Interfacial Reliability between Gold-Germanium solder and Au/Ni-metallized Kovar

Abstract

On a microscopic scale, the reliability of a solder joint depends on the structure of the interfacial intermetallic compound formed by the interfacial reaction between the solder and the pad. In this paper, the reliability of solder joints is characterized by the interfacial reaction of gold-bismuth alloy solder joints and the change of microstructure with environment. The interface characteristics of AuGe alloy solder and eutectic sintering of Ni/Au pads with different gold thickness are studied. The solder wettability of AuGe alloy solder on common pads such as Cu and Ni and its soldering interface characteristics are summarized. The results of slicing analysis showed that after eutectic soldering, the Au-phase of the thick gold sample was cooled to form an irregular solder joint layer, and the thickness of the Au layer was reduced by about 50-60%. The Au layer of the thin gold sample was all. It disappears and a very thin layer of Ni-rich NiGe compound is formed at the interface. The experimental results show that the thick Au layer sample does not show the diffusion of Ni to the solder layer and the formation of NiGe compound. The thick gold layer acts as a barrier layer. In the thin gold sample, Ni slowly forms a NiGe compound with Ge through interdiffusion. In use, the solder layer will evolve through elemental diffusion, etc., transforming the entire solder layer into an intermetallic compound containing a multilayer structure such as an oxide layer, a P-rich layer, a NiGe layer, and an AuCuGe alloy layer, which reduces the solder joint strength and seriously affects the soldering. Layer reliability. This indicates that the intermetallic compound (IMC) is mainly formed by interfacial chemical reaction during the welding process; it mainly evolves in the form of elemental diffusion during the service.