Abstract
A microwave method to measure moisture in encapsulant resin of IC packages was studied. A network analyzer was used to generate a continuous microwave signal fed to an open-ended coaxial line sensor and to measure the amplitude of effective reflection coefficient at the sensor aperture. The coaxial line sensor acted both as a source and receiver of microwave signal, which was transmitted into the encapsulant resin and reflected at the surface of a metallic plate place behind the resin. To evaluate the moisture of encapsulant resin, fundamental experiment was carried out for epoxy resin samples with different moisture contents introduced in various environmental conditions. The relationship between the amplitude of effective reflection coefficient and the moisture content of the encapsulant resin was found, and the evaluation equation was built. The present technique indicates a possibility to determine the moisture in IC packages directly without drying and weighing the package.
