Pub Date : 2000-05-23DOI: 10.1109/ITHERM.2000.866167
Shulin Zeng, Chuan-Hua Chen, J. Mikkelsen, J. Santiago
Electrokinetic (EK) micropumps have been fabricated and demonstrated in which electroosmotic flow is used to transport fluids. Deionized water and pure acetonitrile have been used as working fluids to achieve low current density pumping conditions. These EK pumps have no moving parts and can generate maximum pressures of more than 20 atm at 2 kV applied voltage. Minimizing and controlling electrolytic gas generation is a major concern. Gas generated at the downstream electrode surfaces appears to be forced to dissolve into surrounding fluid at high pressure (>7 atm) condition, and this permits a stable pump operation. Measurements of flow rate have been used to estimate pump structure parameters.
{"title":"Fabrication and characterization of electrokinetic micro pumps","authors":"Shulin Zeng, Chuan-Hua Chen, J. Mikkelsen, J. Santiago","doi":"10.1109/ITHERM.2000.866167","DOIUrl":"https://doi.org/10.1109/ITHERM.2000.866167","url":null,"abstract":"Electrokinetic (EK) micropumps have been fabricated and demonstrated in which electroosmotic flow is used to transport fluids. Deionized water and pure acetonitrile have been used as working fluids to achieve low current density pumping conditions. These EK pumps have no moving parts and can generate maximum pressures of more than 20 atm at 2 kV applied voltage. Minimizing and controlling electrolytic gas generation is a major concern. Gas generated at the downstream electrode surfaces appears to be forced to dissolve into surrounding fluid at high pressure (>7 atm) condition, and this permits a stable pump operation. Measurements of flow rate have been used to estimate pump structure parameters.","PeriodicalId":201262,"journal":{"name":"ITHERM 2000. The Seventh Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (Cat. No.00CH37069)","volume":"82 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134268727","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 : 2000-05-23DOI: 10.1109/ITHERM.2000.866830
R.S. Li, S. E. Larson
Thermal transient analysis of an electronic packaging system is often cumbersome, even with today's sophisticated numerical software. This paper presents an efficient numerical approach to thermal transient analysis of an electronic packaging,system under electrical cyclic loading conditions. A numerical solution of temperature as function of time is formulated upon which a simple computer code is written to obtain transient behavior of a system or components. Based on the lumped capacitance (LC) model, a general average power concept is presented to obtain a steady state solution from finite element modeling (FEM). The steady state solution is then used to evaluate the time constant for analysis of transient heat transfer. The transient solutions from the proposed model and those obtained from FEA show good agreement at component level. Time to transient solution of a wire resistor only takes a couple of seconds via the proposed approach while it took four hours on HP735 for the first 120 cycles. The proposed approach is demonstrated through an example of an automotive control module PCB with resistors having cyclic current input. Thermal measurements from an IR scanner are also presented to correlate with analytical results.
{"title":"An approach to thermal analysis of PCB with components having cyclic electrical loading","authors":"R.S. Li, S. E. Larson","doi":"10.1109/ITHERM.2000.866830","DOIUrl":"https://doi.org/10.1109/ITHERM.2000.866830","url":null,"abstract":"Thermal transient analysis of an electronic packaging system is often cumbersome, even with today's sophisticated numerical software. This paper presents an efficient numerical approach to thermal transient analysis of an electronic packaging,system under electrical cyclic loading conditions. A numerical solution of temperature as function of time is formulated upon which a simple computer code is written to obtain transient behavior of a system or components. Based on the lumped capacitance (LC) model, a general average power concept is presented to obtain a steady state solution from finite element modeling (FEM). The steady state solution is then used to evaluate the time constant for analysis of transient heat transfer. The transient solutions from the proposed model and those obtained from FEA show good agreement at component level. Time to transient solution of a wire resistor only takes a couple of seconds via the proposed approach while it took four hours on HP735 for the first 120 cycles. The proposed approach is demonstrated through an example of an automotive control module PCB with resistors having cyclic current input. Thermal measurements from an IR scanner are also presented to correlate with analytical results.","PeriodicalId":201262,"journal":{"name":"ITHERM 2000. The Seventh Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (Cat. No.00CH37069)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130565690","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 : 2000-05-23DOI: 10.1109/ITHERM.2000.866832
J. Samson, F. Cutting
