leads passing through the board holes. Components for surface mounting with a high density of their placement, it is advisable to mount in the first place, which requires a minimum number of flips of the board during the manufacture of the product.
Mixed installation
An example of mixed mounting is the installation of both SMD and TNT components (mounted in holes) on the top side of the board, and only SMD components on the bottom side. This is the most difficult type of installation (Fig. 6).
Rice. 6. Mixed installation
There are various options for its implementation. In one of them, glue is first applied to the bottom side of the printed circuit board by dosing, and SMD components are installed on the applied glue. After monitoring the installation of the components, the adhesive is cured in an oven. Solder paste is applied to the top side of the board, and SMD components are then installed on it. Application of solder paste is possible both by screen printing and by dosing. In the latter case, the operations of applying glue and solder paste can be carried out on the same equipment, which reduces costs. However, the application of solder pastes by the dosing method is unsuitable for industrial production due to the low speed and stability of the process compared to screen printing and is justified only in the absence of a stencil for the product or the inexpediency of its manufacture. Such a situation can arise, for example, during the pilot production of a large range of electronic modules, when, due to the large number of processed constructs and small series, the costs of manufacturing stencils are significant.
After installing the SMD components on the top side of the board, they are group soldered by reflow solder paste applied on a screen printer or by batching. After this operation, the technological cycle associated with the installation of surface-mounted components is considered completed.
Further, after manual installation of the components into the holes of the board, joint soldering of all SMD components previously held on the underside of the board with the help of a cured adhesive and already installed lead components is carried out.
At the end of the technological cycle, operations of visual inspection of soldering and control are performed.
In another embodiment of mixed installation, a different sequence of operations is assumed. The first step is to apply solder paste through a stencil, install complex surface mount components (SO, PLCC, BGA) on the top side of the board, and reflow solder metering. Then, after installing the components in the holes of the board (with appropriate trimming and fixing of the leads), the board is turned over, adhesive is applied to it and the components are installed. simple forms for surface mounting (chip components, components in SOT package). They and the leads of the components installed in the holes are simultaneously soldered with a double wave of solder. It is also possible to use equipment as part of one line that provides efficient soldering of components (on the top side of the board) by melting dosed solder and soldering (on the bottom side of the board) with a wave of solder.
It should be noted that in the technological process that implements mixed assembly, the number of control operations increases due to the complexity of assembly in the presence of components on both sides of the board. Inevitably, the number of solder joints and the difficulty of ensuring their quality also increase.
Single-sided output and surface mounting
This technology is known in world practice as solder paste reflow technology and is one of the standard ones in surface mounting technology (Fig. 7).
Rice. 7. One-sided mounting of SMD and TNT
Modules of this type are assembled in the following way: solder paste is applied to the surface of the board, on which SMD components are installed; then the paste is reflowed in an oven, THT components are installed, wave soldering is carried out, after which the assembled module is washed and inspected.
Single-sided output mounting
The technology for assembling such printed circuit boards (Fig. 8) is a standard assembly and assembly cycle using solder wave soldering. This cycle consists of the installation of lead components, their soldering on the wave soldering machine and control operations. Installation of components can be either manual or semi-automatic. The choice of equipment is determined by the required performance. Automation of this type of installation is minimal, and the implementation itself is extremely simple.
Rice. 8. One-sided installation of TNT
This publication is the first article in a series on surface mount. Its logical continuation will be the coverage of the issue of composition production line on which this type of installation is implemented: the need for each type of equipment, its specifications and the role in the technological process, the required composition of personnel and their qualifications, as well as other issues that arise when creating an assembly and assembly production.
Literature
- Schmits J., Heiser G., Kukovski J. A look into the future. Technological trends in the development of electronic components and assembly of electronic modules on printed circuit boards. Translation and adaptation by A. Kalmykov. Components and Technologies, No. 4, 2001.
- www.pcbfab.ru
Send your good work in the knowledge base is simple. Use the form below
Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.
Hosted at http://www.allbest.ru/
annotation
The paper presents the technological process (technological documentation) of assembly and installation of "Devices for measuring parameters and tuning piezoelectric resonators and monolithic filters in the frequency range from 1 to 330 MHz" CPNA-330 for small-scale production, developed based on the results of analysis of design documentation and assembly composition, calculation the manufacturability of the design, calculation and analysis of the release cycle, and a device was developed for performing the operation and cutting the leads to size.
List symbols, abbreviations and terms
zig-lock -- type of terminal molding
IET - electronic equipment product
CD - design documentation
KMO -- through-hole components
SMC -- Surface Mounted Components
MTP -- route technological process
PP -- PCB
TK - terms of reference
TP -- technological process
ERE - electroradioelement
Introduction
The purpose of the thesis is to develop a technological process for the assembly and installation of the CPNA-330 device and equipment for performing technological operations.
To achieve this goal, the following tasks were solved:
The analysis of TK was carried out;
Conducted design and technological analysis of design documentation;
The calculation and analysis of the manufacturability of the electronic cell;
A scheme for assembling a device for serial production (for a given production program) was developed, on the basis of which a route TP was developed;
A technological process for assembling and mounting a device for serial production has been developed;
To solve the tasks set, a systematic approach was used; methods of analysis and synthesis; assembly method electronic means with base part; methods of tabulation and formulary data visualization; design of the technological process of assembly and installation based on the synthesis of standard operations; acquisition of technological documentation by standard technological operations; tooling design using modern CAD systems.
1. DEVELOPMENT OF THE TECHNOLOGICAL PROCESS FOR ASSEMBLY AND INSTALLATION OF THE CPNA-330 DEVICE
1.1 Device description
Purpose "Devices for measuring parameters and tuning piezoelectric resonators and monolithic filters in the frequency range from 1 to 330 MHz" CPNA-330:
Measurement of frequency and equivalent dynamic parameters of piezoelectric resonators;
Continuous visual control of the parameters of piezoelectric resonators during their tuning;
Continuous visual control of the parameters of monolithic piezoelectric filters during their adjustment;
Measuring and plotting the dependence of the change in the parameters of the resonators (Fs, R1, Q) on time;
Measurement of frequency response and phase response of piezoelectric resonators and monolithic piezoelectric filters.
1.2 Analysis of design documentation
The installation for measuring parameters and tuning piezoelectric resonators and monolithic filters is a unit with overall dimensions of 130x256x300 mm. The instrument consists of the following assembly units: housing base, housing cover, front panel, rear panel, as well as a set of electronic cells in the amount of 15 pieces.
The supporting structure of the device is the metal base of the case. The design of the case provides reliable fastening of knots.
Several cells are installed on the base of the case and fastened with screws, including the motherboard. The rest of the cells are installed on the motherboard. Some cells connect to the rear panel. The connection to the connectors on the front panel and the connection between some cells is done with wires.
The cover, front and back panels are attached to the base with screws.
For switching with external devices, a plug-in connection with wires is used.
Body base. The base of the body has a U-shaped symmetrical shape with a wall thickness of 2mm. There are rubber struts on the underside of the case.
Case cover. The housing cover also has a U-shape. It is attached with screws to the rail, to which the base is also attached.
The front and back panels are made of the same material as the cover and base. They are also fastened to the connecting rail with screws. The panels have holes for attaching connectors and buttons.
Electronic cells. The device includes 15 electronic cells, on which ERE of various types are installed. The boards are made according to the second class of accuracy and covered with a protective green solder mask. All holes in the boards are metallized. Some boards have mounting holes for installation in a case.
The 1000 MHz reference oscillator board has metalized holes for attaching output components, a connector, and a micro-assembly. The rest of the components are surface mounted.
ERE can be divided into groups:
1. Lead elements that do not require molding: 32-pin connector, LED (pins are preformed), micro-assembly with ADF4360-7 chip;
2. Output elements requiring molding:
The 10 MHz crystal oscillator has 15 leads, is mounted on a gasket, for single and small-scale production, it is recommended to fix it using the springing of the leads; in large-scale and mass production, fixing is recommended to be carried out at the expense of the conclusions formed in the ZIG-lock;
The resistor assembly, the tuning resistor are fixed either by springing the leads or using a ZIG lock.
3. Leadless elements are installed on the surface of the board.
Mounting of elements on the board is one-sided. With single and small-scale production, it is possible to carry out manual soldering of ERE; in large-scale and mass production, it is recommended to carry out soldering of a group workpiece in an oven, followed by wave soldering of lead elements.
Spatial layout has 2 levels:
1st level - leadless resistors, capacitors, inductors, transistors, diodes and microcircuits;
2nd level - transformers and output components.
Installation of components is carried out starting from the lowest level for the convenience of soldering.
Based on the analysis of the design documentation for the development of the TP for the assembly and installation of the device, it is necessary to provide for a subassembly:
1. Assembly electronic cells.
2. Assembling the housing base and mounting the electronic cells.
3. Assembly of the front and rear panels with preliminary formation of seats for switching elements.
4. Assembly of the housing cover.
5. Checking the device for operability.
To assemble the electronic cell and assemble the device, the following operations should also be provided:
2. Forming and trimming of ERE leads.
3. Installation and soldering of the KMP.
4. Installation and soldering of KMO.
5. Washing the board.
6. Drying the board.
7. Separation of the group fee.
8. Output control of the electronic cell.
9. Cutting and stripping wires.
10. Marking of the device.
11. Packaging of the device.
1.3 Assembly composition analysis
The design of the electronic cell includes a large number of attachments of various sizes and ratings. Elements are grouped according to the way they are installed on the board. IET designations according to the specification, the number of element leads and the number of elements on the board, options for installing elements for a single production are shown in Table 1.3.1.
