FR2531597A1 - Printed circuit for heavy currents. - Google Patents

Abstract

It comprises a metal plate 1, one face of which is covered over by an insulation 5, the other face being uncovered, and in which are cut out electrical circuits separated by passages 3 and linked together by linking bridges 4, the said insulation being interrupted above orifices 6 let into the plate for the positioning of connecting pins, characterised in that the insulation 5 is also introduced into the said passages 3 in such a way as to reinforce the strength of the said plate, the said insulation being capable of being removed at least partially from the said passages. Application especially in interconnection housings used in motor vehicles.

Description

Printed circuit for high currents.

 The present invention relates to a printed circuit for high currents and, more particularly, a printed circuit produced in a metal plate.

 Printed circuits for the production of service plates for motor vehicles hardly exceed 0.1 mm thick and are limited in their use by voltage drops and by the lack of withstand at short circuits.

When one wishes the passage of high currents it is necessary either to increase the width of the electrical circuits which would then lead to the use of very large plates incompatible with the tendency to miniaturization of the circuits and to the space available on vehicles, or to increase the thickness of the plate to avoid prohibitive dimensions
To overcome the drawbacks due to excessive dimensions and / or plate thickness, it has been proposed to produce the printed circuit in the form of a stack of circuit plates separated from each other by an insulating sheet. preferably attached to a plate. The circuits are cut from metal plates and are interconnected by bridges which can be removed by stamping, for example, so as to form separate electrical circuits. This effectively amounts to dissociating the functions which must be provided by all of said circuits. In any case, the stack must be kept tight in a case and the various plates connected to one another by pins inserted by force into holes provided for this purpose in said plates. Such stacking is notably described and represented in French patent No. 2,362,504.

 The present invention relates to a printed circuit which allows the passage of high currents without being limited by the thermal diffusion due to the passage of current as occurs with known stacked circuits.

 The printed circuit according to the invention is of the type comprising a metal plate one side of which is covered with an insulator, the other side being uncovered, and in which are cut electrical circuits separated by passages and connected together by bridges of connection, said insulator being interrupted above threatened openings in the plate for positioning the connection pins, and it is characterized in that 11 insulator is also introduced into said passages so as to reinforce the holding of said plate, said insulator being capable of being at least partially removed from said passages.

 According to another characteristic, the recesses in the insulation on the covered face are larger than the positioning orifices of the connection pins so as to allow fixing of said blanks on said plate by wave welding.

 This feature is of great interest in the mass production of circuit boards and connection boxes in which they are mounted.

In fact, in the stacks of known plates, the stack is first introduced into the connection box before forcibly positioning the connection pins which must be of length greater than the height of the stack and include means for retainers which prevent them from being extracted from the connection orifices. Thanks to the present invention, the connection pins can be fixed to the housing before the plates are put in place.

Other advantages and characteristics will emerge more clearly on reading the description given above by way of indication but not limiting of a preferred embodiment of the invention, as well as of the appended drawing in which
Figure 1 is a top view of a face of the printed circuit according to the invention;
Figure 2 is a top view of the other side of the printed circuit shown in Figure 1
Figure 3 is a sectional view on an enlarged scale, of a recess in the insulation and corresponding to an orifice for the passage of a connection pin
Figure 4 is a sectional view on an enlarged scale of a passage formed between the two electrical circuits and filled with insulation.

 The printed circuit according to the invention and represented in FIGS. 1 and 2, comprises a metal plate 1 of appropriate thickness e, - in which are cut circuits 2 delimiting between them passages 3. The cutting of metal circuits or tracks can be chemical or more economically mechanical with waste recovery. The circuits 2 are interconnected by connecting bridges 4. One face of the plate I is covered with an insulating layer 5 (Figure 2) except in certain places 6 and in particular around orifices 7 formed in the plate and intended for the positioning of connection pins nàn shown.

 One or more bands 8 transverse to the longitudinal axis of the plate 1 are also kept bare, on both sides of the plate 1, without insulation, to allow folding of said plate along this or these bands. To this end, the bare zones 8 have cutouts 13 and holes 14 to facilitate folding along the holes 14.

