Fabrication and installation of wire harnesses. Cable harness products. Production of connecting harnesses and cables
Making and laying harnesses
The bundle is a collection of stripped wires and cables fastened together in some way and, if necessary, equipped with elements electrical installation(tips, connectors, etc.).
According to their purpose, harnesses are divided into intrablock and interblock.
Intra-block harnesses are used for electrical connection of individual nodes, blocks and electrical parts inside the device, and inter-unit harnesses - for the electrical connection of various radio equipment and devices into a single system. Depending on the location of the nodes in the body, the bundles can be flat or voluminous.
To protect against exposure environment, mechanical damage or for the purpose of shielding, the bundles are wrapped on the outside with a keeper, nylon, lavsan or polyvinyl chloride tape, varnished or enclosed in a shielding braid.
1) different colors of wire insulation;
2) coloring or numbering of PVC tubes used to fix the ends of the insulation (the tubes are numberedon the machine, in special stamps or inscribed by hand with marking ink);
3) plastic tags with a symbol for the connection point, put on the wires.
Harnesses in which failed wires cannot be replaced are provided with spare wires. Their number is taken at the rate of 8 ... 10% of the total number in the bundle, but not less than two wires. The length and section of the spare wires must be equal to the largest length and section of the wires present in the bundle. The length of the harness leads must be sufficient for connection to the nodes and elements of the device circuit without tension; in addition, there must be a margin of 10 ... 12 mm for re-stripping and attaching each end of the wire.
A typical technological process for manufacturing a tow includes the following operations:
cutting wires and insulating tubes;
laying wires on the template and knitting them into a bundle;
termination of the ends of the wires of the bundle with their simultaneous marking;
harness control (continuity); protection of the harness with insulating tape;
output control (visual inspection for compliance with the standard, well, and continuity).
The length of the prepared wires must correspond to the dimensions specified in technological map or a table of wire blanks. Wires and shielding braids are cut on automatic machines, as well as using assembly or guillotine scissors and wire cutters.
It is more expedient to make a blank of wires of the same length and knit them into a bundle without branches on a special device (Fig. 1.25), which consists of two racks mounted on a board (the distance between the racks depends on the length of the prepared wires).
FROM outside parties the racks have grooves. First, the wire is wrapped around the posts, while the number of turns of wire should be half the number of wires in the bundle. Then the coils of wire located between the uprights are tied into a bundle with thread or twine. After tying, the turns of wire are cut in places located opposite the grooves in the racks.
With the manual method of harvesting wires for bundles, their length is determined using samples or a ruler. In serial production, special machines are used for measuring wire cutting to a predetermined length.
The wires are laid on the template in a certain order (according to the scheme printed on the surface of the template), after which they are tied with a thread or twine into a bundle. Template markup forthe wiring harness is laid according to the wiring diagram, the layout of the node or device in which the harness will be installed, and the mounting table of connections. On the marked template, the wires are first laid out and then knitted into a bundle (Fig. 1.26). Depending on the design of the device, the bundles are flat or voluminous.
When laying out, the ends of the wires are cut along the transverse "marks, marked and fixed. The laying of wires on the template starts with spare and long working wires and ends with the shortest wires. Shielded wires included in the bundle are wrapped with keeper tape and placed inside harness or in an insulating tube.
The harness should be knitted in one direction with cotton thread No. 00 or linen No. 9.5/5. For hand knitting, the device shown in Fig. 1.27 a. A spool 3 with threads is inserted into the body 4 of the device. Covers 5 and 2 serve to center the coil. In the top cover 5 there is an eye for giving the thread a certain direction, and a hook 1 is attached to the bottom cover.
To facilitate the winding of the thread from the spool, a slot and an outlet for the outer end of the wound spool are made in the body. First, a wound coil is inserted into the body of the device, the upper end of which is inserted into the slot of the body. Next, the lid is closed and the end of the thread is threaded through the eyelet.
The harness is knitted in accordance with the loop formation scheme. It takes 0.5 ... 1 s to knit one knot. To perform the operation, it is necessary to take the thread (see Fig. 1.27, b), hook the loop, stretch it under the tourniquet and thread the device through two loops, tightening the thread. At the moment of tightening the knot, the thread passing through the body must be pressed with a finger to its surface. The device helps to improve the quality of knitting harnesses and reduce the complexity of their knitting by 15...20 times. Recommended knitting methods are shown in fig. 1.28.
Loops are recommended to be knitted with tension at regular intervals (no more than 50 mm), as well as in places where wires branch off.
The knitting step of the loops is set by the designer, depending on the diameter of the bundle.
After knitting the wires into a bundle, their ends are terminated. First, all ends of the wires are marked according to the wiring diagram, and then the correct layout of the wires is checked with a dial tone. In the case of using electrified templates for making harnesses, continuity can be omitted.
The control of complex harnesses is carried out on special semi-automatic stands according to a given program. The harness on the panel of the stand is fixed manually, and the correct layout of the wires and the resistance of their insulation are controlled automatically.
First, control is carried out for compliance with the electrical wiring diagrams, that is, checking the correct layout of the wires. For this purpose, the required voltage is sequentially applied to one of the ends of the tested wire. At correct layout wires, the voltage must be recorded in all wires of the bundle electrically connected to the wire under test. Next, you need to make sure that there is no voltage in the wires of the bundle, which are not electrically connected to the wire under test. All information about the control is issued automatically in the form of coded holes on a punched tape or as a record on a tape with digital and alphabetic designations.
When monitoring the insulation resistance of wires, a consistent supply of constant voltage is automatically carried out to electrically isolated wires (circuits), while fixing the insulation resistance.
If necessary, the harness is protected with insulating tapes or a shielding braid. Finished bundles are laid according to the wiring diagram and the drawing of the device. Simultaneously with laying, the ends of the wires of the bundle are bred to the corresponding places in the device circuit and soldered. At the same time, it is necessary to ensure that individual wires do not obscure the markings and inscriptions of the nominal values on the parts.
Attention! When laying the harnesses in the device, care must be taken to avoid breakage and breakage of the conductive cores of the wires and conclusions of the hinged radio components, as well as short circuiting of bare conductive places.
