GB2058652A - Method of making an electrical connector - Google Patents

Abstract

A method of making an electrical connector of a rubbery material, for example, in the form of an elongated rod-shaped body, and provided on the surface thereof with parallel strip-like electroconductive paths (51) running perpendicularly to the longitudinal direction of the rod-shaped body, comprises preparing a composite sheet-like assembly which is a stratified sheet of an insulating carrier film (52) and provided with a set of parallel electroconductive paths (51) on one surface thereof and an uncured rubber sheet (53); placing the composite sheet-like assembly between the upper and lower mould parts (11, 12) of a metal mould (1) having groove-like cavities (2a, 2b) in such a manner that the parallel electroconductive paths of the composite sheet perpendicularly cross the groove-like cavities (2a, 2b) and the composite sheet stretches beyond the peripheries of the cavities, and then compression moulding the composite sheet by moving the upper and lower mould parts (11, 12) together with an appropriate pressure with heating so as that the carrier film (52) is deformed to comply with the surface of one of the cavities 2b while the uncured rubber of the sheet (53) is plastically deformed and cured to fill the hollow space between the cavities. <IMAGE>

Description

SPECIFICATION Method of making an electrical connector The present invention relates to a method of making an electrical connector of elastomeric material which has at least one set of electroconductive paths on its surface and is used for making electrical connections of electronic circuit boards. The connector is generally elongated, for example, rod-shaped.

In recent years, there have been widely used electrical connectors, or so-called interconnectors, for electrically connecting various kinds of electronic circuit boards, for example for connecting a display unit such as a liquid crystal display unit an electrochromic display unit, a lightemitting diode or other display unit to a circuit board for driving the display unit. Most conventional connectors are in the form of a rod made of an elastomeric material provided with a set of parallel strip-like electroconductive paths on the surface formed of an electroconductive material and lying perpendicularly to the iongitudinal direction of the rod.Connectors of this type are sandwiched between arrays of contact terminals on each of the circuit boards with an appropriate pressure so that electric condition is obtained only between the pairs of contact terminals on the circuit boards oppositely positioned on the opposite sides of the connector.

Conventional methods for the manufacture of connectors of the above type are as follows:- For example, parallel, strip-like electroconductive paths are formed with an electroconductive resinous or rubbery material on one surface of an electrically insulating flexible film or sheet and the sheet is laminated or sandwiched with one or two uncured rubber sheets which are integrated by curing under pressure. This is followed by cutting of the integrated body, in a plane approximately perpendicular to the direction of the parallel electroconductive paths, into rod-like bodies.

Alternatively, a so-called transfer sheet provided with a pattern of parallel strips by printing with an electroconductive ink or paint is placed in a groove-like cavity having a rectangular cross section of a metal mould suitable for compression moulding, followed by placing of a rod-shaped body of an uncured rubber thereon.

After compression moulding and curing of the uncured rubber in the metal mould, the cured rubber body having the transfer sheet is taken out of the metal mould and the transfer sheet is removed by peeling so that the electroconductive strip pattern is integrally transferred on to the surface of the rod-like rubber body.

Both of the above described methods have disadvantages in that although they are suitable for the preparation of rod-shaped connectors having a rectangular cross section, rod-shaped connectors having an irregular cross section cannot in practice be obtained by the methods.

Further, the former method is not suitable when a connector having high dimensional accuracy is required because the rubber sheet is unavoidably subject to compressive deformation. The latter method is somewhat burdensome because the rod-shaped core material of the connector must be shaped in advance from uncured rubber. All in all therefore, the above described conventional methods are not always satisfactory for the industrial manufacture of rod-shaped connectors of the type described.

The object of the present invention is to provide an improved method for the manufacture of an electrical connector of an elastomeric material free from the above described problems and inconvenience in the prior art methods.

The method of the present invention for making an electrical connector of an elastomeric material having at least one set of electroconductive paths on a surface thereof, the paths extending side by side, comprises the steps of: (a) bonding a film, which is provided on one face thereof with at least one set of electroconductive paths extending side by side, to a sheet of an uncured rubber to form a composite sheet-like body;; (b) moulding the composite sheet-like body by compression and heating in a metal mould comprising a first mould part provided with a cavity in a moulding surface therefor and a second mould part of such a shape that a hollow mould space is formed with the cavity in the first mould part when the first and second mould parts are moved together so that the film provided with the electroconductive paths is deformed to be in compliance with the surface of the cavity in the first mould part and the uncured rubber of the composite sheet-like body is plastically deformed to fill the hollow space and is heat-cured into a cured body; and, (c) removing the cured body from the metal mould.

