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H Al M t thH. Alan Mantooth
Professor of Electrical EngineeringExecutive Director
NSF Center on GRid-connected Advanced Power Electronic SystemsUniversity of ArkansasUniversity of Arkansas
ARPA-E & EERE Joint Workshop on Power Electronics in Photovoltaic SystemsPower Electronics in Photovoltaic Systems
February 8, 2011
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High Temperature 50 kW Motor Drive
600 V >150 A 250+°C
High Temperature 50 kW Motor Drive
Team
Single Phase Inverter Modules
• APEI, Inc(Circuit Design, Packaging)
• University of Arkansas(Device Modeling, Packaging)
• Rohm, LtdIntegrated gate drive and power stage
Rohm, Ltd.(SiC Devices)
• Sandia National Labs(Energy Storage Systems-Imre Gyuk)
R&D100 AwardR&D100 Award
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R&D100 AwardR&D100 AwardSelected as one of the top 100 global technology
breakthroughs for 2009 by R&D Magazine
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• Demonstration Module 16 SiC DMOS (30A each) half-bridge power topology Integrated power moduleg p High temperature operation (> 250 °C) MCM gate drive boards MMC baseplate
MCM Gate Driver Board
MMC Baseplate
DBA Power Board
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Design ConsiderationsMaterial Selection
• CTE• Thermal Conductivity• Weight• Machinability• Cost• Cost
Geometry• Thickness• Thermal performance
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Thermal ResistanceThermal Resistance vs. Device Dimensions
Thermal Path Optimization• Thermal spreading• Layer thickness• High thermal cond. materials• Void-free solder bondsce
2.5Void free solder bonds
Dominating factors• Die size• Die attach
S b t t ial R
esist
anc
°C /
W)
1
1.5
2
• Substrate ceramic
Current Die Size• 2.4 mm x 4.8 mm• 0.375 – 0.40 °C/W @ 250°C (per die)
Ther
ma (°
0
0.5
1
0 W (p )
Desired Die Size• ≥ 7.5 mm x 7.5 mm• 0.10 – 0.20 °C/W @ 250°C (per die)
0
20 20
1010
0
Die Width Die Length
5
20 20(cm)g
(cm)
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SidewallsThermal-Stress Design• Modeling performed in SolidWorks
Housing Design and SimulationHousing Design and Simulation
g• Maximizes thermal-stress relief features• Incorporates mechanical reinforcement structures
Stress relief and Stress relief and reinforcement features
Housing• Sidewalls frame lid
Lid Frame
• Sidewalls, frame, lid• 275 °C max ambient temperature• Thermal-stress capable design
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Maximum deflection area
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PWM Control Signal Gate Drive Output
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Turn‐on Turn‐off Full period250 °C
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SiC Power Module(Open for Thermal Imaging)
Demonstration System– 300 V DC bus input– 60 V DC motor
60 A peak current
FiltersDC MotorLoad
– 60 A peak current– 15 kHz switching frequency– 250 °C junction
temperature
Voltage Regulator for PWM Control
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Gate DrivePower Supply
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High Temperature SoldersIssues
• Few practical lead free alloys• Gold solders have limitations• Low thermal conductivity• Step soldering
Typical Gold Alloys• 81Au / 19In (487°C)• 96.85Au / 3.15Si (361°C)• 88Au / 12Ge (361°C)
80A / 20S (280°C)• 80Au / 20Sn (280°C)
Typical Lead Alloys• 95Pb / 5Sn (308°C)• 95Pb / 5In (300°C)/ ( )• 92.5Pb / 5In / 2.5Ag (300°C)
Typical Lead Free Alloys• 95.5Sn / 3.8Ag / 0.7Cu (217°C)• 3 5Ag / 96 5Sn (221°C)
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• 3.5Ag / 96.5Sn (221°C)• 3.5Ag / 95Sn / 1.5Sb (218°C)
