DE4208765A1 - ELECTRICAL CONTROL BOX AND MANUFACTURING METHOD - Google Patents

Abstract

A process for the production of service boxes comprised of a set of PCB's to which have been inserted and soldered the corresponding electrical components is characterised in that the production process includes at least some of the following: forming the printed conductors, insertion of conductive bridges, insertion of short pins and long pins in apertures in the PCB's, soldering of the short pins and long pins, checking the printed circuits, bending or angling of PCB's by milling of bases, "sewing" of PCB's along perimeter edges, assembly of covers and fuses, final checking and encasing. Details of the bridges, pins, PCB's, connectors and fuses are given.

Description

The manufacturing process of an operating box with bent or not bent over and "sewn" in the fold (multiple connected, s. u.) circuit boards (printed circuits) at least from one of the following operations: cutting and machining the pins, cutting, bending and machining the bridges (plug connections), Insertion of short or long pins, soldering (welding) the Pins on the circuit board (on the printed circuit board Circuit), insertion of springs and sockets and subsequent welding, checking the flat Circuit, bending the circuit and attaching a Trenners, "sewing" by inserting long pins, assembly of plastic covers, connector brackets and relays and finally assemble the fuses to then add one last check.

This invention patent application, like its title, already exists says from a series of "IMPROVEMENTS IN MANUFACTURING METHOD OF OPERATING BOXES AND THEIR PARTS ", their new Features in terms of construction and shape of these Share the task for which they are specific Wise designed with maximum security and effectiveness were.

We can use a car as an operating box Centralizing device of the electrical connections Define the system of the vehicle.

This operating box serves as a holder for the Protective equipment (fuses), as well as for the various necessary electrical components, such as. B. relays, diodes, electronic control modules and connectors.

All connections of the aforementioned components are in the box executed by means of one or more boards. Both the Boards as well as the connection terminals are suitable Plastic covers that are used for protection and as Serve attachment.

The operating boxes act as a connection center, which the electrical and electronic connections in one compact module and is able to Power and control signals from the various vehicles to distribute parts.

Boxes like those below regarding their Manufacturing processes have been described in part regarding various points thereof by entries the same claimant already described, such as. B. utility model no. 2 28 789, the title of which is "Elektrischer Distribution box for cars "reads utility model no. 2 39 279 for an "Improved Electrical Distribution block ", invention patents No. 5 33 433 for the "Improved electrical manufacturing processes  Distribution boxes ", additional certificate No. 5 34 841 for introduced improvements to invention patent No. 5 33 841 and finally invention patent no. 90 01 544 for "Improvements in the electrical manufacturing process Distribution boxes ".

The previous entries each contain partial Form the entirety of those developed by the signatory Improvements on electrical junction boxes are applicable and which is a previous technology reflect that over time through these entries is protected, the subject of this Patent application for invention consists in one Patent to incorporate the improvements regarding all previous entries have been made, the aim of which, like already said, it consists of different manufacturing parts and procedures of these operating boxes.

The outside of the operating boxes are above circuit elements in connection, which are Metal parts that are inserted into the copper and through Welding can be attached. The main advantage of every new one Product (operating box) is versatility of construction, which is a series of functional changes or improvements allowed at a very low price.

The improvements detailed below have the advantage, among other things, that they use the technology of Use printed circuit board and there are the following advantages to highlight:

• a) Less weight than the conventional system.
• b) Lower volume than the conventional system.
• c) Reducing the cost of current cabling systems.
• d) Easy assembly of the operating box in the car.
• f) Both for the user and for the workshop reachable.
• g) Security of connections.

The subject of this patent is the protection of improvements, those regarding the aforementioned previous entries were carried out, as well as the various parts of which there is a box, but not in a specific way a certain box, but the product, d. i.e. the Operating box arises in the construction phase and will according to the information provided by the customer and by adapting to the described technology created that the boxes of all kinds is common.

The manufacturing processes of operating boxes begin in one first phase with a study of the product, under consideration the technical and size requirements of the customer. In this first step you start to shape the to create printed circuit, be it in a simple one Circuit board (plate), multiple circuit board, double-sided, bent or similar circuit board, as well as the Plastic parts, the connections, closures Fastenings and separations between the boards support. In addition, in this first study, the  external assemblies checked, carried out in the box mainly plugs, fuses and relays.

