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© 2010 New strategies for thermal management of high power modules APEC 2011 Fort Worth, TX 9 March 2011 Jeff Perkins Brice Le Gouic
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Page 1: Fort Worth, TX - DoYouBuzz

© 2010

New�strategies�for�thermal�management� of�high�power�modules

APEC�2011

Fort�Worth,�TX

9�March�2011

Jeff�PerkinsBrice�Le�Gouic

Page 2: Fort Worth, TX - DoYouBuzz

© 2010 • 2

Module�structure Origin�of�issues�for�high�temperature

Die�attach Interconnection Gel�filling Substrates�attach

Page 3: Fort Worth, TX - DoYouBuzz

© 2010 • 3

Module�structure Example�for�high�temperature�operating

Thermal�cycling�weaken�the�attach�if�Coefficient�of�Thermal�Expansion�(CTE)�is�different�for�each�layer.�This�is�the�

principal�issue�of�high�temperature

ChallengesÎ Need�to�match�the�CTE�of�each�layerÎ Good�thermal�conductivity�requiredÎ High�melting�point

Attach�cracks�

after�thermal�

cycling

Wire�deͲbonding�

after�thermal�

cycling

Page 4: Fort Worth, TX - DoYouBuzz

© 2010 • 4

Die�attach Soldering,�the�historical�method

Soldering�is�a�fast,�cheap�and�easy�process–

They�use�a�paste�or�a�gel�for�soldering

Historically,�it�is�an�alloy�of�Tin�(Sn)�and�Lead�(Pb)�that�can�

handle�

But��Pb�is�to�be�abandoned�due�to�RoHS:

ÎPbͲfree�solution�is�Sn/Ag�(Tin/Silver)�soldering

ÎSoldering�is�not�suitable�for�high�temperature�or�multiple�steps

max�is�220°C

Page 5: Fort Worth, TX - DoYouBuzz

© 2010 • 5

Die�attach TLPB,�melting�phases�at�liquid�state�

Transient�Liquid�Phase�Bonding�(TLPB)–

We�stack�layers�of�Sn�and�Cu,�and�the�first�melts�and�diffuse�through�the�

other.�Result�is�an�alloy�of�Cu/Sn�with�progressive�percentage.�This�

method�is�also�called�Eutectic�soldering�

T°m

(Cu/Sn)�>�400�°C

Used�by�Infineon�in�its�.XT�modules�in�2010

Page 6: Fort Worth, TX - DoYouBuzz

© 2010 • 6

Sintering–

An�Ag�(Silver)�powder�is�compressed�at�high�temperature

Compression�of�30�to�40�MPa�at�250°C

Process�is�long,�but�cheap�:•

High�pressure

Powder�of�micro�particles

Reliable�and�already�at�mass�production

Used�by�Semikron�since�2008

Die�attach Sintering

30�

MPa

30�

MPa

250°

C Die

Ag�powder

DBC

Page 7: Fort Worth, TX - DoYouBuzz

© 2010 • 7

Die�attach Nanoparticle�sintering�is�under�investigation

Nanoparticle�sintering–

Same�principle�as�Ag�micro�particles�sintering

Using�nano�size�particles�allows�a�better�result�with�a�simpler�

process�:•

Temperature�is�much�lower�Î down�to�20°C

Pressure�and�time�are�also�reduced�Πfaster�thus�cheaper�process

This�technology�is�still�at�R&D�development•

Issues�from�the�migration�of�Ag�particles�at�high�temperature�still�

need�to�be�overcome

TimeͲtoͲmarket�:�2012

Page 8: Fort Worth, TX - DoYouBuzz

© 2010 • 8

Die�attach StateͲofͲtheͲart�&�developments�status

CTEThermal�

Conductivity

Processing�

temperature

Melting�point(Max.�Use�

temp.)

Mass�

production

Cost Key�players

SolderingLeadͲtin

28µm/mK 70�W/K.m 217°C <�183°C

Used�for�all�

low�

temperature�

applications

LowAll�semiconductor�

manufacturers

SolderingLead�free

~20µm/mK 260°C 225°CMore�and�

more�used����Æ RoHs

LowAll�semiconductor�

manufacturers

TLPB Undisclose Undisclose ~260°C~�400°C�for�

Cu/Sn

Q4�2010 High

SinteringMicro�

powder

19�µm/mK 250�W/K.m 250°C<�961°C�for�

Ag�powder

Since�2008 Low

SinteringNano�

powder

Unknown 290W/K.m ~275°C<�961°C�for�

Ag�powder

2012 Very�

low

Others…

Page 9: Fort Worth, TX - DoYouBuzz

© 2010 • 9

Interconnection Today’s�solutions

Wedge�bonding�and�ball�bonding�are�mostly�used�today–

Not�suitable�for�high�temperature�and�high�current

One�side�cooling�only

For�high�temperature,�2�types�of�solutions:–

Soldering�based�solutions•

Evolution�of�the�soldering�with�addition�of�a�top�DBC�for�

connections

Metallization�based�solutions•

Use�of�metallization�process�to�cover�the�dies�and�connect�at�the�

same�time�(Vias)

