Effect of underfill on bending fatigue behavior of chip scale package

摘要

This study evaluated the mechanical behavior of chip scale packages (CSPs) with the underfills using the four-point bending test. The bending fatigue durability in the CSP increased with increasing glass transition temperature (T_g) of the underfill. The mechanical fatigue cracks occurred in the region between the (Ni,Cu)_3Sn_4 layer and the solder region near the upper substrate and the solder region of the CSP with the underfill which had the higher T_g. However, these cracks occurred in the region between the (Ni,Cu)_3Sn_4 layer and the Ni_3P layer near the bottom substrate and the solder region of the CSP with the underfill which had the lower T_g.