Table 1.3.1 - Installation of elements on the prototype PP
|
Name |
Installation option sketch |
Notes |
|||
|
R1, R2, R4…R15, R17…R22, C1…C20, L1…L3 |
|||||
|
Gapless mounting, solder fixing of diagonal pins |
|||||
|
U3, D1, D2, D3, Q1 |
Gapless mounting, solder fixing of one pin |
||||
|
Installation with gasket, fixation by spring-loaded terminals |
|||||
|
Gap-free mounting, spring-loaded pins |
|||||
|
Gap-free mounting, spring-loaded pins |
|||||
|
Installation with a gap, fixing by soldering the output |
The clearance is provided by the design of the terminals |
||||
|
Clearance mounting, fixation by terminal design |
The clearance is provided by the design of the terminals |
ERE installation options for a given output volume N = 1700 (small-scale production) are presented in Table 1.3.2.
Table 1.3.2 - Options for installing elements on the PP for a given output volume (small-scale production)
|
Name |
Installation option sketch |
Characteristics of the installation option and method of fixation |
Notes |
||
|
R1, R2,R4…R15, R17…R22, C1…C20, L1…L3 |
|||||
|
U2, U4, U3, T1, D1, D2, D3, Q1 |
No gap installation, solder paste fixation |
||||
|
Clearance mounting, spring-loaded terminals |
The clearance is provided by the design of the terminals |
||||
|
Mounting with gasket, fixing soldering the output |
|||||
|
Gap-free mounting, spring-loaded pins |
|||||
|
Gap-free mounting, spring-loaded pins |
|||||
|
Installation without gap, solder fixing of the output |
The clearance is provided by the design of the terminals |
||||
|
Clearance installation, interference fit |
The clearance is provided by the design of the terminals |
1.4 Calculation and analysis of the coefficient of manufacturability of electronic means
assembly electronic cell wire
Cell manufacturability is assessed according to a complex manufacturability indicator, which is calculated according to the basic manufacturability indicators according to the formula
where and are basic manufacturability indicators and their weighting coefficients.
Cell manufacturability calculation for a given release program.
The coefficients for calculating and analyzing manufacturability for small-scale production of a 1000 MHz reference oscillator are presented in Table 1.4.1.
Table 1.4.1. - Coefficients for calculating and analyzing cell manufacturability for a given output volume
|
Name |
Designation |
Meaning |
|
|
Number of ICs |
|||
|
The number of contact connections obtained by mechanization |
|||
|
Total number of connections |
|||
|
The number of elements prepared by mechanization |
|||
|
Number of mechanized control and adjustment operations |
|||
|
Total number of control and adjustment operations |
|||
|
Number of types of IET ratings |
|||
|
Number of types of denominations of original IET |
The basic indicators of manufacturability of the reference oscillator at 1000 MHz for a given output volume are presented in Table 1.4.2.
Table 1.4.2 - Basic indicators of cell manufacturability for a given output volume
|
Name of the base indicator |
Calculation formula |
Significance coefficient, i |
Notes |
||
|
IC utilization factor |
Nims-number of ICs Niet = Nims + Nere Design indicator |
||||
|
Installation automation factor |
Us-number of mounting connections obtained by an automated or mechanized method. Hm - total number of solder joints Technological indicator |
||||
|
Coefficient of mechanization of preparation for installation |
Hmp.iet-number of elements automatically prepared for installation Hiet-total number of IET Technological indicator |
||||
|
Coefficient of mechanization of control and adjustment |
Hmkm - the number of mechanized control and adjustment operations Hkm - total number of control and adjustment operations Technological indicator |
||||
|
IEP repeatability coefficient |
Ht.iet - number of type ratings of IET. Hiet-total number of IET Design indicator |
||||
|
IET applicability coefficient |
Ht.op.iet - the number of original IET. Ht.iet-number of typical IET Design indicator |
||||
|
Rate of use of progressive forms |
Dpr. - the number of details of the spatial layout of the progressive form. D-total number of spatial layout details Design and technological indicator |
The complex indicator of manufacturability of the reference oscillator at 1000 MHz for a given output volume is determined based on the basic indicators by the formula:
The obtained value of the complex indicator of manufacturability corresponds to the normative complex indicator for small-scale production. In small-scale production, special and specialized equipment is used, while the qualifications of workers must be high.
1.5 Development of a prototype assembly scheme
To assemble and mount the device, a general assembly scheme with a base part is used. As a base part, an assembly unit is selected - the base of the case, on which the electronic cell is installed. For each assembly unit, intermediate assembly schemes are developed, which are combined into general scheme assemblies. The first step is to assemble the front panel of the device. The assembly diagram of the front panel of the prototype is shown in Figure 1.5.1.
Figure 1.5.1 - Front panel assembly diagram
At the next stage, the back panel is assembled, on which the connectors are installed. The rear panel assembly scheme is shown in Figure 1.5.2.
Figure 1.5.2 - Rear panel assembly scheme
The assembly diagram of the electronic cell is shown in Figure 1.5.3.
Figure 1.5.3 - Diagram of the electronic cell assembly
3 cells are attached to the base of the device. The remaining cells are inserted into the main board. The assembly diagram of the entire device is shown in Figure 1.5.4.
Figure 1.5.4 - Scheme of assembly of a prototype
1.6 Development of a route technological process for assembling a prototype electronic cell
The route technological process (MTP) for assembling a setup for measuring parameters and tuning piezoelectric resonators and monolithic filters reflects the sequence of technological operations, contains information about the equipment and the time it takes to complete each operation. MTP is developed on the basis of analysis of design documentation and device assembly scheme.
At the first stage, preparatory operations are performed: assembly of the front and rear panels of the device, unpacking, acquisition of ERE, packaged in containers for convenient and quick search; incoming quality control, molding and trimming of element leads.
Prepared ERE is installed on the board in the order indicated on the assembly diagram.
After installing the ERE, soldering the leads with a soldering iron, quality control of soldering, cleaning and drying of the board is carried out.
The assembled cells are installed on the base of the case, after which the device is closed with a lid.
The assembled device undergoes functional control.
A good device is marked and packaged.
The sequence of operations for assembling a prototype device is presented in Table 1.6.1.
Table 1.6.1 - Initial data for filling out the route map for assembling a prototype converter
|
operation number |
the name of the operation |
Equipment |
Time, sec |
|
|
Housing base assembly |
||||
|
Mounting table |
||||
|
Mounting table |
||||
|
Front panel assembly |
||||
|
Mounting table |
||||
|
Mounting table |
||||
|
Mounting table |
||||
|
Rear panel assembly |
Mounting table |
|||
|
Mounting table |
||||
|
Mounting table |
||||
|
Mounting table |
||||
|
Electronic cell assembly |
||||
|
Unpacking and completing ERE |
Mounting table |
|||
|
Installation of ERE on a printed circuit board |
Mounting table |
|||
|
Soldering with a soldering iron |
Mounting table |
|||
|
Trimming pins |
Mounting table |
|||
|
Flushing the board |
Flushing plant |
|||
|
Drying board |
Dryer |
|||
|
control stand |
||||
|
Instrument assembly |
||||
|
Completing the device |
Mounting table |
|||
|
Installing the front panel |
Mounting table |
|||
|
Rear panel installation |
Mounting table |
|||
|
Mounting table |
||||
|
Mounting table |
||||
|
Mounting table |
||||
|
Wiring |
Mounting table |
|||
|
Installing the Instrument Cover |
Mounting table |
|||
|
Functional control |
control stand |
|||
|
Marking |
Mounting table |
|||
|
Package |
Mounting table |
The total piece time for assembling a prototype cell Tsht = 5030 sec = 84 min.
1.7 Calculation and analysis of the release cycle
The analysis of the output volume of the product is carried out in order to determine the possibility of releasing products according to a given technological process in a given volume within the established timeframe by comparing the piece assembly time of the product with a given production cycle. Based on the results of the analysis of the release cycle, decisions are made on the need to change the technological process, and recommendations are given on the choice of more productive equipment and tooling, the use of group processing methods, and the volume of a batch of products.
The given volume of release Nout = 1700 pieces/year.
According to the given output volume, the release cycle is determined:
TV \u003d F * 60 / Nvyp,
where TV is the release cycle; F - the annual fund of working time (F? 2070 hours) with one-shift work; where Nzap is the launch program.
TV = 2070 * 60/1700 = 73 min / piece
Hence the performance:
Q = 60/TV = 60/73 = 0.82 pcs/hour
From a comparison of the piece assembly time of the cells Tsht (Tsht = 84 min) and the release cycle Tb (Tb = 73 min) it follows that the assembly and installation process, which uses manual assembly methods, needs to be changed in order to reduce the piece time. To do this, it is recommended to use automated installation of components on the board; selective soldering of elements installed in holes; soldering surface-mounted components in an oven; equipment for group washing of printed circuit boards after soldering, to carry out group drying of printed circuit boards after washing.
