Hideki Kusamitsu

RF performance of a 77 GHz monolithic CPW amplifier with flip-chip interconnections

This paper describes the RF performance of a 77 GHz coplanar waveguide (CPW) monolithic three-stage amplifier connected to an alumina substrate using flip-chip technology. Key issues discussed here cover the substrate, MMIC and bonding structures to realize a good amplifier operation at this frequency. The flip-chip mounted GaAs monolithic amplifier exhibited a gain higher than 15 dB at around 77 GHz.

The flip-chip bump interconnection for millimeter-wave GaAs MMIC

The flip-chip bump interconnection structure has become popular for microwave and millimeter-wave package applications. The structure is expected to provide higher performance and a low cost packaging method. This paper presents the results of an evaluation of flip-chip assembled RF devices. A co-planar line type GaAs MMIC (monolithic microwave IC) was mounted on an Al/sub 2/O/sub 3/ substrate using the flip-chip bump interconnection method. The electrical performance (S-parameter) was measured and the reliability of the interconnection was tested. The DC characteristics of a 30 GHz band and a 60 GHz band LNA (low noise amplifier) were the same between before and after mounting and the RF performance of the assembled MMIC was the same as the bare chip without packaging; however, the influence of underfilling was confirmed. When epoxy resin was injected into the gap between the bare chip and the substrate, the frequency band of the MMIC shifted to the low side. The reliability of the bump interconnection was excellent. The interconnection resistance did not change in a temperature cycle (-55/spl deg/C to +125/spl deg/C, 1000 cycles) test.