Pub Date : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190182
Jiajun Xu, Christopher Hendricks
Lithium-ion batteries (LIB) have found a wide range of applications in many consumer products in the last 25 years. The United States Navy and Marine Corps have various applications using LIB, and safe battery technologies are critically needed. While many consumer applications typically utilize smaller high capacity cells, military applications can utilize specialty large-format (>30 Ah) cells in their LIB packs. One of the most important safety considerations for LIB cells is their thermal stability under various abuses such as exposure to heat, nail penetration, external short circuit, crushing, and so on. Several exothermic reactions can occur as the inner cell temperature increases, and if the heat generation is larger than the dissipated heat to the surroundings, this leads to heat accumulation in the cell and acceleration of the chemical reactions, which can then lead to a thermal runaway. To understand and control thermal runaway, many researchers have formulated complex mathematical models and built experimental set-ups for investigating the phenomenon in detail. However, most of the studies focused on the effect of thermal runaway event, while no detailed numerical analysis on the vaporization of the electrolyte and the correlation of electrochemical reactions with overcharge in large-format LIB has been reported yet. So this study reports the recently developed electrochemical-thermal coupled gas generation and overcharge-to-thermal-runaway model for a large-format lithium-ion battery tested at NSWCCD using COMSOL software.
{"title":"An Electrochemical-thermal Coupled Gas Generation and Overcharge-to-thermal-runaway Model for Large-format Lithium Ion Battery","authors":"Jiajun Xu, Christopher Hendricks","doi":"10.1109/ITherm45881.2020.9190182","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190182","url":null,"abstract":"Lithium-ion batteries (LIB) have found a wide range of applications in many consumer products in the last 25 years. The United States Navy and Marine Corps have various applications using LIB, and safe battery technologies are critically needed. While many consumer applications typically utilize smaller high capacity cells, military applications can utilize specialty large-format (>30 Ah) cells in their LIB packs. One of the most important safety considerations for LIB cells is their thermal stability under various abuses such as exposure to heat, nail penetration, external short circuit, crushing, and so on. Several exothermic reactions can occur as the inner cell temperature increases, and if the heat generation is larger than the dissipated heat to the surroundings, this leads to heat accumulation in the cell and acceleration of the chemical reactions, which can then lead to a thermal runaway. To understand and control thermal runaway, many researchers have formulated complex mathematical models and built experimental set-ups for investigating the phenomenon in detail. However, most of the studies focused on the effect of thermal runaway event, while no detailed numerical analysis on the vaporization of the electrolyte and the correlation of electrochemical reactions with overcharge in large-format LIB has been reported yet. So this study reports the recently developed electrochemical-thermal coupled gas generation and overcharge-to-thermal-runaway model for a large-format lithium-ion battery tested at NSWCCD using COMSOL software.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130974512","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 : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190161
K. Ebrahimi, Sasan Ebrahimi, Khosrow Ebrahimi
Thermal management is necessary to dissipate heat from semiconductors while keeping system efficiency high. There is a clear need for compact, effective, reliable, high-capacity, and quiet, passive cooling systems in the power electronics industry. A novel Smith-Volterra-Cantor (SVC) set fractal heat-sink is introduced and numerically investigated for natural convection. The SVC fractal pattern increases the heat transfer area and interrupts the thermal and aerodynamic boundary layers. The heat-sink mass and size are reduced with the SVC fractal design compared to the classical ones that make compact passive cooling system design feasible. The thermal performance of the fractal heat-sink is detailed, considering the fin scale and surface heat flux. The analysis indicates mass normalized fin effectiveness is improved, and the temperature is more uniformly distributed for fractal design. These results are applicable for the development of compact power-electronics passive thermal management design for telecommunication and aviation applications with reduced parasitic powers, noise, and vibration.
