Pub Date : 2014-05-27DOI: 10.1109/ITHERM.2014.6892355
S. Fong, R. Jeyasingh, M. Asheghi, K. Goodson, H. Wong
Recent progress using a micro-thermal stage (MTS) allowed the control the temperature of microstructures with sub-μs time scales. This approach was applied to phase-change memory (PCM) cells to measure thermal material and device properties. In this work, we use the change in MTS thermal resistance to predict changes in the thermal conductivity or thickness of the nearby phase-change layer (PCL). More generally, we show that the MTS can be placed in-situ of a complicated system to measure the thermal properties of a single changing layer. Electrical measurements of the MTS are performed on several different structures with different PCL thicknesses including 35, 70, and 100 nm thick Ge2Sb2Te5 (GST) films, a different phase-change material, and no PCL. Simulations establish the expected relationship between the MTS temperature for different input PCL thermal properties. The simulation approach is then scaled to match the experimental data and predicts the temperature in the PCL for different PCL thermal properties. Additionally, an analytical thermal circuit model is developed to describe the thermal profile of the system. The calibrated simulation and analytical models are thus able to determine thermal properties of the buried PCL by making purely electrical measurements of the MTS.
{"title":"Characterization of phase-change layer thermal properties using a micro-thermal stage","authors":"S. Fong, R. Jeyasingh, M. Asheghi, K. Goodson, H. Wong","doi":"10.1109/ITHERM.2014.6892355","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892355","url":null,"abstract":"Recent progress using a micro-thermal stage (MTS) allowed the control the temperature of microstructures with sub-μs time scales. This approach was applied to phase-change memory (PCM) cells to measure thermal material and device properties. In this work, we use the change in MTS thermal resistance to predict changes in the thermal conductivity or thickness of the nearby phase-change layer (PCL). More generally, we show that the MTS can be placed in-situ of a complicated system to measure the thermal properties of a single changing layer. Electrical measurements of the MTS are performed on several different structures with different PCL thicknesses including 35, 70, and 100 nm thick Ge2Sb2Te5 (GST) films, a different phase-change material, and no PCL. Simulations establish the expected relationship between the MTS temperature for different input PCL thermal properties. The simulation approach is then scaled to match the experimental data and predicts the temperature in the PCL for different PCL thermal properties. Additionally, an analytical thermal circuit model is developed to describe the thermal profile of the system. The calibrated simulation and analytical models are thus able to determine thermal properties of the buried PCL by making purely electrical measurements of the MTS.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"128 11 1","pages":"744-749"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79591728","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}
Pub Date : 2014-05-27DOI: 10.1109/ITHERM.2014.6892302
N. Chhanda, J. Suhling, S. Canumalla
The mechanical properties of polymer materials are often a key concern of the microelectronic packaging industry. The theoretical analysis of stress, strain, and deformation induced in electronic assemblies due to environmental exposures such as moisture adsorption, isothermal aging, and thermal cycling require the complete characterization of mechanical properties and constitutive behavior of the constituent materials. In this work, an experimental investigation has been performed on the effects of moisture adsorption on the stress-strain behavior of polycarbonate materials used in electronic packaging. Uniaxial test specimens were exposed in a controlled temperature and humidity chamber to combined hygrothermal exposures at 60 C and 90% RH, 60 C and 50% RH, and 40 C and 50% 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 = 20 C, 40 C, and 60 C). It was found that moisture exposure strongly affected the mechanical properties of the tested polycarbonate, especially ultimate strain limit. Reversibility tests were also conducted to evaluate whether the degradations in the mechanical properties were recoverable. Upon fully redrying, the material was found to recover most of its original mechanical properties. In addition, optical microscopy was utilized to examine the fracture surfaces of the failed specimens, and observe the influence of moisture exposure.
