2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)最新文献

{"title":"Optimum spacing of vertical parallel plates for combined natural convection and radiation","authors":"Hanry Issavi, F. Barez","doi":"10.1109/ITHERM.2017.7992549","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992549","url":null,"abstract":"The reliability of electronic products depends on their ability to dissipate the heat generated by various components. Application of an array of parallel plates such as a heat sink is a common example of using parallel plates in electronics cooling. The most common practice in dissipation of the heat generated by electronics is by means of natural convection. Others have investigated the optimum spacing of vertical parallel plates for the maximum natural convection heat transfer. The goal of this study is to determine the optimum spacing for the maximum combined natural convection and radiation heat transfer from an array of isothermal parallel plates. An exact correlation was obtained to determine the optimum spacing for the maximum radiation heat transfer alone. It is concluded that the optimum spacing for the combined natural convection and radiation heat transfer is similar to that of the optimum spacing of the natural convection alone. An exact correlation was also obtained to determine the optimum spacing for combined heat transfer.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"27 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":"115202696","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Long term isothermal aging effects on the cyclic stress-strain behavior of Sn-Ag-Cu solders","authors":"Nianjun Fu, J. Suhling, S. Hamasha, P. Lall","doi":"10.1109/ITHERM.2017.7992637","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992637","url":null,"abstract":"When exposed to a temperature changing environment, solder joints in electronic assemblies are subjected to cyclic mechanical loading due to the mismatches in coefficients of thermal expansion (CTE) of different assembly materials. Eventually, the cyclic loading results in fatigue failure of solder joints, which is one of the common failure modes in electronic packaging. Aging leads to solder microstructure changes such as grain and phase coarsening, and these effects are closely correlated to the damage that occurs during cyclic loading. In this investigation, we have studied long term isothermal aging effects on the cyclic stress-strain behavior and microstructure of Sn-Ag-Cu (SAC) lead free solders. Cylindrical uniaxial specimens were produced using a vacuum suction process and then aged for various aging times up to one year before testing. All the specimens were tested at room temperature (25 °C) using strain controlled cycling method. We have found that aging causes the degradation of solder mechanical properties. The evolution of cyclic stress-strain curve (hysteresis loop) induced by aging has been characterized. Also, the effects of aging on hysteresis loop area, plastic strain range and peak stress have been quantified and modeled for different aging times. Lastly, aging induced microstructural changes in a small fixed region of a single solder sample have been examined, and the coarsening of solder microstructure has been observed.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"32 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":"114993049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"FE analyses and power cycling tests on the thermo-mechanical performance of silver sintered power semiconductors with different interconnection technologies","authors":"R. Dudek, R. Döring, A. Otto, S. Rzepka, S. Stegmeier, S. Kiefl, A. Lunding, R. Eisele","doi":"10.1109/ITHERM.2017.7992618","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992618","url":null,"abstract":"The paper reports on thermo-mechanical performance analyses of power semiconductors. Realistic transient temperature loadings as well as mechanical stresses were simulated by fully coupled electro-thermal-mechanical finite element analyses for power cycling loads. Power cycling tests were run in parallel to the theoretical investigations. The failure modes observed by testing were analyzed and adjusted to FE results. Some of the failures need a sophisticated evaluation strategy, as failure initiates at bi-material free edges, which obey a mechanical stress singularity. Damage mechanical modelling by means of the cohesive zone method (CZM) was adopted along with the coupled finite element analysis (FEA) in those cases. Applications of the methodology are presented for a SiC Mosfet testing sample operating at medium power and a high voltage inverter module with insulated gate bipolar transistors (IGBTs) and diodes, operating at high power. Both modules use silver sintering technology on directly bonded copper (DBC) substrates. Top interconnects are made by wire bonding for the Mosfet test sample but by an electroplating based planar technology for the inverter. Considering electro-thermal results it was calculated that stacks with planar copper interconnects outperform the wire bonded versions by 15–30% dependent on layout and current concerning thermal performance. For the die bonds, networks of cracks in the DCB copper and the silver layer replace the creep-ratchetting mechanism dominant for soft-soldered dies. This failure mode could be attributed to high cyclic in-plane normal stresses leading to subcritical crack growth at high power cycle numbers. The failure mode wire bond lift-off, characteristic for heavy Al wires, was investigated by CZM. The CZM methodology was also adopted to evaluate planar metallization delamination. For the latter, a parametric study has been made to optimize the materials choice and the layout of the metallization.