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High Power Density IGBT Module High Power Density IGBT Module for High Reliability Applications for High Reliability Applications 

D.J. Chamund, L. Coulbeck, D.R. Newcombe, P.R. Waind 

Presented by: Peter Waind Peter Waind 

High Power Density IGBT Module High Power Density IGBT Module for High Reliability Applications for High Reliability Applications 

D.J. Chamund, L. Coulbeck, D.R. Newcombe, P.R. Waind

Outline

Ø Ø Introduction Introduction

Ø Ø Basic IGBT Module Structure Basic IGBT Module Structure

Ø Ø Module Reliability Module Reliability

Ø Ø Technologies for increased power density

Ø Ø Conclusion 

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Basic IGBT Module Structure Basic IGBT Module Structure

Technologies for increased power density

Objective

Ø Ø Quantify Quantify a a range range of of technology technology

Increase Increase power power density density without without 

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technology technology solutions solutions to to: :

without without adversely adversely effecting effecting reliability reliability

IGBT Module 4 

G 

E 

C

Schematic of Construction 

Epoxy 

Heat Sink 

Heat Sink Compound 

Base plate 

Solder Copper 

Ceramic Copper Track 

Silicon 

Silicone Gel Temp gradient 

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Schematic of Construction 

Epoxy 

Heat Sink 

Heat Sink Compound 

Base plate 

Solder 

Copper 

Ceramic 

Silicone Gel

Reliability Constraints

Failure Failure Mechanisms Mechanisms Ø Ø Random Random Failures Failures 

• • Latent Latent defects defects 

• • Cosmic Cosmic Rays Rays 

Ø Ø  Wear Wear Out Out failures failures 

• • Wire Wire bond bond lifting lifting 

• • solder solder cracking cracking 

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− = 

stress use 

a 

T T k E AF  1 1 exp 

B 

j T A N

∆ =

Arrhenius equation

Internally derived model

Coffin‐Manson equation

Examples of wear out failures

Wire Bond failure 

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Examples of wear out failures

Solder joint failure

5 µm 

Failure Produced in RAPSDRA programme 

Example of Random Failure Example of Random Failure

Cosmic ray failure site Cosmic ray failure site 

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Failure Produced in RAPSDRA programme 

Example of Random Failure Example of Random Failure

Summary for maintenance of reliability

Ø Ø  For random failures For random failures – – maintain or reduce the maximum junction temperature maintain or reduce the maximum junction temperature 

Ø Ø  For wear out For wear out – – maintain or reduce the delta T maintain or reduce the delta T 

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Summary for maintenance of reliability

maintain or reduce the maximum junction temperature maintain or reduce the maximum junction temperature 

maintain or reduce the delta T maintain or reduce the delta T

Increase Power Density Increase Power Density

Ø Ø Application specific device characteristics Application specific device characteristics

Ø Ø Increased current rating per silicon chip Increased current rating per silicon chip

Ø Ø Increased Increased junction junction temperature temperature

Ø Ø Advanced Advanced cooling cooling

Ø Ø Increased Increased active active silicon silicon area area 

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Increase Power Density Increase Power Density

Application specific device characteristics Application specific device characteristics

Increased current rating per silicon chip Increased current rating per silicon chip

temperature temperature

area area

Application specific device characteristics 11 

Application specific device characteristics

Increase current rating per chip Increase current rating per chip 

NPT 

Vertical structures 

p Electric field 

n­ 

Doping Profile 

Soft Punch Through enables reduction in silicon thickness 

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Increase current rating per chip Increase current rating per chip 

SPT 

Vertical structures 

p 

Electric field 

n 

Buffer 

n­ p 

Soft Punch Through enables reduction in silicon thickness

Increased current rating per chip Increased current rating per chip 

0 

20 

40 

60 

80 

100 

120 

0 

Collector current, Ic 

Optimised emitter design, such as trench gate, can also reduce on‐state losses allowing for increased current rating 

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Increased current rating per chip Increased current rating per chip 

3.3kV IGBT Forward Characteristics, 125°C, single chip 

1  2  3  4  5  6 

Collector­emitter voltage Vce 

Trench SPT DMOS SPT 

Optimised emitter design, such as trench gate, can also state losses allowing for increased current rating

Increased current rating per chip Increased current rating per chip • •  Effect of Switching Frequency Effect of Switching Frequency 

– –  Headline current rating is a DC rating Headline current rating is a DC rating 

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3.3kV Modules

Increased current rating per chip Increased current rating per chip Effect of Switching Frequency Effect of Switching Frequency 

Headline current rating is a DC rating Headline current rating is a DC rating

Increased Tj

Although increase in Tj will increase power density

This is against criteria to maintain reliability 

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Although increase in Tj will increase power density

This is against criteria to maintain reliability

Advanced cooling

Ø Ø Eliminate layers to reduce overall thermal resistance Eliminate layers to reduce overall thermal resistance

Ceramic substrates mounted directly onto heat 

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Eliminate layers to reduce overall thermal resistance Eliminate layers to reduce overall thermal resistance

Ceramic substrates mounted directly onto heat‐sink

Advanced cooling

Construction  Thermal Resistance 

(junction –heat sink) Standard  21°C/kW 

Integrated heat sink 

7°C/kW 

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Thermal Resistance 

(junction –heat sink) 

DC Current (∆Tj = 45°C) 

C/kW  657 A 

C/kW  1302 A

Increase active silicon area

EPD 500A 3.3kV chopper module 

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Increase active silicon area

EPD 500A 3.3kV chopper module

Std. subst

EPD subst

EPD 2 subst

Increase active silicon area: R 

Module Construct 

IGBT Rth jn. to case (°C/kW) 

Rth case to heatsink (°C/kW) 

Standard  12  8 

EPD  9.6  8 

EPD 2  8  8 

Rth of a 140mm x 130mm 3.3kV single IGBT Rth of a 140mm x 130mm 3.3kV single IGBT module module 

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Increase active silicon area: R th benefit 

Rth case to heatsink C/kW) 

Rth jn. to heatsink (°C/kW) 20

17.6 

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Rth of a 140mm x 130mm 3.3kV single IGBT Rth of a 140mm x 130mm 3.3kV single IGBT module module

Increased active silicon area Increased active silicon area

Frequency rating 

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Increased active silicon area Increased active silicon area

Wear out life of EPD

Increased active silicon area Increased active silicon area

Inductive switching

• •  Typical EPD switching waveforms for a 500A Typical EPD switching waveforms for a 500A 3.3kV chopper module @125 3.3kV chopper module @125 

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Increased active silicon area Increased active silicon area

Short circuit test

Typical EPD switching waveforms for a 500A Typical EPD switching waveforms for a 500A 3.3kV chopper module @125 3.3kV chopper module @125° °C. C.

Conclusion

• •  Techniques for increasing current density have been discussed Techniques for increasing current density have been discussed 

• •  Data Data­ ­sheet continuous current rating does not include switching sheet continuous current rating does not include switching losses and hence current de losses and hence current de­ ­rating should be considered when rating should be considered when operating in switch mode operating in switch mode 

• •  We have demonstrated that better utilisation of module area is We have demonstrated that better utilisation of module area is an effective way of increasing power density an effective way of increasing power density 

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Techniques for increasing current density have been discussed Techniques for increasing current density have been discussed 

sheet continuous current rating does not include switching sheet continuous current rating does not include switching rating should be considered when rating should be considered when 

We have demonstrated that better utilisation of module area is We have demonstrated that better utilisation of module area is an effective way of increasing power density an effective way of increasing power density