{"title":"Fractal Pattern Effects on Natural Convection Heat Transfer and Flow Characteristics","authors":"K. Ebrahimi, Sasan Ebrahimi, Khosrow Ebrahimi","doi":"10.1109/ITherm45881.2020.9190161","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190161","url":null,"abstract":"Thermal management is necessary to dissipate heat from semiconductors while keeping system efficiency high. There is a clear need for compact, effective, reliable, high-capacity, and quiet, passive cooling systems in the power electronics industry. A novel Smith-Volterra-Cantor (SVC) set fractal heat-sink is introduced and numerically investigated for natural convection. The SVC fractal pattern increases the heat transfer area and interrupts the thermal and aerodynamic boundary layers. The heat-sink mass and size are reduced with the SVC fractal design compared to the classical ones that make compact passive cooling system design feasible. The thermal performance of the fractal heat-sink is detailed, considering the fin scale and surface heat flux. The analysis indicates mass normalized fin effectiveness is improved, and the temperature is more uniformly distributed for fractal design. These results are applicable for the development of compact power-electronics passive thermal management design for telecommunication and aviation applications with reduced parasitic powers, noise, and vibration.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133103891","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 : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190946
P. Lall, Tony Thomas, K. Blecker
This paper focusses on the prognostics of damage for a PCB under varying conditions of shock loads. The test board is a multilayer FR4 of JEDEC standard JESD22-B111 specified dimension with 12 packages that are arranged in a rectangular pattern. Health monitoring of the bare printed circuit boards under different drop and shock loads are studied in this analysis from the strain signals acquired from different locations of the board. The test boards are subjected to different shock loads of 3,000, 5000, 7000, and 10,000g acceleration to understand the failure of the packages during these various shock levels. Further, the analysis of varying shocks loads on the same test boards was also carried out to understand the effectiveness of the feature vector in predicting failure during varying load conditions. The strain signals that are acquired from four different locations of the test board during each drop are used for the identification of feature vectors that can predict the failure. The resistance measurements of the packages are used to identify the failure of packages during the drop. The health of the PCB is studied from the strain signal acquired from the strain gauges fixed at four different locations of the test board. The strain signals are processed, and various feature vectors are identified to predict the failure of the package during drop based on the time-domain and frequency-domain characteristics of the strain signal. The time-domain characteristics quantified the variation of the shape and profile of each peak of the damped strain signal, and the frequency-domain studied the characteristic change in the frequency components during each drop of the test board. Different data processing algorithms are used in dimension reduction and feature extraction from the strain signal and frequency components of the strain signal. A comparative study on the difference in the four strain signals under varying conditions of the load and sustainability of the feature vectors at different conditions of load and differences in the feature vectors with the position of the strain gauge is also studied.
{"title":"Health Monitoring and Feature Vector Identification of Failure for SAC305 Solder PCB’s under Shock Loads up to 10,000g","authors":"P. Lall, Tony Thomas, K. Blecker","doi":"10.1109/ITherm45881.2020.9190946","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190946","url":null,"abstract":"This paper focusses on the prognostics of damage for a PCB under varying conditions of shock loads. The test board is a multilayer FR4 of JEDEC standard JESD22-B111 specified dimension with 12 packages that are arranged in a rectangular pattern. Health monitoring of the bare printed circuit boards under different drop and shock loads are studied in this analysis from the strain signals acquired from different locations of the board. The test boards are subjected to different shock loads of 3,000, 5000, 7000, and 10,000g acceleration to understand the failure of the packages during these various shock levels. Further, the analysis of varying shocks loads on the same test boards was also carried out to understand the effectiveness of the feature vector in predicting failure during varying load conditions. The strain signals that are acquired from four different locations of the test board during each drop are used for the identification of feature vectors that can predict the failure. The resistance measurements of the packages are used to identify the failure of packages during the drop. The health of the PCB is studied from the strain signal acquired from the strain gauges fixed at four different locations of the test board. The strain signals are processed, and various feature vectors are identified to predict the failure of the package during drop based on the time-domain and frequency-domain characteristics of the strain signal. The time-domain characteristics quantified the variation of the shape and profile of each peak of the damped strain signal, and the frequency-domain studied the characteristic change in the frequency components during each drop of the test board. Different data processing algorithms are used in dimension reduction and feature extraction from the strain signal and frequency components of the strain signal. A comparative study on the difference in the four strain signals under varying conditions of the load and sustainability of the feature vectors at different conditions of load and differences in the feature vectors with the position of the strain gauge is also studied.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133808121","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 : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190514
P. Lall, Tony Thomas, Jinesh Narangaparambil, Kartik Goyal, Hye-Yoen Jang, Vikas Yadav, Wei Liu
The increase in the use of flexible electronics in wearable applications has resulted in an increased focus on the study of movement characteristics of the human body and its impact on electronics under various day-to-day actions. The flexible electronics that are attached to the human body are tested for reliability under various conditions of human activity such as walking, jumping, squats, lunges, and bicep curls. The human body motion data during these different actions were measured using a set of ten Vicon cameras to measure the position, velocity, and accelerations of a standard full-body sensor location of a human body. The reliability model presented in this study uses the angle variations of each joint in the human body for all the five human activities listed above. Statistical analysis on the difference of each joint angle was tested with hypothesis testing strategies with different subjects and with various human body actions as well. Acceleration factor modeling on the reliability of the electronics was carried out using test data of flexible electronics subjected to bending, twisting, stretching, and folding experiments. These experiments are conducted on flexible electronic substrates until failure with in-situ resistance measurements to monitor the changes in the board during each of these experiments. The experimental measurements of the boards were combined with the human body motion data to model the acceleration factor for each of these tests.
