GB2041828A

GB2041828A - A Method for Manufacturing Interconnectors

Info

Publication number: GB2041828A
Application number: GB8003770A
Authority: GB
Original assignee: Shin Etsu Polymer Co Ltd; Shin Etsu Chemical Co Ltd
Current assignee: Shin Etsu Polymer Co Ltd; Shin Etsu Chemical Co Ltd
Priority date: 1979-02-08
Filing date: 1980-02-05
Publication date: 1980-09-17
Also published as: JPS5951112B2; DE3004523A1; CH646280A5; GB2041828B; JPS55105985A

Abstract

The present invention provides a method for manufacturing interconnectors of rubbery elastomer in which a carrier sheet 1 is provided with relief stripes 2 of an electrically conductive material on one surface, overlaid with a sheet 3 of an uncured electrically insulating rubber elastomer and bonded by pressing to sink the relief stripes into the uncured rubbery elastomer sheet which is then cured. The carrier sheet is then peeled from the cured rubber elastomer sheet and the product sliced in a plane perpendicular to the longitudinal direction of the stripes. In an embodiment a plurality of the rubber sheets each having the stripes are overlaid one on the other so that a manner that the stripes on each of the sheets run in the same direction and bonded together into an integrated block which is then sliced in a plane perpendicular to the longitudinal direction of the stripes. <IMAGE>

Description

SPECIFICATION A Method for Manufacturing interconnectors The present invention relates to a method for manufacturing interconnectors formed of an electrically conductive rubbery elastomer which are used for connecting electronic circuits by contacting with pressure.

In the prior art, the above mentioned interconnectors of the so-called press-contact type made of an electrically conductive rubbery elastomer are manufactured by the following procedure. For example, a plurality of sheets of electrically conductive and insulating rubbery elastomers are laid one upon another alternately and bonded together into an integrated stratified body which is sliced in a plane pernendicular to the plane of the base sheets to give striped sheets.These striped sheets and a plurality of sheets of an electrically insulating rubbery elastomer are further laid one upon another alternately and bonded together to form an integrated stratified body which is again sliced in a plane perpendicular to the plane of the sheets and also perpendicular to the longitudinal direction of the stripes (see, for example, Japanese Patent Disclosure 52-29958 and U.S.

Patent 3,982,320).

The above described procedure is disadvantageous because the procedure involves two-fold stratification and two-fold slicing necessarily leading to an increase in the production cost due to the complexity in the manufacturing procedure of the finally obtained interconnectors.

A method according to the invention comprises the successive steps of providing a carrier sheet on one surface thereof with relief stripes formed of an electrically conductive material, overlaying the carrier sheet having the stripes with a sheet of an uncured electrically insulating rubbery elastomer, bonding the carrier sheet and the sheet of the uncured rubbery elastomer by pressing whereby the relief stripes of the electrically conductive material sink into the uncured rubbery elastomer sheet, subjecting the uncured rubbery elastomer sheet to curing whereby the relief stripes of the electrically conductive material are bonded to the cured rubbery elastomer, separating the carrier sheet from the cured rubbery elastomer sheet so that the stripes of the electrically conductive material are transferred to the cured rubbery elastomer sheet, and slicing the cured rubbery elastomer sheet having the stripes of the electrically conductive material embedded therein in a plane perpendicular to the longitudinal direction of the stripes.

A modification of this method for manufacturing an interconnector having contacting points arranged in rows and columns comprises the successive steps of providing a carrier sheet on one surface thereof with relief stripes formed of an electrically insulating material, overlaying the carrier sheet having the stripes with a sheet of an uncured electrically insulating rubbery elastomer, bonding the carrier sheet and the uncured rubbery elastomer sheet by pressing whereby the relief stripes sink into the uncured rubbery elastomer sheet, subjecting the uncured rubbery elastomer sheet to curing whereby the stripes are bonded to the cured rubbery elastomer sheet, separating the carrier sheet from the thus cured rubbery elastomer sheet whereby the stripes are transferred to the cured rubbery elastomer sheet, overlaying a plurality of the thus obtained cured rubbery elastomer sheets each having stripes one on the other in such a manner that the stripes on each of the sheets run in the same direction, bonding the thus overlaid sheets adhesively into an integrated laminated body, and slicing the integrated laminated body in a plane perpendicular to the plane of the sheet and also perpendicular to the longitudinal direction of the stripes.

Alternatively, the curing step of the rubbery elastomer sheets may be undertaken after a plurality of the sheets having the stripes embedded therein are overlaid one on the other and curing of the rubbery elastomer sheets and bonding of them into an integrated laminated body are effected simultaneously under pressure.

