Extreme temperature change has generally been the great challenge to spacecraft electronic components, particularly in long, periodic, deep-space exploration missions. Hence, researchers have paid more attention to the reliability of component packaging materials. In this study, the microstructure evolution on the interface of Cu/Ni/Au/Au-12Ge/Au/Ni/Cu joints, as well as the effects of extreme thermal shock on mechanical properties and the fracture mode in the course of extreme thermal changes between −196 and 150 °C, have been investigated. Results revealed that the interface layers comprised of two thin layers of NiGe and Ni₅Ge₃ compounds after Au-12Ge solder alloy was soldered on the Au/Ni/Cu substrate. After extreme thermal shock tests, the microstructure morphology converted from scallop type to planar one due to the translation from NiGe to Ni₅Ge₃. Meanwhile, the thickness of interface layer hardly changed. The shear strength of the joints after 300 cycles of extreme thermal shock was 35.1 MPa, which decreased by 19.61%. The fracture location changed from the solder to solder/NiGe interface, and then to the interface of NiGe/Ni₅Ge₃ IMC layer. Moreover, the fracture type of the joints gradually transformed from ductile fracture mode to brittle mode during thermal shock test. Simultaneously, the formation and extension of defects, such as micro-voids and micro-cracks, were found during the process of thermal shock due to the different thermal expansion coefficient among the solder, interface layer and substrate.

中文翻译：

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极端热冲击对Au-12Ge / Au / Ni / Cu焊点组织和力学性能的影响

极端的温度变化通常是航天器电子组件面临的巨大挑战，特别是在长期，周期性的深空探测任务中。因此，研究人员更加关注组件包装材料的可靠性。在这项研究中，Cu / Ni / Au / Au-12Ge / Au / Ni / Cu接头界面的显微组织演变，以及极端热冲击对极端热过程中力学性能和断裂模式的影响研究了−196至150°C之间的变化。结果表明，界面层由NiGe和Ni ₅ Ge ₃的两个薄层组成将Au-12Ge焊料合金焊接到Au / Ni / Cu基板上后，会产生化合物。经过极端的热冲击试验，由于NiGe向Ni ₅ Ge ₃的转化，组织形态从扇贝形转变为平面形。同时，界面层的厚度几乎不变。300次极端热冲击后，接头的剪切强度为35.1 MPa，下降了19.61％。断裂位置从焊料变为焊料/ NiGe界面，然后变为NiGe / Ni ₅ Ge ₃界面IMC层。此外，在热冲击试验中，接头的断裂类型从韧性断裂模式逐渐转变为脆性模式。同时，由于焊料，界面层和衬底之间的热膨胀系数不同，在热冲击过程中发现了缺陷的形成和扩展，例如微孔和微裂纹。