SMTA International Conference Proceedings

The Effect of Isothermal Aging on the Reliability of Sn-Ag-Cu Solder Joints Using Various Surface Finishes

Authors: Chaobo Shen, Zhou Hai, Cong Zhao, Jiawei Zhang, John L. Evans, Ph.D. and M. J. Bozack
Company: Center for Advanced Vehicle and Extreme Environment Electronics (CAVE3) Auburn University
Date Published: 9/28/2014   Conference: SMTA International

Abstract: This paper presents test results and comparative literature data on the influence of isothermal aging and thermal cycling associated with Sn-1.0Ag-0.5Cu (SAC105) and Sn-3.0Ag-0.5Cu (SAC305) ball grid array (BGA) solder joints on three board finishes (ImAg, ENIG, ENEPIG). Weibull analysis after 125C thermal aging shows that the characteristic lifetimes for both SAC105 and SAC305 increase as: ENIG > ENEPIG > ImAg. Failure analysis shows continuous growth of Cu-Sn intermetallic compounds (IMC) on SAC/ImAg systems and Cu-Ni-Sn IMC on SAC/ENIG/ENEPIG systems at board side solder joints, which eventually cause fatigue failures. SAC305, with a higher relative fraction of Ag3Sn IMC within the solder, performs better than SAC105.

Key Words: 

Thermal cycling, Surface finishes, SAC, ENIG, ENIPIG, IMC

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