Stress effect on growth of IMCs at interfaces between Sn-Ag-Cu lead free solder and Cu substrate

Excessive intermetallic growth in solder joints would lead to the premature failure and stress is known to influence growth of IMC. However, no existing method is available to study effect of stress on the IMC growth in a controlled manner. In this research, a novel C-ring technique was used to carry out study of the stress effect on IMC growth at the interface between 95.8Sn-3.5Ag-0.7Cu lead-free solder and Cu substrate in three different surface finishing conditions. The growth of IMC was found to be faster in the interface subjected to compressive stress than that subjected to tensile stress for both bare Cu substrate and Cu substrate coated with electroless Ni/Pd plating and immersion Au. However, the applied stress state did not show noticeable difference in IMC growth for the Cu substrate coated with immersion Sn