Pub Date : 2017-05-01DOI: 10.1109/ITHERM.2017.7992523
L. Collin, J. Colonna, P. Coudrain, M. Shirazy, S. Chéramy, A. Souifi, L. Fréchette
This work proposes an experimental microchannel solution to cool microelectronic chips with hot spots, using a non-intrusive technique. In microelectronics, approaches such as die thinning induces acute stress on cooling because it increases the hotspot phenomena and reduces chip bulk thickness aimed for microchannels. In mobile devices, the heat must be removed using limited pumping power and cooling space. Microchannels etched in the backside of the chip, usually considered as an efficient cooling solution, are impracticable on highly thinned chips. This work experimentally investigates the cooling performance of a non-invasive and hot spot aware microchannel die that is in direct fluidic contact with the backside of the chip. It also proposes a confinement-wise metric. A thermal resistance of 2.8 °C/W is achieved at heat flux of 1185 W/cm2 per heat source, for a total dissipated power of 20 W and a maximum allowed temperature rise of 55 °C. Such performance is obtained with only 19.2 kPa of pressure drop and 9.4 ml/min of flow rate, making a hydraulic power of only 3 mW, representing a coefficient of performance of 6500. Therefore, backside cooling appears as a compact and low consumption solution for highly confined heat on chips for mobile applications.
{"title":"Hot spot aware microchannel cooling add-on for microelectronic chips in mobile devices","authors":"L. Collin, J. Colonna, P. Coudrain, M. Shirazy, S. Chéramy, A. Souifi, L. Fréchette","doi":"10.1109/ITHERM.2017.7992523","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992523","url":null,"abstract":"This work proposes an experimental microchannel solution to cool microelectronic chips with hot spots, using a non-intrusive technique. In microelectronics, approaches such as die thinning induces acute stress on cooling because it increases the hotspot phenomena and reduces chip bulk thickness aimed for microchannels. In mobile devices, the heat must be removed using limited pumping power and cooling space. Microchannels etched in the backside of the chip, usually considered as an efficient cooling solution, are impracticable on highly thinned chips. This work experimentally investigates the cooling performance of a non-invasive and hot spot aware microchannel die that is in direct fluidic contact with the backside of the chip. It also proposes a confinement-wise metric. A thermal resistance of 2.8 °C/W is achieved at heat flux of 1185 W/cm2 per heat source, for a total dissipated power of 20 W and a maximum allowed temperature rise of 55 °C. Such performance is obtained with only 19.2 kPa of pressure drop and 9.4 ml/min of flow rate, making a hydraulic power of only 3 mW, representing a coefficient of performance of 6500. Therefore, backside cooling appears as a compact and low consumption solution for highly confined heat on chips for mobile applications.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128564400","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 : 2017-05-01DOI: 10.1109/ITHERM.2017.7992598
J. Davis, K. Mills, M. Lamvik, Eric Solano, G. Bobashev, C. Perkins
Meeting the longevity requirements of solid-state lighting (SSL) devices places extreme demands on the materials and designs that are used in SSL luminaires. Therefore, understanding the aging characteristics of lens, reflectors, and other materials is essential to projecting the long-term performance of LED-based lighting systems. Overlooking these factors at either the design or product specification stage can result in premature failure of the device due to poor luminous flux maintenance and/or excessive chromaticity shifts. This paper describes a methodology for performing accelerated stress testing (AST) on materials intended for use in SSL luminaires. This test methodology, which consists of elevated temperature and humidity conditions, produces accelerated aging data that can be correlated to expected performance under normal luminaire operating conditions. The correlations can then be leveraged to produce models of the changes in the optical properties of key materials including transmittance versus wavelength of lenses and reflectance versus wavelength for housings and other reflectors. This information has been collected into a lumen maintenance decision support tool (LM-DST) and together with user supplied inputs (e.g., expected operation conditions) can provide guidance on lifetime expectations of SSL luminaires. This approach has been applied to a variety of materials commonly found in SSL luminaires including acrylics, polycarbonates, and silicones used for lenses and paints, coatings, films, and composites used for reflectors.