1.8 Development of an assembly scheme for an electronic cell in mass production
The assembly scheme is necessary to describe the sequence of basic assembly operations and serves as a source of data for the development of a route TS.
To assemble and mount the device, a general assembly scheme with a base part is used. As a base part, an assembly unit is selected - the base of the case, on which the electronic cell is installed. For each assembly unit, intermediate assembly schemes are developed, which are combined into a common assembly scheme.
The first step is to assemble the front panel of the device. The assembly diagram of the front panel of the prototype is shown in Figure 1.8.1.
Figure 1.8.1 - Front panel assembly diagram
At the next stage, the back panel is assembled, on which the connectors are installed.
The rear panel assembly scheme is shown in Figure 1.8.2.
Figure 1.8.2 - Rear panel assembly scheme
The cell assembly scheme is shown in Figure 1.8.3.
Figure 1.8.3 - Assembly diagram of the electronic cell
3 cells are attached to the base of the device. The remaining cells are inserted into the main board. The assembly diagram of the entire device is shown in Figure 1.8.4.
Figure 1.8.4 - Scheme of assembly of a prototype
1.9 Development of a route technological process for assembling an electronic cell in mass production
Taking into account the recommendations for improving the technological process in order to reduce piece time, automated installation of components and soldering of components in an oven are selected to assemble the device in mass production; a device for winding cutting wires is being developed.
The initial data for filling out the route map for assembling the device in mass production are presented in Table 1.9.1.
Table 1.9.1 - Initial data for filling out a route map for assembling a device in mass production
|
operation number |
the name of the operation |
Equipment |
Time, sec |
|
|
Housing base assembly |
||||
|
Housing base assembly |
Mounting table |
|||
|
Preparing the housing base for assembly (drilling holes) |
||||
|
Mounting plates to the base of the housing |
Mounting table |
|||
|
Front panel assembly |
||||
|
Picking parts of the front panel |
Mounting table |
|||
|
Preparing the front panel for assembly (drilling holes) |
Mounting table |
|||
|
Mounting elements on the front panel |
Mounting table |
|||
|
Rear panel assembly |
||||
|
Rear panel assembly |
Mounting table |
|||
|
Preparing the rear panel for assembly (drilling holes) |
Mounting table |
|||
|
Mounting elements on the rear panel |
Mounting table |
|||
|
Electronic cell assembly |
||||
|
Unpacking and completing ERE |
Mounting table |
|||
|
Solder paste application |
||||
|
Installing the KMP on the board |
Machine for installing KMP |
|||
|
Soldering in a multi-zone furnace |
multi-zone furnace |
|||
|
Mounting table |
||||
|
Soldering with a soldering iron |
Mounting table |
|||
|
Trimming pins |
Mounting table |
|||
|
Flushing the board |
Flushing plant |
|||
|
Drying board |
Dryer |
|||
|
Cell functional control |
control stand |
|||
|
Instrument assembly |
||||
|
Completing the device |
Mounting table |
|||
|
Installing the front panel |
Mounting table |
|||
|
Rear panel installation |
Mounting table |
|||
|
Installation of electronic cells on the base of the case |
Mounting table |
|||
|
Installing electronic cells on the main board |
Mounting table |
|||
|
Fixation of cells installed on the main board |
Mounting table |
|||
|
Wiring |
Mounting table |
|||
|
Installing the Instrument Cover |
Mounting table |
|||
|
Functional control |
control stand |
|||
|
Marking |
Mounting table |
|||
|
Package |
Mounting table |
The total piece time for assembling a cell in serial production Tsht = 73 min. The obtained value of the unit assembly time of the voltage converter is equal to the cycle for a given output volume (Tv = 73 min/piece), which ensures the assembly of the device in mass production in accordance with production program release.
1.10 Development of a route-operational technological process
On the basis of the route technological process, a route-operational technological process is being developed. The initial data for the route-operational TP are presented in Table 1.10.1.
Table 1.10.1 Initial data for filling out a route-operational card for assembling a device in mass production
|
operation number |
the name of the operation |
Equipment and accessories |
Materials and modes |
||
|
Housing base assembly |
|||||
|
Housing base assembly |
Mounting table |
||||
|
Unpack the container |
Packing containers, scissors |
||||
|
Remove the body part from the container, check visually and put it into the technological container |
|||||
|
Repeat transition 02 for all parts of the body base |
|||||
|
Preparing the housing base for assembly (drilling holes) |
Mounting table |
||||
|
Remove the base from the technological container |
Technological packaging |
||||
|
Install the base into the drilling fixture |
|||||
|
Remove the base in a container |
Technological packaging |
||||
|
Mounting plates to the base of the housing |
Mounting table |
||||
|
Remove the housing base, plates and required amount screws from containers |
Technological packaging |
||||
|
Fix the plate on the body base with screws and put the body base into the container |
Screwdriver manual |
||||
|
Repeat transitions 01 - 02 for the second plate |
|||||
|
Front panel assembly |
|||||
|
Picking parts of the front panel |
Mounting table |
||||
|
Unpack the container |
Packing containers |
||||
|
Remove the front panel part from the container, check visually and put it into the technological container |
Packing containers, technological containers |
||||
|
Technological packaging |
|||||
|
Preparing the front panel for assembly (drilling holes) |
Mounting table |
||||
|
Remove the front panel from the technological container |
Technological packaging |
||||
|
Drill a hole according to the drawing |
|||||
|
Repeat transition 03 for all holes |
|||||
|
Remove front panel |
Technological packaging |
||||
|
Mounting elements on the front panel |
Mounting table |
||||
|
Remove the elements of the front panel from the container |
Technological packaging |
||||
|
Install the element on the front panel and, if necessary, fasten with screws |
Screwdriver manual |
||||
|
Repeat transition 02 for all front panel elements |
|||||
|
Rear panel assembly |
|||||
|
Rear panel assembly |
Mounting table |
||||
|
Unpack the container |
Packing containers |
||||
|
Remove the part of the back panel from the container, check visually and put it into the technological container |
Packing containers, technological containers |
||||
|
Repeat transition 02 for all front panel parts |
|||||
|
Dial the required number of screws and put in a technological container |
Technological packaging |
||||
|
Preparing the rear panel for assembly (drilling holes) |
Mounting table |
||||
|
Remove the rear panel from the technological container |
Technological packaging |
||||
|
Install the panel in the drilling fixture |
|||||
|
Drill a hole according to the drawing |
|||||
|
Repeat transition 03 for all holes |
|||||
|
Remove back panel |
Technological packaging |
||||
|
Mounting elements on the rear panel |
Mounting table |
||||
|
Remove the elements of the rear panel from the container |
Technological packaging |
||||
|
Install the element on the rear panel and, if necessary, fix with screws |
Screwdriver manual |
||||
|
Repeat transition 02 for all back panel elements |
|||||
|
Electronic cell assembly |
|||||
|
Unpacking and completing ERE |
Mounting table |
||||
|
Remove the printed circuit board from the packaging container and put it into the technological container |
Packing containers, technological containers |
||||
|
Remove the ERE from the packaging container, visually check for the absence of external defects and put it into the technological container according to the drawing and the packing list |
Packing containers, technological containers |
||||
|
Repeat transition 01 for all ERE |
|||||
|
Solder paste application |
Solder paste applicator |
||||
|
Remove the printed circuit board from the technological container |
Technological packaging |
||||
|
Install the printed circuit board in the installation |
|||||
|
Apply solder paste |
Stencil, squeegee |
||||
|
Remove PCB from installation |
|||||
|
Installing the KMP on the board |
Machine for installing KMP |
||||
|
Fasten the printed circuit board in the installation |
|||||
|
Carry out the installation of elements |
|||||
|
Remove the printed circuit board from the installation and put it in a container |
Technological packaging |
||||
|
Soldering in a multi-zone furnace |
multi-zone furnace |
||||
|
Remove the printed circuit board from the container |
Technological packaging |
||||
|
Install board on conveyor |
|||||
|
Carry out soldering |
|||||
|
Remove the printed circuit board and put in a container |
Technological packaging |
||||
|
Visually check the soldering quality |
Technological packaging |
||||
|
Installing KMO on a printed circuit board |
Mounting table |
||||
|
Remove the component from the container and install it on the printed circuit board according to the drawing |
Technological packaging |
||||
|
Bend component leads |
Pliers |
||||
|
Repeat transitions 01-02 for all ERE installed on the PP |
|||||
|
Soldering with a soldering iron |
Mounting table |
||||
|
Install the board in the board soldering tool |
|||||
|
Solder the element leads to the contact pads |
Soldering Station |
Solder POS-61 GOST 21931-76. T°=260+200C |
|||
|
Repeat transition 02 for all KMOs |
|||||
|
Check soldering quality visually |
|||||
|
Remove the board from the soldering tool and put it in a container |
Technological packaging |
||||
|
Trimming pins |
Mounting table |
||||
|
Remove the board from the container |
Technological packaging |
||||
|
Trim ERE leads |
Side cutters |
||||
|
Repeat transition 02 for all ERE |
|||||
|
Put the board in the technological container |
Technological packaging |
||||
|
Flushing the board |
Flushing plant |
||||
|
Transfer the board from the container to the container for washing |
|||||
|
Place the container with the boards in the washing unit and keep in the mixture at the set mode |
Container for washing |
Alcohol-gasoline mixture (1:1) The temperature of the mixture To = 70 ± 5 ° C, time t= 10-15 |
|||
|
Remove the board from the container for washing, check the quality of the cleaning visually and put it in the container |
Technological containers, containers for washing |
||||
|
Drying board |
Dryer |
||||
|
Transfer the board from the container to the drying tray |
Technological packaging, drying tray |
||||
|
Repeat transition 01 for all boards |
|||||
|
Place the pallet with the boards in the drying cabinet and hold at the set mode |
Drying tray |
Temperature Т°= 60±50С, time t= 10 min |
|||
|
Remove the tray with boards from the drying cabinet, place on the table and keep at room temperature |
Drying tray |
Room temperature, time t= 10-15 min |
|||
|
Transfer the board from the drying tray to the technological container |
Drying tray, technological packaging |
||||
|
Cell functional control |
control stand |
||||
|
