Influence of diamond additions on lead-free Sn-Zn-Bi solder-alloys

In this work, diamond nano-particles doped Sn-8Zn-3Bi solder alloys have been studied. The microstructure and the interfacial reactions of the plain solder joints and solder joints containing diamond nano-particles were investigated under current density of 5×10³ A/cm² at temperature of 100°C with Cu pads on daisy chain type ball grid array (BGA) substrates. It was found diamond nano-particles doped in solder joints refined the microstructure and retarded the formation of Cu5Zn8 intermetallic compounds (IMCs). The shear strength of solder joints containing diamond nano-particles exhibited higher value than that of plain solder joint. In addition, the fracture surface of doped solder joints appeared ductile behavior with very rough dimpled surfaces. DSC analyses of plain and doped solders revealed the onset and melting temperatures of solder alloys with diamond additions kept nearly unchanged, indicating its potentially viable applications and benefits.