Thermal stability of intermetallic compounds at Sn-0.7Cu-10Bi-xNi/Co interface during reflows

In this paper, thermal stability of Sn-0.7Cu-10B-xNi/Co (SCB-xNi/Co, x = 0.05, 0.10 and 0.15, in wt.%) interface during multiple reflows was investigated. Both (Ni, Co)Sn-3 and (Cu, Ni)(6)Sn-5 phases were formed at the SCB-xNi/Co interface after the initial reflow. With the increase of reflow number, the thermal stability of intermetallic compounds (IMCs) layer at high temperature was significantly different. The content of Ni atoms determined the thermal stability of IMCs layer in the interface reaction process. At the IMCs layer at the SCB-0.15Ni/Co interface, Ni atoms were enriched excessively, but they were present in a dispersive distribution at SCB-0.05Ni/Co and SCB-0.10Ni/Co interfaces. Ni atoms occupied sublattice sites of Co atoms in CoSn3 phase, which could improve the high-temperature stability of IMCs layer, so the IMCs layer had the strongest thermal stability at the SCB-0.15Ni/Co interface. (C) 2019 Elsevier B.V. All rights reserved.