Impact of Immersion Cooling on Thermomechanical Properties of Low-Loss Material Printed Circuit Boards

For traditional datacenters one third of the total energy consumed is directed towards cooling information technology (IT) equipment. High demand for new datacenters, vast amount of energy consumption, and their impact on the climate requires datacenter industry to make them energy efficient and opt for immersion cooling technologies. From thermal perspective, immersion cooling is better than traditional air cooling technology. However, detailed study of material compatibility of the various electronics packaging materials for immersion cooling is essential to understand their failure modes and reliability. The stiffness and thermal expansion are critical material properties for electronics mechanical design. Printed circuit board/substrate is a critical component of electronic package and heavily influences failure mechanism and reliability of electronics both at the package and board level. This study mainly focuses on two major challenges. The first part of the study focuses on the impact of thermal aging in dielectric fluid for single-phase immersion cooling on the low loss material printed circuit board's (PCB) thermo-mechanical properties. PCB sample weight is compared to quantify absorption of the dielectric fluid into PCBs or leaching of the plasticizers into the fluid. The second part of the study is the impact of thermal aging on thermo-mechanical properties of low-loss PCBs in the air. The low-loss PCBs, Megtron6 are aged in mineral oil, and air for 720 hours at four different temperatures: 22°C, 50°C, 75°C, and 105°C. The complex modulus and coefficient of thermal expansion are characterized before and after aging for both parts and compared.