Power is a threefold problem for mobile electronic applications-generation, dissipation and junction temperature. Of the three, dissipation is the most limiting for spaceborne applications. Advances in high performance computing and high density packaging exacerbates the power dissipation problem and, hence, the junction temperature problem. In many space applications, particularly on smaller space vehicles, articulated space radiator systems with sealed coolant loops, pumps, etc. are neither practical nor available. Hence, the ultimate limitation is the ability to radiate heat to other sinks-primarily and ultimately to deep space. This paper considers the limitation of deep space as a heat sink for given vehicle parameters such as maximum operating temperatures, available radiating surface area, and emissivity. Different techniques of vehicle cooling are reviewed with a brief discussion of the pros and cons of each technique. Consideration of current and future material availability with better thermal and electrical conductivity is presented. Better thermal conductivity tends to isothermalize the radiating area, thereby increasing radiant heat transfer proportional to the fourth power of the absolute temperature. Increased electrical conductivity reduces power consumption and hence the need for heat dissipation. Such considerations are included in projections of self-dissipation capability per circuit board using advanced composite materials. The direct radiation approach is addressed, including a brief discussion of the conflict between the need for spacing for thermal considerations versus the desire to keep the length of signal paths as short as possible and elimination of the beneficial effects of the spacecraft and chassis shielding. A comparison of power and thermal constraints for a 10 GFLOPS onboard processing system is traded off against current and future material availability, power dissipation, radiation surface area available, and the projected performance density of candidate onboard processing architectures using COTS components.
{"title":"Thermal management for high performance computing in spaceborne applications","authors":"J. Samson, F. Cutting","doi":"10.1109/ITHERM.2000.866832","DOIUrl":"https://doi.org/10.1109/ITHERM.2000.866832","url":null,"abstract":"Power is a threefold problem for mobile electronic applications-generation, dissipation and junction temperature. Of the three, dissipation is the most limiting for spaceborne applications. Advances in high performance computing and high density packaging exacerbates the power dissipation problem and, hence, the junction temperature problem. In many space applications, particularly on smaller space vehicles, articulated space radiator systems with sealed coolant loops, pumps, etc. are neither practical nor available. Hence, the ultimate limitation is the ability to radiate heat to other sinks-primarily and ultimately to deep space. This paper considers the limitation of deep space as a heat sink for given vehicle parameters such as maximum operating temperatures, available radiating surface area, and emissivity. Different techniques of vehicle cooling are reviewed with a brief discussion of the pros and cons of each technique. Consideration of current and future material availability with better thermal and electrical conductivity is presented. Better thermal conductivity tends to isothermalize the radiating area, thereby increasing radiant heat transfer proportional to the fourth power of the absolute temperature. Increased electrical conductivity reduces power consumption and hence the need for heat dissipation. Such considerations are included in projections of self-dissipation capability per circuit board using advanced composite materials. The direct radiation approach is addressed, including a brief discussion of the conflict between the need for spacing for thermal considerations versus the desire to keep the length of signal paths as short as possible and elimination of the beneficial effects of the spacecraft and chassis shielding. A comparison of power and thermal constraints for a 10 GFLOPS onboard processing system is traded off against current and future material availability, power dissipation, radiation surface area available, and the projected performance density of candidate onboard processing architectures using COTS components.","PeriodicalId":201262,"journal":{"name":"ITHERM 2000. The Seventh Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (Cat. No.00CH37069)","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124939915","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 : 2000-05-23DOI: 10.1109/ITHERM.2000.866197
P. Zhou, K. Goodson
Thermomechanical diagnostic techniques are required for the characterization and reliability engineering of electronic packaging. Digital image/speckle correlation (DISC) is attractive for large throughput testing because it eliminates the specimen grating required by moire interferometry and does not require coherent illumination. Problems of DISC include a larger sensitivity to noise and a reduction of sensitivity for large fields of view. The present work uses DISC to study thermomechanical deformations of solder-joints in a cross-sectioned ball grid array (BGA) thermal test package. An iterative algorithm is developed to calculate the in-plane deformation and strain. Frame averaging of digital images reduces the noise, while a scanning stage allows a large effective field of view with acceptable sensitivity. This work achieves a spatial resolution of 2 /spl mu/m and a sensitivity of 0.01 pixels. Average strains in these solder joints are also calculated to provide data for fatigue lifetime estimation. The approach demonstrated here is promising for on-line thermomechanical diagnostics in IC manufacturing.
