WO1987004568A1

WO1987004568A1 - Electrical circuit board interconnect

Info

Publication number: WO1987004568A1
Application number: PCT/US1987/000104
Authority: WO
Inventors: Mark S. Zifcak; Bruce G. Kosa; Scott S. Simpson; Herman B. Gordon; Richard C. Berry; Jeffrey B. Otto; Richard T. Traskos; Claudette M. Hoffman
Original assignee: Rogers Corporation
Priority date: 1986-01-15
Filing date: 1987-01-15
Publication date: 1987-07-30
Also published as: EP0255541A4; KR880701027A; EP0255541A1

Abstract

Area array connector device (12) for providing electrical interconnection from contacts on a first printed circuit board surface (15) to corresponding contacts on a second opposed surface (17) consists of an electrically nonconductive support member (13) disposed between opposed board surfaces, the support member having apertures therethrough in regions of the support member generally corresponding to alignment of corresponding opposed pairs of contacts (34, 36), and electrically conductive metallic interconnect members (22) extending in elastomeric material in the regions. The metallic interconnect members extend through the elastomer, and have end surfaces (26, 28) exposed for metal-to-metal, electricity-conductive contact with the contacts, with total resistance between contacts less than about 25 milli-ohms. The member end surfaces deflect under pressure and are restored upon release of pressure, at least in part by the restorative effect of the elastomer. Preferably, the interconnect member is bodily-rotatable.

Description

ELECTRICAL CIRCUIT BOARD INTERCONNECT

This invention relates to devices for interconnecting contact pads of opposed circuit' board surfaces.

Electrical interconnection between opposed circuits has, in the past, been provided by pin-and-socket engagement, e.g., as shown in Welu U.S. 4,249,787. It has also been known to provide interconnection via resilient conductors disposed in matrixes, including of foam or elastomer, e.g., as shown in Lamp U.S. 4,003,621, Luttmer U.S. 3,795,037, Sado

U.S. 4,295,700, Cherian et al. U.S. 4,161,346 and U.S. 4,199,209, and Kashiro et al. U.S. 4,209,841. Others have suggested conductors of resilient material filled with conductive particles, fibers or elongated elements, e.g., as shown in Takashi et al. U.S. 4,449,774, Ponn U.S. 4,008,300 and Koptelin U.S.S.R. 544,028. It has also been suggested to employ connection devices consisting of a line of conductor sheets supported in a housing on elastically deformable rolls extending the length of the housing, as shown in Bonnefoy U.S. 4,445,735.

The objectives of the present invention include providing a connector arrangement having improvement in one or more of the following features: reduction of total resistance between interconnected pairs of contact pads, consistency of contact stresses during repeated connector compression/decompression cycles, minimal deformation of the connector element, simplicity of design, predictability of the effect of temperature and time on performance, and contact pad wiping during compression. Summary of the Invention The invention relates to an area array connector device for providing electrical interconnection from a large plurality of first contact pads on a first printed circuit board surface to a

5 corresponding large plurality of second contact pads on a second opposed printed circuit board surface. The connector device comprises an^"electrically nonconductive support member disposed between the opposed circuit board surfaces, the support member having defined

Id therethrough a like plurality of pre-formed apertures disposed in the regions of the support member generally corresponding to the alignment of corresponding opposed pairs of first and second contact pads on the surfaces of the boards, and electrically conductive metallic

15. interconnect members extending through elastomeric material in the regions of the support member.

According to the invention, the connector device is characterized in that the metallic interconnect members extend through the elastomeric

