Method for equivalent acceleration of JEDEC/IPC moisture sensitivity levels

Abstract

This paper reports a new equivalent test procedure to accelerate JEDEC/IPC moisture sensitivity level testing for plastic surface mount packages. The methodology is developed from moisture diffusion analysis augmented by the use of the critical interface concentration dependency. Equivalent moisture ingress behaviour is shown to be obtainable for any combination of mould compound type and package thickness. The new test procedure, based on testing at 60/spl deg/C/60% RH, reduces the total required moisture soak time for Levels 3-5 by approximately a factor of five compared to the times required for 30/spl deg/C/60% RH testing. An additional benefit of the accelerated test procedure is the introduction of a new moisture level defined as a one month floor life at ambient exposure conditions of 30/spl deg/C/60% RH or less. The required soak time to perform this new moisture level is only 120 hours. Equivalency of the new accelerated test conditions is proven by moisture/reflow experiments on a variety of package types ranging from thin QFPs (TQFPs) and PLCCs to plastic ball grid arrays (PBGAs). Damage response, assessed from inspection for internal cracking and delamination using acoustic microscopy, indicates that the new test procedures are well correlated and considered indistinguishable in most cases.