{"title":"Effects of moisture exposure on the mechanical behavior of polycarbonate materials used in electronic packaging","authors":"N. Chhanda, J. Suhling, S. Canumalla","doi":"10.1109/ITHERM.2014.6892302","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892302","url":null,"abstract":"The mechanical properties of polymer materials are often a key concern of the microelectronic packaging industry. The theoretical analysis of stress, strain, and deformation induced in electronic assemblies due to environmental exposures such as moisture adsorption, isothermal aging, and thermal cycling require the complete characterization of mechanical properties and constitutive behavior of the constituent materials. In this work, an experimental investigation has been performed on the effects of moisture adsorption on the stress-strain behavior of polycarbonate materials used in electronic packaging. Uniaxial test specimens were exposed in a controlled temperature and humidity chamber to combined hygrothermal exposures at 60 C and 90% RH, 60 C and 50% RH, and 40 C and 50% 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 = 20 C, 40 C, and 60 C). It was found that moisture exposure strongly affected the mechanical properties of the tested polycarbonate, especially ultimate strain limit. Reversibility tests were also conducted to evaluate whether the degradations in the mechanical properties were recoverable. Upon fully redrying, the material was found to recover most of its original mechanical properties. In addition, optical microscopy was utilized to examine the fracture surfaces of the failed specimens, and observe the influence of moisture exposure.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"56 1","pages":"355-364"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81525125","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}
Pub Date : 2014-05-27DOI: 10.1109/ITHERM.2014.6892409
N. Bajad, H. Kulkarni, S. Dhole, S. Thakur, S. Tonapi
The effect of solder joint size on wafer level chip scale package reliability has been studied through simulation. A two dimensional finite element model with different solder diameter (250μm, 300μm, 350μm) was studied under accelerated thermal cycling. The failure of the solder joints under thermal fatigue loading is influenced by the solder joint size. Finite element modelling can be used to study the design space and predict failure. In this paper, successive initiation method with energy partitioning approach is used for crack initiation and propagation in the solder joint. The number of thermal cycles to failure are calculated and compared for 250μm, 300μm, 350μm solder diameter.
{"title":"Effect of solder joint size on fatigue life of WL-CSP under accelerated thermal cycling using FEM","authors":"N. Bajad, H. Kulkarni, S. Dhole, S. Thakur, S. Tonapi","doi":"10.1109/ITHERM.2014.6892409","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892409","url":null,"abstract":"The effect of solder joint size on wafer level chip scale package reliability has been studied through simulation. A two dimensional finite element model with different solder diameter (250μm, 300μm, 350μm) was studied under accelerated thermal cycling. The failure of the solder joints under thermal fatigue loading is influenced by the solder joint size. Finite element modelling can be used to study the design space and predict failure. In this paper, successive initiation method with energy partitioning approach is used for crack initiation and propagation in the solder joint. The number of thermal cycles to failure are calculated and compared for 250μm, 300μm, 350μm solder diameter.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"44 1","pages":"1145-1153"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78103578","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}
Pub Date : 2014-05-27DOI: 10.1109/ITHERM.2014.6892306
J. Thalakkottor, K. Mohseni
Fluid flow in a microchannel is primarily laminar due to viscous forces dominating over body or inertia forces. Hence fluid circulation in a droplet greatly enhances heat transfer. As a result, slip at a wall-fluid interface could have a two fold affect on heat transfer in droplet based thermal systems; the first is a direct result of thermal slip at the fluid-wall interface, the second is due to hydrodynamic slip at the interface which leads to reduction of internal circulation and in turn reduction in heat transfer. In this paper molecular dynamic simulations are used to look at the effects of thermal and hydrodynamic slip separately and then to investigate the cumulative effect of them on heat transfer in moving droplets in a microchannel. The affect of hydrodynamic slip in an isothermal channel is studied and it is observed that circulation is inversely dependent on slip length. A simple model is established that captures this effect and it also shows that the effect of slip on circulation only becomes important when the length scale of the problem is comparable to the order of slip length.
{"title":"Effect of hydrodynamic and thermal slip on droplet based thermal management systems","authors":"J. Thalakkottor, K. Mohseni","doi":"10.1109/ITHERM.2014.6892306","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892306","url":null,"abstract":"Fluid flow in a microchannel is primarily laminar due to viscous forces dominating over body or inertia forces. Hence fluid circulation in a droplet greatly enhances heat transfer. As a result, slip at a wall-fluid interface could have a two fold affect on heat transfer in droplet based thermal systems; the first is a direct result of thermal slip at the fluid-wall interface, the second is due to hydrodynamic slip at the interface which leads to reduction of internal circulation and in turn reduction in heat transfer. In this paper molecular dynamic simulations are used to look at the effects of thermal and hydrodynamic slip separately and then to investigate the cumulative effect of them on heat transfer in moving droplets in a microchannel. The affect of hydrodynamic slip in an isothermal channel is studied and it is observed that circulation is inversely dependent on slip length. A simple model is established that captures this effect and it also shows that the effect of slip on circulation only becomes important when the length scale of the problem is comparable to the order of slip length.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"60 1","pages":"381-387"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78355845","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}
Pub Date : 2014-05-27DOI: 10.1109/ITHERM.2014.6892315
C. Kruse, T. Anderson, Chris Wilson, C. Zuhlke, D. Alexander, G. Gogos, S. Ndao
In this paper, we present the experimental investigation of pool boiling heat transfer on multiscale (micro/nano) functionalized metallic surfaces. The multiscale structures were fabricated via a femtosecond laser surface process (FLSP) technique which forms mound-like microstructures covered by layers of nanoparticles. Using a pool boiling experimental setup with deionized water as the working fluid, both the heat transfer coefficient and critical heat flux were investigated. The polished reference sample was found to have a critical heat flux of 91 W/cm2 at 40 °C of superheat and a maximum heat transfer coefficient of 23,000 W/m2-K. The processed sample was found to have a critical heat flux of 122 W/cm2 at 18 °C superheat and a maximum heat transfer coefficient of 67,400 W/m2-K. Flow visualization revealed nucleate boiling to be the main two-phase heat transfer mechanism. The overall heat transfer performance of the metallic multiscale structured surface has been attributed to both augmented heat transfer surface area and enhanced nucleate boiling regime. On the other hand, increase in the critical heat flux can be attributed to the superhydrophilic nature of the laser processed surface and the presence of nanoparticle layers.
