Characterization of Gold Microcontacts

Low Force Contact Resistance Measurements of Gold Microcontacts Using Piezoresistive Cantilevers

Beth Pruitt, PhD candidate

Advisor: Prof. Tom Kenny


The electronics packaging and testing industry is interested in the development of new methods for making contacts to electronic chips that allow improvement or replacement of conventional wirebonding or solder flip-chip techniques. One approach involves the use of flexible contact structures that are integrated with the package or the testing apparatus and allow the device to be fully contacted by simply placing and pressing the interconnect array into contact. This technology critically depends on the electrical properties of low-force electrical contacts. This research aims to characterize the electromechanical properties of such contacts, using instrumented MEMS force sensors. The research is in collaboration with Formfactor, Inc., a semiconductor test and packaging solutions provider.
We have designed, fabricated, and characterized a micromechanical force sensor integrated with a 4- wire electrical contact characterization capability, as shown at right. This sensor consists of a silicon cantilever beam with a piezoresistive force sensor suitable for high-accuracy force measurements in the mN- nN range. The contact tips consist of a metal-coated glass sphere (for well-known contact geometry) or a solid gold "ball" (for highly-compliant contact structure); each of these is also coated with varying thicknesses of metals, deposited by evaporation, sputtering, or plating. When combined with accurate nanoindentation force measurements on the same materials and geometries, we can extract precise measurements of contact mechanics with simultaneous resistance measurements over an array of geometries, film thicknesses, and compositions.

On-Going Work:

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Beth Pruitt, Feb. 2001
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