{"title":"Thermomechanical diagnostics of BGA packages using digital image/speckle correlation","authors":"P. Zhou, K. Goodson","doi":"10.1109/ITHERM.2000.866197","DOIUrl":"https://doi.org/10.1109/ITHERM.2000.866197","url":null,"abstract":"Thermomechanical diagnostic techniques are required for the characterization and reliability engineering of electronic packaging. Digital image/speckle correlation (DISC) is attractive for large throughput testing because it eliminates the specimen grating required by moire interferometry and does not require coherent illumination. Problems of DISC include a larger sensitivity to noise and a reduction of sensitivity for large fields of view. The present work uses DISC to study thermomechanical deformations of solder-joints in a cross-sectioned ball grid array (BGA) thermal test package. An iterative algorithm is developed to calculate the in-plane deformation and strain. Frame averaging of digital images reduces the noise, while a scanning stage allows a large effective field of view with acceptable sensitivity. This work achieves a spatial resolution of 2 /spl mu/m and a sensitivity of 0.01 pixels. Average strains in these solder joints are also calculated to provide data for fatigue lifetime estimation. The approach demonstrated here is promising for on-line thermomechanical diagnostics in IC manufacturing.","PeriodicalId":201262,"journal":{"name":"ITHERM 2000. The Seventh Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (Cat. No.00CH37069)","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130256813","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 : 2000-05-23DOI: 10.1109/ITHERM.2000.866821
K. Sikka, K. Torrance, C.U. Scholler, P.I. Salanova
Novel heat sinks with fluted and wavy fin configurations are designed and fabricated together with conventional longitudinal-plate and pin fin heat sinks. The experimental apparatus, consisting of the guard heater assembly, isolation chamber, wind tunnel and data acquisition instrumentation, is described. The thermal performance of the novel and conventional heat sinks is measured and compared for the horizontal and vertical base plate orientations under natural and low-velocity forced convection conditions. Results, presented as the Nusselt number against the Rayleigh or Reynolds numbers, reveal that the pin fin heat sink outperforms the other heat sinks. The novel heat sink designs do not yield significantly better thermal performance than the conventional heat sinks.
{"title":"Heat sinks with fluted and wavy fins in natural and low-velocity forced convection","authors":"K. Sikka, K. Torrance, C.U. Scholler, P.I. Salanova","doi":"10.1109/ITHERM.2000.866821","DOIUrl":"https://doi.org/10.1109/ITHERM.2000.866821","url":null,"abstract":"Novel heat sinks with fluted and wavy fin configurations are designed and fabricated together with conventional longitudinal-plate and pin fin heat sinks. The experimental apparatus, consisting of the guard heater assembly, isolation chamber, wind tunnel and data acquisition instrumentation, is described. The thermal performance of the novel and conventional heat sinks is measured and compared for the horizontal and vertical base plate orientations under natural and low-velocity forced convection conditions. Results, presented as the Nusselt number against the Rayleigh or Reynolds numbers, reveal that the pin fin heat sink outperforms the other heat sinks. The novel heat sink designs do not yield significantly better thermal performance than the conventional heat sinks.","PeriodicalId":201262,"journal":{"name":"ITHERM 2000. The Seventh Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (Cat. No.00CH37069)","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129087031","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 : 2000-05-23DOI: 10.1109/ITHERM.2000.866182
E. Yu, Deming Wang, Sura Kim, A. Przekwas
In this paper we present a new integrated thermo-electric-fluidic cooler (TEFC). This device is essentially composed of a low dimensional thermoelectric heat pump and a miniature fluidic loop in a highly integrated architecture. Heat removal is enhanced by micro-fin structures in the microchannels on the hot side of the thermoelectric device. Discussions are focused on the conceptual design of the TEFC and numerical models for the thermoelectric, and fluidic circuits. Simulation results on modeling of refrigeration loop are presented. Also different substrate materials are evaluated for improved heat spreading. Microchannels in both diamond and copper blocks are found to effectively remove heat and keep a more uniform temperature profile on the active surfaces than in CuW blocks. Fin configurations in the microchannels for enhancing liquid cooling are also evaluated. Preliminary results obtained for a TEFC device show great potentials for applications in cooling communication and mobile electronic systems.
