The Solder Volume Effect on the Creep Behavior of BGA Structure Cu/Sn-3.0Ag-0.5Cu/Cu Joints

The interfacial microstructure and creep behavior of the single BGA structure Cu/Sn-3.0Ag-0.5Cu/Cu joint of different standoff height (i.e., solder volume) values and undergoing isothermal aging were studied by using the lap-shear test. The experimental results show that the thickness of the intermetallic compounds (IMC) layer at the solder/Cu interface increases with decreasing the standoff height of the joints. Both the standoff height and aging treatment influence significantly creep behavior of solder joints. The creep lifetime and minimum steady-state creep strain rate of solder joints exhibit a significant parabolic relationship with the standoff height; and the typical rupture path of BGA structure solder joints changes from the middle of the solder matrix to the position near interface when the standoff height increases. The creep mechanism can be influenced by the standoff height and aging treatment, which changes from a dominant intergranular mechanism to transgranular mechanism as the standoff height increases; after the joints undergoing isothermal aging at 125 degrees C for 1000 h, the creep deformation may occur predominantly by transgranular creep mechanism irrespective of the standoff height. There is no evidence that the existence of Kirkendall voids at the interface of solder joints may influence the creep behavior of solder joints.