Thermal Management Analysis of Conventional Multi-PCB-Stack for Geothermal Drilling Tools

Abstract

Efficient thermal management of downhole electronics remains a critical challenge for the deployment of Measurement-While-Drilling (MWD) systems in high temperature geothermal environments. This study evaluates the thermal performance of conventional multilayer polyimide-based printed circuit boards (PCBs) within a modular, multi-stack architecture. Experimental tests were conducted under controlled heating conditions to characterize the temperature response and extract effective thermophysical properties of the PCB material. This data was then used to calibrate conjugate heat transfer simulations of both the PCB and the complete tool assembly. Results show that conventional PCBs exhibit anisotropic heat conduction, with radial thermal conductivities between 20–25 W/m·K, and axial values increasing from 0.3 to 0.6 W/m·K as temperature rises from 60°C to 200°C. Simulations indicate that conventional PCBs can effectively dissipate heat for low-power components ( less than 0.5 W) without excessive temperature rise, supporting their viability for modular MWD configurations. The findings provide valuable insights for designing cost-efficient, thermally reliable electronics suitable for next-generation geothermal drilling systems.