Microwave Characterization of a Thick Film System for Hybrid Packaging Applications

Abstract

Abstract Thick film material systems for hybrid applications have existed for many years and have provided the ability to create high density interconnects in industries such as consumer, military, telecommunications and automotive electronic devices. Despite their breadth of applications, thick film hybrid circuits are rarely utilized for microwave/millimeter-wave packaging applications. In this work, the DuPont™ QM44 thick film dielectric is characterized up to 40 GHz. Test samples to characterize this thick film system consisted of the screen-printed QM44 multilayer dielectric and QG150 gold thick film conductor and vias on top of a 96% alumina substrate. Three different fabrication methods were used in the fabrication of the test samples to illustrate the effect of processing techniques on material loss properties, with the conductor lines formed through standard screen printing, chemical etching, and laser ablation. Laser ablation is a technique recently utilized to form transmission line features in low temperature cofired ceramic (LTCC) circuits [1] to increase dimensional precision when compared to standard screen printing. S-parameter measurements of microstrip transmission lines demonstrate a system loss at 30 GHz of approximately 0.8 dB/cm for chemical etching, 0.9 dB/cm for laser ablation, and 1.0 dB/cm for screen printing. Through careful design and good processing, acceptable microwave performance of the QM44 thick film system can be achieved up to 40 GHz.