Thesis (M.Eng.)--Memorial University of Newfoundland, 2003. / Bibliography: leaves 117-123. Also available online.

Orientador: Mauricio Araújo Zanardi / Banca: Petrônio Masanobu Tanisho / Banca: Janaína Ferreira Batista Leal / Resumo: Neste trabalho foi estudada a utilização de tubos de calor no resfriamento de componentes eletrônicos. Foram realizados testes experimentais, utilizando aparato experimental construído especialmente para esta finalidade, com um tubo de calor plano como sorvedouro de calor para um componente elétrico. Diversas condições de operação foram simuladas variando-se a potência dissipada pelo componente e o ângulo de inclinação do sistema. Foi simulada também a falha do tubo de calor por vazamento do fluído de trabalho e os resultados foram comparados com os obtidos com o tubo funcionando perfeitamente. Grandes variações de temperatura foram encontrados o que demonstra a possibilidade de dano ao componente. Modelos numéricos de simulação foram comparados com os dados experimentais. Apesar da simplicidade dos mesmos, uma boa concordância foi encontrada. / Abstract: In this work the use of heat sink for cooling of electronic components was investigated. Experimental tests were perfomed using an experimental apparatus especially developed for this objective. Many different operational conditions were tested varying the power supplied to the component and the inclination angle of the system. The performance of the heat pipe, under failure conditions due to working fluid leakage, was also tested and the results were compared with the ones for the heat pipe in perfect conditions. High temperature differences were archieved what confirms the risks of component failure. Numerical models for both conditions were constructed and the results were compared with the experimental data. Although the simplicity of the models the results showed good agreement. / Mestre

Made available in DSpace on 2014-06-11T19:30:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-04Bitstream added on 2014-06-13T18:47:30Z : No. of bitstreams: 1 abreu_lb_me_guara.pdf: 844401 bytes, checksum: 1328c920a0dadb5dd131f7465a4292e6 (MD5) / Neste trabalho foi estudada a utilização de tubos de calor no resfriamento de componentes eletrônicos. Foram realizados testes experimentais, utilizando aparato experimental construído especialmente para esta finalidade, com um tubo de calor plano como sorvedouro de calor para um componente elétrico. Diversas condições de operação foram simuladas variando-se a potência dissipada pelo componente e o ângulo de inclinação do sistema. Foi simulada também a falha do tubo de calor por vazamento do fluído de trabalho e os resultados foram comparados com os obtidos com o tubo funcionando perfeitamente. Grandes variações de temperatura foram encontrados o que demonstra a possibilidade de dano ao componente. Modelos numéricos de simulação foram comparados com os dados experimentais. Apesar da simplicidade dos mesmos, uma boa concordância foi encontrada. / In this work the use of heat sink for cooling of electronic components was investigated. Experimental tests were perfomed using an experimental apparatus especially developed for this objective. Many different operational conditions were tested varying the power supplied to the component and the inclination angle of the system. The performance of the heat pipe, under failure conditions due to working fluid leakage, was also tested and the results were compared with the ones for the heat pipe in perfect conditions. High temperature differences were archieved what confirms the risks of component failure. Numerical models for both conditions were constructed and the results were compared with the experimental data. Although the simplicity of the models the results showed good agreement.