When manufacturing the printed circuit board you go from a substrate and a circuit board, usually copper that is attached to it. The substrate used is usually cardboard with phenolic resins, referred to as FR-2, although in automotive applications Service boxes also the so-called FR-4 (glass fiber with Epoxy resin) can be used. As for the conductor material is concerned, its thickness will correspond to the amperage it must withstand being selected, taking a range of normal thicknesses used up to about 400 mm.

The conductor material is then protected by Apply a non-weldable mask or varnish about that; for this purpose the edges of the Conductor tracks are oxidized since the oxidation protection mask is not closed they got.

To the electrical connectivity between two sides To reach the printed circuit board, the short pen used. In the event that in an operating box different connected layers (multiple board) are used, which in turn are single or double-sided can be executed, the boards are mechanically long pins connected which are also an electrical connection can manufacture. This way we have in practice four copper sides, which we mutually at will can connect using the long pins (two sides a board with one side of another, the four sides with each other, one from a board with one from one other circuit board).

The arrangement of all these long pins extends over the whole outer circumference of the boards to make a good establish mechanical fastening connection, therefore this insertion of the long pins is called "sewing".

It is also possible that one for volume reasons selects bent circuit; so with the same practical conductor surface occupied a smaller space. This way we have the printed circuit at 90 °, 45 ° and even bent over to 180 °.

The plastic parts are used according to the needs of the Customers and in accordance with the design of the board constructed.

The main plastic parts are those of art fabric holders (mainly fuses, plugs and Relay).

The function that these plastic parts perform is mainly that the plugs, relays and fuses receive a mechanical support and at the same time they serve as storage between all parts of the board, as later is still described in detail. So that an operating box is functional, it must be on the vehicle, among other things be attached; this can be done using screws that  be attached directly to the sheet metal of the container, or Feed-through screws or suitable clips.

Another one of the assembly of printed circuits The parts used within the operating boxes are the Separations; their job is an electrical Isolation between the opposing paths of the To form multiple boards.

It is for storing relays, fuses and plugs necessary that a special design for each component the plastic bracket is made so this Component can be attached in this storage.

Thus, a box is constructed so that bearings for Fuses, plugs, relays and for the pull terminal finds.

The board components used in the manufacturing mentioned The methods most commonly used are the Sockets, clip-like parts that are on the board be inserted and store or fasten a spring need (generally from a fuse, a relay or another component), which causes the electrical contact will be produced; the springs are components that are in the Board are embedded and they serve as a cross connection to the outside area; they are characterized in that they a large width and height in relation to their thickness point. A spring assembly forms a support link external connections; the bridges are devices to the To connect tracks of a printed circuit when it is out The same connection is not possible due to lack of space Manufacture help of the railways yourself.

Wire bridges are also used, which are the same Function like the bridge described above, but they connect tracks that are at an angle of 45 °, 90 ° or 180 ° are bent. They are welded on the side (soldered) on which the substrate is embedded and none Transfer takes place.

Another element used is the header for printed circuits. It is any one Bridge type that is inserted into the printed circuit if the conventional bridge previously described is not can be used, be it by electrical means or due to electrical necessities. In the end power screws are also used, their geometry and key features depend on the function that they is assigned.

Further details and features of this invention patent applications are given in the course of the following Description supplied in which we refer to the drawings related to this report. In it are in the most important details of the previously mentioned manufacturing process. These Details are given as examples below Reference to a possible case of practical production a general operating box, but there is none Restriction to the manufacturing details that are there  be specified; for this reason the present one See description as an illustration of how the Manufacturing an operating box can look like without Restriction of any kind for other fabrications below of different construction, which, however, a part or the All of the operations described are also included would.

