Heat Flux Sensors

In-situ heat flux measurements for micro-pin-fin heat sinks are essential for accurate performance modeling and optimization but notoriously difficult to obtain. My master’s thesis research focused on the design, fabrication and testing of an integrated heat flux sensor, built directly on an individual copper pin (400 microns x 400 microns x 1200 microns). The sensor was to be used for in-situ heat transfer studies within a micro-pin-fin heat sink as part of a collaboration with the University of Hawaii at Manoa. The heat flux sensor utilized two nickel-based 4-wire resistance temperature detectors (RTD). By directly fabricating the sensors on copper substrates, we were able to minimize the contact thermal resistance, resulting in more accurate measurements.

As the primary research assistant on the project, I performed all stages of development. Initial sensor design included signal sensitivity analysis and heat transfer modeling in Matlab. The integrated sensor pins were fabricated on bulk copper surfaces using a combination of lithography-based microfabrication and micro end milling. Copper wafers were hand polished to a flatness and roughness suitable for the necessary fabrication processes, which included photolithography, polyimide deposition via spinning, and metal deposition through physical vapor deposition. Once deposited, micro-end-milling was utilized for machining of the 3D pin structure and device segmentation. Final device calibration was performed using a tube furnace. Heat flux testing utilized an Nd-YAG laser with specialized data acquisition system acquired for the project.

For more information, please see the following publication: Thin film heat flux sensors fabricated on copper substrates for thermal measurements in microfluidic environments