A Low-Cost DC-to-84-GHz Broadband Bondwire Interconnect for SoP Heterogeneous System Integration

A low-cost broadband bondwire interconnect is proposed for heterogeneous system integration. Transmission lines are incorporated with bondwires to form a two-path structure, which can effectively reduce the bondwire effect. Theoretical analysis is provided using a graphical method and it shows that the interconnect can give widest operation bandwidth from dc up to a maximum frequency fmax if the length of the transmission lines is designed at an optimal electrical length θmax. In particular, θmax only depends on the characteristic impedance of the transmission lines. The achievable fmax is limited by the bondwire inductance, i.e., smaller bondwire inductance is preferred to have wider operation bandwidth. An interconnect from a 0.18-μm CMOS chip to a glass-integrated-passive-device carrier is designed to verify the proposed concept. Measured results show that the insertion loss and the return loss can be better than 3.0 and 13.4 dB, respectively, from dc to 84 GHz. The proposed interconnect shows around 3.2 times bandwidth of a single bondwire alone. To the best of authors' knowledge, this work demonstrates the bondwire interconnect with the widest operation bandwidth for heterogeneous system integration by using system-on-package reported thus far.