Researchers have developed a frequency-domain thermoreflectance (FDTR) microscopy approach to visualize thermal conductivity and interfacial thermal conductance in thermal interface materials (TIMs) at the microscale. The study, published in Thermo-X , provides a direct imaging method for revealing structure–property relationships in particle-filled thermal composites used for electronic thermal management.
Unlike conventional techniques that measure only bulk-averaged thermal conductivity or interfacial resistance, the new FDTR microscopy platform enables spatially resolved mapping of local thermal properties within a sandwich-configured TIM structure. The method combines a bidirectional thermal transport model with a customized sample fixture, allowing extraction of thermal conductivity and interfacial conductance with micrometer-scale resolution.
The approach reveals pronounced microscale heterogeneity in a particle-loaded thermal grease. High thermal conductivity regions are observed to cluster spatially , while low-conductivity zones correspond to defects or filler-deficient areas. Correlative micro-computed tomography (micro-CT) further confirms that regions with enhanced thermal transport coincide with dense aggregation of thermally conductive filler particles.
Under varying contact pressures, FDTR imaging captures dynamic redistribution of conductive features within the TIM layer. While the area-averaged thermal conductivity and interfacial conductance remain relatively stable over moderate pressure ranges, local thermal maps reveal continuous rearrangement and flow-like movement of high-conductivity domains during loading and unloading cycles.
Beyond imaging, the study introduces a statistical framework to describe the distribution of local thermal conductivity. The results show that the measured values deviate from a Gaussian distribution and instead exhibit an asymmetric, long-tailed profile. This behavior is attributed to the combined effects of particle spatial randomness and a lognormal particle size distribution, which together govern the observed thermal heterogeneity.
Overall, this work demonstrates FDTR microscopy as a powerful tool for directly linking microstructure and thermal transport in TIMs. The combined FDTR and micro-CT approach provides new insight into the design of high-performance thermal management materials for next-generation electronics.
Thermo-X
Experimental study
Not applicable
Imaging thermal properties of thermal interface materials using frequency-domain thermoreflectance microscopy
2-Jun-2026
Ronggui Yang is an Editorial Board Member of Thermo-X. The other authors declare no conflicts of interest.