Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)最新文献

{"title":"Effects of aging on shear cyclic stress strain and fatigue behaviors of lead free solder joints","authors":"M. Mustafa, J. Roberts, J. Suhling, P. Lall","doi":"10.1109/ITHERM.2014.6892274","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892274","url":null,"abstract":"Solder materials in electronic packages are often subjected to thermal cycling, either during their application in products or during accelerated life qualification testing. Cyclic temperatures cause the solder joints to be subjected to cyclic mechanical stresses and strains due to the mismatches in the thermal expansion coefficients of the assembly materials. Such loads lead to thermomechanical fatigue that results in damage accumulation, crack initiation and propagation, and eventual failure. The authors have extensively examined the effects of isothermal aging on solder stress-strain and creep (constitutive) behavior. However, there have been no prior investigations on aging effects on solder fatigue behavior. Aging leads to both grain and phase coarsening, and can cause recrystallization at Sn grain boundaries. Such changes are closely tied to the damage that occurs during cyclic mechanical loading.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"15 1","pages":"142-151"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87185413","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of droplet diameter on the Leidenfrost temperature of laser processed multiscale structured surfaces","authors":"Anton Hassebrook, C. Kruse, Chris Wilson, T. Anderson, C. Zuhlke, D. Alexander, G. Gogos, S. Ndao","doi":"10.1109/ITHERM.2014.6892316","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892316","url":null,"abstract":"In this paper, an experimental investigation of the effects of droplet diameters on the Leidenfrost temperature and its shifts has been carried out. Tests were conducted on a 304 stainless steel polished surface and a stainless steel surface which was processed by a femtosecond laser to form Above Surface Growth (ASG) nano/microstructures. To determine the Leidenfrost temperatures, the droplet lifetime method was employed for both the polished and processed surfaces. A precision dropper was used to vary the size of droplets from 1.5 to 4 millimeters. The Leidenfrost temperature was shown to display shifts as high as 85 °C on the processed surface over the range of droplet sizes, as opposed to a 45 °C shift on the polished surface. The difference between the shifts was attributed to the nature of the force balance between dynamic pressure of droplets and vapor pressure of the insulating vapor layer.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"7 1","pages":"452-457"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87216084","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Flat heat pipe performance thresholds at ultra-thin form factors","authors":"Yashwanth Yadavalli, J. Weibel, S. Garimella","doi":"10.1109/ITHERM.2014.6892326","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892326","url":null,"abstract":"Improved-efficiency heat spreaders must address ergonomic- and performance-driven thermal management demands of electronic devices of increasingly thin form factor. Heat pipes offer a potential high-conductance solution, but performance limitations unique to sub-millimeter thickness devices must be characterized. Using a reduced-order, one-dimensional resistance network and a two-dimensional numerical model, the thermal resistance of a flat heat pipe is benchmarked against a solid heat spreader as a function of geometry and power input. The reduced-order model enables a broad parametric study and analytical formulation of performance limitations, while the higher fidelity numerical approach is used to assess the accuracy of the thermal resistance network near these limits. The form factors and operating conditions for which a heat pipe is more effective than a solid heater spreader are identified. Two of the bounding performance limits have been commonly discussed in prior analyses - a capillary wicking limit and an increase in the heat pipe thermal resistance relative to the solid heat spreader at very large thicknesses. A third vapor-phase threshold is observed when the thickness is reduced below a critical limit. At this threshold, the vapor-phase thermal resistance imposed by the saturation pressure/temperature gradient in the heat pipe causes a crossover in the thermal resistance relative to a solid heat spreader. Devices are susceptible to this performance threshold at very low power inputs that would not otherwise induce a capillary limitation. Accurate prediction of this threshold is an important consideration in the selection and design of ultra-thin heat pipes.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"62 1","pages":"527-534"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90403472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modeling temperature development of Li-Ion battery packs in hybrid refuse truck operating at different ambient conditions","authors":"P. Coman, C. Veje","doi":"10.1109/ITHERM.2014.6892371","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892371","url":null,"abstract":"This paper presents a dynamic model for simulating the heat dissipation and the impact of Phase Change Materials (PCMs) on the peak temperature in Lithium-ion batteries during discharging operation of a hybrid truck under different ambient temperatures.