{"title":"Correlation of Accelerated Tests with Human Body Measurements for Flexible Electronics in Wearable Applications","authors":"P. Lall, Tony Thomas, Jinesh Narangaparambil, Kartik Goyal, Hye-Yoen Jang, Vikas Yadav, Wei Liu","doi":"10.1109/ITherm45881.2020.9190514","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190514","url":null,"abstract":"The increase in the use of flexible electronics in wearable applications has resulted in an increased focus on the study of movement characteristics of the human body and its impact on electronics under various day-to-day actions. The flexible electronics that are attached to the human body are tested for reliability under various conditions of human activity such as walking, jumping, squats, lunges, and bicep curls. The human body motion data during these different actions were measured using a set of ten Vicon cameras to measure the position, velocity, and accelerations of a standard full-body sensor location of a human body. The reliability model presented in this study uses the angle variations of each joint in the human body for all the five human activities listed above. Statistical analysis on the difference of each joint angle was tested with hypothesis testing strategies with different subjects and with various human body actions as well. Acceleration factor modeling on the reliability of the electronics was carried out using test data of flexible electronics subjected to bending, twisting, stretching, and folding experiments. These experiments are conducted on flexible electronic substrates until failure with in-situ resistance measurements to monitor the changes in the board during each of these experiments. The experimental measurements of the boards were combined with the human body motion data to model the acceleration factor for each of these tests.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"175 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124301136","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 : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190381
Diego Vaca, Luke Yates, N. Nepal, D. Katzer, B. Downey, V. Wheeler, D. Meyer, S. Graham, Satish Kumar
β-Ga2O3 is considered as a promising material for future power electronic applications. In this work, we used time-domain thermoreflectance to measure the thermal conductivity and thermal boundary conductance (TBC) of thin films of β-Ga2O3 grown using molecular beam epitaxy (MBE) on c-Al2O3 (sapphire) and 4H-SiC substrates. One sample was 119 nm thick on sapphire, while the other sample was 81 nm thick on 4H-SiC. The Ga2O3 layer on c-sapphire presented a through-plane thermal conductivity of 3.2 ± 0.3 W/m-K with a Ga2O3/sapphire TBC of 155.6 ± 65.3 MW/m2-K. The thermal conductivity of the Ga2O3 layer on 4H-SiC was measured as 3.1 ± 0.5 W/m-K with a Ga2O3/SiC TBC of 141.8 ± 63.8 MW/m2-K. When compared with the thermal conductivity of films grown using pulsed-laser deposition from a previous study, thermal conductivity of layers grown by MBE show higher values, which suggests that the films grown by epitaxial method such as MBE can improve the thermal conductivity of thin films.