{"title":"Modeling the impact of thermal effects on luminous flux maintenance for SSL luminaires","authors":"J. Davis, K. Mills, M. Lamvik, Eric Solano, G. Bobashev, C. Perkins","doi":"10.1109/ITHERM.2017.7992598","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992598","url":null,"abstract":"Meeting the longevity requirements of solid-state lighting (SSL) devices places extreme demands on the materials and designs that are used in SSL luminaires. Therefore, understanding the aging characteristics of lens, reflectors, and other materials is essential to projecting the long-term performance of LED-based lighting systems. Overlooking these factors at either the design or product specification stage can result in premature failure of the device due to poor luminous flux maintenance and/or excessive chromaticity shifts. This paper describes a methodology for performing accelerated stress testing (AST) on materials intended for use in SSL luminaires. This test methodology, which consists of elevated temperature and humidity conditions, produces accelerated aging data that can be correlated to expected performance under normal luminaire operating conditions. The correlations can then be leveraged to produce models of the changes in the optical properties of key materials including transmittance versus wavelength of lenses and reflectance versus wavelength for housings and other reflectors. This information has been collected into a lumen maintenance decision support tool (LM-DST) and together with user supplied inputs (e.g., expected operation conditions) can provide guidance on lifetime expectations of SSL luminaires. This approach has been applied to a variety of materials commonly found in SSL luminaires including acrylics, polycarbonates, and silicones used for lenses and paints, coatings, films, and composites used for reflectors.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"119 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116685009","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 : 2017-05-01DOI: 10.1109/ITHERM.2017.7992632
D. Squiller, I. Movius, M. Ohadi, P. McCluskey
Embedded cooling systems have enabled higher volumetric heat removal rates at the chip and package levels, permitting advanced power electronic devices to operate closer to their inherent electrical limits. By embedding microchannels directly into the chip or substrate, higher local and global heat fluxes can be reached as the heat removal takes place in close proximity to the source. As this emerging technology finds its way into aerospace, military and commercial applications, reliability will be of utmost importance. This paper will address the fundamental reliability concerns and degradation mechanisms associated with embedded cooling systems, specifically those pertaining to particle erosion. This mechanism has the potential to hinder the active cooling of the electronics by altering the microfluidic geometries and by subsequently restricting or blocking fluid paths due to the increased particle concentration in the fluid. A slurry erosion jet-impingement testing apparatus was constructed to investigate how factors such as particle size, particle concentration, impingement angle and velocity affect the erosion of single crystal silicon and silicon carbide. The test setup is capable of handling velocities up to 60 m/s, particle sizes ranging from the nanometer scale to tens of micrometers, impingement angles from 10 to 90 degrees, and is chemically compatible with a variety of working fluids including deionized water and propylene and ethylene glycols. The main goal of this research is to identify threshold velocities and threshold particle sizes under which no erosion will occur. Additionally, a procedure to develop a new model has been proposed which considers factors that current particle erosion models do not consider such as particle concentration and fluid viscosity.
