An Investigation of the Process Stability of RF SiP Made of DuPont 943 and 9K7

Abstract

RF packaging is one of the most challenging but also the fastest growing topic in low temperature cofired ceramic (LTCC) technology. Today LTCC is particularly useful for advanced packages and systems-in-package because of its electrical, functional, and thermomechanical properties as well as its excellent long-term stability and reliability. LTCC combines the potential for miniaturization and low loss handling of high frequencies up to 110 GHz and it also offers the opportunity to integrate additional features. Therefore it has to go through various manufacturing steps and several refirings without any performance degradation or loss of dimensional accuracy. This article discusses the impact of thermal postprocessing on RF characteristics and geometric properties of LTCC. Ceramic substrates with radar front ends, calibration structures, and other test vehicles made of DuPont Green Tape® 943 and 9K7 were cofired following the recommended conditions and refired several times in order to investigate and compare the influence of the postfiring. The flatness, dimensions, and RF performance of the ceramics up to 110 GHz were evaluated and compared.