If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
I'm not too sure, that's why I stick near to the 1x Icm end of the spectrum where the manufacturer already worried about it for me.
But given the device has a MTBF of 100us at 6x Icm, and 10 years at 1x Icm, some sort of power law would seem like a good bet. "The MTBF halves for every N percent increase in current above Icm": find N.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
In the datasheet they usually state, that the pulse width of the maximum peak current is "limited by maximum junction temperature". The peak current rating is repetitive. Doesn't this imply, that the junction temperature rise during the pulse can be as high as 125 °C (25 to 150 °C) without a limit on the number of pulses?
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
Doesn't this imply, that the junction temperature rise during the pulse can be as high as 125 °C (25 to 150 °C) without a limit on the number of pulses?
Hah! *I* dont think so! Thats where engineering experience comes into play: interpreting the data sheets. Sure you can probably pulse it to 150C die temp for awhile, but who really knows when its gonna pop. All that statement means to me is that crossing 150C means it could go pop *immediately* instead of just wearing out due to fatigue. I think that statement is also a reminder to the designer to check your peak die temp calculations.
Powerex has application notes on using IGBT modules that talk a little bit about thermal fatigue with respect to the die solder connection to the base plate. "All available information has indicated that thermal fatigue is not an issue when [delta] Tj is kept below 30°C."
see also
I havent found anyone really referencing thermal fatigue on small IGBTs that lack the aluminum nitride insulator (maybe thermal fatigue is less of a problem?). Their application is for traction drives, where the temp goes up and down over seconds/minutes, and they still have a rather finite cycle life. Spiking the temp at 100s of hz seems like it would wear them out real fast... It would be an interesting test to see how many shots you could get with fast temp spikes.
If you are blowing up IGBTs and want to figure out why, do all the thermal calculations outlined in those ap notes, if you exceed delta Tj of 30C, or Tj max of say 120C, then it probably means your IGBTs are failing *by design* and that you need to increase your safety margins. I can say for a fact that lots of my old semiconductor failures were simply due to thermal stress, mainly because i had no real design method and just threw stuff together with the TLAR method (Coined by Finn Hammer, "That Looks About Right"). Now every power device i build (hobby or professionally) gets a rather thorough thermal analysis considering worst case operation.
But given the device has a MTBF of 100us at 6x Icm, and 10 years at 1x Icm, some sort of power law would seem like a good bet. "The MTBF halves for every N percent increase in current above Icm": find N.
Figure 3.16 in seems to imply just such a power law. Your bet looks good, if you replace pulsed I by deltaT.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.