Dr. Daniel Kearney, ABB Corporate Research Centre, Switzerland
Cooling of Next Generation Power Electronics: Trends and Challenges © ABB Corporate Research February 1st 2012 | Slide 1
© ABB June 25, 2014
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Introduction
Market, ABB and Power Electronics Research
Application areas and technology drivers
Wide band gap semiconductors
Challenges associated with Power Electronics
Thermal management strategies
Challenges: selected highlights
Future trends
ABB and Power Electronics Research
ABB Corporate Research Centre Switzerland
Founded in 1967; 1 of 7 research centres
240 Employees by end of 2013
About 110 interns/diploma students/PhD`s in 2013
~40 nationalities today
Home of PEARL – Power Electronics Advanced Research Laboratory (open mid 2014)
Wide band gap devices: faster and smarter
© ABB June 25, 2014
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Power Electronic Modules in the electronic market Industry, Transportation, Transmission and Conversion
Low Power Semiconductors and Logic Components. PE market (10kW- 1GW)
kW W
Consumables
mW
Power Electronics Semiconductors Application areas
© ABB June 25, 2014
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2013 - Woodland, County Meath to North Wales
Power Electronics Technology drivers
Electrical performance
High Ratings: 6.5 kV, 1000A IGBTs
Very high switching losses per unit volume
EMI: shorter inductive loop
Power density
Efficiency
Robustness
High operating temperatures: SiC , 300 °C
Cost
Integrated Systems: Power chips & logic/microprocessors in one embedded package Need for more effective semiconductor devices
© ABB Group June 25, 2014 | Slide 6
What are Wide Band Gap devices? Switch faster and more efficiently
Device
Eg [eV]
ᵋr
k [W/mK]
CTE [ppm/°C]
Si
1.1
11.8
150
3
GaN
2.3-3.3
9-11
80-130
5.6
SiC
2.2-3.3
10
450
4
Diamond
5.4
5.5
2000
1
WBG have a larger band gap than traditional Si devices The high intrinsic temperature (above 800°C) of SiC offers excellent thermal stability. High breakdown field of SiC and saturated electron velocity → SiC ideal for high power operations.
Si source p
gate
SiC source
n+
n+ p
n- Si drift layer (very lower carrier concentration
source
gate
source n+ p
n+ p
n- SiC drift layer SiC substrate
drain Drift layer thickness: very thin Carrier concentration: very high
Si substrate
© ABB June 25, 2014
SiC | Slide 7
drain
=drastic reduction in on-state losses
What are Wide Band Gap devices? Switch faster and more efficiently
Faster switching frequencies → lower switching losses → higher efficiency
Larger blocking voltage
Fewer cells & fewer semiconductor chips → Higher reliability & lower cost
Operate at higher temperatures,
Can eliminate up to 90% of the power losses in electricity conversion compared to current Si based technology.
© ABB June 25, 2014
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Frequency scaling factor
Less losses does not always imply easier cooling
only for cooling…
10 x less heat!
© ABB Group Slide 9
Incandescent bulb
LED bulb
1880 2% efficiency 0.4 W/cm2 heat No designed cooling
2007 20% efficiency 4 W/cm2 heat Cooling structure required
© ABB June 25, 2014
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Introduction
Market, ABB and Power electronics research
Application areas and technology drivers
Wide band gap semiconductors
Challenges associated with Power Electronics
WBG thermal management strategies
Challenges: selected highlights
Conclusions
Thermal management Current technology applications
Thermal dissipition [W/cm2]
250 175°C 100A/1200V Powerex SiC Modules
200 3. Increase of Tj,max 150
Tj,max
100
2. Reduction of thermal resistance
50
1. Reduction of losses
200°C 175°C 150°C 125°C
TEnvironment = 40°C 0
0
500
1000
Thermal resistance Rth j-a [K/kWcm2] © ABB June 25, 2014
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1500
Power Electronics Integration Holistic design approach for optimisation
Performance Thermal management
Reliability
Operation temperature
Power cycling Thermal cycling
Electrical Efficiency (Power loss, EMI)
Harsh Environment
Power density /Cost Packaging manufacture Semiconductior Die size
© ABB June 25, 2014
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Application
Thermal management Current technology applications •
•
Paralleling of chips •
higher current ratings,
•
thermal improvements, and
•
sometimes for redundancy
Asymmetric performance of chips →
Unequal power sharing → asymmetry in the cooling •
Local thermal management becomes
critical at chip level.
© ABB June 25, 2014
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Thermal management What can we improve?
