— Improving mixing is an effective means to enhance single- and two-phase heat transfer in microc... more — Improving mixing is an effective means to enhance single- and two-phase heat transfer in microchannels. However, it is challenging to induce since the flow in microchannels is laminar in the most working conditions. We report that heat transfer rate and critical heat flux (CHF) on 1-methoxyheptafluoropropane (HFE-7000) can be significantly enhanced by patterning embed-ded micromixers on the bottom walls in a parallel silicon microchannel array, which consists of five parallel channels (height, width, length: 250 µm × 220 µm × 10 mm). Compared with a plain-wall microchannel array at a mass flux range of 1018 to 2206 kg/m2 · s and a heat flux range of 10 to 198 W/cm2, single-phase heat transfer rate, two-phase heat transfer rate, and CHF are enhanced up to 221%, 160%, and 61 % using microscale staggered herringbone mixers in microchannels, respectively. These mixers consist of 7 or 3.5 Hz with 12 staggered herringbone grooves (50 µm in depth and width) with 90 ° between two asym-met...
Improving mixing is an effective method to enhance flow boiling in microchannels. However, it is ... more Improving mixing is an effective method to enhance flow boiling in microchannels. However, it is challenging to induce since the flow in microchannels is laminar under typical operating conditions. We report that flow boiling of 1-methoxyheptafluoropropane (HFE 7000) in a parallel microchannel array was significantly enhanced by chaotic mixers patterned on the bottom walls. The microchannel array consists of five parallel channels (height, width, length: 250 μm × 220 μm × 10 mm). The chaotic mixers consist of seven cycles with 12 staggered herringbone grooves (50 μm depth and width with 90° between two asymmetric arms) in each cycle. Its asymmetry is defined by the off center position of the apex of the herringbone groove. Compared with a smooth-wall microchannel array with identical channel dimensions, heat transfer coefficient and critical heat flux of flow boiling on HFE 7000 were enhanced up to 45 % and 61 % using chaotic mixer pairs in microchannels. Mass fluxes range from 1000...
High performance miniaturized electronic devices require enhanced, compact and reliable thermal m... more High performance miniaturized electronic devices require enhanced, compact and reliable thermal management system. As an efficient compact space cooling technique, flow boiling in microchannels has recently gained wide acceptance. However, weak buoyancy effects and microgravity in avionics and numerous space systems operations hinder the performance of flow boiling microchannel thermal management system due to poor bubble departure capacity and unfavorable development of flow regimes. Here we report the flow boiling silicon nanowires (SiNWs) microchannels which can favorably regulate two-phase flow regimes by enhancing explosive boiling, minimizing bubble departure diameter, and smoothing flow regime transition. Extensive experimental investigations along with high speed visualizations are performed. The experiments are performed with the dielectric fluid HFE-7100 in a forced convection loop for wide range of heat and mass fluxes. High speed flow visualizations have been employed at...
The application of embedded radial expanding micro-channels with micro-pin fields for two phase c... more The application of embedded radial expanding micro-channels with micro-pin fields for two phase cooling of semiconductor dies has been successfully demonstrated. Thermal data has shown effective two-phase cooling at power densities in excess of those achieved using conventional embedded parallel channel structures with similar base dimensions. An understanding of some of the basis for this improved thermal performance can be gained through detailed examination of the flow boiling characteristics in radial expanding micro-channels with micro-pin fields utilizing high speed, high resolution visualization techniques. In this work, a thermal test vehicle design incorporating manifold and thermal silicon dies as previously reported was modified to provide an optical viewing port for flow visualization. The modifications included replacing the silicon manifold die with a glass manifold die. This die was bonded to the thermal silicon die using a thin film thermoplastic rather than the sold...
