Thermal Performance and Key Challenges for Future CPU Cooling Technologies

2005 ◽  
Author(s):  
Ioan Sauciuc ◽  
Ravi Prasher ◽  
Je-Young Chang ◽  
Hakan Erturk ◽  
Gregory Chrysler ◽  
...  
Keyword(s):  
Power Density ◽  
Thermal Performance ◽  
Hot Spot ◽  
Average Power ◽  
Building Blocks ◽  
Thermal Design ◽  
Air Cooling ◽  
Back Side ◽  
Two Phase ◽  
Density Factor

Over the past few years, thermal design for cooling microprocessors has become increasingly challenging mainly because of an increase in both average power density and local power density, commonly referred to as “hot spots”. The current air cooling technologies present diminishing returns, thus it is strategically important for the microelectronics industry to establish the research and development focus for future non air-cooling technologies. This paper presents the thermal performance capability for enabling and package based cooling technologies using a range of “reasonable” boundary conditions. In the enabling area a few key main building blocks are considered: air cooling, high conductivity materials, liquid cooling (single and two-phase), thermoelectric modules integrated with heat pipes/vapor chambers, refrigeration based devices and the thermal interface materials performance. For package based technologies we present only the microchannel building block (cold plate in contact with the back-side of the die). It will be shown that as the hot spot density factor increases, package based cooling technologies should be considered for more significant cooling improvements. In addition to thermal performance, a summary of the key technical challenges are presented in the paper.   This paper was also originally published as part of the Proceedings of the ASME 2005 Heat Transfer Summer Conference.

Thermal Design Analysis of 2.5-D Packages With Analytical TSV Submodels

2015 ◽  
Author(s):  
H. Y. Zhang ◽  
Xiao Yan ◽  
W. H. Zhu ◽  
Leon Lin
Keyword(s):  
Thermal Performance ◽  
Heat Sink ◽  
Power Dissipation ◽  
High Current Density ◽  
Hot Spot ◽  
Thermal Design ◽  
Good Prediction ◽  
Excessive Heat ◽  
Pin Fin ◽  
Power Application

2.5-D package with through silicon vias (TSVs) on interposer has been envisioned as the most viable way in heterogeneous integration. In this work, several design approaches are considered in the thermal analysis and enhancements of a 2.5-D package with multi chips on through silicon interposer (TSI), which include overmolding materials, metal slug, lid attachment, pin fin heat sink and fan-driven heat sink cooling. The analysis models consist of two dummy flip chips on a silicon interposer to represent the logic die and memory die, respectively. Package submodels, especially the TSV ones, are analyzed with good modeling accuracy. Package thermal modeling indicates that the thermal conductivity of the epoxy overmolding has minimal effect on the thermal performance of copper slug package. Lid attachment further enhances the thermal performance through peripheral substrate attachment. Both designs largely rely on thermally conductive PCB (4L) to maximize power dissipation. Pin-fin heat sink, made of aluminum, can be mounted on the package top to further minimize thermal resistance and extend the power dissipation beyond 10W. For high power application, fan cooled heat sink is used to reduce excessive heat. Copper based aluminum heat sink can remove the heat of 120W from the bare-die package. Self heating due to high current density through the TSV is analyzed. The proposed analytical expression gives good prediction on the local TSV hot spot. It is demonstrated that a distributed TSV network design provides lower temperature rise, which shall have lower risk of failures and is preferred in practice.

Enabling Thermal Management of High-Powered Server Processors Using Passive Thermosiphon Heat Sink

2019 ◽  
Author(s):  
Devdatta P. Kulkarni ◽  
Priyanka Tunuguntla ◽  
Guixiang Tan ◽  
Casey Carte
Keyword(s):  
Heat Pipe ◽  
High Power ◽  
Heat Sink ◽  
Capital Investment ◽  
Thermal Design ◽  
Heat Sinks ◽  
Air Cooling ◽  
Liquid Cooling ◽  
Two Phase ◽  
Pipe Heat

