Effect of Modularity on the Thermal Management of Optimized Printed Circuit Boards for Geothermal Drilling Tools

Abstract This paper investigates a novel approach to thermal management in high-temperature Measurement While Drilling (MWD) tools, addressing critical challenges in geothermal drilling where conventional systems fail to operate efficiently above 175-185 °C. The proposed design integrates modular mechanical housing and advanced thermal management systems optimized for circular, axially stacked Printed Circuit Boards (PCBs). Using Aluminum Nitride (AlN) ceramic PCBs for their superior thermal conductivity, the design enables radial heat dissipation, reducing thermal resistance and maintaining operational stability under extreme conditions. Results indicate that the modular design ensures effective heat evacuation through metal-to-metal contacts and optimized chassis geometry. At a nominal chip power of 0.5 W, the maximum temperature increase remained below 3.5 °C for four PCB stacks and 210 °C mud temperature, highlighting the system's reliability. The findings underscore the importance of modularity for simplifying assembly and improving thermal management in harsh environments.