2Q material and have first and second end surfaces exposed for direct metal-to-metal, electricity conductive contact with the first and second opposed pairs of contact pads, the interconnect members sized and arranged each to provide total resistance from a first 5 contact pad to a second contact pad of the order of less than about 25 illi-ohms. The interconnect members are arranged in a manner so their exposed end surfaces can deflect under contact pressure from a first position and be restored upon release of the contact pressure toward 0; the first position at least in part by the restorative effect of the elastomeric material, whereby the area array connector device is adapted to provide continuous electrical interconnection between opposed circuit board surfaces at varying spacing. In preferred embodiments, the support member comprises resilient elastomeric material, has support surfaces respectively opposed to the surfaces of the first and second circuit boards and is adapted to be compressed by urging of the circuit boards together. Each metallic interconnect member comprises a bodily-rotatable, electrically conductive interconnect element extending through the thickness of the resilient support member and having a pair of pad engagement ^Q surfaces disposed to engage the respective contact pads of the circuit boards, a line projected through the engagement surfaces, at the time of their initial engagement upon the first and second contact pads, being disposed at an initial, acute angle to the direction of 5 thickness of the support member. The connector further comprises means for retaining the circuit boards in a clamped-together relationship with the su po t ember in a compressed, reduced thickness state and with the interconnect member bodily rotated, whereby the line 0 projected through the engagement surfaces lies at an acute angle to the direction of thickness of the support member greater than the initial angle, the body of the support member being locally deformed by the interconnect element and resiliently biasing the S interconnect element towards its original position, into engagement with the pads. Also, the circuit boards carry a multiplicity of matching contact pads in a predetermined pattern corresponding to the arrangement of circuits on the boards, and the support member 0 includes a corresponding multiplicity of the interconnect elements, the elements each being bodily rotated in response to the clamped-together relationship of the circuit boards, locally deforming the compressed support member and being resiliently biased against the 5 respective contact pads by the support member.

Preferably the support member is of sheet form having inserted therein a multiplicity of interconnect elements in a pattern corresponding to the pattern of the pads. The support member includes a distribution of voids that serve locally to accomodate the bodily rotation of the

5 interconnect elements, preferably the support member is a layer of foam having an aggregate void volume in the range of about 25 to 95%, preferably in the range of about 60 to 75%. The elastomer is selected from the group consisting of silicone, urethane, natural rubber, rr_j copolymers of butadiene-styrene, butadiene-acrylonitrile, butadiene-isobutylene, chloroprene polymers, polysulfide polymers, plasticized vinyl chloride and acetate polymers and copolymers. The support member has a compression force deflection (CFD)

-r_5 in the range of about 2 to 50 pounds per square inch at 25 percent compression, and a compression set of less than about ten percent afj____r--2j2. hours- aτt"158°F at 50 percent compression, with one half hour recovery. The interconnect element comprises a body extending

2_Q< generally in the direction of thickness of the support member and end portions projecting from respective ends of the body in a direction overlying the respective contact pads, preferably the interconnect element is generally of S-shape, and lines of projection of the end 5 portions lie in a common plane normal to the direction of thickness of the support member. The support member further comprises a sheet-form layer of generally non-distendable material disposed generally parallel to the opposed board surfaces. _Q Also in other preferred embodiments, the interconnect element comprises at least two electrically conductive metal filaments enclosed in elastomeric material, the filaments extending in generally parallel relationship between the first and second exposed end 5 surfaces. Preferably the surface of the support member defining the aperture is of configuration differing from the configuration of the corresponding surface of the interconnect element to provide localized areas of pressure between the interconnect element and the support, more preferably the aperture has an irregular diameter. The metal filaments enclosed in the elastomeric material are in electricity-conductive contact. The support member is of elastomeric material, e.g., a foam, and the interconnect members are oriented in a manner whereby application of the contact pressure causes their angular deflection. The interconnect members are copper containing, and the exposed end surfaces are gold-plated. The apertures are formed by removal of material, preferably by punching or drilling.

According to another aspect of the invention, a connector arrangement for providing electrical interconnection between a first contact pad on a surface of a first circuit board and a corresponding second contact pad on an opposed surface of a second opposed circuit board comprises an electrically nonconductive support member of resilient elastomeric material, a bodily-rotatable, electrically conductive interconnect element, and means for retaining the circuit boards in a clamped-together relationship. The support member has support surfaces respectively opposed to the surfaces of the first and second circuit boards and is disposed therebetween, and is adapted to be compressed by urging of the circuit boards together. The interconnect element extends through the thickness of the resilient support member and has a pair of pad engagement surfaces disposed to engage the respective contact pads of the circuit boards, a line projected through the engagement surfaces, at the time of their initial engagement upon the first and second contact pads, being disposed at an initial, acute angle to the direction of thickness of the support member. The circuit boards are retained in a clamped-together relationship with the support member in a compressed, reduced thickness state and with the interconnect member bodily rotated, whereby the line projected through the engagement surfaces lies at an

5 acute angle to the direction of thickness of the support member greater than the initial angle, the body of the support member being locally deformed by the interconnect element^ and resiliently biasing the interconnect element towards its original position, into

L engagement with the pads.

