Stabilized Interfacial Intermetallic Compound Evolution in Ni-Coated Carbon Fiber Reinforced Sn-3.5Ag Composite Solder Joint

In this work, a novel composite solder was fabricated by mechanically incorporating Ni-coated carbon fiber (Ni-CF) into the Sn-3.5Ag solder paste in an effort to improve the overall service capability, where the intermetallic compound (IMC) formation and growth is a fundamental issue for consideration. General findings indicated that the addition of Ni-CF did not significantly impact the processing properties of the base alloy, such as melting temperature and wettability, when the reinforcement fraction was less than 2 wt.%. Isothermal aging tests were carried out to study the formation and growth of interfacial IMC layers between the composite solder and Cu substrate. The Ni-CF near the Cu substrate was found to act as the nucleation barrier of the interfacial (Cu, Ni)6Sn5 phase during reflow soldering to prevent fast Cu-Sn reaction. Moreover, the addition of 1 wt.% Ni-CF was believed to be more effective to restrict and reduce the subsequent growth rate of the IMCs during solid-state aging due to the initial formation of a thicker (Cu, Ni)6Sn5 layer after reflow.