Electrical connector having a supported bulge configuration

Abstract: Electrical interconnects, configured as one or more supported bulges (42, 90), are formed in both one or more of electrical conductors (32, 94) in a circuit or flexible cable (24, 92) and in any insulation (34, 98) underlying the conductors at the sites of the interconnects. The bulges may be placed individually in each conductor, or traverse the circuit or cable in a straight, curved, segmented or other broken or unbroken meandering path as a V-shaped or hollow shaped fold, wrinkle or crease in both the conductors and any insulation underlying the conductors at the sites of the interconnects. Supports (56, 108) for the bulges are so composed as to be physically, electrically and chemically compatible with their surrounding materials.

Description: The present invention relates to an electrical connector according to the preamble of claim 1; in particular, the invention relates to such connectors which have a pointed, serial or continuous supported bulge configuration, such as one or more upsets, e.g. V-shaped and hollow shaped, wrinkles, folds and creases, in both one or more of the conductors in the circuit and any insulation underlying the conductors at the sites of the interconnects. The interconnection of the electronic components, especially high density electronic components and printed wiring boards, presents recurring problems for which multitudes of solutions have been presented. Conventionally, micro-connectors, because of their small sizes, require soldering or other very expensive techniques. In particular, most connectors cannot handle a 0.0762 mm to 0.1270 mm or smaller line width and spacing in an efficient manner. Accordingly, many conventional interconnection systems utilize pads or electrically conductive dots as a means of providing the interconnection, such as is disclosed in US-A-4,125,310 and US-A-4,453,795. These patents describe a plurality of generally resilient metallic raised projections. In the latter patent, a resilient backup mechanism is used to avoid overstressing and squashing of the resilient projections or contacts beyond their elastic limit, which overstressing precludes repeated mating and unmating of connectors incorporating such projections. While these terminations otherwise effectively and reliably interconnect mating circuits, their manufacture can be difficult, time consuming and costly. Furthermore, the manufacturing process for forming such bumps is limited to a size of about 0.0508 mm in diameter. In addition, such bumps require proper support, without placing them at hazard to delamination due to outgassing from support materials during or after production or to inattention to thermal matching with its surrounding materials, or to possible electrical or chemical interaction with the surrounding materials. An electrical connector according to the preambles of claims 1 and 11 is known from EP-A-0 476 868. This document discloses an electrical connector which is used for providing a pressure-type contact for cable terminations. In this known electrical connector, a metallic wafer is electroplated with a raised conductive interconnection feature or bump which is located within a conductive pattern. Subsequently a dielectric layer is laminated on the upper surface of the device, thus forming an upper layer of dielectric material. In addition, a lower layer of dielectric material is provided, this lower layer not being provided at the site of the interconnections so that the interconnections can be contacted from the lower side. A major disadvantage of this known connector has to be seen in that the line or conductor width or the spacing between neighbouring lines (conductors) cannot be made as small as this would be necessary for micro-connection applications. It is therefore the object of the present invention to improve a connector according to the preamble of claim 1 in such a way that micro connections can easily be obtained. This object, according to the present invention, is solved by the advantageous measures indicated in claim 1. Several advantages are derived from the present invention. Line widths and spacing between lines of less than 0.0762 mm, e.g., 0.0254 mm or less, are obtainable so that the cable may be connected to a printed wiring board or a flexprint circuit, without the need to utilize other connectors, solder or welding. The resulting interconnection scheme provides for a low weight, low volume and low profile interconnection. The cost of manufacturing such bump configurations is much lower as related to those of prior connection systems. Other aims and advantages, as well as a more complete understanding of the present invention, will appear from the following explanation of exemplary embodiments and the accompanying drawings thereof, in which: FIG. 1 illustrates a corner of a chip and multiple leaded flat circuit, such as a flexprint circuit, extending therefrom with its contacts having the bulge configuration of the present invention; FIG. 2 is a side view in partial cross-section of an arrangement, such as is illustrated in FIG. 1; FIG. 3 illustrates a further embodiment for interconnecting a stack of chips and their flexprint circuits, such as shown in FIGS. 1 and 2; FIG. 4 is a top view of a flat cable arrangement; FIG. 5 depicts the cable arrangement, such as shown in FIG. 4, employing a bulge configuration having a linear or curved pattern; FIG. 6 is a top view of a flexible circuit with individual bulge configurations on conductors therein; FIG. 7 is a cross-sectional view of one of the bulge configurations, such as depicted in FIG. 6; FIG. 8 is an alternate arrangement of the bulge configuration; FIG. 9 depicts a method for forming one or more bulge configurations; and FIGS. 10a-10d illustrate patterns of bulge configurations extending across a cable. FIG. 1 illustrates a corner of an electronic assembly 20 comprising a chip 22, a flexprint or flat circuit 24 and supporting hardware 26. Flat circuit 24 includes a plurality of fine lines, leads or conductors 28 which are electrically connected to the chip and extend upwardly to electrical connecting points 30. The assembly thus far described is of conventional construction, except that connecting points 30 and their supports are configured in accordance with the present invention as defined in claim 1. As shown in FIG. 2, a conductor 32, which is illustrative of all conductors in flexprint circuit 24, is imbedded within upper and lower layers 34 and 36 of dielectric material, such as of polyimide plastic. A supported bulge configuration 38, comprising individual bulges or upsets, is formed at sites 40 on the conductor 32 where contacts are desired. These sites 40 are produced by removal of plastic