Lightweight, LowLightweight, Low--Cost Heat Cost Heat Sink for HighSink for High--Heat Flux Heat Flux
ApplicationsApplicationsArt Art FortiniFortini
ULTRAMETULTRAMETTFAWS MeetingTFAWS MeetingAugust 8, 2006August 8, 2006
Basic ConceptBasic Concept
Use openUse open--cell SiC foam as an cell SiC foam as an extended surface or cooling fin for extended surface or cooling fin for SiC integrated circuits (ICs).SiC integrated circuits (ICs).AdvantagesAdvantages•• Perfect CTE match with SiC ICsPerfect CTE match with SiC ICs•• High thermal conductivity High thermal conductivity •• High surface areaHigh surface area•• Low pressure dropLow pressure drop•• Immune to corrosionImmune to corrosion
Silicon Carbide FoamSilicon Carbide FoamHigh surface areaHigh surface areaImportant for transferring heat to cooling mediumImportant for transferring heat to cooling medium
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Surf
ace
area
(cm
2/cm
3)
100 ppi
80 ppi65 ppi
Pressure DropPressure Drop
Silicon carbide Silicon carbide foamfoam•• 0.5 x 2 x 30.5 x 2 x 3”” slabslab•• Water flow parallel Water flow parallel
to long axis.to long axis.•• Important for Important for
flowing large flowing large quantities of quantities of coolant without coolant without pressure drop pressure drop penalty.penalty.
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flow (g/min)
dP (m
m H
2O)
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flow (cm/s)
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sid)
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80, 20
no foam
Pressure DropPressure Drop
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air velocity (ft/s)
pres
sure
dro
p (p
sid) 20
30456580100
1" thick foam • Carbon foam– 1” thick slab– Air flow
perpendicular to thickness
– Very low pressure drop
UltrafoamsUltrafoams
Begin with polyurethaneBegin with polyurethaneImpregnate with resinImpregnate with resinPyrolyze to form glassy carbonPyrolyze to form glassy carbon•• 33--1000 pores per inch (ppi)1000 pores per inch (ppi)
CVI with SiCCVI with SiC•• 55--30% relative density30% relative density•• Other materials: Si, Gr, pyC, Si(C), Other materials: Si, Gr, pyC, Si(C),
refractory metals, etcrefractory metals, etc
UltrafoamUltrafoam
Vitreous carbon Silicon carbide
Basic ConceptBasic Concept
FaceplateIC heatsource
Coolant in Coolant out
SiC foam
ExperimentalExperimental
Copper block w/ resistive heaters
SiC foamTi Pi
Te
dP
Thermocouple (at heater/foam bondline) Insulation
Coolant outletCoolant inlet
Bondline
Unique Thermal Control Challenges(High Heat Flux, High Power, Low Temperature)
10 3
4 10
2 10
1 10
10 0
10 -1
10 -2
1000 2000 3000 4000 5000
Solar heating
Rocket motor case (external)
Reentry from Earth orbit
Nuclear blast (1 Mt, 1 mi)
Ballistic entry Rocket nozzle throat (internal)
Laser diodes
Temperature (K)
2 q" W/cm
Electronic & microwave devicesLaser diodesLaser gain media
150°C
•Phase II goal was to reach 1000 W/cm2 with temperature below 150°C
Experimental ResultsExperimental ResultsFoam PPI / density Heat Flux Flow Rate Heat Flux / Flow Rate
Cooler SurfaceTemperature
(W/cm2) (GPM) (W min /cm2 G) (°C)100ppi/ 9.8% 711 0.5 1422 1131000ppi / 12% 867 0.5 1734 122100ppi/ 10% 612 0.5 1224 47.81000ppi/ 5% 1006 0.64 1572 165300ppi/ 20% 1011 0.5 2022 53100ppi/ 20% 1000 1.0 1000 135300ppi/ 20% 758 0.3 2527 42.4
• Phase II goal: 1000 W/cm2 while below 150°C.