Preferably, the connector is of elongated rod shape and the paths extend substantially parallel with each other in a direction substantially perpendicular to the longitudinal direction of the connector and the lower mould, and the mould parts are both provided with a linearly extending groove-like cavity having a cross section such that the cavities in the first mould part and the second mould part form the hollow space when the lower mould and the upper mould are joined together, the composite sheet-like body being placed between the mould parts in such a manner that the direction of the electroconductive paths is substantially perpendicular to the longitudinal direction of the linearly extending groove-like cavities and the composite sheet-like body stretches beyond the peripheries of the cavities.

Preferably also the mould is provided with a plurality of the cavities so that a number of connectors are obtained in one moulding operation and the individual connectors are connected to the neighbouring connectors by very thin marginal portions therebetween as a continuum so that all of the connectors can be taken out of the metal mould in one movement and can subsequently be divided by cutting the continuum into the individual connectors with great efficiency.

Some examples of methods in accordance with the invention will now be described with reference to the accompanying drawings, in which~ Figure 1 is a cross sectional view of a metal mould for moulding rod-like connectors by the method in accordance with the invention with a composite sheet-like body placed between lower and upper parts of the mould; Figures 2a to 2c are cross sections of composite sheet-like bodies having electroconductive paths in different positions on them; Figure 3 is a perspective view of a continuum of the rod-like connectors as moulded in the metal mould illustrated in Figure 1; Figures 4a and 4b are perspective views of typical examples of the rod-like connectors; Figures 5 to 9 are perspective views of further examples of rod-like connectors having irregular cross sections;; Figures 10 to 14 illustrate the different manners in which the rod-like connectors shown in Figures 5 to 9 are used for electrically connecting two circuit boards; Figures 1 5a and 1 5b are cross sectional views of metal moulds in which a projecting portion is provided in either one of lower and upper mould in parts; Figures 1 6a to 1 6c are perspective views of further examples of rod-like connectors moulded in metal moulds like those shown in Figures 1 5a and 1 5b: Figures 1 7a to 1 7c illustrate examples of patterns of electroconductive paths on composite sheet-like bodies; and, Figures 1 8a to 1 8c are perspective views of rubber connectors made from composite sheetlike bodies having electroconductive paths of the patterns shown in Figures 1 7a to 1 7c respectively.

The method of the present invention is applied most typically to the preparation of rod-shaped connectors having electroconductive paths extending perpendicularly to the longitudinal direction of the rod. The following description is therefore directed mainly to the making of such connectors although it can also be applied to the manufacture of connectors with paths which do not extend in this way.

The first step in the method in accordance with the invention is the preparation of the composite sheet-like body composed of an uncured rubber sheet and an electrically insulating film provided with strip or stripe-like parallel electroconductive paths on its surface. The latter film provided with strip-like electroconductive paths, hereinafter called a striped film, in turn is prepared as follows.

The material of the insulating film is not particularly limitative provided that the material has a sufficient mechanical strength and heat resistance. Suitable materials include, for example, films of rubbers or plastic resins such as polyimide resins, polyether resins, polyester resins and the like as well as woven or non-woven cloths impregnated with a thermosetting resin such as epoxy resins, unsaturated polyester resins, diallyl phthalate resins, triazine resins and the like with subsequent heat curing of the resin. The parallel stripe-like electroconductive paths are most conveniently formed by printing, e.g. by screen printing or offset printing, with an electroconductive ink or paint on the above insulating film followed by curing thereof. The electroconductive ink or paint is well known in the art and need not be described in detail here.

Alternatively, the striped sheet may be prepared by slicing an alternately stratified body formed of a plurality of insulating sheets and a plurality of electroconductive sheets in a plane perpendicular to the direction of stratification.

Further alternatively, the striped film is prepared by the technique of stripe-wise etching of a film provided with a metal foil adhesively bonded thereon or formed by vacuum deposition.

A method of stripe-wise vacuum deposition of a metal on an insulating film is also used with a suitable masking. Most simply, very narrow ribbons of an electroconductive material, e.g.

metal foil, are directly bonded in stripes on the surface of an insulating film by use of a suitable adhesive agent.

The uncured rubber sheet to be bonded with the striped film is made of a known rubbery material such as silicone rubbers, nitrile rubbers, chloroprene rubbers and the like and it is bonded with the striped film, preferably, by use of an adhesive agent and a coupling agent in order to obtain stronger bonding between them. In this case, the striped film may be bonded to the uncured rubber sheet either on the surface provided with the parallel stripe-like electroconductive paths so as that the electroconductive paths are embedded between them or on the reverse surface having no electroconductive paths so as that the electroconductive paths are exposed outwardly.

