Thermal Management Roadmap Avram Bar-Cohen Department of Mechanical Engineering University of Maryland UEF THERMES 2002 Santa Fe, NM January 13-17, 2002
Electronic Industry Business Trends Packaging driven by product category Market-driven price point Cost/Function primary challenge Rapid bifurcation in product categories High functionality and value added Low cost commodity Supply Chain drives productivity SCM Enables cost reduction EMS growing 50% per year 8/29/01 Cooling-ABC 2
Electronic Industry Business Trends Market Convergence Computing/Telecom fueled 1990 s gold rush Automotive/Consumer 2000 s??? Volume Drivers Cell phones Optoelectronics Bluetooth OLED displays Shrinking Product Cycles Product release to peak production = 6-9 mo Production end = 24 mo 8/29/01 Cooling-ABC 3
Electronic Industry Technology Trends Moore s Law fatigue Silicon device growth slows Feature size shrink returning to 3 year cycles SOP needed after 2005 Under-Exploitation of Silicon Potential Design Productivity Gap Packaging Limitations Thermal Management CMOS provided only temporary relief Key element in performance, reliability, cost Develop metrics for thermal packaging 8/29/01 Cooling-ABC 4
Drivers for Thermal Packaging Air as the Ultimate Heat Sink Market-Driven Thermal Solutions Environmentally-Friendly Design Low power consumption Low noise: acoustic and EMI Recyclability Feature-Rich Design Tools Integrated with product CAD system Parametric optimization 8/29/01 Cooling-ABC 5
Design for Sustainability spreading + natural convection/radiation Least-material optimization Entropy generation minimization Least-energy optimization Work allocation factor, ξ pp = Pumping work / Total cooling work = W pp / [W M + W PP ] 8/29/01 Cooling-ABC 6
Heat Sink Design Metrics Thermal resistance [K/W] R hs = θ b /q T Array heat transfer coefficient h a = q T /(LWθ b ) [W/m 2 -K] Mass-specific heat transfer coefficient [W/kg-K] h m = q T /(ρ fin V fin θ b ) Space claim heat transfer coefficient h sc = q T /(LWHθ b ) 8/29/01 Cooling-ABC 7 3
Design for Sustainability Metrics Coefficient of Performance COP = q T /IP IP = V air P Total Work Coefficient of performance COP T = q T t 1 /W T W T W M = W M + W PP = 85,000 M (estimated) q T : Heat dissipation, kw W T : Energy investment for cooling, kwh W M : Formation/fabrication work, kwh W PP : Pumping work, kwh t 1 : Duty cycle, h M: Fin mass, kg P: Pressure drop, Pa V air : Volumetric flow rate, m 3 /s 8/29/01 Cooling-ABC 8
Coefficient of Performance P = 40Pa, V air = 0.02 m 3 /s q T = 284W, IP = 0.8W COP = 355 Typical values P = 40Pa, V air = 0.02 m 3 /s q T = 194W, IP = 0.8W COP = 243 COP = q T / IP Q max /W pp (a) 1000 900 800 700 600 500 400 300 200 100 0 20 30 40 50 P (Pa) 60 70 80 0.04 0.035 0.03 0.01 0.015 0.02 0.025 V air (m 3 /s) 900-1000 800-900 700-800 600-700 500-600 400-500 300-400 200-300 100-200 0-100 1000 900 800 700 600 Q max /W pp 500 400 300 200 100 0 COP = q T / IP (b) 20 30 40 50 60 70 P (Pa) 80 0.04 0.035 0.03 0.025 0.02 0.015 0.01 V air (m 3 /s) 900-1000 800-900 700-800 600-700 500-600 400-500 300-400 200-300 100-200 0-100 Maximum heat transfer design Least material design L = W = 0.1 m, H = 0.05 m, θ b = 25 K, k = 200 W/m-K 8/29/01 Cooling-ABC 9
