Novel Packaging, Cooling and Interconnection Method for GaN High Performance Power Amplifiers and GaN Based RF Front-Ends

We report a new approach for low-cost, scalable RF front-end packaging that enables "known good die" GaN MMICs to be combined with other ICs (Si, SiGe etc) and passives in an integrated 3D package that includes RF interconnects and cooling. The electroformed heat sink also serves as the substrate for creating the RF front-end. We call this multi-purpose layer the Integrated Thermal Array Plate (ITAP). Compared to conventionally mounted GaN power amplifiers (PA) using AuSn solder, the ITAP X-band PA showed 1.4x improvement in CW P-out (4.4W at 8 GHz) while the ITAP Ku-band showed 1.3x improvement in CW P-out (4W at 12 GHz). Compared to silver epoxy mounted PAs the improvement was 2x and 1.5x respectively. Additionally, by using a meandered GaN gate structure we demonstrated that the ITAP reduces the junction temperature by 40 degrees C when the dissipated power is at 2W/mm or increases the power handling by 1.45x when the junction temperature is held at 150 degrees C.