Additive Manufacturing in Power Module Development · 2018-10-16 · UNCLASSIFIED UNCLASSIFIED The Nation’s Premier Laboratory for Land Forces Additive Manufacturing in Power Module

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UNCLASSIFIEDThe Nation’s Premier Laboratory for Land ForcesUNCLASSIFIEDThe Nation’s Premier Laboratory for Land Forces

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Additive Manufacturing in Power

Module Development

Dr. Lauren Boteler

3D PEIM - June 2018

Dimeji Ibitayo, Morris Berman, Mike Fish, Claude Pullen,

Marco Echeverria (UPRM)

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UNCLASSIFIED The Nation’s Premier Laboratory for Land Forces

ArmyPower Electronics Applications

Power device packaging plays a critical role in enabling these

capabilities

Aerospace

Platforms

Medical

Survivability & Lethality

Army electrical power needs are increasing across the multi-

domain battlefield

↑ Power + ↓ Size = ↑ Temperature

àà Need improved packaging AND cooling

Opportunity Space• New Army application goals are

rendering current power package technologies obsolete

• Packaging is now limiting the performance of power electronics.

• Power Packaging has not changed

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Power Electronics: Cooling Challenge

Problem: Current power electronics packaging needs to

catch up to the device capability.

Current SOA: Ø 200 W/cm2

Ø 10 kVØ 150 °C

Future Target: Ø 1 kW/cm2

Ø >30 kVØ >200 °C

Ø no thermal transient control

Ø Poor reliability at full device rating

Ø transient suppressionØ increased reliabilityØ additive manufacturing

Heat spreading

Integrated 2-phase heat sink

Multi-stage encapsulant

Improved DBC

Die stacking

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100

150

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Packaging Limits SiC Performance

CPM2-1200-0025B• 4.04 x 6.44 mm = 0.260 cm2

• 200 W/cm2 x 0.26 cm2 = 52 W• 1000 x 0.26 = 260W

CPM2-1200-0160B• 2.39 x 2.63 mm = 0.0629 cm2

• 200 W/cm2 x 0.0629 = 12.6 W• 1000 W/cm2 x 0.0629 = 63 W

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5

10

15

20

25

30

35

40

0 2 4 6 8 10 12

200 W/cm2200 W/cm2

1000 W/cm21000 W/cm2

Cont. Current Rating = 98A

Cont. Current Rating = 19A

NOTE: Analysis done at 25°C, challenges much greater at 150°C

*Plots from CREE datasheets

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• Wirebonds- 10-12 mil Al (Au or Cu)

• Power Device- Switches (IGBT/MOSFET) and Diodes- Silicon and/or Silicon Carbide

• Solder- AuSn, SAC, sintered silver

• DBC (Direct Bonded Copper)- Thick ceramic (25mils) sandwiched by

Cu (12 mils)- Ceramic: Alumina or AlN- Alternatives: DBA, AMB

• Heat Spreader- CuMo, CuW, AlSiC, Copper

• Thermal Interface Material (TIM)• Heat Sink/Cold Plate

- Copper, aluminum- Air or liquid cooled

Power Electronics: Standard Package

Heat Sink / Cold Plate

Heat Spreader

DBC

TIM

Power Device

SolderWirebonds

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Challenge Current Solution(s)Packaging limits performance Derate devicesOperating temperature (> 200°C) High temperature materials

Thermal (1 kW/cm2) – drives the size

Integrated cooling, reduce thermal resistance, PCMs, higher thermal conductivity materials, improved heat sinks

Break-down voltage (up to 25 kV) Increase package size, thicker/improved dielectrics

Inductance Snubbers, eliminate wirebonds, intelligent placement of chips on board

Reliability: DBC Dimple edges, DBAReliability: Wirebonds Eliminate wirebondsReliability: Large area contacts DBC, CTE matched materials (TiW, CuMo),

multiple DBC boards, stress-relieving TIMS

dtdiLV =

Power Electronics: Packaging Challenges

All of these challenges are exacerbated by increased temperature and/or temperature non-uniformity.

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1. Co-Design/Co-Engineering– Consider the electrical, thermal and mechanical domains during design

2. Transient Thermal Mitigation– Designing for transient thermal loads instead of steady state to reduce

overdesign3. High Voltage Design and Packaging

– New high voltage devices (>15kV) create the need for advanced packaging4. Additive Manufacturing

– Custom power modules– New power module architectures

Key Enabling Capabilities for Future Power Modules

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Advantages:• Cost-effective and time-efficient for low-volume production• Freedom of design• Complex geometries with internal features• Customized products • Advanced material properties and functionality

What is Additive Manufacturing?