Forced air cooling of electronic packages is enhanced through the use of extended surfaces or heat sinks that reduce boundary resistance allowing heat generating devices to operate at lower temperatures, thereby improving reliability. Unfortunately, the clearance zones or bypass regions surrounding the heat sink, channel some of the cooling air mass away from the heat sink, making it difficult to accurately estimate thermal performance. The design of an "optimized" heat sink requires a complete knowledge of all thermal resistances between the heat source and the ambient air, therefore, it is imperative that the boundary resistance is properly characterized, since it is typically the controlling resistance in the path. Existing models are difficult to incorporate into optimization routines because they do not provide a means of predicting flow bypass based on information at hand, such as heat sink geometry or approach velocity. <br /><br /> A procedure is presented that allows the simultaneous optimization of heat sink design parameters based on a minimization of the entropy generation associated with thermal resistance and fluid pressure drop. All relevant design parameters such as geometric parameters of a heat sink, source and bypass configurations, heat dissipation, material properties and flow conditions can be simultaneously optimized to characterize a heat sink that minimizes entropy generation and in turn results in a minimum operating temperature of an electronic component. <br /><br /> An analytical model for predicting air flow and pressure drop across the heat sink is developed by applying conservation of mass and momentum over the bypass regions and in the flow channels established between the fins of the heat sink. The model is applicable for the entire laminar flow range and any type of bypass (side, top or side and top both) or fully shrouded configurations. During the development of the model, the flow was assumed to be steady, laminar, developing flow. The model is also correlated to a simple equation within 8% confidence level for an easy implementation into the entropy generation minimization procedure. The influence of all the resistances to heat transfer associated with a heat sink are studied, and an order of magnitude analysis is carried out to include only the influential resistances in the thermal resistance model. Spreading and material resistances due to the geometry of the base plate, conduction and convection resistances associated with the fins of the heat sink and convection resistance of the wetted surfaces of the base plate are considered for the development of a thermal resistance model. The thermal resistance and pressure drop model are shown to be in good agreement with the experimental data over a wide range of flow conditions, heat sink geometries, bypass configurations and power levels, typical of many applications found in microelectronics and related fields. Data published in the open literature are also used to show the flexibility of the models to simulate a variety of applications. <br /><br /> The proposed thermal resistance and pressure drop model are successfully used in the entropy generation minimization procedure to design a heat sink with bypass for optimum dimensions and performance. A sensitivity analysis is also carried out to check the influence of bypass configurations, power levels, heat sink materials and the coverage ratio on the optimum dimensions and performance of a heat sink and it is found that any change in these parameters results in a change in the optimized heat sink dimensions and flow conditions associated with the application for optimal heat sink performance.

Forced air cooling of electronic packages is enhanced through the use of extended surfaces or heat sinks that reduce boundary resistance allowing heat generating devices to operate at lower temperatures, thereby improving reliability. Unfortunately, the clearance zones or bypass regions surrounding the heat sink, channel some of the cooling air mass away from the heat sink, making it difficult to accurately estimate thermal performance. The design of an "optimized" heat sink requires a complete knowledge of all thermal resistances between the heat source and the ambient air, therefore, it is imperative that the boundary resistance is properly characterized, since it is typically the controlling resistance in the path. Existing models are difficult to incorporate into optimization routines because they do not provide a means of predicting flow bypass based on information at hand, such as heat sink geometry or approach velocity. <br /><br /> A procedure is presented that allows the simultaneous optimization of heat sink design parameters based on a minimization of the entropy generation associated with thermal resistance and fluid pressure drop. All relevant design parameters such as geometric parameters of a heat sink, source and bypass configurations, heat dissipation, material properties and flow conditions can be simultaneously optimized to characterize a heat sink that minimizes entropy generation and in turn results in a minimum operating temperature of an electronic component. <br /><br /> An analytical model for predicting air flow and pressure drop across the heat sink is developed by applying conservation of mass and momentum over the bypass regions and in the flow channels established between the fins of the heat sink. The model is applicable for the entire laminar flow range and any type of bypass (side, top or side and top both) or fully shrouded configurations. During the development of the model, the flow was assumed to be steady, laminar, developing flow. The model is also correlated to a simple equation within 8% confidence level for an easy implementation into the entropy generation minimization procedure. The influence of all the resistances to heat transfer associated with a heat sink are studied, and an order of magnitude analysis is carried out to include only the influential resistances in the thermal resistance model. Spreading and material resistances due to the geometry of the base plate, conduction and convection resistances associated with the fins of the heat sink and convection resistance of the wetted surfaces of the base plate are considered for the development of a thermal resistance model. The thermal resistance and pressure drop model are shown to be in good agreement with the experimental data over a wide range of flow conditions, heat sink geometries, bypass configurations and power levels, typical of many applications found in microelectronics and related fields. Data published in the open literature are also used to show the flexibility of the models to simulate a variety of applications. <br /><br /> The proposed thermal resistance and pressure drop model are successfully used in the entropy generation minimization procedure to design a heat sink with bypass for optimum dimensions and performance. A sensitivity analysis is also carried out to check the influence of bypass configurations, power levels, heat sink materials and the coverage ratio on the optimum dimensions and performance of a heat sink and it is found that any change in these parameters results in a change in the optimized heat sink dimensions and flow conditions associated with the application for optimal heat sink performance.