{"title":"Enhanced pool-boiling heat transfer and critical heat flux using femtosecond laser surface processing","authors":"C. Kruse, T. Anderson, Chris Wilson, C. Zuhlke, D. Alexander, G. Gogos, S. Ndao","doi":"10.1109/ITHERM.2014.6892315","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892315","url":null,"abstract":"In this paper, we present the experimental investigation of pool boiling heat transfer on multiscale (micro/nano) functionalized metallic surfaces. The multiscale structures were fabricated via a femtosecond laser surface process (FLSP) technique which forms mound-like microstructures covered by layers of nanoparticles. Using a pool boiling experimental setup with deionized water as the working fluid, both the heat transfer coefficient and critical heat flux were investigated. The polished reference sample was found to have a critical heat flux of 91 W/cm2 at 40 °C of superheat and a maximum heat transfer coefficient of 23,000 W/m2-K. The processed sample was found to have a critical heat flux of 122 W/cm2 at 18 °C superheat and a maximum heat transfer coefficient of 67,400 W/m2-K. Flow visualization revealed nucleate boiling to be the main two-phase heat transfer mechanism. The overall heat transfer performance of the metallic multiscale structured surface has been attributed to both augmented heat transfer surface area and enhanced nucleate boiling regime. On the other hand, increase in the critical heat flux can be attributed to the superhydrophilic nature of the laser processed surface and the presence of nanoparticle layers.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"5 1","pages":"444-451"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80553367","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}
Pub Date : 2014-05-27DOI: 10.1109/ITHERM.2014.6892260
Minmin Hou, Chi-Chun Pan, M. Asheghi, D. Senesky
This paper reports the steady-state and transient temperature response of AlGaN/GaN high electron mobility transistor (HEMT) based structures. In this study, three localized heating schemes, namely, continuous self-heating, pulsed self-heating and heating with on-chip heaters are studied for sensor applications that require controlled heating profiles. Two scenarios were considered for the GaN sensor structure: 1) the silicon substrate under the AlGaN/GaN sensor is not removed, and 2) the silicon substrate is removed to form a suspended AlGaN/GaN diaphragm on which the sensor is located. The three heating schemes are analyzed by finite element thermal analysis, evaluated and compared. In addition, general guidelines for designing localized heating architectures for AlGaN/GaN HEMT based sensors are provided.
{"title":"Finite element thermal analysis of localized heating in AlGaN/GaN HEMT based sensors","authors":"Minmin Hou, Chi-Chun Pan, M. Asheghi, D. Senesky","doi":"10.1109/ITHERM.2014.6892260","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892260","url":null,"abstract":"This paper reports the steady-state and transient temperature response of AlGaN/GaN high electron mobility transistor (HEMT) based structures. In this study, three localized heating schemes, namely, continuous self-heating, pulsed self-heating and heating with on-chip heaters are studied for sensor applications that require controlled heating profiles. Two scenarios were considered for the GaN sensor structure: 1) the silicon substrate under the AlGaN/GaN sensor is not removed, and 2) the silicon substrate is removed to form a suspended AlGaN/GaN diaphragm on which the sensor is located. The three heating schemes are analyzed by finite element thermal analysis, evaluated and compared. In addition, general guidelines for designing localized heating architectures for AlGaN/GaN HEMT based sensors are provided.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"19 1","pages":"25-30"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86186425","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}
Pub Date : 2014-05-27DOI: 10.1109/ITHERM.2014.6892440
A. Emplit, I. Huynen
Multifunctional and multistructured materials are currently developed for high power electronics in transportation and aerospace sectors requiring size and weight reduction. In this work, we investigate laser-machined micro patterns of CNT brushes as an alternative to metallic structures for driving simultaneously EM and heat propagation. The thermal response of the CNT array is observed to be sensitive to the microstructured pattern etched in the CNT brush, and to the mechanical stress induced by an incident air flux. Depending on the induced displacement of nanotubes, a temperature change up to 5°C is measured. The movement of the CNT within the array is correlated to the mechanical stress imposed by the incident air flux. The correlation between thermal fluctuation and air flux is indeed assessed through the proper combination of SEM and interferometry imaging with thermography.
