Micromachined silicon conformal packaging for millimeter wave system applications

Summary form only given. Low RF loss, high density, yet affordable mm-wave system packaging combined with ever increasing MMIC device performance is set to unlock the long anticipated potential of many mm-wave systems operating in the 30-100 GHz spectral region. This paper discusses the merging of several complementary technologies that enable highly miniaturized mm-wave multi-function packages which are potentially capable of high rate and volume production: silicon RF micromachining, flip chip MMICs and PbSn solder MMIC attachment. The heart of this approach is the RF silicon micromachining technology developed at the University of Michigan. This development has led to the successful fabrication of numerous mm-wave building block components densely integrated in conformal Si packages that provide low RF loss with high isolation. The fabrication is based upon modified Si processing which has the potential for high volume batch production. Hard-bumped, flip chip MMIC attachment by lead-tin solder reflow provides repeatable and accurate chip self-alignment. Plated silver bumps 2 mils in diameter provide MMIC with low parasitic DC, RF and thermal interconnections. This flip chip attachment technique is suited to automated "pick, place and bond" equipment, thus contributing to the low cost mm-wave system implementation objective. Both simulated and measured micromachined component performance are presented as well as bump measured geometrical and mechanical characteristics.