Interlayer cooling utilizing pumped two-phase flow of a chip-to-chip interconnect-compatible diel... more Interlayer cooling utilizing pumped two-phase flow of a chip-to-chip interconnect-compatible dielectric fluid is an enabling technology for future high power 3D (three-dimensional) chip stacks. Development of this approach requires high fidelity and computationally manageable conjugate thermal models. In this paper, a conjugate heat transfer model developed for simulating two-phase flow boiling through chip embedded micron-scale channels is described. This model uses a novel hybrid approach where governing equations for flow-field and convection in the single-phase flow regions (e.g. inlet plenum) as well as that for heat conduction in solids is solved in detail (i.e., full-physics) while in the two-phase flow regions (e.g. micro-channels), a reduced-physics approach is used. Extensive model validation using data from several experiments was performed to quantify the accuracy of this model under different operating conditions.
Controlling the movement of liquids/vapors on solid interfaces is of importance for numerous appl... more Controlling the movement of liquids/vapors on solid interfaces is of importance for numerous applications ranging from fluid processing to lab-on-chip and thermal management systems. In this study, a new mechanism is proposed to coordinate the two-phase transport during a boiling process in a highly on-demand fashion. A novel wicking nanofence was designed to confine liquids as an ordered, reconfigurable boundary layer that allows for significant enhancements in all aspects of two-phase transport performances. Experiments have been conducted to systematically investigate the effect of a nanofence-activated boundary layer on the flow boiling performance for mass velocity ranging from 113 to 389 kg/m2·s. Significant enhancements regarding the heat transfer coefficient (HTC) and critical heat flux (CHF) have been demonstrated. For example, a CHF value of 585 W/cm2 with an enhancement of about threefold is achieved compared to a plain-wall microchannel at a mass velocity of 389 kg/m2·s. The HTC enhancement is up to 58% as well at a mass velocity of 160 kg/m2·s. All these achievements are demonstrated without escalating the pressure drops.
2016 IEEE 66th Electronic Components and Technology Conference (ECTC), 2016
This paper reports on the integration and packaging of embedded radial micro-channels for 3D chip... more This paper reports on the integration and packaging of embedded radial micro-channels for 3D chip cooling. A thermal demonstration vehicle (TDV) has been designed, fabricated and assembled. Radial micro-channels based on deep Si etching was integrated with a manifold chip to form a 2-layer chip stack, which has been assembled using a ceramic substrate and a Cu manifold. A test vehicle with an effective critical heat flux of 340 W/cm2 and uniform cooling has been successfully demonstrated using a dielectric coolant (R1234ze).
2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm), 2016
Thermal challenges in 3D ICs have driven the need for embedded chip cooling. In this paper, we me... more Thermal challenges in 3D ICs have driven the need for embedded chip cooling. In this paper, we measured the thermal performance of a two-phase system employing flow boiling in chip-embedded micro-channels utilizing the latent heat of vaporization of dielectric refrigerants (such as R-1234ze) In the present study, an investigation was performed on a 20 mm × 20 mm thermal test vehicle having a heater layer to simulate the heat generation from a state-of-the-art 8-core microprocessor chip and a sensor layer to measure temperature at key locations within the test vehicle. Fluidic channels in the form of radial expanding micro-scale cavities with micro-pin fields were etched into the test vehicle. The micro-pin fields represent the through-silicon-via (TSV) interconnects present in multi-die stacks. The heaters are used to simulate a background heat flux of 20 W/cm2 and individual core heat fluxes of up to 210 W/cm2. This heat generation capability corresponds anywhere from a processor low-power idle mode to a high-power super-turbo mode and beyond. Since the flow resistance in a microchannel for two-phase cooling depends on in-situ heat generation, asymmetric power dissipation due to different power levels in various cores and non-core areas may unbalance the overall flow distribution. Furthermore, it may reduce the local heat transfer rate and even lead to premature failure of working cores. This study aims at understanding the effects of asymmetric heat flux profiles on flow resistance and boiling heat transfer.
