FR2656494A1 - DEVICE FOR SHIELDING AND INSULATING AN ELECTRONIC CIRCUIT BOARD. - Google Patents

Abstract

The invention relates to a device for shielding and isolating an electronic circuit board (10) comprising on one face components (14) and on the other face welds (16) of said components, said board being fixed on a frame (20) comprising a metal plate (22) running along the board on the weld side. It is characterized in that it comprises a sheet (30) made in one piece and folded so as to wrap the card, the sheet comprising an insulating base (32a, 34a, 36a) which supports, on the component side only and on its face opposite said components, a conductive shielding layer (34b). According to a variant, for a card fixed to an insulating plate, the sheet comprises a base formed by the superposition of an insulating inner layer and of an outer conductive layer and supports, on the side of the components only and opposite to those. here, a second insulating layer.

Description

This invention relates generally to insulation and

  shielding printed circuit boards. In the prior known art, an electronic circuit board is conventionally mounted at a small distance from a metal plate located on the side of the welds of the circuit and forming part of a frame. This card ensures the shielding of the circuit on the face considered, and a thin film of insulating material is provided between the card and the metal plate to avoid any risk of grounding the protruding conductors of the various components Furthermore, there is also provided on the component side a second metal shielding plate, lined with an insulator to prevent contact of the components with said second plate The mounting of the assembly requires a large number of screws, nuts, balusters and / or spacers for mounting the card on the frame and for mounting the second plate of shielding and sound insulation above the board, side

components.

  Such a known solution is disadvantageous in that the presence of these mechanical mounting means and the various conductive and insulating plates substantially increases the cost price of the apparatus, and requires excessively long assembly times The weight of the apparatus is also increased to a substantial extent. The present invention aims to overcome these drawbacks of the prior art and to provide shielding and insulating means for an electronic circuit board which are economical, simple to

implement and lightweight.

  Another object of the invention is to allow to bring an electronic circuit board closer to other structures or neighboring bodies, without the means 2 - shielding and insulation are an obstacle to a

such approximation.

  To this end, the invention relates, in a first aspect, to a device for shielding and isolating an electronic circuit board comprising on one side components and on the other side solders of said components, said card being fixed on a frame comprising a metal plate along the board on the side of the welds thereof, characterized in that it comprises a sheet made in one piece and folded so as to wrap the card, the sheet having a base of insulating material which supports, on the component side only and on its opposite side to said components, a layer of electrically

shielding conductor.

  Optionally, the sheet further comprises a second insulating layer disposed over the shielding layer. According to another essential aspect, the present invention relates to a device for shielding and isolating an electronic circuit board comprising on one side of the components and on the other side welds of said components, said card being fixed on a chassis comprising a surface of insulating material along the board on the side of the welds thereof, characterized in that it comprises a sheet made in one piece and folded so as to wrap the card, the sheet having a base constituted by the superposition an inner layer of insulating material and an outer shielding layer of an electrically conductive material, said base supporting, on the component side only and on its opposite side to said components, a second layer of

insulating material.

  Advantageously, the shielding layer is connected to a mass via at least one screw 3 - fixing the card on a support, the contact with the screw or screws being ensured by designing the second insulating layer to clear locally the shielding layer at said screws, or again by folding locally on themselves the shielding layer and the

second insulating layer.

  It is particularly convenient to secure the portion of the sheet extending between the card and the metal plate in position by means of board support struts, which pass through sparse holes.

in said portion of the sheet.

  Preferably, the polyester insulation layer or layers are produced, while the armor layer

can be aluminum.

  Other aspects, objects and advantages of the present invention will become more apparent upon reading the

  following detailed description of several forms of

  preferred embodiment thereof, given by way of nonlimiting example and with reference to the accompanying drawings, in which: Figure 1 is a schematic sectional view of an electronic circuit board equipped with shielding means and according to a first embodiment of the invention, FIG. 2 is a view of the assembly of FIG. 1 in a particular environment, FIG. 3 is a diagrammatic sectional view of an electronic circuit board equipped with shielding and insulating means according to a second embodiment of the invention, FIG. 4 is a view of the assembly of FIG. 3 in a particular environment, FIG. 5 is a detailed view of a variant. embodiment of the shielding and insulating means of FIG. 3, and FIG. 6 is a schematic sectional view of an electronic circuit board equipped with shielding and insulating means according to a third embodiment of FIG.

embodiment of the invention.

