Reliability Analysis of Aging in Joint Microstructures for Sn-Ag-Cu Solder Joints During Thermal Cycling

This study illustrates 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). The resulting degradation shows that the characteristic lifetimes for both SAC105 and SAC305 decrease in the order ENIG > ENEPIG > ImAg. SAC305, with a higher relative fraction of Ag3Sn IMC within the solder, performs better than SAC105. SEM and EDX 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.Copyright © 2015 by ASME