A thick film package for microwave ICs

A rugged, inexpensive two-port package for mounting a cascade of monolithic microwave ICs was developed. The package consists of two layers of alumina on which silk-screened metal pastes are deposited to form the metal patterns. The RF design of the conductors is described, and the measured transmission properties of the package are given. The key to achieving low insertion loss at microwave frequencies is to use a process that keeps the conductor resistivity as low as possible. It is also important to avoid reflections at discontinuities. It was possible to achieve reasonably smooth insertion loss characteristics and low return loss up to 6 GHz. This required the suppression of parallel-plate waveguide modes and the careful design of the transmission lines for correct characteristic impedance. The suppression of parallel-plate waveguide resonances is achieved by the introduction of via walls along the transmission lines