Microwave frequency model of flip-chip interconnects using anisotropic conductive film

Flip-chip interconnects using the anisotropic conductive films (ACF) offers the simple and the lead-free processing as well as cost effective packaging method. To use the ACF flip-chip joint in high-speed digital and microwave devices, precise electrical model is needed for the frequency range over 1 GHz. In this paper, we firstly propose an extraction procedure and a microwave frequency model of the ACF flip-chip interconnects based on microwave S-parameter measurement and subsequent network analysis. In addition, it is shown that the ACF flip-chip interconnects have comparable transfer and loss characteristics to those of the solder bump flip-chip bonding. The ACF flip-chip exhibited less than 2-ohn resistance and 0.1-nH inductance, indicating the usefulness of the ACF flip-chip bonding over GHz frequency. Finally, we demonstrated 80-ps rising digital signal transmission with low loss and reflection through the ACF flip-chip interconnects.