Inside the device, the harness is attached to the chassis or walls with metal brackets (Fig. 1.29), under which you must firstput insulating materials made of polyvinyl chloride, varnished cloth or pressboard. The edges of the gaskets should protrude from under the bracket by at least 5 mm. The brackets are made double-sided (attached with two screws) and one-sided (attached with one screw). The design of mounting brackets, especially single-sided ones, must be sufficiently rigid to prevent them from bending or deforming when attached to the chassis together with the harness.
To ensure the transition of unshielded (and, if necessary, shielded) harnesses from one unit of the device to another through the wall of the chassis or screen, insulating bushings are provided in this place.
Knitting harnesses
The basis of every electrical product is conductors. In this age of miniaturization, many of them are integrated into printed circuit boards, walls and panels, can be made in the form of ultra-thin plumes, transparent coatings and much more. However, the lion's share of the circuits is still connected by separate isolated copper wires and cables, which, for ease of installation and repair, more stringent standardization of parameters and easier access to various blocks combined into bundles.
Knitting harnesses is one of the most common operations in the general cable processing process, the manufacture of cable assemblies. In principle, it is produced after cutting and stripping the cables. But often (especially when many wires of the same type are used in the bundle that do not require complex stripping), cutting can be done directly on the knitting template after laying the wire along the route. That is, depending on the materials used, production conditions and the characteristics of a particular product, operations can be mixed and interchanged. This requires their implementation in the course of a single technological process, in any case, at one enterprise. LLC "CEPIKS" is one of the leaders of the Russian market in this specialization.
Knitting is a general term. In fact (in accordance with the specifications for specific bundles), wires can be fastened not only with a thread, but also with all kinds of clamps, ties and tapes, leather cases, special polymer bandages and so on. The material and method of knitting is determined by the type of wires, the conditions of installation, storage and operation of the equipment, the location of the bundle route in the product in relation to sharp, moving, heating elements. In some cases, knitting with a thread is even unacceptable: in flexible areas where the wires must move freely relative to each other, inside insulating tubes (sheathing, windings), on wires and cables with insulation made of polyethylene, fluoroplastic and other materials with cold fluidity.
When knitting bundles, special attention is paid to shielded wires, the braids of which must be isolated from each other and from the device case, if this is not allowed. electric circuit. They are also enclosed in solid smooth dielectric tubes in areas where the bundle can be bent during operation. Additional insulation is also applied to the bundles at the points of their transition through sharp edges and holes in the structural elements of panels and devices. A reinforced bandage made of thread (or an additional tie) fastens the places where the wires branch from the trunk of the bundle, the edges of the flexible sections and some other key points.
Harnesses are knitted, as a rule, on templates specially made according to technical documentation - shields with pegs for turns and wire branches, providing the necessary bending radii and matching the shape of the harness to its route according to the project. The methods of knitting and layout of wires in bundles, depending on their cross section, type and functional purpose, are standardized by GOST 23586-96, the design of wire cutting and core fastening - by GOST 23587-96, and the requirements for cutting and connecting screens - by GOST 23585-96. Immediately, stripping, dialing and marking of cables is usually performed (since the wire numbers are signed directly on the shields), and their tinning or installation of lugs after removal from the template.
final stage harness manufacturing is its testing on special equipment with a thorough check and recording of all electrical and mechanical parameters.
Manufacture of cable harness products
Cable harness products are used for switching nodes, boards, blocks and switching racks in many industries. They can differ both in the degree of complexity (from a single-core conductor between two contact pads, to a combined bundle with a complex switching table), and functional purpose(ground wire, coaxial cable, fiber optic cable, etc.)
Regardless of the complexity and purpose, the cable assembly must meet the following quality criteria: reliability of signal transmission from the start to the end point; minimum loss of signal characteristics; ease of switching the harness in electrical equipment; durability of terminal connectors, contacts and connectors during the operation of electrical equipment; maintainability during service.
The manufacturing process of cable harness products (cable assemblies) is divided into several production stages:
Measured wire cutting
wire stripping
Crimping cable lugs (cremping)
Installation (assembly) of connectors
Knitting (installation) of harnesses
Wire (cable) marking
Preparation and installation of a special cable
Quality control and compliance with the terms of reference
Even at the design stage, factors affecting the characteristics of the harness are determined. They form the basis of the technological process for the manufacture of cable assemblies. Overall dimensions, type of wire (cable), cross-section, external diameter, installed contacts and connectors, marking, bandage and strapping - all these stages are strictly verified in the production process chain.
The production of cable harness products is carried out on assembly stands (with the exception of jumper wires). They allow you to minimize errors when knitting and bandaging harnesses, as well as reduce production time. Also on the stands there is an opportunity to check specifications harness knitting.
Checking the quality and compliance of the cable assembly with the terms of reference is checked at all stages of the production of the wire harness and at the final control (output control of the enterprise). All discrepancies are recorded in the test reports, on the basis of which a statistical analysis is carried out. Necessary adjustments are made to the manufacturing process, materials, terms of delivery of components, design and technological documentation.
TECHNOLOGIES FOR THE PRODUCTION OF ELECTRICAL HARNESSES Cars are currently subject to high requirements for build quality and reliability. Accordingly, each unit and part of the car must meet these requirements. An integral element of the car is the electrical wiring (wiring harnesses). A wiring harness is a finished product consisting of individual wires fastened together in a bundle, the ends of which are reinforced with contacts that are assembled into blocks or protective elements (tubes, rubber caps, covers) are put on them. The wires are fastened into bundles: bandages made of PVC adhesive tape, cable ties (toothed clamps made of thermoplastic polymers); heat shrink tube.  A modern car has harnesses with a total number of wire segments of about three hundred (and more often more), reinforced with various contacts. The reliability of such a complex product depends on several factors. First of all, these are increased requirements for the quality of components and materials. Which, in turn, is influenced by the choice of supplier and the conduct of incoming control. The next factor is the use of modern high-performance and precise production and control - measuring equipment that meets the requirements of international standards. And, finally, the most important factor of reliability is the specialists involved in the production process. The quality and reliability of the product depends on their professionalism. Autotractor harnesses can be divided into: low and high voltage(battery and starter wires are most often single, less often - consisting of two to three wires).  The technological process of manufacturing a wire harness is divided into several basic operations: cutting wires, stripping the ends of wires from insulation, reinforcing wires with lugs or contacts, fastening wires into bundles (binding), installing detachable connectors, quality control. In order for you to better understand what components the wire harnesses consist of and in what sequence they are used in their manufacture, we tried to give a detailed description of the main operations for the manufacture of harnesses and the types of equipment used. For a better understanding of the assembly sequence of any harness, in this section we will introduce the general concepts of the structure of the harness, which will be encountered later in the text. The harness can be divided into parts and give them names.