{"title":"Active cooling of integrated circuits and optoelectronic devices using a micro configured thermoelectric and fluidic system","authors":"E. Yu, Deming Wang, Sura Kim, A. Przekwas","doi":"10.1109/ITHERM.2000.866182","DOIUrl":"https://doi.org/10.1109/ITHERM.2000.866182","url":null,"abstract":"In this paper we present a new integrated thermo-electric-fluidic cooler (TEFC). This device is essentially composed of a low dimensional thermoelectric heat pump and a miniature fluidic loop in a highly integrated architecture. Heat removal is enhanced by micro-fin structures in the microchannels on the hot side of the thermoelectric device. Discussions are focused on the conceptual design of the TEFC and numerical models for the thermoelectric, and fluidic circuits. Simulation results on modeling of refrigeration loop are presented. Also different substrate materials are evaluated for improved heat spreading. Microchannels in both diamond and copper blocks are found to effectively remove heat and keep a more uniform temperature profile on the active surfaces than in CuW blocks. Fin configurations in the microchannels for enhancing liquid cooling are also evaluated. Preliminary results obtained for a TEFC device show great potentials for applications in cooling communication and mobile electronic systems.","PeriodicalId":201262,"journal":{"name":"ITHERM 2000. The Seventh Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (Cat. No.00CH37069)","volume":"36 4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122508256","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 : 2000-05-23DOI: 10.1109/ITHERM.2000.866813
G. Refai-Ahmed, A. Radmehr, K. Kelkar
This paper presents an analysis of flow distribution in a new-generation power supply used in telecommunication applications. The power supply involves several boards, each containing several magnetic components, EMI screens, and heat sinks, arranged in a rack. The flow in each passage is driven by four suitably placed fans. The study utilizes the technique of Flow Network Modeling (FNM) for efficient prediction of the flow distribution in the power supply system. The novelty of the study lies in the use of a two-level flow network approach to achieve modularity and gain further efficiencies in the analysis of flow distribution. A flow network model of a passage formed by two successive boards is first constructed to determine the characteristics that describe the behavior of the flow in and out of an individual power supply. Two types of flow characteristics, namely resistive and pumping, are outlined and used for constructing these equivalent compact characteristics of the power supply. Network model for the overall system is then constructed by arranging the compact models for each passage in a manifold arrangement corresponding to the physical arrangement in the rack. Analysis is carried out for three placements of cabinets, namely a isolated cabinet, two cabinets side by side, and three or more cabinets side by side. Results of analysis show that for a single cabinet, the flow is uniformly distributed among the passages because of the presence of side vents. However, with multiple cabinets plated side-by-side, the forward flow streams from individual passages are forced to merge in the header passage at the back of the cabinet. The resulting combining manifold gives rise to a maldistribution of flow among the passages with lower flow rate in the bottom passages. The two-level network modeling approach outlined in this study is very efficient in terms of the time required for model definition, analysis, and examination of re-suits. The modularity of the approach is well suited for a top-down design and packaging of large scale electronics systems for achieving the desired thermal performance.
{"title":"Analysis of flow distribution in a power supply using flow network modeling (FNM)","authors":"G. Refai-Ahmed, A. Radmehr, K. Kelkar","doi":"10.1109/ITHERM.2000.866813","DOIUrl":"https://doi.org/10.1109/ITHERM.2000.866813","url":null,"abstract":"This paper presents an analysis of flow distribution in a new-generation power supply used in telecommunication applications. The power supply involves several boards, each containing several magnetic components, EMI screens, and heat sinks, arranged in a rack. The flow in each passage is driven by four suitably placed fans. The study utilizes the technique of Flow Network Modeling (FNM) for efficient prediction of the flow distribution in the power supply system. The novelty of the study lies in the use of a two-level flow network approach to achieve modularity and gain further efficiencies in the analysis of flow distribution. A flow network model of a passage formed by two successive boards is first constructed to determine the characteristics that describe the behavior of the flow in and out of an individual power supply. Two types of flow characteristics, namely resistive and pumping, are outlined and used for constructing these equivalent compact characteristics of the power supply. Network model for the overall system is then constructed by arranging the compact models for each passage in a manifold arrangement corresponding to the physical arrangement in the rack. Analysis is carried out for three placements of cabinets, namely a isolated cabinet, two cabinets side by side, and three or more cabinets side by side. Results of analysis show that for a single cabinet, the flow is uniformly distributed among the passages because of the presence of side vents. However, with multiple cabinets plated side-by-side, the forward flow streams from individual passages are forced to merge in the header passage at the back of the cabinet. The resulting combining manifold gives rise to a maldistribution of flow among the passages with lower flow rate in the bottom passages. The two-level network modeling approach outlined in this study is very efficient in terms of the time required for model definition, analysis, and examination of re-suits. The modularity of the approach is well suited for a top-down design and packaging of large scale electronics systems for achieving the desired thermal performance.","PeriodicalId":201262,"journal":{"name":"ITHERM 2000. The Seventh Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (Cat. No.00CH37069)","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131423797","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 : 2000-05-23DOI: 10.1109/ITHERM.2000.866170
