Wafer-level packaging method incorporating embedded thermal management for GaN-based RF front-ends

We report a new wafer-level, low-cost, scalable RF front-end packaging approach that enables heterogeneous integration of GaN integrated circuits (IC) with other ICs (Si, SiGe, InP, GaAs etc) and RF passives in a 3D package that includes RF/DC interconnects and thermal management. This is achieved by forming a composite substrate utilizing double-side polished alumina wafers with embedded electroformed heat spreaders and through substrate vias. We call this composite substrate Integrated Thermal Array Plate (ITAP). Compared to conventionally mounted GaN power amplifier (PA) using AuSn and silver epoxy the ITAP pckaged X-band PA demonstrated 1.42x and 2x improvement in output power respectively (36.4 dBm, with 57% associated power added efficiency). By using a junction temperature (T_j) evaluation circuit we demonstrated that the ITAP reduces the T_j by 40° when the dissipated power is 2W/mm or increases the power handling by 1.45x when the T_j is held at 150°C. Using the same approach we are also reporting wafer-level packaged GaN power switches as well as thermal cycling and thermal shock test data that show no performance degradation.