Thermal performance for embedded two-phase cooling using dielectric coolant (R1234ze) is evaluate... more Thermal performance for embedded two-phase cooling using dielectric coolant (R1234ze) is evaluated on a ∼20 mm × 20 mm large die. The test vehicles incorporate radial expanding channels with embedded pin fields suitable for through-silicon-via (TSV) interconnects of multidie stacks. Power generating features mimicking those anticipated in future generations of processor chips with eight cores are included. Initial results show that for the types of power maps anticipated, critical heat fluxes (CHFs) in “core” areas of at least 350 W/cm2 with at least 20 W/cm2 “background” heating in rest of the chip area can be achieved with less than 30 °C temperature rise over the inlet coolant temperature. These heat fluxes are significantly higher than those seen for relatively long parallel channel devices of similar base channel dimensions. Experimental results of flow rate, pressure drop, “device,” and coolant temperature are also provided for these test vehicles along with details of the tes...
2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm), 2016
The development of embedded chip cooling for 2D and 3D integrated circuits using pumped dielectri... more The development of embedded chip cooling for 2D and 3D integrated circuits using pumped dielectric refrigerant has gained recent attention due to the ability to manage high heat densities and compatibility with electronics. Recent studies have focused on in-situ thermal and hydrodynamic phenomena (e.g. boiling and bubble dynamics) of two-phase flow boiling at micro-scales. In this paper we focus on the two-phase cooling system design including the cooling capability, size and coefficient of performance (COP). In implementing a two-phase cooling, a system-level computational model for two-phase cooling systems becomes necessary. Therefore, a computationally manageable and accurate one dimensional (1D) system model is described. Furthermore, the model can be easily customized for different two-phase cooling system configurations. By validating the model with experimental data from a two-phase cooling system, it is shown that model can generate accurate results, and therefore, can be used as a tool to study and predict the characteristics and performance of a pumped two-phase cooling systems.
Volume 1: Micro/Nanofluidics and Lab-on-a-Chip; Nanofluids; Micro/Nanoscale Interfacial Transport Phenomena; Micro/Nanoscale Boiling and Condensation Heat Transfer; Micro/Nanoscale Thermal Radiation; Micro/Nanoscale Energy Devices and Systems, 2016
Flow boiling in Silicon Nanowire microchannel enhances heat transfer performance, CHF and reduces... more Flow boiling in Silicon Nanowire microchannel enhances heat transfer performance, CHF and reduces pressure drop compared to Plainwall microchannel. It is revealed by earlier studies that promoted nucleate boiling, liquid rewetting and enhanced thin film evaporation are the primary reasons behind these significant performance enchantments. Although flow regime plays a significant role to characterize the flow boiling Silicon Nanowire microchannel performances; surface characteristics, hydrodynamic phenomena, bubble contact angle and surface orientation are also some of the major influencing parameters in system performances. More importantly, effect of orientation (effect of gravity) draws a great attention in establishing the viability of flow boiling in microchannels in space applications. In this study, the effects of heating surface orientation in flow boiling Silicon Nanowire microchannels have been investigated to reveal the underlying heat transfer phenomena and also to discov...
Volume 1: Micro/Nanofluidics and Lab-on-a-Chip; Nanofluids; Micro/Nanoscale Interfacial Transport Phenomena; Micro/Nanoscale Boiling and Condensation Heat Transfer; Micro/Nanoscale Thermal Radiation; Micro/Nanoscale Energy Devices and Systems, 2016
Volume 1: Micro/Nanofluidics and Lab-on-a-Chip; Nanofluids; Micro/Nanoscale Interfacial Transport Phenomena; Micro/Nanoscale Boiling and Condensation Heat Transfer; Micro/Nanoscale Thermal Radiation; Micro/Nanoscale Energy Devices and Systems, 2016
Volume 2: Advanced Electronics and Photonics, Packaging Materials and Processing; Advanced Electronics and Photonics: Packaging, Interconnect and Reliability; Fundamentals of Thermal and Fluid Transport in Nano, Micro, and Mini Scales, 2015
Two-phase microchannel heat sink is promising in cooling high power electronics with dielectric f... more Two-phase microchannel heat sink is promising in cooling high power electronics with dielectric fluids. Compared to water, dielectric fluids can assure system safety in case of working fluid leakage. However, two-phase heat transfer of these hydrofluorocarbon refrigerants is restricted by their relatively low thermal conductivities and low latent heats. Numerous nanoscale/submicron structures have been developed to enhance the single and two-phase heat transfer in microchannels; but these techniques usually require nanoparticle seeds in multi-step wet processes or nanolithography to integrate these nanostructures. Therefore, most of these techniques were time-consuming and costly. In this study, we present a plasma etching method using a modified Bosch process to create silicon tips with nanoscale scallops in microchannels. This is a rapid and cost-effective method to integrate large density of nucleation sites without involving nanolithography method or using nanoparticle seeds. Th...
