Power module technology with extended reliability

for hybrid electric vehicle applications

Josef Lutz, Alexander Hensler, Markus Thoben, Thomas Gutt

Josef Lutz. Chemnitz University of Technology

Alexander Hensler, former Chemnitz University, meanwhile Siemens AG, Erlangen

Markus Thoben and Thomas Gutt, Infineon Technologies Warstein

1

Some results of the joint project „Electric Components

for Active Gears“ (EfA), with financial support by German

government (BMWi)

FKZ 19U6006A-F, 19U8006G

Power module technology with extended reliability

for hybrid electric vehicle applications

2 [Her12]

Aim:

Use combustion engine coolant

(105°C, worst case 125°C)

Tjmax 200°C, sufficient power

cycling capability

EfA: Power electronics cooled by cooling circuit of the combustion engine

3

heatsink

die

solder Cu

ceramics

solder Cu

base plate

thermal grease

bond wire

die

solder

ceramics

Cu

bond wire

Cu

heatsink

thermal grease

a

b

weak point 1:

bond connection weak point 2:

chip solder

weak point 3:

large area solder connection

Weak points in packaging technologies to be adressed

weak point 4:

thermal grease

4

EfA:

- reference standard modules

- improved bond interconnections (doped bond wires)

- different chip thickness

V = 600V (chip thickness 70µm)

1200V (chip thickness 120µm)

1700V (chip thickness 180µm)

6543

2

1 273

DVIteTKN on

T

JfJ

(TJ = Tlow in °C)

Comparison with former work (CIPS 2008)

[Bay08] [Hen11]

EfA results #1

5

Electric Components for Active Gears

1,0E+04

1,0E+05

1,0E+06

1,0E+07

40,00 50,00 60,00 70,00 80,00 90,00 100,00 110,00 120,00

An

zah

l d

er Z

yk

len

ΔTj [K]

Lebensdauerauswertung

Test 600V IGBT Test 1200V IGBTTest 1700V IGBT CIPS2008 600VCIPS2008 1200V CIPS2008 1700VStandard BSM100GS120DLC

Improved bond wires alone: no increase of

reliability at these conditions.

End-of-Life: Rth-increase.

Root cause: fatigue of chip solder

EfA results #1

6

N

um

be

r o

f c

yc

les

10 7

10 6

10 5

10 4

Test conditions:

Tjmin = 75°C; Tjmax = 175..187°C;

ton = 1..4sec; toff = 3..6sec;

ILoad per bond foot = 9.4..12.5A

EfA results #2

- Diffusion soldering

- all other production steps like

standard modules

[Gut10], [Gut12]

EfA results #2

7

80

90

100

110

120

90

95

100

105

110

0 10 20 30 40 50 60 70 80 90

Rth

%

VC

E%

*10³ Zyklen

Verlauf von VCE und Rth

VCE

Rth

5% Anstieg (VCE)

VCEVCE

Rth

1,0E+04

1,0E+05

1,0E+06

1,0E+07

80 90 100 110 120

An

za

hl

Zyk

len

ΔTj in K

Lebensdauerauswertung

verbesserte Lötung zwischen Chip und DCB-Stubstrat

standard 600V IGBT-Leistungsmodule

All failures: Bond-Wire Lift-off

Diffusion soldering leads to a

significant improvement (factor 3)

all tests with

Tjmin 75°C

EfA results #2

VCE

Rth

improved solder layer chip to substrate

standard 600V power modules

cyc

les

8

* 10 3 cycles

EfA results #3

- diffusion soldering

- improved bond wires

- improved chip metallization

Tjmax 175°C

(exception ΔT > 130K)

EfA results #3

9

90

95

100

105

110

0 1.000.000 2.000.000 3.000.000 4.000.000

VC

E, R

thin

%

Zyklen

VCE

Rth

Metallization variant 3, ΔT =

94K,

Tjmin = 83°C, ton = 0.7s

(only sample with End-of-

Life)

EfA results #3

cycles

10

Standard: Al

Improved wire material, modified

die metallization

Si

Cu, Al2O3, Cu (DCB)

Standard: Sn-Ag solder

improved: diffusion solder

Standard: 3mm Cu without PinFin

improved: 5mm Cu with PinFin

Standard: Sn-Ag solder

improved: silver sinter technology

EfA-results #4

EfA results #4

11

Twater_min

22°C

Twater_max

122°C

theating (passive) 10min

tcooling (passive) 5min

ILoad

220A

ton (active)

2s

toff (active)

4s

No of active cycles

per passive cycle

100

Tjmax (standard-

module)

175°C

Tjmax (improved

module)

173°C

Aim: stress to the interconnection Chip - DCB

as well as to DCB - base plate

EfA results #4

12

Standard technology: failure after 2 400 long cycles, caused by base

plate solder layer

New technology: no failure after 6 500 long and 650 000 short cycles

EfA results #4

standard IGBT

modules

modules with

silver sintering

Long cycles

EOLEOL

not reached

13

EfA results #5

New solder process

substrate to base plate.

The new solder layer

contains vertical

intermetallic phases

Further: improved bond wires, diffusion soldering identical EfA results #4

Test conditions: identical EfA results #4

Test after 2100 long cycles aborted for ultrasonic analysis

[Gut10]

EfA results #5

14

Expected lifetime of this solder layer:

> 6500 long cycles

System solder

layer

Chip solder layer

EfA results #5

15

Summary

Improved bond wires alone give no longer lifetime,

considering the used conditions.

Improved chip solder layer (diffusion soldering), improved

bond wires and improved metallization leads to a significant

longer power cycling lifetime (factor 100 possible)

Additional improved substrate solder layer leads to a very

high power cycling capability

The reached power cycling capability shows potential for use

of power modules in the cooling circuit of the combustion

engine, with Tjmax = 200°C.

Packages with SiC devices require improved packaging

technology

16

[Bay08] R. Bayerer, T. Licht, T. Herrmann, J. Lutz, M. Feller: “Model for Power Cycling lifetime of

IGBT Modules – various factors influencing lifetime”, Proceedings of the 5th International

Conference on Integrated Power Electronic Systems, p 37-42 (2008)

[Gut10] K. Guth, F. Hille, F. Umbach, D. Siepe, and J. Görlich, "New assembly and interconnects

beyond sintering methods," Proceedings of the PCIM, Nuremberg, 2010, pp. 232-237

[Gut12] K. Guth, N. Oeschler, L. Boewer, R. Speckels, G. Strotmann, N. Heuck, S. Krasel, A.

Ciliox, „New interconnect technologies for power modules”, Proceedings CIPS 2012, paper 10.1

[Hen11] A. Hensler, J. Lutz, M. Thoben, A. Munding, D. Zeidler, S. Lutz, W. Schön: “Reliability

Investigations of Improved Power Modules - Results from EfA-Project”, Proc. Braunschweiger

Symposium Hybrid- und Elektrofahrzeuge (2011)

[Her12] C. Herold, A. Hensler,J. Lutz, M. Thoben ,T. Gutt: “Power Cycling Capability of New

Technologies in Power Modules for Hybrid Electric Vehicles” Proceedings of the PCIM,

Nuremberg, 2012, pp. 486-493

References