Thermal fatigue performance of Sn–Ag–Cu chip-scale package with underfill

The thermal fatigue properties of the solder joints with various underfills were evaluated by thermal shock test. The thermal fatigue crack initiated at the bottom edges of interface between the (Ni,Cu)3Sn4 intermetallic compounds layer and the Ni3P layer and spread to all the interfaces with increasing number of thermal shock cycles. The thermal fatigue properties of package with underfill, which has the higher glass-transition temperature (Tg) and lower coefficient of thermal expansion (CTE) were better than those of the package with underfill having the lower Tg and higher CTE value.