The interconnect device of the invention has now made possible accurate and precise interconnection of circuit boards having large numbers of contact pads of very high density and small diameter, and the device _j_5_ may be employed to provide interconnection between all nature of planar and nonplanar surfaces, including, but not limited to: ceramic-to-printed circuit board, printed circuit board-to-printed circuit board, or ceramic-to-ceramic.

2o Also, by the interconnect element of the invention, there is achieved low contact resistance and low total resistivity of the connection system, e.g., total resistance of below about 25 milliohms and as low as 5 to 10 milliohms. The device thus provides for very

25 low contact resistance compared to filled elastomers and other prior art interconnect devices.

Other features and advantages of the invention will be understood from the following description of the presently preferred embodiment, and from the claims.

30_. Preferred Embodiment

We first briefly describe the drawings: Fig. 1 is an exploded view in perspective of a circuit including a preferred embodiment of the connector arrangement of the invention; Fig. la is an enlarged perspective view of a preferred embodiment of the interconnect element in the connector arrangement of Fig. 1;

Figs. 2, 3 and 4 are somewhat diagrammatic side 5 section views of the circuit of Fig. 1, respectively showing the circuit in exploded, assembled and compression states;

Figs. 5 and 5a are enlarged side section views of the circuit of Fig. 1 showing a 3-interconnect T/J element segment in assembled and compression states;

Figs. 6 and 6a are side section views of an alternate embodiment showing a one-interconnect element segment in the assemoled and compression states, while Figs. 7 and 7a are similar views of another alternate 2 embodiment of the interconnect element;

Figs. 8 and 9 are side section views, and Figs. 10 and 10a are side and rear section views of still other alternate embodiments of the interconnect element, while Fig. 10b is rear section view of another alternate _Q embodiment of the interconnect element having a front view as seen in Fig. 10;

Fig. 11 is a side section view of an alternate embodiment of the connector arrangement of Fig. 1 for low impedance connection, and Fig. 11a is a perspective 2 view of the interconnect element of the device of Fig. 11; and

Fig. 12 is a side section view of still another embodiment of the invention.

Referring to Fig. 1, the electrical circuit 10 20 consists of connector arrangement 12 disposed between first and second electrical circuit boards '14, 16. Clamping frame 18 is provided for fixed assembly of the circuit over alignment posts 20.

Area array connector arrangement 12 consists of 35 a sheet-form support member 13 of planar expanse, having uncompressed thickness. A, e.g., between about 0.025 inch (0.64 mm) and 0.500 inch (12.7 mm), and preferably about 0.125 inch (3.18 mm) , including resilient, electrically nonconductive elastomeric material in the

5 form of open cell foam having a density in the range of about 2 to 50 lbs/ft³ (0.032 to 0.8 gm/cm³) , preferably about 15 to 25 lbs/ft³ (0.24 to 0.40

3 gm/cm ) , compared to a material density of about 65 lbs/ft 3 (1.04 gm/cm3) , for an air or cell volume in

Iff; the range of about 25% to 95%, preferably about 60 to 75%.

The support member has a characteristic compression force deflection (CFD) in the range of 2 to 50 lbs per square inch (0.14 to 3.45 atm) at 25 percent

15 compression, and has a compression set, tested by ASTM

Test Standard D 3574, of less than 10% compression^set .-= after 22 hours at 158°F (70°C) at 50% co pressioh with ■ ■ one-half hour recovery. The foam material of support- member 13 is preferably urethane, silicone or natural

ZfJ rubber, although the specific material employed is less critical than the physical characteristics mentioned above, and other suitable materials may also be employed, e.g., copolymers of butadiene-styrene, butadiene-acrylonitrile, butadiene-isobutylene, ;

25 chloroprene polymers, polysulfide polymers, plasticized vinyl chloride and acetate polymers and copolymers. Where the elastomeric foam material is urethane, the average void diameter is of the order of about 125 microns.

