Evaluate anti-shock property of solder bumps by impact test

Anti-shock property of lead-free Sn96.5-Ag3.0-Cu0.5 solder bumps was investigated by the high speed impact to explore the relation among the fracture modes and the reflow profile and the microstructure of solder joint. Solder bumps were formed with various reflow profiles and multi-reflow and then subjected to the impact test under a constant speed of 1.8m/s and a shear standoff of 50μm. The results show that the IMC status has a close relation with the impact behavior upon one reflow. When the heating factor increases beyond 800 s-°C, the thickness of IMC layer goes up, and the impact absorbed energy of solder bump raises quickly. Upon multi-reflow using the same profile, the IMC thickness changed a little but the failure modes varied a lot.