Abstract In recent years, rapid growth is seen in computer and server processors in terms of thermal design power (TDP) envelope. This is mainly due to increase in processor core count, increase in package thermal resistance, challenges in multi-chip integration and maintaining generational performance CAGR. At the same time, several other platform level components such as PCIe cards, graphics cards, SSDs and high power DIMMs are being added in the same chassis which increases the server level power density. To mitigate cooling challenges of high TDP processors, mainly two cooling technologies are deployed: Liquid cooling and advanced air cooling. To deploy liquid cooling technology for servers in data centers, huge initial capital investment is needed. Hence advanced air-cooling thermal solutions are being sought that can be used to cool higher TDP processors as well as high power non-CPU components using same server level airflow boundary conditions. Current air-cooling solutions like heat pipe heat sinks, vapor chamber heat sinks are limited by the heat transfer area, heat carrying capacity and would need significantly more area to cool higher TDP than they could handle. Passive two-phase thermosiphon (gravity dependent) heat sinks may provide intermediate level cooling between traditional air-cooled heat pipe heat sinks and liquid cooling with higher reliability, lower weight and lower cost of maintenance. This paper illustrates the experimental results of a 2U thermosiphon heat sink used in Intel reference 2U, 2 node system and compare thermal performance using traditional heat sinks solutions. The objective of this study was to showcase the increased cooling capability of the CPU by at least 20% over traditional heat sinks while maintaining cooling capability of high-power non-CPU components such as Intel’s DIMMs. This paper will also describe the methodology that will be used for DIMMs serviceability without removing CPU thermal solution, which is critical requirement from data center use perspective.

Cooling of High Powered GPUs Using Liquid Nitrogen Cold Plates Made With Additive Manufacturing

2021 ◽  
Author(s):  
Alec Nordlund ◽  
Rachel McAfee ◽  
Rebecca Ledsham ◽  
Joshua Gess
Keyword(s):  
Additive Manufacturing ◽  
Liquid Nitrogen ◽  
Data Center ◽  
Power Efficiency ◽  
Thermal Design ◽  
Cryogenic Cooling ◽  
Air Cooling ◽  
Two Phase ◽  
Computational Performance ◽  
Two Phase Cooling

Abstract Processor energy density is exceeding the capabilities of conventional air-cooling technology, but two-phase cooling has the potential to manage these resulting heat fluxes at reliable temperatures and higher electrical efficiency. When two-phase cooling is used in tandem with overclocking, data center footprints are reduced as individual chip processing power can be set at limits well beyond the manufacturer’s Thermal Design Power (TDP) or nominal operating condition. This study examines how Liquid Nitrogen (LN2) can be used with Additive Manufacturing (AM) and overclocking to increase the computational performance of a commercially available GPU. The power consumption and frequency relationship were established for both the cryogenically cooled solution and a comparative air-cooled solution. The cryogenic solution saw up to a 17.4% increase in compute efficiency and an 18.1% improvement in compute speed with comparable power efficiency at an equivalent performance level to the air-cooled solution. This study considers the computational performance and efficiency gains that can be acquired through cryogenic cooling on an individual graphics card, which can be replicated on a larger scale in data center applications.

Thermal Design and Performance of Two-Phase Meso-Scale Heat Exchangers

2005 ◽  
Author(s):  
Robert Hannemann ◽  
Joseph Marsala ◽  
Martin Pitasi
Keyword(s):  
Heat Exchangers ◽  
Thermal Design ◽  
Low Flow ◽  
Commercial Application ◽  
Working Fluid ◽  
Small Scale ◽  
Air Cooling ◽  
Cold Plate ◽  
Two Phase ◽  
Meso Scale

Dramatically increased power dissipation in electronic and electro-optic devices has prompted the development of advanced thermal management approaches to replace conventional air cooling using extended surfaces. One such approach is Pumped Liquid Multiphase Cooling (PLMC), in which a refrigerant is evaporated in a cold plate in contact with the devices to be cooled. Heat is then rejected in an air or water-cooled condenser and the working fluid is returned to the cold plate. Reliable, highly efficient, small-scale components are required for the commercial application of this technology. This paper presents experimental results for two-phase meso-scale heat exchangers (cold plates) for use in electronics cooling. The configurations studied include single and multi-pass designs using R134a as the working fluid. With relatively low flow rates, low effective thermal resistances were achieved at power levels as high as 376 W. The results confirm the efficacy of PLMC technology for cooling the most powerful integrated circuits planned for the next decade.