Wedge��

bonding

Ball��bonding

Page 10: Fort Worth, TX - DoYouBuzz

© 2010 • 10

Thermal�dissipation

Impact�of�powerͲmodule�packaging�type�

0 20 40 60 80 100 120 140 160 180 200

Direct�cooling�with�µͲchannel�doubleͲface

Direct�cooling�with�µͲchannel� singleͲface

Wire�bonding�+�water�cooling

Wire�bonding�+�oil�cooling

Wire�bonding�+�forced�convection

Wire�bonding�+�thermogravity�heatͲpipe

PressͲpack�+�pool�boiling

Wire�bonding�+�natural�convection

Impact�of�packaging�type�upon�thermal�dissipation�(W/cm²)

Page 11: Fort Worth, TX - DoYouBuzz

© 2010 • 11

Interconnection StateͲofͲtheͲart

Soldering�based•

Solder�bump�:–

Bumper�realize�3D�interconnection�in�the�

module

Developments�by�Alstom�for�rail�traction

Mass�production�is�envisioned

Metal�post�interconnection:–

Die�in�sandwich�between�DBCs

Bottom�attach�is�classic�soldering

Top�is�an�array�of�metal�post�for�connection

Direct�solder:–

Die�is�soldered�on�bottom�and�top

Classic�soldering�is�used�on�each�side

Dimple�array:–

Use�dimple�on�copper�plate�to�operate�

connection�with�plots�from�the�dies

No�mass�production�possible

Metallization�based

Embedded�power:–

Dies�are�in�a�ceramic�as�a�mechanical�support

Metallization�is�done�over�this�assembly�for�

interconnection

Developed�by�CPES

Time�to�market�is�to�be�confirmed�:�2012

May�be�too�expensive�for�mass�production

Power�overlay:–

Interconnection�with�metallization�using�

masks�and�photolithography

Developed�by�GE

Time�to�market�is�to�be�confirmed:�2012

May�be�too�expensive�for�mass�production�

Page 12: Fort Worth, TX - DoYouBuzz

© 2010 • 12

Interconnection Focus�on�power�overlay

Power�overlay�–

General�Electric:

Wirebondless�technology�

characteristics:•

Double�side�cooling

Higher�power�density�

Lower�inductance

Lower�contact�resistance

Copper�metallizationDielectric

Process�steps:ͲDie�attach�on�a�support�with�

protection�filmͲ RIE�etchingͲ

Metallization�+�electro�

deposition

Manufacturability�is�complex

Reliability�has�to�be�

improved

Page 13: Fort Worth, TX - DoYouBuzz

© 2010 • 13

Parylene�HT�vs.�Gel�solution Filling�of�power�modules

Parylene�HT•

Air�fills�the�empty�parts�of�the�module

Achieve�400°C

Only�one�company�propose�it�:�Specialty�coating�systems

Parts�must�be�sent�to�the�company�to�be�coated�Πhighly�protected�process

Gel Manufacturer Dielectric�strength�(kV/mm) CTE�(ppm) Max�temperature

Elastosil�RT�745S Wacker 23 N/A

Nusil�R2188 Nusil�silicone 17.7 N/A 240°C

Sylgard�567 Dow�corning 21 300 200°C

Gel�solution

Silicone�gel�max�temperature�is�200°C

There�are�not�many�solutions�to�overcome�the�

issue�for�now

Page 14: Fort Worth, TX - DoYouBuzz

© 2010 • 14

Baseplate� DBCͲBaseplate�characteristics

Material CTE(ppm/°C)

Thermal�

conductivity�

(W/mK)

ASP�($)

DBC

Al2

O3 6.5 25 $25Ͳ$30

(19x14cm²)

AlN 4.5 200 $100Ͳ$120

(19x14cm²)

BeO 8 250

Baseplate

Cu 17.8 398 у$15(19x14cm²)

AlSiC 6.5�– 9 170�– 200� у$30(19x14cm²)

CuW6.5�–

8.3

180�– 200�

CuMo 7�– 8 160�– 170�

Si3

N4 3.4 70�Ͳ

90

Alloys�characteristics�

depends�of�the�

percentage�of�each�

metal�in�the�alloy

Challenge�is�to�find�a�

tradeͲoff�between�

thermal�conductivity�

and�CTE,�for�a�pair�of�

DBCͲSubstrate.

