Accelerated Moisture Sensitivity Test Methodology for Stacked-Die Molded Matrix Array Package

The existing IPC/JEDEC of moisture/reflow sensitivity classification determines the time of accelerated equivalent soak by the equivalency of moisture concentration at the critical interface with the standard sensitivity test. This paper proposes a new methodology of accelerated moisture sensitivity test based on the equivalency of both local moisture concentration and overall moisture distribution for stacked-die molded matrix array package (MMAP). The new methodology can ensure the same failure rate of cracking/delamination by the equivalency of local vapor pressure, interfacial adhesion as well as the thermo- and hygro-stresses. Finite element analysis (FEA) is applied for moisture diffusion and vapor pressure analysis under the conditions of 30degC/60%RH and 60degC/60%RH, respectively. At 70 hours at 60degC/60%RH, both the local moisture concentration at critical interface and overall moisture distribution of package become identical with that at 216 at 30degC/60%RH, indicating that 70 hours is the equivalent soak time compared to the standard MSL-3 for this type of MMAP packages. Such an equivalency of the new accelerated test conditions is proven by moisture/reflow experiments under various soak times at 30degC/60%RH and 60degC/60%RH. Damage response assessed from inspection for internal cracking/delamination indicates that the accelerated test procedures are well correlated and considered indistinguishable in terms of failure rate.