20 Area array connector 12 also consists of a multiplicity of interconnect elements 22, disposed in the support member 13, and positioned selectively in the plane of the connector array, with element body 24 extending through the support member to expose contact "

35 pad engagement surfaces 26, 28 adjacent connector array surfaces 30, 32. The relative positions of the engagement surfaces are predetermined to correspond, when assembled, to the positions of contact pads on the opposed circuit board surfaces. Referring to Fig. la, in the preferred embodiment, generally S-shape interconnect element 22 consists of body 24 and tabs 27, 29 of electricity-conducting material, e.g., copper or other metal or metal-coated resin (provided the volume of metal is sufficient for the desired level of conductance, typically less than 1 ohm for power

I_d applications and less than 25 milliohms for signal applications) . When disposed in the support member in the assembled, uncompressed state, body 24 preferably lies at acute angle B, to the direction of thickness of the support member (the normal line between surfaces 30,

25 32) , angle, B, being in the range of about 0 to 70°, preferably about 20° to 40° and optimally about 30°. Angle, M, taken between a line projected through the engagement surfaces at the time of their initial engagement upon the contact pads and the direction of _Q thickness, is somewhat greater where the tabs extend generally parallel to the overlying contact pad surfaces. Element 22 has width, W, selected to be in the range of 10 to 90% of contact pad spacing, thickness, T, selected to be in the range of about 10 to

25 100% of interconnect element width, preferably between about 0.250 inch (6.35 mm) down to 0.003 to 0.005 inch (0.076 to 0.127 mm), or 0.001 inch (0.025 mm), and length, L, selected to extend at angle B generally through the support member between surfaces 30, 32 in 30 uncompressed state. In the preferred embodiment shown, W is about 0.040 inch (1.02 mm), T is about 0.010 inch (0.25 mm), and L is about 0.160 inch (4.06 mm), including the curved segments of radius, R, e.g., about 0.012 inch (0.305 mm). The contact pad.engagement 35 surfaces 26, 28, exposed on the tabs, are of area C by W, e.g., about 0.030 inch (0.76 mm) by 0.040 inch (1.02 mm) . Disposed above and below area array connector arrangement 12 are circuit boards 14, 16 having board surfaces 15, 17 respectively opposed to connector array surfaces 30, 32. Disposed on the board surfaces are contact pads 34, 36, in the embodiment shown having thickness of about 0.001 inch (0.025 mm), with a diameter of 0.050 inch (1.27 mm) on 0.100 inch (2.54 mm) centers.

When assembled (Fig. 3) , each contact pad 34 of board 14 lies in electricity-conductive contact with the opposed contact pad engagement surface 26 of a interconnect element 22, which extends through the support member 13 to electricity-conductive contact between contact pad engagement surface 28 and contact pad 36 of the .opposed circuit board 16. The pairs of contact pads connecte-d— -rar'element 22 are offset from each other-,.- and=-the elemen is configured in a manner to cause the element-to Titσv 'bodily in the support member as compressional force is applied to the opposed boards, as shown in Fig. 4, and described in more detail below.

Referring to Fig. 5, the circuit 10 is shown in assembled state, with area array connector 12 disposed between circuit boards 14, 16. Interconnect elements 22 extend through the support member 13, with contact pad ^; engagement surfaces 26, 28 of tabs 27, 29 disposed in contact with contact pads 34, 36. The centers of the opposed contact pads to be electrically interconnected are offset from each other by a distance, D, e.g., about 0.120 inch (3.05 mm), and the undersurfaces of tabs 27, 29 lie generally on the respective planar surfaces 30, 32 of the support member 13.

Referring to Fig. 5a, upon application of compression force to the opposed boards, represented by arrows, P, the gap between board surfaces 15, 17 is decreased to distance, G, equal to about 100% down to about 60% of W, the uncompressed thickness of the support member 13, e.g., in the embodiment shown, G is about 0.100 inch (2.54 mm). The combination of the structure of the interconnect elements 22, the relationship of the elements to the material of the surrounding support member matrix, and the angle of the line projected through the contact pad engagement surfaces of the interconnect element at the time of their initial engagement upon the contact pad surfaces 0 causes the interconnect elements to move bodily within the support member by rotation, e.g. about axes, X, on the support member center-line to a greater acute angle, M*, without significant flexing of the interconnect element. The cellular, open nature of the foam of

-t^ support member 13 allows the member to give resiliently by movement of elastomeric material into the foam voids, without significant adverse affect on the position of surrounding adjacent interconnect elements. As the interconnect element rotates, the contact pad engagement 0 surfaces also move along the opposed surfaces of the contact pads, indicated by arrows, S, over a distance, E, in a wiping action that removes oxides, dust particles and the like from the contacting surfaces for improved electricity-conducting contact. (Where angle B

2 is about 30°, the length, E, is typically about 0.016 inch (0.41 mm) .)