Weight�can�also�be�part�

of�the�equation

These�are�prototypes�ASP’s.�Mass�production�price�depends�on�series�size.

Page 15: Fort Worth, TX - DoYouBuzz

© 2010 • 15

Baseplate� Future�evolutions

New�trends�are:–

Improving�the�heat�transfer�and�the�efficiency�of�the�coldplate•

Example:

The�integration�of�cooling�inside�the�baseplate�Î AlSiC�pinͲfin

Eliminating�layers�and�reduce�thickness�between�the�die�and�the�cooling�

system•

Example:

Removing�of�the�baseplate�ΠDBC�is�fixed�to�the�cooling�system

Evolution�will�come�from�integrated�liquid�cooling�solutions:–

Porous�materials–

MicroͲchannel�heatͲsinks�(GE)–

ForcedͲpath�cooling�(Danfoss�shower�power)–

Integrated�AlSiC�cooling�pinͲfin–

Page 16: Fort Worth, TX - DoYouBuzz

© 2010 • 16

Powerex�SiC�1200V/100A�MOSFET Case�study

Powerex�has�released�a�1200V�100A�SiC�Mosfet�module�2009

Certified�operation�@200°C

It�has�been�developed–

Using�CREE�SiC�dies

For�Army�research�laboratory

Page 17: Fort Worth, TX - DoYouBuzz

© 2010 • 17

Powerex�SiC�1200V/100A�MOSFET Case�study

The�technology�inside�Gen.�II

Case:

Torlon�® polyimide�material�

up�to�260°C

Gel:�Wacker�RT745S�that�resist�at�

250°C�operation

Dies:

CREE�4HͲSiC�MOSFETS�20A�by�

5�&�JBS�diodes�50A�by�3

Solder:

95Pb5Sn�or�80Au/20Sn�

(unsure)

Baseplate:

AlN�DBC�with�a��CTE�of�

4.5�ppm/K

Cooling:�Copper�fins�soldered�

directly�to�DBC DBC�pattern�is�a�key

Comparison�between�

old�and�new�pattern

Page 18: Fort Worth, TX - DoYouBuzz

© 2010 • 18

Powerex�SiC�1200V/100A�MOSFET Case�study

Issues�to�reach�250°C

Gel�filling�:�Powerex�tested�different�

solutions,�and�they�still�face�issues�at�250°C�

junction�temperature

Die�size�:�To�handle�100A,�they�had�to�

increase�the�die�size,�which�result�in�more�

mass�manufacturing�problems.�Finally�

56mm²

MOSFETS�and�32mm²

diodes

DBC�attach�:�Temperature�cycling�make�

delaminations�to�appear�when�using�AlN.�

Other�materials�are�under�investigation

Cracked�gel�

after�T°

cycling

Die�size�

comparison�

between�1st

and�2nd

Gen.

Delamination�

on�AlN��DBC

Page 19: Fort Worth, TX - DoYouBuzz

© 2010 • 19

THERMAL�MANAGEMENT� AT�SYSTEM�LEVEL

Page 20: Fort Worth, TX - DoYouBuzz

© 2010 • 20

Cooling�systems�relative�cost in�overall�Silicon�power�modules

Breakdown�over�a�complete�power�module:�inverter,�converter….Cooling�systems�include:�fans,�heatͲsink,�radiators

Page 21: Fort Worth, TX - DoYouBuzz

© 2010 • 21

Current�setup�of�cooling�in�inverters

PV�inverters

Example�of�a�large� size�PV�inverter�

from�TMEIC:–

The�overall�inverter�

is�used�as�an�air�

circuit:�no�fans�is�

needed�in�this�

configuration

Î cold�air�is�coming�up�and�in�and�hot�air�is�coming�out�by�the�top�of�the�structure

Page 22: Fort Worth, TX - DoYouBuzz

© 2010 • 22

Impact�of�operation�T°

on�thermal�management

Motor�drives�in�industry�environment

Thermal�management:–

Several�possible�utilizations�of�inverters�lead�to�different�working�

temperature�conditions:•

Conveyors�are�in�movement�and�can�cool�by�themselves

Automation�systems�are�often�working�with�fans

Foundries

Depending�on�the�working�temperature,�different�cooling�solutions�exist:

Working�

temperature

<�20°C 20�to�55°C 55�to�95°C >�95°C

Cooling�solution Aluminum�heat�sinkNo�fan

Aluminum�heat�sink1�optional�fan

1�fan 2�fans�minimumLiquid�cooling�

system

Page 23: Fort Worth, TX - DoYouBuzz

© 2010 • 23

Impact�of�operation�T°

on�thermal�management

Motor�drives�in�industry�environment

Configuration:

A�large�part�of�motor�drives�inverters�(especially�for�conveyors)�use�air�cooling:�under�55°C,�there�is�

almost�never�a�need�for�fans.