{"title":"Degradation mechanisms of embedded cooling systems for high heat flux power electronics: Particle erosion of silicon and silicon carbide","authors":"D. Squiller, I. Movius, M. Ohadi, P. McCluskey","doi":"10.1109/ITHERM.2017.7992632","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992632","url":null,"abstract":"Embedded cooling systems have enabled higher volumetric heat removal rates at the chip and package levels, permitting advanced power electronic devices to operate closer to their inherent electrical limits. By embedding microchannels directly into the chip or substrate, higher local and global heat fluxes can be reached as the heat removal takes place in close proximity to the source. As this emerging technology finds its way into aerospace, military and commercial applications, reliability will be of utmost importance. This paper will address the fundamental reliability concerns and degradation mechanisms associated with embedded cooling systems, specifically those pertaining to particle erosion. This mechanism has the potential to hinder the active cooling of the electronics by altering the microfluidic geometries and by subsequently restricting or blocking fluid paths due to the increased particle concentration in the fluid. A slurry erosion jet-impingement testing apparatus was constructed to investigate how factors such as particle size, particle concentration, impingement angle and velocity affect the erosion of single crystal silicon and silicon carbide. The test setup is capable of handling velocities up to 60 m/s, particle sizes ranging from the nanometer scale to tens of micrometers, impingement angles from 10 to 90 degrees, and is chemically compatible with a variety of working fluids including deionized water and propylene and ethylene glycols. The main goal of this research is to identify threshold velocities and threshold particle sizes under which no erosion will occur. Additionally, a procedure to develop a new model has been proposed which considers factors that current particle erosion models do not consider such as particle concentration and fluid viscosity.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"252 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115623956","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 : 2017-05-01DOI: 10.1109/ITHERM.2017.7992491
P. R. d'Egmont, C. Naveira-Cotta, R. Dias, C. Tostado, F. P. Duda, K. Chen
Applications of high-power insulated gate bipolar transistor (IGBT) modules include railway traction, motor drives, and hybrid electric vehicles. The reliability of these semiconductor devices is tightly linked to the operating junction temperatures of IGBT and diode chips present in them. Since these temperatures are very difficult to measure, accurate models and simulation tools are required to compute the instantaneous temperature of the devices under different load conditions. In this paper, we describe a transient 3D heat transfer numerical model of an IGBT power device with many layers of varying cross-sectional areas, distinct materials, and heat sources. Two cases were evaluated according to the total power dissipation considered. In the first case, a non-switching constant conduction scenario was considered in which a power dissipation of 6.15 W based on experiments was adopted and the calculated results were validated against experimental data obtained via infrared thermography, and excellent agreement between the results was observed. For the second case, IGBT switching — along with power losses due to the gate-closing and gate-opening transitions between conducting and non-conducting states — was taken into consideration. For this case, a higher power of 27.23 W was considered to represent the average power dissipation associated with a typical real-life application of the IGBT unit at a switching at frequency of 1 kHz. For this case, the power dissipation on the IGBT chip was obtained from an electrical simulation and used in the heat transfer problem as a strongly time-dependent heat source. The temperature distributions for both cases were then critically compared.
{"title":"Experimental-theoretical thermal and electrical analyses of insulated gate bipolar transistors (IGBT) power module","authors":"P. R. d'Egmont, C. Naveira-Cotta, R. Dias, C. Tostado, F. P. Duda, K. Chen","doi":"10.1109/ITHERM.2017.7992491","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992491","url":null,"abstract":"Applications of high-power insulated gate bipolar transistor (IGBT) modules include railway traction, motor drives, and hybrid electric vehicles. The reliability of these semiconductor devices is tightly linked to the operating junction temperatures of IGBT and diode chips present in them. Since these temperatures are very difficult to measure, accurate models and simulation tools are required to compute the instantaneous temperature of the devices under different load conditions. In this paper, we describe a transient 3D heat transfer numerical model of an IGBT power device with many layers of varying cross-sectional areas, distinct materials, and heat sources. Two cases were evaluated according to the total power dissipation considered. In the first case, a non-switching constant conduction scenario was considered in which a power dissipation of 6.15 W based on experiments was adopted and the calculated results were validated against experimental data obtained via infrared thermography, and excellent agreement between the results was observed. For the second case, IGBT switching — along with power losses due to the gate-closing and gate-opening transitions between conducting and non-conducting states — was taken into consideration. For this case, a higher power of 27.23 W was considered to represent the average power dissipation associated with a typical real-life application of the IGBT unit at a switching at frequency of 1 kHz. For this case, the power dissipation on the IGBT chip was obtained from an electrical simulation and used in the heat transfer problem as a strongly time-dependent heat source. The temperature distributions for both cases were then critically compared.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127536178","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 : 2017-05-01DOI: 10.1109/ITHERM.2017.7992604
