Moisture diffusion modeling and application in a 3D RF module subject to moisture absorption and desorption loads

Moisture induced interfacial delamination failures are often found in a microelectronic package within die attach epoxy and laminate substrate during moisture sensitivity reliability test. In this paper, a piecewise normalization approach is proposed to simulate moisture sensitivity test with both preconditioning absorption and reflow desorption phases. A bi-material model with analytical solutions is used to validate the modeling approach. It is shown that the moisture concentration using proposed modeling approach can be correlated well with analytical solutions in both preconditioning absorption and reflow desorption phases. The modeling approach then has been applied to a 3D RF module, a typical system in package, to effectively obtain distribution of moisture concentration which is one of key parameters in calculation of moisture induced hygroscopic stress and vapor pressure induced stress and thus the moisture induced risk can be quickly assessed in early product development for optimal design to achieve a goal of design for reliability.