NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Thermal Management of Power Semiconductor 

Packages – Matching Cooling Technologies with 

Packaging Technologies

IMAPS 2nd Advanced 

Technology Workshop on 

Automotive Microelectronics 

and Packaging

Kevin Bennion

Gilbert Moreno

Dearborn, MI

April 27, 2010

NREL/PR-540-48147
National Renewable Energy Laboratory Innovation for Our Energy Future

Acknowledgements

2

• Jason Lustbader, National Renewable Energy laboratory 

(NREL)

• Advanced Power Electronics and Electric Machines 

Benchmarking, Oak Ridge National Laboratory (ORNL)

Funding Provide by:

Susan Rogers, Office of Vehicle Technology, U.S. 

Department of Energy
National Renewable Energy Laboratory Innovation for Our Energy Future

Objective

1. Efficient heat transfer technologies can 

enable increased power density and 

specific power.

2. Thermal management is a path to 

reduce cost and maintain robust 

operation.

3. Thermal management should not be an 

afterthought but should involve an 

integrated systems approach.

4. Cost-effective solutions require 

integration of capabilities for cooling, 

packaging (materials/geometry), and 

reliability prediction.

3

Power 

Electronics

Module

Battery

Electric

Machines

Other

Toyota Camry - 2007

Source: Technology and Cost Report of the 

MY2007 Toyota Camry - ORNL 
National Renewable Energy Laboratory Innovation for Our Energy Future

Relevance of Thermal Management

4

Thermal management directly relates to improvements in cost, 

power density, and specific power.

Impacts: Lower cost, volume, and weight

“Easy ways to increase output power are paralleling more silicon chips and/or step-up the 

die size to increase current capacity. But this strategy is unaffordable in terms of both 

increased chip cost and packaging space.”

Concern: Heat

“The most significant concern for increasing current is intensified heat dissipation.”

Source: Yasui, H., et al, “Power Control Unit of High Power Hybrid System” – EVS23

Prius PE MY 2004 Camry PE MY 2007 LS 600h PE MY 2008

Double-sided 

Cooling
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Outline

Background

• Department of Energy’s Advanced Power Electronics and 

Electric Machines (APEEM) activity.

• Thermal management for power electronics cooling.

Problem

• Quantify trade-off interaction between packaging configuration 

and cooling technology.

• Identify effective packaging and cooling combinations.

Approach

Results

5
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Background

DOE’s Advanced Power Electronics and Electric Machines (APEEM)

6
National Renewable Energy Laboratory Innovation for Our Energy Future

Background

7

APEEM

Thermal Control Subsystem

integration, performance, reliability

APEEM

Technology

Development

Potential Thermal Management Technologies

Advanced 

Vehicle 

Systems

Performance Targets

System Impacts

• Heat load

• Heat flux

• Thermal 

resistance

• Cost 

• Weight

• Volume

• Efficiency

• Robustness

• NREL Advanced Power Electronics Thermal Overview

Industry 

Collaboration

Research 

Community
National Renewable Energy Laboratory Innovation for Our Energy Future

Background

8

• NREL Advanced Power Electronics Thermal Focus Areas
National Renewable Energy Laboratory Innovation for Our Energy Future

Background

9

• Defines thermal requirements

• Links thermal technologies to electric 

traction drive systems
Problem

National Renewable Energy Laboratory 10 Innovation for Our Energy Future

How do developments in cooling 

impact APEEM technology 

selection?

How do developments in 

APEEM technologies influence 

cooling technology selection?

APEEM

Thermal Control Subsystem

integration, performance, requirements

APEEM

Technology

Development

Potential Thermal Management 

Technologies

Advanced 

Vehicle 

Systems

HEATER

δt

Stagnation 

Zone

Wall Jet Zone

d

Ud ,Tl

L: heater diameter

S

Twall
National Renewable Energy Laboratory Innovation for Our Energy Future

Approach

11

Heat Transfer & Fluid 

Flow Characterization

1

Cooling 

Technologies

Cooling 

Performance

Experimental Correlations, 

CFD Results, & Analytical

Heat Exchanger 

Characterization

Effectiveness – NTU Method

Fins & Jets

2

3

System Performance Trade-offs

10

100

1000

0.001 0.010 0.100 1.000 10.000

IGBT Flux (W/cm2)

Heat Exchanger Thermal Resistance, Rhx (K/W)

Heat 

Exchanger 

B

Heat 

Exchanger 

A

Quantify interaction between package configuration and cooling technology on total 

thermal performance. 
National Renewable Energy Laboratory Innovation for Our Energy Future

Approach

12

Heat Transfer & Fluid 

Flow Characterization

1

Cooling 

Technologies

Cooling 

Performance

Experimental Correlations, 

CFD Results, & Analytical

Heat Exchanger 

Characterization

Effectiveness – NTU Method

Fins & Jets

2

3

System Performance Trade-offs

3

2

1

PE Package Thermal 

Characterization

3D Package 

Configuration

3D Parametric 

FEA

Thermal 

Characterization

Heat Flux 

vs. 

