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Author: Muhammad Omar Memon Publisher: ISBN: Category : Carbon fibers Languages : en Pages : 133
Book Description
The power density of electronic packages has substantially increased. The thermal interface resistance involves more than 50% of the total thermal resistance in current high-power packages. The portion of the thermal budget spent on interface resistance is growing because die-level power dissipation densities are projected to exceed 100 W/cm2 in near future. There is an urgent need for advanced thermal interface materials (TIMs) that would achieve order-of-magnitude improvement in performance. Carbon nanotubes and nanofibers have received significant attention in the past because of its small diameter and high thermal conductivity. The present study is intended to overcome the shortcomings of commercially used thermal interface materials by introducing a compliant material which would conform to the mating surfaces and operate at higher temperatures. Thin film "labeled buckypaper" of CNF based Materials was processed and optimized. An experimental setup was designed to test processed materials in terms of thermal impedance as a function of load and materials density, thickness and thermal conductivity. Results show that the thermal impedance decreased in conjunction with the increasing heat-treatment temperature of CNFs. TIM using heat treated CNF showed a significant decrement of 54% in thermal impedance. Numerical simulations confirmed the validity of the experimental model. A parametric study was carried out which showed significant decrement in the thermal resistance with the decrease in TIM thickness. A transient spike power was carried out using two conditions; uniform heat pulse of 24 Watts, and power spikes of 24-96 Watts. The results show that heat treated CNF was 12% more temperature resistant than direct contact with more than 50% enhancement in heat transport across it.
Author: Muhammad Omar Memon Publisher: ISBN: Category : Carbon fibers Languages : en Pages : 133
Book Description
The power density of electronic packages has substantially increased. The thermal interface resistance involves more than 50% of the total thermal resistance in current high-power packages. The portion of the thermal budget spent on interface resistance is growing because die-level power dissipation densities are projected to exceed 100 W/cm2 in near future. There is an urgent need for advanced thermal interface materials (TIMs) that would achieve order-of-magnitude improvement in performance. Carbon nanotubes and nanofibers have received significant attention in the past because of its small diameter and high thermal conductivity. The present study is intended to overcome the shortcomings of commercially used thermal interface materials by introducing a compliant material which would conform to the mating surfaces and operate at higher temperatures. Thin film "labeled buckypaper" of CNF based Materials was processed and optimized. An experimental setup was designed to test processed materials in terms of thermal impedance as a function of load and materials density, thickness and thermal conductivity. Results show that the thermal impedance decreased in conjunction with the increasing heat-treatment temperature of CNFs. TIM using heat treated CNF showed a significant decrement of 54% in thermal impedance. Numerical simulations confirmed the validity of the experimental model. A parametric study was carried out which showed significant decrement in the thermal resistance with the decrease in TIM thickness. A transient spike power was carried out using two conditions; uniform heat pulse of 24 Watts, and power spikes of 24-96 Watts. The results show that heat treated CNF was 12% more temperature resistant than direct contact with more than 50% enhancement in heat transport across it.
Author: Wei Lin Publisher: ISBN: Category : Microelectronic packaging Languages : en Pages :
Book Description
As the integration scale of transistors/devices in a chip/system keeps increasing, effective cooling has become more and more important in microelectronics. To address the thermal dissipation issue, one important solution is to develop thermal interface materials with higher performance. Carbon nanotubes, given their high intrinsic thermal and mechanical properties, and their high thermal and chemical stabilities, have received extensive attention from both academia and industry as a candidate for high-performance thermal interface materials.\r : The thesis is devoted to addressing some challenges related to the potential application of carbon nanotubes as thermal interface materials in microelectronics. These challenges include: 1) controlled synthesis of vertically aligned carbon nanotubes on various bulk substrates via chemical vapor deposition and the fundamental understanding involved; 2) development of a scalable annealing process to improve the intrinsic properties of synthesized carbon nanotubes; 3) development of a state-of-art assembling process to effectively implement high-quality vertically aligned carbon nanotubes into a flip-chip assembly; 4) a reliable thermal measurement of intrinsic thermal transport property of vertically aligned carbon nanotube films; 5) improvement of interfacial thermal transport between carbon nanotubes and other materials.