Drainage-Induced Structural Degradation of Thermal Greases

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In flip-chip microelectronics packages, heat removal from the backside of the chip is important for device thermal management. This is commonly achieved by applying a thermal interface material between the chip and heat dissipating component, which can be a heat spreader or heat sink. [In packages that contain both a heat spreader and heat sink, a thermal interface material is applied at the two interfaces, i.e. between the chip and spreader and between the spreader and sink. ] The thermal interface material (TIM) must be able to conform to the topography of the mating surfaces thereby filling in localized interstitial spaces between their asperity contacts to reduce the thermal contact resistance. Consequently, fluidity is an important characteristic of any TIM. TIMs must also easily deform to accommodate mechanical stresses that arise from thermal expansion mismatches between various materials in the package. Thermal greases are designed with these characteristics in mind and are used in many high-performance microelectronics packages.

By: Ijeoma Nnebe; Claudius Feger

Published in: IEEE Transactions on Advanced Packaging, volume 31, (no 3), pages 512-18 in 2008


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