A Flexible-PCB on DPC GaN Power Module With Ultra-low Parasitic Inductance

The gallium nitride (GaN) power device, with its ultrahigh switching speed and low on-resistance, has greatly promoted the development of power electronic converters towards high frequency and high-power density. However, the packaging parasitic parameters will limit its switching speed. In order to maximize the excellent characteristics of GaN power device, this paper first comprehensively analyzes the effects of parasitic parameters on its switching transients to guide its packaging design. Based on this analysis, a highly integrated Flexible-printed circuit board (Flex-PCB) on direct plating copper (DPC) ceramic substrate GaN half bridge power module is proposed. The GaN bare dies are sandwiched between Flex-PCB and DPC, with the driver circuit and decoupling capacitors placed on the top surface of Flex-PCB. The ultra-thin Flex-PCB combined with the proposed hybrid loop layout method minimizes the loop size while achieving magnetic field self-cancellation, reducing the parasitic inductance of the power loop to less than 0.1 nH. Additionally, compared to PCB on DPC hybrid packaging structure, the proposed packaging structure can reduce the maximum von Mises stress experienced by the bare dies and solder layers by 29% and 32.7%, respectively. After a 48 V/90 A double-pulse test, the turn-off voltage overshoot is only 8 V, and the parasitic inductance of the power loop is calculated to be only 71 pH. Finally, a 5MHz, 48 V-20 V buck converter is built based on the proposed GaN power module, demonstrating its broad application prospects in high frequency and high-power density power converters.