As mentioned, the interconnect elements rotate without significant flexing or deformation. As a result, when pressure, P, is removed, the resilience to

30 return the conductor element to essentially its original position, as shown in Fig. 5, is provided entirely by the resilience of the support member.

In another embodiment, the connector arrangement, shown in Figs. 6 and 6a, is a single, 3 isolated interconnect element 22", having a body 24' lying generally perpendicular to the opposed board surfaces, with tabs 26' , 28' extending outwardly, in opposite directions, parallel to the surfaces. Line, F, connecting points on the engagement surfaces of the interconnect element lies -at an initial acute angle, M, to the direction of thickness of the support member. Upon application of compression force, P, to the opposed boards 14, 16, shown in Fig. 6a, the connector element 22' rotates bodily in aperture 41, compressing the

Iff support member 13 in the area adjacent and below the tabs to a reduced thickness state, with rotational movement of the interconnect element on the surface of the contact pad causing desirable wiping action of length, E, e.g., about 0.025 inch (0.64 mm), for •_rt- improved electrical contact. (In the embodiment shown, the final gap thickness, G, is approximately equal to the uncompressed thickness". A, of the support member, with compression of the support member to reduced thickness state being confined generally to the vicinity

2σ of the connector element.)

The positions of interconnect elements in the support member are predetermined, and apertures formed at precise locations, e.g., by numerically controlled drilling. The elements may also be cast in place, or 22 the support member may be cast in a manner to provide apertures at the desired positions. Oval or even slit-form apertures may be provided, in order to more closely conform to the rectangular shape of the element, by forming the apertures, e.g., by drilling, while the

30 support member is. stretched, then allowing it to relax.

Other embodiments are within the following claims. For example, the support member may be an open cell foam or may be of other construction providing the desired voids, or, as shown in Figs. 6 and 6a, the support member may include a sheet-form layer 40 of generally nondistendible material, e.g.. Mylar© or woven fiberglass mat, in the embodiment shown, disposed along the center line between the surfaces of the support member to further minimize bulging of the material of the support member in the plane of the member under compressional force, thereby to reduce displacement of adjacent interconnect elements from the desired positions. The Mylar ^"@ film may also be 0 disposed upon support member surfaces 30, 32, the modulus of the material of the film allowing application of higher compressional force without adversely affecting performance of the connector arrangement, and also permitting adjustment of the coefficient of thermal 5 expansion of the connector arrangement.

Also, the interconnect element may be a sheet form member (122, Figs. 7 and 7a) or a round or a rectangular pin (222, Fig. 8; 322, Fig. 9, respectively) without tabs, the body of the interconnect element lying _Q at an acute angle to the direction of thickness of the support member, with contact pad engagement surfaces disposed at each end. Referring to Fig. 7a, as compressional force, P, is applied to the opposed circuit boards, the interconnect element 122 bodily _j rotates to a greater acute angle with the engagement surfaces wiping the contact pad surfaces for improved conductivity. Also as shown in Figs. 8 and 9, the interconnect elements may be provided with support-member-engaging rings (42, Fig. 8) or 0 protrusions (44, Fig. 9) to retain the pin placement within the support member, and the elements may be placed by insertion through the support member.

In another embodiment, shown in Figs. 10, 10a and 10b, the interconnect element may be bent three 5 di ensionally to cause the lines of projection of the tabs to be in different planes normal to the direction of thickness of the support member, whereby the member is caused to twist as it rotates bodily upon application of compressional force to the opposed boards, thereby providing oblique or rotational wiping of the engagement

5- surfaces on the opposed contact pad surfaces. Fig. 10 shows a side view of one possible three-dimensional interconnect element, while Figs. 10a and 10b show alternate rear views of such interconnect element configurations. 0 In a further embodiment for controlled impedance connection, shown in Figs. 11 and 11a, the support member-also may include a conductive grounded layer 52, e.g., of foam, disposed between two layers of nonconductive elastomeric material 54, 56, also

1 typically foam, to form a ground plane. The body 58 of the interconnect element is coated first wi-t- »--_aHLayer of dielectrical material and then coatedjwi h a -n t -l- outer layer 64. The protruding tabs (66, Fig-.-_lla)- ensure connection between the conductive foam layer 52 and the

20_. metal outer layer of the interconnect element.

