Using Microwave Coupled Resonator Filters to Characterize Thick Film Interconnects for Highfrequency Signal Propagation

Abstract

All interconnect mediums are expected to conduct signals with a minimum amount of corruption. This is particularly important when the signals contain high frequency fundamental or harmonic information. For microwave applications or very densely packed circuit modules, thin film conductors are typically the interconnect medium of choice. Alternatively, thick film interconnects have served well for many applications. The question this work seeks to answer is this. With the improved thick film material sets and 300 to 400 mesh screen printing procedures available today, at approximately what frequency or conditions should the thick filmhhin film tradeoff decision be reconsidered? This question is especially poignant for applications in which circuit packing density is not the main driver. Stated another way, to what frequency regime do the imperfections in the interconnect pattern profile introduced by the screen printing operation, or material properties intrinsic to the thick film pastes, make thick film passive structures and interconnects inferior to thin film counterparts? In an effort to answer this question, and obtain an estimate of the impact the actual screen printing process and the material compositions have on the propagation of microwave signals, the hg/2 end-coupled resonator filter was selected as a test vehicle. This paper will describe the design and characterization of a number of end-coupled resonator filters fabricated using a selection of thick and thin film media.