Vulnerability of Copper Pad in BGA Solder Interconnects Under Temperature Cycling

SAC305 solder interconnects in ball grid array (BGA) packages can experience failure by a combination of cracks in solder alloy and copper pad when the packages are subjected to different sequential combinations of loading conditions, such as temperature cycling and isothermal harmonic vibration at low temperature. To understand the relative risk of these two competing failure models, an accurate assessment of the stress fields in the joint is important. The stress fields depend on the local solder grain structure in the joint, since each grain is highly anisotropic. Therefore, this study uses grain-scale finite element modeling to provide a preliminary understanding of the impact of local grain orientation in the solder on the vulnerability of crack propagation in the copper pad in the critical solder ball of BGA package.