Volume 3: Advanced Fabrication and Manufacturing; Emerging Technology Frontiers; Energy, Health and Water- Applications of Nano-, Micro- and Mini-Scale Devices; MEMS and NEMS; Technology Update Talks; Thermal Management Using Micro Channels, Jets, Sprays, 2015
Thermal performance for embedded two phase cooling using dielectric coolant (R1234ze) is evaluate... more Thermal performance for embedded two phase cooling using dielectric coolant (R1234ze) is evaluated on a ∼20 mm × 20 mm large die. The test vehicles incorporate radial expanding channels with embedded pin fields suitable for through-silicon-via (TSV) interconnects of multi-die stacks. Power generating features mimicking those anticipated in future generations of processor chips with 8 cores are included. Initial results show that for the types of power maps anticipated, critical heat fluxes in “core” areas of at least 350 W/cm2 with at least 20 W/cm2 “background” heating in rest of the chip area can be achieved with less than 30 °C temperature rise over the inlet coolant temperature. These heat fluxes are significantly higher than those seen for relatively long parallel channel devices of similar base channel dimensions. Experimental results of flow rate, pressure drop, “device,” and coolant temperature are also provided for these test vehicles along with details of the test facility...
— Improving mixing is an effective means to enhance single- and two-phase heat transfer in microc... more — Improving mixing is an effective means to enhance single- and two-phase heat transfer in microchannels. However, it is challenging to induce since the flow in microchannels is laminar in the most working conditions. We report that heat transfer rate and critical heat flux (CHF) on 1-methoxyheptafluoropropane (HFE-7000) can be significantly enhanced by patterning embed-ded micromixers on the bottom walls in a parallel silicon microchannel array, which consists of five parallel channels (height, width, length: 250 µm × 220 µm × 10 mm). Compared with a plain-wall microchannel array at a mass flux range of 1018 to 2206 kg/m2 · s and a heat flux range of 10 to 198 W/cm2, single-phase heat transfer rate, two-phase heat transfer rate, and CHF are enhanced up to 221%, 160%, and 61 % using microscale staggered herringbone mixers in microchannels, respectively. These mixers consist of 7 or 3.5 Hz with 12 staggered herringbone grooves (50 µm in depth and width) with 90 ° between two asym-met...
Improving mixing is an effective method to enhance flow boiling in microchannels. However, it is ... more Improving mixing is an effective method to enhance flow boiling in microchannels. However, it is challenging to induce since the flow in microchannels is laminar under typical operating conditions. We report that flow boiling of 1-methoxyheptafluoropropane (HFE 7000) in a parallel microchannel array was significantly enhanced by chaotic mixers patterned on the bottom walls. The microchannel array consists of five parallel channels (height, width, length: 250 μm × 220 μm × 10 mm). The chaotic mixers consist of seven cycles with 12 staggered herringbone grooves (50 μm depth and width with 90° between two asymmetric arms) in each cycle. Its asymmetry is defined by the off center position of the apex of the herringbone groove. Compared with a smooth-wall microchannel array with identical channel dimensions, heat transfer coefficient and critical heat flux of flow boiling on HFE 7000 were enhanced up to 45 % and 61 % using chaotic mixer pairs in microchannels. Mass fluxes range from 1000...
