Microstructure, thermal analysis and damping properties of Ag and Ni nano-particles doped Sn–8Zn–3Bi solder on OSP–Cu substrate

Abstract

This paper investigates the effects of reaction time and temperature on the morphology and growth mechanism of intermetallic compound (IMC) layers of plain Sn–8Zn–3Bi solder and solders containing Ag, Ni nano-particles on Organic Solderability Preservative (OSP)–Cu substrate. At the interface of the plain Sn–8Zn–3Bi solder/OSP–Cu system, a scallop-shaped Cu5Zn8 IMC layer was clearly observed. However, after adding Ag nano-particles into the Sn–8Zn–3Bi solder, an additional island-type AgZn3 IMC layer was found at the top surface of the scallop-shaped Cu5Zn8 IMC layer. Moreover, in the Sn–8Zn–3Bi–0.5Ni solder/OSP–Cu system, a ternary (Cu, Ni)–Zn IMC layer was well adhered at their interfaces. Furthermore, in solder ball regions a needle-shaped α-Zn and spherically-shaped Bi phases were clearly observed in the β-Sn matrix of plain Sn–8Zn–3Bi solder. However, in the solder alloys containing Ag and Ni nano-particles an additional very fine AgZn3 IMC particles for Ag doped solder and Zn–Ni IMC particles for Ni doped solder was uniformly distributed as well as the needle-shaped α-Zn and spherically-shaped Bi phases in the β-Sn matrix. These IMC layer thicknesses were increased with the reaction time and temperature. However, after the addition of the Ag and Ni nano-particles, the IMC growth behavior was slower than that of the plain solder system.Damping capacity of plain Sn–8Zn–3Bi solder alloy and solder alloys containing Ag, Ni nano-particles were measured by dynamic mechanical analyzer (DMA). The damping capacity of composite solder alloys exhibited higher values than that of plain Sn–8Zn–3Bi solder alloy which is essential to suppress the mechanical vibration and wave propagation. Furthermore, the composite solder alloys doped with Ag, Ni nano-particles improved the oxidation resistance than that of plain Sn–8Zn–3Bi solder alloy by the formation of fine Zn containing IMC particles which block the penetration of vapor and oxygen into the solder matrix.