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
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.