High performance miniaturized electronic devices require enhanced, compact and reliable thermal m... more High performance miniaturized electronic devices require enhanced, compact and reliable thermal management system. As an efficient compact space cooling technique, flow boiling in microchannels has recently gained wide acceptance. However, weak buoyancy effects and microgravity in avionics and numerous space systems operations hinder the performance of flow boiling microchannel thermal management system due to poor bubble departure capacity and unfavorable development of flow regimes. Here we report the flow boiling silicon nanowires (SiNWs) microchannels which can favorably regulate two-phase flow regimes by enhancing explosive boiling, minimizing bubble departure diameter, and smoothing flow regime transition. Extensive experimental investigations along with high speed visualizations are performed. The experiments are performed with the dielectric fluid HFE-7100 in a forced convection loop for wide range of heat and mass fluxes. High speed flow visualizations have been employed at...
The application of embedded radial expanding micro-channels with micro-pin fields for two phase c... more The application of embedded radial expanding micro-channels with micro-pin fields for two phase cooling of semiconductor dies has been successfully demonstrated. Thermal data has shown effective two-phase cooling at power densities in excess of those achieved using conventional embedded parallel channel structures with similar base dimensions. An understanding of some of the basis for this improved thermal performance can be gained through detailed examination of the flow boiling characteristics in radial expanding micro-channels with micro-pin fields utilizing high speed, high resolution visualization techniques. In this work, a thermal test vehicle design incorporating manifold and thermal silicon dies as previously reported was modified to provide an optical viewing port for flow visualization. The modifications included replacing the silicon manifold die with a glass manifold die. This die was bonded to the thermal silicon die using a thin film thermoplastic rather than the sold...
Interlayer cooling utilizing pumped two-phase flow of a chip-to-chip interconnect-compatible diel... more Interlayer cooling utilizing pumped two-phase flow of a chip-to-chip interconnect-compatible dielectric fluid is an enabling technology for future high power 3D (three-dimensional) chip stacks. Development of this approach requires high fidelity and computationally manageable conjugate thermal models. In this paper, a conjugate heat transfer model developed for simulating two-phase flow boiling through chip embedded micron-scale channels is described. This model uses a novel hybrid approach where governing equations for flow-field and convection in the single-phase flow regions (e.g. inlet plenum) as well as that for heat conduction in solids is solved in detail (i.e., full-physics) while in the two-phase flow regions (e.g. micro-channels), a reduced-physics approach is used. Extensive model validation using data from several experiments was performed to quantify the accuracy of this model under different operating conditions.
Controlling the movement of liquids/vapors on solid interfaces is of importance for numerous appl... more Controlling the movement of liquids/vapors on solid interfaces is of importance for numerous applications ranging from fluid processing to lab-on-chip and thermal management systems. In this study, a new mechanism is proposed to coordinate the two-phase transport during a boiling process in a highly on-demand fashion. A novel wicking nanofence was designed to confine liquids as an ordered, reconfigurable boundary layer that allows for significant enhancements in all aspects of two-phase transport performances. Experiments have been conducted to systematically investigate the effect of a nanofence-activated boundary layer on the flow boiling performance for mass velocity ranging from 113 to 389 kg/m2·s. Significant enhancements regarding the heat transfer coefficient (HTC) and critical heat flux (CHF) have been demonstrated. For example, a CHF value of 585 W/cm2 with an enhancement of about threefold is achieved compared to a plain-wall microchannel at a mass velocity of 389 kg/m2·s. The HTC enhancement is up to 58% as well at a mass velocity of 160 kg/m2·s. All these achievements are demonstrated without escalating the pressure drops.