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Modern harness production |
Deprecated Solutions |
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harness production XXI century requires new technological approaches in the production of wire harnesses. TERMOPRO offers new assembly tables for laying out and knitting bundles of the MONOLITH series, which are designed to replace obsolete plywood plazas at domestic enterprises. |
Existing solutions are plywood sheets with a structural diagram of the bundle printed on paper and pins firmly installed at the nodal points of the bundles. This design is non-separable and is intended for assembling only one type of bundle. Design homemade device takes a lot of time, both from technologists and skilled workers involved in its manufacture. |
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New solution for harness production
New tables for harnesses of the MONOLITH series are made of Russian aluminum profile. The increased rigidity of the frame is provided by cast, angular amplifiers. The solid construction of the tables for the production of bundles is complemented by elements for quick replacement of the assembly plates.
4.1. Complete electrical devices with mounted internal secondary circuits must be manufactured at factories or (as an exception) at the MEZ.
4.2. The basis for the development of technical documentation is the task issued by the customer for the manufacture of electrical equipment.
4.3. Based on the task, design documentation for the product is developed (electrical schematic diagrams, connections and connections, documentation for the manufacture of metal cases and other metal structures).
4.4. Based on the drawings, a list of consumption rates of materials and components for the device is compiled. Technological documentation is developed for serial production.
4.5. After picking, the task is transferred to the production unit for work to be performed.
4.6. When performing secondary circuits on the same type of devices, there is no need to lay wires in each case in place. It is more productive to conduct preliminary preparation of wire harnesses on special tables-stands using templates. To work on these tables, you must first draw up a sketch of the wiring harness.
4.7. The sketch is made on the basis of the connection diagram, the layout of the laying route, as well as the laying places on the switched device. The wiring harness can be sketched in single line (see figure 4.1, a) and isometric (see Fig. 4.1, b) images.
On sketches, wire harnesses with all branches and bends should be drawn with one line.
On each rectilinear section of the bundle (from corner to corner or branch), the dimensions determined when measuring the route for laying the wiring harness are applied (see Fig. 4.1, a). On the sketches, straight sections and bending angles of the wire harness to the edge are depicted as lines, and the bending angles of the bundle to the plane are shown as a cross or other mark. On all sections of the flow in circles indicate the number of wires.
It is necessary to take measurements in place and apply dimensions on the sketch with an accuracy that excludes marriage during installation and excessive consumption of wires during the preparation of bundles.
According to the sketches, the length of the wires is determined and marked on the connection diagram.
Rice. 4.1. Wire Harness Sketches
4.8. With multi-wire laying, it is necessary to take measurements along the middle wire, i.e. in the center of the harness. Measure the branches from the main bundle to the apparatus, adding the length of the wire required for bending and connecting it to the apparatus. According to the sketch, the length and number of wires for pre-working are calculated. The lengths of the wires calculated according to the sketch are put down on the wiring diagram.
4.9. The wiring harnesses according to the sketches are arranged as follows. According to the marks on the wiring diagram, they take the required number of wires of the appropriate length, which are laid on the table in a stream of the intended shape. Since the assembly of the bundle, as a rule, starts from a series of clamps, the ends of the wires have different lengths depending on the place of their connection. Fasten the tourniquets with temporary bandages. The first bandage is applied at a distance of 50-60 mm from the beginning of the first straight section of the tourniquet. The following bandages are applied at intervals necessary to maintain the shape of the bundle being assembled (every 500-600 mm).
If it is necessary to form a tourniquet with an angle to the edge, then a mark is made on it with chalk according to the size of the straight section on the sketch. Stepping back from this mark to a distance equal to half the width of the bundle, a second mark is made on the inner wire, along which this wire is bent. All the following wires bend along this wire. When branching, the parts of the bundle do the same, only in this case they retreat to a distance equal to half the width of the branch. After the bend is completed, the next straight section is measured according to the sketch, and so on until the end of the bundle.
After complete assembly the tourniquet is bent to a plane. Since the lower row of wires is stretched when the wire harness is bent onto a plane, when assembling the bundle, an allowance is given to the lower row to compensate for this stretch.
Bundling (see fig. 4.2) and bending of wire bundles to the plane (see fig. 4.3) should be carried out using special devices or plates.
Rice. 4.2. Bundling wire flow:
a- compress for packing; b- package of wires; 1 - screw with washer; 2 - pressure plates; 3 - lower clamp bar with screw thread; 4 - gaskets
Rice. 4.3. Bending the flow of wires to a plane
a- using a wooden plate; b- using an aluminum bracket; 1 - wooden plate; 2 - wire flow; 3 - wooden plate; 4 - bandage; 5 - bracket made of sheet aluminum
4.10. If it is necessary to manufacture several identical bundles or jumpers according to the same scheme, it is recommended to use templates made from electric cardboard, plywood or other sheet material and representing a layout of a part or the entire electrical structure to be mounted, universal templates - tables on which plates with rows of holes are installed, where studs are laid according to the markup, as well as three-dimensional templates.
4.11. When preparing and installing a wiring harness on electrical structures using templates made of sheet material, for example, from electrical cardboard, you should:
On a sheet of electrical cardboard 0.5 mm thick, mark the panel diagram with a pencil and a ruler, mark the attachment points with crosses;
Through the marked electrical cardboard attached to the panel, using a center punch, mark on the panel the attachment points for devices, apparatus and wire harnesses;
After marking the panel, remove the template and mark the following electrical structures of the same type in the same way;
Transfer the marked electrical structures for further processing, and according to the template on the table-stand, prepare and route the flows and terminate the wires. In order to prevent the bundle on the template from shifting when laying and terminating the wires, through holes should be made along it on the template in three or four places, with the help of which the wire flow is temporarily attached to the template;
Install devices, devices and relays or their layouts (templates) - cut out from steel sheet base projections. To install mock-ups on the electrical structure in places corresponding to the mounting holes of apparatuses and devices, press in bushings 10 mm high, on which to place the mock-ups of the equipment, fixed to the electrical structure with screws;
Lay the prepared wiring harnesses and fix them on the electrical structures;
Remove mock-ups from electrical structures and install devices and devices instead;
Attach wires to dial-in clamps, devices and devices.
