Effect of stand-off height on the reliability of Cu/Sn-4.8Bi-2Ag/Cu solder joint

This study investigates intermetallic compound (IMC) growing behavior at different stand-off heights (SOH) in miniature Cu/Sn-4.8Bi-2Ag/Cu solder joints. The solder joints with SOH of 10, 20, 50 and 100 mum will be studied, and the microstructures and compositions will be discussed. Meanwhile the tensile strength and the fracture mode of Sn-4.8Bi-2Ag solder joints will be also studied. The results show that Bi appears as particles spreading over the bulk of the solder joint, which will increase the strength of the solder joint. It is also found that the content of the IMC layer increases as the SOH reduces. The SOH of the solder joint plays an important role in the tensile strength. Tensile strength of the solder joint decreases as the SOH reduces, which correlates with the change of microstructures and compositions in the solder joints. The fractured path of the solder joint transfers from the bulk of the solder joint to the interface between IMC and solder, and the fracture mode tends to be brittle fracture.