Electrical connectors – Preformed panel circuit arrangement – e.g. – pcb – icm – dip,... – With provision to conduct electricity from panel circuit to...
Reexamination Certificate
1998-02-13
2003-02-18
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
06520778
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to resilient (spring) electrical contact (interconnection) elements (structures) suitable for but not limited to 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. Pat. No. 6,184,053, and its counterpart commonly-owned “divisional” U.S. Pat. Nos. 6,049,976 and 5,852,871, 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, and 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 U.S. Pat. No. 5,917,707 discloses a number of applications for the aforementioned spring contact element, and 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 U.S. Pat. No. 5,917,707 discloses 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 U.S. Pat. No. 5,994,152 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 U.S. patent application No. 08/819,464 filed Mar. 17, 1997 (status: pending), referenced as a parent application above and incorporated by reference herein, disclose a number of processes and metallurgies for prefabricating contact tip structures on sacrificial substrates, for later joining to ends of spring contact elements, as well as mechanisms for releasing prefabricated components of spring, contact elements from the sacrificial substrates. Many of the processes, metallurgies and mechanisms disclosed therein are directly applicable to the methods and apparatus of the present invention.
Commonly-owned, co-pending U.S. patent application No. 08/802,054 filed Feb. 18, 1997, referenced as a parent application above, discloses a technique for making microelectronic contact structures by masking and etching grooves into a sacrificial substrate (e.g., a silicon wafer), then depositing one or more layers of metallic material into the grooves, then transferring the resulting structures onto an electronic component such as by brazing, then removing the sacrificial substrate so that the fabricated structures are secured at one end to the electronic component and have another end for contacting another electronic component and function as spring contact elements. The present invention takes the concept a step further, providing an alternate technique for fabricating such spring contact elements and mounting them to terminals of electronic components.
Commonly-owned, U.S. Pat. No. 6,184,053, issued from the parent application Ser. No. 08/852,152 referenced above, discloses a technique for making microelectronic contact structures by applying a series of masking layers patterned with openings onto a substrate such as a semiconductor device, then depositing one or more layers of metallic material into the openings, then removing the masking layers. This results in a plurality of spring contact elements having been fabricated on the substrate at lithographically-defined locations.
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. The invention is useful for devices with arbitrarily large pitch, but also is particularly useful for 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.
An exemplary application for making fine-pitch pressure connections between. electronic components can be found in commonly-owned U.S. Pat. No. 5,974,662, which discloses a probe card assembly including elongate resilient (spring) contact elements mounted to a “space transformer” component. As used herein, a space transformer is a multilayer interconnection substrate having terminals disposed at a first pitch on a one surface thereof and having corresponding terminals disposed at a second pitch on an opposite surface thereof, and is used to effect “pitch-spreading” from the first pitch to the second pitch. In use, the free ends (tips) of the elongate spring contact elements make pressure connections with corresponding terminals on an electronic component being probed (e.g., tested).
Another example of an application for fine pitch spring contact elements can be found in commonly-owned U.S. Pat. No. 6,064,213, which discloses mounting springs on active semiconductor devices.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an improved technique for fabricating microelectronic contact structures, such as spring contact elements.
Another object of the invention is to provide a technique for fabricating microelectronic contact structures, such as 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 microelectronic contact structures, such as 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 microelectronic contact structure
Eldridge Benjamin N.
Grube Gary W.
Khandros Igor Y.
Mathieu Gaetan L.
Abrams Neil
FormFactor Inc.
O'Melveny & Myers LLP
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