J. Davis, A. Smith, Terry Clark, K. Mills, C. Perkins
Two-channel tunable white lighting (TWL) systems represent the next wave of solid-state lighting (SSL) systems and promise flexibility in light environment while maintaining the high reliability and luminous efficacy expected with SSL devices. TWL systems utilize LED assemblies consisting of two different LED spectra (i.e., often a warm white assembly and a cool white assembly) that are integrated into modules. While these systems provide the ability to adjust the lighting spectrum to match the physiology needs of the task at hand, they also are a potentially more complex lighting system from a performance and reliability perspective. We report an initial study on the reliability performance of such lighting systems including an examination of the lumen maintenance and chromaticity stability of warm white and cool white LED assemblies and the multi-channel driver that provides power to the assemblies. Accelerated stress tests including operational bake tests conducted at 75°C and 95°C were used to age the LED modules, while more aggressive temperature and humidity tests were used for the drivers in this study. Small differences in the performance between the two LED assemblies were found and can be attributed to the different phosphor chemistries. The lumen maintenances of both LED assemblies were excellent. The warm white LED assemblies were found to shift slightly in the green color direction over time while the cool white LED assemblies shifted slightly in the yellow color direction. The net result of these chromaticity shifts is a small, barely perceptible reduction in the tuning range after 6,000 hours of exposure to an accelerating elevated temperature of 75°C.
{"title":"Lifetime predictions for dimmable two-channel tunable white luminaires","authors":"J. Davis, A. Smith, Terry Clark, K. Mills, C. Perkins","doi":"10.1109/ITHERM.2017.7992604","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992604","url":null,"abstract":"Two-channel tunable white lighting (TWL) systems represent the next wave of solid-state lighting (SSL) systems and promise flexibility in light environment while maintaining the high reliability and luminous efficacy expected with SSL devices. TWL systems utilize LED assemblies consisting of two different LED spectra (i.e., often a warm white assembly and a cool white assembly) that are integrated into modules. While these systems provide the ability to adjust the lighting spectrum to match the physiology needs of the task at hand, they also are a potentially more complex lighting system from a performance and reliability perspective. We report an initial study on the reliability performance of such lighting systems including an examination of the lumen maintenance and chromaticity stability of warm white and cool white LED assemblies and the multi-channel driver that provides power to the assemblies. Accelerated stress tests including operational bake tests conducted at 75°C and 95°C were used to age the LED modules, while more aggressive temperature and humidity tests were used for the drivers in this study. Small differences in the performance between the two LED assemblies were found and can be attributed to the different phosphor chemistries. The lumen maintenances of both LED assemblies were excellent. The warm white LED assemblies were found to shift slightly in the green color direction over time while the cool white LED assemblies shifted slightly in the yellow color direction. The net result of these chromaticity shifts is a small, barely perceptible reduction in the tuning range after 6,000 hours of exposure to an accelerating elevated temperature of 75°C.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125685136","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 : 2017-05-01DOI: 10.1109/ITHERM.2017.7991851
Joel D. Chapman, P. Kottke, A. Fedorov
For a number of demanding applications, the performance of electronic devices is hampered by the inability to remove generated heat at a sufficient rate to increase transistor density or operating frequency without exceeding thermal limits. Two-phase cooling, in particular thin film evaporation, exploits the latent heat of phase change to provide an effective means for high heat flux dissipation while keeping device junction temperatures nearly constant over a range of heating loads. Delivering a coolant at a precise location on the heated surface and forming a thin film needed for efficient evaporation from a free liquid surface are key requirements for using evaporative cooling for thermal management of spatially non-uniform heat fluxes. The electrospray process enables production and delivery of micro to nanoscale electrically charged droplets towards the heated surface to produce the liquid films, and therefore it has a potential to be a promising method for evaporative cooling. A relatively low power consumption needed to generate the electrospray provides further benefits in terms of energy efficiency as compared to conventional mechanically pumped liquid spray approaches. We report on experimental observations of electrosprayed droplet impingement, coalescence, and film formation on a heated ITO (Indium Tin Oxide) surface acting as an optically transparent heating element, focusing primarily on visualization and mapping of the impacting spray-jet behavior and its impact on the resulting film thickness and shape, which directly affect an expected performance of evaporative cooling.