  Referring firstly to Figure 1, there is shown an electronic circuit board generally designated by the reference 10 In this case, it is a printed circuit board comprising the printed circuit 12, components 14 on one side thereof (here the upper face) and welds 16 of said

  components on the other side of it.

  In the present example, the card 10 is fixed on a frame 20 made of metal and having a flat plate 22 The card 10 is fixed on the plate 22 by means of screws 24 and spacers 26 (only one

  screw and only one spacer being shown).

  According to a first aspect of the present invention, for shielding and electrical isolation of the card 10, a one-piece sheet generally indicated at 30 is used which includes a first portion 32 extending between the card 10 and the frame plate 22 and a second portion 34 which extends over the card, on the component side A "U" fold 36 of the sheet along an edge (here the right edge) of the card combines the two parts 32, 34 of the unit sheet. The lower part 32 of the sheet consists of a single layer 32a of an insulating material such as polyester On the other hand, the U-shaped part 36 and the upper part 34 comprise, in addition to the insulating layer 36a, 34a, respectively , corresponding to the extension of the layer 32a, a layer of a conductive material 36b, 34b which is attached to the outside of the polyester layer and is fixed thereto, locally or over the entire surface, by any means suitable, especially bonding or use of an intermediate film of adhesive - double-sided material is preferably used as

conductor aluminum.

  It will be noted here that, in FIG. 1 and the following, the thicknesses of the various layers of the sheet have been exaggerated for the sake of clarity. Thus, on the weld side, the insulation between said welds 16 and the metal plate 22 is provided by the single polyester layer 32a, while said plate 22 itself provides the shielding And on the component side, the insulation is provided by the polyester layer 34a, while the aluminum layer 34b

  carried by it provides the shielding.

  Fixing the sheet 30 around the card 10 can be done by any means In this case, the lower portion 32 is floating between the card 10 and the frame plate 22, and is held in place by holes 38 Above the card, the portion 34 of the sheet is simply placed, and its maintenance is ensured on one side (right) by the transition fold 36 with the part 32, and on the other side (left) by holes formed in said part and through which are engaged the screws 24 It should be noted that this attachment, by which the screw heads are in contact with the aluminum layer 34b, also ensures the grounding of this layer of

shielding 34 b.

  Moreover, with this solution, the screws 24 locally ensure the reciprocal attachment of the layers 34a and 34b of the portion 34 of the sheet, and it is not necessary to use specific fixing means in this region. a simplified embodiment, it is only possible to provide, in addition to the fixing by the screws 24, an adhesive attachment to the

  neighborhood of the part 36 located opposite.

  FIG. 2 shows the case where the card, the frame 20 and the shielding and insulating sheet 30 of FIG. 1 are incorporated in a housing or partition or the like 40 made of insulating material. It can be observed in this figure that, for reasons of size, parts 42 of the housing 40 which project towards the card 10 are embedded to a certain extent in free spaces 15 which exist between the components 14. distance between the card 10 and the housing 40 can be reduced,

  for a greater compactness of the whole.

  According to another essential aspect of the invention, it is the use of a flexible sheet

  in accordance with the above description which authorizes a

  such that the upper portion 34 of the sheet is capable of deforming to conform to the shape of the relatively sinuous space left between the components 14 and the projecting portions 42 of the housing. Satisfactory flexibility can be achieved by using a polyester layer with a thickness of about 50 to 250 microns, and a layer

  aluminum of a thickness of the same order of magnitude.

  FIGS. 3 and 4 show a second

  basic embodiment of the present invention.

