US3701726A

US3701726A - Support assembly for electrolytic deposition on contact element

Info

Publication number: US3701726A
Application number: US97131A
Authority: US
Inventors: Bernard Andre Laboue
Original assignee: Societe Industrielle Honeywell Bull
Current assignee: Bull SA
Priority date: 1969-12-17
Filing date: 1970-12-11
Publication date: 1972-10-31
Anticipated expiration: 1989-10-31
Also published as: DE2061572C2; GB1335221A; JPS5128340B1; NL7016923A; DE2061572A1; FR2071087A5; NL170650C; NL170650B

Abstract

A support providing for the selective electroplating of the contact points of a pair of contact elements having arch-shaped portions, each element having a contact point at each extremity of the arch-shape portions thereof, the two contact elements being electroplated with the arch-shaped portions thereof mutually opposed; whein an insulated spacing member extends between the two arch-shaped portions to protect such portions from the electroplating solution, but wherein the contact points extend beyond the spacing member; wherein a flat electrode is supported by the spacing member and extends between each opposed pair of contact points of the contact elements, and wherein when the support is immersed in an electrolytic solution, metal is selectively deposited on the contact points opposite to the electrode.

Description

1972 a. A. LABOUE SUPPORT ASSEMBLY FOR ELECTROLYTIC DEPOSITION ON CONTACT ELEMENT Filed Dec. 11. 1970 6 Sheets-Sheet 2 0a. 31, 1912 A, LAB UE v 3,701,726

SUPPORT ASSEMBLY FOR ELECTROLYTIC DEPOSITION ON CONTACT ELEMENT Filed Dec. 11. 1970 6 Sheets-Sheet 5 W will W I IN ENTOR BUM HTML; 2M

Oct. 31, 1972 LABQUE 3,701,726

SUPPORT ASSEMBLY FOR ELECTROLYTIC DEPOSITION ON CONTACT ELEMENT Filed Dec. 11, 1970 6 Sheets-Sheet 4 NTOR btf M I dklwb Oct. 31,1972 5 LABQUE 3,701,726

7 SUPPORT ASSEMBLY FOR ELECTROLYTIC DEPOSITION ON CONTACT ELEMENT Filed D60. 11, 1970 6 Sheets-Sheet 5 INVENTOR (5 W1 W4 MM SUPPORT A MBLY FOR ELECTROL c A. mous 3,701,726

DEPOSITION ON CONTACT ELEME Filed D80. 11, 1970 6 Sheets-Sheet 6 IN ENTOR BUM ANAL; ATM

United States Patent O SUPPORT ASSEMBLY FOR ELECTROLYTIC DEPOSITION ON CONTACT ELEMENT Bernard Andre Laboue, Goussainville, France, assignor to Socit Industrielle Honeywell Bull, Paris, France Filed Dec. 11, 1970, Ser. No. 97,131

Claims priority, application France, Dec. 17, 1969,

Int. Cl. C23b 5/70 US. Cl. 204-297 R 14 Claims ABSTRACT OF THE DISCLOSURE A support providing for the selective electroplating of the contact points of a pair of contact elements having arch-shaped portions, each element having a contact point at each extremity of the arch-shaped portions thereof, the two contact elements being electroplated with the archshaped portions thereof mutually opposed; whein an insulated spacing member extends between the two archshaped portions to protect such portions from the electroplating solution, but wherein the contact points extend beyond the spacing member; wherein a fiat electrode is supported by the spacing member and extends between each opposed pair of contact points of the contact elements, and wherein when the support is immersed in an electrolytic solution, metal is selectively deposited on the contact points opposite to the electrode.

BACKGROUND OF THE INVENTION The present invention concerns a support assembly especially suitable to enable effecting an electrolytic deposit of a precious metal selectively on the contact points of the contact elements of electric connectors and more particularly for some contact elements of connectors adapted for receiving printed circuit boards.

Some connectors for printed circuit boards comprise in general at least one row of contact elements provided with flexible arms presenting contact surfaces called contact points because of their small area, and disposed for engaging in contact, under predetermined pressure, with other contact surfaces arranged along an edge of a printed circuit board when the latter is introduced into a connector. Because of their particular form, the flexible arms of the contact elements are frequently termed lyres.

