Effect of Ge addition on wettability, copper dissolution, microstructural and mechanical behavior of SnCu–Ge solder alloy
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This paper explores the effects of Germanium (Ge) addition on the wetting behavior, copper dissolution, IMC formation, microstructure and mechanical behavior of SnCu alloy. Static copper dissolution was conducted as a function of contact time and in the temperature range of 260–300 °C. The results show that the Ge doped alloy has the lowest copper dissolution rate compared to SnCu, SAC305, and very much comparable with SnPb solder thus making it suitable alloy for the wave soldering process. Two solderability standards measurement (JIS vs. IPC) have been executed on different surface finishes such as OSP, ENIG, ImAg commonly used in industrial soldering process. The results showed that addition of Ge significantly improves the wetting/spread performance for all the surface finishes (ENIG, OSP and ImAg). Contact angles range from 17°–30°, the lowest contact angles being observed on ENIG surface. Microstructural analysis showed Ge addition refine the grain structure of SnCu–0.01Ge alloy. A thin IMC layer was observed, and IMC growth was not significant after multiple reflows as compared to Sn–Cu alloy. Similarly, Ge addition increases the hardness value due to uniform microstructure of SnCu–Ge alloy. The tensile testing results also showed an increase in tensile strength and tolerable ductility.
This research was supported by Kester R & D, material science division. The authors thankful to ITW Tech Center and Buehler for sample preparation and analysis.
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