In still another embodiment of the invention, interconnect device 10' (Fig. 12) consists of an electrically nonconductive support member 24' that is a foam elastomer matrix of thickness,- t, e.g., about 0.015

2 to 0.5 inch (0.38 to 12.7 mm), preferably about

0.035-0.040 to 0.133 inch (0.9-1.0 to 3.5 mm), having a range of compression volume at 25% compression between about 1 lb/in.² to 60 lbs/in.² (0.07 to 4.1 atm) , with the range preferably between about 6 to 45 2 30- lbs/in. (0.4 to 3.1 atm), and having density in the

₃ range from about 2 to 50 lbs/ft (0.03 to 0.8

3 gm/cm ) , preferably in the range from about 15 to 30 lbs/ft. (0.24 to 0.48 gm/cm³). Defined in member

24' are apertures 26', formed, preferabl -by drilling

35 under computer positioning, at the precise locations where it is desired to provide electrical interconnection between corresponding contact pads of the opposed printed circuit board surfaces. Disposed in each aperture 26* is an interconnect element 28', consisting of a column 30' of solid elastomeric material, e.g., silicone rubber of about 30 durometer, or foam of similar softness, through which a metallic interconnect member 32', e.g., a wire of conductive, very flexible, fine wire elements 34¹, e.g., copper, typically each about 0.001 to 0.002 inch (0.025 to 0.050 0 mm) diameter (only a few are shown) , the vast majority of which extend over the full length of the column from the end surface 36* to the end surface 38' of the element. (The wires may be caused to protrude from the ends of the element by removal of the elastomeric

, r- material, e.g., by abrasion or mechanical stripping, the wire protrusions serving to-enhance electrical -contact with the pads since the wire.is_^bent when pressed against the pads.) The exposed ends of the wire-containing interconnect elements, and of the more

2_Q rigid interconnect elements described above, are typically plated with gold or other tarnish resistant material, unless the elements are formed of non-corrosive material.

The elastomeric material extending between the

25 individual filaments of wire may form a substantially encapsulating, supporting column of elastomeric material about each wire filament, separating it from adjacent filaments, if any. In multifilament elements, however, some twisting or braiding of the wire may be provided,

30 e.g., to enhance the level of flexibility from one end of the conductor to the other and thus allow the element to be of smaller size. Also, where twisted wire is used, the wire filaments are typically in electrically conductive contact and only one or a few of the

35 filaments at one end of the element need make contact with the pad to ensure conductance to the pad at the other end of the element. In both described embodiments the filaments are generally parallel.

Column diameter is limited at the low end by the amount of conductor feasible to obtain proper electrical conductivity. Maximum diameter is limited by required spacing between contact pads, with intervening space between columns to allow for bulging of conductor columns under pressure. Diameters from 0.005 inch to 0.200 inch (0.13 to 5.1 mm) are preferred. Aperture

10 diameter must be close to or smaller than column diameter, e.g., with a range of between about +0.010 to -0.030 inch (+0.25 to -0.75 mm), and preferably +.007 to -.019 inch (+0.18 to -0.48 mm). The height of the column may vary from the thickness of the support, e.g.,

■5 by up to about ± 0.015 inch (0.38 mm) , preferably up to about ± ^* 0.005 inch (0.13- mm), so the end surfaces of the element may extend beyond the planes of -the surfaces of the support member, or, due to the relative compressibility of the foam matrix of the support as

2_Q compared to that of the columns, may lie flush or even lie below the surfaces as desired, in a configuration requiring additional pressure for proper electrical contact.

Also, where desired, the electricall

2 non-conductive support member defining formed apertures for receiving the interconnect element may be substantially rigid, e.g., glass reinforced phenolic, e.g., as sold by Rogers Corporation, Rogers, Connecticut under trade designation RX640.

30 The apertures may be formed with protrusions extending radially inwardly from the surface defining each aperture in a manner to apply pressure to the interconnect element to hold the assembly straight and centered in the aperture, as well as to enhance its

35 resilience, and to cause the material to deform into the area without protrusions. Preferably, the surface may extend radially inwardly at several points about the circumference, the aperture may be of diameter less than that of the interconnect element, e.g., the aperture may narrow axially with the surrounding surface necking inwardly to a minimum diameter at the center plane. Such designs control the connector wire contact and exert pressure toward the pads, and by having selected pressure lines, spots or rings within the molding of the support member, subtle and controlled pressure can be provided by areas of the side surfaces of the apertures that are relieved for displacement of the elastomer, thus allowing the system to be well located in the center of the apertures. The interconnect elements may thus be positioned in the molded apertures in a way as to provide lateral relief for the material of the element so that: (1) the element is held in position; and (2) the elastomeric material is allowed to resiliently flow in selected zones to provide stability and the ability to position the entire system. When pressure is applied to the assembly, the elastomer will be under axial compression and therefore have to move in the horizontal direction. The form of the molding is created in such a way to allow for controlled lateral movement, thus providing for the precise contact pressure in the system.

