Volume 7, Issue 5 (May 2010)
Loading Mixity on the Interfacial Failure Mode in Lead-Free Solder Joint
In this paper, single solder joints (SSJs) were subjected to moderate speed loading (5 mm/s) in different directions, from pure tensile mixity mode to pure shear. Fracture surfaces from different loading directions were examined both experimentally and numerically. The intermetallic compound (IMC) is formed between the solder alloy and the Cu pad, and the failure typically occurs at or near the solder/IMC/Cu interfaces of the board side. Pure tensile loading typically leads to interfacial fracture along the IMC/Cu interface. Mixity mode loading usually results in a mixture of interfacial and cohesive failure with damage propagating in a zigzag fashion between the solder/IMC interface and the solder alloy. Loading with higher shear component tends to result in more cohesive failure of the solder alloy near the solder/IMC interface. Under pure shear loading, failure is almost always cohesive within the solder alloy near the solder/IMC interface.