insulation from lower plastic layer 36 to provide openings 42 therein. In the present invention, the bulge configurations 38 are provided in both the conductor 32 and portions of upper plastic layer 34. As shown, bulge configurations 38 are V-shaped, having a convex portion 46 and a concave portion 48. The concave portion is of sufficient height that it extends beyond the smooth surface, denoted by reference sign 50, of flat circuit 24. This extension of convex portion 46 permits the exposed portion of conductor 32 to contact a mating conductor 52 on another article 54, such as a further flat circuit, printed wiring board, and a cable. A support 56, having V-shaped protuberances 58, fits within concave portions 48 of flat circuit 24, to insure contact between convex portions 46 and mating conductors 52. Support 56 may be formed of any rigid material, and may comprise a metal, if the metal is insulated from conductors 28, or a rigid dielectric material. It is important that the material of support 56 also is chemically compatible with the materials constituting the flat circuit. The scheme shown with respect to FIG. 2 for a single chip and flat circuit may be utilized for assembling a plurality of chips and flat circuits into a stack, as shown in FIG. 3. In this embodiment corresponding to the definition of the invention given in claim 11, the various elements are substantially the same as that shown in FIG. 2 and, therefore, are designated with the same numerals, but differentiated by the addition of the letters "a" through "d" after the numeral, in order to illustrate a plurality of flat circuits 24a, 24b, 24c and 24d , each having an upper plastic film 34a and a lower plastic film 36a encapsulating electric conductors 32a. Because the intention in this embodiment is to electrically couple all four chips of FIG. 3 into a stack at interconnection sites 38a of the respective flexprint circuits, insulation material from both upper layers 34a and lower layers 36a are removed to provide respective openings 60 and 40a. The respective conductors 32a are bulged at sites 38a to provide V-shaped configurations, which define convex portions 46a and concave portions 48a. These V-shaped portions of conductor 32a are configured to be mutually interfittable, so that all intermediate concave and convex portions will contact. Support 56a having a V-shaped protuberance 58a is fitted into one of the concave portions at an outer face 62 of the stacked together circuits. The stacking of the V-shaped protuberances, in conjunction with support 56a, provides support for all protuberances. Referring now to FIGS. 4 and 5, a flat circuit or cable 64 comprises a plurality of conductors 66 encapsulated in plastic layers 68 and 70. The cable 64 has smooth surfaces 72 and 74, with an opening 76 in its surface 74 to define a site 78 for an interconnect. The interconnect is formed by displacing a portion 80 of conductor 66 and a portion 82 of upper plastic layer 68. To insure that the interconnect formed by portions 80 and 82 maintain their shape, a support 84 having a V-shaped protuberance 86 is positioned on smooth surface 72 of cable 64 and placed within the concave portion of the interconnect. As illustrated in FIG. 4, support 84 is maintained in contact with the cable 64 by means of a cooperating plate secured to support 84 by fastening means such as screws 88 or to another plate in contact with surface 74 of plastic layer 70. FIGS. 6 and 7 illustrate the bulge configuration as a sequence of pointed bulges or upsets 90 in a flat cable 92. Cable 92 includes a plurality of electrical conductors 94 encapsulated between upper and lower plastic layers 96 and 98. Material is removed from upper layer 96 to form an opening or window 100 for exposing an upper surface 102 of conductor 94, said upper surface 102 being closest to the smooth surface, denoted by reference sign 104, of the flat cable 92 and its upper layer 96. A pointed bulge is formed in each conductor 94 and its underlying plastic portion 106 of lower layer 98 sufficient to extend upper conductor surface 102 beyond the smooth surface 104 of the flat cable 92, in readiness for electrical contact with a mating contact. A support 108, comprising a small amount of rigid plastic, such as EPON 825 (a trademark of Shell Chemical Company for a diglycidyl ether of Bisphenol A), is positioned within the concave portion, designated by reference sign 110, of each upset 90. This EPON 825 rigid plastic is a preferred material as meeting the several physical, electrical and chemical criteria for a support. A backup film 112 or other suitable layer is affixed to the surface, identified by reference sign 114, of lower layer 98 of the flat cable 92, to assure that support 108 will remain in position. In FIG. 8, which illustrates an alternate embodiment of the present invention, a support 116 is configured with a partial spherical surface 118 which interfits within a like spherical concave portion 120 of a bulge configuration 122. FIG. 9 illustrates a method for forming a bulge configuration and utilizes a tool 130. Tool 130 comprises a die 132 and a blade 134. Die 132 has an opening 136 of width W . Blade 134 has a thickness A and, preferably, terminates in a rounded end 138. A flat cable 140 having a thickness B , is positioned on die 132 and is so located that its opening 142 in a layer 143 of flat cable 140 defines a site 144 for the interconnect to be formed. The relationships of the dimensions of the tool and the cable is such that W = A + B + t , where t is a tolerance, for example of 0.005 inches (0.127 mm), which is intended, in conjunction with rounded blade end 138, to form a proper V-shaped bulge without piercing or cutting into cable 140. The bulge configurations of the present invention, as shown in FIGS. 10a-10d, may take any suitable shape, whether pointed, serial or continuous, to form one or more upsets, wrinkles, folds and creases in both one or more of the conductors in the circuit or cable and in any insulation underlying the conductors at the sites of the interconnects. FIGS. 10a-10d exemplify several paths of linear and curved creases, folds or wrinkles. In FIG. 10a, bulge configuration 146 is patterned to take a path which extends linearly at an angle or diagonal to conductors 148 of a cable 150. In FIG. 10b, a bulge configuration 152 is patterned with a path which extends at a sequence of lines 152a and 152b across conductors 154 of a cable 156. In FIG. 10c, bulge configuration 158 has a pattern whose path gradually arcs across conductors 160 of a cable 162. FIG. 10d illustrates a bulge configuration 164 formed as a semi-circle traversing conductors 166 of a cable 168. All of the bulge configurations shown in FIGS. 10a-10d, are supported by like-patterned supports.

