Microstructure, interfacial reactions and mechanical properties of Co/Sn/Co and Cu/Sn/Cu joints produced by transient liquid phase bonding
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In this paper, the wettability and growth behaviors of interfacial intermetallic compounds (IMCs) in the Sn/Co and Sn/Cu liquid/solid couples were comparatively investigated. In situ tensile tests were conducted to evaluate the mechanical properties of the Co/Sn(IMCs)/Co and Cu/Sn(IMCs)/Cu joints. The wettability of Sn on Cu substrate was better than that of Co substrate. The lath-like CoSn3 IMCs limited the improvement of wettability of Sn on Co substrate, even if the soldering temperature was increased. The Sn/Co couples showed an acceptable wettability for electronic application. During liquid aging, the rapid growing interfacial CoSn3 were controlled by the combination of chemical reaction and atomic diffusion. Grain boundary diffusion should be responsible for the growth of Cu6Sn5 in the Sn/Cu liquid/solid couples. The tensile strength and elongation of the Co/CoSn3/Co joints were basically equal to that of the Cu/IMCs/Cu full IMCs joints. Interfacial IMCs cracks were more likely to occur in the joints fabricated by Co substrate. The Co/CoSn3/Co sandwich structure can be fabricated within a remarkable short period of time at low temperature without pressure.
The authors would like to acknowledge the financial support by the National Natural Science Foundation of China (51004039) and the Opening Project of Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology (ASMA201602).
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