A feasibility study of flip-chip packaged gallium nitride HEMTs on organic substrates for wideband RF amplifier applications

Gallium nitride (GaN) technology has emerged as a frontrunner for high power electronics applications. By performing a survey of wire-bond and flip-chip-packaged GaN HEMTs on either AlN (a ceramic with high thermal conductivity) or LCP (an organic polymer with low thermal conductivity), the thermal and electrical limits of each package are established. Flip-chip packaging has the benefit of improving the bandwidth of a hybrid PA. Dies that were wire-bonded on AlN showed best performance, and were able to dissipate more than 6 W of power while remaining below the maximum operating junction temperature. On the other hand, flip-chipped devices on LCP were severely limited by thermal effects, even at a 10% duty cycle. This study motivates the need for advanced packaging techniques, such as integrated microfluidics or backside heat-sinking, in order to make LCP a viable material for high-power applications.