Embodiments of the invention will now be described by way of example with reference to the drawings in which:~ Fig. 1 is a perspective view of a carrier sheet provided with plurality of relief stripes of an electrically conductive rnaterial on one surface thereof.

Fig. 2 is an illustration of the sequential steps of the method of the invention by cross sections in which: (a) is a cross sectional view of a carrier sheet provided with a plurality of relief stripes on one surface thereof; (b) is a cross sectional view of the carrier sheet with relief stripes overlaid with a sheet of an uncured electrically insulating rubbery elastomer; (c) is a cross sectional view of the carrier sheet and the uncured rubber sheet as bonded together so as that the relief stripes have sunk into the uncured rubber sheet; and (d) is a cross sectional view of the carrier sheet under peeling from the cured rubber sheet having the stripes of the electrically conductive material embedded therein.

Fig 3 is a perspective view of the carrier sheet with the relief stripes and the sheet of the uncured rubbery elastomer sheet bonded thereto corresponding to Fig. 2(c); Fig. 4 is a perspective view of a finished interconnector having the contacting elements arranged in a single row.

Fig. 5 is a perspective view of an interconnector similar to that shown in Fig. 4 but provided with a lining layer.

Fig. 6 is a perspective view of an integrated block prepared by overlaying a plurality of the rubber sheets with stripes one on the other.

Fig. 7 is a perspective view of a finished interconnector having the contacting elements arranged in rows and columns.

As is shown in Fig. 1, a carrier sheet 1 is first provided on one surface thereof with a plurality of relief stripes 2 formed of an electrically conductive material. Various kinds of films or sheets are suitable for preparing the carrier sheet 1 in so far as they have sufficient mechanical strengths including films of synthetic plastics such as polyethylene terephthalate, polyethylene, polypropylene, polystyrene, polyimide resins, polyamide resins and the like, regenerated cellulose and cellulose derivatives such as "Cellophane" (Registered Trade Mark), nitrocellulose, cellulose acetate and the like and foils of metals such as aluminum and copper. The thickness of the carrier sheet 1 is also not limitative in so far as dimensional stability of the carrier sheet 1 can be ensured.

The electrically conductive material for forming the relief stripes 2 can be a commercially available electroconductive coating composition or electroconductive paint which is used as such.

However, it is recommendable that the electrically conductive material is prepared by uniformly dispersing a sufficient amount of a powder of a conductive material such as carbon, graphite, metals and alloys, metal carbides and the like in a polymeric matrix which exhibits rubbery elasticity after curing such as certain kinds of silicone resins and silicone rubbers, polyurethane polymers and some kinds of thermoplastic resins.

The method for providing the relief stripes 2 on the surface of the carrier sheet 1 is well known in the art and conventional printing techniques, e.g.

screen printing, gravure printing and offset printing, can be used when the electrically conductive material has a consistency of something like a printing ink. The relief stripes 2 formed by printing, e.g. screen printing, are subsequently subjected to curing, for example, by heating.

It is necessary that the relief stripes 2 are formed on the carrier sheet 1 with a sufficiently high dimensional accuracy. The pitch P of the stripes 2 and the width W and height H of each stripe 2 should be determined in accordance with the dimensions of the electronic circuit boards with which the interconnector is to be used in contact. For example, the pitch P is in the range from 0.1 to 6 mm, width W is in the range from 0.05 to 3 mm and height H is in the range from 0.01 to 0.6 mm. The method of screen printing is particularly suitable when relief stripes 2 with a relatively large height H are desired.On the other hand, finer relief stripes 2 can be formed advantageously by the so-called photoprocess using a photocurable electroconductive coating composition in which the carrier sheet 1 is first coated uniformly with the coating composition followed by stripewise exposure to light to effect photocuring of the composition on the irradiated areas and removing the uncured portion by washing with an organic solvent. At any rate, the combination of the carrier sheet 1 and the electrically conductive material for forming the relief stripes 2 is of some significance; the adhesion between the carrier sheet 1 and the cured material of the relief stripes 2 is not excessively strong in order to facilitate the transfer of the cured stripes 2 to the rubbery elastomer sheet in the subsequent step.

Referring now to Fig. 2 which illustrates the successive steps of the method by the cross sections, the carrier sheet 1 having the relief stripes 2 as is shown in Fig. 2(a) is then overlaid on the surface having the stripes 2 with a sheet of an uncured electrically insulating rubbery elastomer 3 as is shown in Fig. 2(b). As the rubbery elastomer for the sheet 3 are used various kinds of synthetic rubbers as well as certain kinds of plastic resins exhibiting rubbery elasticity upon curing. Examples of these rubbery polymers are polyesters, polyurethanes, polybutadienes, polyisoprene rubbers, silicone rubbers, styrene-butadiene rubbers, polychloroprene rubbers and the like.If desired, the rubbery elastomer for the sheet 3 may be expanded into a foamed body simultaneously with curing so that the cured sheet 3 can have a resilience suitable for the base material of an interconnector with which a very small compressive load is sufficient to obtain a reliable interconnection. This technique of foaming the sheet 3 is particularly recommended when the interconnector is to be used in certain compactsize electronic instruments such as extremely thin electronic pocketable calculators where no strong compression can be applied to an interconnector sandwiched between the terminals of circuit boards.