4.12. When preparing wire harnesses using universal templates (see Fig. 4.4), you should:
Screw the studs 2 into the holes of the inclined wooden plate 1, installed on the table, in the direction of the wiring harness 4, and if there are no holes, hammer nails without hats; also install the studs at the locations of the contact springs and the leads of the coils of the devices;
Lay out the wires according to the wiring diagram. To do this, install the turntables with wires near the universal template table; unwinding wire 3 from the turntable, lay it behind the studs in the direction of the wire flow and fasten it with two or three turns on the stud-pin of the apparatus furthest from the terminals; fasten the other end of the wire in the same way on the pin of another device or clamp to which the wire is to be connected, and cut it off. Similarly, lay out the remaining wires of the bundle;
Perform bandaging (knitting) of wires in bundles in straight sections with a step of 150-200 mm, depending on the thickness of the bundle, as well as in all places where the wires exit the bundle;
Remove the ends of the wires from the studs imitating the outputs of the apparatus, straighten and bite off according to the ruler-template to a length that makes it possible to attach the wire to the output of the apparatus. The template ruler should be applied with an edge to the plate, and the plane should be applied to the bitten off ends of the wires;
Remove the prepared bundles from the stove, terminate the wires and mark the flows.
On universal templates, by rearranging the studs, it is possible to prepare wire harnesses according to various schemes.
Rice. 4.4. Preparing a wire harness using a universal template.
4.13. When preparing and laying wire harnesses using a three-dimensional template (see Fig. 4.5), you should:
Lay the wires on the dashboard;
Install the instrument sheet with the wires laid on the template;
Install the mounting clamps on the mounting structures in accordance with the assembled scheme;
Run the laying of wire flows descending from the instrument sheet to devices, devices, typesetting clamps and secondary buses;
Terminate the wires and attach their ends to the clamps;
Disconnect the ends of the wires from the terminals of the devices and secondary buses;
Remove the instrument sheet with wires from the template, transfer it to the device to be mounted and fix it on the panel.
Rice. 4.5. Harvesting wires using a three-dimensional template.
1 - three-dimensional template; 2 - mounting structure; 3 - assembly of typesetting clamps; 4 - front part of the template with a bundle of terminated wires; 5 - bandage; 6 - wiring harness
4.14. to make a large number of jumpers or simple flows, consisting of three or four wires, should also be done using templates (see Fig. 4.6):
In place, make one jumper-sample (see Fig. 4.6, a). If the jumper turns out to be bent in different planes, unfold its corners (but not unbend) into one plane;
Lay the prepared jumper sample on the first template - a piece of plywood or a smooth board (see Fig. 4.6, b). Drive studs 1 into one of the rings and along the inner sides of the corners of the jumper, which should protrude 10-12 mm above the plane of the plywood (board). Thus, a template is formed according to which the required number of jumpers can be made;
Remove jumper 2 from the studs, straighten it along its entire length and lay it on the second template - a piece of plywood (board) 200-250 mm wide (see Fig. 4.6, in) and a length that is 100-120 mm longer than the length of the straightened jumper;
On one side, along the width of the template, fix stop 3 with a height of 5-8 mm. Press the end of the jumper against the stop and mark the stripping line 4 and the wire cutting line 5 on the template;
According to the template, cut off pieces of wires of the required length, remove the insulation and terminate;
Bend the prepared wire segments on the first template, for which put one of the segment rings on the first stud, and then manually insert the wire alternately behind the subsequent studs and bend in one plane. Remove the prepared jumpers from the template studs. Bending jumpers in other planes, if necessary, should be done by deploying along the sample segment in the required directions.
Rice. 4.6. Jumper making
For the manufacture of simple (short) bundles, the sections of wires of the required length and configuration prepared in this way should be laid in bundles and bandaged.
A set of designed wires and cables connected to one another in some way and, if necessary, equipped with electrical installation elements (lugs, connectors, etc.) is called tourniquet. According to their purpose, the harnesses are divided into intra-block and inter-block.
Intrablock harnesses serve for the electrical connection of individual units, blocks and electrical parts inside the device, and interblock are used for electrical connection of various electronic equipment and devices into one system.
The design of the intrablock bundled installation is determined by the type of instrument housing, the requirements for their maintenance and repair. Depending on the placement of nodes in the body, such bundles can be: flat fixed with detachable connections; flat movable with one-piece connections; volumetric mobile; volumetric with movable outlets. Permanent connections for in-block installation are used mainly in electronic equipment designed for harsh operating conditions.
A typical technological process for the manufacture of a bundle consists of cutting wires and insulating tubes, laying wires on a template, tying them into a bundle, developing the ends of the bundle wires and marking them, controlling the manufactured bundle (continuity), protecting the bundle with insulating tape and its final control (visual inspection on compliance with the standard and continuity).
Harness layout template It is a rectangular plate made of plastic or plywood, on the surface of which a full-size harness diagram is applied and end and corner pins are fixed (Fig. 4.8).
Laying the wire begins by fixing it on the corner stud. Then the wire is laid according to the bundle scheme, bending it on the corner studs and fixing it on the end stud. The start and end pins have the same number. When all the wires are on the template, they are tied with linen thread.
In harnesses where it is impossible to replace damaged wires, spare wires are provided, the number of which is 8-10% of total number wires in the bundle, but not less than two. The length and section of the spare wires must be equal to the largest length and section of the wires present in the bundle. The length of the harness taps must be sufficient to connect to the nodes and elements of the device circuit without tension; in addition, you should have some margin of length (10-12 mm) for re-stripping and soldering each end of the wire.