  In these figures and on the following, elements or parts identical or similar to those of the preceding figures are designated by the same reference numbers. In this example, the card 10 is no longer fixed on a metal frame, but directly on a flat surface 44 of the housing 40 made of insulating material. The shielding of the board 10 on the solder side is in this case

more assured.

  Furthermore, the card 10 is disposed in the

  sinage organs, schematically indicated at 50 (see Figure 4), which must be avoided at all costs they come into contact with the mass, and in this case with the conductive layer 34 b of the upper portion 34 of

the sheet 30.

  To solve these problems, according to another essential aspect of the present invention, the sheet 30 has a first portion 32, between the card and the portion 44 of the housing, which is constituted by the superposition of an insulating layer 32a, side

  welds, and a conductive layer 32b, on the housing side.

  These two layers 32a and 32b extend at 36a, 34a and 36b, 34b, respectively, to define on the other side of the card 10 an insulating layer vis-à-vis the components 14 of the card 10 and a shielding layer of said card, respectively Here again, the sheet 30

is therefore in one piece.

  Furthermore, the portion 34 of the sheet also comprises, outside the conductive layer 34b, a second insulating layer 34c which is intended to prevent the members 50 from coming into contact with the mass

constituted by layer 34 b.

  In this example also, the insulating layers are preferably polyester and the conductive layer

is preferably aluminum.

  Thus, the lower part 32 of the sheet provides the shielding of the board and the insulation of the welds 16 with respect to the layer 32b forming the shield, while the upper part 34 provides the shielding, the insulation with respect to the components 14 and

  the insulation with respect to the members 50.

  According to the arrangement of neighboring members 50, the second insulating layer 34c and the conductive layer 34b may be extended or not at the fold to 1800 of the sheet; in the present example, the layers 34b and 34c are stopped at the transition between the parts 34b and 34c.

36 of the sheet.

  8 - The sheet 30 of this embodiment can be held in place for example as the sheet 30

Figures 1 and 2.

  Here again, the additional layer provided on the outside of the portion 34 of the sheet may be attached to the polyester / aluminum unitary composite with the part 32 by any appropriate means, involving or

not the screws 24.

  In the example of FIG. 3, the grounding of the layer 34b is carried out by stopping the outer layer 34c at a determined distance from the free edge, opposite to the fold 36, of the underlying layers 34a, 34 b, so as to clear on a marginal area the aluminum layer 34b; the electrical contact between the screw heads 24 and said layer 34b is thus made possible; on the other hand, it is in this case necessary to provide a fixation of the layer 34c on the layer 34b in the

  free end region of the first.

  FIG. 5 illustrates an alternative embodiment in which the screws 24 are able to perform simultaneously the grounding of the conductive layer 34b and the local fixing of the layer 34c on the layers 34a and 34 According to this variant, the layers 34b and 34c, in the region of the edge opposite the fold 36, are folded back on themselves for a short distance at the location of the screws. In this way, the conductive layer is released. 34 b Holes are provided for the passage of the screws 24 and, when they are tightened, both the grounding of the

  shielding layer 34b and the local assembly of the layers.

  FIG. 4 shows the situation in which, in order to reduce space requirements, the projecting members 50 are embedded in open spaces

  left between the components 14 of the card 10.

  Here again, the portion 34 of the sheet is sufficiently flexible to adapt to the relatively sinuous 9-gap that exists between the card 10 and the members 50, while effectively shielding the card 10 (and / or 50) and the isolation of

  components 14 and members 50 vis-à-vis the shield.

  An electronic device of greater

compactness can thus be obtained.

  Of course, the embodiments of FIGS. 1 and 3 can be combined. Thus, FIG. 6 shows a variant in which the lower part 32 of the sheet 30 comprises a single layer 32a of insulating material, while the upper part has three layers, namely a conductive layer 34b sandwiched between two insulating layers 34a and 34c The insulating layer 34a is integral with the layer 32a, and the upper portion 34 can be made of relating to the layer 34a which prolongs the layer 32 to an insulating / conductive complex, by adhesive bonding

  or by any of the other means described above.

