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IGBT reliability in converter design Zhou Yizheng.

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Presentation on theme: "IGBT reliability in converter design Zhou Yizheng."— Presentation transcript:

1 IGBT reliability in converter design Zhou Yizheng

2 Temperature T j >150°C T case < -40°C Current I C short circuit surge current RBSOA / SOA Mechanical stress shock & vibration forces on terminals heat sink bending Voltage V CE Over-voltage V GE Over-voltage Faulty control shoot through(dead time) short pulse Wrong handling ESD wrong mounting proc. Thermal stress thermal cycling power cycling by How to destroy an IGBT module ? Other components driver bus bar

3 Set datePage 3Copyright © Infineon Technologies All rights reserved. Converter reliability Component qualification Correct assembling Proper design  Hardware  control  Lifetime & reliability estimation Sufficient protection  Over voltage  Over current  Over temperature

4 Set datePage 4Copyright © Infineon Technologies All rights reserved. Assembling Mounting torque  DCB crack  terminal broken Mounting sequence  thermal grease distribution

5 Set datePage 5Copyright © Infineon Technologies All rights reserved. Assembling Applying thermal grease  thermal grease thickness  high Rthch  thermal grease distribution  DCB crack TIM(thermal interface material) Screen printer

6 Set datePage 6Copyright © Infineon Technologies All rights reserved. Assembling ESD  IGBT is ESD sensitive component

7 Set datePage 7Copyright © Infineon Technologies All rights reserved. Proper design(hardware) Vce overvoltage  must not exceed blocking voltage  Low commutation loop stray inductance  Proper Rgoff  Suitable protection in abnormal condition Vge overvoltage  can not exceed 20V  influence SC capability  Proper driving voltage level  Short gate cable length  Efficient clamping

8 Set datePage 8Copyright © Infineon Technologies All rights reserved. Proper design(hardware) RBSOA  Maximum turn off two times of nominal current  over current protection point SOA (Diode)  Peak power limitation ¬IGBT turn on speed ¬Stray inductance ! VR(t) [V] IR(t) [A] locus i R (t)*v R (t) ! 0

9 Set datePage 9Copyright © Infineon Technologies All rights reserved. Proper design(hardware) Maximum junction temperature  Maximum operation temperature within limitation (including overload condition and temperature ripple)  accurate losses calculation Switching losses  accurate thermal impedance value Rthch Rthha  certain design margin Considering aging issue Considering lifetime

10 Set datePage 10Copyright © Infineon Technologies All rights reserved. Proper design(hardware) Temperature sensing Detect junction temperature  almost impossible for real products, but in lab… 1.Gate Resistor of IGBT chip as a sensor (R GINT ) 2.Infrared Camera (IR-Camera) 3.Thermocouple 4.Infrared sensor

11 Protection(temperature) R GINT method ¬can detect chip junction temperature ripple ¬synchronization and sophisticated data acquisition are needed ¬measurements at high voltage are possible

12 Protection(temperature) IR- camera ¬Temperature ripple detection is possible ¬requires an open module ¬Limited by high voltage Set dateCopyright © Infineon Technologies All rights reserved.Page 12

13 Protection(temperature) Thermocoupler ¬Special module need to be prepared ¬Not suitable for junction temperature ripple Infrared sensor ¬Not suitable for junction temperature ripple ¬Limited by high voltage Set dateCopyright © Infineon Technologies All rights reserved.Page 13 IR-Sensor Assembly fixture Customer made sample

14 Set datePage 14Copyright © Infineon Technologies All rights reserved. Proper design(hardware) Mechanical stress (vibration) ¬Fixing block (force direction) ¬Soft copper bus bar ¬Fastness of capacitor

15 Set datePage 15Copyright © Infineon Technologies All rights reserved. Proper design(control) Dead time (avoid short through)  driver delay may shrink dead time  Worst case is at small current condition  Software dead time VS. hardware dead time Minimum pulse width  Short pulse will speed up switching ¬IGBT switching voltage spick ¬Didoe reverse recovery  Care about hardware dead time t DT =[((t doff (max)+t f (max))-t don (min))+(t PHLmax -t PLHmin ))]×1.5

16 Set datePage 16Copyright © Infineon Technologies All rights reserved. Proper design(Lifetime & reliability estimation) Power cycling  Bonding wire reliability ¬Junction temperature ripple ¬Junction temperature ¬Cycling time Thermal cycling  Soldering reliability ¬case temperature ripple ¬case temperature ¬Cycling time

17 Comparing to old generation chip, IGBT4 have around 4 times improvement with same max. junction temperature. By improvement of bonding technology and chip metallization Proper design(Lifetime & reliability estimation)

18 By improvement of material, soldering process, DCB shape… Proper design(Lifetime & reliability estimation)

19 How to estimate lifetime of IGBT module What’s needed: Basic system parameters ¬Output current ¬Output frequency ¬Power factor ¬Modulation index ¬Switching frequency

20 How to estimate lifetime of IGBT module Calculate the losses and further more get temperature ripple. losses Temperature ripple Thermal model of system

21 How to estimate lifetime of IGBT module Compare PC/TC curve with estimated number off temperature ripple

22 Set datePage 22Copyright © Infineon Technologies All rights reserved. Cosmic radiation  DC link voltage  Altitude  FIT Proper design(Lifetime & reliability estimation)

23 Set datePage 23Copyright © Infineon Technologies All rights reserved. High altitude effect  FIT rate(due to cosmic radiation)  Cooling  Clearance Proper design(Lifetime & reliability estimation)

24 Set datePage 24Copyright © Infineon Technologies All rights reserved. Protection (voltage) DC link voltage overvoltage  IGBT blocking voltage(active clamping voltage) limitation  IGBT turn off snappy Vce overvoltage  more severer at overload and short circuit condition  soft turn off, two level turn off  active clamping Vge overvoltage  zener diode, TVS  clamp to 15V

25 Set datePage 25Copyright © Infineon Technologies All rights reserved. Protection (current) Over current ¬Two times of nominal current ¬Transient junction temperature within limitation Short circuit ¬Short circuit time within 10us ¬Short circuit gate voltage limitation (SC energy, current) ¬Short circuit turn off after IGBT goes into desaturation

26 Set datePage 26Copyright © Infineon Technologies All rights reserved. Protection(temperature) Over temperature Hundreds of ms Several s Tens of s

27 Set datePage 27Copyright © Infineon Technologies All rights reserved. Protection(temperature)  Sensing case temperature  time delay is around several seconds  Require prior estimation delt Tjc max.  Sensing heatsink temperature  time delay is around tens of seconds  Require prior estimation delt Tjh max.  suffer from Rthch changing due to thermal grease aging

28 Set datePage 28Copyright © Infineon Technologies All rights reserved. Protection(temperature) Over temperature  How to realize fast and accurate temperature protection ¬Real time transient losses calculation, and ¬Temperature detection point(as close as to chip), and ¬Thermal impedance model  Real time calculation of the junction temperature

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