When making harnesses, the following requirements must be met:
two or more parallel insulated wires running in the same direction and with a length of more than 80 mm must be bundled;
longer wires should be laid at the top of the bundle so that the branch of the bundle comes out from under them. Wires of small sections (0.2 mm 2) should be laid in the central part of the bundle;
depending on the operating conditions, as well as on the insulation of the wires included in the bundle, it is necessary to knit with threads, braid or tapes made of synthetic materials or winding with electrical insulating tapes or films. It is also possible to use electrically insulating tubes instead of winding with a tape or to perform mechanical and automatic knitting of bundles with threads with a tension that does not break the insulation of the wires;
the knitting step of the harness loops depends on the diameter of the harness and is selected from Table 4.3.
in places where the tourniquet is exposed (before and after it), bandages from 2-3 loops placed nearby should be made. At the beginning and end of knitting, there should also be bandages, which consist of two to five loops and have end knots. A loop must be made in front of each wire coming out of the bundle. An example of knitting and laying with a bandage is shown in Fig. 4.9;
depending on the number of wires and the diameter of the bundles, knitting must be done in one, two or more threads. Before knitting, it is recommended to grate or soak the threads with ceresin. Knots of linen threads after knitting must be covered with glue (for example, BF-4) or varnish; the ends of kapron threads after knitting must be melted.
After knitting the wires into a bundle, their ends are checked. In this case, all ends of the wires are marked in accordance with the wiring diagram.
Marking of wires, cable products and bundles during electrical installation, it should provide the ability to check electrical circuits, find faults and repair equipment. For marking, the following methods are used: laying in a bundle of wires that have different colors; coloring or numbering of polyvinyl chloride tubes used to clamp the ends of the insulation (the tubes are marked on the machine or the numbers are written by hand with marking ink);
putting plastic tags on the wires with symbols of the connection points;
making a mark on the insulation using colored printing foil (for wires with PVC and polyethylene insulation and cables of the PK type);
use of a metal tag (mainly for cables of the RK type);
use of adhesive marking tape (with a bandage of 1.5 ... 3 turns per wire or cable).
The marking is applied to both ends of the wire, cable or bundle at the points of their connection. The designation of wires, cables and bundles on marking tags, tapes and tubes or directly on the wires must correspond to the mark shown in the technical documentation. If the tag put on the wire or cable is not glued, it is tied on the wire (cable) with a knot or loop.
To mark wires with an insulation diameter of up to 1 mm, color marking tubes with an inner diameter corresponding to the wire diameter should be used.
The marking of wires in the bundle is done using tags or tapes from polymer materials. The length of the tags or the width of the tapes must be no more than 12 mm.
Then the harness is controlled by dialing, for which they are connected by a device (indicator) in series to the ends of the wires of the harness with the same numbers.
The control of complex harnesses is carried out on special semi-automatic stands according to a given program. All information about such control is recorded in the computer.
Harnesses, wires and cables are fixed to the electronic equipment case or its elements using: brackets, tapes, clamps, adhesives, mastics, compounds, threads, ribbons, plastic self-adhesive tapes.
Staples, tapes and clamps must correspond to the shape of the tourniquet and, when fastened, prevent its displacement.
In order not to damage the insulation of the wires when fastening with metal brackets and clamps, it is necessary to put elastic gaskets made of insulating material protruding beyond the edge of the brackets (clamps) by at least 1 mm.
The distance between brackets or clamps when attaching them to linear sections must be selected depending on the diameter of the bundle (wire or cable) in the range from 100 to 300 mm. Identical wires with a cross section of less than 0.35 mm 2 must be fastened with a distance between the fastening points of not more than 80 mm.
When glue or mastic is used to fix wires, bundles and cables, the distance between the gluing points should be selected depending on the diameter of the wire (bundle or cable) according to Table 4.4
Bundles with a diameter of more than 15 mm, when glued, are fixed with threads through a hole in the chassis.
The passage of a bundle, wire or cable through a hole in a metal chassis must be done through an insulating sleeve that is installed in the hole.
When passing wires, harnesses and cables from the fixed part of the device to the moving part (for example, from the case to the board or panel, etc.), it is recommended to place them in such a way that the wires are twisted and not bent when the moving part is removed. At the same time, the moving parts of the tourniquet do not need to be tied and leave the necessary margin in length.
Soldering and tinning: purpose, application and physical and chemical bases. Solder, fluxes, their brands and applications. Soldering technology with soft and hard solders, temperature conditions, heat sink. Group methods of soldering. Equipment and tools: purpose, design and methods of work. Methods for soldering wires of various grades and sections. Ultrasonic soldering. Laser soldering. Requirements for soldering connections, quality control. Appointment and application of tinning, quality control. Automation of soldering and tinning processes
Soldering- physico-chemical process of obtaining a joint as a result of the interaction of solid and liquid metal (solder). The layers resulting from this interaction at the boundaries of the seam and the surfaces of the parts to be joined are called junctions. To obtain junctions, it is necessary to remove oxide films from the joined surfaces and create conditions for the interaction of solid and liquid metals. During the crystallization of the more fusible solder that has interacted with the material of the brazed parts, a brazed joint is obtained.
One of the advantages of soldering is the ability to connect many elements that make up the product into a single whole in one go. Soldering, like no other connection method, meets the conditions of mass production. It allows you to connect dissimilar metals, as well as metals with. glass, ceramics, graphite and other non-metallic materials.
Tinning is the process of coating electrical elements with solder (ERE terminals, contact pads printed circuit boards, metallized holes, cores of mounting wires and cables, etc.) It is necessary to improve the solderability of the joined surfaces of the elements during their installation.
To make a good solder joint you need:
7. prepare the surfaces of the soldered parts;
8. activate soldered metals and solder;
9. provide interaction at the boundary "base metal - liquid solder;
10. create conditions for the crystallization of the liquid metal layer of the solder.
Surface preparation involves removing contaminants and oxide films from it that interfere with wetting - its molten solder. Films are removed by mechanical or chemical means. For mechanical cleaning
removed thin surface layer metal using sandpaper, a wire brush, etc. To increase productivity in processing large surfaces (for example, printed circuit boards), hydroabrasive treatment or cleaning with rotating brushes made of synthetic material into which abrasive particles are introduced is used. Surface roughness after mechanical cleaning contributes to the spreading of flux and solder, since small scratches on the surface are the smallest capillaries.
Chemical treatment (degreasing) of the surface of the product is carried out in solutions of alkalis or organic solvents (acetone, gasoline, alcohol, carbon tetrachloride, freon, alcohol-gasoline and alcohol-freon mixtures) by wiping, lowering into a bath, etc.
The cleaned parts must be immediately sent for tinning and soldering, since the shelf life for copper is 3-5 days, for silver - 10-15 days.