What is claimed is:

Claims

- 1. An area array connector device for

² providing electrical interconnection from a large plurality of first contact pads on a first printed

⁴ circuit board surface to a corresponding large plurality ^ of second contact pads on a second opposed printed

° circuit board surface,

^ said connector device comprising:

°^': an electrically nonconductive support member

^ disposed between said opposed circuit board surfaces,

¹⁰ said support member having defined -" therethrough a like plurality of pre-formed apertures

^■^ disposed in the regions of said support member generally

¹³ corresponding to the alignment of corresponding opposed

¹⁴ pairs of first and second contact pads on the surfaces

¹⁵ of said boards, and

¹⁵ electrically conductive metallic interconnect

-"-' members extending through elastomeric material in said w

^■-" regions of said support member, ^ιa characterized in that

2X1 said metallic interconnect members- extend

71 through said elastomeric material and have first and

22 second end surfaces exposed for direct metal-to-metal, 23 electricity-conductive contact with said first and 24 second opposed pairs of contact pads,

^ said interconnect members sized and

2& arranged each to provide total resistance from a first

27' said contact pad to a second said contact pad of the

2& order of less than about 25 milli-ohms, and

29 said interconnect members arranged in a

30 manner so the exposed end surfaces of said interconnect

31 members can deflect under contact pressure from a first

32- position and be restored upon release of said contact

33- pressure toward said first position at least in part by

34: the restorative effect of said elastomeric material,

35 whereby said area array connector device is

36 adapted to provide continuous electrical interconnection τι. between opposed circuit board surfaces at varying

38-'. spacing. 2. The area array connector device of claim 1 wherein said support member comprises resilient elastomeric material, has support surfaces respectively opposed to the surfaces of said first and second circuit boards and is adapted to be compressed by urging of said circuit boards together, and each said metallic interconnect member comprises a bodily-rotatable, electrically conductive interconnect element extending through the thickness of said resilient support member and having a pair of pad engagement surfaces disposed to engage the respective contact pads of said circuit boards, a line projected through said engagement surfaces, at the time of their initial engagement upon said first and second contact pads, being disposed at an initial, acute angle to the direction of thickness of said support-member, said connector further comprising means for retaining said circuit boards in a clamped-together relationship with said support member in a compressed, reduced thickness state and with said interconnect member bodily rotated whereby said line projected through said engagement surfaces lies at an acute angle to the direction of thickness of said support member greater than said initial angle, the body of said support member being locally deformed by said interconnect element and resiliently biasing said interconnect element towards its original position, into engagement with said pads.

3. The area array connector device of claim 2 wherein said circuit boards carry a multiplicity of matching contact pads in a predetermined pattern corresponding to the arrangement of circuits on said boards, and said support member includes a corresponding multiplicity of said interconnect elements. 1 said elements each being bodily rotated in

2 response to the clamped-together relationship of said

3 circuit boards, locally deforming said compressed

4 support member and being resiliently biased against the

5 respective contact pads by said support member.

6z 4. The area array connector device of claim 3

7 wherein said support member is of sheet form having

-F inserted therein a multiplicity of said interconnect

-P elements in a pattern corresponding to the pattern of

10^" said pads.

H 5. The area array connector device of claim 4

12^" wherein said support member further comprises a

13- sheet-form layer of generally non-distendable material

L4 disposed generally parallel_-tQ---said opposed.board

15 surfaces.

16. 6. The area array connector device of claim 2

17^' wherein said support member includes a distribution of

18$ voids that serve locally to accomodate the bodily

19^ rotation of said interconnect elements.

20 7. The area- array connector device of claim 6

ZL wherein said support-member comprises a layer of

22 elastomeric foam.

23 8. The area array connector device of claim 7

24 wherein said elastomeric foam has an aggregate void

25 volume in the range of about 25 to 95%.