The principle of foaming is well known in the art e.g. it comprises admixing the uncured rubbery elastomer with a foaming agent such as N,N'dimethyl-N,N'-dinitrosoterephthalamide, N,N'dinitrosopentamethylene-tetramine, azodica rbonamide, azobisisobutyronitrile, benzenesulfonyl hydrazide and the like.

The uncured rubbery elastomer sheet 3 is prepared by a conventional means such as sheeting or topping and the thickness of the sheet 3 is determined according to the desired dimensions of the finished interconnector.

-The carrier sheet 1 and the uncured rubbery elastomer sheet 3 are bonded as is shown in Fig.

2(c), for example, by pressing with a pinch roller or with two pressure plates sandwiching the carrier sheet 1 and the overlying uncured sheet 3.

Owing to the plasticity of the uncured sheet 3, the relief stripes 2 on the carrier sheet 1 sink into the uncured sheet 3 by this pressing to be embedded in the uncured sheet 3 as is shown in Fig. 2(c). It is necessary that the electrically conductive material forming the relief stripes 2 has been imparted with a sufficient degree of hardness by curing in advance in order that the cross sectional contour of each of the stripes 3 is not deformed by this pressing.

When no satisfactory hardness can be obtained even by the curing of the electroconductive material owing to high loading with an electroconductive filler, an auxiliary reinforcement of the relief stripes 2 is obtained by providing a coating layer using a flowable coating composition such as a room-temperature curable silicone rubber composition prior to the overlaying with the uncured sheet 3.

The next step of the method is the curing of the uncured rubbery elastomer sheet 3 overlying the carrier sheet 1 with the relief stripes 2 embedded therein. Curing is usually effected by heating and the heating schedule is determined according to the particular type of the rubbery elastomer. It is necessary that strong adhesive bonding is obtained by this curing between the relief stripes 2 and the cured rubbery elastomer sheet 3. Fig. 3 is a perspective view of the thus obtained cured sheet 3 overlying the carrier sheet 1.

The cured rubber sheet 3 and the carrier sheet 1 are then separated by peeling as is shown in Fig. 2(d). In this case, the relief stripes 2 are transferred to the cured rubber sheet 3 as embedded therein. It is a necessary condition that the bonding between the carrier sheet 1 and the relief stripes 2 and between the carrier sheet 1 and-ttie cured rubbery sheet 3 is not so strong that smooth peeling of the carrier sheet 1 and transfer of the relief stripes 2 are ensured.

The cured rubber sheet 3 freed from the carrier sheet 1 is then sliced together with the stripes 2 embedded therein in a plane substantially perpendicular to the longitudinal direction of the stripes 2 into pieces which are used as finished interconnectors shown in Fig. 4. The thickness of the individual pieces naturally is determined in accordance with the particualr use of the interconnectors.

It is optional that the cured rubber sheet 3 with the embedded stripes 2 is provided before slicing with a lining sheet 4 of an electrically insulating rubbery elastomer which is preferably of the same kind as the rubber sheet 3 so that each of the stripes 2 has exposed surfaces only on the opposite cross sections obtained by slicing as is shown in Fig. 5; this may be desirable for particular uses of the interconnector.

In the above described embodiment of the method, the finished interconnector has a plurality of contacting elements, i.e. the segments of the stripes 2 formed of the electrically conductive material, arranged only in a single row as is shown in Fig. 4 or Fig. 5. When an interconnector having the contacting elements arranged in rows and columns is desired, the above described procedure is somewhat modified. Thus, a plurality of the cured rubber sheets 3, each having the stripes 2 embedded therein, are overlaid and bonded together back to face one on the other by use of a suitable adhesive agent in such a manner that the stripes 2 on each of the sheets 3 run in the same direction to give an integrated block 6 shown in Fig. 6. The integrated block 6 shown in Fig. 6 is provided with a covering sheet 5 to cover the end surface on which the stripes 2 are exposed.The thus obtained integrated block 6 is then sliced in a plane substantially perpendicular to the longitudinal direction of the stripes 2 and, in most cases, substantially perpendicular to the plane of the sheets to give a sheet-like interconnector shown in Fig. 7 in which the contacting elements, i.e. the segments of the stripes 2, are arranged in rows and columns.