Activation of the joined metals and solder occurs with the help of various fluxes, the creation of a special gaseous medium or physical and mechanical effects (mechanical vibrations, ultrasonic vibrations, etc.). Activation is necessary, since when metals are heated and solder melts, their surface layers interact with atmospheric oxygen, which leads to the formation of a new oxide film.
Soldering with flux is the most common. The molten flux spreads over the soldered surface and solder, wets them and interacts with them, as a result of which the oxide film is removed. But the use of fluxes can lead to the fact that their residues after soldering, as well as the products of their interaction with oxide films, create slag inclusions in the brazed joint. This reduces the strength of the joint and leads to its corrosion. To avoid this, flux residues after soldering are washed off (wiped) usually with organic solvents.
To ensure interaction at the "base metal - liquid solder" interface, it is necessary to achieve good wetting of the base metal surface (ERE leads, petals, wires, etc.) with molten solder. The strength, corrosion resistance and other properties of solder joints. The process of wetting and spreading of solder is influenced by certain technological factors (the method of removing the oxide film, the brand of flux used, the soldering mode, etc.).
Crystallization of the liquid metal layer is carried out after the removal of the source of thermal energy. The crystallization process has a significant impact on the quality of solder joints.
Solder and fluxes for soldering designed to perform technological processes of hot tinning and soldering of non-ferrous and ferrous metals and metallic and non-metallic materials. They are divided into:
solders for low-temperature soldering with a melting point of less than 450 °C;
solder for high temperature folder with melting point above 450°C.
The symbol for solder grades consists of the letters "P" or "Pr" and the following abbreviated names of the main components: tin - O, lead - C, antimony - Su, bismuth - Vi * cadmium or cobalt - K, silver - Cp, copper - M , indium - Yin, zinc - C, nickel - N, gallium - Gl, germanium - G, titanium - T, gold - Zl, manganese - Mts, boron - B, phosphate - F, brass or lithium - L, iron - F , aluminum - A. Further, the content of the main component is indicated as a percentage of the mass. The letter "P", which stands at the end of the brand with a hyphen, means that the solder has an increased purity.
The main brands of solders and their melting temperature (T pl) are shown in Table 4.5.
Fluxes are intended for use in technological processes of soldering and hot tinning in order to remove the oxide film from soldered surfaces and solder, protect the surface of metals and solder from oxidation during soldering, as well as reduce the surface tension of molten solder at the metal-solder-flux interface
The symbol for flux grades consists of the letter "F" (flux) and the abbreviated name of its constituent components: K - rosin, Sp - alcohol, T - triethanolamine, Et - ethyl acetate, C - salicylic acid, B - benzoic acid, Bf - cadmium (or zinc) boron fluoride, P - polyester resin, D - diethyl amine, CK - semicarboside, Gl - glycerin, Fs - orthophosphoric acid, C - zinc chloride, A - ammonium chloride, B - water, L - laprol, Kp - catapine, M - maleic acid.
Fluxes can be low-temperature (use temperature less than 450 °C) and high-temperature (with use temperature over 450 °C). Depending on the corrosive effect on the metal to be brazed, they are divided into the following groups: non-corrosive inactive, non-corrosive weakly active, slightly corrosive active, corrosive active, corrosive highly active.
To avoid corrosion field connection, residues of corrosive and even slightly corrosive fluxes must be removed immediately after soldering. Remove fluxes with liquids in which they dissolve. For some brands of fluxes, these may be organic solvents, for others, water.
The most common brands of fluxes are given in Table 4.6.
In addition to fluxes, protective liquids are used to protect the mirror of molten low-temperature solder from oxidation in tinning and soldering baths (for example, ZhZ-1, ZhZ-2, TP-22). They are a mixture of petroleum oils with organic components.
The quality of solders and soldering fluxes is determined by technological characteristics: spreading coefficient (K p) and wetting time (t CM). Coefficient K p \u003d Sp /Sq, where S p is the area occupied by solder; Sq - area of unmelted solder in the initial state; tCM - the time during which the mounting element is tinned (should be no more than 3 s).
Soldering technology with soft and hard solders, temperature conditions, heat sink. The technological process of soldering consists of the following operations:
preparation of surfaces of connected elements for soldering; fixing the connected elements tightly to one another; applying a dosed amount of flux and solder; heating parts to a predetermined temperature and holding for a certain time; *
cooling of the soldered joint without shifting the parts included in it;
clearing the connection; soldering quality control.
Soft (low-temperature) solders (see Table 4.5) are used for electrical installation of equipment. Therefore, the temperature regimes for their use depend on the permissible temperature for those elements that take part in the installation. Soldering can be done with a soldering iron or in molten solder baths. When tinning and soldering with molten solder, the required bath temperature increases for each grade of solder according to the formula
tp = tnk + (45...80) °С,
where t n - solder temperature, tHK - crystallization start temperature (first digit T pl in table 4.5). Exceeding value (45...80) °С above tHK depends on the mass of the product to be soldered, the immersion time, the flux used, the restrictions on thermal effects in accordance with the technical specifications for the ERE.
To avoid overheating of soldered EREs, a heat sink is used, which is fixed to the ERE terminals during soldering.
There are other methods of heat removal during individual and group soldering of circuit boards. Mounting plate 2 (fig.4.10, a) is installed in fixture 5, made by injection molding in the form of a thermal block. The housing is built-in 6 racks 3, preloaded with springs, carrying support copper sockets 4 from above, having slots for leads. Mounted on these heat sinks circuit board 2 so that the conclusions of the radioelements fit into the slots of the sockets. The board is fixed in the device by turning the clamping bar 1. Thus, during the period of individual soldering, heat removal is carried out by the entire body of the device.
When group soldering hinged elements on the circuit board, the method of heat removal is used, carried out with the help of shot from aluminum wire with a diameter of 3 mm (Fig. 4.10, b). The shot 3 is loaded into the holder 1, where the circuit board 2 is inserted before group soldering by immersion or hydrostatic method. At the end of soldering, the shot spills out.
Hard (high-temperature) solders are used for structural soldering of mechanical joints in the manufacture of large-sized parts (for example, chassis, cases, etc.). High-temperature soldering of mechanical joints is performed in high-frequency current fields (HF), in furnaces or baths with molten salt.
