Comparison of Carbon-based Nanostructures with Commercial Products as Thermal Interface Materials
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Comparison of Carbon-based Nanostructures with Commercial Products as Thermal Interface Materials Michael Rosshirt, Drazen Fabris, Christopher Cardenas, Patrick Wilhite, Thanh Tu, and Cary Y. Yang Center for Nanostructures, Santa Clara University, Santa Clara, CA 95053 ABSTRACT Heat dissipation in electronics packaging can be highly dependent on Thermal Interface Materials (TIM). TIM contact, compliance, and conductivity can be the dominant limiting factors in the overall conduction heat transfer across the interface. Mixing multiwall Carbon Nanotubes (CNTs), which have high thermal conductivity, with other thermally conducting materials holds great promise as TIM fillers and has been shown to have higher thermal performance than commercial TIM [1]. Such mixtures possess greater thermal conductivity as a result of increased thermal conduction paths through highly conductive, high aspect ratio CNTs. In this work, we develop and test an advanced apparatus based on the ASTM D5470-06 standard to measure thermal interface resistance. Our experimental findings quantify the thermal performance trends of industry-standard TIM Arctic Silver® 5 along with hybrid TIM mixtures of Arctic Silver®5 and varying weight ratios of CNTs. Early experimental findings show that Arctic Silver®5 mixed with 0.5 to 1% multiwall CNT by weight may improve thermal conductivity over pure Arctic Silver®5.The goal of this research is to investigate the viability of integrating CNTs with commercial products as improved TIM for electronic cooling in chip packages. INTRODUCTION Thermal management is a core concern of integrated circuit design and electronic packaging. Minimizing the thermal contact resistance (TCR) in particular is a crucial aspect of thermal management design in electron-based devices. When two surfaces are placed in contact with one another, the net heat transfer across the interface is dictated, in part, by the TCR between the two materials. At the microscale engineering surfaces are rough and inundated with asperities. The effective contact area for conduction heat transfer is constricted to the physical contact made between the microscale peaks of the two surfaces, with the remaining interstitial spaces filled typically by air (Figure 1.a) [2]. TIM are commonly inserted at the interface to increase the overall conduction area and replace much of the insulating air with a more conductive material to reduce the TCR. In general, the two most important qualities for thermal TIM to possess are high thermal conductivity and high compliance [3]. There are few homogeneous materials, which exhibit both properties under natural operating conditions. Consequently most commonly used TIM are composite thermal greases, composed of highly conductive particle fillers, which form percolation paths through a highly compliant matrix material of silicone or synthetic oils [4] (Figure 1.b). Carbon nanotubes have garnered substantial interest throughout the engineering community because of their exceptional electrical, thermal and physica
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