ASTM Definition: Process of joining materials to make objects from three-dimensional (3D) model data, usually layer by layer, as opposed to subtractive manufacturing methodologies.

Courtesy of Stratasys Direct Manufacturing

Current Challenges/Limitations:• Limited materials available (e.g. pure copper work in progress)• Surface finish out of the machine not ideal for many applications• Geometries must take into account support design and powder removal• Insufficient repeatability and consistency in produced parts• Design methods to aid designers in defining and exploring design spaces

enabled by AM

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Vision

Additive Manufacturing for Power Packaging

Packaging Specific Characterization of

Materials & Processes

Additive Manufacturing-Enabled Design

Methods

Integrated Function Packaging

Components

Research Objective: Develop advanced additive manufacturing materials and processes to enable low quantity and low cost production of improved SWaP-C power packaging.

• Cost-effective for low-volume production

• Disruptive design space• Customized power substrates • Increased power density • Reduced inductance

• Thermal transient suppression• Improved reliability• Functionally graded materials• Complex internal features• Integrated substrate - heatsink

Benefits:

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Additive Manufacturing for Power Electronics

Option 1: Improve “Standard” Power Module

Option 2: Additive Manufacturing-Enabled Design Methods

AM can enable both incremental improvements in power electronics packaging as well as revolutionary improvements.

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Additive Manufacturing Solutions

Problem: Host of power packaging challenges limiting device performance Packaging Challenge Additive Manufacturing Solution(s)

Electrical: Parasitic inductance

Integrated Gate DriverWirebondless Packaging (reduced parasitics)

Electrical: High voltage Cold Spray Power Substrates(customized, thick ceramic)

Thermal: High power density, thermal transient suppression

Integrated HeatsinkThermal Ground Plane Heat Spreader Additively Manufactured HeatsinkPhase Change Materials(reduced thermal resistance, enhanced heat transfer, thermal transient suppression )

Operating temperature (> 200°C)

High temperature materials

Reliability: DBC substrates Cold Spray (eliminate DBC)

Reliability: Die attach & large area bonds

Advanced Package StructuresIntegrated Heatsink

Reliability: Wirebonds Wirebondless Packaging

Additive Manufacturing offers solutions to many power packaging challenges

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Cold Spray

Cold spray directs a fine stream of high velocity metal particles onto solid surfaces using a robotically controlled jet.

CGT Kinetiks 4000® high-pressure cold spray system

ARL hand-held cold spray system

Advantages for Power Packaging:• Room temperature process

• Reduced stress

• Graded structures possible (smoothly vary CTE)

• Enabling technology for Co-design approach

(i.e. customized substrate for specific requirements)

• Does not require chemical etching

• Capable of writing copper lines from 0.1 to 10 mm

in width

Common Applications:• Metal-on-metal

• Protective coatings (wear,

corrosion, etc.)

• Repair material

POC: Dimeji Ibitayo, [email protected], 301-394-5514

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R. Drehmann et. al, “Interface Characterization and Bonding of Cold Gas-Sprayed Al Coatings on Ceramic Substrates,” Journal of Thermal Spray Technology, 2015, 24(1-2), p 92-99.

B.Wielage et. al, “New Method for Producing Power Electronic Circuit Boards by Cold-Gas Spraying and Investigation of Adhesion Mechanisms,” Surface & Coatings Technology, 2010, 24(1-2), p 1115-1118.

• Institute of Materials Science/Technology (Germany)• Both physical and chemical interactions between the

metallic coating and the ceramic substrate appear to play a role in adhesion strength.

• Proven success with aluminum interlayer and/or substrate heating.

• Cold spray copper coatings successfully deposited on thermally sprayed aluminum nitride

What research is being/has been already done in the field and by whom?

K.-R. Ernst, J. Braeutigam, F. Gaertner, and T. Klassen, “Effect of Substrate Temperature on Cold-Gas-Sprayed Coatings on Ceramic Substrates,” Journal of Thermal Spray Technology, 2014, 22 (5-6), p 422-432.

ARL Goal: Application-specific additively manufactured substrate to reduce over-design and improve reliability.

