High-frequency signal transmission characteristics of coplanar waveguides with cone bump interconnections

We evaluated high frequency signal transmission characteristics of coplanar waveguides fabricated using cone bump interconnections on flip-chip bonded surfaces. The signal insertion loss (S21 parameter) increased with the number of bump interconnections. At 40 GHz, the signal insertion loss due to the bump interconnections was 0.017 dB / bump. This value was small enough for application to most radio-frequency devices. Besides, the bump interconnections did not alter the characteristic impedance of the waveguide from the designed even at 40 GHz. The results indicate that the cone bump offers high-frequency signal data transmission lines for chip-stack integration of LSIs.