{"title":"Carbon nanotube arrays for coupled electromagnetic and thermal management in high power electronics: Influence of microstructuration and stress investigated by IR thermography","authors":"A. Emplit, I. Huynen","doi":"10.1109/ITHERM.2014.6892440","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892440","url":null,"abstract":"Multifunctional and multistructured materials are currently developed for high power electronics in transportation and aerospace sectors requiring size and weight reduction. In this work, we investigate laser-machined micro patterns of CNT brushes as an alternative to metallic structures for driving simultaneously EM and heat propagation. The thermal response of the CNT array is observed to be sensitive to the microstructured pattern etched in the CNT brush, and to the mechanical stress induced by an incident air flux. Depending on the induced displacement of nanotubes, a temperature change up to 5°C is measured. The movement of the CNT within the array is correlated to the mechanical stress imposed by the incident air flux. The correlation between thermal fluctuation and air flux is indeed assessed through the proper combination of SEM and interferometry imaging with thermography.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"2 1","pages":"1379-1384"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75343893","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}
Pub Date : 2014-05-27DOI: 10.1109/ITHERM.2014.6892369
R. Weigand, A. Fleischer
Solid-liquid phase change materials (PCMs) can be used as a transient thermal management technique due to their ability to store significant amounts of heat through the solid liquid phase change. It is common to improve the low thermal conductivity of PCMs by adding nanoparticles, however, this addition changes some of the physical properties of the material, including viscosity, possibly hindering convection currents seen in the liquid state. The dynamic viscosity of nano-enhanced materials is examined in this paper as a function of shear rate and temperature. The materials used are paraffin wax enhanced with herringbone style graphite nanofibers (HGNFs) in 0.1% and 0.5% volume fractions with and without oleic acid. The nano-enhanced materials are found to be Newtonian in nature and to decrease in viscosity as temperature increases.
{"title":"The influence of nanoparticle loading and surfactant on the viscosity of nanoenhanced energy storage materials","authors":"R. Weigand, A. Fleischer","doi":"10.1109/ITHERM.2014.6892369","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892369","url":null,"abstract":"Solid-liquid phase change materials (PCMs) can be used as a transient thermal management technique due to their ability to store significant amounts of heat through the solid liquid phase change. It is common to improve the low thermal conductivity of PCMs by adding nanoparticles, however, this addition changes some of the physical properties of the material, including viscosity, possibly hindering convection currents seen in the liquid state. The dynamic viscosity of nano-enhanced materials is examined in this paper as a function of shear rate and temperature. The materials used are paraffin wax enhanced with herringbone style graphite nanofibers (HGNFs) in 0.1% and 0.5% volume fractions with and without oleic acid. The nano-enhanced materials are found to be Newtonian in nature and to decrease in viscosity as temperature increases.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"86 1 1","pages":"846-850"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75207519","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}
Pub Date : 2014-05-27DOI: 10.1109/ITHERM.2014.6892356
Thomas J. Dusseault, Julie Gires, M. Barako, Y. Won, D. Agonafer, M. Asheghi, J. Santiago, K. Goodson
We report the fabrication and fluid flow characterization of a class of open-cell copper foams known as copper inverse opals (CIOs). This material has finely controlled structure at the pore level, which may enable its use in microscale heat exchangers for microelectronics cooling. We fabricated CIOs by electrodepositing copper around a sacrificial template of packed polystyrene microspheres. We then removed the CIOs from their substrates and used electroetching to vary the pore structure and porosity. We characterized the geometry of the samples at various stages of fabrication with visual inspection and image analysis of scanning electron micrographs. We characterized the permeability with a through-plane flow rig and developed computational models for fluid flow in ideal face-centered cubic and hexagonally close-packed unit cells. Here we report the simulated and experimentally measured values of permeability. We also report experimental challenges that arise from the microscale dimensions of the samples.
