Method for producing a shielding case

Abstract

Method of producing a shielding casing (4) in which there is provided a sealing and shielding profile section (9) which fills a gap between first and second adjoining casing portions (1, 2) and which comprising pasty material is applied under pressure from a coordinate-controlled applicator device (5) having an applicator needle or nozzle directly on to onto the first casing portion and then sets there elastically adhering thereto in self-supporting relationship, wherein the sealing and shielding profile section is produced by simultaneously applying at least one first material (8a) with material properties adapted for a good sealing action and a second material (8b) with material properties adapted to a good shielding action, from the applicator needle or nozzle (6) provided with at least a first and a second passage (6a, 6b), whereby the second material firmly adheres to the first material.

Description

w Wherein the screw holes 1b in the casing bottom portion are provided for partially self-tappingly screwing in self-tapping screws 3 while the screw holes 2b in the cover each have a countersink for accommodating the screw head of the respective screws 3. This screw connection permits the device casing 4 to be opened and re-closed repeatedly if required.

The Figure diagrammatically shows the way in which an arm 5 of a coordinate-controlled handling device (not shown overall as such) guides an applicator needle 6 having two concentrically extending passages or ducts 6a, 6b, with hose connections 7a, 7b for feeding two seal starting materials 8a, 8b which are under pressure, in the direction of the arrow A, over the edge section of the casing bottom portion 1. In that operation, an approximately U-shaped sealing and shielding material strand 9 whose core 9a comprises the first starting material 8a and whose surface layer 9b comprises the second starting material 8b is distributed on to the edge section and firmly adheres there.

The first starting material 8a is an unfilled silicone mixture which is set to a pasty-gel-like condition and which hardens in air and at ambient temperature while the second starting material 8b is a silicone conductive mixture which is set to a pasty condition and which is filled with a proportion of about 50% by mass of silvered nickel particles, the matrix of the silicone conductive mixture being of substantially the same composition as the first material 8a to which however a surface active agent is additionally added as a bonding agent or primer, in a proportion of less than 1% by mass.

After issuing from the needle 6 hardening of the material strand 9 begins immediately from the surface—without additional technical measures—to constitute an elastic, freely formed sealing and shielding profile section having a soft core and a highly conductive but also still relatively elastic surface layer which encases the core on all sides. After hardening is substantially concluded, the cover 2 is fitted on to the bottom portion 1—as symbolically indicated by the arrow B—and screwed to the bottom portion 1 by way of the screws 3, in which case the material strand 9 which has hardened to form the sealing and shielding profile section is elastically deformed without adhering to the cover 2 and reliably seals and shields the gap between the casing portions 1, 2.

FIGS. 2a to 2j are cross-sectional views showing various sealing and shielding profile sections in accordance with preferred embodiments together with the applicator needles which are respectively used for the production thereof. The finished profile sections are each shown with parts of the adjacent casing surfaces 1′ and 2 respectively, wherein reference 1′ (unlike the specification relating to FIG. 1) stands for a metal casing bottom portion while the material adopted for the cover 2 is again plastic material with a metal coating 2a. (It will be appreciated that the invention can also be applied in relation to an entirely metal casing.)

The sealing and shielding profile section 91 shown in FIG. 2a comprises a non-conductive base portion 91a and a conductive layer 91b which covers the base portion 91a over rather more than half the periphery thereof, and it is applied to the casing portion 1′ by means of an applicator needle 61 diagrammatically shown in FIG. 2b, having a first duct or passage 61a of circular cross-section and a second duct or passage 61b, which partially surrounds it, of a cross-section which is in the form of a segment of a circular ring.

The sealing and shielding profile section 92 shown in FIG. 2c comprises a non-conductive base portion 92a and a conductive flank portion 92b which extends around same over somewhat less than half the periphery thereof, and is applied to the casing portion 1′ by means of an applicator needle 62 shown in FIG. 2d, having a first duct or passage 62a of circular cross-section and a second duct or passage 62b which partially surrounds it, of a cross-section which is approximately in the shape of a segment of a circular ring The sealing and shielding profile section 93 shown in FIG. 2c differs from that shown in FIG. 2c in that provided on both sides of a non-conductive base portion 93a is a respective conductive profile portion 93b, 93c which extends over rather less than half the periphery thereof The profile section 93 is produced by means of an applicator needle 63 as shown in FIG. 2d, with a first duct or passage 63a of circular cross-section and two ducts or passages 63b, 63c which are arranged laterally thereof and which are of a cross-section that is approximately in the form of a segment of a circular ring.