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"35 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":"116312307","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A study of thermal performance in novel radial pulsating heat-pipe systems","authors":"B. Kelly, Y. Kim, Y. Hayashi","doi":"10.1109/ITHERM.2017.7992540","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992540","url":null,"abstract":"As technology becomes increasingly miniaturized, extremely localized heat dissipation (so called hot-spot) leads to the challenge of how to keep devices from overheating. Heat dissipation from advanced power and military electronics is expected to be on the order of 1 kW/cm2, while conventional cooling techniques can only cool up to <10 W/cm2 with forced air convection cooling and <500 W/cm2 with advanced microchannel liquid cooling. In the present study, we propose and investigate a novel radial pulsating heat-pipe (RPHP), which is tailored for effective “spreading of heat” from a local high heat-flux hot-spot. An experimental system for RPHP was constructed with a 110 mm diameter circular brass plate with 1 mm depth and 1 mm width primary channels. The primary channels are enclosed using a polycarbonate cover that is equipped with an internal working fluid charging port. The diameters of the boiling chamber (or evaporator section) and the condenser section were 10 mm and 60 mm, respectively. Thermocouples were installed to measure the temperatures of RPHP surface and the working fluid. The pressure of the fluid in the boiling chamber (evaporator section) was measured using an absolute pressure transducer. The measured data was used to evaluate the thermal performance of the RPHP in terms of thermal resistance with respect to working fluid fill ratio and power input.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"6 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":"123460448","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experiments on the simultaneous two-phase liquid cooling of multiple simulated servers at differing vertical rack positions in steady state","authors":"Felipe Valenzuela, A. Ortega, Gerard F. Jones, A. Fleischer, S. Schon, Russell Tipton","doi":"10.1109/ITHERM.2017.7992577","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992577","url":null,"abstract":"An experimental study was conducted to examine the behavior of a refrigerant two-phase system for cooling multiple servers at differing vertical locations within a standard data center rack. In such racks, the vertically stacked servers may operate at different utilization levels and hence may have differing power dissipations. Furthermore, these distinct power dissipations may occur at differing vertical levels in the rack and may be time-dependent as a result of IT workload scheduling. A reliable two phase cooling system must operate in a stable and controllable fashion under these conditions and the design and characterization of such a system is the topic of this study. An experimental rig was developed for evaluating both pumped and non-pumped (thermosyphon) refrigerant two-phase systems for cooling simulated CPU's in both steady and transient scenarios, and with multiple simulated CPU's operating at distinct vertical positions. Each server flow branch was supplied by a common supply manifold, absorbing the heat at the CPU's using a mini-channel evaporator and returning the two-phase flow to a chilled water cooled plate condenser. Precise measurements were made of the mass flow rate to each branch as well as temperatures and pressures at all key system locations, allowing the identification of thermodynamic state at all relevant system positions. This paper presents preliminary experimental results for two simultaneously operating servers at different vertical positions and with different heat loads operating in steady state, in both pumped and non-pumped modes. It is shown that the system operation is stable in both modes for the two-server case. The flow rate branches evenly in the pumped case, with little effect of vertical position. In the non-pumped thermosyphon operation, flow rate to each server location is not affected by is power dissipation and vertical position.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"53 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":"121940499","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Self-adaptive microvalve array for energy efficient fluidic cooling in microelectronic systems","authors":"H. Azarkish, J. Barrau, P. Coudrain, G. Savelli, L. Collin, L. Fréchette","doi":"10.1109/ITHERM.2017.7992531","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992531","url":null,"abstract":"In the present work, the performance of temperature-regulated microvalves is investigated analytically for energy efficient fluidic cooling of microelectronic systems. The objectives are to decrease the overall mass flow rate of coolant (hence decreasing the pumping power) as well as to improve the temperature uniformity across the chip surface with hot spots. For this purpose, temperature-regulated microvalves are used to manage the coolant mass flow rate distribution throughout the chip based on the local chip temperature. The aim of this study is to find the optimum temperature response function of the microvalves to have more energy efficient cooling. Linear, quadratic and exponential temperature response behaviors are considered for the microvalves. Results show that for the linear microvalves, the mass flow rate and the temperature non-uniformity across the chip decrease by 50% and 29% respectively by using active self-adaptive microvalves, compared to the reference condition without any microvalve. These enhancement values are respectively 45% and 55% when using exponential instead of linear microvalves. This study shows that the concept of self-adaptive microvalve arrays for distributed chip cooling can have a significant impact on power and performance, opening a new approach for microfluidic cooling compared to traditional fixed microchannels.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"145 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":"129724802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Parametric study of spatially-uniform mini-channel heat sinks using a porous media modeling approach","authors":"John J. Podhiny, A. Ortega","doi":"10.1109/ITHERM.2017.7992484","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992484","url":null,"abstract":"Pumped-liquid single-pass heat sinks with channel dimensions on the order of 0.1mm to 1.0mm are commonly researched for cooling small-scale electronic devices that generate high heat fluxes. This paper presents a simulation-based parametric study that investigates the steady-state thermal and hydrodynamic performance of 1,014 unique designs that employ square channels of a uniform size that are evenly distributed throughout the heat sink. The volume-averaged two-equation porous media model is used to simulate thermal behavior and provides the 2D spatial distributions of solid and fluid phase temperatures. Hydrodynamic behavior of the coolant is modeled using Darcy's law. The model is implemented via a user-defined element in the commercial finite element analysis code Abaqus. Thermal response is found to fall into two regimes which are defined based on an effective Biot number. Response in the low-Biot regime is found to scale with an effective resistance that is composed of a fin-type resistance (which the authors have not encountered previously) and an advective resistance. Response in the high-Biot regime is found to scale with an effective resistance that is composed of the conductive, convective and advective resistances. Hydrodynamic performance is assessed briefly, and as expected, does not follow the same trends as thermal performance. A basic design methodology for this class of heat sink is also discussed.