Improving the solderability and electromigration behavior of Low-Ag SnAgCu soldering

Compared with widely used SAC305 (Sn-3.0Ag-0.5Cu) solder, low-Ag (Ag≤1%) SAC solder obviously shows advantages in cost and mechanical impact resistance, and disadvantages in worse wettability, higher melting point and degeneration in electromigration, which restrict its application. Therefore, adding some suitable elements to the solder to improve the solderability and mechanical performance is very important for applications. In this paper, the solderability and electromigration behavior of Low-Ag SAC solder were studied. The effect of adding Bi and Ni elements on the wettability, melting temperature and electromigration properties of SAC0705 (Sn-0.7Ag-0.5Cu) soldering on Cu pad were analysed by SEM and DSC investigations. Results indicate that addition of some Bi and Ni elements into SAC0705 could decrease the peak melting point of the solder, improve the wettability of solder on Cu pad obviously, and decrease the IMC grain size in interface. In addition, adding some Bi and Ni elements could restrict the electromigration behavior under high temperature and high density current stressing. It is found that the thermal condition has much more influence on electromigartion behavior. The IMC polarized distribution and copper consumption aggravate sharply under higher temperature and high density current stressing condition.