In the former case, the film supporting the parallel stripe-like electroconductive paths is peeled off after completion of shaping of the rodshaped connector and, if the film is kept as bonded until just before use of the connector, it may serve as a temporary protecting film of the connector surface.

The composite sheet-like body obtained in the above described manner is then shaped by compression molding in a metal mold. The metal mold used in the inventive method usually consists of an upper mold and a lower mold, optionally, with one or more of intermediate frames and each of them is provided with a linearly extending groove-like cavity engraved in the molding surface so that a hollow space is formed between the upper and lower molds having a cross section in conformity with the cross section of the desired connector when they are joined together for compression molding. Of course a plurality of such cavities may be provided in a metal mold so that a number of connectors may be molded in one shot to give better efficiency of production.The upper and/or the lower mold of the metal mold are provided with line protrusions, preferably, having acute-angled ridges along the peripheral lines of the cavities which act something like a thrusting blade so that the compression molding is effected with the upper and the lower molds joined together to leave very thin marginal portions around the periphery of the cavities.

The composite sheet-like body is placed on the cavity or cavities of the lower mold in such a manner that the direction of each of the stripes is substantially perpendicular to the longitudinal direction of the linearly extending cavity or cavities. It is also necessary that the composite sheet-like body is sufficiently large to be outstretched beyond the peripheries of the cavity so as that marginal portions extend between the upper and lower molds when they are joined together for compression molding. Compression molding of the composite sheet-like body is carried out by moving the upper and the lower molds together with an appropriate pressure and heating.The uncured rubber sheet of the composite sheet-like body is first plastically deformed to fill the hollow space formed by the cavities in the upper and lower molds and cured as such, retaining the cross section of the desired connector. In this case, the arrangement of the parallel electroconductive paths never becomes disordered as being supported by the insulating film of the striped film.

In the application of the pressure for compression molding, it is preferable that the thickness of the composite sheet-like body in the marginal portions around the cavities is very thin but the individual shaped bodies are never severed from each other by proper control of the pressure or by having suitably adjusted heights of the above mentioned line protrusions around the cavities.

This measure is advantageous because the shaped bodies after compression molding can be taken out of the metal mold as a continuum of the individual shaped bodies connected by the very thin marginal film portions surrounding each of the shaped bodies so that the time-consuming step of taking the shaped bodies, i.e. connectors, out of the metal mold piece by piece can be avoided. The thus obtained continuum is divided into the individual connectors by cutting and trimming, if necessary, after post-heating treatment to obtain complete curing of the rubber.

In the following, the method of the present invention is described in further detail with reference to the accompanying drawing.

FIG. 1 illustrates a cross section of a metal mold for compression molding used in practicing the method of the present invention. The metal mold 1 is composed of an upper mold 11 and a lower mold 12 and each of the upper mold 1 1 and lower mold 12 is provided with a plurality of linearly extending cavities 2a, 2a or 2b, 2b, respectively, engraved in the molding surfaces of the molds. The cross sections of the cavities 2a and 2b are such that linearly extending hollow spaces are formed by the opposedly positioned cavities 2a and 2b having cross sections in coincidence with the cross sections of the desired connectors molded with the metal mold 1 when the upper mold 11 and the lower mold 12 are joined together for compression.

In the metal mold 1 shown in FIG. 1, the upper mold 11 is provided with line protrusions 3 having acute-angled ridges surrounding the cavities 2a.

The upper mold 11 is also provided with a groove 4 which serves as an overflow escape of the uncured rubber stock when a composite sheet-like body is compressed between the upper mold 11 and the lower mold 12.

FIG. 2a to FIG. 2c each illustrate a cross sectional view of a composite sheet-like body 5 to be subjected to compression molding. The composite sheet-like body 5 shown in FIG. 2a is prepared by adhesively bonding a striped film 52 provided with parallel stripe-like electroconductive paths 51 on one surface thereof with an uncured rubber sheet 53 on the surface provided with the electroconductive paths 51 so that the electroconductive paths 51 sink into the uncured rubber sheet 53 to have coplanar surfaces with the latter.The composite sheet-like body 5 shown in FIG. 2b is, on the other hand, composed of the striped film 52 provided with the parallel stripelike electroconductive paths 51 on one surface thereof as bonded to the uncured rubber sheet 53 on the surface having no electroconductive paths so as that the electroconductive paths 51 are raised in relief on the surface of the film 52.

