Counterfeit high voltage transistors

[[email protected]]

It is likely this won't affect many, but we have good evidence of
counterfeit high voltage transistors from some suppliers. The types so
far affected are BU505 and MJE8502, these are 1500V VCES and 700V
VCEO. We noted failures in our products and traced to a very low VCEO
which I checked with a current limited voltage source. We found ST
brand BU505's failing at slightly more than 500V VCEO and the same for
Onsemi branded MJE8502. I etched a couple of BU505's with nitric acid
to remove all metal. One was a good tested one and one the other a
failed one. There was a completely different die size between the two.
The good one had a 3.3mm die and the bad one a 1.8mm die. The good one
had the markings etched and the bad one had markings printed. These
devices are often used for switchmode supplies and horizontal drive in
CRT's, where circuit designs may not ever allow the base to be open
circuit, ie driven from a low impedance source, so I guess that many
users many not see the failures.

I presented the data to St Microelectronics and they confirmed the
likelihood of counterfeit devices. Now we will have to do incoming
VCEO checks of all batches until the situation improves. We try to get
these normally from mainstream suppliers, but sometimes supply
problems prevent this. Looks like we will have to get smarter with
purchasing though. This is the first time I have personally come
across this in 20+ years of engineering.

 

[Phil Allison]

It is likely this won't affect many, but we have good evidence of
counterfeit high voltage transistors from some suppliers. The types so
far affected are BU505 and MJE8502, these are 1500V VCES and 700V
VCEO. We noted failures in our products and traced to a very low VCEO
which I checked with a current limited voltage source. We found ST
brand BU505's failing at slightly more than 500V VCEO and the same for
Onsemi branded MJE8502. I etched a couple of BU505's with nitric acid
to remove all metal. One was a good tested one and one the other a
failed one. There was a completely different die size between the two.
The good one had a 3.3mm die and the bad one a 1.8mm die. The good one
had the markings etched and the bad one had markings printed. These
devices are often used for switchmode supplies and horizontal drive in
CRT's, where circuit designs may not ever allow the base to be open
circuit, ie driven from a low impedance source, so I guess that many
users many not see the failures.

I presented the data to St Microelectronics and they confirmed the
likelihood of counterfeit devices. Now we will have to do incoming
VCEO checks of all batches until the situation improves. We try to get
these normally from mainstream suppliers, but sometimes supply
problems prevent this. Looks like we will have to get smarter with
purchasing though. This is the first time I have personally come
across this in 20+ years of engineering.

** The topic of counterfeit BJTs has been discussed here on many occasions -
mainly in relation to the popular audio output devices like the TO3 pack
MJ1503/4 and MJ15024/5 and flat pack 2SC3281 and 2SA1302 devices.

Other devices are also involved and I got once even got some fake TO92 pack
BC639s - which were relabelled BC547s !! This page has a lot of info on
the matter:

http://sound.westhost.com/counterfeit.htm

The FACT is that while ever you continue buy from non-authorised suppliers
you WILL be sold fakes.

There is a whole industry in places like China & India creating them to
order by relabelling cheap and obsolete types as more expensive and popular
ones in the same pack.

Also and very importantly, doing your own Vce or Hfe testing is NOT an
answer - the counterfeiters will often supply devices that pass such basic
tests but still fail in service.

To be sure you are not buying sub-standard or re-labelled / fake BJTs you
MUST have a guarantee of origin ( means documented & traceable stock) and
only an authorised supplier of the brand can give you that.



...... Phil

 

[David L. Jones]

It is likely this won't affect many, but we have good evidence of
counterfeit high voltage transistors from some suppliers. The types so
far affected are BU505 and MJE8502, these are 1500V VCES and 700V
VCEO. We noted failures in our products and traced to a very low VCEO
which I checked with a current limited voltage source. We found ST
brand BU505's failing at slightly more than 500V VCEO and the same for
Onsemi branded MJE8502. I etched a couple of BU505's with nitric acid
to remove all metal. One was a good tested one and one the other a
failed one. There was a completely different die size between the two.
The good one had a 3.3mm die and the bad one a 1.8mm die. The good one
had the markings etched and the bad one had markings printed. These
devices are often used for switchmode supplies and horizontal drive in
CRT's, where circuit designs may not ever allow the base to be open
circuit, ie driven from a low impedance source, so I guess that many
users many not see the failures.

I presented the data to St Microelectronics and they confirmed the
likelihood of counterfeit devices. Now we will have to do incoming
VCEO checks of all batches until the situation improves. We try to get
these normally from mainstream suppliers, but sometimes supply
problems prevent this. Looks like we will have to get smarter with
purchasing though.

Yes, the only solution is to buy up sufficient stock from an
authorised supplier so you don't have continued supply problems that
force you to use the dodgy vendors.
Buy 10 times more than you think you'll ever need if you have to, the
cost will be trivial compared to what the fakes will cost your
company.

Dave.

 

[Phil Allison]

It is likely this won't affect many, but we have good evidence of
counterfeit high voltage transistors from some suppliers. The types so
far affected are BU505 and MJE8502, these are 1500V VCES and 700V
VCEO.

** Farnell sell the BU505 for a 2.30 each + gst in 100 off - have plenty
of stock.

http://au.farnell.com/1084459/semic...ku=stmicroelectronics-bu505&_requestid=209663

The brand is ST Microelectronics, guaranteed to be genuine & traceable from
Farnell.

The very similar MJE8502 is a *long obsolete* type - best forget trying to
get genuine parts from anyone.



....... Phil

 

[[email protected]]

** Farnell sell the BU505 for a  2.30 each + gst in 100 off  -  have plenty
of stock.

http://au.farnell.com/1084459/semiconductors-discretes/product.us0?sk...

The brand is ST Microelectronics,  guaranteed to be genuine & traceablefrom
Farnell.

The very similar MJE8502 is a  *long obsolete* type -  best forget trying to
get genuine parts from anyone.

......  Phil

Thanks for the info, we just got 500 ST BUL416 at $1.50 and they come
from proper vendor and test OK. Farnell for us is mostly R&D only, our
purchasing dept will only go there if desperate. The Farnell source is
good backup though, I'll tell purchasing.

 

[Phil Allison]

** Farnell sell the BU505 for a 2.30 each + gst in 100 off - have plenty
of stock.

http://au.farnell.com/1084459/semiconductors-discretes/product.us0?sk...

The brand is ST Microelectronics, guaranteed to be genuine & traceable
from
Farnell.

The very similar MJE8502 is a *long obsolete* type - best forget trying to
get genuine parts from anyone.

Thanks for the info, we just got 500 ST BUL416 at $1.50 and they come
from proper vendor and test OK. Farnell for us is mostly R&D only, our
purchasing dept will only go there if desperate. The Farnell source is
good backup though, I'll tell purchasing.


** The cretins in " purchasing " are your worst enemies - if they do not
understand the need to buy only components that carry their original maker's
guarantees and full traceability. Plus are from reputable makers too.

Let only the WESs, DSEs and Jaycars of this world buy from the scumbags who
sell non- traceable and counterfeit semis to any fool who will order them.



...... Phil

 

[[email protected]]

** The cretins in " purchasing "  are your worst enemies  

Hey, how do you know our purchasing people? LOL

-  if they do not

 

[Eeyore]

The good one had the markings etched and the bad one had markings
printed.

This is a typical 'give away' now. Makes some genuine chips a bugger to
read though.

Graham

 

[Eeyore]

Hey, how do you know our purchasing people? LOL

Purchasing people are the same the world over.

Graham