Effect of Substrates on Fracture Mechanism and Process Optimization of Oxidation–Reduction Bonding with Copper Microparticles
Oxidation–reduction bonding (ORB) is a promising method to achieve Cu-Cu bonding with copper microparticles by a pressureless and low-temperature process. In this study, the influences of Cu substrates with and without Ag-plating and Au-plating on ORB were investigated. The shear strengths of the different bondings were evaluated and the fracture surfaces were observed. The results show that, comparing to original Cu substrates, Ag-plating and Au-plating substrates improved the shear strength of bonding under all conditions, due to the different fracture modes and formation of the intermetallic compound (IMC). Both Ag-plating and Au-plating substrates prevented the formation of oxide film on the substrate, which caused separation at the interface, thereby increasing the shear strength. Au-Cu IMC formed in the Au plating layer; therefore, the bonding with Au-plating was better strengthened. Based upon this observation, an optimized pre-oxidation ORB process with Cu substrates was successfully developed to reduce the process time and improve the bonding strength.
KeywordsOxidation–reduction bonding method substrate formic acid pre-oxidation
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The authors are grateful for the support from China Scholarship Council 201706050096.
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