Abstract: In this paper,we have developed a process to fabricate BCB/Au multilayer stack on low loss silicon based on the embedded package structure,especially for the dielectrical layers spin-coating at the first time on the silicon substrate.We have designed,fabricated and characterized transmission lines, including micro-strip and coplanar waveguide lines.They have excellent performance:insertion loss and return loss of the standard 50-Ohm micro-strip line are better than 0.08dB/mm and 32dB/mm during the 20-30GHz band.Also,we have fabricated a power divider using thin-film micro-strip line for the SIP of the front-end of a radar working at K-Band.This fabricated power divider is just 1.6*0. 84mm²,with insertion loss less than 0.45dB and return loss better than 25dB.