Remove the cell from the container and install it in the stand for control |
Technological packaging |
||||
|
Check the functioning of the cell according to the control instructions |
|||||
|
Remove the cell from the stand and put it in a container |
Technological packaging |
||||
|
Instrument assembly |
|||||
|
Completing the device |
Mounting table |
||||
|
Remove the device component from the packaging container and place it in the technological container |
Packing containers, technological containers |
||||
|
Repeat transition 01 for all instrument components |
|||||
|
Installing the front panel |
Mounting table |
||||
|
Remove the front panel and the base of the case from the container and install on the base of the case, aligning with the holes in the base |
Technological packaging |
||||
|
Fix the front panel with screws |
Screwdriver manual |
||||
|
Put the device in the container |
Technological packaging |
||||
|
Rear panel installation |
Mounting table |
||||
|
Remove the rear panel from the container and install on the base of the case, aligning with the holes in the base |
Technological packaging |
||||
|
Fix the back panel with screws |
Screwdriver manual |
||||
|
Put the device in the container |
Technological packaging |
||||
|
Installation of electronic cells on the base of the case |
Mounting table |
||||
|
Remove the device from the container |
Technological packaging |
||||
|
Remove the electronic cell from the container, aligning it with the holes in the base |
|||||
|
Fix the cell with screws |
Screwdriver manual |
||||
|
Repeat transitions 02-03 for the remaining cells mounted on the base |
|||||
|
Installing electronic cells on the main board |
Mounting table |
||||
|
Remove the electronic cell from the container and insert it into the main board |
Technological packaging |
||||
|
Repeat transition 01 for all cells mounted on the main board |
|||||
|
Fixation of cells installed on the main board |
Mounting table |
||||
|
Remove the components for fixing from the container |
Technological packaging |
||||
|
Fix cells with screws |
Screwdriver manual |
||||
|
Wiring |
Mounting table |
||||
|
Unwind and cut the wire to the length indicated in the drawing |
Technological containers, ruler, device for cutting wires |
||||
|
Remove the insulation and strip the ends of the wire on both sides |
Pliers |
||||
|
Tin the ends of the wire on both sides |
Bath for tinning |
Solder POS-61 GOST 21931-76, bath temperature T°=260+200C |
|||
|
Carry out the installation of wires according to the wiring drawing |
|||||
|
Repeat steps 1-4 for all connector wires |
|||||
|
Installing the Instrument Cover |
Mounting table |
||||
|
Remove the cover of the device from the container and install it on the base of the case, aligning it with the holes in the base |
Technological packaging |
||||
|
Fasten the device cover with screws |
Screwdriver manual |
||||
|
Functional control |
control stand |
||||
|
Check the operation of the device according to the control instructions |
|||||
|
Marking |
Mounting table |
||||
|
Remove the plate from the container |
Technological packaging |
||||
|
Apply glue to the plate and stick on the cover of the device housing by lightly pressing |
Glue PU-2 OST 4GO.029.204 |
||||
|
Keep the device in air at room temperature |
Room temperature, time t= 30 min |
||||
|
Package |
Mounting table |
||||
|
Remove the device from the container and pack the device in plastic bag |
Scissors, technological containers |
Duct tape |
|||
|
Place the plastic bag with the device in the packing box |
|||||
|
Enclose the accompanying documentation in the shipping box |
|||||
|
Close the lid of the packaging box and secure with adhesive tape |
Duct tape |
1.11 Draft process
50 Installing items on the front panel
70 Mounting elements on the rear panel
90 Installing the KMP on the board
110 Installation of KMO on a printed circuit board
120 Soldering with a soldering iron
210 Installation of electronic cells on the main board
230 Wiring
240 Fitting the instrument cover
Part 2 DEVELOPMENT OF RIGGING
2.1 Technical task for the design of a wire cutter
2.1.1 Purpose
The device is designed for cutting wires of a given length in aisles from 1 cm to 10 cm.
2.1.2. Design requirements
Develop a design for cutting wires to size that meets the following requirements:
- the device must provide the required range of wire lengths;
- the productivity of the device must correspond to the given output volume;
- the device must be of a design that allows easy filling of coils with wires;
- the device for cutting wires must be designed for manual cutting;
- the design of the device for cutting wires should be easy to operate, have low cost at high performance.
2.1.3 Kinematics
The working movement of the knife occurs in a vertical plane.
2.1.4 Placement and installation
The fixture must be placed on the installer's table.
2.1.5 Operating conditions
Equipment designed to work in the air production premises: temperature environment from -20 to +600C, relative humidity up to 98% at temperatures up to 350C. The room must be ventilated, during operation, sharp fluctuations in temperature are unacceptable.
The equipment must be protected from the ingress of large particles of dust, sand on the working surfaces.
During storage, the equipment should be packed in a container in oiled paper.
2.1.6 Specifying security measures
In order to avoid accidents, trained personnel are allowed to work with the device.
2.1.7 Setting
Carry out a trial run of the device to check the force and direction of the knife after assembling and lubricating the moving parts. If necessary, re-adjust the device.
2.1.8 Reliability
The design of the tooling elements and the materials of the elements must ensure the reliability required for small-scale production. In the design of the device, the maximum use of standard, unified and interchangeable products.
2.1.9 Data sources
When developing a design, use tooling prototypes developed at the Department of Design and Production Technology of ES, the base enterprise where the technological practice took place, standard parts from the catalog - the reference book "Technological equipment for cold sheet stamping", atlases of designs of typical parts.
2.2 Tooling design calculations
Installation force calculation.
Since the round wire is cut with a straight knife, the calculation is carried out according to the following formula
where is the number of pins cut at the same time, in this case.
- clamping force.
- wire cross-sectional area
.
where is the tensile strength of the material.
For ordinary carbon steel.
- the number of places where the pressing force is applied, in this case.
where, is the area under the clamp, .
.
The value of the required force obtained as a result of the calculation satisfies the cutting forces using auxiliary mechanisms.
2.3 Description of the tooling assembly sequence
The device is assembled in the following sequence: coil assembly, cutting knife assembly, limiter assembly; general assembly of the resulting assembly units, casing, ruler and clamp. The basis of the assembly is the platform, on which other assembly units are installed. Bushings are pressed into holes.
2.4 Description of tool operation
Performing a wire cutting operation:
1. Set the limiter to the required wire length using ruler 4.
2. Unwind the wire of the required length from the spool.
3. Fix the wire with a clamp.
4. Press the knife handle 2 as far as it will go (there will be a wire cut).
5. Release the knife (it will return to its original position due to the spring).
6. Put the cut wire into a technological container.
1. The developed technological process of assembly and installation of the CPNA-330 device ensures the production of products in mass production.
2. Device for cutting wires can reduce the labor intensity of the preparatory operation and reduce the unit assembly time of the product.
List of sources used
1. Design and technological design of electronic equipment / Ed. Shakhnova V.A., M.: Publishing house of the Moscow State Technical University named after N.E. Bauman, 2012.
2. Gridnev V.N. Lectures on the course "EMU Technology" 2007.
3. Zhuravleva L.V. Lectures on the course "EMU Technology" 2009.
Featured on Allbest.ur
Similar Documents
Analysis of the manufacturability of the product design, calculation of manufacturability indicators, development of a technological assembly scheme. Analysis of route technology options, selection technological equipment and tooling, process design.
term paper, added 06/12/2010
Development of a set of technological documentation for the manufacture of a stroboscope: analysis of the manufacturability of the product design, drawing up a technological scheme for assembling the product. Carrying out an analysis of options for the route technology of assembly and installation of the part.
term paper, added 10/14/2010
Determining the type of production. Formation of the technological code of the product. Calculation of the manufacturability of the design and ways to improve it. Development of a technological scheme for assembling a timer. Selection and description of equipment and tooling for assembly and assembly work.
term paper, added 03/04/2015
Development of technology for assembly and installation of low-frequency amplifier drivers. Analysis of route technology, substantiation of technological equipment, selection of the optimal variant of the technological process. Design of the assembly and installation site.
term paper, added 06/19/2010
The purpose of the power supply control device, its technical characteristics. Development block diagram. Calculation of device reliability. The route of manufacture and stages of the technological process of assembling the product. Analysis of the manufacturability of the design.
thesis, added 11/22/2016
Description of the block diagram and principle of operation of the USB-ionizer. The choice of radioelements and their technical parameters. Design and manufacture of printed circuit boards. The technical process of assembly and installation of tool nodes computer science. Appearance devices.
term paper, added 04/29/2011
Development of technological processes according to unified system preparing the production of the H21e transistor meter. Analysis of the type, conditions and annual release program. The route of the assembly design scheme, equipment selection, installation optimization.
term paper, added 01/10/2011
Determination of indicators of manufacturability of instrument design. Rules for constructing technological assembly schemes. Development of the assembly process. Design of technological equipment and specialized equipment of all kinds.
abstract, added 11/07/2008
Technological process (TP) as a basis production process. Development of TP for assembly and installation of low-frequency amplifier drivers. Product design analysis. Design of the assembly and installation site, equipment for assembly and installation works.
term paper, added 06/21/2010
Consideration of the manufacturability of the design of the current amplifier. Learn how to design an assembly diagram with a base part. Carrying out a feasibility study of route technology options. Basic safety rules for the operation of equipment.
