Fatigue Life Predictive Model and Acceleration Factor Development for Decoupling Capacitors

Decoupling capacitors are increasingly being used to decrease signal latency and to increase the speed and functionality of microprocessors used in ASICs and Server applications. SnAgCu (SAC) based solder joints are typically used to attach the capacitors to the organic laminate. Fatigue failure of the solder joints due to CTE mismatch between the capacitor and the laminate and due to proximity of the capacitor to the chip is a cause of concern. In this paper we have developed a predictive model and an Arrhenius type acceleration factor that can be used to determine the mean number of cycles for capacitor failure during any thermal cycling conditions including field-use conditions due to solder joint fatigue. The predictive model and the acceleration factor was developed using experimental data from test vehicles with 0306 and 0508 decoupling capacitors that were attached to the laminate using either SAC305 or SAC105 solder and were subjected to a wide range of thermal cycling conditions from harsh to benign.