RELIABILITY ESTIMATUION FOR BGA SOLDER JOINTS IN ORGANIC PKG

摘要

BGA solder joints are applied to attaching PC-board with PKG. A crack is occasionally formed at the BGA solder joint by a heat cycles due to Si chip fever. The objective of this work is study how the crack progresses at the BGA solder joints. Organic substrates jointed to Invar (Fe-36Ni Alloy) substrates with Sn-37Pb solder balls are used as test pieces. The test pieces are evaluated by thermal cycle tests. Non-linear initial strain of the BGA solder joints is calculated by FEM analysis by using 3D models. Initial crack occurred at the solder edge near the joining surface, where the maximum strain was calculated by FEM. The crack propagates in the solder with increasing of thermal cycle. Finally the fatigue life of BGA solder joints are estimated as 4times long compared with the initial crack forming life.