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Thermal Management of Electronics– Energy Conversion Issues
Avram Bar-CohenDepartment of Mechanical Engineering
University of Maryland
Rohsenow Symposium – MIT Cambridge, Mass
May 16th 2003
5/16/03 WMR-ABC 2
Drivers for Thermal Packaging
Air as the Ultimate Heat SinkMarket-Driven Thermal Solutions
Price – volume – weight – reliability Environmentally-Friendly Design
Low power consumptionSemiconductor devicesPackaging and cooling
Low noise: acoustic and EMI Recyclability
Feature-Rich Design ToolsIntegrated with product CAD systemParametric optimization
5/16/03 WMR-ABC 3
“spreading” + natural convection/radiation
Entropy generation minimization
Least-material optimization
Least-energy optimization
Work allocation factor, ξpp
= Pumping work/Total cooling work= Wpp / [WM + WPP]
Design for Sustainability
5/16/03 WMR-ABC 4
Design for Sustainability Metrics
Coefficient of Performance
COP = qT/IP
IP = Vair × ∆P
Total Work Coefficient of Performance
COPT = qTt1/WT
WT = WM + WPP
WM = 85 M (aluminum-estimated)
5/16/03 WMR-ABC 5
High Performance Heat Sink Arrays
(d) Forging (e) Skiving
(a) Bonding (b) Folding
(f) Machining
(c )Modified Die-Casting
5/16/03 WMR-ABC 6
Heat Sink Coefficient of Performance
L = W = 0.1 m, H = 0.05 m, θθbb= 25 K, k = 200 W/m-K
∆P = 40Pa, Vair = 0.02 m3/sqT = 284W, IP = 0.8WCOP = 355
∆P = 40Pa, Vair = 0.02 m3/sqT = 194W, IP = 0.8WCOP = 243
2030
4050
6070
80
0.01
0.01
50.
020.
025
0.03
0.03
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0.04
0
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Qmax/Wpp
Vair (m3/s)∆P (Pa)
900-1000800-900700-800600-700500-600400-500300-400200-300100-2000-100
20 30 40 5060
7080
0.01
0.01
50.
020.
025
0.03
0.03
50.
04
0
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Qmax/Wpp
Vair (m3/s)∆P (Pa)
900-1000800-900700-800600-700500-600400-500300-400200-300100-2000-100
(a) (b)
Maximum heat transfer design Least material design
CO
P =
q T/ I
P
CO
P =
q T/ I
P
5/16/03 WMR-ABC 7
COPT Comparison Forced convection SISE plate-fins
L= W = 0.1 m, H = 0.05 m, θb= 25 K, k = 200 W/m-K
COPT = qTt1/WT
20 3040
5060
7080
0.01
0.01
50.
020.
025
0.03
0.03
5
0.04
0
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Q/ET
∆P (Pa) Vair (m3/s)
90-10080-9070-8060-7050-6040-5030-4020-3010-200-10
20 30 4050 60
7080
0.01
0.01
50.
020.
025
0.03
0.03
50.
04
0
10
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Q/ET
∆P (Pa) Vair (m3/s)
90-10080-9070-8060-7050-6040-5030-4020-3010-200-10
(a) (b)
Maximum heat transfer designLeast material design
WT = 85M + IP t1
5/16/03 WMR-ABC 8
2030
4050
6070
80
0.010.01
50.020.02
50.030.03
50.04
0
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CO
P T
Vair, m3/s∆P, Pa
2030
4050
6070
80
0.010.01
50.020.02
50.030.03
50.04
0
10
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CO
P T
∆P, PaVair, m3/s
(a) COPT, Extrusion (b) COPT, Skiving
COPT ComparisonForced convection SISE plate-fins
L= W = 0.1 m, H = 0.05 m, θb= 25 K, k = 200 W/m-K
COPT = qTt1 /WTWT = 85M + IP t1
5/16/03 WMR-ABC 9
COPT Optimization SISE plate-fins, WT = 10 kWh, t1 = 6000h
W T = 1 0 k W h , t1 = 6 0 0 0 hNC: natura l c onvec t ion, F C : forc ed c onvec t ion
0
10
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0 1 2 3 4 5 6 7 8 9 10 11
F in D en s ity , N /c m
CO
P T =
[ (q
t 1) /
WT
]
F C, 0.028 F C, 0.042F C, 0.083 F C, 0.125F C, 0.139 F C, 0 m as sNC, a ll m as s
W ork a lloc at ion fac tor, ξpp = W pp / W T
L ocus o f C O P T , m ax
5/16/03 WMR-ABC 10
Refrigeration Technologies for Microelectronics
Kryotech IBM S/390 G4
P P P P P PN N N N N N
Substrate
Cap
Thermoelectric
Chip
module
Epoxyinterfaces
Thermalpaste
5/16/03 WMR-ABC 11
Issues in Refrigerated Packaging
CMOS Chip/CPU PerformancePerformance Driven by” Hot Spots” “Cost” of Refrigeration System
Life Cycle CostVolume, MassPower Consumption
Reliability of Refrigeration/Packaging Refrigeration HardwareCondensation on PCBs + Refrigerant LinesVibration
5/16/03 WMR-ABC 12
FundamentalThermal Packaging ResearchLow-cost, high-k packaging materials Low-cost, reliable PCM’s Enhancement of convection/boiling/spray Heat Sink/HX Manufacturing processes Compact liquid cooling/refrigeration systemsImproved solid state refrigerationLow environmental impact systems Integrated modeling tools
5/16/03 WMR-ABC 13
Concluding Thoughts
Growing energy consumption in electronic systems Thermal Management significant fraction of energy consumptionPromise of local energy conversionDesign for sustainability requires:
Passive cooling where feasible Optimization of COP for active coolingOptimization of COPT for all systems