Molybdenum copper based ultrathin two-phase heat transport system for high power-density gallium nitride chips

Abstract

• Design of metal matrix composite enables creation of ultrathin heat transport device. • Ultrathin devices integrated with microchip for low-thermal-resistance heat removal. • The thermal conductivity of the device reaches 10200 W/(m·K) under large heat flux. • Low-stress encapsulation for high power-density chip cooling systems is highlighted. Metal matrix composite based ultrathin two-phase heat transport devices with excellent thermal conductivity and low thermal expansion can address heat dissipating issues and thermal expansion mismatch-induced mechanical failures in the high-power-density micro-electronic systems. Due to the difficulties in processing metal matrix composites, however, achieving the fabrication of the ultrathin devices and their reliable integration with semiconductor chips has challenges. The precision machining and surface engineering of composite materials address the difficulties in processing metal matrix composite based ultrathin devices and contribute to reliable welding encapsulation of the chip. Here, we generate an ultrathin (≤1 mm) metal matrix composite based two-phase heat transport device with low thermal expansion and integrate such device with the gallium nitride chip. The sandwich-structured molybdenum (Mo) copper (Cu) composite, Cu-MoCu-Cu, is used as the casing material of the hermetically welded device. The Mo-Cu based two-phase heat transport device demonstrates an extremely low thermal resistance, which is 95% lower than that of the Cu plate. This device with superior thermal conductivity of 10200 W∙m −1 ∙K −1 enables the stable operation of the high-power-density (7.9 × 10 2 W/cm 2 ) gallium nitride micro-chip within the safe operating temperature range (20–175 °C). In addition, the Mo-Cu based device also helps reduce the thermal stress generated at the encapsulation interface by 39% compared to Cu cooling plate, and thus mitigates the fatigue risks of the device. This chip-level integration of heat transport system using the metal matrix composite-based ultrathin two-phase heat transport devices offers new opportunities in the integration of high heat dissipation and low-stress encapsulation in compact electronic systems.