Prognostics modeling of solder joints in electronic components

We describe a methodology for performing materials-based prognostics for failure in electronic components. The methodology is based on results of a previous research program involving a substantial number of mechanical fatigue experiments and FE analyses investigating solder joint integrity. The component considered here is a gull-wing lead power supply chip on a DC/DC voltage converter PWB assembly. As a first step, three-dimensional finite element analyses are performed to determine macrostrains in the solder joint due to thermal or mechanical cycling of the component. We consider strains due to lead bending resulting from the thermal mismatch of the board and chip and those resulting from local thermal mismatch between the lead and the solder as well as between the board and the solder. In the second step, the macrostrains are used to set boundary conditions for a probabilistic micromodel that can explicitly simulate initiation and growth of cracks in the microstructure of the solder joint. Based on the growth rate of the cracks in the solder joint, estimates can be made of the cycles to failure for the electronic component. Here, we describe the first step of the methodology