# Cheap diode 403CNQ400



## Cor (Sep 17, 2013)

Datasheet: http://pdf.datasheetcatalog.com/datasheet/irf/403cnq.pdf
Cor.
(I am using this diode in my EV controller)


----------



## PStechPaul (May 1, 2012)

The actual IRF datasheet shows only 80, 90, and 100V versions:
http://www.irf.com/product-info/datasheets/data/403cnq.pdf

Forward voltage is 0.83V at 200A and 0.97V at 400A at 25C. 0.69V and 0.82V at 125C.

Here is what is offered on eBay:
http://www.ebay.com.au/itm/403CNQ40...ttky-Bridge-Rectifier-400A-400V-/190769441060

This unit is from Hong Kong and the company seems to specialize in consumer products, fashions, games, etc. I suspect it may be counterfeit. If you have one you may want to see if it is really a Schottky type, easily determined with a multimeter diode check. You can check reverse breakdown with a 400V supply and a 100k to 1 megohm power resistor to limit reverse current.

Here is the Vishay version from Mouser, also 100V, and $77 each:
http://www.mouser.com/ProductDetail/Vishay/VS-403CNQ100PBF/?qs=%2fha2pyFaduh8rzF7%2fQdx6g18sR8lcq8an6m2jfYHapU%3d
http://www.mouser.com/ds/2/427/94206-95656.pdf


----------



## Cor (Sep 17, 2013)

As I said before, I am running this diode in my EV controller.
Due to the fact that the controller has serious issues (I am still not sure
if it is that it has such a bad layout that spikes are killing components or
that the connectors might lose contact during bumps in the road or that
the driver stage of the controller is unable to always drive the IGBT with
enough current to switch it fast - anyway, once every 1000+ miles the
IGBT and diode blow and the controller detects the short circuit, so it
drops the contactors and I need to wrench 2 or 3 hours to replace them.
I have almost half dozen of these diodes with one half blown (shorted) and
the other half still working fine. I am tempted to cut them in half and
use two good halves as replacement, but these diodes sell for $16 on
the UXCELL website - which is also the entity behind all the Ebay stores
that sell this diode for around $20.
Nice thing of UXCELL is that they like return visits, so they ship a $5 
coupon with every shipment, so the next diode you can order for $11
(which is what I just did today, before the coupon end date)
And yes, it has 0.4V diode drop according to my multimeter in diode test setting, so it should be the Schottky that it claims to be.
Cor.


----------



## DJBecker (Nov 3, 2010)

We've had problems with both 'snappy' diodes that shorted and killed the active devices and counterfeit FETs bought from a Chinese supplier.

I was even foolish enough to buy a second batch from the same supplier. It was only because my co-designer suggested that we test the incoming parts that we figured out they were at least 10x worse than the genuine.

The FETs were easy to check: we used a 12V battery and a battery tester, turned the gate on with a bench supply, and cranked the current. By the time we reached 20 amps the FETs were dropping over 2V instead of the expected 160mV.

Ordering the same part number from Digikey fixed the overheating problems we were having. With a side by side comparison we could see a texture difference in the case surface and markings, but you definitely wouldn't pick out the fake parts if they were presented alone.

I don't know how you would test diodes for recovery speed with hobby-level equipment.


----------



## Cor (Sep 17, 2013)

DJBecker said:


> We've had problems with both 'snappy' diodes that shorted and killed the active devices and counterfeit FETs bought from a Chinese supplier.


Hm, that is good to know. I now grabbed two of the diodes that I have here,
one a 203CNQ100 and the other the Hong Kong supplied 403CNQ400 and at
a current of 12A (Max that my lab supply can deliver) both are showing
just over 0.7V drop. That is too high according to the datasheet, it
should be no more than 0.5V at room temp (and yes, I measured with a
DVM at the diode itself, not at the other end of the 12A carrying wires,
so used the proper 4-wire setup).
Anyway, it seems that the Chinese did a nummer on IR after IR discontinued the 403CNQ series, so you can buy clone/fake diodes that
do not really have the IR specs, but are branded with the IR logo,
the part numbers but not the same performance. Hm...



DJBecker said:


> I don't know how you would test diodes for recovery speed with hobby-level equipment.


You could try to things like measure current and diode voltage in time with
a scope (at lower current levels). For now, I just measured forward drop
as a first indicator of quality. It does not look good and could explain
why my controller fails every few months. I am going to look for a different
diode that does at least 200A and 150V...


----------



## Siwastaja (Aug 1, 2012)

Counterfeit discrete semiconductors indeed are typical. I have got some too. Don't buy those from Ebay at all unless you are sure what you are doing. They are often almost as expensive as the genuine ones from Digikey or other reputable suppliers.

Otherwise, some of the stuff from Chinese Ebay suppliers is just fine. Just forget FETs, BJTs or diodes.


----------



## Cor (Sep 17, 2013)

Siwastaja said:


> Counterfeit discrete semiconductors indeed are typical. I have got some too. Don't buy those from Ebay at all unless you are sure what you are doing.


I bought a *real* IR diode from a USA source, it is a 409CNQ150
(so, still 400A but 150V which is enough for my purpose and also this
part actually is mentioned on an IR datasheet)
This one measured out with a forward drop of 0.48V at 12A, which is more
like I would expect from a Schottky diode and it conforms to the datasheet.
So, I should stop buying junk from China, I guess...


----------



## evric (Oct 26, 2008)

Which US supplier did you finally use? 
DIGIKEY don't have any in stock and MOUSER has them for over $80.00 each


----------



## Cor (Sep 17, 2013)

evric said:


> Which US supplier did you finally use?
> DIGIKEY don't have any in stock and MOUSER has them for over $80.00 each


Ebay is usually my reference and in a lot of cases also the final supplier ;-)


----------