{"title":"Inverse opals for fluid delivery in electronics cooling systems","authors":"Thomas J. Dusseault, Julie Gires, M. Barako, Y. Won, D. Agonafer, M. Asheghi, J. Santiago, K. Goodson","doi":"10.1109/ITHERM.2014.6892356","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892356","url":null,"abstract":"We report the fabrication and fluid flow characterization of a class of open-cell copper foams known as copper inverse opals (CIOs). This material has finely controlled structure at the pore level, which may enable its use in microscale heat exchangers for microelectronics cooling. We fabricated CIOs by electrodepositing copper around a sacrificial template of packed polystyrene microspheres. We then removed the CIOs from their substrates and used electroetching to vary the pore structure and porosity. We characterized the geometry of the samples at various stages of fabrication with visual inspection and image analysis of scanning electron micrographs. We characterized the permeability with a through-plane flow rig and developed computational models for fluid flow in ideal face-centered cubic and hexagonally close-packed unit cells. Here we report the simulated and experimentally measured values of permeability. We also report experimental challenges that arise from the microscale dimensions of the samples.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"106 1","pages":"750-755"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76078091","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}
Pub Date : 2014-05-27DOI: 10.1109/ITHERM.2014.6892374
M. Ikhlaq, Omidreza Ghaffari, M. Arik
Synthetic jets are being investigated over the last four decades. Researchers have been interested in its unique applications for a wide range of flow control to thermal management of electronics applications. Synthetic jets are made up of actuators such as piezoelectric, magnetic, or linear piston technology etc. In this study, we performed an experimental and numerical investigation of a piezoelectric disk deflection over a range of frequencies in order to understand the performance for low and high frequency synthetic jets. First, we performed a numerical analysis of a piezoelectric based synthetic jet and, validated computational result with experimental findings. Numerical models are performed by using commercial finite element software. To understand the size effect on the operating frequency, three jets with different sizes are manufactured and examined. Two different low frequency synthetic jets manufactured in our laboratory and a commercially available high frequency jet are included in the present study. Heat transfer performance is given as an enhancement over natural convection heat transfer. The heat transfer enhancement factor of each of these jets with respect to natural convection is measured over a 25.4×25.4 (mm) vertical heater. Finally, power consumption of the low and high frequency synthetic jets were measured and compared. It is found that disk deflection and operating frequency are directly related to heat transfer enhancement factor, if the Helmholtz frequency of a cavity has no effect on the performance of a jet. The Helmholtz frequency of each jet was calculated to ensure that it has no effect on the synthetic jet, but we found that the commercial synthetic jet took partial advantage of Helmholtz phenomena to enhance the performances at high frequencies.
{"title":"Effect of actuator deflection on heat transfer for low and high frequency synthetic jets","authors":"M. Ikhlaq, Omidreza Ghaffari, M. Arik","doi":"10.1109/ITHERM.2014.6892374","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892374","url":null,"abstract":"Synthetic jets are being investigated over the last four decades. Researchers have been interested in its unique applications for a wide range of flow control to thermal management of electronics applications. Synthetic jets are made up of actuators such as piezoelectric, magnetic, or linear piston technology etc. In this study, we performed an experimental and numerical investigation of a piezoelectric disk deflection over a range of frequencies in order to understand the performance for low and high frequency synthetic jets. First, we performed a numerical analysis of a piezoelectric based synthetic jet and, validated computational result with experimental findings. Numerical models are performed by using commercial finite element software. To understand the size effect on the operating frequency, three jets with different sizes are manufactured and examined. Two different low frequency synthetic jets manufactured in our laboratory and a commercially available high frequency jet are included in the present study. Heat transfer performance is given as an enhancement over natural convection heat transfer. The heat transfer enhancement factor of each of these jets with respect to natural convection is measured over a 25.4×25.4 (mm) vertical heater. Finally, power consumption of the low and high frequency synthetic jets were measured and compared. It is found that disk deflection and operating frequency are directly related to heat transfer enhancement factor, if the Helmholtz frequency of a cavity has no effect on the performance of a jet. The Helmholtz frequency of each jet was calculated to ensure that it has no effect on the synthetic jet, but we found that the commercial synthetic jet took partial advantage of Helmholtz phenomena to enhance the performances at high frequencies.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"45 1","pages":"882-888"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75981252","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}
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