Directly Probing Thermal Transport Across Micrometer‐Thick Metallic Interfaces Using Transient Thermal Grating Spectroscopy

The increasing power density and continued miniaturization of microelectronics impose significant challenges on thermal management. Interfaces between two mating surfaces can represent a substantial fraction of the total thermal resistance to heat flow to the surroundings. A deep understanding of the interface structure and its thermal transport properties is imperative for better thermal interface design strategies. Soldering, sintering, and direct bonding are widely used in electronics packaging to attach the die to the heat spreader or heat sink. Yet, a direct probing method for the thermal interface properties is lacking. For the first time, a laser-induced transient thermal gratings (TTG) spectroscopy method is presented to investigate such interfaces. Using soldered interfaces as an example, it is demonstrated that the thermal conductivity for bond line thicknesses of 55 and 11 µm can be resolved. The technique enables the identification of structure-property relationships for interfaces from various die-attach methods. It offers a powerful and convenient probe of the interface quality and benefits the future design of high-performance microelectronic devices with low contact resistance.