{"title":"Thermal Conductivity of β-Ga2O3 Thin Films Grown by Molecular Beam Epitaxy","authors":"Diego Vaca, Luke Yates, N. Nepal, D. Katzer, B. Downey, V. Wheeler, D. Meyer, S. Graham, Satish Kumar","doi":"10.1109/ITherm45881.2020.9190381","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190381","url":null,"abstract":"β-Ga<inf>2</inf>O<inf>3</inf> is considered as a promising material for future power electronic applications. In this work, we used time-domain thermoreflectance to measure the thermal conductivity and thermal boundary conductance (TBC) of thin films of β-Ga<inf>2</inf>O<inf>3</inf> grown using molecular beam epitaxy (MBE) on c-Al<inf>2</inf>O<inf>3</inf> (sapphire) and 4H-SiC substrates. One sample was 119 nm thick on sapphire, while the other sample was 81 nm thick on 4H-SiC. The Ga<inf>2</inf>O<inf>3</inf> layer on c-sapphire presented a through-plane thermal conductivity of 3.2 ± 0.3 W/m-K with a Ga<inf>2</inf>O<inf>3</inf>/sapphire TBC of 155.6 ± 65.3 MW/m<sup>2</sup>-K. The thermal conductivity of the Ga<inf>2</inf>O<inf>3</inf> layer on 4H-SiC was measured as 3.1 ± 0.5 W/m-K with a Ga<inf>2</inf>O<inf>3</inf>/SiC TBC of 141.8 ± 63.8 MW/m<sup>2</sup>-K. When compared with the thermal conductivity of films grown using pulsed-laser deposition from a previous study, thermal conductivity of layers grown by MBE show higher values, which suggests that the films grown by epitaxial method such as MBE can improve the thermal conductivity of thin films.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"72 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123212044","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 : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190944
Huihui Xu, Kunpeng Lin, C. Ehrenpreis, Grégoire Roux, R. D. De Doncker
Advanced cooling methods, especially direct oil cooling, are used to maximize the power density of electrical traction machines. However, thermal monitoring with temperature sensors can only provide limited information about the thermal stress distribution. This work combines computational fluid dynamics and lumped parameter thermal networks to develop a thermal model of a prototype machine with direct oil cooling. The generated model represents the inhomogeneous spatial temperature distribution caused by the asymmetrical oil distribution in radial and axial direction of the machine. The proposed method allows a rapid study of the thermal behavior of electrical machines with direct oil cooling. Experimental measurements validate the accuracy of the thermal model. The temperature difference between simulations and measurements is within 5 °C.
{"title":"Thermal Modeling of Electrical Machines with Advanced Fluid Cooling","authors":"Huihui Xu, Kunpeng Lin, C. Ehrenpreis, Grégoire Roux, R. D. De Doncker","doi":"10.1109/ITherm45881.2020.9190944","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190944","url":null,"abstract":"Advanced cooling methods, especially direct oil cooling, are used to maximize the power density of electrical traction machines. However, thermal monitoring with temperature sensors can only provide limited information about the thermal stress distribution. This work combines computational fluid dynamics and lumped parameter thermal networks to develop a thermal model of a prototype machine with direct oil cooling. The generated model represents the inhomogeneous spatial temperature distribution caused by the asymmetrical oil distribution in radial and axial direction of the machine. The proposed method allows a rapid study of the thermal behavior of electrical machines with direct oil cooling. Experimental measurements validate the accuracy of the thermal model. The temperature difference between simulations and measurements is within 5 °C.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117001959","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}
Unprecedented computing power is pursued for the next generation of big data, cloud computing and artificial intelligence, and it is driving all kinds of new technology in semiconductor industry now. Integrated fan-out on substrate (InFO_oS) packaging technology emerges as one of the innovative package solutions to connect multiple dies, and therefore could deliver higher performance than conventional one-die package. Due to extremely high power is accommodated in one single package, accurate thermal analysis of it is crucial to avoid thermal issue of integrated chips.In order to understand the thermal characteristic of integrated fan-out on substrate package, not only a detailed package thermal model was constructed but also a thermal test vehicle (TTV) was developed in this work. Standard JEDEC package thermal resistance of junction-to-case experiments was conducted with large body InFO_oS TTV, including multiple heat sources. It is shown that the thermal model can achieve great accuracy compared with measurement result. Meanwhile, as thermal interface material (TIM) between die and metal lid plays a big role of thermal resistance of junction-to-case, different kinds of TIM materials were adopted in this TTV to characterize their thermal performance. The effect of bond line thickness (BLT) of TIM was also investigated as it is another key factor.In this study, a detail InFO_oS thermal model was verified and fundamental thermal characteristic of it was completed. Furthermore, based on the correlated thermal model, a series of thermal simulation was executed to study thermal power budget with advanced thermal solutions and with different TIM materials adopted in InFO_oS package. It would be practical and beneficial to implement this methodology in design phase to reduce thermal risk in system application of end product.