  This variant lends itself particularly to the case where the frame which supports the card 10 is metallic and itself ensures the shielding side welds, while parts or members 50 which must be imperatively isolated from the mass are likely to come into contact

  of the upper part 34 of the sheet.

  The present invention is particularly well suited to the case where the card 10 is a digital circuit card, while the members 50 are components (transformer, capacitors, rectifiers, etc.) of a power supply circuit of the card 10. is good

  3 U understood that this application is not limiting.

  The present invention is not limited to the embodiment described above and shown in the drawings, but those skilled in the art will be able to provide any

  variant or modification in keeping with his spirit.

  It should be noted in this regard that the expressions "higher", "lower", etc. are used throughout -

  of the description must be understood in a sense

  relative, the card 10 and its environment can in practice have any desired orientation, including vertical. he -

Claims (12)

  A device for shielding and isolating an electronic circuit board (10) comprising on one side components (14) and on the other side welds (16) of said components, said board being fixed on a chassis (20). ) having a metal plate (22) along the weld side of the card thereof, characterized in that it comprises a sheet (30) made in one piece and folded so as to envelop the card, the sheet comprising a base (32a, 34a, 36a) of insulating material which supports, on the component side only and on its opposite side to said components, a layer of electrically conductor (34b) shielding.   2 Device according to claim 1, characterized in that the shielding layer (34b) is connected to a mass via at least one screw   (24) fixing the card on a support.   3 Device according to one of claims 1 and   2, characterized in that the sheet (30) comprises in   in addition to a second insulating layer (34 c) disposed above the shielding layer.   4 Device according to claim 3, attached to claim 2, characterized in that the second insulating layer (34c) is arranged so that the shielding layer (34b) is locally cleared for   contact with the screw head or heads (24).   Device according to claim 3, attached to claim 2, characterized in that, in a region opposite the fold (36) of the sheet, the shielding layer (34b) and the second insulating layer (34c) are locally folded on themselves for a contact with the screw head or heads (24).   6 Device according to one of claims 1 to   , characterized in that the portion (32) of the sheet extending between the card (10) and the metal plate 12 - (22) is fixed in position by means of card support spacers (26), which cross holes (38)   arranged in said portion of the sheet.   7 Device according to one of claims 1 to   6, characterized in that the insulating layer or layers   (32a, 34a, 36a, 34c) are polyester.   8 Device according to one of claims 1 to   7, characterized in that the shielding layer (34b) is in aluminium.   9 A device for shielding and isolating an electronic circuit board (10) comprising on one side components (14) and on the other side welds (16) of said components, said board being fixed on a chassis comprising a insulating material surface (44) along the weld side of the card, characterized in that it comprises a sheet (30) made in one piece and folded so as to envelop the card, the sheet comprising a base consisting of the superposition of an inner layer of insulating material (32a, 34a, 36a) and an outer shielding layer (32b, 34b, 36b) of an electrically conductive material, said base supporting on the component side only and on its opposite side to said components, a second layer of material insulation (34c).   Device according to claim 9, characterized in that the shielding layer (32b, 34b, 36b) is connected to a mass by means of at least one screw (24) for fixing the card on a support.   11 Apparatus according to claim 10, characterized in that the second insulating layer (34c) is arranged in such a way that the shielding layer (34b) is locally disengaged for contact with the or the screw heads (24).   13 - 12 Device according to claim 10, characterized in that, in a region opposite the fold (36) of the sheet, the shielding layer (34b) and the second insulating layer (34c) are locally folded over them- same for contact with the head (s) of screws (24).   13 Device according to one of claims 9 to   12, characterized in that the portion (32) of the sheet extending between the card and the insulating surface (44) is fixed in position by means of board support spacers (26), which pass through holes ( 38) in said portion of the sheet.   14 Device according to one of claims 9 to   13, characterized in that the at least one insulating layer   (32a, 34a, 36a, 34c) are polyester.   Device according to one of claims 9 to   14, characterized in that the shielding layer (32b, 34 b, 36 b) is aluminum.