One connector of this type has been described more particularly in the US. Pat. No. 3,118,716, granted Jan. 21, 1964. A connector of the same type has been similarly described in the US. Pat. No. 3,543,226, granted Nov. 24, 1970.

The introduction of a printed circuit board into a connector of this type is accompanied by a rubbing between the contact pads of the printed circuit board and the contact points of the lyres. This rubbing has a wiping eifect on the surfaces brought into contact and contributes to assuring a good electrical contact, provided, however, that such surfaces have not suffered meanwhile chemical deterioration such as oxidation or sulfurization under the action of atmospheric or other agents.

For remedying this disadvantage, it is current practice to coat the contact surfaces with a metal that is a good conductor of electricity and is unoxidizable for assuring 3,701,726 Patented Oct. 31, 1972 'ice a prolonged use of the apparatus with complete reliability.

The metal employed for this purpose is frequently of gold or an alloy of gold or another precious metal, of which the cost is always relatively very great. A layer of this metal, of sufficient thickness, must be electrolytically deposited on at least the contact points of the contact elements. However, in the course of this operation a substantial quantity of the metal is also deposited on other portions of the elements immersed in the electrolysis bath, thereby entailing an unnecessary consumption of the precision metal.

For remedying this disadvantage it has been proposed to protect with an insulating varnish the other portions than the points of contact which are necessarily found immersed in the tank, but because of supplementary manipulations which become necessary, this process is evidently relatively costly.

It is known that in an electroplating installation, the thickness of metal deposited on a particular surface is greater the closer is the surface to an anode. In most instances, the differences in thickness of the deposit obtained in this way are considered to be a disadvantage, which may be successfully remedied in part, either by multiplying the number of anodes or by modifying the relative position of the anodes in relation to the objects to be treated in the course of the operation.

SUMMARY OF THE INVENTION The present invention relates to a support assembly especially adapted for taking advantage of the pecularity pointed out above under particularly advantageous conditions with the object of obtaining directly by electrolysis a deposit of precious metal, of a predetermined thickness and selectively localized in desired locations, in this instance on the contact points of the lyres of contact elements, whereas the thickness of the metal deposited on the other immersed portions of these contact elements is practically null or negligible, permitting the realization of a significant economy of precious metal. The invention concerns a support assembly for effecting an electrolytic deposit of a precious metal selectively on the contact points of a plurality of pairs of contact lyres of conducting metal, these lyres being joined by a thin strip where they are disposed in such a way that, in each pair of lyres, two prominent contact points are separated by a certain distance and disposed symmetrically in relation to an axis of symmetry of the pair of lyres, the lyres being symmetrically opposed. The support assembly comprises a support body permitting the mounting and stacking of a predetermined number of strips of lyres. The support body comprises a wall of insulating material having at right angles to each of the axes of symmetry a support finger of form adapted to the two opposed lyres. A conductive electrode forming an anode is incorporated in each support finger and has a length and a thickness such that each of the two extremities of this electrode is found opposite to, and at a relatively small distance from, a contact point of the corresponding lyre, in order to concentrate on the such contact point a deposit of precious metal at the time of the electrolysis process.

BRIEF DESCRIPTION OF THE DRAWING The invention will be described with reference to the accompanying drawing, wherein:

FIG. 1 is a sectional view of a portion of a connector described in the above-mentioned US. Pat. No. 3,543,226;

FIG. 2 shows a portion of a strip of contact lyres cutout for a connector of the type shown in FIG. 1;

FIG. 3 shows a portion of a strip of contact lyres for a connector of the type which has been described in the above-mentioned US. Pat. No. 3,118,716;

FIG. 4 is a sectional view of a portion of a support assembly, taken on the section 4--4 of FIG. 9;

FIG. 5 shows separately different parts of the support assembly of FIG. 4;

FIG. 6 is a sectional view, in large scale, of a support assembly, taken on section 6-6 of FIG. 4;

FIG. 7 shows separately a removable element of the support block for the lyres;

FIG. 8 is a sectional view of a support assembly, taken on section 8-8 of FIG. 6; and

FIG. 9 is a plan view of several support assemblies placed in a movable frame disposed above an electrolysis tank.

