Joining delicate electronic components for high-temperature applications is challenging. Regular soldering with lead-free or lead-based materials is typically not suitable for high-temperature applications due to their low melting points. Using off-eutectic compounds for joints offer an easy and gentle process creating joints that can be formed at a lower process temperature than the final operation temperature. Microstructural evolution near the eutectic melting point is key to be able to form reliable joints. A layered Au/eutectic Au-Ge/Au structure was used to form Au-rich off-eutectic Au-Ge joints. Columnar-like structures of primary \( \alpha \)-phase (Au) protruded through a Ge-rich off-eutectic Au-Ge mixture at the center of the joint. These structures connect the joined pieces with a single solid phase with a melting point of ca. 1064 °C. The microstructure coarsened when exposed to temperatures between 300 °C and 380 °C, i.e., near the eutectic melting point at 361 °C. Ge diffused and accumulated along grain boundaries between Au grains. Annealing above the eutectic melting point, Ge rapidly diffused and formed larger colonies of pure Ge surrounded by a Au matrix. This accords well with our previously published results demonstrating shear strength capacity of similar joints at temperatures well above the eutectic temperature.

中文翻译：

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非共晶Au-Ge接头的微观结构：高温接头

连接用于高温应用的精密电子元件具有挑战性。用无铅或铅基材料进行的常规焊接由于熔点低，通常不适合高温应用。对接头使用非共晶化合物可提供一种轻松而温和的工艺，从而可以在比最终操作温度更低的工艺温度下形成接头。共晶熔点附近的微观结构演变是能够形成可靠接头的关键。使用分层的Au /共晶Au-Ge / Au结构形成富金的非共晶Au-Ge接头。主\（\ alpha \）的柱状结构相（Au）通过在接头中心的富含Ge的非共晶Au-Ge混合物突出。这些结构将连接的零件与熔点约为1的单个固相连接。1064°C。当暴露于300°C和380°C之间的温度（即接近361°C的低共熔熔点）时，显微组织会粗化。Ge沿着Au晶粒之间的晶界扩散并积累。在共晶熔点以上退火时，Ge迅速扩散并形成被Au基质包围的较大的纯Ge菌落。这与我们先前发表的结果相吻合，该结果证明了在高于共晶温度的温度下类似接头的剪切强度能力。