Low loss multilayer transitions using via technology on LCP from DC to 40 GHz

This paper presents low loss CPW (Co-Planar Waveguide) and microstrip via transitions on LCP (Liquid Crystal Polymer) substrate. The CPW transition using 105 µm via holes on a 4 mil LCP shows virtually no loss up to 25 GHz and about 0.13 dB of loss per transition at 40 GHz. The microstrip transition has no loss up to 15 GHz and approximately 0.5 dB of loss per transition at 30 GHz. In addition, the response with 70 µm vias opposed to 105 µm vias on a 4 mil substrate added slightly more loss of 0.16 dB per transition at 40 GHz. Using 2 mil thick LCP, a back to back transition with 55 µm via holes has been made on a single layer LCP and also on LCP bonded to a silicon wafer. The results show less than 0.1 dB loss per transition up to 40 GHz in both designs.