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Flip-chip bonding on 6-um pitch using thin-film microspring technology


Bonding-pad densities on high-performance integrated-circuit chips are beginning to exceed the limits of available interconnect technologies. Also, stresses due to thermal mismatch in flip-chipped packages are reducing time to contact failure. We have addressed both of these problems by microlithographically fabricating highly elastic cantilever springs in linear arrays on pitches down to 6-um. We have soldered test arrays of 52 springs on this pitch to Si chips with 100% contact yield and good solder wetting to every spring. The fine-pitch capability also facilitates off-chip routing; the very high compliance of the springs should avoid thermal fatigue; and low thermal conductance along the springs should allow fast-cycle soldering of chips to multi-chip modules as well as replacement chips subsequently testing faulty.

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Smith, D. L. ; Fork, D. K. ; Thornton, R. L. ; Alimonda, A. S. ; Chua, C. L. ; Dunrowicz, C.; How, J. Flip-chip bonding on 6-um pitch using thin-film microspring technology. 1998 Proceedings of the 48th Electronic Components and Technology Conference; 1998 May 25-28; Seattle, WA. New York: IEEE; 1998; 325-329.


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