Multi-gigabits digital signal transmission in flip-chip interconnect is studied. It is indicated that a conventional flip-chip (CFC) interconnect has two distinct problems. Adding two micromachined features, air cavity and trenches, can improve the transmission characteristic of the CFC interconnect, which is called locally matched flip-chip (LMFC) interconnect. The measured S-parameters, which are the parameters in the frequency domain, show that the LMFC interconnect has the bandwidth of return loss below 20 dB up to 50 GHz. Based on the frequency domain response, the CFC and LMFC flip-chip interconnects are characterized in the time domain using eye-diagram. The simulated eye-diagram performance of the LMFC interconnect indicates that introducing the air cavity and trench to the CFC interconnect improves the multi-gigabits digital signal transmission significantly and the LMFC interconnect could operate at 40 Gb/s bit rate.