Sintered silver paste is a popular material for die attachment technology in power electronics. However, using traditional nano-silver paste when fabricating sintered joints has intrinsic material problems that cannot be overcome, such as the high cost of nano-silver particles and their potential health hazards. In this study, a novel micro-silver paste was utilized for sintering and bonding to overcome the limitations of nano-silver paste. Although the micro-silver paste is an excellent candidate to replace nano-silver paste for sintering processes to reduce the potential harm to humans, the oxidation at copper substrates on both sides of the pure silver joint at 300 °C causes mechanical reliability issues in long-term high temperature applications. Therefore, a micro-silver paste was sintered with the addition of indium to address the Cu oxidation problem in this study. It was found that Ag–In intermetallic compounds (IMCs) formed through a transient liquid phase reaction. The results demonstrated that sintered joints comprising Ag–In IMCs and Ag–In solid solution phases could effectively resolve the oxidation issues and significantly enhance the high-temperature reliability. Furthermore, the Ag–In IMCs exhibited excellent mechanical properties, withstanding the thermal stress induced during the thermal cycling test.
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