Cooling of Next Generation Power Electronics: Trends

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Feb 1, 2012 - Integrated Systems: Power chips & .... Heat spreader baseplate. (AlSiC) ... An Open Loop Pulsating Heat Pipe for Integrated Electronic Cooling ...
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

| Slide 2

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

| Slide 10

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

| Slide 14

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

• • • • • © ABB Group Month DD, Year

| Slide 15

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

| Slide 19

Challenges: selected highlights Integrated microfluidics: Pulsating heat pipes qout

qin • • • • • • © ABB June 25, 2014

| Slide 20

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

| Slide 25

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

| Slide 26

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

| Slide 27

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

| Slide 29

Future trends Integrated PCB Power Electronics

Power chips embedded in PCB

Semikron Skip

© ABB Group Month DD, Year

| Slide 30

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

| Slide 31

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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