Advanced moisture diffusion model and hygro-thermo-mechanical design for flip chip BGA package

In the present paper, a comprehensive moisture diffusion model and characterization for encapsulated plastic flip chip (FC) ball grid array (BGA) package are investigated. The transient moisture diffusion analysis described by Fick´s second law is performed to evaluate the overall moisture distribution. Diffusivities in the moisture desorption model are determined under Arrhenius behaviors. Hygroscopic swelling properties of polymeric materials are characterized by using an existing TMA/TGA extraction method. With the so-called ldquothermal-wetnessrdquo analogous technique, finite element analysis (FEA) is developed to evaluate the entire moisture distribution on FC BGA package. The analytical expression for total expansion strain due to hygro-thermo-mechanical coupled effect is implemented using finite element software ANSYS. Finite element predictions reveal the significance of contribution of hygroswelling induced strain. Reliability analysis for FC BGA is performed in accordance with JEDEC standard JESD22-A120. A series of comprehensive experimental works and parametric studies are conducted in this research.