On the Correlation Between Power Density Distribution and Junction-Case Thermal Resistance for Electronic Packages

2003 ◽  
Author(s):  
Sai Ankireddi ◽  
Henry H. Jung ◽  
James Jones
Keyword(s):  
Thermal Resistance ◽  
Density Distribution ◽  
Power Density ◽  
Thermal Performance ◽  
Power Distribution ◽  
Hot Spot ◽  
Electronic Packages ◽  
Power Density Distribution ◽  
Lower Power ◽  
Simulation Testing

When comparing two electronic packages identical in all respects except die plan dimensions and power, wherein the package with the smaller die is associated with a lower power, it is often hypothesized that the lower-powered package would have a lower junction-case thermal resistance. This hypothesis is generally based on the questionable argument that because the smaller package has lower power, its internal temperatures should be lower and hence a lower junction-case resistance should be ‘intuitively’ expected. In this article we show that drawing inferences about trends in junction-case resistance based merely on power trends, as outlined above, can be incorrect. In order to address this issue and provide better ‘indicators’ for comparing thermal performance across packages, we introduce the concept of the Power Density Distribution (PDD) and show how it relates with the junction-case thermal resistance. To illustrate its use in comparing thermal performance of packages we consider examples of several ICs with different die size/power combinations. Additionally, we also note the correlation between peaks in the spatial distribution of the power density and those of the die temperature distribution; in effect, this furnishes a simple way to identify candidate hot-spot locations on the die without resorting to extensive numerical thermal simulation/testing. We illustrate this intuitively anticipated concept for a variety of power distribution scenarios in some of our example IC packages.

Local Measurements of Flow Boiling Heat Transfer on Hot Spots in 3D Compatible Radial Microchannels

2015 ◽  
Author(s):  
Fanghao Yang ◽  
Mark Schultz ◽  
Pritish Parida ◽  
Evan Colgan ◽  
Robert Polastre ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Power Density ◽  
High Power ◽  
Hot Spots ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Hot Spot ◽  
Uniform Heat Flux ◽  
Two Phase ◽  
Flow Boiling Heat Transfer

Hot spots and temperature non-uniformities are critical thermal characteristics of current high power electronics and future three dimensional (3D) integrated circuits (ICs). Experimental investigation to understand flow boiling heat transfer on hot spots is required for any two-phase cooling configuration targeting these applications. This work investigates hot spot cooling utilizing novel radial microchannels with embedded pin arrays representing through-silicon-via (TSV) interconnects. Inlet orifices were designed to distribute flow in radial channels in a manner that supplies appropriate amounts of coolant to high-power-density cores. Specially designed test vehicles and systems were used to produce non-uniform heat flux profiles with nominally 20 W/cm2 background heating, 200 W/cm2 core heating and up to 21 W/mm2 hot spot (0.2 mm × 0.2 mm) heating to mimic a stackable eight core processor die (20 mm × 20 mm) with two hot spots on each core. The temperatures associated with flow boiling heat transfer at the hot spots were locally measured by resistance temperature detectors (RTDs) integrated between the heat source and sink. At nominal pressure and flow conditions, use of R1234ze in these devices resulted in a maximum hot spot temperature (Ths) of under 63 °C and average Ths of 57 °C at a hot spot power density of 21 W/mm2. A semi-empirical model was used to calculate the equivalent heat transfer rate around the hot spots which can provide a baseline for future studies on local thermal management of hot spots.

Thermal Performance of Vapor Chambers Under Hot Spot Heating Conditions

2005 ◽  
Author(s):  
Je-Young Chang ◽  
Unnikrishnan Vadakkan ◽  
Ravi Prasher ◽  
Suzana Prstic
Keyword(s):  
Thermal Performance ◽  
Hot Spots ◽  
Hot Spot ◽  
Heat Pipes ◽  
Air Cooling ◽  
Test Results ◽  
Uniform Heating ◽  
One Dimensional ◽  
Localized Heating ◽  
Phase Change Phenomena

Use of heat pipes (or vapor chambers) is considered as one of the promising technology to extend the capability of air cooling. This paper reports the test results of vapor chambers using two different sets of test heaters (copper post heater and silicon die heater). Experiments were conducted to understand the effects of non-uniform heating conditions on the thermal performance of vapor chambers. In contrast to the copper post heater which provides ideal heating condition, silicon chip package was developed to replicate more realistic heat source boundary conditions of microprocessors. The chip contains three metallic heaters: a 10 × 12 mm heater in order to provide uniform heating, a 10 × 3 mm heater in order to simulate a localized heating, and a 400 × 400 μm heater in order to simulate the hot spots on actual microprocessors. In the experiment, the highest heat flux from the hotspot heater was approximately 690 W/cm2. Test results indicated that both conduction heat transfer and phase-change phenomena played key roles in the evaporator. The study found that the evaporator resistance was almost insensitive to non-uniform heating conditions, but was clearly dependent on the amount of power applied over the die area. In addition, a simple one-dimensional thermal model was developed to predict the performance of vapor chambers for non-uniform heating conditions and the results were compared against experiments.

