A 77 GHz broadband flip-chip transition on LTCC submount

A flip-chip interconnect of a SiGe chip to an LTCC submount with microstrip feeding line is presented. In order to be compatible with cost-effective submount solutions, bumps with 125 µm diameter and 100 µm design rules on the LTCC side are applied. Also, the use of vias is avoided. Although the dimensions are relatively large for the 77 GHz range, transitions with 10 GHz bandwidth are achieved. Test structures were manufactured and measurement results show good agreement with simulation yielding less than 1 dB of insertion loss at 77 GHz.