Thermal fatigue analysis of a CBGA package with lead-free solder fillets

Reliability performance of a ceramic ball grid array (CBGA) package using lead-free solder fillets is numerically examined from the viewpoint of viscoplastic deformation and thermal fatigue life. Three lead-free solder alloys, nearly peritectic antimony-tin (Sb5-Sn95), eutectic silver-tin (Ag3.5-Sn96.5) and eutectic zinc-tin (Zn9-Sn91), were considered in this study. A finite element model was used to analyze a 32 mm single chip module (SCM) CBGA package under a 0/100°C accelerating thermal cycling (ATC) load with a frequency of 2 cycles per hour. Model validation shows that the predicted mean solder joint fatigue life of a standard CBGA package using Pb37-Sn63 solder fillets has good agreement with experimental data. The prediction results also indicate that these lead-free alloys can be used as alternative solder fillet materials to improve the resistance to creep and fatigue of CBGA solder joints compared to that of the standard CBGA package. The predicted mean fatigue life of a CBGA package with lead-free solder fillets of Sb5-Sn95 is 1.69×, Ag3.5-Sn96.5 is 2.62×, and Zn9-Sn91 is 3.01× relative to that of Pb37-Sn63 soldered CBGAs