The structure of the assembly process.
Assembly and installation operations are the most important in the technological process of manufacturing electronic components, since they have a decisive influence on the technical characteristics of products and are highly labor intensive (up to 50-60% of the total manufacturing labor intensity). At the same time, the proportion of IEP preparation for installation is about
10%, installations - more than 20%, soldering - 30%. Automation and mechanization of these groups of operations gives the greatest effect in reducing the complexity of manufacturing products. The main ways to improve efficiency are: the use of automated equipment, group processing of IEP, the introduction of a new element base, such as surface-mounted elements.
The technological process of automated assembly consists of supplying components and parts to the installation site, orienting the leads relative to mounting holes or pads, and fixing the elements on the board. Depending on the nature of production, assembly can be performed:
– manually with indexing and without address indexing;
– mechanized on pantograph;
– automatically in parallel on automatic stackers and sequentially on automatic machines or automatic lines with computer control.
The supply of elements to the installation site during automated assembly occurs by loading cassettes with IEP and boards into the magazines and drives of the machine, capturing the IEP by the installation head and positioning. As a rule, cassettes are loaded manually, and only in GAP this operation is performed using automatic Vehicle. The remaining operations on the assembly machine are carried out without the participation of the operator. Boards with mounted IEP are removed from the machine manually or automatically and sent to the polymerization of the adhesive.
Next, the board goes to a light-mounting or ordinary assembly table, where IEP of little use are installed. After soldering, washing off flux residues and correcting defects, the assembled board undergoes visual and functional control. The final step in the assembly process is the application of a waterproof coating.
Fig.5.1. Scheme of a typical process of assembling blocks on a PCB.
The use of manual assembly is economically beneficial in the manufacture of products no more than 15-20 thousand pieces. per year in batches of 100 pcs. At the same time, no more than 100 elements, including up to 20 ICs, can be located on each board. The advantages of manual assembly are: high flexibility when changing production facilities, the possibility of constant visual control, which allows you to detect defects in boards or components in a timely manner and eliminate the causes of marriage. Disadvantages - low productivity, significant labor intensity of the technological process, the use of highly qualified workers.
With production volumes of about 100-500 thousand pieces. per year with up to 500 elements located on the board, it is economically feasible to use a mechanized assembly with a pantograph. At the same time, high flexibility is combined with greater productivity than with manual assembly. In conditions of mass production of the same type of household EA products (0.5-5 million pieces per year), it is advisable to use automated equipment (automatic machines) or automatic lines with computer control.
The structure of a typical process for assembling electronic equipment blocks on printed circuit boards is shown in fig. 5.1.
Preparation of ERE and IC for installation.
Preparation of hinged elements for installation includes the following operations: unpacking of elements, incoming inspection, control of solderability of terminals, straightening, molding, cutting, tinning of terminals, placement of elements in technological containers.
The ERE manufacturer must ensure that solderability is maintained for a specified period. However, in practice, only in Japan, with its short distances and high discipline of deliveries, no more than 70% of the ERE is subject to installation "from wheels", in our country the delivery and storage periods may overlap the warranty ones.
From the manufacturer, ERE come in a variety of containers. Most of it is designed for loading units of assembly machines, however, some of the elements, including ICs, are supplied in individual satellite containers made of antistatic heat-resistant material.
To unpack ICs in type 4 cases, automatic models 141-411 or AD-901 and AD-902 are used, the technical data of which are given in Table. 5.1. Unpacking the container consists in removing a thin plastic cover from the body by transverse compression with the help of two rods that come into contact with the edges of the cover and, approaching each other, bend it and disengage from the body. The released cover is carried away into the collection container by a jet of compressed air, and the IC slides along the guide into the receiving cassette. Automatic machine 141-411 loads ICs into rack cassettes, and automatic machines AD-901 and AD-902 load them into direct-flow ones.
Table 5.1. Characteristics of IC unpacking machines.
Shelf and direct-flow cassettes are used for intra-factory transportation of ICs with planar leads. In the first ICs lie perpendicular to the longitudinal axis of the cassette, each in its own compartment, held by the leads. The issuance of the IC is carried out using the pusher of the assembly machine. In the second, the ICs lie longitudinally along the axis, one after the other. The cassettes are installed vertically on the assembly machine, and the IC is unloaded under the action of gravity and the electromagnetic cutter of the piece-by-piece issuance mechanism.
Resistors and capacitors with axial leads are supplied glued in a double-row adhesive tape on a fabric basis. Pasting into the tape is carried out on special machines, observing the polarity of the elements. A coil with a diameter of 245-400 mm and a width of 70-90 mm contains up to 1-5 thousand ERE. In order to avoid adhesion of adjacent turns, the winding is carried out with an interlayer gasket tape made of cable paper. With the advent of "leadless" IEP, tape media with internal slots have been proposed. Media width 8, 12 and 16 mm. The nests are sealed with polyester film with a preheated tool.
Options for forming ERE leads and installation on boards must comply with OST 4010.030 - 81 (Fig. 5.2).
Figure 5.2. Options for installing IET on boards
Option I is used to install elements on single-sided boards with significant mechanical loads. In this case, a U-shaped molding of the terminals of the elements is used. Option II applies to DPP and MPP. It corresponds to the "zig"-forming of the conclusions. For leads up to 0.5 mm in diameter R min = 0.5 mm, for pins
0.5–1.1 mm R min = 1mm. Option III is recommended for a dense layout of elements on the board, IV - for the board-to-board design of the block, V - for transistors with significant mechanical loads and preservation during dismantling, VI - for ICs with planar outputs. To fix the ERE on the board, the formation of a “ridge” is used on one of the conclusions of the ERE in installation options III and IV.
The installation dimension must be a multiple of the grid spacing (2.5 mm or 1.25 mm) and provided by the tool H 12, H 13, shafts h 12; bending radii +0.3 mm, the rest IT 14/2.
Forming-bending force of planar terminals is calculated by the equation:
where k- coefficient that determines the state of the surfaces of the punch
and matrices (1.0 - 1.2);
b- output width, mm;
δ is the lead thickness, mm;
σ b– yield strength, MPa;
R pr - terminal clamping force, which is (0.25-0.3) R;
For installation variant IIa "zig"-forming of conclusions is carried out according to the scheme shown in fig. 5.3.
Rice. 5.3. Scheme for "zig"-forming the conclusions of radioelements:
a- output bending b- the formation of a "ridge".
In feed discs 1 there are grooves into which the elements are fed by fixed shaping 2. The feed discs receive continuous rotation. Spring-loaded punches built into discs 3, which, when running on the levers, acquire translational motion and form a "zig" on the conclusions. Cam 4 pushes the element 5 from the grooves of the disk into the container.
Zig size FROM calculated by the formula:
where d 0 , d- hole and outlet diameters, respectively.
The mechanization of the process of preparing leads for installation is carried out by using technological devices, semiautomatic devices and automatic machines, selected depending on the design of the ERE and the type of production. Semiautomatic device (Fig. 5.4), designed to prepare ERE leads with axial wire leads and a cylindrical
Rice. 5.4. Semiautomatic device for preparation of radioelements for tinning of leads.
body shape, performs the following operations:
- straightening of conclusions,
- control of ERE by electrical parameters with sorting "good" - "not good",
- stripping and trimming the leads,
- laying ERE in technological cassettes.
Radioelements 7 are manually loaded into the rails 2, along which, with the help of a cutter 3 fed into the straightening mechanism 4 one at a time, then in clips 6 control mechanism 5. The straightening of the leads is carried out with the help of spring-loaded punches. Control and sorting by electrical parameters is carried out by a device connected to the clamps 6. In the presence of a defective element, the device sends a signal to the defect cut-off mechanism 7 and the part is dropped from the rotor. High-quality ERE enter the stripping mechanism 8, where various contaminants are removed with metal brushes. Next, ERE are fed into the trimming mechanism 9, after which they are loaded into a technological cassette 10.
Straightening of conclusions in small-scale production, it is carried out either manually using tweezers and pliers, or in a straightening device (at the same time
20 - 50 conclusions of the ERE model GG 1422-4101 with a capacity of 500 pcs / h). To prepare ERE and IC for assembly, use various equipment(Table 5.2).