Z. L. Yang, B. Palm, Ivan Kazachkov, B. Sehgal
In this paper, several different aspects of thermal dynamics of two-phase flow in a narrow channel have been addressed and analysed. According to the flow regime classification of two-phase flow in a narrow channel, only Taylor bubble flow and annular flow with thin liquid film are considered since they are of most interest for practical applications. The hydrodynamics of Taylor bubbles in a narrow channel is simulated by an advanced CFD method for two-phase flow - Lattice-Boltzmann method. The present numerical simulation provides reasonable pictures of Taylor bubble dynamics which agrees qualitatively well with analytical solutions and experimental observations. More importantly, the simulation results show that several vertices near the head and meniscus of the Taylor bubble appear. Experimental study is performed to study the condensation heat transfer inside a square channel. The experimental results show that significant enhancement of heat transfer is achieved in comparison with the predictions by Nusselt's correlation. This indicated clearly that the capillary force is playing an important role in redistribution of the film thickness inside the channel. An instability analysis is also performed to investigate the dynamics of the thin film flow in a narrow channel. The analytical solution for a narrow gap channel shows that there is no growing wave on the film surface from perturbation, all the kinematic waves coming from perturbations on the film surface are convoyed by vapor flow without growing or decreasing since the liquid film is too thin. The wave structure of the interface of two-phase flow could enhance significantly the heat transfer between the liquid film and heated wall.
{"title":"On mechanism of enhancement of two-phase flow heat transfer in a narrow channel","authors":"Z. L. Yang, B. Palm, Ivan Kazachkov, B. Sehgal","doi":"10.1109/ITHERM.2000.866170","DOIUrl":"https://doi.org/10.1109/ITHERM.2000.866170","url":null,"abstract":"In this paper, several different aspects of thermal dynamics of two-phase flow in a narrow channel have been addressed and analysed. According to the flow regime classification of two-phase flow in a narrow channel, only Taylor bubble flow and annular flow with thin liquid film are considered since they are of most interest for practical applications. The hydrodynamics of Taylor bubbles in a narrow channel is simulated by an advanced CFD method for two-phase flow - Lattice-Boltzmann method. The present numerical simulation provides reasonable pictures of Taylor bubble dynamics which agrees qualitatively well with analytical solutions and experimental observations. More importantly, the simulation results show that several vertices near the head and meniscus of the Taylor bubble appear. Experimental study is performed to study the condensation heat transfer inside a square channel. The experimental results show that significant enhancement of heat transfer is achieved in comparison with the predictions by Nusselt's correlation. This indicated clearly that the capillary force is playing an important role in redistribution of the film thickness inside the channel. An instability analysis is also performed to investigate the dynamics of the thin film flow in a narrow channel. The analytical solution for a narrow gap channel shows that there is no growing wave on the film surface from perturbation, all the kinematic waves coming from perturbations on the film surface are convoyed by vapor flow without growing or decreasing since the liquid film is too thin. The wave structure of the interface of two-phase flow could enhance significantly the heat transfer between the liquid film and heated wall.","PeriodicalId":201262,"journal":{"name":"ITHERM 2000. The Seventh Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (Cat. No.00CH37069)","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128447167","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 : 2000-05-23DOI: 10.1109/ITHERM.2000.866849
D. Kulkarni, G. Subbarayan
The dynamic motion of a solder droplet during assembly is a complex, unsteady, free surface problem involving surface tension and viscous effects. The motion of the droplet is coupled with the motion of the component or chip to be assembled and involves dynamic contact lines. A methodology based on a Non-Uniform Rational B-Spline (NURBS) discretization has been developed for the dynamic analysis of the droplet motion. A surface energy based formulation has been developed to incorporate the surface tension effects. The developed methodology leads to an updated Lagrangian scheme with a Galerkin in space and least square in time formulation. The Non-Uniform Rational B-Spline (NURBS) representation used, for the spatial discretization enables the method to handle problems involving complex droplet geometries. The ability of the NURBS representation to provide both global and local control, along with the least square method used in this methodology, enables us to develop an unconditionally stable time integration scheme which can be optimized to achieve desired accuracy and numerical dissipation efficiently. A sample problem of droplet shape evolution has been solved to demonstrate the path prediction capability of the proposed methodology. In future, the method can be applied to solve various real world dynamic motion problems associated with droplets.