This study has two main objectives: The performance evaluation of existing microchannel heat sinks using a CFD model, and the dimensional optimization of various heat sinks by minimizing the total thermal resistance. For the analyses, the geometric modeling is performed using the software GAMBIT while the thermal analysis is performed with FLUENT. The developed model compares very well with those available in the literature. Eight different metal-polymer microchannel heat sinks are analyzed using the model to find out how much heat could be provided to the systems while keeping the substrate temperatures below 85&deg / C under a constant pumping power requirement. Taking the objective function as the total thermal resistance, the optimum geometries have been obtained for the mentioned metal-polymer heat sinks as well as more conventional silicon ones. The results of the optimization code agreed very well with available ones in the literature. In the optimization study, the Intel Core i7-900 Desktop Processor Extreme Edition Series is considered as a reference processor which is reported to dissipate 130 W of heat and to have chip core dimensions of 1.891 cm &times / 1.44 cm. A dimensional optimization study has been performed for various copper and silicon microchannel heat sinks to cool down this processor. To the best of the author&rsquo / s knowledge, this study contributes to the literature in that, as opposed to the available analytical microchannel optimization studies considering constant thermophysical properties at the fluid inlet temperature, the properties are evaluated at the area weighted average of the fluid inlet and iteratively calculated outlet temperatures. Moreover, the effects of the thermal and hydrodynamic entrance regions on heat transfer and flow are also investigated.

The thermal interface layer can be a limiting element in the cooling of microelectronic devices. Conventional solders, pastes and pads are no longer sufficient to handle the high heat fluxes associated with connecting the device to the sink. Carbon nanotubes(CNTs) have been proposed as a possible thermal interface material(TI M), due to their thermal and mechanical properties, and prior research has established the effectiveness of vertically arranged CNT arrays to match the capabilities of the best conventional TIMs. However, to reach commercial applicability, many improvements need to be made in terms of improving thermal and mechanical properties as well as cost and manufacturing ease of the layer. Prior work demonstrated a simple method to transfer and bond CNT arrays through the use of a nanometer thin layer of gold as a bonding layer. This study sought to improve on that technique. By controlling the rate of deposition, the bonding temperature was reduced. By using different metals and thinner layers, the potential cost of the technique was reduced. Through the creation of a patterned array, a phase change element was able to be incorporated into the technique. The various interfaces created are characterized mechanically and thermally.

Advancements in the semiconductor industry have lead to the miniaturization of components and increased power densities, resulting in thermal management issues. In response to this shift, finding multifunctional materials with excellent thermal conductivity and tailored electrical properties are becoming increasingly important. For this research thesis, three different studies were conducted to develop and characterize thermally conductive polymer composites. In the first study, a PPS matrix was combined with different types of carbon-based fillers to determine the effects of filler’s size, shape, and orientation on thermal conductivity. In the second study, effects of adding ceramic- and carbon- based fillers on the tailored thermal and electrical properties of composites were investigated. Lastly, the possibility of improving the thermal conductivity by introducing and aligning polymer fibers in the composites was investigated. The composites were characterized with respect to their physical, thermal, and electrical properties to propose possibilities of application in the electronic packaging industries.

Advancements in the semiconductor industry have lead to the miniaturization of components and increased power densities, resulting in thermal management issues. In response to this shift, finding multifunctional materials with excellent thermal conductivity and tailored electrical properties are becoming increasingly important. For this research thesis, three different studies were conducted to develop and characterize thermally conductive polymer composites. In the first study, a PPS matrix was combined with different types of carbon-based fillers to determine the effects of filler’s size, shape, and orientation on thermal conductivity. In the second study, effects of adding ceramic- and carbon- based fillers on the tailored thermal and electrical properties of composites were investigated. Lastly, the possibility of improving the thermal conductivity by introducing and aligning polymer fibers in the composites was investigated. The composites were characterized with respect to their physical, thermal, and electrical properties to propose possibilities of application in the electronic packaging industries.

Thesis (Ph.D.)--Rochester Institute of Technology, 2008. / Typescript. Includes bibliographical references (leaves 170-176).