DESCRIPTION OF THE PREFERRED EMBODIMENT The connector shown partly in section in FIG. 1 comprises a connector body 1 of molded electrically insulating material and two rows of contact elements. The upper row comprises contact elements A1, A2, A3, and the lower row comprises. elements B1, B2, B3, Each contact element comprises a flexible portion BF, prolonged at one end thereof by a wedge-shaped part C, which is introduced by force into a socket of appropriate shape arranged in the connector body. The portion BF is prolonged v.at the other end thereof by a flexible curved portion PR which provides two contact points CT1 and GT2. Contact points CT1 and CTZ are disposed for engaging in contact with and exerting predetermined pressure respectively at two points with a contact pad PC of a printedcircuit board 3, engaged in the connector. The portions BF and PR of a contact element form together that which has been termed a contact lyre. The part C is prolonged toward the exterior of the connector body by a rectilinear part Q, termed a lug.

In the, connector,;a contact element B1 is disposed symmetrically in relation to the contact element A1 for engaging in contact with a contact pad that is disposed on the other surface of the printed circuit board.

The contact elements shown in FIG. 2 comprise only a single lyre each, and are obtained by cutting from a strip of metal. However, also shown in this figure are connecting ribs 4, which join together the contact elements, particularly for the operation of gilding the contact points. These connecting ribs are separated from the contact elements, for example by cutting, before proceeding to. the mounting, of the contact elements into a connector body. In a strip of contact elements so shaped the lyres are disposed in pairs, the lyres of a pair being symmetrical in relation to an axis of symmetry 5. These axes 5 are separated to maintain a particular spacing between the lyres of two adjacent pairs.

In a connector of the type described in the first patent cited previously herein, each of the contact elements 8, FIG. 3, comprise twocontact lyres L10 and L20, which are joined to a single lug and are disposed symmetrically in the same plane relative to an axis 5D. With this second arrangement, two contact pads on opposite surfaces of the same printed circuit board are electrically connected together by the, contact points CT of the portions 7A and 7B of the lyres of the same contact element.

This invention concerns a support assembly presenting particular arrangements for permitting the depositing of a precious metal only on the contact points of contact elements, as will be described hereinafter. This support can receive equally wellstrips of contact lyres analogous to those represented by the examples of FIGS. 2 and 3.

The support assembly proper comprises a vertical support wall 10 of insulating material, FIG. 5, which is provided with

support fingers

11A, 11B, 11F, FIG. 4. The spacing between these support fingers corresponds, FIGS. 4 and 7, to the spacing of the axes of symmetry 5 of the contact lyres as they are disposed along the cutout strips. The length of the support fingers is adapted for the fingers to be able to receive a stack of a predetermined number of strips comprising preferably, contact elements of the same shape. These strips are pressed together by means of a removable cover 13 to form a block, BL, FIGS. 5, 6 and 8.

In the example represented, wall is formed of a plurality of removable support blocks 10A, 10B, 10C, 10D, assembled together by means of assemblage bars 17 and 18, FIGS. 5 and 6, which are electrically connected together by means of screws. These bars are further connected by any suitable means to the terminal of negative polarity (cathode) of a source of electric current. Through the assembling bars, the strips of lyres pressed together in the support are electrically connected to the negative terminal of the current source. The removable cover 13 of the support is similarly formed of an assemblage of removable insulating

blocks

13A, 13B, 13C, 13D, FIGS. 4, 5, -6 and 8, assembled together by means of conductive bars, 20 and 21, FIGS. 4, 5 and 6. With a stack of strips BL mounted on support fingers '11A, 11B, 11C the lower portion of support wall 10 is engaged in a U-shaped piece 14, which extends along the length of the support, FIG. 4. The cover 13 is similarly mounted on the support fingers and its lower portion engaged in U-shaped piece 14. The cover 13 and the support wall are then forced toward each other by means of clamps 15 for locking the stack of strips in the support.

FIG. 7 shows separately a removable support block 10C,

apart from a support assembly. This block is provided with two

support fingers

11E and 11F, similarly visible in FIGS. 4, 7 and 8. Each finger is provided with a fiat anode, such as anode 23 of finger (11B and anode 24 of finger 11F. Each anode is formed of a strip of platinum iridium, each such strip being soldered to a copper lead 25 which, similarly to the strip, is partly embedded in the mass of insulating material forming the support block. FIG. 7 shows, by dashed lines, the outlines of a portion of a stack of strips of lyres engaged on the support fingers of a support block 10C, in order to show the positions of the extremities ANl, AN2, AN3, and AN4 of

anodes

23 and 24 in relation to the contact points CT of the lyres.

