A novel technique for modeling solder joint failure during system level drop simulations

This paper will describe a newly developed solder model that can accurately predict solder failure during a full product level drop. Currently, it is not feasible to include a detailed model of the solder ball assembly in a system level drop. Simple calculations show that the mesh count would exceed 10 million nodes just for the solder balls on a typical cellular phone printed circuit board! This has lead to the investigation of various techniques to replace the detailed solder joint model with a computationally simple form. The most promising approach is using an equivalent beam element, whose properties are generated from a detailed model. To ensure the mechanical response of the solder, experimentally obtained rate dependent material properties for lead-free solder data are used, along with a failure criterion based upon the pad finish and solder ball chemistry. Simulations of dynamic 4-pt bend testing have validated this technique and bounded the failure criterion consistent with the literature. Application of the modeling technique has allowed for solder ball failure prediction in fully populated cellular radio drop models and these results will form the basis of this paper