{"title":"Towards using nanoelectrospray for evaporative heat transfer enhancement","authors":"Joel D. Chapman, P. Kottke, A. Fedorov","doi":"10.1109/ITHERM.2017.7991851","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7991851","url":null,"abstract":"For a number of demanding applications, the performance of electronic devices is hampered by the inability to remove generated heat at a sufficient rate to increase transistor density or operating frequency without exceeding thermal limits. Two-phase cooling, in particular thin film evaporation, exploits the latent heat of phase change to provide an effective means for high heat flux dissipation while keeping device junction temperatures nearly constant over a range of heating loads. Delivering a coolant at a precise location on the heated surface and forming a thin film needed for efficient evaporation from a free liquid surface are key requirements for using evaporative cooling for thermal management of spatially non-uniform heat fluxes. The electrospray process enables production and delivery of micro to nanoscale electrically charged droplets towards the heated surface to produce the liquid films, and therefore it has a potential to be a promising method for evaporative cooling. A relatively low power consumption needed to generate the electrospray provides further benefits in terms of energy efficiency as compared to conventional mechanically pumped liquid spray approaches. We report on experimental observations of electrosprayed droplet impingement, coalescence, and film formation on a heated ITO (Indium Tin Oxide) surface acting as an optically transparent heating element, focusing primarily on visualization and mapping of the impacting spray-jet behavior and its impact on the resulting film thickness and shape, which directly affect an expected performance of evaporative cooling.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128083561","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 : 2017-05-01DOI: 10.1109/ITHERM.2017.7992493
A. Sarode, Z. Ahmed, Pratik Basarkar, A. Bhargav, Debjyoti Baneijee
Very high thermal conductivity of carbon nanotube (CNT) makes it an obvious choice in electronic cooling applications. But at the nanoscale, these CNTs face a limitation due to the interfacial thermal resistance commonly known as Kapitza resistance, prevailing between the carbon nanotube and coolant molecules at the solid-liquid boundary. Vibrational mismatch at the interface gives rise to the Kapitza resistance which plays a dominating role in the heat transfer process. Current work puts an effort to investigate the impact of CNT diameter on the interfacial resistance between nanotube and water molecules through molecular dynamics. Molecular dynamics simulations have been performed using armchair single walled CNTs. Beginning with the initial configuration, the system of CNT and water molecules is equilibrated at 300 K and 1 atm. The temperature of the CNT is raised to 700 K and then allowed to relax in a bath of water molecules. The time constant of the CNT temperature response is determined based on the lumped capacitance analysis which is then used to compute the interfacial resistance. Present study illustrates that the interfacial thermal resistance is increases as the diameter of the single walled carbon nanotube increases. Therefore, in electronic cooling applications, CNT of smaller diameters should be preferred owing to its lower values of interfacial thermal resistance.
