Creep lifetime prediction of solder joint for heat sink assembly

The heat sink assembly in a server station is anticipated to creep to fail at the solder joint under a constant load and temperature condition. To predict the lifetime of solder joint in the system, accelerated creep-rupture tests are conducted. Three loads of 4, 6, and 8 kg and temperatures of 35, 55, and 65 °C are selected for the tests. Larson–Miller model is adopted for the lifetime prediction, which requires tested lifetime data and stress analyses for the solder joint. An FE model for the stress analyses is developed and validated experimentally. Analyzed Larson–Miller constants show different tendency in the 8 kg load cases. Extensive failure analyses on the failed solder joints reveal the transition of failure mechanism at 8 kg load cases from the intergranular to the transgranular creep. Using only the validated test data of 4 and 6 kg load cases, creep lifetime prediction model for the solder joint in the heat sink assembly is developed and applied for a field condition.