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"18 1","pages":"862-869"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81838652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Graphene-enhanced phase change materials for thermal management of battery packs","authors":"P. Goli, A. Balandin","doi":"10.1109/ITHERM.2014.6892442","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892442","url":null,"abstract":"Graphene and few-layer graphene reveal exceptionally high thermal conduction properties, which can be used for thermal management. Here we show that incorporation of graphene and few-layer graphene to the hydrocarbon-based phase change material allows one to increase its thermal conductivity by more than two orders of magnitude while preserving its latent heat storage ability. A combination of the sensible and latent heat storage together with the improved heat conduction results in a composite material with the exceptional thermal management capabilities. We show that the graphene-enhanced phase change material can substantially improve the thermal management of Li-ion and other advanced types o f batteries.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"21 1","pages":"1390-1393"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87544180","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermal characterization of nanostructured superlattices of TiN/TaN: Applications as electrodes in Phase Change Memory","authors":"A. Sood, S. Eryilmaz, R. Jeyasingh, Jungwan Cho, M. Asheghi, H. Wong, K. Goodson","doi":"10.1109/ITHERM.2014.6892358","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892358","url":null,"abstract":"Phase Change Memory (PCM) technology relies on the contrast in electrical resistance between the amorphous and crystalline states of a chalcogenide active material. Electrical PCM devices use Joule heating by short pulses of current to induce phase change, such that the amount of heat injected into the active material and the rate of cooling determine the final state of material formed. In this paper, we explore the possibility of replacing commonly used TiN electrodes by nanostructured superlattices of TiN/TaN that have lower through-plane thermal conductivity, in order to improve the confinement of heat within the phase change material and achieve a reduction in the device programming current. TiN(m)/TaN(n) superlattices were grown on Si substrates using physical vapor deposition, m and n representing the intra-period thicknesses of TiN and TaN layers respectively (m, n: 5 - 25 nm). The through-plane thermal conductivity of these superlattices was measured using time-domain thermoreflectance (TDTR), and was found to be in the range 1.5 - 2 W/m-K, a reduction from the bulk conductivity of TiN (~ 19 W/m-K) by up to a factor of 10. Transmission Electron Microscopy (TEM) was used to characterize film morphology, pointing to additional sources of carrier scattering that might lead to this reduction in conductivity, and suggesting avenues for optimization of growth parameters. The low thermal conductivity of the superlattice films opens up the possibility of using them as bottom electrodes in PCM, towards the goal of reducing power consumption and improving device packing density. A simplified 1D thermal model predicts that reductions in programming current b y ~75% are possible.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"7 1","pages":"765-770"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84253680","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"CHF enhancement of Al2O3, TiO2 and Ag nanofluids and effect of nucleate pool boiling time","authors":"M. S. Ulcay","doi":"10.1109/ITHERM.2014.6892357","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892357","url":null,"abstract":"Nanofluids are nanometer sized suspended particles in water or other base fluids. They are used for their increased nucleate boiling critical heat flux (CHF) values far beyond compared to pure water or base fluid. Therefore pool boiling heat transfer tests are performed to understand increase in CHF. The pool boiling characteristics and critical heat flux enhancement using nanofluids of dilute dispersions of alumina, titania and silver are studied. High heat transfer rates with high critical heat flux achieved with modest nanoparticle concentrations (<;0.1% by volume). Heater wire used in CHF tests were only on 50μm in diameter. Change in surface structure of heater wire causes increase in CHF. Surface of the heater is covered with porous layer of nanoparticles during nucleate boiling. It is determined to investigate the effects of nucleate boiling time (coating time) during which the heater wire is exposed to deposition of nanoparticles. Results of this study presented that there is a non-linear relationship between the coating time and CHF for short periods of coating times, up to 30 seconds; however this effect loses its impact if the coating duration is elongated. It was also showed that longer periods of coating time increased the CHF but not drastically and the relationship between coating time and CHF is no longer non-linear and can be approximated by a linear line. This study represents an important step in understanding the relationship between CHF and the optimum amount of nanoparticle deposition or amount of porous layer of nanoparticles formed on heater surface with respect to nucleate boiling (coating)/time dependency.