\r : The major achievements are summarized.\r : 1. Based on the fundamental understanding of catalytic chemical vapor deposition processes and the growth mechanism of carbon nanotube, fast synthesis of high-quality vertically aligned carbon nanotubes on various bulk substrates (e.g., copper, quartz, silicon, aluminum oxide, etc.) has been successfully achieved. The synthesis of vertically aligned carbon nanotubes on the bulk copper substrate by the thermal chemical vapor deposition process has set a world record. In order to functionalize the synthesized carbon nanotubes while maintaining their good vertical alignment, an in situ functionalization process has for the first time been demonstrated. The in situ functionalization renders the vertically aligned carbon nanotubes a proper chemical reactivity for forming chemical bonding with other substrate materials such as gold and silicon.\r : 2. An ultrafast microwave annealing process has been developed to reduce the defect density in vertically aligned carbon nanotubes. Raman and thermogravimetric analyses have shown a distinct defect reduction in the CNTs annealed in microwave for 3 min. Fibers spun from the as-annealed CNTs, in comparison with those from the pristine CNTs, show increases of ~35% and ~65%, respectively, in tensile strength (~0.8 GPa) and modulus (~90 GPa) during tensile testing; an ~20% improvement in electrical conductivity (~80000 S m−1) was also reported. The mechanism of the microwave response of CNTs was discussed. Such an microwave annealing process has been extended to the preparation of reduced graphene oxide.\r : 3. Based on the fundamental understanding of interfacial thermal transport and surface chemistry of metals and carbon nanotubes, two major transfer/assembling processes have been developed: molecular bonding and metal bonding. Effective improvement of the interfacial thermal transport has been achieved by the interfacial bonding.\r : 4. The thermal diffusivity of vertically aligned carbon nanotube (VACNT, multi-walled) films was measured by a laser flash technique, and shown to be ~30 mm2 s−1 along the tube-alignment direction. The calculated thermal conductivities of the VACNT film and the individual CNTs are ~27 and ~540 W m−1 K−1, respectively. The technique was verified to be reliable although a proper sampling procedure is critical. A systematic parametric study of the effects of defects, buckling, tip-to-tip contacts, packing density, and tube-tube interaction on the thermal diffusivity was carried out. Defects and buckling decreased the thermal diffusivity dramatically. An increased packing density was beneficial in increasing the collective thermal conductivity of the VACNT film; however, the increased tube-tube interaction in dense VACNT films decreased the thermal conductivity of the individual CNTs. The tip-to-tip contact resistance was shown to be ~1×10−7 m2 K W−1. The study will shed light on the potential application of VACNTs as thermal interface materials in microelectronic packaging.\r : 5. A combined process of in situ functionalization and microwave curing has been developed to effective enhance the interface between carbon nanotubes and the epoxy matrix. Effective medium theory has been used to analyze the interfacial thermal resistance between carbon nanotubes and polymer matrix, and that between graphite nanoplatlets and polymer matrix.
Author: Jihong Al-Ghalith Publisher: Springer ISBN: 3319738828 Category : Science Languages : en Pages : 88
Book Description
The book introduces modern atomistic techniques for predicting heat transfer in nanostructures, and discusses the applications of these techniques on three modern topics. The study of heat transport in screw-dislocated nanowires with low thermal conductivity in their bulk form represents the knowledge base needed for engineering thermal transport in advanced thermoelectric and electronic materials, and suggests a new route to lower thermal conductivity that could promote thermoelectricity. The study of high-temperature coating composite materials facilitates the understanding of the role played by composition and structural characterization, which is difficult to approach via experiments. And the understanding of the impact of deformations, such as bending and collapsing on thermal transport along carbon nanotubes, is important as carbon nanotubes, due to their exceptional thermal and mechanical properties, are excellent material candidates in a variety of applications, including thermal interface materials, thermal switches and composite materials.
