Effect of Time-Dependent Bulk Modulus on Reliability Assessment of Automotive Electronic Control Unit

Time-dependent bulk modulus of EMCs is measured using an embedded fiber Bragg grating (FBG) sensor while subjecting EMCs to hydrostatic pressure. The time-dependent behavior of the bulk modulus, especially around the glass transition region, is discussed. Then, an LVE based numerical modeling is employed to quantify the effect of time-dependent bulk modulus on the internal stresses of encapsulated automotive ECU units subjected to the solder reflow profile. The results are compared with the case of the time-independent bulk modulus, and the effect on the reliability assessment is discussed.