Packaging A Top-cooled 650V/300A GaN Power Module with Insulated Thermal Pads and Gate-Drive Circuit
The proposing team will design a 650V/300A GaN power module using dies from GaN Systems. Ceramics will be employed for the thermal pad insulation and the smart PCB will be adopted for the flux cancellation and gate-drive-circuit integration. Upon the completion of the project, we expect to provide a high-current, high-compactness and affordable GaN power module with the thermal pad insulated from the drain and source and gate-drive circuit integrated inside the package, which facilitates the assembly of GaN devices with enhanced thermal performance compared to regular GaN HEMTs on the market. The proposed module can be found immediate use in our 22kW EV on-board charger with Hella and 100kW six-phase inverter with Mercedes Benz.
3-D view of the packaged 650V/300A GaN half-bridge
The key technology involved includes: 1) ceramic insulation. A thin layer of ceramics is sandwiched between two copper layers. In this way, all G, D and S terminals of GaN devices are insulated from the heatsink. The first-layer copper connections are used to internally connect the top-switch S terminal with the D terminal of the bottom switch. The second layer of the copper is directly attached to the heatsink. Thermal grease can be used for better attachement, which however still yields much lower thermal impedance compared to state-of-art TIMs. Silicon gel will be used to fill the package for mechanical support and insulation; 2) smart PCB, which is essentially a multi-layer PCB with the decoupling cap to form the flux cancelling loop to offset the potential parasitic inductance. In addition, the gate-drive circuit of top and bottom switches, including the needed power supply are soldered on this PCB. Only PWM signals for top and bottom switches, i.e., PWM/T and PWM/B are to be provided by the control system. All connectors of this smart PCB will be directly soldered on the external control and power PCBs. Compared to bottom cooled devices using IMS, which essentially is one-layer board introducing high parasitic inductance, the proposed packaging approach adopts the extra multi-layer PCB to realize flux canceling. Compared to discrete switches, soldering dies in one package to form a half bridge yields much higher compactness.
How WBG Can Help
The success of this project provides a high-current (>300A) and high-voltage (650V) GaN power modules, which will facilitate the assembly, reduce the cost, enhance the thermal performance by lowering the probability of thermal runaway thereby expediting the acceptance of GaN HEMTs. The proposing team forsees the immediate usage of GaN power modules in on-board chargers (OBCs) and motor inverters in electric vehicles (EVs).
- Yu Yan
- Ziwei Liang
- Jared Walden