Material compatibility and dielectric properties of co-fired high and low dielectric constant ceramic packages

Recent trend in integrated ceramics is to have a 3-dimensional integration of passive components onto the low permittivity dielectric substrate to achieve a monolithic multilayer ceramic (MMC) substrate. MMC substrates offer significant gain in both circuit density and device hermiticity leading to increased reliability and low cost packages. Low-temperature glass-ceramic based low K tapes have been demonstrated to have good compatibility with silver metallization and resistor inks. To push the level of passive component integration one step forward, we studied the materials compatibility and co-firing aspects of low K tapes with high dielectric constant Pb-based relaxer materials. Li salt addition to high K ceramic tape was found to be effective in reducing the sintering temperature to match with that of low K tape. It also improved the dielectric properties and, most importantly, gave a wider processing window for the high K material. This paper describes the optimization of the high K tape casting process such as slurry preparation, rheology, solid content, tape release, lamination, and shrinkage matching with the low-K substrate. This paper also demonstrates the successful integration of high and low K materials.