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Size dependent dewetting and sideband reaction of eutectic SnPb on Au/Cu/Cr multilayered thin film

Published online by Cambridge University Press:  31 January 2011

D. W. Zheng
Affiliation:
Department of Materials Science and Engineering, UCLA, Los Angeles, California 90095-1595
Z. Y. Jia
Affiliation:
Department of Materials Science and Engineering, UCLA, Los Angeles, California 90095-1595
C. Y. Liu
Affiliation:
Department of Materials Science and Engineering, UCLA, Los Angeles, California 90095-1595
Weijia Wen
Affiliation:
Department of Materials Science and Engineering, UCLA, Los Angeles, California 90095-1595
K. N. Tu
Affiliation:
Department of Materials Science and Engineering, UCLA, Los Angeles, California 90095-1595
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Abstract

Dewetting of eutectic SnPb on blank Au(500 Å)/Cu(1 μm)/Cr(800 Å) layered structure was found to have a solder size dependence. At 250 °C, if the solder weight fell below 4 mg, dewetting occurred from the center of the solder cap; if the solder weight went beyond 6 mg, dewetting happened from the cap edge. In the latter case, a smaller cap with a higher wetting angle was formed at the center and a ring of solder was left around the edge. Large voids were left in the solder cap after dewetting in both cases. In contrast, all solder caps were found to dewet from the edge on a patterned film at 250 °C if the solder ball was large enough to wet the whole film initially, irrespective of the solder size. For comparison, pure Sn, eutectic SnAg, and eutectic SnBi caps also dewetted from the edge of the Au/Cu/Cr thin film, irrespective of the solder size or whether the substrate was patterned. Since eutectic SnPb on blank Au/Cu/Cr is the only case in which a large sideband growth was found and the dewetting occurred from the center, we postulated sideband to be the main factor which controls the unusual dewetting. The link between them is discussed.

Type
Articles
Copyright
Copyright © Materials Research Society 1998

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References

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