Characterization of the isothermal solidification process in the Ni/Au–Ge layer system

Abstract

The eutectic Au28Ge (at.%) solder alloy in combination with Ni substrates or Ni coatings is interesting for applications in transient liquid phase (TLP) bonding. To achieve sound joints with high re-melting temperatures, it is necessary to gain profound knowledge about the joining process. In this work, the isothermal solidification behavior in the Ni-Au28Ge (at.%) system was analyzed by means of microstructure evolution and time to complete solidification. In short-time annealing experiments the early stage of the reaction (\300 s over liquidus temperature) was investigated. It was observed that a continuous layer of Ni 5 Ge 3 forms at the substrate-solder interface before scallop-like NiGe grains start to grow as solidification proceeds. Cyclic differential scanning calorimetry measurements were applied to estimate the time to complete solidification. Solidification was completed after less than 1 h in the Ni-Au28Ge (at.%) system, which enables comparably short processing times for TLP bonding.

Effects of Extreme Thermal Shock on Microstructure and Mechanical Properties of Au-12Ge/Au/Ni/Cu Solder Joint

“…Based on Figure 6b and the EDS analysis in Table 2, a continuous layer of Ni5Ge3 was detected at the interface of asproduced joint. There was also a continuous layer of NiGe phase with a scallop-like morphology adjacent to the Ni5Ge3 phase, which was similar to the research reported by Weyrich et al [8,27,28]. There were no voids or other defects at the interface, which meant that the solder joint had complete structure.…”

Cu3Sn-microporous copper composite joint for high-temperature die-attach applications

“…Although high-Pb solder alloys are still in use at present, they would not last long in the future because Pb is harmful to the environment and people’s health (Liu et al , 2015). Au-containing solder alloys such as 80Au-20Sn,Au-28Ge have high melting point, eximious electrical and thermal conductivity and corrosion resistance; however, the high price of gold limits their widespread application (Huang et al , 2018; Weyrich and Leinenbach, 2015). Zn-based solders have high melting point, but the corrosion resistance of Zn-based solders is very poor (Haque et al , 2012).…”