Leak-Proof Packaging for GaN Chip with Controlled Thermal Spreading and Transients

Abstract

Plastic mold packaging is proposed as the first solution to make leak proof joinability between the heat spreader and plastic mold by optimization of micro-textures on the spreader. No leaks were detected after gross-leak testing. Vertically-aligned graphitic substrate (VGS) provided the second solution to control thermal spreading and transients from GaN to the spreader. A Copper-laminated VGS with stacking graphene planes in Y and Z-axes significantly reduced the channel temperature and Thermal resistance (Rth) by 40 K and 0.28 K/W than those in Cu-based composite substrate (CCS) even for the same spreader thickness of 1 mm. Since thermal diffusivity for VGS is ten times faster than CCS., temperature difference during ON/OFF intervals was reduced by 18 K between Cu-laminated VGS-packaged and CCS-packaged GaN HEMTs. The time constant of Cu-laminated VGS-packaged GaN HEMT was 2.5 ms, much longer than 0.2 ms.