Electrical connectors – Preformed panel circuit arrangement – e.g. – pcb – icm – dip,... – With provision to conduct electricity from panel circuit to...
Reexamination Certificate
1997-02-18
2002-11-19
Abrams, Neil (Department: 2839)
Electrical connectors
Preformed panel circuit arrangement, e.g., pcb, icm, dip,...
With provision to conduct electricity from panel circuit to...
C324S762010
Reexamination Certificate
active
06482013
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to resilient electrical contact (interconnection) elements (structures), also referred to as spring contacts, suitable for effecting pressure connections between electronic components and, more particularly, to microminiature spring contacts such as may be used in probing (resiliently and temporarily contacting) microelectronic components such as active semiconductor devices.
BACKGROUND OF THE INVENTION
Commonly-owned U.S. patent application Ser. No. 08/152,812 filed Nov. 16, 1993 (now U.S. Pat. No. 4,576,211, issued Dec. 19, 1995), and its counterpart commonly-owned copending “divisional” U.S. patent application Ser. No. 08/457,479 filed Jun. 01, 1995 (status: allowed issue fee paid) and 08/570,230 filed Dec. 11, 1995 (now U.S. Pat No. 5,852,871, issued Dec. 29, 1998), all by KHANDROS, disclose methods for making resilient interconnection elements for microelectronics applications involving mounting an end of a flexible elongate core element (e.g., wire “stem” or “skeleton”) to a terminal on an electronic component coating the flexible core element and adjacent surface of the terminal with a “shell” of one or more materials having a predetermined combination of thickness, yield strength and elastic modulus to ensure predetermined force-to-deflection characteristics of the resulting spring contacts. Exemplary materials for the core element include gold. Exemplary materials for the coating include nickel and its alloys. The resulting spring contact element is suitably used to effect pressure, or demountable, connections between two or more electronic components, including semiconductor devices.
Commonly-owned, copending U.S. patent application Ser. No. 08/340,144 filed Nov. 15, 1994 and its corresponding PCT Patent Application No. PCT/US94/13373 filed Nov. 16, 1994 (now U.S. Pat. No. 5,917,707 issued Jun. 29, 1999) (WO95/14314, published May 26, 1995), both by KHANDROS and MATHIEU, disclose a number of applications for the aforementioned spring contact element, and also disclosed techniques for fabricating contact pads at the ends of the spring contact elements. For example, in
FIG. 14
thereof, a plurality of negative projections or holes, which may be in the form of inverted pyramids ending in apexes, are formed in the surface of a sacrificial layer (substrate). These holes are then filled with a contact structure comprising layers of material such as gold or rhodium and nickel. A flexible elongate element is mounted to the resulting contact structure and can be overcoated in the manner described hereinabove. In a final step, the sacrificial substrate is removed. The resulting spring contact has a contact pad having controlled geometry (e.g., sharp points) at its free end.
Commonly-owned, copending U.S. patent application Ser. No. 08/452,255 filed May 26, 1995 (status pending) and its corresponding PCT Patent Application No. PCT/US95/14909 filed Nov. 13, 1995 (WO96/17278, published Jun. 06, 1996), both by ELDRIDGE, GRUBE, KHANDROS and MATHIEU, disclose additional techniques and metallurgies for fabricating contact tip structures on sacrificial substrates, as well as techniques for transferring a plurality of spring contact elements mounted thereto, en masse, to terminals of an electronic component (see, e.g.,
FIGS. 11A-11F
and
12
A-
12
C therein).
Commonly-owned, copending U.S. Provisional Patent Application No. 60/005,189 filed May 17, 1996 superceded by U.S. application Ser. No. 08/788,740, filed Jan. 24, 1997 (essentially identical to the PCT application, status: allowed, issue fee paid), and its corresponding PCT Patent Application No. PCT/US96/08107 filed May 24, 1996 (WO96/37332, Published Nov. 28, 1996), both by ELDRIDGE, KHANDROS, and MATHIEU, discloses techniques whereby a plurality of contact tip structures (see, e.g, #620 in
FIG. 6B
therein) are joined to a corresponding plurality of elongate contact elements (see, e.g., #632 of
FIG. 6D
therein) which are already mounted to an electronic component (#630). This patent application also discloses, for example in
FIGS. 7A-7E
therein, techniques for fabricating “elongate” contact tip structures in the form of cantilevers. The cantilever tip structures can be tapered, between one end thereof and an opposite end thereof. The cantilever tip structures of this patent application are suitable for mounting to already-existing (i.e., previously fabricated) raised interconnection elements (see, e.g., #730 in
FIG. 7F
) extending (e.g., free-standing) from corresponding terminals of an electronic component (see. e.g., #734 in FIG.
7
F).
Commonly-owned, copending U.S. Provisional Patent Application No. 60/024,555 filed Aug. 26, 1996, superceded by U.S. application Ser. No. 08/819,464, filed Mar. 24, 1997 (status: pending), by ELDRIDGE, KHANDROS and MATHIEU, discloses, for example at
FIGS. 2A-2C
thereof, a technique whereby a plurality of elongate tip structures having different lengths than one another can be arranged so that their outer ends are disposed at a greater pitch than their inner ends. Their inner, “contact” ends may be collinear with one another, for effecting connections to electronic components having terminals disposed along a line, such as a centerline of the component.
The present invention addresses and is particularly well-suited to making interconnections to modern microelectronic devices having their terminals (bond pads) disposed at a fine-pitch. As used herein, the term “fine-pitch” refers to microelectronic devices that have their terminals disposed at a spacing of less than 5 mils, such as 2.5 mils or 65 &mgr;m. As will be evident from the description that follows, this is preferably achieved by taking advantage of the close tolerances that readily can be realized by using lithographic rather than mechanical techniques to fabricate the contact elements.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an improved technique for fabricating spring contact elements.
Another object of the invention is to provide a technique for fabricating spring contact elements using processes that are inherently well-suited to the fine-pitch close-tolerance world of microelectronics.
Another object of the invention is to provide a technique for fabricating spring contact elements that are suitable for probing electronic components such as semiconductor devices, and that is readily scaleable to probing fine-pitch peripheral interconnect structures.
Another object of the invention is to provide a technique for fabricating spring contact elements that are suitable for socketing electronic components such as semiconductor devices, such as for performing burn-in on said devices.
According to the invention, an elongate spring contact element suitable for microelectronic applications is fabricated by forming depressions (such as trenches, such as by etching) in a sacrificial substrate and depositing (such as by plating) metallic materials into the depressions. A plurality of spring contact elements may be fabricated in this manner on a single sacrificial substrate, with lithographically-defined tolerances (e.g., dimensions, spacings).
The resulting spring contact elements may then be mounted to another substrate such as a passive substrate or an active substrate such as a semiconductor device, after which the sacrificial substrate is removed.
An exemplary spring contact element formed in this manner has a length “L” between its base end and its contact end. The base end is preferably offset in a first direction from a central portion of the spring contact element, and the contact end is preferably offset in an opposite direction from the central portion. In this manner, the overall spring contact element is not planar and, when its base end is mounted to an electronic component, its contact end extends above the surface of the electronic component to which it is mounted.
An exemplary sacrificial substrate upon which the spring contact elements may be fabricated is a silicon wafer, in which case the process of
Eldridge Benjamin N.
Grube Gary W.
Khandros Igor Y.
Mathieu Gaetan L.
Abrams Neil
FormFactor Inc.
Sterne Kessler Goldstein & Fox PLLC
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