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"28 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":"127305734","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"NiyanTron — An approach to develop a control system app for data center cooling","authors":"V. Rahul, A. Darekar, Rajesh Kasukurthy, Ashwin Sidharth, D. Agonafer","doi":"10.1109/ITHERM.2017.7992590","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992590","url":null,"abstract":"This study addresses a Data Center Cooling Control System App designed and developed to make the existing technology modular and economical. The project has been carried out using standard lab equipment and software. The emphasis of the study is on conditioning the outside air by using the cooling systems that aren't energy intensive and hence reduce the overall cost of operation. The paper also discusses the results, cost analysis and future scope while implementing this niche technology. The app is titled ‘NiyanTron’, a portmanteau of the Hindi word Niyantran meaning control and elecTRONic, as the app is an electronic control system. The study was carried out for environmental conditions in four cities — Albuquerque, NM, Dallas, TX, Chicago, IL and Tucson, AZ. The weather information from the four regions was used as the preliminary data to run the control system and show the versatility of the app. The modes Economizer and Return Air cooling have been used for Chicago and Dallas. Tucson and Albuquerque have Direct Evaporative Cooling and Economizer mode. Further, the use of Glassdek and Celdek media has been compared.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"1 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":"130145923","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Parametric investigation of a raised-floor data center cooling using a reversible fan system","authors":"Zhihang Song, J. Dong","doi":"10.1109/ITHERM.2017.7992580","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992580","url":null,"abstract":"The active tile cooling has become one advanced thermal management approach for offering an appropriate amount of cooling air to raised-floor data centers. However, difficulty remains to alleviate the waste of the CRAC-supplied cooling air when the data center is over-cooled. In view of this concern, this paper especially investigated a reversible fan system, including a ductwork assembly and a fan unit. This configuration was capable of delivering cooling air upwards into the above-floor space as well as working oppositely to draw unnecessary cooling air backwards into the under-floor plenum to be a smart solution. In this way, the fan unit was able to control the airflow of the perforated tile more flexibly than the conventional fan unit of the active tile systems. The computational fluid dynamics (CFD) model was established to analyze the performance of a raised-floor data center cooling using the reversible fan system, and the key operating conditions (e.g., the rotational speed, rotational direction and the vertical position of the reversible fan unit) were defined and the airflow/thermal performances (e.g., local rack inlet temperature, and the air flow distribution in the cold aisle) were observed and compared carefully. Eventually, the results indicate that the reversible fan system is capable of managing the airflow and thermal distributions efficiently and economically.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"132 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":"131070891","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Molecular dynamics simulation of the effect of the solid gas interface nanolayer on enhanced thermal conductivity of copper-CO2 nanofluid","authors":"Z. Ahmed, A. Sarode, Pratik Basarkar, A. Bhargav, Debjyoti Baneijee","doi":"10.1109/ITHERM.2017.7992487","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992487","url":null,"abstract":"The use of CO2 as a natural refrigerant in data center cooling, in oil recovery and in CO2 capture and storage is gaining traction in recent years. These applications involve heat transfer between CO2 and the base fluid, and hence, there arises a need to improve the thermal conductivity of CO2 to increase the process efficiency and reduce cost. One way to improve the thermal conductivity is through nanoparticle addition in the base fluid. The nanofluid model in this study consisted of copper (Cu) nanoparticles in varying concentrations with CO2 as a base fluid. No experimental data is available on thermal conductivity of CO2 based nanofluid. Molecular dynamics (MD) simulations are being increasingly adopted as a tool to perform preliminary assessments of nanoparticle (NP) fluid interactions. In this study, the effect of the formation of a nanolayer (or molecular layering) at the gas-solid interface on thermal conductivity is investigated using equilibrium MD simulations by varying nanoparticle diameter and keeping the volume fraction (1.413%) of nanofluid constant to check the diameter effect of nanoparticle on the nanolayer and thermal conductivity. A dense semi-solid fluid layer was seen to be formed at the nanoparticle-gas interface, and the thickness increases with increase in particle diameter, which also moves with the nanoparticle Brownian motion. Density distribution has been done to see the effect of nanolayer, and its thickness around the nanoparticle.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"43 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":"132499687","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}