More Related Content Similar to Igbt reliability Similar to Igbt reliability (20) Igbt reliability2. Temperature
• Tj >150°C
• Tcase< -40°C
How to destroy an IGBT module ?
Current
•IC short circuit
• surge current
•RBSOA / SOA
Mechanical stress
• shock & vibration
• forces on terminals
• heat sink bending
Voltage
• VCE Over-voltage
• VGE Over-voltage
Faulty control
• shoot through(dead time)
• short pulse
Wrong handling
• ESD
• wrong mounting proc.
Thermal stress
• thermal cycling
• power cycling
by
Other components
• driver
• bus bar
3. Converter reliability
Component qualification
Correct assembling
Proper design
Hardware
control
Lifetime & reliability estimation
Sufficient protection
Over voltage
Over current
Over temperature
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4. Assembling
Mounting torque
DCB crack
terminal broken
Mounting sequence
thermal grease distribution
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5. Assembling
Applying thermal grease
thermal grease thickness high Rthch
thermal grease distribution DCB crack
TIM(thermal interface material)
Screen printer
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6. Assembling
ESD
IGBT is ESD sensitive component
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7. 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
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8. 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
3000
2000
1000
0
1000
2000
2
2000
1000
1
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time [400ns/div]
VR [500V/div] IR [500A/div]
1
3
!
0
0 1000 2000 3000
0
VR(t) [V]
IR(t) [A]
locus iR(t)*vR(t)
2
3
!
0
9. 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
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10. 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 (RGINT)
2.Infrared Camera (IR-Camera)
3.Thermocouple
4.Infrared sensor
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11. Protection(temperature)
C
E
F1 S1 S2 F2
G
RGINT RG = f(T)
IGBT-VRG
VGINT Chip
I0
Gate bond ±V0
Ri
RGINT 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
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13. Protection(temperature)
Thermocoupler
¬ Special module need to be prepared
¬ Not suitable for junction temperature ripple
Customer made sample
Infrared sensor
Assembly IR-Sensor
fixture
¬ Not suitable for junction temperature ripple
¬ Limited by high voltage
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14. Proper design(hardware)
Mechanical stress (vibration)
¬ Fixing block (force direction)
¬ Soft copper bus bar
¬ Fastness of capacitor
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15. 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
tDT=[((tdoff(max)+tf(max))-tdon(min))+(tPHLmax-tPLHmin))]×1.5
Minimum pulse width
Short pulse will speed up switching
¬ IGBT switching voltage spick
¬ Didoe reverse recovery
Care about hardware dead time
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16. 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
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17. Proper design(Lifetime & reliability estimation)
Comparing to old generation chip, IGBT4 have around 4 times
improvement with same max. junction temperature.
By improvement of bonding technology and chip metallization
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. Proper design(Lifetime & reliability estimation)
Cosmic radiation
DC link voltage
Altitude
FIT
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23. Proper design(Lifetime & reliability estimation)
High altitude effect
FIT rate(due to cosmic radiation)
Cooling
Clearance
1,E+07
1,E+06
1,E+05
1,E+04
FF450R17ME4
Cosmic Radiation Induced Failure Rate
per Device
RT, 4000m
FIT
1,E+03
1,E+02
1,E+01
1,E+00
Voltage [V] RT, sea level
125°C, 4000m
1000 1050 1100 1150 1200 1250 1300 1350 1400 1450 1500
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24. 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
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25. 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
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26. Protection(temperature)
Over temperature
Hundreds of ms
Several s
Tens of s
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27. 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
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28. 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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