Morphology of the water in plastic electronic packaging materials

The absorption and desorption processes of moisture in plastic material were studied. The diffusion coefficient and the saturate concentration were determined by experiments and simulation results with Fick law. The water molecules inside plastic material were bonded with polymers by the hydrogen bond in the micro-voles formed by the polymer chain. Under the saturate concentration, the moisture density in effective volumes is 100 times greater than vapor density in standard state, and is 8 % the density of liquid water. The water in plastic material is a special liquid. The delamination happens when liquid and gas states coexist. There were water and vapor in the micro-voles when the moisture concentration is high enough. The strength of the interface between the plastic material and the die was reduced by the bonding of water molecule with polymers, which caused the delamination.