THE EFFECTS OF INTERNAL STRESSRS IN BGA Ni LAYER ON THE STRENGTH OF Sn/Ag/Cu SOLDER JOINT

Due to the consideration of environmental protection policy, all electronic products are requested to be lead free. In package field, solder ball is also requested to be lead free and currently the most popular type of solder ball is the Sn/Ag/Cu solder [1]. Sn/Ag/Cu solder has higher melting point and weaker wettability [2-3] during IR re-flow profile than eutectic solder ( Sn/Pb ), therefore the strength of solder joint of Sn/Ag/Cu solder has risk to be worse than Sn/Pb Solder . In this study, the effects of internal stresses in BGA Ni layer on the strength of Sn/Ag/Cu solder joint are investigated. The drop test and peel off test are adopted in order to test the strength according to the standard of JEDEC. The peel off test and drop test results show that the higher tensile stress and compressive internal stresses in the Ni layer have worse effects on the joint strength than lower tensile internal stresses can affect. According to the failure modes analysis, the failure mode is at the intermetallic compound between BGA Ni layer and solder ball. .