Effects of Thin Film Heat Spreader on Hot Spots Mitigation in Heat Sinks

The effects of graphene platelets and diamond based thin film heat spreaders on maximum temperature of integrated electronic circuits were investigated. A fully three-dimensional conjugate heat transfer analysis was performed to investigate the effects of thin film material and thickness on the temperature of a hot spot and temperature uniformity on the heated surface of the integrated circuit when subjected to forced convective cooling. Two different materials, diamond and graphene were simulated as materials for thin films. The thin film heat spreaders were applied to the top wall of an array of micro pin-fins having circular cross sections. The integrated circuit with a 4 × 3 mm footprint featured a 0.5 × 0.5 mm hot spot located on the top wall which was also exposed to a uniform background heat flux of 500 W cm−1. A hot spot uniform heat flux of magnitude 2000 W cm−2 was centrally situated on the top surface over a small area of 0.5 × 0.5 mm. Both isotropic and anisotropic properties of the thin film heat spreaders made of graphene platelets and diamond were computationally analyzed. The conjugate heat transfer analysis incorporated thermal contact resistance between the thin film and the silicon substrate. The isotropic thin film heat spreaders significantly reduced the hot spot temperature and increased temperature uniformity, allowing for increased thermal loads. Furthermore, it was found that thickness of the thin film heat spreader need not be greater than a few tens of microns

Multiscale Micro/Nanostructured Heat Spreaders for Thermal Management of Power Electronics

In this chapter, we describe surface modification techniques for enhancing heat/mass transfer and evaporation on heated surfaces. The effect of asymmetrical structure in designing a vapor chamber, patterned with multiscale micro/nanostructured surfaces will be introduced. The wettability patterned surface and its mechanism for improving the evaporation rate of a droplet and the thermal performance of nucleate boiling are discussed. An ultrathin vapor chamber based on a wettability patterned evaporator is introduced as a case for the application of the wettability pattern. Besides, modifying the surface with nanostructure to form a multiscale micro/nanostructured surface or superhydrophobic surface also enhances the phase change. Several types of heat spreaders are proposed to investigate the effects of multiscale micro/nanostructured surface and nanostructured superhydrophobic condenser on the thermal performance of the heat spreaders, respectively. The effects of multiscale micro/nanostructured evaporator surfaces with wettability patterns will be analyzed and experimental data will be presented.

Efficient Thermal Analysis of Lab-Grown Diamond Heat Spreaders

Lab-grown diamond heat spreaders are becoming attractive solutions compared to traditional copper heat spreaders due to their high thermal conductivity, the ability to directly bond them on silicon, and allow for an ultra-thin silicon layer. Researchers have developed various thermal models and prototypes of lab-grown diamond heat spreaders to evaluate their cooling performance and heat spreading ability. The majority of existing thermal models are built using finite-element method (FEM) based simulators such as COMSOL and ANSYS. However, such commercial simulators are computationally expensive and lead to long solution times along with large memory requirements. These limitations make commercial simulators unsuitable for evaluating numerous design alternatives or runtime scenarios for real-world high-performance processors. Because of this modeling challenge, none of the existing works have evaluated the thermal behavior of lab-grown diamond heat spreaders on real-world high-performance processors running realistic application benchmarks. Recently, we have developed a parallel compact thermal simulator, PACT, that is able to carry out fast and accurate steady-state and transient thermal simulations and can be extended to support emerging integration and cooling technologies. In this paper, we use PACT to evaluate the steady-state and transient cooling performance of lab-grown diamond heat spreaders against traditional copper heat spreaders on various real-world high-performance processors (e.g., Intel i7 6950X, IBM Power9, and PicoSoC). By using PACT with architectural performance and power simulators such as Sniper and McPAT, we are able to run transient simulations with realistic benchmarks. Simulation results show that lab-grown diamond heat spreaders achieve maximum temperature and thermal gradient reductions of up to 26.73 °C and 13.75 °C when compared to traditional copper heat spreaders, respectively. The maximum steady-state and transient simulation times of PACT for the real-world high-performance chips and realistic applications used in our experiments are 259 s and 22 min, respectively.

Performance and Manufacturing of Silicon-Based Vapor Chambers

This paper reviews recent progress in the development of silicon-based vapor chambers for heat spreading in electronic packages. Effective hotspot mitigation is an increasingly challenging issue in electronics thermal management, and the use of silicon vapor chambers creates opportunities for thermal-expansion matched, high performance heat spreaders that can be directly integrated with the semiconductor die. While silicon microheat pipes have been extensively studied as one-dimensional heat transport mechanisms for heat routing in semiconductor substrates, silicon vapor chambers require special consideration and different manufacturing approaches due to the different heat transport configurations involved. The following review therefore provides an overview on the evolution of silicon vapor chambers in terms of fabrication strategies and performance characterization. Particular focus is given to opportunities and challenges associated with using silicon as the vapor chamber envelope material rather than more traditional metal-based vapor chambers, such as the ability to optimize the wick geometry with greater fidelity and issues with manufacturing scalability.