Bongtae Hana and Dae-Suk Kima
a CALCE, Center for Advanced Life Cycle Engineering, Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20740, USA
Reliability issues associated with moisture have become increasingly important as
advanced electronic devices are nowhere more evident than in portable electronic products.
The transition to the Pb-free solders, which require higher reflow temperature,
makes the problem further exacerbated. Moisture absorbed into semiconductor packages
can initiate many failure mechanisms, in particular interfacial delamination, degradation
of adhesion strength, etc. The absorbed moisture can also result in catastrophic crack
propagation during reflow process, the well-known phenomenon called popcorning. High
vapor pressure inside pre-existing voids at material interfaces is known to be a dominant
driving force of this phenomenon. This paper reviews various existing mechanisms of
water accumulation inside voids. The procedures to obtain the critical hygroscopic properties
are described. Advanced numerical modeling schemes to analyze the moisture diffusion
phenomenon are followed with selected examples. [DOI: 10.1115/1.4035598]
Keywords: moisture diffusion, diffusivity, solubility, hygroscopic swelling, Fick’s law,
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