{"title":"Role of carbon nanotube on the interfacial thermal resistance: A molecular dynamics approach","authors":"A. Sarode, Z. Ahmed, Pratik Basarkar, A. Bhargav, Debjyoti Baneijee","doi":"10.1109/ITHERM.2017.7992493","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992493","url":null,"abstract":"Very high thermal conductivity of carbon nanotube (CNT) makes it an obvious choice in electronic cooling applications. But at the nanoscale, these CNTs face a limitation due to the interfacial thermal resistance commonly known as Kapitza resistance, prevailing between the carbon nanotube and coolant molecules at the solid-liquid boundary. Vibrational mismatch at the interface gives rise to the Kapitza resistance which plays a dominating role in the heat transfer process. Current work puts an effort to investigate the impact of CNT diameter on the interfacial resistance between nanotube and water molecules through molecular dynamics. Molecular dynamics simulations have been performed using armchair single walled CNTs. Beginning with the initial configuration, the system of CNT and water molecules is equilibrated at 300 K and 1 atm. The temperature of the CNT is raised to 700 K and then allowed to relax in a bath of water molecules. The time constant of the CNT temperature response is determined based on the lumped capacitance analysis which is then used to compute the interfacial resistance. Present study illustrates that the interfacial thermal resistance is increases as the diameter of the single walled carbon nanotube increases. Therefore, in electronic cooling applications, CNT of smaller diameters should be preferred owing to its lower values of interfacial thermal resistance.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127272012","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 : 2017-05-01DOI: 10.1109/ITHERM.2017.7992601
Linjuan Huang, Yu-Chou Shih, F. Shi
As a novel replacement of conventional light sources, LED filament bulb has gained popularity recently due to its long lifetime, low cost and high energy efficiency. However, the bottleneck in LED filament development is thermal management of the whole bulb and consequential degradation of light output performance. The potential cooling strategies include passive cooling and active cooling. Compared with passive cooling methods, active cooling ones are more costly, space-consuming, heavier and do not apply to the case of filament bulb. Thus, passive cooling such as thermal conductive phosphor-silicon composite and thermal radiation coating wrapped around the filaments can be adopted to boost the thermal conduction and radiation into the environment. Notice that the temperature distribution within phosphor layer is non-uniform, thermal radiation coating can make phosphor temperature more uniform as well as reduce the risk of thermal quenching and hotspot. Here, the effect of our self-developed thermal radiation coatings with different emissivity are compared and investigated. What's more, open slots or holes on the bulb can be considered to enhance the thermal convection of the filament. According to our simulation, the junction temperature will decrease with filament thickness. This is because the outer surface of filament for both thermal convection and radiation is increased, which stimulates the total heat transfer. With this optimized passive cooling strategy, thermal issue of LED filament bulb can be mitigated largely and cost-performance ratio is at a relatively low level.
{"title":"Cooling strategy for LED filament bulb utilizing thermal radiation cooling and open slots enhancing thermal convection","authors":"Linjuan Huang, Yu-Chou Shih, F. Shi","doi":"10.1109/ITHERM.2017.7992601","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992601","url":null,"abstract":"As a novel replacement of conventional light sources, LED filament bulb has gained popularity recently due to its long lifetime, low cost and high energy efficiency. However, the bottleneck in LED filament development is thermal management of the whole bulb and consequential degradation of light output performance. The potential cooling strategies include passive cooling and active cooling. Compared with passive cooling methods, active cooling ones are more costly, space-consuming, heavier and do not apply to the case of filament bulb. Thus, passive cooling such as thermal conductive phosphor-silicon composite and thermal radiation coating wrapped around the filaments can be adopted to boost the thermal conduction and radiation into the environment. Notice that the temperature distribution within phosphor layer is non-uniform, thermal radiation coating can make phosphor temperature more uniform as well as reduce the risk of thermal quenching and hotspot. Here, the effect of our self-developed thermal radiation coatings with different emissivity are compared and investigated. What's more, open slots or holes on the bulb can be considered to enhance the thermal convection of the filament. According to our simulation, the junction temperature will decrease with filament thickness. This is because the outer surface of filament for both thermal convection and radiation is increased, which stimulates the total heat transfer. With this optimized passive cooling strategy, thermal issue of LED filament bulb can be mitigated largely and cost-performance ratio is at a relatively low level.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"45 14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122614517","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 : 2017-05-01DOI: 10.1109/ITHERM.2017.7992460
T. Crittenden, S. Jha, A. Glezer
Heat transport within rectangular, mm-scale channels of forced convection heat sinks is enhanced by the aeroelastic fluttering of cantilevered planar thin-film reeds protruding into the channels. The shedding of a train of counter-rotating vortical structures induced by the motion of the reeds and their effects on heat transfer from the channel walls are investigated in two separate testbeds. The interaction of the reeds with the cross flow in the channels is investigated in a single channel model using PIV with specific emphasis on the formation, shedding, and advection of small-scale vorticity concentrations that lead to enhanced mixing of the core flow and enhanced dissipation reminiscent of a fully-developed turbulent channel flow. Heat transfer enhancement is investigated using a pair of back-to-back heat sinks with a common heater that model the fins of an air-cooled condenser. It is demonstrated that the power dissipation and temperature in the heat sink base flow can be matched at reduced air flow rate with the addition of the reeds (for example, between Re = 1,000 baseline and 775 with reeds). The reduction in the required air volume flow rate indicates the potential for lower system-level losses of the cooling air flow and consequently significant reductions in the cooling power.