Induction soldering (TVCh). A technological device for induction soldering or soldering with high frequency currents (HFC) is an inductor, which is a coil made of a highly conductive tubular material through which a coolant is pumped. An HDTV generator serves as equipment for soldering. Typically, induction brazing is used to join elements operating at microwave frequencies, such as microwave waveguides. The quality of the connection is improved when the soldering process is carried out in a vacuum or in a protective gas environment (hydrogen, nitrogen, or mixtures thereof). A big disadvantage of HDTV soldering is the need for special devices for each assembly unit.
Soldering in ovens with a controlled atmosphere ensures uniformity of heating. The soldered materials are heated in an active gaseous medium. In this case, fluxing can be omitted.
Soldering in bathtubs with molten salt is used to assemble large-sized products. The composition of the melt is selected in such a way that it provides the desired temperature and has a fluxing effect on the surfaces to be joined. The units assembled for soldering (the gap between the soldered parts should be within 0.05 ... 0.1 mm) are preheated in an oven to temperatures 80 ... 100 ° C below the melting point of the solder. This is necessary to avoid warping of parts, as well as to maintain the temperature in the bath. After soaking in the melt for 0.5 ... 3 minutes, the part, together with the fixture, is removed from the bath and cooled, and then thoroughly washed with water to remove flux residues.
Group methods of soldering. Group soldering methods in the production of REA are classified according to the sources of thermal energy, which is the main factor in the formation of solder joints (Fig. 4.11). Soldering elements with pin leads, which are placed on printed circuit boards, in mass production is carried out by two methods: immersion and solder wave.
Different options for implementing the group methods of the folder are shown in Figure 4.12. When soldering, the printed circuit board is immersed in molten solder for 2 ... 4 s to a depth (0.4 ... 0.6) h, where h - board thickness. As a result of the capillary effect, the mounting holes are filled with solder (Fig. 4.12, a). The simultaneous effect of temperature on the entire surface of the board leads to its overheating and can cause increased warping. To reduce the area of action of the solder, a special mask (made of paper or fiberglass) is glued to the board from the mounting side, in which holes for the contact pads are provided. Remaining flux solvent that got into the solder evaporates intensively, which leads to local non-solders. To reduce the number of non-solders, dip soldering is used with the board tilted (angle 5 ... 7 °) (Fig. 4.12, b) or apply mechanical vibrations to the board with a frequency of 50 ... 200 Hz and an amplitude of 0.5 ... 1 mm (Fig. 4.12, d, e). Good results can be obtained by drawing the board along the solder mirror (Fig. 4.12, in). In this case, the board is mounted on the fixture at an angle of 5°, immersed in solder and pulled along its surface. With this method, suitable conditions arise for the removal of oxidation products.
Selective soldering(fig.4.12, e) provides selective supply of solder to soldered parts through special dies made of of stainless steel. Between the board and the filters there is a layer of heat-resistant rubber. With selective soldering, the temperature of the board and the heating of the ERE are reduced, the consumption of solder is reduced, but the cost of manufacturing special dies can be significant.
Wave soldering is the most common method of group soldering. In this case, the board moves in a straight line across the crest of the solder wave. Its advantages are high productivity and short time of solder interaction with the board, which reduces ERE overheating and dielectric warping. A variation of wave soldering is cascade soldering (Fig. 4.12, g), in which several waves are used.
High quality soldering provides a way to immerse the board in a bath in which there is a grid with cells of 0.2x0.2 mm, for example, made of nickel (Fig. 4.12, h). When the board touches the grid, the solder is pressed through the cells and, under the action of the capillary effect, enters the gap between the leads and the metallized holes. When moving back, excess solder is drawn into the capillaries of the grid, which prevents the occurrence of "icicles"
Equipment and tools: purpose, design and methods of work. Depending on the type of production, soldering is carried out individually with a heated soldering iron or by various group methods.
Soldering with a soldering iron used for electrical installation in a single or small-scale production.
Design electric soldering iron shown in Figure 4.13. The required temperature regime for individual soldering is provided by the thermophysical characteristics of the soldering iron used: the temperature of the working end of the tip (tip 1 on, Fig. 4.13), the stability of this temperature, which is maintained using a thermocouple 4, the power of the heating element 14.
The temperature of the working end of the tip is set to 30 ... 100 ° C higher than the melting point of the solder, since during the soldering process the temperature of the soldering tip decreases due to heat costs when the soldered parts are heated. The recommended power of soldering irons for soldering microcircuits is 4 ... 18 W, for printed wiring 25...60 W, for soldering wires (bundles) 50... 100 W.
Soldering iron tips use copper, which is plated with a layer of nickel to increase its wear resistance. The sequence of the soldering process with a soldering iron: flux elements of the field connection with a brush dipped in liquid flux; heat the elements of the field connection by touching them with a soldering iron tip; introduce a twig of solder into the soldering area; withstand heating until the solder reaches normal spreading and fills all the gaps between the surfaces to be joined.
After soldering is completed, the parts must not be touched until the solder is completely hardened. The total time of soldering one mounting joint with a soldering iron is 1...3 s and cannot be more than 5 s.
If soldering and tinning is performed manually, it is necessary to ensure the removal of heat from the ERE, semiconductor devices, IP, etc., which are sensitive to its effects (according to the specifications for these elements). Heat sinks in the form of clips are fixed on the leads of soldered elements between the soldering points and the body of the element. After soldering, the heat sinks are removed no earlier than after 5 s. For reuse heat sinks change or cool.
Scheme of installation for selective soldering shown in Figure 4.14. Board 3 with leads, pre-coated with flux, is installed on the die 5. Each soldering place has its own die, the hole of which must coincide with this place. In this position, the board is fixed with a clamp 4. The molten solder 1 is in a volume closed on all sides, and its temperature is maintained by the molten salt bath 8, heated by electric heating elements 9. Through the bronze diaphragm 7, the vibrator 6 informs the molten solder with oscillations with a frequency of 100 Hz, which improves soldering quality. The solder is fed through the dies to the places of soldering by lowering the piston 2.
Scheme of installation for wave soldering shown in Figure 4.15. In the bath with molten solder, the temperature of which is maintained by a salt bath 2 with heating elements 1, there is a branch pipe with a vane pump 4 driven by an electric motor using a shaft 3. The wave height depends on the speed of the electric motor and is regulated by its change.