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"35 1 1","pages":"756-764"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88072659","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Parametric design of a low-profile, forced convection heat sink for high-power, high-density LED arrays","authors":"K. Geisler","doi":"10.1109/ITHERM.2014.6892263","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892263","url":null,"abstract":"Solid state light sources, such as light emitting diodes (LEDs), provide many inherent benefits and will dominate the lighting industry in the coming decades. While much of the industry is currently focused on packaging LED technology in standardized 19th century form factors to address the massive installed base of traditional fixtures, the unique characteristics of solid state devices can and will be exploited to produce new luminaire types and new paradigms in lighting design for the 21st century and beyond. Since operating temperatures directly impact energy efficiency, output spectrum, and product lifetime, thermal management is a key linkage in the interdependence of application requirements, design trade-offs, and performance characteristics. This paper details the design of a high-power, high-density LED-based light source for large-scale lighting applications. In particular, a low-profile folded-fin copper heat sink was designed for forced-convection cooling by an array of 38 mm × 38 mm fans. Heat sink dimensions, including fin thickness, fin spacing, heat sink length, and heat sink base thickness to fin height ratio, were varied within form factor constraints and manufacturing limits to produce a suitable thermal solution for a 60,000+ lumen, 50.8 mm × 50.8 mm LED array dissipating 600 W of heat. Results of numerical, analytical, and experimental investigations demonstrate that LED junction temperatures can be maintained below maximum operating limits in a 45°C ambient.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"7 1","pages":"47-58"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87047368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Novel power electronics three-dimensional heat exchanger","authors":"K. Bennion, J. Cousineau, J. Lustbader, S. Narumanchi","doi":"10.1109/ITHERM.2014.6892398","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892398","url":null,"abstract":"Electric-drive systems, which include electric machines and power electronics, are a key enabling technology to meet increasing automotive fuel economy standards, improve energy security, address environmental concerns, and support economic development. Enabling cost-effective electric-drive systems requires reductions in inverter power semiconductor area, which increases challenges associated with heat removal. In this paper, we demonstrate an integrated approach to the design of thermal management systems for power semiconductors that matches the passive thermal resistance of the packaging with the active convective cooling performance of the heat exchanger. The heat exchanger concept builds on existing semiconductor thermal management improvements described in literature and patents, which include improved bonded interface materials, direct cooling of the semiconductor packages, and double-sided cooling. The key difference in the described concept is the achievement of high heat transfer performance with less aggressive cooling techniques by optimizing the passive and active heat transfer paths. An extruded aluminum design was selected because of its lower tooling cost, higher performance, and scalability in comparison to cast aluminum. Results demonstrated a 102% heat flux improvement and a package heat density improvement over 30%, which achieved the thermal performance targets.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"99 1","pages":"1055-1063"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85815950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of moisture exposure on the mechanical behavior of flip chip underfills in microelectronic packaging","authors":"N. Chhanda, J. Suhling, P. Lall","doi":"10.1109/ITHERM.2014.6892300","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892300","url":null,"abstract":"Reliable, consistent, and comprehensive material property data are needed for microelectronics encapsulants for the purpose of mechanical design, reliability assessment, and process optimization of electronic packages. Since the vast majority of contemporary underfills are epoxy based, they have the propensity to absorb moisture, which can lead to undesirable changes in their mechanical and adhesion behaviors. In this study, the effects of moisture adsorption on the stress-strain behavior of an underfill encapsulant were evaluated experimentally and theoretically. A novel specimen preparation procedure has been used to manufacture 60 × 3 mm uniaxial tension test samples, with a specified thickness of 0.5 mm. The test specimens were dispensed and cured with production equipment using the same conditions as those used in actual flip chip assembly, and no release agent was required to extract them from the mold. The fabricated uniaxial test specimens were then exposed in an adjustable thermal and humidity chamber to combined hygrothermal exposures at 85 C and 85% RH for various durations. After moisture preconditioning, a microscale tension-torsion testing machine was used to evaluate the complete stress-strain behavior of the material at several temperatures (T = 25, 50, 75, 100 and 125 C). The viscoelastic mechanical response of the underfill encapsulant has also been characterized via creep testing for a large range of applied stress levels and temperatures before moisture exposure. From the recorded results, it was found that the moisture exposures strongly affected the mechanical properties of the tested underfill including the initial elastic modulus and ultimate tensile stress. With the obtained mechanical property data, a three-dimensional linear viscoelastic model based on Prony series response functions has been applied to fit the stress-strain and creep data, and excellent correlation had been obtained for samples with and without moisture exposure. The effects of moisture were built into the model using the observed changes in the glass transition temperature within the WLF Shift Function.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"6 1","pages":"333-345"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85478356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}