[논문 리뷰] Simultaneous measurement of pressure-dependent bulk and interfacial thermal properties in thermal interface materials using square-pulsed source thermoreflectance

Tao Chen, Xin Qian외 1명|arXiv (Cornell University)|2026. 03. 24.

Thermal properties of materials인용 수 0

한 줄 요약

이 논문은 정사각 펄스 소스 열반사(SPS-TR) 방법을 도입하여 TIM 스택에서 벌크 열전도도(k), 부피 열용량(C), 그리고 계면 열저항(ITR)을 제어된 기계적 하중 하에 넓은 주파수 범위(1 Hz에서 10 MHz)에서 동시에 정량화한다.

ABSTRACT

Thermal interface materials (TIMs) critically regulate heat dissipation from electronic chips to heat spreaders, yet their thermal conductivity (k), volumetric heat capacity (C), and interfacial thermal resistance (ITR) evolve with mechanical pressure and cannot be determined simultaneously using existing steady-state or transient techniques. As a result, the coupled roles of bulk compaction and interfacial contact in governing heat transport in TIM assemblies remain poorly resolved. Here, we present a square-pulsed source (SPS) thermoreflectance method that enables simultaneous determination of k, C, and ITR in TIM stacks under controlled mechanical loading. By spanning square-wave modulation frequencies from 1 Hz to 10 MHz, SPS probes a broad range of thermal penetration depths, enabling distinction between heat diffusion in the TIM bulk and interfacial heat transfer at the Al/TIM contact. Measurements on a thermally conductive gel, a thermal pad, and a high-vacuum grease during compression-unloading cycles reveal distinct pressure-dependent thermal transport mechanisms. The gel and pad exhibit increases in k and C, reduced ITR, and pronounced hysteresis, indicating coupled bulk densification and persistent interfacial conformity during loading cycles. In contrast, the grease shows nearly pressure-independent bulk properties but a strong pressure dependence of ITR, consistent with an interface-dominated response. These results resolve the long-standing challenge of simultaneously quantifying bulk and interfacial thermal transport in mechanically loaded TIM assemblies, enabling experimentally constrained thermal management and reliability analysis in electronic packaging.

연구 동기 및 목표

• Address the challenge of simultaneously determining bulk TIM properties (k and C) and interfacial thermal resistance (ITR) under mechanical pressure.
• Develop a measurement technique that decouples bulk diffusion from interfacial transfer in TIM assemblies.
• Enable analysis of how compression cycles affect TIM thermal transport for reliability in electronic packaging.

제안 방법

• Apply square-pulsed source thermoreflectance (SPS-TR) to TIM stacks.
• Span square-wave modulation frequencies from 1 Hz to 10 MHz to probe different thermal penetration depths.
• Distinguish TIM bulk diffusion from Al/TIM interfacial heat transfer by analyzing frequency-dependent responses.
• Perform compression–unloading cycles on different TIM materials (gel, pad, grease) to observe pressure effects on k, C, and ITR.
• Infer hysteresis and interface-conformity effects from the observed thermal transport changes under loading.

실험 결과

연구 질문

• RQ1 Can k, C, and interfacial thermal resistance (ITR) be measured simultaneously in TIM assemblies under mechanical pressure?
• RQ2 How do bulk and interfacial contributions to heat transport evolve with pressure for different TIM types (gel, pad, grease)?
• RQ3 Can SPS-TR distinguish between bulk-dominated and interface-dominated thermal transport regimes under compression?
• RQ4 What is the role of hysteresis and interfacial conformity in pressure-dependent TIM thermophysical properties?

주요 결과

• SPS-TR enables simultaneous extraction of bulk and interfacial thermal properties under controlled loading.
• Gel and pad show increases in k and C, with reduced ITR and pronounced hysteresis during loading cycles.
• Grease exhibits nearly pressure-independent bulk properties but strong pressure dependence of ITR.
• Results reveal coupled bulk densification and persistent interfacial conformity in some TIMs, versus interface-dominated response in others.
• The method addresses the long-standing challenge of decoupling bulk and interfacial transport in loaded TIM stacks.