Cascade soldering differs from the wave one by the presence of several waves (Fig. 4.16) created by thresholds 3 on the inclined surface of the base 5. The molten solder 8 is supplied by the pump 7 through the slot 4 at a constant speed to these thresholds and flows down. The side walls 1 protect the solder from running off in other directions. As in the previous schemes, the temperature of the solder is maintained by a salt bath 9 with electric heaters 6.
These types of soldering are most appropriate for large-scale and mass production of boards with one-sided arrangement of attachments. They provide continuous movement of boards during soldering and its local heating.
Methods for soldering wires of different grades and sections. After processing, as described above, mounting copper wires and cable cores that do not have a coating must be serviced. Separate cores of wires must be twisted after stripping the insulation before tinning. When tinning conductors of wires and cables, flux is recommended to be applied at a distance of 0.3 to 2 mm from the insulation. Non-tinned sections of the core between the insulation and the tinned part of the wire are allowed up to 1 mm. The cross sections of the conductors must correspond to the load current. total area the cross section of wire cores and leads of the ERE connected to the contact should not exceed smallest area contact section.
When soldering wires and cable cores, the following requirements must be met: the wires must be connected to each other using electrical contacts. Options for fixing wire cores and ERE leads on contacts different designs shown in Figure 4.17:
no more than three wires can be soldered into each soldered contact hole. In this case, each wire must be fixed in the hole independently, without twisting it with other wires and ERE leads. If the mounting hole is small for soldering, it is necessary to use the reference wiring contacts; the wire must be attached to the screw terminals only with the help of cable lugs (for one screw terminal no more than two wires). Clamping contacts must be sealed with paint or varnish;
wires of small sections (less than 0.2 mm 2) must be mounted carefully; laying of wires must be carried out only once, so as not to break them off;
the supply of the drive in the form of a loop is placed on the board, but there should not be a wire hanging over its edge; the wire to the place of soldering must be brought from below; connection of mounting wires to the contacts must be carried out in such a way that the length of the bare part of the core of the mounting wire from its insulation to the soldering point is no more than 2 and no less than 0.5 mm (after soldering). When the contact spacing is less than 5mm, the wire exposure should not exceed 1.5mm.
Attaching the mounting wires to the screw terminal blocks is carried out different ways. With one of them, rings are made from stripped and tinned wire cores with a diameter greater than the diameter of the screw (Fig. 4.18, a). In another way, cable lugs with screw holes are attached to the wire cores by soldering, welding or crimping (Fig. 4.18, b).
The laying of wires in the cable lug is carried out in the following sequence: an electrical insulating tube with an inner diameter equal to the outer diameter of the wire is put on the wire; the core of the wire after cutting and tinning is inserted into the tip; the paws of the tip are crimped and soldered to the core of the wire from the inside to the paws; crimp the following paws on the insulation of the wire; an electrical insulating tube is put on top of the tip
(fig.4.18, b).
Ultrasonic soldering. Ultrasonic vibrations introduced into the solder destroy oxide films on the metal surface, improve its wetting with liquid solder, flow of solder into capillary recesses, promote degassing of the melt, which improves the quality of the soldered joint.
The cavitation that occurs under the action of ultrasound in the solder contributes to the destruction of oxide films, and acoustic currents carry away particles of oxides and contaminants, and remove metal at the sharp edges of the contact. Exposed areas of the metal are easily wetted with solder.
Laser soldering. Laser radiation differs from other sources of electromagnetic energy in a very narrow directionality. Concentrated heating by focused beam energy has a number of advantages, the main of which are: non-contact energy supply to products due to the removal of the source from the object of heating; the possibility of energy transfer through optically transparent shells both in a controlled environment and in a vacuum; heat different materials regardless of their electrical, magnetic and other properties in a wide range of regulation and control of soldering parameters. Depending on the design features and the mass of soldered products, as well as the properties of the materials to be joined, use different equipment of different capacities.
Requirements for solder joints, quality control. To
Solder joints are subject to the following requirements:
when fluxing, it is impossible to allow the flux to get inside the ERE and on the contact parts of the electrical connections;
the shape of soldered joints should be frame with concave fillets of solder (Fig. 4.19) and without excess solder. It should allow visually viewing through thin layers of solder the contours of the individual electrical elements included in the connection;
the surface of solder fillets along the entire perimeter of the solder joint should be concave, continuous, smooth, glossy or light matte, without dark spots and side inclusions.
The quality of the soldering is checked by external inspection, and, if necessary, using a magnifying glass. Well-made soldering should be considered one on which the contours of the parts to be joined are clearly visible, but all the holes are filled with solder. The solder must have glossy surface, without sags, cracks, sharp slopes. Possible types solder joint defects are shown in Figure 4.20.
mechanical strength solderings are checked with tweezers with polyvinyl chloride tubes put on its ends (when there are instructions for this in the TD). The tension force along the wire axis should be no more than 10 N. It is forbidden to bend the wire near the soldering point. After control and acceptance, the place of soldering is painted with a transparent colored varnish.
Appointment and use of tinning, automation of soldering and tinning processes. The high requirements for fixed connections of parts and elements during electrical installation carried out by soldering make it necessary to perform a hot tinning operation.
Usually, hot tinning of electrical installation elements is carried out only if their solderability is unsatisfactory (the need for solderability control is laid down in the TD). When tinning, the following requirements must be met:
tinning of electrical elements (ERE terminals, contact pads of printed circuit boards, metallized holes, cores of mounting wires, etc.) should be carried out mainly with the same solders as subsequent soldering. Temperature-sensitive EREs are tinned with low melting point solders. As well as during soldering, when tinning such EREs, it is necessary to use heat sinks;
the application of flux to tinned surfaces during manual tinning should be carried out for the minimum time necessary to ensure wetting of the surface with solder. In mechanized tinning, the entire surface that touches the solder is fluxed;
when tinning, the distance along the length of the ERE lead from the solder mirror to the ERE body must be at least 1 mm (or in accordance with the specifications for the ERE);
when tinning the ERE leads manually by immersion in solder or electric soldering irons, the duration of the process should not exceed the time specified in the technical specifications for the ERE. When there is no such restriction, the duration of tinning is taken to be no more than 5 s.