In this paper, a 2D finite element heat transfer simulation was used to optimize the quasi monolithic technology (QMT) structure and to reduce thermal resistance in power microwave and millimeter wave applications, considering limitations in the fabrication process. Effects of different factors and parameters such as epoxy thermal conductivity, distance between active device and Si substrate, front side substrate metallization and heat spreader on the back side have been described. Results show that by using a good heat spreader on the backside of the active device, total thermal resistance comparable to that in standard MMICs is possible

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