2016 IEEE 66th Electronic Components and Technology Conference (ECTC), 2016
This paper reports on the integration and packaging of embedded radial micro-channels for 3D chip... more This paper reports on the integration and packaging of embedded radial micro-channels for 3D chip cooling. A thermal demonstration vehicle (TDV) has been designed, fabricated and assembled. Radial micro-channels based on deep Si etching was integrated with a manifold chip to form a 2-layer chip stack, which has been assembled using a ceramic substrate and a Cu manifold. A test vehicle with an effective critical heat flux of 340 W/cm2 and uniform cooling has been successfully demonstrated using a dielectric coolant (R1234ze).
2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm), 2016
Thermal challenges in 3D ICs have driven the need for embedded chip cooling. In this paper, we me... more Thermal challenges in 3D ICs have driven the need for embedded chip cooling. In this paper, we measured the thermal performance of a two-phase system employing flow boiling in chip-embedded micro-channels utilizing the latent heat of vaporization of dielectric refrigerants (such as R-1234ze) In the present study, an investigation was performed on a 20 mm × 20 mm thermal test vehicle having a heater layer to simulate the heat generation from a state-of-the-art 8-core microprocessor chip and a sensor layer to measure temperature at key locations within the test vehicle. Fluidic channels in the form of radial expanding micro-scale cavities with micro-pin fields were etched into the test vehicle. The micro-pin fields represent the through-silicon-via (TSV) interconnects present in multi-die stacks. The heaters are used to simulate a background heat flux of 20 W/cm2 and individual core heat fluxes of up to 210 W/cm2. This heat generation capability corresponds anywhere from a processor low-power idle mode to a high-power super-turbo mode and beyond. Since the flow resistance in a microchannel for two-phase cooling depends on in-situ heat generation, asymmetric power dissipation due to different power levels in various cores and non-core areas may unbalance the overall flow distribution. Furthermore, it may reduce the local heat transfer rate and even lead to premature failure of working cores. This study aims at understanding the effects of asymmetric heat flux profiles on flow resistance and boiling heat transfer.
Thermal performance for embedded two-phase cooling using dielectric coolant (R1234ze) is evaluate... more Thermal performance for embedded two-phase cooling using dielectric coolant (R1234ze) is evaluated on a ∼20 mm × 20 mm large die. The test vehicles incorporate radial expanding channels with embedded pin fields suitable for through-silicon-via (TSV) interconnects of multidie stacks. Power generating features mimicking those anticipated in future generations of processor chips with eight cores are included. Initial results show that for the types of power maps anticipated, critical heat fluxes (CHFs) in “core” areas of at least 350 W/cm2 with at least 20 W/cm2 “background” heating in rest of the chip area can be achieved with less than 30 °C temperature rise over the inlet coolant temperature. These heat fluxes are significantly higher than those seen for relatively long parallel channel devices of similar base channel dimensions. Experimental results of flow rate, pressure drop, “device,” and coolant temperature are also provided for these test vehicles along with details of the tes...
2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm), 2016
The development of embedded chip cooling for 2D and 3D integrated circuits using pumped dielectri... more The development of embedded chip cooling for 2D and 3D integrated circuits using pumped dielectric refrigerant has gained recent attention due to the ability to manage high heat densities and compatibility with electronics. Recent studies have focused on in-situ thermal and hydrodynamic phenomena (e.g. boiling and bubble dynamics) of two-phase flow boiling at micro-scales. In this paper we focus on the two-phase cooling system design including the cooling capability, size and coefficient of performance (COP). In implementing a two-phase cooling, a system-level computational model for two-phase cooling systems becomes necessary. Therefore, a computationally manageable and accurate one dimensional (1D) system model is described. Furthermore, the model can be easily customized for different two-phase cooling system configurations. By validating the model with experimental data from a two-phase cooling system, it is shown that model can generate accurate results, and therefore, can be used as a tool to study and predict the characteristics and performance of a pumped two-phase cooling systems.
