EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: wlamb02 on June 24, 2017, 07:32:27 am
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I recently ordered some mosfets for my power supply project about 2 weeks ago. I ordered some from ebay and others from aliexpress. The fake mosfets I got from aliexpress, the price didnt seem too outrageously cheap (20pcs for 12$). The mosfets I got from ebay are real, i have bought them from the same seller and they work great. Before I used the fake mosfets I tested them, they seemed fine, but they had a slightly higher on resistance then the datasheet says, but i didnt think much of it. Then, they kept blowing on me. I suspected them to be fake so I opened a fake one and a real one and compared them.
The tube the fakes came in
(http://i.imgur.com/biPNHl9.jpg)
Real IRFP460
(http://i.imgur.com/kDtdPb2.jpg)
Fake (but looks pretty convincing)
(http://i.imgur.com/xIOJn8lg.jpg)
Fake opened
(http://i.imgur.com/LpYruHz.jpg)
Real opened
(http://i.imgur.com/98LHRZz.jpg)
Real (left) vs Fake (right)
(http://i.imgur.com/3NW8UHZ.jpg)
large heat spreader, real (top) vs thin heat spreader, fake (bottom)
(http://i.imgur.com/MeAxIAZ.jpg)
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Does the RDS(on) value of the real MOSFET close to the one specified in the data sheet?
I agree the best method to tell the fake apart is to measure the RDS(on) value at the specified current. Fake one usually measured many times higher than the real one.
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I did more tests and measurements and I tested the Rdson for the real mosfet and it was 0.3 \$\Omega\$ I tested the fake transistor and it was 0.45 \$\Omega\$ I also tested the breakdown voltage of the fake and it was only around 200V. This leads me to believe that these were re-labeled and sold as IRFP460 when they actually weren't.
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Recycled transistors usually have new leads welded on to the old stumps then heavily tinned to obscure the joint. So far they have worked out well for me.
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the price didnt seem too outrageously cheap (20pcs for 12$).
it is outrageously cheap.... when its far off the digikey price, you can bet its counterfeit...
https://www.digikey.com/products/en?keywords=IRFP460 (https://www.digikey.com/products/en?keywords=IRFP460)
$0.60 vs $3.66 is far off...
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I have been using what I think are fake Infineon SPW47N60C3 mosfets for about 10 years from the one supplier in China. The reason I think they are fake is because the back metal surface is all scratched and dull looking, and when I bend the leads at a right angle some of them used to crack and break. Also the trademark is not quite perfect. Known real ones are not like this in all three areas. Nevertheless the die size is the same, the RDSon seems the same and the voltage rating is at least as good. Probably about 1 in 100 is faulty. Reliability is good. But I have also bought from China IGBTs and EPROMs that are totally useless. :--
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Those who you denoted as the real ones certainly are not. I have somewhere original IRFP460s from a local reputable distributor I have payed good money for, and they definitely look different - more like those with the polished window.
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I have been using what I think are fake Infineon SPW47N60C3 mosfets for about 10 years from the one supplier in China. The reason I think they are fake is because the back metal surface is all scratched and dull looking, and when I bend the leads at a right angle some of them used to crack and break. Also the trademark is not quite perfect. Known real ones are not like this in all three areas. Nevertheless the die size is the same, the RDSon seems the same and the voltage rating is at least as good. Probably about 1 in 100 is faulty. Reliability is good. But I have also bought from China IGBTs and EPROMs that are totally useless. :--
They sound like recycled MOSFETs which have had new leads welded on. They break easily when bent.
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Those who you denoted as the real ones certainly are not.
Yes, they certainly look like fake ones. But the one marked as fake looks very similar to genuine parts from the outside.
This is how genuine IR mofets look like:
(https://www.eevblog.com/forum/beginners/fake-irfp460-mosfets-from-aliexpress/?action=dlattach;attach=326857;image)
One is actually an IGBT and the other one a IRFP460LC made by Vishay/Siliconix, but both look identical except for the manufacturer logo.
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Hi,
Are some of those pictures to scale?
I ask because in at least one pic i see a die size that is much smaller than the supposed real one.
Die size has a lot to do with the current capability of diodes and that would mean Rds(on) too.
See if you can find a correlation with the total die area for the fake vs the real for the Rds(on) spec.
If the area of the real was 2 times the area of the fake (for example only) then the Rds(on) should be roughly 1/2 of the fake. If the die size is smaller and it really is a true part number it could be that they have different grades for the same part, like A,B,C, so you could check that too although i doubt that.
A Rds(on) of 0.45 and 0.3 would indicate 1.5 times more die area for the 'real' one. Measure them carefully and see what you get.
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I have got thousands of mosfets (IRLR8113 92A 30V ) in "original" packaging from Aliexpress. They work fine. But when washed in water the "laser" markings wash away. Atmel processors, ATmega64A-AU the same but also work fine.
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I tried isopropyl alcohol and rubbed it on the markings and they didn't wash away. These counterfeits are exceptionally good.
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Why would someone sell a $3 part that no volume, even 100ku, will bring down below $2.25 - for $.75? It's going to be fake or recycled; there's just no way to source those at such a low price, and if YOU found say 10000 at some liquidation event, would YOU sell them for $.75? No, of course not. The old adage goes - if it's too good to be true...
And, of course, they could be selling them at $2.50. They'd still likely be fake or recycled. This is why it's highly advisable not to buy parts on ebay or aliexpress, unless someone else does the due diligence and will vouch for their authenticity. (Sometimes deals CAN be had, but unless you know what you're buying you're just going to lose money since you'll have to go buy the part from a proper channel eventually, anyway.) The exception is some jellybean parts, like 1N4148 diodes and resistors - parts that are so cheap to begin with there is no cheaper substitute and releading them costs more than they're worth.