• Ultramet SiC foam 1011 W/cm2 at only 53°C!
Experimental ResultsExperimental Results
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Heat Flux (W/cm2)
Coo
ler S
urfa
ce T
empe
ratu
re (C
)
300ppi 2-28-06
300ppi with Cu Flap
600ppi-copper flap 9-14-051000ppi (2)(9-9-05)
100PPI-10%
100ppi-20%
100-20%
300ppi-20%
600ppi
Experimental ResultsExperimental ResultsHeat Stress = Heat Flux/ Flow rate (Gallons per minute)
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Heat Stress (W*min/cm2*G)
Coo
ler S
urfa
ce T
empe
ratu
re (C
)
300ppi 2-28-06
300ppi with Cu flap
600ppi-copper flap 9-14-051000(2)(9-9-05)
100PPI-10%
100ppi-20%
100-20%
300ppi-20%
600ppi
Thermal ModelingThermal ModelingX-Ray Tomography Ultramet SiC Foam
Thermal Model InputThermal Model InputPartPart Side DimensionsSide Dimensions ThicknessThickness Thermal Conductivity Thermal Conductivity
(W/m C)(W/m C)
SiC FoamSiC Foam 2 x 22 x 2”” 0.50.5”” 4040
TIM1TIM1 2 x 22 x 2”” 100 100 µµmm 4040
SiC Heat spreaderSiC Heat spreader 2 x 22 x 2”” 250 250 µµmm 200200--500 (4H500 (4H--SiC)SiC)
Die Attach (TIM2)Die Attach (TIM2) 5 x 5 mm5 x 5 mm 50 50 µµmm 4040
DieDie 5 x 5 mm5 x 5 mm 380 380 µµmm 200200--500 (4H500 (4H--SiC)SiC)
GaN active areaGaN active area 0.25 x 4 mm0.25 x 4 mm n/an/a n/an/a
Modeling ConclusionsModeling Conclusions1kW/cm2 with Heat Spreader
0.1 and 0.5 GPM 27 and 28 °C
1kW/cm2 without Heat Spreader
0.1 and 0.5 GPM 61 and 48 °C
0.1 GPM 0.1 GPM
0.5 GPM0.5 GPM
Other WorkOther Work-- High Heat Flux GaN-Based RF Componentsand Cooling Methods
Jeff Calame, Steve Binari, Robert Myers †, and Frank Wood †Naval Research Laboratory, Washington, DC 20375
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Measured power density (W/cm2 )
Experimentally measured temperatures(Cooler surface under heat probe source center )
(0.502 gal/min, 20 oC H2O inlet)
OFHC copper cooler
Silicon cooler
Aluminumnitridecooler
Tem
pera
ture
( o C
)
-Micromachined to 500µm
3rd Annual Workshop on Thermal Management of High Flux Commercial and Military Electronics University of Maryland, College Park, MD October 18, 2004
Ultramet Foam (same flow rate)
•Ultramet SiC foam has comparable performance to micromachined OFHC copper and single crystal silicon with diamond heat spreader.
SummarySummaryEffects of SiC foam:Effects of SiC foam:•• 1011 W/cm1011 W/cm2 @53C w/ 0.5 GPM water@53C w/ 0.5 GPM water
Thermal Model predicts improvements Thermal Model predicts improvements by going to heat spreader configuration.by going to heat spreader configuration.•• 27 27 ººC with heat spreader w/ 0.1 GPMC with heat spreader w/ 0.1 GPM•• 61 61 ººC for 100ppi. 10% density (stock item) C for 100ppi. 10% density (stock item)
at low flow rate.at low flow rate.
Excellent heat transfer Excellent heat transfer little material little material is requiredis required (small volume/ light and (small volume/ light and inexpensive).inexpensive).Low coolant flow rates requires less in Low coolant flow rates requires less in way of supporting systemsway of supporting systems-- pumping, pumping, filtration, etc.filtration, etc.