Volume 1: Micro/Nanofluidics and Lab-on-a-Chip; Nanofluids; Micro/Nanoscale Interfacial Transport Phenomena; Micro/Nanoscale Boiling and Condensation Heat Transfer; Micro/Nanoscale Thermal Radiation; Micro/Nanoscale Energy Devices and Systems, 2016
Flow boiling in Silicon Nanowire microchannel enhances heat transfer performance, CHF and reduces... more Flow boiling in Silicon Nanowire microchannel enhances heat transfer performance, CHF and reduces pressure drop compared to Plainwall microchannel. It is revealed by earlier studies that promoted nucleate boiling, liquid rewetting and enhanced thin film evaporation are the primary reasons behind these significant performance enchantments. Although flow regime plays a significant role to characterize the flow boiling Silicon Nanowire microchannel performances; surface characteristics, hydrodynamic phenomena, bubble contact angle and surface orientation are also some of the major influencing parameters in system performances. More importantly, effect of orientation (effect of gravity) draws a great attention in establishing the viability of flow boiling in microchannels in space applications. In this study, the effects of heating surface orientation in flow boiling Silicon Nanowire microchannels have been investigated to reveal the underlying heat transfer phenomena and also to discov...
Volume 1: Micro/Nanofluidics and Lab-on-a-Chip; Nanofluids; Micro/Nanoscale Interfacial Transport Phenomena; Micro/Nanoscale Boiling and Condensation Heat Transfer; Micro/Nanoscale Thermal Radiation; Micro/Nanoscale Energy Devices and Systems, 2016
Volume 1: Micro/Nanofluidics and Lab-on-a-Chip; Nanofluids; Micro/Nanoscale Interfacial Transport Phenomena; Micro/Nanoscale Boiling and Condensation Heat Transfer; Micro/Nanoscale Thermal Radiation; Micro/Nanoscale Energy Devices and Systems, 2016
Volume 2: Advanced Electronics and Photonics, Packaging Materials and Processing; Advanced Electronics and Photonics: Packaging, Interconnect and Reliability; Fundamentals of Thermal and Fluid Transport in Nano, Micro, and Mini Scales, 2015
Two-phase microchannel heat sink is promising in cooling high power electronics with dielectric f... more Two-phase microchannel heat sink is promising in cooling high power electronics with dielectric fluids. Compared to water, dielectric fluids can assure system safety in case of working fluid leakage. However, two-phase heat transfer of these hydrofluorocarbon refrigerants is restricted by their relatively low thermal conductivities and low latent heats. Numerous nanoscale/submicron structures have been developed to enhance the single and two-phase heat transfer in microchannels; but these techniques usually require nanoparticle seeds in multi-step wet processes or nanolithography to integrate these nanostructures. Therefore, most of these techniques were time-consuming and costly. In this study, we present a plasma etching method using a modified Bosch process to create silicon tips with nanoscale scallops in microchannels. This is a rapid and cost-effective method to integrate large density of nucleation sites without involving nanolithography method or using nanoparticle seeds. Th...
Volume 3: Advanced Fabrication and Manufacturing; Emerging Technology Frontiers; Energy, Health and Water- Applications of Nano-, Micro- and Mini-Scale Devices; MEMS and NEMS; Technology Update Talks; Thermal Management Using Micro Channels, Jets, Sprays, 2015
Thermal performance for embedded two phase cooling using dielectric coolant (R1234ze) is evaluate... more Thermal performance for embedded two phase cooling using dielectric coolant (R1234ze) is evaluated on a ∼20 mm × 20 mm large die. The test vehicles incorporate radial expanding channels with embedded pin fields suitable for through-silicon-via (TSV) interconnects of multi-die stacks. Power generating features mimicking those anticipated in future generations of processor chips with 8 cores are included. Initial results show that for the types of power maps anticipated, critical heat fluxes in “core” areas of at least 350 W/cm2 with at least 20 W/cm2 “background” heating in rest of the chip area can be achieved with less than 30 °C temperature rise over the inlet coolant temperature. These heat fluxes are significantly higher than those seen for relatively long parallel channel devices of similar base channel dimensions. Experimental results of flow rate, pressure drop, “device,” and coolant temperature are also provided for these test vehicles along with details of the test facility...
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