Claims: Electrical connector, comprising: [a] a flat circuit (24) including electrical conductors (32) within an upper layer (34) and a lower layer (36) of dielectric material; [a1] said lower layer (36) having a smooth surface (50); and [b] said conductors (32) having sites (40) defining positions of electrical interconnects, at which sites said electrical conductors (32) are exposed in openings (42) in said lower layer (36), whereby [b1] a conductor portion in said opening protrudes beyond the level of the smooth surface (50) of said lower layer (36); characterized in that [c1] the protruding conductor portion is established by a bulge configuration (38) including the conductor in said opening and said upper layer (34), whereby said bulge configuration (38) defines a convex surface portion (46) of this conductor and a corresponding concave surface portion (48) of said upper layer (34); and [c2] said bulge configuration (38) is supported by a support (56) having protuberances (58) shaped to be fitted into the concave surface portion (48) of said upper layer (34). Electrical connector according to claim 1, in which said bulge configuration (38) comprises a plurality of bulges wherein each of these bulges has a concave (48) and a convex (46) portion, and wherein said support (56) comprises protuberances (58) placed in said concave (48) portions. Electrical connector according to claim 2, further comprising a backing on said support (56) and said protuberances (58) for support thereof. Electrical connector according to one of claims 1 through 3, in which said bulge configuration (38) comprises a plurality of deformations in respective ones of said conductors (32) and said upper layer (34). Electrical connector according to one of claims 1 through 4, in which said bulge configuration (38) comprises a V-shaped fold extending across at least some of said conductors (32) and any of said underlying dielectric material (34). Electrical connector according to one of claims 1 through 5, in which said bulge configuration (38) extends in a pattern across said conductors (32). Electrical connector according to claim 6, in which said pattern extends linearly at an angle to said conductors (32). Electrical connector according to claim 6, in which said pattern extends linearly and normally to said conductors (32). Electrical connector according to claim 6, in which said pattern extends as a sequence of lines angularly disposed to one another and to said conductors (32). Electrical connector according to claim 6, in which said pattern extends in a curved path across said conductors (32). Electrical connector, comprising: [a] a flat circuit (24a-24d) including electrical conductors (32a) within an upper layer (34a) and a lower layer (36a) of dielectric material; [a1] said lower layer (36a) having a smooth surface; [b] said conductors (32a) having sites (40a) defining positions of electrical interconnects, at which sites said electrical conductors (32a) are exposed in openings in said upper layer (34a) and said lower layer (36a), whereby [b1] a conductor portion in said opening protrudes beyond the level of the smooth surface of said lower layer (36a); characterized in that [c1] the protruding conductor portion is established by a bulge configuration (80) including the conductor in said opening, whereby said bulge configuration (80) defines interfittable concave (48a) and convex (46a) surface portions of said conductor; [d] each flat circuit (24a-24d) is adapted to interconnect with at least one further circuit (24a-24d) having identically formed bulge configurations (80) in order to form a stacked circuit arrangement having an outer face(62), the bulge configurations (80) of neighbouring circuits being interfitted in electrical contact with one another when said circuits are stacked together; [c2] the bulge configuration of that one circuit (24a) which is forming said outer face(62) is supported by a support (56a) having protuberances (58a) shaped to be fitted into the concave surface portion (48a) of this circuit (24a). Electrical connector according to claim 11, in which the respective bulge configurations (80) extend in like patterns across the respective conductors (32). Electrical connector according to one of claims 1 through 12, in which said support (56; 56a) is electrically, physically and chemically compatible with said dielectric material.

Inventors: SOBHANI MOHI, SOBHANI, MOHI
Applicants: HUGHES AIRCRAFT CO, HUGHES AIRCRAFT COMPANY
Application year: 1993
Main classification: H01R23
IPC codes: H05K3, H01R12, H05K1, H01L23