{"title":"Thermal Characteristics of Integrated Fan-Out on Substrate (InFO_oS) Packaging Technology","authors":"Chia-Hao Hsu, Yi-Jou Lin, Sheng-Liang Kuo, Yi Peng, Chi-Wen Pan, Tai-Yu Chen, Wen-Sung Hsu","doi":"10.1109/ITherm45881.2020.9190542","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190542","url":null,"abstract":"Unprecedented computing power is pursued for the next generation of big data, cloud computing and artificial intelligence, and it is driving all kinds of new technology in semiconductor industry now. Integrated fan-out on substrate (InFO_oS) packaging technology emerges as one of the innovative package solutions to connect multiple dies, and therefore could deliver higher performance than conventional one-die package. Due to extremely high power is accommodated in one single package, accurate thermal analysis of it is crucial to avoid thermal issue of integrated chips.In order to understand the thermal characteristic of integrated fan-out on substrate package, not only a detailed package thermal model was constructed but also a thermal test vehicle (TTV) was developed in this work. Standard JEDEC package thermal resistance of junction-to-case experiments was conducted with large body InFO_oS TTV, including multiple heat sources. It is shown that the thermal model can achieve great accuracy compared with measurement result. Meanwhile, as thermal interface material (TIM) between die and metal lid plays a big role of thermal resistance of junction-to-case, different kinds of TIM materials were adopted in this TTV to characterize their thermal performance. The effect of bond line thickness (BLT) of TIM was also investigated as it is another key factor.In this study, a detail InFO_oS thermal model was verified and fundamental thermal characteristic of it was completed. Furthermore, based on the correlated thermal model, a series of thermal simulation was executed to study thermal power budget with advanced thermal solutions and with different TIM materials adopted in InFO_oS package. It would be practical and beneficial to implement this methodology in design phase to reduce thermal risk in system application of end product.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117098866","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 : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190404
P. Subrahmanyam, Y. Pang, Muhammad Ahmad, Amy Xia
The heat transfer distributions of axisymmetric confined turbulent jets impinging on a high power density silicon issued from dual primary circular nozzles and accelerated under tapered nozzles has been extensively investigated in this research to discretize the flow field characteristics under submerged conditions. Sixteen RANS CFD simulations with processed chilled water as impingement fluid by varying Reynolds number 8000 ≤ Re ≤ 20000 (based on the main inlet nozzle jet diameter and bulk velocity) and the nozzle jet orifice plate to the die standoff distance 4 ≤ z/d ≤ 16 (up to sixteen nozzle jet diameters distance) is researched along with four distinct LES cases at a Reynolds of 20000. The nozzle plate has 20 tapered nozzles used to distribute and accelerate the flow under the dual circular nozzles where the flow is initially issued from. The CFD RANS simulations for dual circular primary nozzles are compared to the CFD cases of the single primary nozzle cases published previously. An overall heat transfer coefficient to the order of 179,000 W/m2°K has been observed on the surface of the silicon when the flow is issued from a single primary nozzle and an overall heat transfer coefficient to the order of 333,000 W/m2°K has been observed when the jets are issued from dual primary nozzles for identical jet-to-wall distance. Large Eddy Simulations are used to predict the flow-field turbulent characteristics of dual circular jets impinging directly on the silicon wall for four significant cases with varying (0.5 ≤ z/d ≤ 2) distances at a Reynolds (Re) of 20,000 issued from main nozzle and the results are compared to the four LES cases of single nozzle direct impingement that is published previously. Results from these simulations reveal intricate features of flow field distributions including primary and secondary vortices, entrainment effects on the bare die hot silicon and guides the design of the impingement setup in terms of nozzle configuration, maximum power and power density dissipation criteria that can be met for a given nozzle configuration and impingement setup for hotspot mitigation.
