Effectors of high temperature reliability in epoxy encapsulateddevices

摘要

Ball shear testing of devices encapsulated with a variety ofmolding compounds after aging at either 200° C/dry or 158° C/85%R.H. has shown comparable or faster failure rates for the 158° C/85%R.H. parts than for the 200° C/dry parts, in most cases. Slight or nocorrosion of the bond pad was observed under either of these conditions,suggesting that loss of ball shear strength with wet aging (like dryaging) results from chemical weakening of the ball/intermetallicinterface. Molding compounds without Sb₂O₃, andcontaining an ion scavenger performed the best. Electrical testing wasalso carried out on three different types of logic devices with eitherpure aluminum, aluminum+copper, or aluminum+copper+siliconmetallization, built with three different molding compounds and threedifferent die attach materials, under the more traditional hightemperature (190° C) dry conditions (High Temperature Storage LifeTest). The most improved reliability found was for devices with purealuminum pad metallization encapsulated with non-Sb₂O₃ molding compounds of high catalyst level and using a low Cl iondie attach. Among the identified effectors of high temperaturereliability, the presence of moisture and the type of molding compoundused, are the most important