Microstructure and hardness of SAC305-xNi solder on Cu and graphene-coated Cu substrates
This study investigated the interfacial reaction, the microstructure, and the hardness of the SAC305-xNi solder on both Cu and graphene-coated Cu (G–Cu) substrates. The experimental results indicate that the increase of Ni content in the solder leads to the roughness of the (Cu, Ni)6Sn5 IMC layer on Cu. In contrast, the growth of the (Cu, Ni)6Sn5 interfacial IMC, which results from increasing Ni addition, is significantly suppressed on G–Cu substrates. As the concentration of Ni ranges from 0 to 0.2 wt%, the microstructure of the solder bulks on Cu substrates shows slight changes. The hardness of the solder bulks in SAC305-Ni/Cu is similar to that in the SAC305/Cu solder joint. The amount of β-Sn rises and the eutectic area shrinks due to increasing Ni addition in the solder bulks on G–Cu substrates. Therefore, the solder bulks in the SAC305-Ni/G–Cu show lower hardness than that in the SAC305/G–Cu solder joint.
This work is supported by National Natural Science Foundation of China (No. 51604090), Natural Science Foundation of Heilongjiang Province (No. E2017050), and University Nursing Program for Young Scholars with Creative Talents in Heilongjiang Province (UNPYSCT-2015042).
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