Heat Exchanger Thermal 

Resistance

10

100

1000

0.001 0.010 0.100 1.000 10.000

IGBT Flux (W/cm2)

Heat Exchanger Thermal Resistance, Rhx (K/W)

Package A

Package B

Quantify interaction between package configuration and cooling technology on total 

thermal performance. 
National Renewable Energy Laboratory Innovation for Our Energy Future

Approach

13

Heat Transfer & Fluid 

Flow Characterization

1

Cooling 

Technologies

Cooling 

Performance

Experimental Correlations, 

CFD Results, & Analytical

Heat Exchanger 

Characterization

Effectiveness – NTU Method

Fins & Jets

2

3

System Performance Trade-offs

3

2

1

PE Package Thermal 

Characterization

3D Package 

Configuration

3D Parametric 

FEA

Thermal 

Characterization

Heat Flux 

vs. 

Heat Exchanger Thermal 

Resistance

10

100

1000

0.001 0.010 0.100 1.000 10.000

IGBT Flux (W/cm2)

Heat Exchanger Thermal Resistance, Rhx (K/W)

Package A

Package B

Performance

Improvement

Required heat exchanger improvement 

for equivalent performance gain.

Quantify interaction between package configuration and cooling technology on total 

thermal performance. 
National Renewable Energy Laboratory Innovation for Our Energy Future

Approach

14

Applied process to range of package configuration examples approximated 

from in-use commercial packages with different geometries.

Semikron SKM Toyota Camry Toyota Prius 2004

Semikron SKAI Lexus LS 600h

IGBT and diode pair
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Approach

15

Baseline Package Configurations

Layer

SKMSKAIPriusCamryLs 600H

IGBT/Diode (Si) x x x x

See referenced paper below

Solder x x x x

Cu x x x** x**

Substrate AlN NA* x x x

Al2O3 x NA NA NA

Cu x x x x

Solder x NA x x

Heat Spreader Cu x NA NA NA

Cu-Mo-Cu NA NA x x

TIM x x+ x x

Heat Sink x x x x

Cooled Surface Footprint Area: [cm2] 15.34 3.90 16.86 7.68 15.00++

* Included additional model variation with AlN.

+ Modeled with reduced thermal interface material thickness of 0.05 mm.

** Assumed copper metallization layer.

++ Listed area is for one side of the package, and it is the same on each side of the package.

Reference:

K. Bennion and K. Kelly, “Rapid Modeling of Power Electronics Thermal Management Technologies,” IEEE Vehicle Power 

and Propulsion Conference, Sept. 7-11, 2009.
National Renewable Energy Laboratory Innovation for Our Energy Future

Results

16

* Sample single-sided and double-sided total thermal resistance. (Source: Y. Sakai, H. Ishiyama, and T. Kikuchi, “Power control unit for high power 

hybrid system,” SAE 2007 World Congress, Detroit, MI, April 16-19, 2007, SAE Paper 2007-01-0271.)

** Sample cooling performance. (Source: I. Mudawar, "Assessment of high-heat-flux thermal management schemes," IEEE Transactions on 

Components and Packaging Technologies, vol. 24, no. 2, pp. 122-141, June 2001.
National Renewable Energy Laboratory Innovation for Our Energy Future

Results

• All curves flatten as the heat 

exchanger performance 

improves (R’’

h,h-a decreases).

• Package becomes thermal 

limitation.

• Difference in total thermal 

performance (R’’

th,j-a) is affected 

by the footprint area available 

for cooling.

• Method for comparing 

alternative heat exchanger 

technologies and package 

configurations.

17

* Sample single-sided and double-sided total thermal resistance. (Source: Y. Sakai, H. Ishiyama, and T. Kikuchi, “Power control unit for high power 

hybrid system,” SAE 2007 World Congress, Detroit, MI, April 16-19, 2007, SAE Paper 2007-01-0271.)