Author: Marion Odul Okoth Publisher: ISBN: Category : Languages : en Pages :
Book Description
This thesis describes the synthesis of a low modulus, thermally conductive thermal interface materials (TIM) using metal decorated nanotubes as fillers. TIMs are very important in electronics because they act as a thermally-conductive medium for thermal transfer between the interface of a heat sink and an electronic package. The performance of an electronic package decreases with increasing operating temperature, hence, there exists a need to create a TIM which has high thermal conduction to reduce the operating temperature. The TIM in this study is made from metal decorated multi-walled carbon nanotubes (MWCNT) and Vinnapas®BP 600 polymer. The sample was functionalized using mild oxidative treatment with nitric acid (HNO3) or, with N-Methly-2-Pyrrolidone (NMP). The metals used for this experiment were copper (Cu), tin (Sn), and nickel (Ni). The metal nanoparticles were seeded using functionalized MWCNTs as templates. Once seeded, the nanotubes and polymer composites were made with or without sodium dodecylbenzene sulfonate (SDBS), as a surfactant. Thermal conductivity (k) measurement was carried out using ASTM D-5470 method at room temperature. This setup best models the working conditions of a TIM. The TIM samples made for this study showed promise in their ability to have significant increase in thermal conduction while retaining the polymer's mechanical properties. The highest k value that was obtained was 0.72 W/m-K for a well dispersed aligned 5 wt percent Ni@MWCNT sample. The Cu samples underperformed both Ni and Sn samples for the same synthesis conditions. This is because Cu nanoparticles were significantly larger than those of Ni and Sn. They were large enough to cause alloy scattering and too large to attach to the nanotubes. Addition of thermally-conductive fillers, such as exfoliated graphite, did not yield better k results as it sunk to the bottom during drying. The use of SDBS greatly increased the k values of the sample by reducing agglomeration. Increasing the amount of metal@MWCNT wt percent in the sample had negative or no effect to the k values. Shear testing on the sample shows it adheres well to the surface when pressure is applied, yet it can be removed with ease.
Author: Eric Kenji Mayhew Publisher: ISBN: Category : Languages : en Pages : 100
Book Description
The excellent thermal properties of individual carbon nanostructures, such as carbon nanofibers (CNFs), carbon nanotubes (CNTs), and CNT fibers, have provided the impetus for the development of thermal interface materials that can incorporate these nanostructures. The thermal conductivity measurements of individual CNFs, CNT strands, CNT fibers, and CNT-polymer composite fibers are made using a Wollaston wire T-type probe method inside of a scanning electron microscope. CNFs are studied to determine the degree of improvement in structure and thermal conductivity that can be attained by annealing chemical vapor deposition grown CNFs. The results show a significant increase in thermal conductivity of CNFs that are annealed at 2800°C for 20 hours compared with the non-heat-treated samples. Thermal conductivity measurements are also made on CNT fibers, CNT-polymer composite fibers, and individual CNT strands pulled from the CNT fibers. The thermal conductivity values are, by far, the highest reported values for CNT fibers.
Author: Premkumar Nagarathnam Publisher: ISBN: Category : Heat Languages : en Pages :
Book Description
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.
Author: Dimitrios V. Papavassiliou Publisher: Elsevier ISBN: 0128176830 Category : Technology & Engineering Languages : en Pages : 370
Book Description
Nanocomposites with Carbon-based nanofillers (e.g., carbon nanotubes, graphene sheets and nanoribbons etc.) form a class of extremely promising materials for thermal applications. In addition to exceptional material properties, the thermal conductivity of the carbon-based nanofillers can be higher than any other known material, suggesting the possibility to engineer nanocomposites that are both lightweight and durable, and have unique thermal properties. This potential is hindered by thermal boundary resistance (TBR) to heat transfer at the interface between nanoinclusions and the matrix, and by the difficulty to control the dispersion pattern and the orientation of the nanoinclusions. Thermal Behaviour and Applications of Carbon-Based Nanomaterials: Theory, Methods and Applications explores heat transfer in nanocomposites, discusses techniques predicting and modeling the thermal behavior of carbon nanocomposites at different scales, and methods for engineering applications of nanofluidics and heat transfer. The chapters combine theoretical explanation, experimental methods and computational analysis to show how carbon-based nanomaterials are being used to optimise heat transfer. The applications-focused emphasis of this book makes it a valuable resource for materials scientists and engineers who want to learn more about nanoscale heat transfer. Offers an informed overview of how carbon nanomaterials are currently used for nanoscale heat transfer Discusses the major applications of carbon nanomaterials for heat transfer in a variety of industry sectors Details the major computational methods for the analysis of the thermal properties of carbon nanomaterials
Author: Muhammad Omar Memon
Author: Muhammad Omar Memon
Author: Wei Lin
Author: Jihong Al-Ghalith
Author: Marion Odul Okoth
Author: Win Hon Tan
Author: Rahayu Saniman Mohd Zin
Author: Eric Kenji Mayhew
Author: R. L. Rudkin
Author: Premkumar Nagarathnam
Author: Dimitrios V. Papavassiliou