{"title":"Forced convection heat transfer enhancement in heat sink channels using aeroelastically fluttering reeds","authors":"T. Crittenden, S. Jha, A. Glezer","doi":"10.1109/ITHERM.2017.7992460","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992460","url":null,"abstract":"Heat transport within rectangular, mm-scale channels of forced convection heat sinks is enhanced by the aeroelastic fluttering of cantilevered planar thin-film reeds protruding into the channels. The shedding of a train of counter-rotating vortical structures induced by the motion of the reeds and their effects on heat transfer from the channel walls are investigated in two separate testbeds. The interaction of the reeds with the cross flow in the channels is investigated in a single channel model using PIV with specific emphasis on the formation, shedding, and advection of small-scale vorticity concentrations that lead to enhanced mixing of the core flow and enhanced dissipation reminiscent of a fully-developed turbulent channel flow. Heat transfer enhancement is investigated using a pair of back-to-back heat sinks with a common heater that model the fins of an air-cooled condenser. It is demonstrated that the power dissipation and temperature in the heat sink base flow can be matched at reduced air flow rate with the addition of the reeds (for example, between Re = 1,000 baseline and 775 with reeds). The reduction in the required air volume flow rate indicates the potential for lower system-level losses of the cooling air flow and consequently significant reductions in the cooling power.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"63 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126279604","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 : 2017-05-01DOI: 10.1109/ITHERM.2017.7992514
M. Fish, P. McCluskey, A. Bar-Cohen
A series of single-phase water microgap cooling experiments (gap height: 200 μm) are conducted on via arrays in 400 μm thick glass interposers. Surface temperature rise is compared to trials run with bulk Si of the same thickness. The results show that the copper vias are necessary to control the temperature rise of the glass substrate, and that while the via-enhanced interposers do exhibit a larger thermal resistance than silicon, they also provide the desired increase in lateral thermal isolation. As flow rates within the gap are increased (approaching Re=1600), the penalty associated with constraining the flow of heat to the footprint of the via array is mitigated, owing to the reduction in the thermal resistance attributable to the convection boundary.
{"title":"Microgap cooling of via-enhanced glass interposers","authors":"M. Fish, P. McCluskey, A. Bar-Cohen","doi":"10.1109/ITHERM.2017.7992514","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992514","url":null,"abstract":"A series of single-phase water microgap cooling experiments (gap height: 200 μm) are conducted on via arrays in 400 μm thick glass interposers. Surface temperature rise is compared to trials run with bulk Si of the same thickness. The results show that the copper vias are necessary to control the temperature rise of the glass substrate, and that while the via-enhanced interposers do exhibit a larger thermal resistance than silicon, they also provide the desired increase in lateral thermal isolation. As flow rates within the gap are increased (approaching Re=1600), the penalty associated with constraining the flow of heat to the footprint of the via array is mitigated, owing to the reduction in the thermal resistance attributable to the convection boundary.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125529491","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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