Characterization Of Creep Behaviours Of Soldered Joints Of A Nano-Composite Solder And Of Lead-Free Sn-Ag-Bi And Sn60Pb40 Solders

摘要

Creep performance of soldered connections is significant to the reliability evaluation and lifetime prediction of microelectronic and optoelectronic/photonic packaging systems. In this work, creep behaviours of a tin-based composite solder reinforced by nano-sized metal particles and a lead-free Sn-Ag-Bi solder were characterized, with a comparison to Sn60Pb40 solder. The results show that the nano-composite solder has much better creep resistance than Sn60Pb40. The lead-free Sn-Ag-Bi solder has superior creep performance to both Sn60Pb40 and nano-composite solders. The creep fractography analysis shows that a progressive shear deformation occurred as the main creep fracture mechanism. Sn60Pb40 solder joints deform dominantly by transgranular sliding, while Sn-Ag-Bi and nano-composite solder joints creep by intergranular mechanism through grain boundary sliding and boundary voids growth. The mechanism of enhancing the creep resistance of nano-composite solder joints is that uniformly dispersed nano-sized particulates provide effective resistance by impeding grain boundary sliding and dislocation movement, besides the alloying effect of increasing elasticity modulus of the solder.