A New Development of Thermally Enhanced GaN-QFN with Heat Slug Attach Bonding Technology

GaN mosfet provides significantly lower resistance and low capacitance than silicon mosfet which makes GaN mosfet considered as alternative power devices to replace silicon mosfet, and by the adoption of GaN mosfet technology, the high-frequency power supply can be designed in small form factor by miniaturization of passive components. Integrated architecture with driver IC and GaN mosfet in QFN-SIP (System in package) is preferred solution to maximize the electrical performance of GaN devices, but this QFN-SIP has its own thermal challenge as it contains driver IC power dissipation and GaN mosfet power dissipation in one package so thermal improvement solution of QFN-SIP is required to be used in power supply without having thermal problems. In this paper, various thermal improvement methods are recommended about 8x8mm QFN-SIP available in the market now, simulation study compares maximum junction temperatures and thermal resistance of QFN-SIP by increasing package size, increasing leadframe thickness, changing die location, and Cu clip bonding and Ag sintering attach. Thick leadframe QFN-SIP can be achieved by heat slug bonding technology, and QFN 10x12mm with heat slug bonding samples build completed to run MSL3 3x reflow and temperature cycle and power cycle test.