Below we give a detailed list of the various elements mentioned in this patent application: ( 10 ) punching, ( 11 ) welding of the components, ( 12 ) welding of the components, ( 13 ) bridge insertion, ( 14 ) pin insertion, ( 15 ) welding or soldering the pins, ( 16 ) checking the flat circuit, ( 17 ) bending, ( 18 ) making separations, ( 19 ) "sewing", ( 20 ) side welding, ( 21 ) cover and safety assembly, ( 21 a) assembly the fuse holder covers, ( 21 b) installing the relay holder covers, ( 21 c) installing the connector holder covers, ( 22 ) final check, ( 22 a) packaging, ( 23 ) substrate, ( 24 ) conductor material laminate, ( 24 a) pin environment, ( 25 ) short pin, ( 26 ) long pin, ( 27 ) plug holder, ( 27 a) small partitions, ( 28 ) fuse and relay holder, ( 28 a) small partitions, ( 29 ) operating box, ( 30 ) springs, ( 31 ) Printed circuit board, ( 32 ) socket n, ( 33 ) cells, ( 34 ) cells, ( 35 ) separation, ( 36 ) hinge, ( 36 a) flexible laminate, ( 37 ) lugs, ( 38 ) axes, ( 39 ) fuses, ( 40 ) pull-off clamp, ( 40 ) wings, ( 40 b) mandrels, ( 40 c) small claws, ( 40 d) overhang (attachment), ( 41 ) wings, ( 41 a) bracing, ( 42 ) bridges, ( 42 a) angled end pieces, ( 43 ) Power screws, ( 43 a) head piece, ( 43 b) deformation areas, ( 43 c) multifaceted body, ( 44 ) laser beam, ( 45 ) mirror, ( 46 ) prism, ( 47 ) components, ( 48 ) laser beam, ( 49 ) light beam, ( 49 ) welding material.

Fig. 1 is a diagram of the manufacturing process of an operating box ( 29 ).

Fig. 2 is a partial cross section (elevation) of a printed circuit board on which a short pin ( 25 ) has been attached, and in another embodiment two boards ( 31 ) which are connected by attaching a long pin ( 26 ).

Fig. 3 is a perspective view of two boards ( 31 ), which are connected by "circumferential sewing" by means of long pins ( 26 ).

Fig. 4 contains partial cross-sections (elevations) of a series of boards ( 31 ) which are bent at right angles, at an acute angle, in a semicircular arc and at an angle of 445 °.

Fig. 5 is a partial longitudinal section (elevation) of a circuit board ( 31 ) on which a milling has been carried out in order to divide the multiple circuit board into individual plates.

Fig. 6 is a longitudinal section (elevation) of an operating box ( 31 ) on which a connector holder ( 27 ) and a fuse holder ( 28 ) are mounted, each of which is equipped with the corresponding cells ( 33 ) and ( 34 ); inside they consist of a set of elements from the box.

Fig. 7 is a longitudinal section (elevation) of a separation ( 35 ), with different sections of this separation with a detailed representation of the bracket and hinges.

Figure 8 is a detailed top view of a bracket bracket ( 40 ) mounted on a fuse bracket ( 28 ).

Fig. 9 is a top, elevation and side view of a clip.

Fig. 10 is a top view and also an elevation, partially broken down, of the connector mounting system to a connector bracket ( 27 ) after it has been inserted into the springs ( 30 ).

Fig. 11 is a longitudinal section (elevation) of a board ( 31 ) on which a bridge ( 42 ) has been inserted.

Fig. 12 shows a front elevation, a bottom view and the course of a bridge ( 42 ).

Fig. 13 shows an elevation, partially broken down into sections, of a power screw ( 43 ).

Fig. 14 shows an elevation, partially broken down into sections, of a welding system for laser beams.

Fig. 15 shows an elevation, partially broken down into sections, of an ultrasonic welding system.

In one of the most important embodiments of the subject matter of this patent application, the manufacturing process of an operating box ( 29 ) with bent or not bent and "sewn" boards ( 31 ) consists of at least some of the following operations:

• a) Cutting the short or long pins ( 25 and 26 ) to size and machining their end points using an endless rod.
• b) cutting the bridges ( 42 ) and bending the angled end pieces ( 42 a) and machining their end points.
• c) Insertion of short ( 25 ) or long pins ( 26 ) and the bridges.
• d) soldering the pins ( 25 ) and ( 26 ) to the circuit board ( 31 ) by wave soldering or by ultrasound or laser welding.
• e) use of components such. B. springs ( 30 ) and sockets ( 32 ).
• f) welding of springs ( 30 ) and sockets ( 32 ).
• g) Check the flat circuit.
• h) bending of the circuit ( 31 ), with a separation ( 35 ) being attached in the middle.
• i) "Sewing" by inserting long pins ( 26 ) and later bending them.
• j) Assembling the previously injected connector holder Plastic covers.  
• k) Assembly of the previously injected relay and fuse bracket plastic covers.
• l) Assemble the fuses to make a final one afterwards Carry out verification.

