Abstract Au-12Ge(wt.%) eutectic solder is widely used in electronic packaging thanks to its good electrical conductivity, solderability, and chemical stability. To investigate the stability of Au-12Ge solder during high-temperature service, the effects of different isothermal aging conditions on the microstructure and performance of Au/Ni(P)/Kovar substrate after soldering were investigated. Solder joints produced at 400 °C for 1 min showed excellent wetting behavior with NiGe/Ni5Ge3/Ni3(P,Ge) intermetallic layers formed at the interface. The thickness of generated interfacial intermetallic compounds was estimated to only 1.56 μm due to the amorphous nature of Ni-P coating that hindered the diffusion of Ni atoms. As aging increased with time and temperature, the interfacial intermetallic compounds grow further, leading to deterioration and failure of solder joints. The growth mechanism of interfacial intermetallic compounds was then examined, and activation energy was estimated to 95.4 kJ/mol. In turn, shear strength of solder joints declined and fracture mode became brittle as aging time and temperature increased. Meanwhile, fracture position evolved from IMC layer to Ni-P layer. At aging temperatures above 290 °C, Ni-P layer showed crystallization transition to porous Ni3P, leading to formation of holes and cracks, and resulting in exfoliation of coating with Kovar substrate.

中文翻译：

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等温时效对Au-12Ge/Ni(P)/Kovar焊点界面微观结构演变和剪切行为的影响

摘要 Au-12Ge(wt.%)共晶焊料具有良好的导电性、可焊性和化学稳定性，被广泛应用于电子封装领域。为了研究 Au-12Ge 焊料在高温使用过程中的稳定性，研究了不同等温老化条件对 Au/Ni(P)/Kovar 基板焊接后的微观结构和性能的影响。在 400 °C 下生产 1 分钟的焊点显示出优异的润湿行为，在界面处形成 NiGe/Ni5Ge3/Ni3(P,Ge) 金属间化合物层。由于 Ni-P 涂层的无定形特性阻碍了 Ni 原子的扩散，所生成的界面金属间化合物的厚度估计仅为 1.56 μm。随着老化时间和温度的增加，界面金属间化合物进一步生长，导致焊点劣化和失效。然后检查界面金属间化合物的生长机制，活化能估计为 95.4 kJ/mol。反过来，随着老化时间和温度的增加，焊点的剪切强度下降，断裂模式变脆。同时，断裂位置从 IMC 层演变为 Ni-P 层。在高于 290 °C 的时效温度下，Ni-P 层表现出结晶转变为多孔 Ni3P，导致孔洞和裂纹的形成，并导致 Kovar 基体涂层的剥落。同时，断裂位置从 IMC 层演变为 Ni-P 层。在高于 290 °C 的时效温度下，Ni-P 层表现出结晶转变为多孔 Ni3P，导致孔洞和裂纹的形成，并导致 Kovar 基体涂层的剥落。同时，断裂位置从 IMC 层演变为 Ni-P 层。在高于 290 °C 的时效温度下，Ni-P 层表现出结晶转变为多孔 Ni3P，导致孔洞和裂纹的形成，并导致 Kovar 基体涂层的剥落。