26- 9. The area array connector device of claim 8

27 wherein said elastomeric foam has a void volume in the

28^' range of about 60 to 75%. - 10. The area array connector device of claim 7

² wherein said elastomer is selected from the group

³ consisting of silicone, urethane, natural rubber, copolymers of butadiene-styrene, butadiene-acrylonitrile, butadiene-isobutylene, chloroprene polymers, polysulfide polymers, plasticized vinyl chloride polymers and copolymers, and plasticized acetate polymers and copolymers.

11. The area array connector device of claim 2

10 wherein said support member has a compression force

11 deflection (CFD) in the range of about 2 to 50 pounds

12 per square inch at 25 percent compression.

13 12. The area array connector device of claim 2

14 wherein said support member has a compression set_of

15 less than about ten percent after 22 hours at 158°F at

16 50 percent compression with one half hour recovery.

17 13. The area array connector device of claim 2

18 wherein said interconnect element comprises a body

19 extending generally in the direction of thickness of

20 said support member and end portions projecting from the

21 respective ends of said body in a direction overlying 22. the respective contact pads.

21 14. The area array connector device of claim

24 13 wherein said interconnect element is generally of

25 S-shape.

26 15. The area array connector device of claim

27 13 wherein lines of projection of said end portions lie

28 in a common plane normal to the direction of thickness

29 of the support member. 1 16. The area array connector device of claim 1

2 wherein an interconnect element comprises a said metalic

³ interconnect member comprising at least two electrically

4 conductive metal filaments enclosed in elastomeric

5 material, said filaments extending in generally parallel

6 relationship between said first and second exposed end

7 surfaces.

8T- 17. The area array connector device of claim

3- 16 wherein the surface of said support member defining

1Q said aperture is of configuration differing from the

Hi configuration of the corresponding surface of said

12 interconnect element to provide localized areas of

13 pressure between said interconnect element and said

14 support.

15 - 18. The area array connector device of claim

16 17 wherein said aperture has an irregular diameter.

17 19. The area array connector device of claim 1 IS- wherein said metal filaments enclosed in said

19 elastomeric material are in electricity-conductive

20- contact.

21 20. The area array connector device of claim 1

22 wherein said support member is of elastomeric material.

23 21. The area array connector device of claim 1 24. or 20 wherein said elastomeric material is an

25 elastomeric foam.

26 22. The area array connector device of claim 1

27 wherein said interconnect members are oriented in a

28 manner whereby application of said contact pressure

29 causes angular deflection of said members. 23. The area array connector device of claim 1

² wherein said metallic interconnect members are copper

³ containing.

4^' 24. The area array connector device of claim 1

5 wherein the exposed end surfaces of said metallic

6 interconnect members are gold-plated.

7^" 25. The area array interconnect device of

8 claim 1 wherein said apertures are formed by removal of

9 material.

-^ 26. The area array interconnect device of

-¹"¹ claim 25 wherein said apertures are formed by punching - or drilling.

27. A connector arrangement for providing

¹⁴ electrical interconnection between a first contact pad

¹⁵ on a surface of a first circuit board and a

-^ corresponding second contact pad on an opposed surface

-^ of a second opposed circuit board,

18 said connector arrangement comprising 19 an electrically nonconductive support member 20 disposed between said circuit boards and comprising 1 resilient elastomeric material, said support member

²² having support surfaces respectively opposed to the ³ surfaces of said first and second circuit boards and -" being adapted to be compressed by urging of said circuit ^s boards together, ^ a bodily-rotatable, electrically conductive ^ interconnect element extending through the thickness of 8 said resilient support member and having a pair of pad 9 engagement surfaces disposed to engage the respective 0 contact pads of said circuit boards, a line projected through said engagement surfaces, at the time of their ^ώ initial engagement upon said first and second contact 1 pads, being disposed at an initial, acute angle to the

2 direction of thickness of said support member,

3 means for retaining said circuit boards in a clamped-together relationship with said support member

5 in a compressed, reduced thickness state and with said

6 interconnect member bodily rotated whereby said line

7 projected through said engagement surfaces lies at an 3 acute angle to the direction of thickness of said

9 support member greater than said initial angle,

IXJ the body of said support member being locally

11 deformed by said interconnect element and resiliently

12 biasing said interconnect element towards its original

13 position, into engagement with said pads.