Depending�on�the�power�range,�a�fan�can�cost�from�2�to�50€,�it�roughly�represents�10%�of�the�inverter�

cost.

Therefore,�removing�fans�by�using�high�temperature�semiconductor

(SiC)�would�have�two�

positive�impacts:

Cost�Πreduction�of�10%�of�the�inverter�cost

Reliability�Πsuch�fans�have�to�be�replaced�every�50.000�hours,�which�implies frequent�stops�of�factories�

and�cost�of�maintenance

Aluminum�is�also�used�for�cold�plates�where�thermal�

management�solutions�are�implemented:

Liquid�cooling�system�based�on�pipes

IGBT�modules�are�fixed�on�those�systems

Page 24: Fort Worth, TX - DoYouBuzz

© 2010 • 24

SIC�FOR�HIGH�TEMPERATURE

Page 25: Fort Worth, TX - DoYouBuzz

© 2010 • 25

Comparison�Si,�SOI,�SiC�and�GaN� in�Power�Electronics

Silicon SOI SiCGaN

(on�silicon)

Max.�junction�T° 125�°C 225�°C 400°C 350°C

Power�rangeSeveral�100’s�

kW<�100W

Several�100’s�

kWFew�kW

Max.�Vb 6.5�kV 600�V 10�kV 1.2�kV

4”

price�range $20 $70 $1,000+ <�$250

6”

price�range $35 $170 N/A <�$400

#�of�companies�

developing�

devices

100+ ~40 ~25 ~15

Page 26: Fort Worth, TX - DoYouBuzz

© 2010 • 26

Main�added�values�of�SiC�electronics

Higher�switching�frequency–

20�kHz�power�converter–

Increase�motor�speed–

Reduce�the�need�for�electric�noise�filtering�•

Higher�voltage�operation–

15kV�is�envisioned�for�train�traction�or�energy�T&D–

Will�divide�by�a�factor�2�to�3�the�size�and�weight�of�the�overall�power�module•

Higher�Junction�T°–

200°C�is�envisioned–

Increase�reliability–

Allow�passive�cooling�(no�more�water�??)–

Allow�the�integration�of�the�inverter�within�the�motor�in�traction�applications•

Reduction�in�power�losses–

2%+�more�efficient

Page 27: Fort Worth, TX - DoYouBuzz

© 2010 • 27

Relative�interest�of�SiC�introduction

High temp. High freq. Smaller devices Low losses

Now2011

Future2015

Now2011

Future2015

Now2011

Future2015

Now2011

Future2015

Automotive

Rail

Motor�

drivers

T&D

PV

Wind�

turbines

Others Application�dependent

No�interest

Limited�interest

Strong�interest

Page 28: Fort Worth, TX - DoYouBuzz

© 2010 • 28

Relative�interest�of�SiC�introduction

High temp. High freq. Smaller devices Low losses

Now2011

Future2015

Now2011

Future2015

Now2011

Future2015

Now2011

Future2015

Automotive

Rail

Motor�

drivers

T&D

PV

Wind�

turbines

Others Application�dependent

No�interest

Limited�interest

Strong�interest

SiC’s�high�temperature�performances�

are�not�the�main�interest�in�power�

electronics.�The�increased�conversion�

efficiency

through�higher�frequency�and�

lower�losses�are�more�of�interest�for�

integrators.

Page 29: Fort Worth, TX - DoYouBuzz

© 2010 • 29

Your�contacts�at�YOLE

Your�contacts�at�YOLE�Développement:–

Brice�Le�Gouic,�Market�analyst�in�charge�of�

Power�Electronics�activities•

Email:�[email protected]

Tel:�+33�472�83�01�81

Alexandre�Avron,�Market�analyst�in�Power�

Electronics•

Email:�[email protected]

Tel:�+33�472�83�01�03

Jeffrey�Perkins,�General�Manager,�Yole�Inc.•

Email:�[email protected]

Tel:�+1�650�906�7877

Page 30: Fort Worth, TX - DoYouBuzz

© 2010 • 30

Questions�&�Answers

Thank�you�for�your� attention

Questions�are�welcome

Jeffrey�Perkins,�General�Manager,�Yole

Inc.

Email:�[email protected]

Tel:�+1�650�906�7877

Contact�details:

Come�and��visit�us�at�our�booth

Come�and��visit�Come�and��visit�us�at�our�boothus�at�our�booth