{"title":"Effects of Jet to Wall Spacings on Heat Transfer Characteristics And Flow Fields of Turbulently Impinging Nozzled Jets on Hot Silicon","authors":"P. Subrahmanyam, Y. Pang, Muhammad Ahmad, Amy Xia","doi":"10.1109/ITherm45881.2020.9190404","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190404","url":null,"abstract":"The heat transfer distributions of axisymmetric confined turbulent jets impinging on a high power density silicon issued from dual primary circular nozzles and accelerated under tapered nozzles has been extensively investigated in this research to discretize the flow field characteristics under submerged conditions. Sixteen RANS CFD simulations with processed chilled water as impingement fluid by varying Reynolds number 8000 ≤ Re ≤ 20000 (based on the main inlet nozzle jet diameter and bulk velocity) and the nozzle jet orifice plate to the die standoff distance 4 ≤ z/d ≤ 16 (up to sixteen nozzle jet diameters distance) is researched along with four distinct LES cases at a Reynolds of 20000. The nozzle plate has 20 tapered nozzles used to distribute and accelerate the flow under the dual circular nozzles where the flow is initially issued from. The CFD RANS simulations for dual circular primary nozzles are compared to the CFD cases of the single primary nozzle cases published previously. An overall heat transfer coefficient to the order of 179,000 W/m2°K has been observed on the surface of the silicon when the flow is issued from a single primary nozzle and an overall heat transfer coefficient to the order of 333,000 W/m2°K has been observed when the jets are issued from dual primary nozzles for identical jet-to-wall distance. Large Eddy Simulations are used to predict the flow-field turbulent characteristics of dual circular jets impinging directly on the silicon wall for four significant cases with varying (0.5 ≤ z/d ≤ 2) distances at a Reynolds (Re) of 20,000 issued from main nozzle and the results are compared to the four LES cases of single nozzle direct impingement that is published previously. Results from these simulations reveal intricate features of flow field distributions including primary and secondary vortices, entrainment effects on the bare die hot silicon and guides the design of the impingement setup in terms of nozzle configuration, maximum power and power density dissipation criteria that can be met for a given nozzle configuration and impingement setup for hotspot mitigation.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126122056","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 : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190296
Mohammed Abueed, Raed Athamenh, S. Hamasha, J. Suhling, P. Lall
Failure due to thermal cycling is common at the solder joint level of electronic assemblies due to the mismatch in the coefficient of thermal expansions between the carrier and printed circuit board. Combined damage mechanisms of creep and fatigue are presented in thermal cycling conditions. Recent studies showed that fatigue damage is dominant during ramps, while creep damage is dominant during dwell times. The amount of damage is highly aggregated when the temperature is elevated. So, it is essential to explore the effect of both damage mechanisms on solder joint reliability, especially at elevated temperatures. In this work, an accelerated shear fatigue test on individual solder joints is used to study the effect of elevated temperature at different stress levels on fatigue life. Individual SAC305 solder joints were cycled in stress-controlled fatigue at various temperature levels of 25°C, 60°C and 100°C using Instron micro-tester machine with a customized fixture. The stress amplitudes include 16, 20, and 24MPa. Hysteresis (stress-strain) loops were generated at different testing conditions, and the inelastic work per cycle is calculated. The results showed that increasing the stress level leads to increasing the inelastic work per cycle and decreasing fatigue life. The fatigue life of the solder joint is reduced significantly with increasing temperature at certain stress levels. Also, the inelastic work per cycle is significantly increased with increasing temperature. The effect of temperature found to create more damage than increasing stress levels. Further experiments with different testing conditions are in progress to study the effect of both creep and fatigue. It would help in quantifying both damages at several temperatures and stress levels.
{"title":"Effect of Fatigue on Individual SAC305 Solder Joints Reliability at Elevated Temperature","authors":"Mohammed Abueed, Raed Athamenh, S. Hamasha, J. Suhling, P. Lall","doi":"10.1109/ITherm45881.2020.9190296","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190296","url":null,"abstract":"Failure due to thermal cycling is common at the solder joint level of electronic assemblies due to the mismatch in the coefficient of thermal expansions between the carrier and printed circuit board. Combined damage mechanisms of creep and fatigue are presented in thermal cycling conditions. Recent studies showed that fatigue damage is dominant during ramps, while creep damage is dominant during dwell times. The amount of damage is highly aggregated when the temperature is elevated. So, it is essential to explore the effect of both damage mechanisms on solder joint reliability, especially at elevated temperatures. In this work, an accelerated shear fatigue test on individual solder joints is used to study the effect of elevated temperature at different stress levels on fatigue life. Individual SAC305 solder joints were cycled in stress-controlled fatigue at various temperature levels of 25°C, 60°C and 100°C using Instron micro-tester machine with a customized fixture. The stress amplitudes include 16, 20, and 24MPa. Hysteresis (stress-strain) loops were generated at different testing conditions, and the inelastic work per cycle is calculated. The results showed that increasing the stress level leads to increasing the inelastic work per cycle and decreasing fatigue life. The fatigue life of the solder joint is reduced significantly with increasing temperature at certain stress levels. Also, the inelastic work per cycle is significantly increased with increasing temperature. The effect of temperature found to create more damage than increasing stress levels. Further experiments with different testing conditions are in progress to study the effect of both creep and fatigue. It would help in quantifying both damages at several temperatures and stress levels.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126126369","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 : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190431