The manufacturing process of an operating box, the circuit board of which is bent and "sewn", takes place in a line consisting of a series of automatic insertion devices of the various components, which are programmable by computer, transport lines and automated welding, as well as a system with an artificial view, which different colors of fuses discovered in their respective places; the batch is then electrically controlled and the reference number and date are printed on the operation box ( 29 ) if the part is correct or any defective parts are automatically ejected from the batch.

The soldering or welding is done in the following way, in Depending on the type of soldering or welding performed:

• a) wave soldering; the non-soldered or welded printed circuit ( 31 ) first passes through the "fix" device to remove any contaminants that may be on the copper and thereby achieve better soldering or welding; then the circuit goes through a preheat area where the ambient temperature is about 400 ° C with the aim of reducing the heat shock it receives from contact with the tin and finally it goes through the gush of tin which is at a temperature of about 245 ° C, thereby the tin returns to the soldering area.

The whole process can be controlled by certain Variables like the tow speed of the transported Band, the plate or the height of the surge of tin that the areas to be soldered are changed.

So-called 60-40% tin is to be used, i. H. with a Composition of 63% tin and 17% lead.

• b) The laser welding, as shown in Fig. 14, is carried out by a laser beam ( 48 ), which strikes a prism ( 46 ), which emits the light beams ( 49 ) via a few mirrors ( 45 ), which these beams focus on those areas ( 24 a) reflect that are near the pins, causing the melting to take place. The beam ( 49 ) can strike the pin of the component to be welded directly, or a part of the pin and partially the copper of the circuit board ( 24 ) around it, ie the area ( 24 a).
• c) The welding can alternatively also be carried out by ultrasound, as can be seen from Fig. 15, so that the pins ( 47 ) of the components are connected to the copper or the printed circuit board ( 24 ), by fusion therewith due to this ultrasound application, whereby there is the advantage that the side opposite the weld remains usable.

The main operations that form part of this improved manufacturing process are described below with reference to the drawings. In Fig. 2 a pin ( 25 ) can be seen which is inserted into a circuit board ( 31 ) with the addition of welding material ( 49 ). Using a long pin ( 26 ), the electrical connection of four copper sides ( 24 ), which we can connect with one another at will with the help of these long pins ( 26 ), can be carried out with the variants of two sides of a circuit board, ie the conductive parts ( 24 ), a circuit board ( 31 ), with the conductive part ( 24 ) of another circuit board ( 31 ). There are also the following connection options: the four conductive sides ( 24 ) with one another or one conductive side ( 24 ) of a circuit board ( 31 ) with one side ( 24 ) of the other.

The arrangement of the long pins ( 26 ) is carried out as shown in Fig. 3, on the entire circumference of the boards ( 31 ), such that a good mechanical connection between them is achieved.

For reasons of space, it is also possible for the circuits ( 31 ) to be reshaped by bending them accordingly, as a result of which the same practical surface of the webs takes up a smaller volume, or we adapt to the exact geometries required for the automobile manufacturer are; in this way we bent the printed circuit ( 31 ) to 90 °, 45 ° and even to 180 °.

As can be seen in Fig. 4, there are two options when bending to 90 °: bending outwards or inwards, for which purpose the corresponding milling of the substrate ( 23 ) is carried out, according to the details given in Fig. 4 sees. Depending on the selected angle, the configuration of the milling on the substrate ( 23 ) differs completely in some cases from the 90 ° milling; this creates a notch with a perfectly straight profile, with vertical parallel sides, while in another 90 ° processing the milling in the substrate ( 23 ) produces sides which form an angle of approximately 90 ° with one another.

If the bend is made to 45 °, we have two Bending options, the outward bending and the Bend inwards. When turning outwards the milling produces a notch with vertical parallel Sides, while when turning inward the milling creates a notch with sides that are at an angle of form about 45 °.

When bending to 180 °, the distance between two Boards determined by the milling width, so that this Distance equal to twice the width divided by the number Phi, must be.

It must be taken into account that for all types of bending of the substrate ( 23 ) and, after the same milling process, a small substrate layer ( 23 ) must remain on the uncut copper or printed circuit board layer ( 24 ), the thickness of which varies between 0.02 and 0.01 mm.