COP T Comparison: Maximum Vs Least-material Forced convection SISE plate-fins L= W = 0.1 m, H = 0.05 m, θ b = 25 K, k = 200 W/m-K Least material design Maximum heat transfer design (a) 100 90 80 70 60 Q/E T 50 40 30 20 10 0 20 30 40 P (Pa) 50 60 70 80 0.04 0.035 0.01 0.015 0.02 0.025 0.03 V air (m 3 /s) 90-100 80-90 70-80 60-70 50-60 40-50 30-40 20-30 10-20 0-10 (b) Q/E T 100 90 80 70 60 50 40 30 20 10 0 20 30 40 P (Pa) 50 60 70 80 0.04 0.035 0.03 0.025 0.02 0.01 0.015 V air (m 3 /s) 90-100 80-90 70-80 60-70 50-60 40-50 30-40 20-30 10-20 0-10 COP T = q T t 1 /W T W T = 85M + IP t 1 M - mass (kg), IP - pumping power (kw), t 1 - life cycle (6000 hours) 8/29/01 Cooling-ABC 10
COP T Comparison: Extrusion Vs Skiving Forced convection SISE plate-fins L= W = 0.1 m, H = 0.05 m, θ b = 25 K, k = 200 W/m-K 60 60 50 50 40 30 COPT 40 30 COPT 20 20 10 10 0 0 0.04 0.035 0.03 V air, m 3 /s 0.025 0.02 0.015 0.01 80 70 60 50 40 20 30 P, Pa 0.04 0.035 0.03 V air, m 3 /s 0.025 0.02 0.015 0.01 80 70 60 50 40 20 30 P, Pa (a) COP T, Extrusion (b) COP T, Skiving COP T = q T t 1 /W T W T = 85M + IP t 1 M - mass (kg), IP - pumping power (kw), t 1 - life cycle (6000 hours) 8/29/01 Cooling-ABC 11
COP T Optimization: Fixed Input Work Forced convection SISE plate-fins, W T = 10 kwh, t 1 = 6000h W T = 10 kwh, t 1 = 6000 h NC: natural convection, FC: forced convection 100 Work allocation factor, ξpp = W pp / W T FC, 0.028 FC, 0.042 FC, 0.083 FC, 0.125 FC, 0.139 FC, 0 mass NC, all mass 90 80 COPT = [ (q t1) / WT ] 70 60 50 40 30 Locus of COP T, max 20 10 0 0 1 2 3 4 5 6 7 8 9 10 11 Fin Density, N/cm L = W = 0.1 m, H = 0.05 m, θ b = 25 K, k = 200 W/m-K 8/29/01 Cooling-ABC 12
SOA Heat Spreaders Ceramic-Coated Cu plate 8/29/01 Cooling-ABC 13
Heat Spreaders Technology Needs High k Coatings High k composites Vapor Chambers Micro Heat pipes 2φ Thermosyphons Micro-fluidics Vapor chamber Heat sink Air flow Chip(s) 8/29/01 Cooling-ABC 14
Heat Spreaders Research Needs Low-cost, high-k, TCE-matched materials Algorithms for optimal design Improved on-chip spreading techniques Correlations/analytical models: Dryout/rewetting of micro-channels Dryout/rewetting of micro-porous structures Local spreading resistance 8/29/01 Cooling-ABC 15
Heat Pipes Technology Needs Q Q Air Flow Q Air Flow Q 8/29/01 Cooling-ABC 16
Heat Pipes Research Needs Deformable & flexible thermal-hinge High radial & axial heat fluxes Long, Low cost, high performance Technology capable of withstanding harsh environments (automotive and aerospace) High g High, cyclic temperatures Correlations/algorithm for thermosyphon design 8/29/01 Cooling-ABC 17
SOA Interface Materials Elastomer Grease Phase Change Material Classs Grease Phase Change Elastomer Epoxy Eutectic Performance [K/W/cm 2 ] 0.3-0.7 0.35-1.0 1+ 0.25-0.5 ~0.1 8/29/01 Cooling-ABC 18
Thermal Interfaces Technology Needs Develop standardized measurements Characterize normal process variations Optimize filled polymers Study time variant thermal properties Create new thermal elastomers k = 20-100 W/mK, Thin bondlines (~10-25µm) Low elastic moduli Block 1 Interface Material Block 2 8/29/01 Cooling-ABC 19
Thermal Interfaces Research Needs Nanoparticle-filled high-k pastes, epoxies, elastomers Techniques/materials to minimize interfacial stresses Correlations/theories for fatigue of bonded interfaces Microencapsulated PCM packaging materials 8/29/01 Cooling-ABC 20
Air Cooling Technology Needs Air flow Q High aspect-ratio, closely-spaced fins Design/Optimize for manufacturability High head fans Low acoustic/emi noise 8/29/01 Cooling-ABC 21