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Cold Spray Trials

“Copper sponge” deposit from handheld low-pressure

cold spray

Damaged 0.080” AlN tile with delaminated copper coating

Path forward:• High pressure deposition on oxidized AlN substrate• Calculate maximum allowable impact energies based

on fracture toughness of ceramics to better inform coating experiments and prevent substrate damage

• Mount ceramic substrates on compliant backing• Increasing the substrate temperature to enhance

adhesion strength• Intermediate aluminum bond coat layer on AlN to

promote copper adhesion• Partner with Univ of Puerto Rico, Northeastern Univ

Cold Spray modeling to understand the guide

experiment - UPR

Adhered copper onto AlN

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Thermal Ground Plane (TGP) Heatspreader

Goals:• Transition DARPA Thermal Ground Plane (TGP) technology to power electronic temperatures

- Improved heat spreading capability- Higher temperature limits (~200°C), heat fluxes- Overcome material, fluid, stress issues

Status:• Partnered with ACT, Inc., developing metal ceramic (DBC) vapor chamber

• InterPACK2017 publication: highest heat flux (>500 W/cm2) demonstration of low CTE vapor chamber directly integrated to backside of DBC showing 40-50°C temp at high power

• Technology transition: Wolfspeed presently investigating technology in one of their commercial modules Device under thermal evaluation

(a) Solid CuMo, (b) TGP heating at 520 W/cm2

(a) (b)

219°C169°C

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Sequential• Not optimized,

overdesigned• Integration is difficult• Minimal

understanding of tradeoffs

Current & New Design Methods

Electrical Mechanical Thermal

Parametric Analysis Methodology

16X Reduction in Size & Weight

Army Design Goal: Improve SWaP-C & Reliability

Co-Design/Co-Eng

Multiphysics Module Design

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Build a Single Unit Cell

Half-bridge module (building block of most power circuits)

3 Phase Voltage Source Inverter (VSI) Full Bridge isolated buck converter

IGBT and diode are packaged in a series (vs. anti-parallel) to minimize inductance path (Tolbert, ORNL, 2010)

Boteler et al. IWIPP 2017

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Multi-Functional Components (MFCs)

Single-Half Bridge:

Mechanical Electrical Thermal

stacked devices reduce parasitic inductance

fewer wirebonds

small area bonds reduce CTE mismatch fluid ports

for active cooling

internal heat sinks

thermal fins also electrical contacts

Positive Bus

Negative Bus

Midpoint

no DBCincreased power density

Co-Design Objective: Eliminate single

function components (ex. wirebonds, heat

sinks, solid dielectrics)

KEY enabling feature: Multi-functional components (MFC)• MFC acts as electrical, thermal and mechanical attachment consecutively • Eliminating solid dielectrics and using the dielectric fluid as both the coolant and dielectric• Exterior plastic housing acts as both the heat sink enclosure and the module housing

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Additive Manufactured Power Module

Thermocouple

SourceGate

Stereolithographic Resin Additive Manufacturing Copper AM MFCs

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Full 3 Phase Inverter

~8X Reduction in Size and Weight!5-10X reduction in package thermal resistivity

Fluid Holes

Rth = 0.25 Kcm2/W

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Traditional thermal improvement focuses on steady-state thermal resistance

Traditional thermal improvement

Enhanced power thermal stack(Substrate Integrated Cooling)Standard power thermal stack

Integratedsubstrate

Solder Power Device hAAkxR

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Package layer thermal conduction

Heat sink /fluid convection

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3x peak temp.

response

Steady state package improvements may not improve transient thermal performanceReduction in package thermal resistance (Rth)

→ reduced thermal capacity (Cth)→ drops thermal time constant (! =RthCth)

→ increased temp. during fast pulses

Want to increase Cth while maintaining low Rth

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Transient Thermal Management

• OBJECTIVE: Design thermal and packaging solutions for transient loads− Metallic Phase Change Materials directly in contact with heated chip

Unsteady traction driveADS Environmental Control Units

µsec msec seconds hours

short pulse long pulse / pulse trains surges diurnal

Directed energy

6

Significant temperature reduction during experimentsDeveloping robust modeling tools

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1. Co-Design/Co-Engineering– Consider the electrical, thermal and

mechanical domains during design2. Transient Thermal Mitigation

– Designing for transient thermal loads instead of steady state to reduce overdesign

3. High Voltage Design and Packaging – New high voltage devices (>15kV) create

the need for advanced packaging4. Additive Manufacturing

– Custom power modules – New power module architectures

Conclusions/Path Forward

Holistic approaches to electronic design to enable significant SWaP improvement in various Army systems

[email protected]

Documents

Additive Manufacturing in Power Module Development · 2018-10-16 · UNCLASSIFIED UNCLASSIFIED The Nation’s Premier Laboratory for Land Forces Additive Manufacturing in Power Module