The behavior of Sn whisker growth on Sn-0.7Cu-0.05Ni solder joint during thermal cycling

The present study investigates the behavior of Sn whisker growth on Sn-0.7Cu-0.05Ni solder joints during thermal cycling conducted for 1500 cycles at temperature of - 40 (+ 0/- 10) degrees C and + 85 (+ 10/- 0) degrees C through industry standard practices JESD22-A121A established by the Joint Electron Device Engineering Council (JEDEC). Results determine that the growth rate of Sn whisker on the Sn-0.7Cu-0.05Ni solder joint was slower than the Sn-0.7Cu solder joint and consequently show that the 0.05% addition of Ni is able to suppress the growth of Sn whisker during thermal cycling. Furthermore, the stabilization of hexagonal eta-Cu6Sn5 of (Cu,Ni)6Sn5 IMC interfacial layer in Sn-0.7Cu-0.05Ni solder joints significantly contributes to a lower coefficient of thermal expansion (CTE) compared to Cu6Sn5 IMC interfacial layer, thereby reducing thermal mismatch stress for Sn whisker growth on the Sn0.7Cu0.05Ni solder joint. The implications of this study are substantial for effective approach to mitigate Sn whiskers growth through consistent inspection protocols and adherence to industry standard practices.