The composite sheet-like body 5 shown in FIG.

2c has a striped film prepared by slicing an alternately stratified body formed of a plurality of insulating sheets and a plurality of electroconductive sheets in a plane perpendicular to the direction of stratification.

FIG. 1 also shows a composite sheet-like body 5 of FIG. 2b placed between the upper mold 11 and the lower mold 12 with the electroconductive paths 51 facing the lower mold 12 in such a manner that the striped electroconductive paths 51 are substantially perpendicular to the longitudinal direction of the linearly extending cavities 2a or 2b and a single composite sheet-like body 5 covers all of the cavities 2a, 2a or 2b, 2b.

Compression molding is carried out by holding the upper mold 1 1 and the lower mold 12 together under an appropriate pressure with the composite sheet-like body 5 therebetween so that the uncured rubber sheet 53 is plastically deformed to fill the hollow spaces formed of the upper and lower cavities 2a and 2b, excess amount of the uncured rubber being excluded through the overflow escape 4, while the insulating film 52 is bent in contact with the surface of the cavity 2b of the lower mold 12 together with the electroconductive paths 51 thereon. In the application of the pressure for compression, the line protrusions 3 do not sever apart the composite sheet-like body 5 completely but very thin marginal film portions are left surrounding each of the shaped bodies, i.e.

connectors, filling the cavities.

After completion of compression molding under pressure and heating to cure the uncured rubber 53, the molded body is taken out of the metal mold 1 by separating the upper mold 11 and the lower mold 12 as a single continuum as is shown in FIG. 3 (upside down) composed of a number of the molded bodies, i.e. connectors, and the marginal portions surrounding each of them and connecting them with each other. It is of course optional that the pressure for compression is controlled and the height of the line protrusions 3 is adjusted so as that each of the molded bodies, i.e. connectors, is taken discretely out of the metal mold 1 piece by piece but the former described method of taking out as a single continuum is better in most cases from the working efficiency.

The single continuum shown in FIG. 3 is readily divided apart into the individual connectors, if desired, with trimming.

FIG. 4a and FIG. 4b each illustrate a perspective view of a typical connector prepared in accordance with the method of the present invention. The model shown in FIG. 4a is prepared with the composite sheet-like body 5 shown in FIG. 2b and the model shown in FIG. 4b is prepared with the composite sheet-like body 5 shown in FIG. 2a with subsequent removal of the film 52 so that the electroconductive paths 51 and the insulating rubber base 53 have coplanar surfaces.

FIG. 5 to FIG. 9 each illustrate a perspective view of a different model of the connectors 6 obtained by the inventive method. These connectors 6 may be slightly curved ones or in the form of a rectangular frame instead of a straight line by use of suitably engraved cavities in the metal mold.

FIG. 10 to FIG. 14 each illustrate the manner in which the connectors prepared by the inventive method is put to practical use for connecting two circuit boards. The connector shown in FIG. 5 is used in FIG. 10 and the connectors shown in FIG.

7 to FIG. 9 are used in FIG. 12 to FIG. 14, respectively. In each of these figures, the arrow mark indicates the direction of the pressing force with which the connector is contacted with the contact terminals on the circuit boards. In FIG. 10 and FIG. 12 to FIG. 14, the connectors are used for electrically connecting a display unit 7 such as a liquid crystal display unit, electrochromic display unit, light emitting diode or the like and a board 8 for driving circuit thereof. FIG. 1 1 illustrates a jig 9 provided with two female screw holes for mounting in bonding the connectors.

The above described method of the present invention is sufficiently effective in most cases for the preparation of rod-shaped connectors of rubbery materials having not only rectangular cross sections but also irregular cross sections with high dimensional accuracy in industrial quantities. A problem is left, however, depending on the irregularity of the cross sections that filling of the hollow spaces formed by the cavities in the metal mold with the uncured rubber of the composite sheet-like body sometimes does not reach the very corner, especially, when the cavities have acute-angled corners so that the molded bodies obtained with such a metal mold have dull edge lines or the density of the cured rubber is low at the corner portions.

The inventors have conducted investigations to solve the above problem and arrived at a conclusion that the problem is solved by improving the cross sectional forms of the cavities in the metal mold. The improved metal mold suitable for the inventive method is composed of a first mold, e.g. lower mold, provided with a linearly extending groove-like cavity while the other mold, e.g. upper mold, to be joined with the former is provided with a linearly extending protrusion to enter the cavity in the former mold. The compression molding of the composite sheet-like body is carried out in just a like manner as described before. The molded body prepared with such a metal mold has very uniform density over whole cross section by virtue of the protrusion in the upper mold acting to accelerate the plastic flow of the uncured rubber of the composite sheet-like body.