In the example considered, the distance between the surface of the extremities of the anodes and the surfaces of the contact points CT of the lyres is about 0.3 to 0.4 millimeter. The thickness of each support finger, such as fingers 11B and 11 F, is such that when the strips of lyres are engaged by force on these fingers, the separation of the lower and upper contact points CT is the same as when a printed circuit board is plugged into a connector.

The assemblage constituting support wall 10 is attached to an upper insulating plate 26 through the intermediary of two insulating

uprights

27 and 28, each aflixed respectively at one end thereof to the upper plate, FIGS. 4, 5 and 9, and at the other end thereof to conductive bar 17, FIGS. 5, 6 and 9. Upper plate 26 is provided toward each of its ends with contact plates 29A and 29B, FIGS. 4, 5 and 9, which in turn, are provided with contact plugs 30. Contact plate 29A is electrically connected through a conductor 31, FIGS. 4, 5 and 6, to leads 25 of the removable support blocks constituting wall 10, whereas contact plate 293 is electrically connected, FIG. 5, through a conductor 32 to conductive bar 17. The support blocks and the cover blocks are provided respectively with

openings

34, 35, 36 and 37, each presenting a corresponding funnelshaped portion, which openings are disposed for assisting providing an intense circulation of the electrolyte around the anodes when a fabrication support is moved in an electrolysis tank 40.

FIG. 9 is a plan view of an electrolytic apparatus comprising six support assemblies emplaced in a movable support frame 41. Frame 41 is provided with insulating support plates 42 and 43. Insulating support plate 42 is provided with a contact bus 44, FIGS. 4 and 9, which is connected to the positive terminal of the current source. On this bus rest the contact plugs 30 of contact plates 29A, which are electrically connected through conductor 31 to the anodes of the supports. A contact bus 45 of insulating plate 43 is connected to the negative terminal of the current source and receives the contact plugs of contact plates 29B, which are electrically connected through conductors 32 to the strips of lyres which are stacked in each fabrication support. The upper plates of the fabrication supports are positioned in movable frame 41 by means of pins 47, which are affixed to insulating plates 42 and 43.

The upper plate of each support assembly is engaged at one extremity under a flange 48 of support frame 41, FIG. 4, in order to prevent the rocking of the support assemblies in the movable frame when the latter is moved longitudinally along the top of tank 40. FIG. 4 shows that the upper portion of tank 40 supports rollers 50, which are engaged in channels 51 provided on the lower face of two opposite edges of the movable frame. Channels 51 are disposed for permitting an oscillatory longitudinal movement of the frame along the top of the .tank in the direction of arrows M1 and M2, FIGS. 6 and 9, under the action of a crank and rod mechanism 53, which is driven by a motor 52.

FIGS. 4 and 6 show that the tank is provided internally with stationary partitions 54 disposed on both sides of each support assembly in order to inhibit the electrolyte from moving in the tank when the support assemblies are moved, and in order to intensify the movement of the electrolyte around the anodes when they are moved. One installation providing characteristics analogous to those which have been described permits, using a gold acid bath with cobalt, maintained at a temperature about 30 centigrade and for a current density of 2.4 amperes per square decimeter, of obtaining in ten minutes a deposit of gold localized at the level of the contact points of the lyres. The minimum thickness of such deposit is 1.5 microns and the deposit presents a Vickers hardness of about 180.

The sectional view of FIG. 8 is taken on the section 8-8 of FIG. 6 at substantially the level of the contact points CT disposed on each side of the flat anodes 23 and- 24. The metal is deposited along paths extending over the entire thickness of the stack of lyres. The metal deposited is sufliciently thin and sufiiciently adherent to permit subsequently separating the strips of lyres, one from the other, without the danger of tearing away the metal deposited on each contact.