Table 5.2. Equipment for the preparation of ERE and IMS.
| Name, type | Type ERE, IC | Productivity, piece/h | Drive, power, W | Dimensions, mm |
| Semi-automatic preparation of resistors and diodes, GG-2420 Installation for straightening and trimming of transistor leads GG-2293 Machine for U-shaped forming of leads ERE, GG-1611 Machine for forming microcircuit leads, GG-2629 Semi-automatic, ARSM2.230.000 Semi-automatic, GG-2125 | MLT-0.195; 0.25; 0.5; 1.0; 2D503; 509. MP42, MP416, GT309 MLT-0.125, 0.25, 0.5 1-1MS 14-1404. 14-3 KM options III, IV Corps 301.12-1; 401.143 | Electromechanical, 50 Electromagnetic, 80 Electromechanical, 180 Electromechanical, pneumatic, 500 Electromechanical, pneumatic, 800 Electromechanical, 180 | 600×500×800 295×215×275 330×380×405 900×400×1500 2200×1000×1500 335×300×305 |
The leads can be tinned both before and after molding by immersion in molten solder. For flux hot tinning of IC leads (case 401.14-3), an automatic model GG-2630 is used. The productivity of the machine is 900 pcs/h, the solder temperature control limits are 200-280 °С with an accuracy of ±5 °С. Tinning of the ERE leads in a group way is carried out on a mechanized installation GGM2.339.002. Its productivity is 400 cassettes / h, the exposure time of cassettes in flux and solder is 1.5 -3 s.
Solder pressing - one of the ways to fix a strictly metered amount of solder wire on the IC leads by its deep plastic deformation. The solder is held on the leads due to the mechanical jamming of the protrusions squeezed into the space between adjacent leads. Usually, for leads with a cross section of 0.3 × 0.1 mm (case 401.14, etc.), solder wire with a diameter of 0.3-0.4 mm or tubular solder with a flux core with a diameter of 0.5 mm is used.
The placement of discrete ERE in the technological container allows to increase the productivity of the assembly and mechanize the installation of elements on the boards. Adhesive tape is also used as a container, into which ERE is glued mainly with axial leads according to the program. Pasting is carried out on the GG-1740 installation. In technological cassettes, ERE are loaded into accumulators, from where, according to the program, they are fed to a transport device, moving along which they enter the gluing zone. Productivity of the machine is 2400 pcs/h, the number of elements in one program is 2-12 pcs, pasting step S multiple of 5 mm, tape width 6 or 9 mm. Polar IET are glued into the tape in a uniquely oriented position (Fig. 5.5, a).
Rice. 5.5. Packing IET in a single-row tape (a) and in a cassette (b)
Elements with unidirectional leads are glued into a single-row perforated tape 18 mm wide. Paste pitch 15 mm, distance between pins 2.5 or 5 mm. KG and IC type transistors are supplied in special straight-through single-strand technological cassettes (Fig. 5.5, b).
Approved by the editorial and publishing board of the university
UDC.621.396.6.001.63
Vinnikov, V.V. Electronic Design Fundamentals: tutorial: in 2 books. Book. 2 / V. V. Vinnikov. - St. Petersburg: Publishing house of SZTU, 2009. - 223 p.
The textbook has been developed in accordance with the requirements of state educational standards of higher professional education.
The second book of the manual deals with issues related to design engineering; protection of ES structures; designing ES taking into account the requirements of ergonomics and design.
The textbook is intended for students of the specialty 210201.65 - "Design and technology of electronic means" and the direction of preparation of the bachelor 210200.62 - "Design and technology of electronic means", studying the discipline "Fundamentals of design of electronic means".
Reviewers: V.I.Sokolov, Dr. Sci. sciences, prof., scientific. lab consultant. Institute of Physics and Technology of the Russian Academy of Sciences; A. E. Kalmykov, Ph.D. Phys.-Math. Sciences, art. scientific collaborator Physical-Technical Institute of the Russian Academy of Sciences.
Ó Northwestern State Correspondence Technical University, 2009
Ó Vinnikov V.V., 2009
FOREWORD
This textbook is intended for students of the specialty 210201.65 - "Design and technology of radio electronic means" and the direction of preparation of the bachelor 210200.62 - "Design and technology of electronic means". It should help them in studying the discipline "Fundamentals of designing electronic means" of the cycle of general professional disciplines (federal component). In addition, students of the specialty 210302.65 - "Radio Engineering" and 230101.65 - "Computers, Complexes, Systems and Networks" can use the manual when studying the disciplines "Fundamentals of design and production technology of electronic electronic devices" and "Design and technological support for the production of computers", respectively.
The purpose of the manual is to provide students with material on the following sections of the work program of the discipline: design engineering (designing elements of supporting structures of ES; information technologies for designing ES); protection of ES structures; ES design taking into account the requirements of ergonomics and design. The discipline "Fundamentals of designing electronic means" is a logical continuation of the discipline "Fundamentals of designing and reliability of ES" and is associated with the disciplines "Fundamentals of designing RES" and "Modern methods of designing and technologies of RES".
INTRODUCTION
The discipline "Fundamentals of designing electronic means" is a logical continuation of the discipline "Fundamentals of designing and reliability of ES", and, therefore, all the studied material of this discipline should be used to study it and deepen knowledge on the design of ES (RES). On the other hand, the discipline under study is the basis for a deeper study of a number of design methods, and above all, verification methods for calculating the REM structures for the admissibility of thermal, electromagnetic, mechanical and other modes of their operation, which will be studied in the fifth and sixth years in the discipline "Fundamentals of design RES". In this regard, the consideration of these methods in the discipline under study is not carried out, and the main attention is paid to the design design of functional units and modules that are printed.
This manual (Book 2) is a logical continuation of the training manual "Fundamentals of Electronic Design", Book 1. Therefore, when studying the discipline, you should start with it.
This manual contains a subject index, a bibliographic list of used literature, as well as questions for self-control.
1. Construction of es modules
1.1. Design of sealed cells and blocks
The general principles for the layout of structural elements in pressurized units are similar to non-pressurized structures. A significant difference is the provision of the necessary tightness, as well as the specifics in heat removal to create normal thermal conditions in the block. The method of conductive heat sinks has found wide application for cooling hermetic blocks, which provides the most rational heat removal from the applied packageless integrated circuits (ICs), integrated circuits (ICs) and microassemblies (MSBs).
All open-frame ICs and MSBs in sealed blocks are installed on individual or group heat-removing tires, the latter, in turn, are in contact with the block case, which allows heat to be transferred from the elements to the case. Removal of heat from the block body occurs by natural convection, for which the block surface is increased due to its finning or forced air blowing over the block body. To increase the dissipated power of the block, air ducts are introduced inside the block that do not violate the tightness of the block body. To equalize the thermal fields of the elements inside the block housing, a fan is installed in the block, which performs internal mixing of the gas filling the block. Individual and group thermal buses provide smoothing of the thermal field on the substrates of unpackaged ICs and MSBs. Considering the foregoing and the fact that the use of unpackaged NS and MSB increases the packing density of elements and, accordingly, the dissipation power in the block, the specific designs of hermetic blocks and their cells differ significantly from the designs of non-hermetic blocks, although general principle the layout and design options of blocks (detachable and book) is saved.
The calculation of the number of unpackaged ICs and SMEs on the circuit board of the cell is carried out according to the method for determining the number of case elements. The installation of a frameless SME is shown in fig. one . It is recommended to select the installation steps for frameless SMEs according to Table. one.
Installation steps for unpackaged MSBs depending on the average number of terminals involved, in which it is possible to use double-sided printed circuit boards with one-sided installation of unpackaged MSBs and multilayer printed circuit boards (MPB) with two-sided installation of unpackaged microassemblies with a number of layers of at least four (for the manual design method) , are given in table. 2. The recommended steps are given for the case when the output contacts of bare MSBs are located on both sides of the MSB substrate.
Rice. 1. Installation of a frameless SME on a metal base: 1 and 2 - boards; 3 - metal base 4 - conductor; 5 - contact pad
On fig. 2 shows markup seats for open-frame SMEs. By analogy with cells made using case elements, we introduce the concept of the size of edge fields on a printed circuit board. Under the margin margins X 1,X 2,at 1 and at 2;, refers to the distances from the edge of the printed circuit board along the axes X and Y up to the first row of pads for external leads of unpackaged MSBs. edge field at 2 for all standard sizes of film boards (substrates) of unpackaged MSB is 12.5 mm when using control blocks with soldering pins in metallized holes or using printed contact pads and 10 mm when using single caps and contacts as control elements.
Table 3 . In the case of mechanized assembly of cells on printed circuit boards, edge fields with a width of at least 5 mm are provided. On fig. 3 ... 6 shows typical cell designs of sealed blocks of detachable and book designs.