V. Simon, Ashwin Siddarth, D. Agonafer
A data center cooling system consists of a hierarchy of systems with dedicated control algorithms dictating their operational states. There exists a wide range in spatial and temporal parameter space in an ensemble of non-linear dynamic systems, each executing a control task, while the global objective is to drive the overall system to an optimum operating condition i.e. minimum total operational power at desired rack inlet temperatures. Certainly, it is beneficial in optimizing workload migration at temporal scales but, solving the instability of the cooling systems operating at design points helps in understanding the whole system and make predictions to have better control strategies. Several techniques are available to realistically capture and make predictions. Datadriven modelling/Machine learning is one such method that is less expensive in terms of cost and time compared to other methods like validated CFD simulation/experimental setup.The objective of this study is to develop a control framework based on predictions made using machine learning techniques such as Artificial Neural Network (ANN) to operate multiple Computer Room Air Conditioning Units (CRAC) or simply Air-Cooling Units (ACU) in a hot-aisle contained raised floor datacenter. This paper focuses on the methodology of gathering training datasets from numerous CFD simulations (Scenarios) to train the ANN model and make predictions with minimal error.Each rack has a percentage of influence (zones) based on the placement of ACUs and their airflow behavior. These zones are mapped using steady state CFD simulation considering maximum CPU utilization and cooling provisioning. Using this map, ITE racks are targeted and given varying workload to force the corresponding ACU that is responsible for provisioning, to operate at set points. Number of such scenarios are simulated using the same CFD model with fixed bounds and constraints. Using large samples of data collected from CFD results, the ANN is trained to predict values that correspond to the activation of the desired ACU. Such efficient control network would minimize excessive cooling. The validated prediction points are used to model a control framework for the cooling system to quickly reach the operating point. These models can be used in real-time data centers provided; the training data is based on in-house sensor values.
{"title":"Artificial Neural Network Based Prediction of Control Strategies for Multiple Air-Cooling Units in a Raised-floor Data Center","authors":"V. Simon, Ashwin Siddarth, D. Agonafer","doi":"10.1109/ITherm45881.2020.9190431","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190431","url":null,"abstract":"A data center cooling system consists of a hierarchy of systems with dedicated control algorithms dictating their operational states. There exists a wide range in spatial and temporal parameter space in an ensemble of non-linear dynamic systems, each executing a control task, while the global objective is to drive the overall system to an optimum operating condition i.e. minimum total operational power at desired rack inlet temperatures. Certainly, it is beneficial in optimizing workload migration at temporal scales but, solving the instability of the cooling systems operating at design points helps in understanding the whole system and make predictions to have better control strategies. Several techniques are available to realistically capture and make predictions. Datadriven modelling/Machine learning is one such method that is less expensive in terms of cost and time compared to other methods like validated CFD simulation/experimental setup.The objective of this study is to develop a control framework based on predictions made using machine learning techniques such as Artificial Neural Network (ANN) to operate multiple Computer Room Air Conditioning Units (CRAC) or simply Air-Cooling Units (ACU) in a hot-aisle contained raised floor datacenter. This paper focuses on the methodology of gathering training datasets from numerous CFD simulations (Scenarios) to train the ANN model and make predictions with minimal error.Each rack has a percentage of influence (zones) based on the placement of ACUs and their airflow behavior. These zones are mapped using steady state CFD simulation considering maximum CPU utilization and cooling provisioning. Using this map, ITE racks are targeted and given varying workload to force the corresponding ACU that is responsible for provisioning, to operate at set points. Number of such scenarios are simulated using the same CFD model with fixed bounds and constraints. Using large samples of data collected from CFD results, the ANN is trained to predict values that correspond to the activation of the desired ACU. Such efficient control network would minimize excessive cooling. The validated prediction points are used to model a control framework for the cooling system to quickly reach the operating point. These models can be used in real-time data centers provided; the training data is based on in-house sensor values.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124609671","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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