Non-Contact Measurement of Thermal Contact Resistance Using Lock-in Thermography

(20:04 + Q&A) Prof. Ryohei Fujita, Nagoya University
From the First IEEE Hybrid Bonding Symposium 
Summary: Thermal contact resistance (TCR) refers to the phenomenon where heat flow is impeded at the contact interface between two materials. In advanced electronics packaging and systems, TCR can lead to significant temperature increases and performance degradation by obstructing efficient heat dissipation. Notably, direct bonding technologies, such as diffusion bonding and hybrid bonding, offer superior bonding strength, but the evaluation of TCR for these methods is limited due to the absence of non-contact measurement techniques for real interfaces. We have developed a novel method for TCR measurement at the interface between bulk materials, utilizing Lock-in Thermography (LIT) combined with periodic laser heating. This method employs an infrared microscope to visualize dynamic temperature behavior across the contact interface, presenting the potential for assessing the quality of hybrid bonding interfaces.
In this presentation, we will share TCR measurement results for various material interfaces, showing images of a cross-section of a bilayer isotropic graphite specimen bonded with adhesive. The specimen’s surface was periodically heated with a diode laser at a specific frequency, and one-dimensional heat conduction across the cross-section was visualized using lock-in signal processing. We show the phase delay of the periodic temperature response. Phase jump due to the TCR on the contact interface is clearly observed. The phase delay along the z-axis (perpendicular to the contact interface) is presented. By fitting a theoretical model to the experimental data, TCR was determined to be 3.28 × 106 m2K/W. Additional measurements were conducted on bilayer specimens comprising Cu and AlN, Cu and SiN, and Cu and Mo to evaluate the sensitivity of this method.
Bio: Ryohei Fujita is an Assistant Professor in the Thermal Control Engineering Group at Nagoya University, Japan. He earned both his B.S. and M.S. degrees in Aerospace Engineering from Nagoya University. He has industry experience as an airframe structural engineer, specializing in Non-Destructive Testing (NDT) within the airline sector. In 2024, he obtained his Ph.D. from Nagoya University and subsequently served as a postdoctoral fellow supported by the Japan Society for the Promotion of Science. His primary research interests include NDT of composite materials and the evaluation of thermal management materials for semiconductors using infrared thermography.

For other edited  videos from this symposium, visit  https://attend.ieee.org/hbs/?page_id=456