A highly integrated millimeter-wave active antenna array using BCB and silicon substrate

A simple and inexpensive packaging scheme is implemented in the design of an active antenna array module. The package consists of etched wells in a silicon wafer in which the components of the module are placed. A benzocyclobutene (BCB) film covers the components and serves as a substrate for interconnections. Prefabricated metallic bumps on the components are used for connection through the BCB film, eliminating the need for wire bonds. Aluminum coating of the silicon wafer isolates the lossy substrate from the millimeter-wave circuitry. This packaging process is applied to form an array of four cavity-backed patch antennas and then integrate it with a down-converter. The resulting active antenna array down-converts a 39-GHz received signal. The only off-wafer interconnects are for the 16-GHz local-oscillator input and a 7-GHz IF output. The effect of the packaging on the down-converter is described and important design features are noted. A detailed loss analysis is conducted based on measurements of the array performance.