Broadband Flip-Chip Interconnects for Millimeter-Wave Si-Carrier System-on-Package

A flip-chip interconnect is proposed to achieve good electrical performance applicable to millimeter-wave applications. By Au-Au thermocompression technique, the transition structure provides continuity of characteristic impedance from the on-carrier CPW line to the on-chip microstrip line, as well as smooth current flow. Parameter optimization further indicates that the tapered reference ground connection is insensitive to the frequency response. Characterization of the structure is conducted by the thur-reflect-line (TRL) calibration technique to test the flip-chip interconnects up to 50 GHz. Measurement results show that return loss is better than 15 dB and insertion loss smaller than 1.7dB up to 50 GHz. The broadband transition structure is suitable for high frequency application without any external matching network.