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BenefitsTransient Liquid Phase (TLP)
• Extremely strong• High temperature stable• Excellent thermal conductivity• Processing temp < Melting temp• Lead Free
Transient Liquid Phase (TLP)
Low Temperature Liquid Phase• Tin, Indium, etc.• Eutectic solder alloys
Issues / Challenges
• Lead FreeHigh Melting Point Base Metal
• Silver, Nickel, Gold, Copper, etc.• Unalloyed for best diffusion• Needs to be relatively thick • Longer processing times
• Material compatibility• Composition variations• Pressure• Thin die metallization
• Needs to be relatively thick
Dissolution and Diffusion• Composition changes• Solidification
C tibl t i l t Thin die metallization• Highly sensitive to contamination• Compatible material systems
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Transient Liquid Phase (TLP)Starting
compositionTarget
Composition
Transient Liquid Phase (TLP)
Low Temperature Liquid Phase• 96.5Sn / 3.5Ag Foil
High Melting Point Base Metal• 100% Silver Foil
PreformsIsostatically laminated• Isostatically laminated
• Sn plated and cut to shape
Assembly Hardware• Precision graphite fixturesg p• Alumina weights
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Diffusion • Ni/Sn TLP bonding samples have
been fabricated Diffusion area
been fabricated• Thermal cycling still underway• Testing/Inspection/Analysis
performed:
Sn-rich area• Cross sectioning followed by
• Optical microscopy• SEM/EDX
• > 100 kg die shear testing results
TLP bond interface /minor
• > 100 kg die shear testing results w/ 1cm2 die
TLP bond interface w/minor voiding
TLP bond TLP bond interface
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(1)Process power substrateAttach power device
(2)Add dielectric
(3)Metal contact
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SiCMOSFET
Power Substrate
Dielectric Material
GateConnect
SiCMOSFET
SourceConnect
Lg RgLg Rg
Ls Rs
Wire Bondless Power Module12 SiC MOSFETs1200V / 150A
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1200V / 150A
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APEI, Inc.SiC Power Modules
CreeSiC MOSFETsSiC Diodes
9”
9”
Key Attributes• 3-Phase• Power ~ 5 kW• 115 V line to line
4”
• 115 V line to line• SiC MOSFETs and diodes• Convection air cooled• 200 °C junction temp operation• 50 kHz switching frequency
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• 50 kHz switching frequency• Mass = 7.25 lbs.• Volume = 365 cubic inches
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Air ConvectionHeat-Sink
APEI Power Modules
PowerBoard
Power
(Cree MOSFETs) InverterFilters
ConnectorsSiCGate Drivers
ControlBoard
17
Board
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Actual Size Comparison
28”Heat Sink Characteristics Commercial Si Inverter APEI, Inc. SiC Inverter Comparison
Power 5 kW 5 kW SameCooling Free Air Convection Free Air Convection SamePeak Efficiency @ Pk Power 95.50% 96.75% APEI increased efficiency 1.25%Power Loss 205 watts 162 watts APEI reduces losses 27%
14”Heat Sink
Size 28.5" x 16" x 5.75" 4.5" x 9" x 9" APEI > 7x smaller volumeVolume 2,622 cubic inches 365 cubic inches APEI > 7x smaller volumeMass 58 lbs. 7.25 lbs. APEI > 8x lighterPk Temperature Capability < 125 °C > 225 °C APEI 2× temperature capability
7”
Heat Sink
APEI, Inc.SiC Inverter
CommercialSi Inverter
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100
97
98
99
Eff
SiC JFET Solar Inverter (10 kHz)
SiC MOSFET Solar Inverter (50 kHz)
94
95
96fice Si IGBT, Fsw=10kHz
Si Solar Inverter (10 kHz)
S C OS So a e e (50 )
91
92
93ncy
SiC, Fsw=10kHz
SiC, Fsw=20kHz
SiC, SV, Fsw=8.5kHz
90
0 2 4 6 8 10 12 14Power (kW)
SiC, Fsw=10kHz, No Filter
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