SMTA International Conference Proceedings

Microstructure and Reliability Studies of Mixed Sn-Pb and Pb-Free BGA Soldering

Authors: Ken Kramer, Ph.D., Corey Nelson, Alok Sharan, Ph.D.
Company: Micro Systems Engineering, Inc.
Date Published: 9/28/2014   Conference: SMTA International

Abstract: Backward compatible mixed-alloy soldering has been carried out on area array packages with Pb-free bumps and eutectic SnPb soldering paste. Thermal fatigue reliability testing indicates reduced performance relative to pure SnPb or Pb-free solder joints. Microstructural studies show evidence of shrinkage voids within the Pb-rich eutectic phase regardless of the peak reflow temperature and level of mixing. There is inconsistent evidence of segregation of the Pb-rich eutectic phase to the pad surfaces. Underfill is recommended to mitigate the increased risks of mixed alloy soldering of area array.

Key Words: 

backward compatible, mixed alloy

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