Development of a simple cup method for water vapor transmission rate measurements under high-temperature conditions

A novel method has been studied to measure high-temperature water vapor transmission rates (WVTRs) for sealing materials such as epoxy encapsulants. Sealing materials are widely used as electronic components and must be moisture resistant under the damp heat test conditions for electronic components, e.g., 60 °C and 85 °C. To prevent samples from damage during high-temperature measurements using the conventional cup method, we built a new cup unit with a pressure-adjusting mechanism. This new cup is used to measure WVTRs without damaging the thin epoxy encapsulant membranes (thicknesses of 120-220 μm). Arrhenius plots of the WVTRs for epoxy encapsulants measured by using the new cup exhibit linear relationships between temperatures of 25-85 °C.