Lifetime of a seminconductor is doubled for every 10 degC below Tj(max) - Page 1
Forum section: electronics / beginners

author: ocset
author_rank: Super Contributor
timestamp: November 01, 2018, 06:17:24 am
content: Hi,Ive heard the above rule, but can't find any official data on it, do you know of any?Eg for example , in the case of a Power FET and diode in a 60W offline flyback SMPS.

author: sibeen
author_rank: Frequent Contributor
timestamp: November 01, 2018, 06:56:21 am
content: I suspect it comes from, or is closely related to, the Arrhenius equation.

author: BravoV
author_rank: Super Contributor
timestamp: November 01, 2018, 07:06:35 am
content: What is the baseline ? Say you can maintain it stable at 25 C, what will be the lifetime ?

author: not1xor1
author_rank: Frequent Contributor
timestamp: November 01, 2018, 07:18:43 am
content: Quote from: treez on November 01, 2018, 06:17:24 amit is worthwhile a copy & pasteQuotemore details and links here:https://en.wikipedia.org/wiki/Arrhenius_equation

author: AndyC_772
author_rank: Super Contributor
timestamp: November 01, 2018, 07:22:44 am
content: https://www.microsemi.com/document-portal/doc_view/124041-calculating-reliability-using-fit-mttf-arrhenius-htol-model

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: November 01, 2018, 10:09:25 am
content: What is not often understood is that although a heatsink or device case changes temperature relatively slowly, the junction of a semiconductor can change temperature on the scale of milliseconds under large changes in loading. (Ever tested a power amp on a dummy load and wondered where the music was coming from? Thermal vibration of the output transistor chips.)It follows that if you rate such a device to its absolute limit it will suffer a lot of ongoing thermal stress, and is likely to eventually fail even though strictly speaking it is not being overloaded.Also explains why ordinary fuses do not protect transistors from s/c damage. By the time the fuse wire melts, the transistor has long since moved on to a higher plane of existence.

author: rawrs
author_rank: Contributor
timestamp: November 02, 2018, 08:06:17 am
content: Sounds like insulation categories, as well. Insulation for motors, anyway. I probably should have googled before I replied, but it goes along the lines of;Whatever category of insulation you have, lets say 125C, which will be represented by a letter, approximately category E or F, or something along those lines here. It will quite happily do 125C all day long, for a quantifiable amount of time. But for every 10c above this rating, it will roughly halve its expected lifetime. So, lets say our 125C insulation is rated to last for 10,000 hours, as a pure pulled-from-the-arse number. If we run it at 135C, we can roughly halve its lifespan to 5,000 hours. 145C, you can kiss it goodbye after 2,500 hours. And I'm pretty sure that there will eventually be a point where someveryinteresting properties of that insulation come to light in a rather... lets say, luminous way.It sounds much like what the above members have said. Again, I am still a major in electronics noobery, so take what I say with a grain of salt, and please do feel free to learn me something if I get something wrong - I am here to learn, after all. But as far as motors go, the wiring is essentially a consumable part in decently industrial cases. For example when a train goes in for an overhaul roughly every 10 years, they'll basically strip the train down to its shell, remove all of the traction package components, and part of this overhaul will be ripping the motors apart, discarding all of the wiring that makes up that motor, renewing the wiring looms, re-assembling the traction package back on to the train, and hey presto, your six car train has 16 nicely refurbished motors ready for another 10 years of service and roughly 10 million kilometres, until the next overhaul.TL;DR, if the motor becomes large and expensive enough, it's my understanding that the wiring becomes consumable service items that have to be replaced every so often. But these are motors that will see daily service for many decades, so it makes economic sense to do this.Hope this rambling diatribe is remotely entertaining to anyone to read!Cheers,Rory

author: Chalcogenide
author_rank: Regular Contributor
timestamp: November 02, 2018, 08:43:37 am
content: A good part of failures of semiconductor devices are due to electromigration affecting metal interconnections (both on-chip and the bond wires). Electromigration is a thermally activated process that follows the Black's equation (https://en.wikipedia.org/wiki/Black%27s_equation). For the typical metals used for interconnects, the temperature dependence of the likelihood of failure turns out to double roughly every 10° C. It also depends on the current density, so for example a power FET operating close to the maximum current limit will fail sooner than the same device at the same (die) temperature that happens to operate at a lower current.