Comparison of thermal-shunt and flip-chip HBT thermal impedances: comment on "Novel HBT with reduced thermal impedance"

For the original article see ibid., vol. 5, no. 11, p. 373-5 (1995). As indicated in the aforementioned work, reducing thermal impedance is a key to increasing heterojunction bipolar transistor (HBT) power densities and there are several competing technologies evolving to reduce the thermal impedance of HBTs. This comment specifically addresses the question: does the flip-chip technology proposed by D. Hill et al. offer significantly lower HBT thermal impedance than the thermal-shunt technology? The commenters conclude that while any further reduction of the thermal impedance associated with flip-chip technology has yet to be determined, a comparison of the two technologies provides no compelling reason for adopting flip-chip technology.