Thermally Conductive Electrically Insulating Electronics Packaging for Water Immersion Cooling

Abstract

Power densification is making thermal design a key step in the development of future electrical devices. Systems such as data centers and electric vehicles are generating more heat, which requires efficient cooling to maintain the electronics at temperatures below their limits and to ensure reliability. Immersion cooling has emerged as a promising thermal management technique that brings the coolant closer to the heat-generating elements, hence reducing thermal impedance and improving cooling. Although the dielectric liquid coolants used in immersion cooling do not compromise the electrical performance of the submerged electrical devices, their cooling performance is inferior compared to ideal coolants such as water. To use water as an immersion coolant, the electronics need to be encapsulated to prevent short circuits. Here, a packaging approach is developed that insulates the electronics from the surrounding water and spreads heat for better cooling. The package consists of an aluminum nitride (AlN) component for insulation and heat spreading, and a Parylene C coating for conformal electrical insulation. The package is characterized electrically by measuring the leakage current in water under dc voltages up to 600 V for periods of up to seven days. The thermal performance of this packaging method is also characterized by calculating the junction-to-coolant thermal resistance. The developed packaging design can be implemented in high-power-density applications where the heat flux is beyond what standard dielectric fluids can handle.