Another system that is for better utilization is used is the bend and the subsequent one "Sew" through the edges that are not those of the fold are.

If the boards ( 31 ) have small dimensions, they can be combined into another, larger one and the insertion and welding processes can be carried out as if they were one. In order to divide the multiple circuit board into individual circuit boards, a milling must be carried out as shown in Fig. 5.

The plastic parts, such as. B. the connector holder ( 27 ) and the fuse holder ( 28 ) are designed according to the requirements of the customer, but they generally fit into each other and, as shown in Fig. 6, surround the interconnected boards by means of the corresponding short ( 25 ) or long ones Pins ( 26 ) or bridges ( 42 ), both sides of the circuit boards ( 24 ) having sockets ( 32 ) and springs ( 30 ) positioned inside cells ( 33 ) that are designed to act as a guide serve for the entry of the corresponding plugs or fuses.

Between the boards ( 31 ) the appropriate partitions ( 35 ) are attached, which, as can be seen in Fig. 7, are equipped with the corresponding hinges ( 36 ), which have breakpoints, e.g. B. included within a point circle, which are equipped with a small flexible lamella ( 36 a) to give them a steady course, and at the end points of these separations ( 35 ) are some lugs ( 37 ) in cross section in the form of Arrows located at the end points of axes. The separation between two boards ( 31 ) is positioned by these lugs ( 36 ).

The fastening system of the plugs requires that in the construction of the holder for the same ( 27 ) a few wings ( 41 ) are provided which are equipped with struts ( 41 a) and these wings are fastened to the cell walls ( 33 ), as shown in FIG represents; there is shown a connector holder ( 27 ) which has a plurality of wings ( 41 ) and springs ( 30 ); The same connector holder ( 27 ) is also shown in this Fig. 10 as soon as these connectors have been received and they are locked by the struts ( 41 a).

The bridges ( 42 ), which are manufactured automatically, consist of thin brass and copper rods, which are cut in a first step in order to then produce a few bridgeheads with a truncated prismatic configuration at their angled end points ( 42 a).

Finally, the power screw (43) 13 comprise, as shown in Fig. A body (43 c) with more than one side (poliedrischer) side surface that extends at the top by a head (43 a), while in the lower part of the multi-sided body (43 c) there are some deformation areas ( 43 b) which, as shown in FIG. 13, penetrate into the printed circuit ( 31 ) and by means of the corresponding deformation operation, the power screw ( 43 ) is located inside an operating box ( 29 ) and also in the conductor parts ( 24 ) a board ( 31 ) locked.

After considering the drawings and the explanations that we have given, it becomes clear that the invention patent application on which this description is based, a simple and enables efficient production by a Entire operations with great ease can be managed, which is without a doubt a new one Manufacturing result represents.

After having adequately described what from this patent application for invention exists in accordance with the attached pictures, it is understandable that in it Changes of details of any kind are introduced that are considered appropriate, provided that they do not have the nature of the patent the following claims is summarized.

Claims (19)