** Sample cooling performance. (Source: I. Mudawar, "Assessment of high-heat-flux thermal management schemes," IEEE Transactions on 

Components and Packaging Technologies, vol. 24, no. 2, pp. 122-141, June 2001.
National Renewable Energy Laboratory Innovation for Our Energy Future

Results

18

100

1,000

10,000

1 10 100 1,000 10,000

R" th, j-a (mm2 -K-/W)

R"th, h-a (mm2 -K/W)

 

Camry

Prius

SKM

SKAI

Lexus (d)

• Weight the total thermal 

performance (Rth,j-a) by the total 

footprint area available for 

cooling.

• Curves collapse onto a single 

curve as the heat exchanger 

resistance increases.

• Removes effect of different 

package footprint areas.
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Results

19

Baseline Direct Cooled 

Baseplate

(DCB)

Direct 

Cooled 

DBC 

(DCD)

Package geometry, material, 

and cooling trade-offs
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Results

20

Baseline

Direct Cooled 

DBC (DCD)

Baseline 

• At low Rth,h-a , the separation between 

AL203 and AlN package resistance is more 

significant.

• Trade-off between material cost and heat 

exchanger performance cost.

• At about 100 mm2-K/W, switching to AlN 

would have a similar benefit to a 10X 

heat exchanger improvement.

Direct Cooled DBC (DCD)

• At high Rth,h-a , the cooling area footprint 

and heat exchanger resistance dominate 

thermal performance.

• As the cooling technology improves, the 

thermal characteristics of the package 

become more important.
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Results

21

10

100

1,000

10,000

1 10 100 1,000 10,000

R" th, j-a (mm2-K/W)

R"th, h-a (mm2 -K/W)

 

Al2O3

AlN

open symbol: Baseline

gray symbol: DCB

black symbol: DCD

• Weight the total thermal 

performance (Rth,j-a) by the total 

footprint area available for 

cooling.

• Curves collapse onto a single 

curve as the heat exchanger 

resistance increases.

• Removes effect of different 

package footprint areas.

• Highlights impact of package.
National Renewable Energy Laboratory Innovation for Our Energy Future

Results

22

1.00

1.25

1.50

1.75

2.00

1 10 100 1,000 10,000

Rth, j-a (Al

O2 3) /

Rth, j-a (AlN) 

R"th, h-a (mm2 -K/W)

Baseline

DCB

DCD
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Results

23

1.00

1.25

1.50

1.75

2.00

1 10 100 1,000 10,000

Rth, j-a (Al

O2 3) /

Rth, j-a (AlN) 

R"th, h-a (mm2 -K/W)

Baseline

DCB

DCD

• The impact of a material with 

improved thermal conductivity 

depends on the package 

configuration and heat 

exchanger performance.

• The cost/benefit trade-off 

improves for more aggressive 

cooling and packages with 

fewer thermal bottlenecks.

• Relationship between package 

thermal performance and 

cooling technology can lead to 

a more expensive system than 

necessary if the relationship is 

not used properly.
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Results

24

0.01

0.10

1.00

1 10 100 1,000 10,000

R th, j-a (K/W)

R"th, h-a (mm2 -K/W)

 

Lexus

Camry (DCD)

0.203*

0.452*

* Sample single-sided and double-sided total thermal resistance. (Source: Y. Sakai, H. Ishiyama, and T. Kikuchi, “Power control unit for high power 

hybrid system,” SAE 2007 World Congress, Detroit, MI, April 16-19, 2007, SAE Paper 2007-01-0271.)

Matching package geometry 

and cooling technology
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Results

25

0.01

0.10

1.00

1 10 100 1,000 10,000

R th, j-a (K/W)

R"th, h-a (mm2 -K/W)

 

Lexus

Camry (DCD)

0.203*

0.452*

* Sample single-sided and double-sided total thermal resistance. (Source: Y. Sakai, H. Ishiyama, and T. Kikuchi, “Power control unit for high power 

hybrid system,” SAE 2007 World Congress, Detroit, MI, April 16-19, 2007, SAE Paper 2007-01-0271.)

• To maximize the thermal 

performance, the package and 

heat exchanger technology 

should be investigated together.

• Identify appropriate cooling 

methods for a given package 

technology.

• Identify appropriate packaging 

options for a given cooling 

approach.

Matching package geometry 

and cooling technology
National Renewable Energy Laboratory Innovation for Our Energy Future

Conclusion

26

• Thermal management plays an important part in the cost 

of electric drives in terms of power electronics packaging.

• Cost-effective solutions require an appropriate balance 

between package and thermal management design.

• Appropriate cooling technology depends on

• Package application

• Reliability

• Integration of capabilities for cooling, packaging

(materials/geometry), and reliability prediction provide a 

system view of technology developments.