Q
h
A
Ts T
Maximise Heat produced from switching and conduction losses in the device
© ABB June 25, 2014
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What are our options? Influence of package
Limited
Exotic material Phase change materials
Minimise the chip temp rise relative to ambient
Thermal management Traditional package structure
Chip (heat source)
Substrate (AlN) ~180 K/kW Heat spreader baseplate (AlSiC) Thermal grease
~137 K/kW
Cooler/Heat sink ~250 … 900 K/kW
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Thermal greases Phase change materials Structured baseplate Liquid metals Heat spreaders
© ABB June 25, 2014
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Introduction
Market, ABB and Power electronics research
Application areas and technology drivers
Wide band gap semiconductors
Challenges associated with Power Electronics
Thermal management strategies
Challenges: selected highlight
Future Trends
Challenges: selected highlights Heat spreading
IGBT=32.6W
Diode=6.8W
h=1000W/m2K Traditional package stucture
Enhanced heat spreading Pre-preg CHIP
Silicone gel
CHIP
Copper leadframe
HTC applied to base 1000W/m2K
1090µm
CHIP Cu pure k=300W/mK
CHIP 250µm
Al2O3 k=27W/mK
400µm
Cu pure k=300W/mK
300µm
HTC applied to base 1000W/m2K
New package structures are needed to accommodate these WBG devices © ABB June 25, 2014
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950µm
Challenges: selected highlights
Thermal spreading to avoid hot spots
Minimal thermal resistance
Passive/active: application specific
Examples:
mini-channels
2 phase
© ABB June 25, 2014
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Challenges: selected highlights Integrated microfluidics: Pulsating heat pipes qout
qin • • • • • • © ABB June 25, 2014
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Sensible and latent heat transfer by liquid slugs and vapour plugs PHP is wickless – easier to integrate Operates independent of gravity Operate at sub-ambient pressures Lower cost/easier to manufacture compared to traditional wicked heat pipe Dielectric working fluids An Open Loop Pulsating Heat Pipe for Integrated Electronic Cooling Applications Daniel Kearney and Justin Griffin J. Heat Transfer 136(8), 081401, 2014,; doi: 10.1115/1.4027131
Challenges: selected highlights OLPHP testing facility High-speed camera -
Multi-angle support
© ABB Group June 25, 2014
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Transparent polycarbonate cover allows visual access
Challenges: selected highlights Effect of design parameters
Channel geometry Must be sufficiently small for surface tension to dominate, cause bubble formation Sharp corner effect Number of turns More turns: more fluid being heated, and more sites for pressure perturbations Too many turns: reduced Tevap, vapor pressure, pumping force Working fluid Critical properties: Surface tension, latent heat, specific heat, viscosity, and (dp/dT)sat Fill Ratio: Effects operating mode, sensible heat transfer capacity
1.9mm
Top
Bottom (a)
Orientation: Ideally, PHPs can operate independent of orientation (b)
© ABB Group June 25, 2014
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Challenges: selected highlights Thermo-physical Properties of working fluids
(dp/dT)sat vs. Temperature
© ABB Group June 25, 2014
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Dcrit 2
g l v
Results Flow Regimes Mode 1
Low FR, mostly acts like a thermosyphon with countercurrent annular flow
Mode 2
Transitional flow, thermosyphon operation with liquid bridging, some oscillation
Mode 3
Self sustained pulsation
Mode 4
Over-filled, insufficent vapor fraction to induce pulsation (not seen)
© ABB Group June 25, 2014
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Mode 1
Mode 2
(1/20 speed)
(1/2 speed)
Mode 3
Challenges: selected highlights Integrated microfluidics: Pulsating heat pipes
Minumum RTH for tested conditions: 0.25 °C/W
Similar to values reported in literature
>10x improvement vs. copper
𝑅𝑡ℎ
RTH vs. Applied Flux (Novec 649, 90°)
𝑇𝑒𝑣𝑎𝑝 − 𝑇𝑐𝑜𝑛𝑑 = 𝑄𝑖𝑛
Thick Copper PCB Board
© ABB June 25, 2014
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An Open Loop Pulsating Heat Pipe for Integrated Electronic Cooling Applications Daniel Kearney and Justin Griffin J. Heat Transfer 136(8), 081401, 2014,; doi: 10.1115/1.4027131
© ABB June 25, 2014
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Introduction
Market, ABB and Power electronics research
Application areas and technology drivers
Wide band gap semiconductors
Challenges associated with Power Electronics
Thermal management strategies
Challenges: selected highlights
Future Trends
Future trends Doubled sided cooling
Package redesign
wireless connection of the top contacts of the chips
optimized CTE matching
low-temperature bonding (LTB)—silver sintering of the Chips
Double-sided cooling ⇒ very efficient cooling of the semiconductor chips
ABB 2cool LC presspak Si module
Low-Voltage AC Drive Based on Double-Sided Cooled IGBT Press-Pack Modules Slavo Kicin, Matti Laitinen, Christoph Haederli, Jukka Sikanen, Roman Grinberg, Member, IEEE, Chunlei Liu, Member, IEEE, J.-H. Fabian, and Amina Hamidi IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 48, NO. 6, NOVEMBER/DECEMBER 2012 © ABB Group Month DD, Year
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Future trends Immersion cooling of Power Module •
• • •
Dielectric cooling fluids saturated 3M HFE7100 Rth as low as 0.09 °C/W → 2x double side cooling Local heat transfer → enable effective IGBT paralleling load imbalance Lab demonstrators with mircoporous coating can achieve h≥200,00W/mK
IGBT
Diode
Cu spreader plate with microporous (3M) coating
© ABB June 25, 2014
Two phase cooling review for Power Electronics with Novel coolants, 2011 DOE Vehicle Technologies Program review, G. Moreno NREL | Slide 28
Challenges: selected highlights Integrated microfluidics: jet impingement
Jet impingement directly on the substrate
High HTC & allows direct focused cooling
Cooler material can be an insulator unlike microchannel cooling
Direct Jet Impingement Cooling of Power Electronics, PhD Thesis, R. Skuriat, 2011 © ABB June 25, 2014
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Future trends Integrated PCB Power Electronics
Power chips embedded in PCB
Semikron Skip
© ABB Group Month DD, Year
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Challenges with integration • Increased functionality and performance → increased power density • Increased complexity → holistic solution • Application specific Applications • Switched mode power supplies • Converter systems for eCar, Solar • LED-Systems • Smart power electronics
Future trends Si → SiC packaging trends Gen 1
Gen 3
Gen 2
Wire bond
Planar bond
Single side cooling
Integrated cooling/ planar cooling
Double planar bond
Double sided cooling
Integrated double sided cooling/ Jet/ immersion
ABB Semikron skin
Infineon XT
ABB
Infineon hybrid pack
© ABB June 25, 2014
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Contact details
Dr. Daniel Kearney Research Scientist Power Electronic Integration
ABB Corporate Research Phone: +41 58 586 80 64 email:
[email protected]
© ABB Group June 25, 2014
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