1. Operation box, in particular for motor vehicles, characterized by one or more isolations ( 35 ) separate boards ( 31 ) with one or both sides printed circuit boards made of conductive material ( 24 ), on which construction parts ( 11 ) attached and are soldered on, the printed circuits ( 24 ) on the two sides of a circuit board ( 31 ) or the printed circuits ( 24 ) of a plurality of circuit boards ( 31 ) being connected in an electrically conductive manner by means of pins ( 25 , 26 ). 2. Operating box according to claim 1, characterized in that the two conductive sides ( 24 ) of a circuit board ( 31 ) are conductively connected by short pins ( 25 ). 3. Operating box according to claim 1 or 2, characterized in that to produce an electrically conductive connection between the various boards ( 31 ), each having one or two conductive sides ( 24 ), long pins ( 26 ) are used in addition to creating a mechanical connection, whereby four conductor material sides ( 24 ), two conductor material sides ( 24 ) of a circuit board ( 31 ) with a conductor material side ( 24 ) of another circuit board ( 31 ) or a conductor material side ( 24 ) of a circuit board ( 31 ) with another conductor material side ( 24 ) of another circuit board ( 31 ) are electrically connectable. 4. Operating box according to one of claims 1-3, characterized in that the mechanical connection between boards ( 31 ) on the entire outer circumference of the boards ( 31 ) by means of long pins ( 26 ) it follows. 5. Operating box according to one of claims 1-4, characterized in that one or more boards ( 31 ) are bent, the two parts of the board ( 31 ) angles of +/- 45 °, +/- 90 ° or 180 ° lock in. 6. Operation box according to one of claims 1-5, characterized in that the sinkers (31) plug, fuse and relay mounts (27, 28) are arranged, said brackets (27, 28) by separating walls (27 a , 28 a) are divided into groups of cells ( 33 , 34 ). 7. Operating box according to claim 6, characterized in that for removing the fuses ( 39 ) from the fuse holders ( 28 ) pull-off parts ( 40 ) with wings ( 40 a) are arranged, in the outer part and center of which there are mandrels ( 40 b) , And that in the inner part of the wing ( 40 a) and at their end points small claws ( 40 c) and at the top of these parts ( 40 ) Before cracks ( 40 d) are arranged. 8. Operating box according to claim 7, characterized in that perpendicular to the connector holder ( 27 ) project the wings ( 41 ), which are equipped at their end points with struts ( 41 a), as a device for locking the connector, which in a cell ( 33 ) for connection with springs ( 30 ) can be inserted. 9. Operating box according to one of claims 1-8, characterized in that the insulation ( 35 ) between two boards ( 31 ) consist of a film (plate) made of thin non-conductive material, at the end points alternately and perpendicular to their front and Rear side projecting lugs ( 37 ) are arranged, which are based on axes ( 38 ), both of which are arranged at a fixed distance from a hinge ( 36 ) which is provided with flexible film ( 36 a). 10. Operating box according to one of claims 1-9, characterized in that individual conductor tracks of the printed circuit ( 42 ) can be connected to one another with the aid of wire bridges ( 42 ). 11. Operating box according to one of claims 1-10, characterized in that it can be fastened to a vehicle by means of screws, the screws ( 43 ) forming a multifaceted main body ( 43 c), the upper part of which is provided with a threaded head piece ( 43 a) is extended and from its lower part some deformation areas ( 43 b) emerge. 12. A method for producing an operating box according to one of claims 1-11, characterized by the steps:

• - Inserting the components ( 11 ) into the boards ( 31 )
• - Soldering the components ( 11 ) with the boards ( 31 )
• - Insertion and welding or soldering of pins ( 25 , 26 ) for producing electrical connections between printed circuits ( 42 ) of one or more circuit boards ( 31 )
• - Insertion and welding or soldering of pins ( 26 ) on the circumference of boards ( 31 ) to produce a mechanical connection between the boards ( 31 )
• - Check the circuits
• - Attaching covers
• - packaging.

13. The method according to claim 12, characterized in that the attachment of the pins ( 25 , 26 ) by means of laser beam welding ( 48 ) through a prism ( 46 ) which splits the light bundle ( 49 ) and breaks on mirrors ( 45 ) . 14. The method according to claim 12, characterized in that the pins ( 25 , 26 ) are attached by ultrasonic welding, in which the feet ( 47 ) of the pins ( 25 , 26 ) with areas ( 24 b) of the conductor material plate ( 24 ) to be merged. 15. The method according to any one of claims 12-14 for the manufacture of an operating box according to claim 5, characterized in that one or more boards ( 31 ) by 90 ° or 180 ° by producing a milling groove with a rectangular cross section in the boards ( 31 ) be kinked off. 16. The method according to claim 15, characterized in that when the boards ( 31 ) bend by 180 °, the two board parts have a distance which corresponds to twice the groove width divided by π. 17. The method according to any one of claims 12-14 for the manufacture of an operating box according to claim 5, characterized in that when the boards ( 31 ) bend by -90 °, a milling groove on the substrate layer ( 23 ) of the board ( 31 ) is attached, the side edges form an angle of approximately 90 °. 18. The method according to any one of claims 12-14 for the manufacture of an operating box according to claim 5, characterized in that when the boards ( 31 ) bend at 45 °, a milling groove with parallel side edges in the substrate layer ( 23 ) of the boards ( 31 ) is introduced. 19. The method according to any one of claims 12-14 for the manufacture of an operating box according to claim 5, characterized in that when the boards ( 31 ) are bent by -45 °, a milling groove in the substrate layer ( 23 ) of the board ( 31 ) is introduced, the side edges of which form an angle of 45 ° to one another.