scholarly journals Green Cooling of High Performance Microprocessors: Parametric Study Between Flow Boiling and Water Cooling

2011 ◽  
Vol 3 (4) ◽  
Author(s):  
Jonathan A. Olivier ◽  
Jackson B. Marcinichen ◽  
Arnaud Bruch ◽  
John Thome
Keyword(s):  
Ethylene Glycol ◽  
Single Phase ◽  
Flow Boiling ◽  
Hot Spot ◽  
Junction Temperature ◽  
Air Cooling ◽  
Processing Unit ◽  
Exergetic Efficiency ◽  
Two Phase ◽  
Cooling Cycle

Due to the increase in energy prices and spiralling consumption, there is a need to greatly reduce the cost of electricity within data centers, where it makes up to 50% of the total cost of the IT infrastructure. A technological solution to this is using on-chip cooling with a single-phase or evaporating liquid to replace energy intensive air-cooling. The energy carried away by the liquid or vapor can also potentially be used in district heating, as an example. Thus, the important issue here is “what is the most energy efficient heat removal process?” As an answer, this paper presents a direct comparison of single-phase water, a 50% water–ethylene glycol mixture and several two-phase refrigerants, including the new fourth generation refrigerants HFO1234yf and HFO1234ze. Two-phase cooling using HFC134a had an average junction temperature from 9 to 15 °C lower than for single-phase cooling, while the required pumping power for the central processing unit cooling element for single-phase cooling was on the order of 20–130 times higher to achieve the same junction temperature uniformity. Hot-spot simulations also showed that two-phase refrigerant cooling was able to adjust to local hot-spots because of flow boiling’s dependency on the local heat flux, with junction temperatures being 20 to 30 °C lower when compared to water and the 50% water–ethylene glycol mixture, respectively. An exergy analysis was developed considering a cooling cycle composed by a pump, a condenser, and a multimicrochannel cooler. The focus was to show the exergetic efficiency of each component and of the entire cycle when the subject energy recovery is considered. Water and HFC134a were the working fluids evaluated in such analysis. The overall exergetic efficiency was higher when using HFC134a (about 2%), and the exergy destroyed, i.e., irreversibilities, showed that the cooling cycle proposed still have a huge potential to increase the thermodynamic performance.

scholarly journals Enhanced Power Extraction with Sediment Microbial Fuel Cells by Anode Alternation

Fuels ◽  
2021 ◽  
Vol 2 (2) ◽  
pp. 168-178
Author(s):  
Marzia Quaglio ◽  
Daniyal Ahmed ◽  
Giulia Massaglia ◽  
Adriano Sacco ◽  
Valentina Margaria ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Energy Harvesting ◽  
Power Density ◽  
Microbial Fuel Cells ◽  
Average Power ◽  
Power Extraction ◽  
Harvesting Technique ◽  
Harvesting Method ◽  
Energy Harvesting Devices ◽  
Efficient Power

Sediment microbial fuel cells (SMFCs) are energy harvesting devices where the anode is buried inside marine sediment, while the cathode stays in an aerobic environment on the surface of the water. To apply this SCMFC as a power source, it is crucial to have an efficient power management system, leading to development of an effective energy harvesting technique suitable for such biological devices. In this work, we demonstrate an effective method to improve power extraction with SMFCs based on anodes alternation. We have altered the setup of a traditional SMFC to include two anodes working with the same cathode. This setup is compared with a traditional setup (control) and a setup that undergoes intermittent energy harvesting, establishing the improvement of energy collection using the anodes alternation technique. Control SMFC produced an average power density of 6.3 mW/m2 and SMFC operating intermittently produced 8.1 mW/m2. On the other hand, SMFC operating using the anodes alternation technique produced an average power density of 23.5 mW/m2. These results indicate the utility of the proposed anodes alternation method over both the control and intermittent energy harvesting techniques. The Anode Alternation can also be viewed as an advancement of the intermittent energy harvesting method.

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