Improving Low-Ag Pb-Free Solder Performance by Adding Bi, Ni Elements
In this study, some Ni, Bi elements were added into low-Ag (less than 1%) Sn-Ag-Cu (SAC) solder. The effect of these additive elements on the solderability, intermetallic compounds (IMCs), and electromigration performance of low-Ag SAC (LASAC) solder were investigated. With the increase of Bi content in LASAC-0.05Ni-xBi (x=0, 2.0, 2.5, 3.0, 3.5, 4.0) solders, the peak melting point decreases while the wetting area of solder alloy increases. With the addition of Ni, the IMC between Cu pad and LASAC solder transforms from Cu6Sn5 to (Cu1-xNix)6Sn5 and the morphology of the IMC turns from bulk-like to needle-like. Either the addition of Bi or Ni will slow down the IMCs growth rate during high temperature storage aging (HTS) at 180°C and has a positive effect on electromigration performance of LASAC soldering.
Zhengyi Jiang, Shanqing Li, Jianmin Zeng, Xiaoping Liao and Daoguo Yang
F. L. Sun et al., "Improving Low-Ag Pb-Free Solder Performance by Adding Bi, Ni Elements", Advanced Materials Research, Vols. 189-193, pp. 3498-3502, 2011