Interfacial reaction, microstructure and hardness between graphene-coated Cu substrate and SAC305 solder doped with minor Ni during isothermal aging

Abstract

This study investigated the influences of Cu, high temperature-treated Cu (H-Cu) and graphene-coated Cu (G-Cu) substrates on interfacial reaction, microstructure and hardness of Sn-3.0g-0.5Cu (SAC305) solder alloy. Intermetallic compound (IMC) layer evolution and mechanical property of Sn-3.0g-0.5Cu-0.3Ni (SAC305-0.3Ni) solder joints were also studied under different aging duration. A continuous scallop-like IMC layer was observed at SAC305/Cu, SAC305/H-Cu, SAC305/G-Cu interfaces during reflow and isothermal aging. After adding Ni in the SAC305-0.3Ni solder alloy, the roughness of IMC layer on Cu, H-Cu substrates increased. In contrast, the addition of Ni had a limited impact on the roughness of IMC layer on G-Cu substrates. The total thickness of IMC layer grew as aging time increases, proportionated to the square root of aging duration. The addition of Ni in the solder alloy promoted the growth of IMC layer on Cu and H-Cu substrates, but it was restrained on G-Cu substrate. The amount of the IMC phases in SAC305 and SAC305-0.3Ni solder bulks on the three substrates increased significantly as aging time prolonged. Thus, the hardness of SAC305 and SAC305-0.3Ni solder bulks on the three substrates rose. The addition of Ni in the solder bulks on the three substrates sharply enhanced the formation of [Formula: see text]-Sn phases and increased the quantity of the IMCs. Consequently, the hardness of SAC305-0.3Ni solder bulks was higher than that of SAC305 solder bulk on the three substrates under same aging condition. In addition, the graphene-coated layer on G-Cu substrate could improve the hardness of SAC305 and SAC305-0.3Ni solder bulks.