In the case of the sealing and shielding profile section 94 shown in FIG. 2g, a non-conductive core portion 94a is completely encased by a conductive layer 94b whose thickness however is smaller in the gap space in the proximity to the casing portions 1′, 2. This profile section is formed by means of an applicator needle 64 diagrammatically shown in FIG. 2h, having a first duct or passage 64a of circular cross-section and a second duct or passage 64b surrounding it, of ellipsoidal cross-section.

The sealing and shielding profile section 95 shown in FIG. 21 2i is of a similar (three-component) structure to that shown in FIG. 2e, but the association of material is different: provided on each side of a conductive, shielding central portion 95a is a respective non-conductive, sealing profile portion 95b, 95c. The profile section 95 is produced by means of an applicator needle 65 as shown in FIG. 2d, with three ducts or passages 65a to 65c which are arranged in side-by-side relationship and which are of approximately rectangular cross-section.

The invention is not limited in terms of its implementation to the preferred embodiments described hereinbefore. On the contrary, it is possible to involve a number of variants which make use of the illustrated solution even in configurations of a different nature.

Thus the specification of the first material as being ‘non-conductive’ is to be understood in the broad sense as meaning that this material is of markedly lower conductivity (for example corresponding to a markedly lower level of metallic filling) than the second material. The use of a plastic material on a silicone basis is not a necessary feature; it is also possible to use a neoprene or other elastically setting material which also does not necessarily have to harden at ambient temperature.

The geometry of the profile section to be produced and the needle and nozzle cross-sectional shape which is to be adopted in relation thereto depend on the purpose of use and the specific configuration of the shielding casing and, besides the variants diagrammatically illustrated in FIGS. 2a to 2j, many others can also be used.

Claims

1. A method of producing a shielding casing for mechanically protecting and electromagnetically shielding an electronic functional unit, in which there is provided a sealing and shielding profile section which fills a gap between a first and second adjoining casing portions and which comprises pasty material applied under pressure from a coordinate-controlled applicator needle or nozzle directly on to onto the first casing portion which then sets elastically, adhering thereto in self-supporting relationship, comprising: producing the sealing and shielding profile section by simultaneously applying at least a first material which sets elastically, with material properties which are adapted to a good shielding sealing action, and a second material, which sets elastically, with material properties which are adapted to a good sealing shielding action, from the applicator needle or nozzle which is provided with at least a first and a second passage, whereby the second material adheres firmly to the first material and wherein one of the first and second materials forms a base portion and the other of the first and second materials forms a layer that at least partially surrounds the base portion.

2. The method of claim 1, wherein the second casing portion is brought into contact with the sealing and shielding profile section after substantially complete hardening of the first and/or second material.

3. The method of claim 1, wherein the first material used is a substantially non-conductive plastic material which hardens in air and at ambient temperature and the second material used is a plastic material which is made conductive by means of electrically conducting inclusions, the second plastic material being of the same kind of material as the first material.

4. The method of claim 3, wherein particles comprising a metal or an alloy with a high level of electrical conductivity are used as electrically conducting inclusions.

5. The method of claim 3, wherein the first material contains a non-conductive filler.

6. The method of claim 1, wherein a bonding agent is used when applying the first and/or second material.

7. The method of claim 1, wherein the first passage of the applicator needle or nozzle is surrounded at least over a part of its periphery by the second passage.

8. The method of claim 1, wherein application of the sealing and shielding profile section is effected by using an applicator needle or nozzle whose first passage is of substantially circular cross-section and is concentrically surrounded at least in portion-wise manner by the second passage, wherein the latter is of a cross-section that is substantially in the form of a segment of a circular ring.

9. The method of claim 1, wherein the second material is applied in the profile cross-section with irregular thickness.

10. The method of claim 9, wherein the second material is applied on the inside of the casing with a greater thickness than in the part towards a casing portion and/or on the outside of the casing.

11. The method of claim 3, wherein the non-conductive plastic material is made of silicone and has thixotropic properties.

12. The method of claim 4, wherein the particles are fibres or flakes of silver or silver-bearing alloy.

13. The method of claim 5, wherein the non-conductive filler is oxidic or ceramic.