{"title":"A dynamic model for predicting the motion of solder droplets during assembly","authors":"D. Kulkarni, G. Subbarayan","doi":"10.1109/ITHERM.2000.866849","DOIUrl":"https://doi.org/10.1109/ITHERM.2000.866849","url":null,"abstract":"The dynamic motion of a solder droplet during assembly is a complex, unsteady, free surface problem involving surface tension and viscous effects. The motion of the droplet is coupled with the motion of the component or chip to be assembled and involves dynamic contact lines. A methodology based on a Non-Uniform Rational B-Spline (NURBS) discretization has been developed for the dynamic analysis of the droplet motion. A surface energy based formulation has been developed to incorporate the surface tension effects. The developed methodology leads to an updated Lagrangian scheme with a Galerkin in space and least square in time formulation. The Non-Uniform Rational B-Spline (NURBS) representation used, for the spatial discretization enables the method to handle problems involving complex droplet geometries. The ability of the NURBS representation to provide both global and local control, along with the least square method used in this methodology, enables us to develop an unconditionally stable time integration scheme which can be optimized to achieve desired accuracy and numerical dissipation efficiently. A sample problem of droplet shape evolution has been solved to demonstrate the path prediction capability of the proposed methodology. In future, the method can be applied to solve various real world dynamic motion problems associated with droplets.","PeriodicalId":201262,"journal":{"name":"ITHERM 2000. The Seventh Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (Cat. No.00CH37069)","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131741458","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 : 2000-05-23DOI: 10.1109/ITHERM.2000.866823
S. Narasimhan, A. Mira
The modeling of heat sinks was carried out by using the electronics cooling software for natural convection scenarios in vertical configurations. Simulations were carried out using the electronics cooling CFD software on both actual and compact heat sink models to evaluate the thermal efficiency of the heat sink. The effective thermal conductivity of the compact heat sink was calculated using Nusselt number correlation for free convection on a vertical plate. Due to the complex nature of the Nusselt number correlation for free convection on a vertical plate, an iterative solution was used in order to solve for the effective conductivity of the compact heat sink. The use of compact heat sink models helps to reduce the cost of computing time and resources. The compact modeling technique was first applied to both extruded and pin fin heat sinks to validate the methodology in laminar natural convection scenarios. After validating the methodology in laminar natural convection scenarios, it was applied to a system level model consisting of a set of pin fin heat sinks placed on a row of components. It was found that the compact heat sink technique results in significant savings in mesh size and computing time and also gives good accuracy when compared with the results from the detailed heat sink models.
{"title":"Characterization of compact heat sink models in natural convection","authors":"S. Narasimhan, A. Mira","doi":"10.1109/ITHERM.2000.866823","DOIUrl":"https://doi.org/10.1109/ITHERM.2000.866823","url":null,"abstract":"The modeling of heat sinks was carried out by using the electronics cooling software for natural convection scenarios in vertical configurations. Simulations were carried out using the electronics cooling CFD software on both actual and compact heat sink models to evaluate the thermal efficiency of the heat sink. The effective thermal conductivity of the compact heat sink was calculated using Nusselt number correlation for free convection on a vertical plate. Due to the complex nature of the Nusselt number correlation for free convection on a vertical plate, an iterative solution was used in order to solve for the effective conductivity of the compact heat sink. The use of compact heat sink models helps to reduce the cost of computing time and resources. The compact modeling technique was first applied to both extruded and pin fin heat sinks to validate the methodology in laminar natural convection scenarios. After validating the methodology in laminar natural convection scenarios, it was applied to a system level model consisting of a set of pin fin heat sinks placed on a row of components. It was found that the compact heat sink technique results in significant savings in mesh size and computing time and also gives good accuracy when compared with the results from the detailed heat sink models.","PeriodicalId":201262,"journal":{"name":"ITHERM 2000. The Seventh Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (Cat. No.00CH37069)","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131168760","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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