Measurement of RF properties of glob top and under-encapsulant materials

In this paper we introduce an improved RF dielectric measurement technique based on the Agilent 4291A Impedance Analyzer and 16453A Dielectric Material Test Fixture covering frequencies ranging from 1 MHz to 1 GHz. The measurement structure is a simple parallel plate capacitor with the material under test serving as the dielectric. Obtaining consistent data requires careful sample preparation and accurate alignment between the 16453A electrodes. We describe our procedures for creating flat, polished, metallized samples starting with encapsulant samples in their liquid form. Data for a variety of encapsulants are shown. The technique is readily extendable to solid materials, and we include data for selected samples of LTCC substrates as well as a MAPBGA molding compound.