 Around the orifices 7, the insulation has a chamfer 9 which allows a better flow of the material to be welded in the recess 10 created by the insulation around said orifices 7 and above all which allows a wave welding carried out by moving the coated side of the plate on a solder bath. The weld, during displacement, slides on the insulation and fills the recesses 10 until substantially the chamfer, thus realizing a connection between the metal plate 1 and the end. connection pins passing through the openings 7 and opening into the recesses 10.

 On the other side of the plate not covered with insulation, the passages 3 formed between the circuits 2 are filled with insulation 5. Preferably, the insulation 5 of the passages forms an additional thickness 11 and covers, on both sides other of each passage, a small part of the adjacent circuits to thereby form two beads 12 (Figures 2 and t). Once the plate 1 is assembled with the insulation, the mechanical connecting bridges 4 can then be removed by cutting so as to achieve the appropriate separation of the electrical circuits.

 The covering of one face of the plate 1 and the filling of the passages 3 with insulation can be carried out by overmolding said plate, taking great care to avoid bending of said plate. The insulating material is a thermosetting moldable plastic and preferably a polyester compound loaded with glass fibers.

 Another method consists in using a highly charged precut insulating sheet so that during the gluing and pressing of the sheet on the metal plate there occurs a creep of the resin which would then partially fill the passages between the electrical circuits without the formation of beads on the other side. The support sheet can for example be a glass fiber fabric or bakelized paper.

 Finally, another application of the printed circuit according to the invention could be envisaged. It consists in using the assembly described above not in an interconnection box as envisaged, but as a support for electronic components, by mounting for example resistors and / or capacitors and inductors on the isolated face, these components being fixed by connecting conductors in the holes provided for fixing the connection pins.

 Of course, the invention is in no way limited to the embodiment of the example described and shown, it is capable of numerous variants accessible to those skilled in the art, depending on the applications envisaged and without departing from the scope of the invention.

Claims (12)

 1. Printed circuit for high current, of the type comprising a metal plate (l) one side of which is sewn by an insulator (5), the other side being uncovered, and in which electrical circuits (2) are cut apart. - res through passages (3) and interconnected by connecting bridges (4) gledit insulator being interrupted above orifices (6) formed in the plate for the positioning of connection pins, caradérisé in that insulator (5 ) is also introduced into said passages (3) so as to strengthen the holding of said plate, said insulator being capable of being at least partially removed from said passages.  2 Circuit according to claim 1, characterized in that on the exposed side the insulator, introduced into the passages, forms at least one extra thickness (11) covering part of the circuits adjacent to said passages.  3. Circuit according to claim 2, characterized in that on the exposed face of axa lacquer and on either side of each passage the insulator covers part of the circuits adjacent to said passages.  4. The circuit as claimed in claim 1, characterized in that the insulating recesses (10) on the covered face are of dimensions greater than those of the orifices (6) for positioning the connection pins so as to allow the connection pins to be fixed to said plate by wave welding.  5. Circuit according to claim 1, characterized in that on each side of said plate is provided at least one bare area, continuous and totally devoid of insulation so as to allow the folding of the printed circuit along said bare area.  6. Circuit according to one of claims 1 to 5, characterized in that the insulator is a thermosetting moldable plastic.  7. Circuit according to claim 6, characterized in that the thermosetting plastic material is a polyester compound loaded with glass fibers.  8. Circuit according to claim 4, characterized in that the recesses in the insulation are provided with chamfers.  9. Circuit according to one of claims g to 8, characterized in that it is used as a support for electronic components  10. Circuit according to one of claims 1 to 5, characterized in that the insulation is a precut support sheet heavily loaded with a resin so that during bonding and pressing occurs a creep of said resin so as to fill the passages between electrical circuits  11. Circuit according to claim 10, characterized in that the support sheet is a glass fiber fabric.  12 2 Circuit according to claim 10, characterized in that the support sheet is bakelized paper.