Air Cooling Industrial Research Needs Advanced manufacturing techniques for metal and composite material heat sinks Compact high head/moderate flow/low noise fans Low power consumption micro-fans for notebook computers and handheld electronics High pressure/high flow blowers with low acoustical and EMI noise 8/29/01 Cooling-ABC 22
Air Cooling Research Needs Models/correlations for heat transfer in transition and low Reynolds number flow Low Reynolds number turbulence models for use in CFD codes Heat sink design/optimization procedures Mass constraints Volume constraints Energy requirements/constraints 8/29/01 Cooling-ABC 23
SOA Liquid Cooling 8/29/01 Cooling-ABC 24
Liquid Cooling Technology Needs Air to water heat exchanger Pump Water reservoir Air flow Cold plate Filter Electronic module Superior coolant Exploit known technology cold plates, compact HX, pumps Wide range of enhancements 8/29/01 Cooling-ABC 25
Liquid Cooled Cold Plates 8/29/01 Cooling-ABC 26
Liquid Cooling Research Needs Miniaturized components with high reliability and enhanced performance MEMS and meso-scale HX components MEMS and meso-scale cold-plates Direct water cooling of chips/packages 8/29/01 Cooling-ABC 27
Direct Liquid Immersion Cooling Heat Exchanger Side View Blower Pump CP U Mo dule 8/29/01 Cooling-ABC 28
SOA Spray Evaporative Cooling (Cray SV Module) Spray Nozzle Liquid Droplets Vapor Bubbles Heater Surface Liquid Film Thickness 8/29/01 Cooling-ABC 29
Direct Liquid Immersion Research Needs Thermofluid single- and two-phase correlations new dielectric coolants Non-uniform fluxes 3-D structures Dryout and CHF Nanoparticles for enhancing dielectric coolants MEMS/meso-scale thermal enhancement Correlations/models - evaporative spray cooling 8/29/01 Cooling-ABC 30
SOA Vapor Compression Refrigeration IBM S/390 G4 Kryotech 8/29/01 Cooling-ABC 31
Issues in Refrigerated Packaging CMOS Chip/CPU Performance Multiple High Power Devices Cost of Refrigeration System Life Cycle Cost Volume, Mass Power Consumption Reliability of Refrigeration/Packaging Refrigeration Hardware Condensation on PCBs + Refrigerant Lines Vibration 8/29/01 Cooling-ABC 32
Refrigeration Cooling Research Needs Highly reliable miniaturized components MEMS/meso-scale, low-cost, low noise refrigerators using solid-state, vapor compression, or absorption cycles MEMS/meso-scale, low-cost, packagesize cold plates New thermoelectric materials and fabrication methods 8/29/01 Cooling-ABC 33
TE Refrigeration Technology Needs Epoxy interfaces Thermal paste P N P N P N P N P N P N Substrate Chip Thermoelectric module Cap Low-cost semiconductor Technology Higher Z factor Improved interfaces 8/29/01 Cooling-ABC 34
Fundamental Thermal Packaging Research Low-cost, high-k packaging materials Low-Cost, reliable PCM s Enhancement of convection/boiling/spray Heat Sink/HX Manufacturing processes Compact liquid cooling /refrigeration systems Improved solid state refrigeration Low environmental impact systems Integrated modeling tools 8/29/01 Cooling-ABC 35
Concluding Thoughts Critical Need in Spreading/Interfaces On-chip On-PCB Heat Sink Base Untapped Potential in Direct Air-Cooling Heat Sink Optimization Heat Sink Manufacturing Advances 8/29/01 Cooling-ABC 36
Concluding Thoughts Liquids Provide Superior Spreading Pumped Cold Plates Pumped/Sprayed Dielectric Liquids Passive Immersion Refrigeration Creates New Options Chilled Air-Cooling Refrigerated Cold Plate Low Temperature Operation 8/29/01 Cooling-ABC 37