In the following, the inventive method with the above described improved metal mold is described in further detail with reference to the accompanying drawing.

FIG. 1 5a and FIG. 1 5b each illustrate a cross sectional view of a metal mold 1 consisting of a lower mold 12 provided with one or more of linearly extending groove-like cavities 20 and an upper mold 11 provided with a protrusion 30 projecting in the cavity 20 when the lower mold 12 and the upper mold 1 1 are joined together.

Line protrusions 20a and 30a are provided along the peripheral lines of the cavities 20 and the protrusions 30 of the lower mold 12 and the upper mold 11, respectively. An overflow escape 4 is provided in either one of the lower mold 12 and the upper mold 11, if necessary.

FIG. 1 6a to FIG. 1 6c each illustrate a perspective view of a rod-shaped connector having a set of parallel electro-conductive paths running perpendicularly to the longitudinal direction of the rod as prepared by use of the metal mold of the above described type having protrusions in the upper mold.

The principle of the inventive method is not limited to the preparation of straight solid rodshaped connectors but is also applicable to the preparation of more complicated, for example frame-like or annular, connectors. In this case, the striped film for the composite sheet-like body is provided, instead of a single set of parallel electroconductive paths, with two sets or more of parallel electroconductive paths or radially arranged electro-conductive paths according to the shapes of the desired finished connectors. FIG.

1 7a to FIG. 1 7c each illustrate a plan view of such a striped film and FIG. 1 8a to FIG. 1 8c each illustrate a perspective view of the connector prepared with the striped film of FIG. 1 7a to FIG.

1 7c, respectively.

The connectors shown by FIG. 1 8a to FIG. 1 8c may be prepared of course piece by piece by use of a composite sheet-like body having a single unit pattern of the electroconductive paths as shown in FIG. 1 7a to FIG. 1 7c, respectively. It is also possible to manufacture such connectors continuously with a continuous length composite sheet-like body provided with repetition of the unit patterns of the electroconductive paths of FIG.

1 7a to FIG. 1 7c, which continuous length sheet is supplied between a pair of rotating rollers provided with a cavity or cavities or a protrusion or protrusions on the surface of the rollers acting as an upper mold and a lower mold, respectively.

Although not shown in the figures, it is optional or advisable that each of the connectors is provided with one or more of pins or pits in positions not to interfere with the electroconductive paths for positioning by fitting in the pits or pins provided in the circuit boards to be connected with the connector so as that the working efficiency in mounting of the connectors in assembling electronic instruments can be improved.

Claims (4)

1. A method of making an electrical connector of an elastomeric material having at least one set of electroconductive paths on a surface thereof, the paths extending side by side, the method comprising the steps of~ (a) bonding a film, which is provided on one face thereof with at least one set of electroconductive paths extending side by side, to a sheet of an uncured rubber to form a composite sheet-like body:: (b) moulding the composite sheet-like body by compression and heating in a metal mould comprising a first mould part provided with a cavity in a moulding surface thereof and a second mould part of such a shape that a hollow mould space is formed with the cavity in the first mould part when the first and second mould parts are moved together so that the film provided with the electroconductive paths is deformed to be in compliance with the surface of the cavity in the first mould part and the uncured rubber of the composite sheet-like body is plastically deformed to fill the hollow space and is heat-cured into a cured body; and, (c) removing the cured body from the metal mould.

2. A method according to claim 1, in which the connector is of elongated rod shape and the paths extend substantially parallel with each other in a direction substantially perpendicular to the longitudinal direction of the connector and the mould parts are both provided with a linearly extending groove-like cavity having a cross section such that the cavities in the first mould part and the second mould part form the hollow space when the lower mould and the upper mould are joined together, the composite sheet-like body being placed between the mould parts in such a manner that the direction of the electroconductive paths is substantially perpendicular to the longitudinal direction of the linearly extending groove-like cavities and the composite sheet-like body stretches beyond the peripheries of the cavities.

3. A method according to claim 1 or claim 2, in which the face of the film on which the paths are provided is bonded to the sheet and after removal of the cured body from the mould, the film is removed to leave the paths on the surface of the body.

4. A method according to claim 1, substantially as described with reference to Figures 1 to 3 and any one of Figures 4a to 9 and 1 6a to 1 8c, or Figures 1 5a or 1 Sb, of the accompanying drawings.