Interfacial reaction, microstructure and mechanical properties of Sn58Bi solder joints on graphene-coated Cu substrate

Abstract

The wettability, interfacial reaction, microstructure and hardness of Sn58Bi (SnBi) solder paste on Cu, high-temperature Cu (H-Cu) and graphene-coated Cu (G-Cu) were investigated in this study. Experimental results indicate that the wettability of Sn58Bi solder on G-Cu is higher than that on Cu and H-Cu substrates. The thickness of the interfacial intermetallic compound (IMC) on Cu, H-Cu and G-Cu substrates increased during aging. The IMC on G-Cu showed the lowest growth rate due to the interfacial diffusion suppressed by the graphene-coated layer. Large dendrite β-Sn phase formed and grew up in the solder bulks on Cu and H-Cu substrates. In contrast, the dissolved graphene inhibits the growth and segregation of β-Sn in the solder bulk on G-Cu during aging. The solder bulk on this substrate shows more uniform microstructure and lower hardness than that on the others.