It is of course optional that the cured rubber sheets 3 have the stripes 2 of the electrically conductive material with different pitches P, widths W and heights H so that the finished sheet-like interconnector has the contacting elements arranged in an irregular distribution according to need.

It is further optional in the preparation of the above described integrated block 6 that the rubbery elastomer sheet 3 with the stripes 2 embedded therein shown in Fig. 2(c) is freed from the carrier sheet 1 by peeling before curing and a plurality of the thus obtained uncured rubbery elastomer sheet 3 with the embedded stripes 2 are overlaid one on the other in the same manner as with the cured sheets 3 followed by subsequent simultaneous bonding and curing with heat and pressure into the integrated block 6. A strong bonding is obtained in this procedure even without any adhesive agents.

As will be understood from the above description, the illustrated method provides a .novel and very efficient means for manufacturing interconnectors made of a rubbery elastomer in a sequence of simplified steps. Furthermore, the interconnectors manufactured in accordance with the method can have the contacting elements arranged with a very fine pitch of 1 mm or smaller and with a very high precision at a very low production cost so that great practical advantages are obtained with the method. For example, a sheet-like interconnector as shown in Fig. 7 may be used as spread between two circuit units covering whole surfaces thereof with punched void areas in a form of a hole or notch corresponding to the particular portions on the circuit units where the presence of an intervening interconnector is undesirable.

Claims

1. A method for manufacturing an interconnector of press-contact type made of a rubber elastomer which comprises the successive steps of (a) providing a carrier sheet on one surface thereof with relief stripes formed of an electrically conductive material, (b) overlaying the carrier sheet on the surface having the relief stripes with a sheet of an uncured electrically insulating rubbery elastomer, (c) bonding the carrier sheet and the uncured rubbery elastomer sheet by pressing whereby the relief stripes of the electrically conductive material sink into the uncured rubbery elastomer sheet, (d) subjecting the uncured rubbery elastomer sheet to curing whereby the relief stripes are adhesively bonded to the cured rubbery elastomer sheet, (e) separating the carrier sheet from the cured rubbery elastomer sheet so that the embedded stripes are transferred to the cured rubbery elastomer sheet, and (f) slicing the cured rubbery elastomer sheet having the stripes embedded therein in a plane substantially perpendicular to the longitudinal direction of the stripes.

2. A method for manufacturing an interconnector of press-contact type made of a rubbery elastomer which comprises the successive steps of (a) providing a carrier sheet on one surface thereof with relief stripes formed of an electrically conductive material, (b) overlaying the carrier sheet on the surface having the relief stripes with a sheet of an uncured electrically insulating rubbery elastomer, (c) bonding the carrier sheet and the uncured rubbery elastomer sheet by pressing whereby the relief stripes of the electrically conductive material sink into the uncured rubbery elastomer sheet, (d) subjecting the uncured rubbery elastomer sheet to curing whereby the relief stripes are adhesively bonded to the cured rubbery elastomer sheet, (e) separating the carrier sheet from the cured rubbery elastomer sheet so that the embedded stripes are transferred to the cured rubbery elastomer sheet, (f) overlaying a plurality of the thus prepared cured rubbery elastomer sheets each having the stripes embedded therein one on the other in such a manner that the stripes on each of the sheets run in the same direction, (g) bonding the cured rubbery elastomer sheets into an integrated laminated body, and (h) slicing the integrated laminated body in a plane substantially prependicular to the longitudinal direction of the stripes.

3. A method for manufacturing an interconnector of press-contact type made of a rubbery elastomer which comprises the successive steps of (a) providing a carrier sheet on one surface thereof with relief stripes formed of an electrically conductive material, (b) overlaying the carrier sheet on the surface having the relief stripes with a sheet of an uncured electrically insulating rubbery elastomer, (c) bonding the carrier sheet and the uncured rubbery elastomer sheet by pressing whereby the relief stripes of the electrically conducting material sink into the uncured rubbery elastomer sheet and bonded thereto, (d) separating the carrier sheet from the uncured rubbery elastomer sheet having the stripes as embedded therein, (e) overlaying a plurality of the uncured rubbery elastomer sheets each having the stripes embedded therein one on the other in such a manner that the stripes on each of the sheets run in the same direction, (f) subjecting the uncured rubbery elastomer sheets thus overlaid one on the other to bonding and curing into an integrated laminated body, and (g) slicing the integrated laminated body in a plane substantially perpendicular to the longitudinal direction of the stripes.

4. A method according to Claim 1,2 or 3, substantially as hereinbefore described with reference to the drawings.

5. An interconnector of press-contact type when made by a method according to any preceding claim.