Accelerated Moisture Soak for Moisture Sensitivity Analysis Revisited

This paper assesses the feasibility of a shorter moisture soak when performing Moisture Sensitivity level assessments (MSLA) based on Level 1 (implying unlimited floor life before PCB assembly at the semiconductor user). The standard soak time during preconditioning for Level 1 is 168 h at 85°C/85% R.H. As microelectronics packages in the mobile and personal application space evolve into thinner and smaller products, it is often a matter of conjecture whether a shorter soak time is justified. Based purely on moisture diffusion kinetics, it can be shown that thinner (and smaller) packages will saturate much faster than older generation, thicker packages. This paper demonstrates a novel way to quantify damage response after MSL, to compare the effect of a shorter soak with the standard soak time. Although in some cases, a shorter soak time was shown to give a comparable damage response compared to that after the standard soak time, it is not always the case. However, based on a comparison with older generation, thicker packages, an alternative approach to define a shorter soak time for such packages is proposed.