Table 1
Steps for installing open-frame micro assemblies on cell circuit boards
|
Installation step of frameless microassembly along axes, mm |
Dimensions of the film board of unpackaged MSB, mm |
|||||||||
Note: 1- plus sign (+) corresponds to the recommended installation steps;
table 2
Installation steps for unframed SMBs (BSMBs) depending on the average number of outlets involved
|
film |
Average number of people involved leads in one BSMB, mm no more |
BSMB installation step along the axes, mm |
|
Rice. 2. Marking of seats for open-frame SMEs
Table 3
edge fieldsX 1, X 2 on PP when installing BSMB
Rice. 3. Cell of the hermetic block of a detachable design: 1 - printed board; 2 - unpackaged microassembly; 3 - metal tire; 4 - electrical connector contact
Rice. 4. Cell sealed block book design: 1 - metal base 2 - unpackaged microassembly; 3 - air duct: 4 - electrical contact; 5 - printed circuit board
R 
is. 5. Cell of hermetic block of book design with frame: 1
- printed circuit board; 2
- metal tire; 3
- body microassembly; 4
- printed contact
Rice. 6. Cell sealed block book design:
1 - printed circuit board; 2 - metal tire; 3 – microassembly
The cell shown in fig. 3 consists of metal bars to which a printed circuit board is attached with hollow rivets. Open frame MSBs are directly mounted on metal rails on both sides of the printed circuit board. A clamping bar is attached to the end of one of the sides of the printed circuit board through metal tires, which has tides for fixing the cell in the block using captive screws. On the opposite side, contacts are installed by means of flaring and soldering into the holes of the printed circuit board, intended for the electrical connection of the cell with the unit's backplane printed circuit board.
To remove heat from the cell, the clamping bar has good thermal contact with the metal busbars of the cell. The cell shown in fig. 4 consists of a U-shaped metal base to which a rectangular air duct is attached by welding. The air duct has lugs for fastening and hinged connection of cells in the block. The printed circuit board of the cell is attached to the base with hollow rivets. Frameless SMEs are directly installed on the base from two sides. The electrical connection of the cell with the backing printed circuit board of the unit is made using a flexible printed cable. To remove heat from the cell, the base has good thermal contact along the entire length with the air duct.
The cell shown in fig. 5, consists of a cast frame, to which a printed circuit board with metal busbars mounted on it on both sides is attached with hollow rivets.
Unpackaged microassemblies are placed directly on metal tires. The frame is provided with lugs for hinged connection of the cells in the block. To fix the cell in the block, adapter sleeves are made through which the fixing screws pass. The electrical connection to the unit's backplane is made using a flexible printed cable. To remove heat from the cell, the frame has good thermal contact with the busbars of the cell.
The cell shown in fig. 6 consists of a printed circuit board with frameless MSBs installed on its two sides on individual metal busbars. The cells have hinges for hinged connection of the cells in the block. Holes are provided on the printed circuit board for fixing the cell in the block with screws. The electrical connection of the cell is made using bulk wires, which are stitched through two rows of non-metallized holes located on the printed circuit board to protect against breaking.
On fig. Figure 7 shows the design of a sealed cell with switching elements and unpackaged MSBs. The design consists of a rectangular case, on the bottom of which a film is glued or a switching board is installed. Two flexible cables made of foil-coated polyimide are pressed into the holes on the rear side of the case with plastic, on which connecting conductors and contact pads are formed by chemical etching. The terminals of the electrical connector SNP34 are fixed in the contact pads. The flexible cable is placed between two plastic spacers, put on the terminals of the electrical connector. From above, the body is closed with a lid, which is sealed with the cell body by soldering. On the sides of the body there are lugs used to install the cell in standard BNK2 guides; cells are fixed with screws. On the underside of the cell body there is a recess for installing pin radiators made of titanium tape.
R 
is. 7. Sealed cell with unpackaged SMEs
On fig. Figures 8 and 9 show typical designs of sealed units with unpackaged microassemblies. The block of hermetic detachable design (Fig. 9) consists of a set of cells on unpackaged SMEs (see Fig. 3) installed parallel to the front panel. The body of the block is cast, made of Al9 aluminum alloy. The block is sealed with the help of rubber gaskets installed in the grooves of the block body, and the side covers of the block are bolted. The case and lateral removable covers of the block are ribbed. To fix the cells in the block, group guides and lugs with threaded bushings are provided on the upper and lower walls of the housing. On the front panel there is a connector, sealed through a sealing gasket, and a tube for evacuating air and filling with dry nitrogen. Catching pins are located on the rear panel of the block housing. Intra-unit electrical connection between the cells is carried out with the help of captive jumpers installed on the pins of the interconnecting printed circuit board.
A corrugated aluminum spacer is used to improve thermal contact between the cell clamps and the ribbed side cover of the block.
Rice. 8. Block sealed split design: 1 - cell; 2 - front panel; 3 - wall; 4 - back panel; 5 - side cover
Rice. 9. Hermetic block of book design with air duct: 1 - cell; 2 - front panel; 3 - casing; 4 - fee; 5 - flexible printed cable; 6 - air duct
A block of hermetic book design with a vertical axis of cell opening, shown in fig. 9, consists of a set of cells on unpackaged SMEs (see Fig. 4), which are installed perpendicular to the front panel of the unit. Front and rear panels are injection molded from aluminum alloy Al9 and coated. The casing of the block is welded, made of titanium alloy with a coating, followed by hot tinning with POS-61 solder. The side walls of the casing have stiffening ribs.
The unit is sealed by soldering the casing to the front and rear panels of the unit. On the front panel of the unit there is a connector sealed through a sealing gasket, a tube for evacuating air and filling the unit with dry nitrogen, as well as openings for supplying and discharging air to the air duct collector. On the front panel of the block there are safety pins.
Intrablock electrical connections are made using flexible printed cables and a backplane printed circuit board. The heat is removed from the unit with the help of forced air supplied through hermetic air ducts.
Rice. 10. Hermetically sealed book design with fan: 1 - fan; 2 - front panel; 3 - cell; 4 - connection board; 5 - flexible printed cable; 6 - back panel; 7 - wall
The block of hermetic book design with a vertical axis of cell opening (Fig. 10) consists of a set of cells on unpackaged SMEs (see Fig. 5), which are installed perpendicular to the front panel of the block. The body of the block is welded. The body parts of the unit are made of AMg material, the front and rear panels of the unit are die-cast from Al9 aluminum alloy.
All body parts and panels are coated. The unit is sealed by soldering the case and the front panel of the unit.
Hermetic block of book design with a horizontal axis of cell opening, shown in fig. 11, consists of two cells (see Fig. 6) on frameless SMEs installed perpendicular to the block panel. The frame of the block is made by pressure casting of Al9 aluminum alloy. The panel and casing of the unit are made of titanium alloy and hot tinned with solder plating. The block is sealed by soldering the casing to the panel. In the case for fixing the frame with cells there are stops, and for fixing the cells in the panel and frame - tides. The panel is equipped with electrical connectors obtained using multi-pin eye connections, a tube for evacuating air and filling with dry nitrogen, and threaded safety pins. Intrablock electrical connections are made using bulk wires.
The set of considered NDT blocks allows solving design problems for a wide range of hardware developments. In this case, it should be borne in mind that blocks with a general sealing are characterized by a high packing density of elements.
Rice. 11. Block sealed book design: 1 - cell; 2 - frame; 3 - panel; 4 - bulk wire; 5 - casing
Block sealing containing unpackaged ICs and MSBs is carried out in order to prevent the impact of external climatic factors on the unpackaged elements that are part of the ICs and MSBs, i.e. they are sealed to establish the permissible relative humidity and composition of the gas filler inside the unit case, which is determined by the technical conditions for the incoming frameless elements are included in the block.
To create the most favorable microclimate inside the block body, the internal volume of the block is filled with an inert medium in the form of various gases or mixtures of gases through the exhaust tube. In order to increase the service life or storage of hermetic blocks before preventive maintenance, the internal volume of the block is filled with an inert medium with an overpressure of not more than 12 10 4 Pa through exhaust pipes (Fig. 12, hell).
Rice. 12. Designs of exhaust tubes: 1 - frame; 2 - a tube; 3 - sleeve; 4 - compound; 5 - cup; 6 - rubber compressor; 7 -ball; 8 - pin
To create an inert environment, dry nitrogen is used, which, in terms of its thermal characteristics, is equated to air. Work is also underway to use as an inert medium various non-toxic liquid solutions with a thermal conductivity an order of magnitude higher than that of dry nitrogen. However, the influence of these liquids on the electrical parameters of bare elements and, accordingly, on their reliability is not always fully understood.
The tightness of the blocks is ensured by the sealing of their cases and external electrical connectors, which are installed on the front or rear panels of the case. Taking into account the specifics of the sealing of block cases and electrical connectors, these issues must be considered separately.
Sealing of block cases can be carried out in the following ways: by welding the base and block body; soldered dismantled connection of the body (base) with the cover (casing) of the block; sealing gasket. The choice of sealing method is determined by the requirements for the blocks, depending on the operating conditions, the size (volume) of the block, as well as the materials used in the body and base of the block.
Sealing by welding. The opening of such blocks is possible only with the help of mechanical removal of the weld, which entails the obligatory ingress of metal dust on unpackaged elements and, accordingly, their failure.
Sealing with a soldered, dismantled joint. The following requirements are imposed on the elements of the soldered joint of the unit structure: to eliminate overheating of the unit at the time of soldering, a thermal groove must be provided in the structural elements of the cover body (near the solder joint); the gasket should be made of rectangular section made of heat-resistant rubber; the diameter of the wire must be less than the width of the gap between the cover and the body by 0.1 ... 0.2 mm.
In a solder joint, the wire over the gasket is laid around the entire perimeter of the joint. One of the ends of the wire is led out of the connection zone through a groove in the cover and usually fits into the thermal groove. The distance around the entire perimeter of the connection is filled with low-melting solder. This soldered connection allows you to dismantle (open the case) of the block up to three times.