In order to avoid favoring the formation of a deposit of metal on the extreme surfaces of a stack of lyres, FIG. 8 shows that the anodes are slightly narrower than the total thickness of the stack of lyres. With such an arrangement, the quantity of gold deposited on the lyres outside of the contact points is practically negligible, or null. The weight of precious metal deposited on each contact point is normally less than 0.4 milligram, which permits obtaining a particularly significant reduction in cost.

It is evident that the arrangements which have been described for illustrating one application of the invention are not limitations and that modifications and adaptations can be provided for a support assembly according to the circumstances and the applications without departing from the heart of the invention. Thus, the contact elements treated in the support can present parts cutout and stamped or be formed by bending conductive wires, according to the type of connector.

What is claimed is:

1. In an electrolytic apparatus adapted for effecting electrolytic deposits selectively on flat conductive lyre arranged in interconnected opposed pairs and each lyre having a curved portion defining two prominent contact points for receiving the electrolytic deposits; a support assembly comprising a vertical wall formed on an electrical insulating material, insulating support means projecting from said wall for receiving pairs of lyres in stacked relation thereon parallel to said wall and with contact points of each pair of lyres in predetermined spaced apart opposed positions, said support means being in the form of a finger projecting from said wall generally at right angles thereto, a contact plate carried by said wall spaced from said finger for engaging lyres mounted on said finger, and an elongated conductive anode partly embedded in said finger with said anode extending substantially parallel to said wall and projecting at opposite ends from said finger, each opposite end portion of said anode being aligned with the space between the predetermined spaced apart positions of a pair of contact points and in immediate proximity thereto in order to concentrate a metal deposit at said predetermined spaced apart positions during electrolytic deposition.

2. The support assembly of claim l further including means for connecting said contact plate to one terminal of a source of electroplating current and means for connecting said anode to the other terminal of said source.

3. The support assembly of claim 1 together with a removable cover opposing said wall and cooperable with said wall to clamp lyres to be coated therebetween, said wall and said cover having aligned opening means therethrough aligned with said anode end portions for eflecting circulation of electrolyte around said anode.

4. The support assembly of claim 3 together with drive means connected to said wall for .imparting to said support assembly an oscillatory movement during the process of deposition to circulate electrolyte through said opening means.

5. The support assembly of claim 4, wherein there are a plurality of said anodes, said anodes are of metal insoluble in said electrolyte and are connected together by conductors embedded in the body of said support for coupling to one terminal of a source of voltage, and wherein said support wall and said cover are provided with means for connecting said stack of strips of lyres to the other terminal of said voltage source. 1 l

6. The support assembly of claim 3 together with upper and lower clamp means for clamping said cover relative to said wall with lyres to be plated clamped therebetween.

7. The support assembly of claim 6 wherein said wall and said cover have remotely disposed conductor bars, said cover having a contact plate opposing said wall contact plate, means electrically connecting said contact plates to respective conductor bars, and said upper clamp means including an electrical conductor contacting and electrically connecting said conductor bars.

8. The support assembly of claim 1 wherein said wall includes a support bar, a plurality of separate support blocks, and means separately securing each support block to said support bar, and each support block having at least one of said fingers.

9. The support assembly of claim 1 wherein said anode projects from said wall a distance generally corresponding to the predetermined thickness of a stack of lyres to be carried by said support assembly.

10. The support assembly of claim 1 wherein said anode projects from said wall a distance generally corresponding to the predetermined thickness of a stack of lyres to be carried by said support assembly with said anode being of a lesser thickness than said predetermined thickness so as to be recessed.

11. The support assembly of claim 1 wherein each extremity of said anode is spaced from an adjacent one of said predetermined lyre contact point positions between 0.3 and 0.4 millimeters.

12. The. support assembly of claim 1 wherein said finger has a vertical extent and has vertical sides configurated for interlocking engagement with lyres to be mounted thereon for accurately positioning lyre contact points of said predetermined spaced apart positions.

13. The support assembly of claim 1 wherein said predetermined spaced apart positions for lyre contacts correspond to normal operative positions thereof.

14. The support assembly of claim '1 wherein said electrolytic apparatus includes means adapted to hold an electrolytic bath, and a movable support frame supporting said vwall for movement in said electrolyticibath.

References Cited UNITED STATES PATENTS JOHN H. MACK, Primary Examiner 0 R. J. FAY, Assistant Eiiaminer I US. Cl, X.R. 204 222