Tin whisker growth on electroplating Sn bilayer

In this work, matte Sn bilayer with different grain size in each layer were electrodeposited onto IC leads to adjust the internal stress of tin films and thus affect tin whisker growth. Sn/Ni film was also deposited in order to compare with the matte Sn bilayer. Microstructural characterization of Sn bilayer and Sn/Ni film were analyzed through surface and cross-section examination using field emission scanning electron microscope (FE-SEM). The IC leads with both Sn/Ni film and Sn bilayer were mounted on the PCB boards and evaluated by TCT testings. Tin whisker growth evaluation at room temperature condition revealed that both Ni barrier and matte Sn bilayer structure could mitigate the tin whisker growth. The TCT evaluation results revealed that tin whisker growth of Sn bilayer system was much less than that of the Sn/Ni film system.