In order to prevent leakage of the unit, the outer surface of the solder joint should not be the mounting surface of the unit, and all fastening elements of the units should be located at the maximum possible distance from the solder joint.
Sealing with gaskets. Structural elements of sealing block housings with gaskets are shown in fig. 13.
The sealing and design of special electrical connectors, the tightness of which is carried out using glass-to-metal joints, have a number of specific aspects, so this issue should be considered in more detail. All glass-to-metal joints that are used in the design of microcircuits, microassemblies and hermetic blocks of microelectronic equipment can be divided into the following types: eye, disk, window and flat.
Eye connections are used in the manufacture of relay bases, bases of IC and MSB cases, pressure seals, metal legs of electrovacuum devices, plugs of electrical plug connectors and similar products.
Disk connections are used in the manufacture of multi-contact current bushings, plugs of electrical connectors, assemblies of electrovacuum devices, bases of cases.
Window connections are used in the manufacture of resonator windows, high-frequency filters and viewing windows of devices necessary for visual control.
Flat connections are used in the manufacture of bases for metal-glass cases of ICs and MSBs with a rectangular cross section of the leads.
Rice. 13. Sealing the body of the blocks with a sealing gasket: 1 - block base; 2 - sealing gasket; 3 - block body; 4 - bolt; 5 - screw
Glass-to-metal joints, depending on the materials used, are divided into matched and non-matched (compressed) junctions. Matched junctions are understood as connections in which the coefficients of thermal expansion (TEC) of the materials being soldered (glass-metal of the holder) are equal or differ little from each other. In turn, mismatched junctions are understood as compounds in which the CTE of the materials being soldered (glass - metal of the casing) differ sharply from each other in the temperature range from room temperature to the glass softening temperature. Therefore, when designing individual units of microelectronic equipment, it is necessary to pay great attention to the choice of materials and, accordingly, their mutual combination.
Eye connections should be understood as connections in which one or more leads are soldered (melted) into a metal cage through an insulator individual for each lead. Such designs of eye connectors are shown in Fig. 14 and 15.
Disk connections are made in the form of matched and unmatched junctions (Fig. 16 and 17). In the disk connection (Fig. 16), the glass insulator is placed symmetrically in height 
.
Minimum distance between terminals 
and between outlet and wall 
clips must be at least 0.8 of the output diameter.
Rice. 14. Eye single-pin connections:
a- design with flanging (or hood) eye in sheet metal; b and in- constructions with punching (or drilling) of an eye in thick-walled metal; 1 - metal clip; 2 - output (rod or tube); 3 - glass insulator
Rice. 15. Eye multi-terminal connections: a- design with beaded peephole in sheet metal: b- construction with punching or drilling in thick-walled metal; 1 - metal clip; 2 - output (rod or tube); 3 - glass insulator
Window connections can be made by direct soldering glass to metal or using fusible enamel.
Flat joints are understood to mean joints in which metal parts are soldered to glass on a flat surface.
Rice. 16. Disk connections. Rice. 17. Disk connections.
Consistent junction: 1 - Unmatched junction: 1 –
metal clip; 2 - conclusion; 2 - metal clip;
conclusion; 3 - glass insulator 3 - glass insulator
In the production of radio-electronic equipment based on microelectronics, specific requirements are imposed on the connection of microelements inside microcircuits, as well as on the installation of microcircuits in nodes and blocks.
Mounting, soldering and welding methods used in the production of microcircuits differ from the methods used in the production of functional units and micromodules. This is due to the fact that most semiconductor materials and dielectric substrates made of ceramics and glass have low thermal conductivity, a narrow plasticity zone, and low resistance to thermal and mechanical stresses.
Semiconductor integrated circuits, unlike thin-film ones, have an order of magnitude higher resolution of the pattern, which makes it possible to increase the density of microelement placement (i.e., increase the degree of integration). Compared with thick-film integrated circuits, the degree of integration is more than a hundred times higher.
The internal mounting of any microcircuits includes technological operations for installing and fixing one or more microcircuits in the package and making intra-circuit connections. For the assembly and installation of microcircuits, various installations are used. So, for the assembly of crystals of semiconductor integrated circuits ranging in size from 0.6 x 0.6 to 1.8 x 1.8 mm, the EM-438A installation is used, and for mounting several crystals in one housing, the EM-445 installation is used. The fastening of the chip chip is carried out by soldering or gluing.
Intra-microcircuit connections between the contact pads of the microcircuit deposited on the crystals and the terminals of its case are made using wire jumpers, which are copper, aluminum and gold microwires with a thickness of 8 to 60 microns.
Depending on the combination of materials used and the design of the leads, when assembling microcircuits, microwelding (thermocompression, ultrasonic, contact, electron beam, laser) or microsoldering is used for the connection.
The most widely used are thermocompression and ultrasonic microwelding and microsoldering.
Thermocompression microwelding It consists in the simultaneous effect on the welded metals of pressure and elevated temperature. The metals to be joined are heated to a certain temperature (the beginning of recrystallization), at which the adhesion (diffusion) of the metal surfaces cleaned from oxides begins when even a small load is applied. This method allows you to connect electrical leads with a thickness of not more than a few tens of microns to the contact pads of crystals, the dimensions of which do not exceed 20...50 microns. In the connection process, an aluminum or gold microwire is applied to a semiconductor crystal and pressed with a heated rod.
The main parameters that determine the mode of thermocompression microwelding are specific pressure, heating temperature and welding time.
In thermocompression microwelding, careful control of these parameters is necessary.
The scope of thermocompression microwelding is very wide. It is the main method of connecting leads to semiconductor crystals; it is also used for connecting wire microconductors to sputtered pads of microcircuits, for mounting LSIs and microassemblies. With the help of thermocompression micro-welding, group welding of microcircuits with planar leads is carried out, as well as precision micro-welding of elements with a minimum conductor thickness (up to 5 microns).
Ultrasonic microwelding allows to obtain a reliable connection of metals with oxide surfaces of crystals with a minimum thermal effect on the structure of heat-sensitive elements of microcircuits. This type of microwelding is used to join metals with different electrical and thermal conductivity, as well as to join metals with ceramics and glass.
The domestic industry produces ultrasonic installations for attaching a microwire or microtape (up to 60 microns in diameter) made of aluminum and gold to semiconductor microcircuit crystals, for in-case mounting of microcircuits, as well as for assembling LSI and microassemblies.
Equipment for the assembly of semiconductor devices and microcircuits by ultrasonic microwelding consists of an ultrasonic welding unit, the principle of which is based on the excitation of mechanical vibrations of ultrasonic frequency by a transducer in the place of the parts to be welded, and a device for fixing the microcircuit.
as converters electrical energy in mechanical vibrations, magnetostrictive and piezoelectric devices are used.
In ultrasonic welding, a permanent connection of metals is formed as a result of the combined effect of mechanical vibrations with a frequency of 15 ... 60 kHz on the parts, relatively small compressive forces and the thermal effect that accompanies welding. As a result, a slight plastic deformation appears in the welded zone, which ensures a reliable connection of the parts.
In recent years, a combined method based on thermal compression with indirect pulsed heating and the superposition of ultrasonic vibrations has been widely used for mounting microcircuits.
micro soldering can be carried out with soft and hard solders. The main advantages of microsoldering are its relative simplicity and the ability to connect parts of complex configuration, which is difficult to perform with microwelding.
To soft solders include alloys of tin and lead, indium and gallium, tin and bismuth, which have a low melting point (usually 140 ... 210 ° C). These solders are most commonly used for soldering in integrated circuits.
When microsoldering microcircuits with soft solders, the metals to be joined must be metallurgical and chemically compatible, must not form alloys with high resistance and intermetallic brittle joints at the contact point; Solder must be inert at the operating temperature of the circuit and completely removed from the joint and from the surrounding surface.
To hard (high temperature) solders include alloys based on silver PSr45 and PSr50, having a melting point of up to 450 ... 600 ° C. These solders are used to seal microcircuit packages, to connect silver or silver-plated parts (since tin-lead solders dissolve a significant amount of silver, changing the characteristics of the contact), etc.
Currently, high-tech methods of microsoldering have been developed. One of these methods is microsoldering in an atmosphere of hot (up to 400 °C) inert gas or hydrogen, in which the pre-tinned area is blown from miniature nozzles with a hot gas jet. This method provides high productivity, in addition, eliminates the use of flux.
The soldering process is simplified by using dosed solder in the form of tablets or paste, which is pre-applied to the joints. This method provides accurate control of the amount of heat at the welding site, and when using automation tools, it allows you to adjust the time of current flow and its magnitude.
Mechanized microsoldering is characterized by stepping movements of the soldering tool, usually carried out according to the program, and pressing the solder joint by the tool during soldering. Automation of soldering processes when connecting integrated circuits to a circuit board, along with an increase in labor productivity, provides an increase in the quality of connections.
It might be useful to read:
- Resume - a step towards obtaining the position of a tourism manager Resume of an assistant tourism manager sample;
- Some standards for project activities;
- Some standards for project activities;
- Filled sample resume for system administrator, IT specialist (example) Resume for the position of system administrator example;
- Sample Veterinarian Resume General Requirements for a Veterinarian;
- Key Responsibilities of a Bartender;
- Job Responsibilities of a Bartender;
- Sample resume of a PC operator Achievements in a resume of a PC operator;