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STM32L151RET6 chips faulty/bad/fake ?

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DeanA:
A local contract PCB manufacturer has asked me to look into whether a recent patch of STM32L151RET6 chips he has soldered onto customer’s boards could be faulty/bad/fake.  I’m not very familiar with these devices (yet) or the operation of the boards they are used on.
 
The newer chip on the left is not working as expected (ending with 1.3).  If the chip is replaced with one of the older batch chips (on the right, ending with 1.1) the boards work as expected.
[attachimg=1]

The programming sequence seems to work the same for both devices (although verify comes up with an error for both, perhaps the memory is locked or something).
The boards do operate to a certain degree even with the newer batch chips, flashing LEDs and generating some beep tones, so the chips do have some operation.  We are still trying to get some more information from the original designer of the board, but he no longer works with that company so may be difficult.
Has anyone experienced similar problems with these STM32L151RET6 chips.  Is there known fake or faulty devices on the market or something.  Or is there some difference with the 1.1 / 1.3 that could be the cause?
One thing I thought was a bit strange, the barcode on the original packaging from the supplier has been blanked out.
[attachimg=2]
Thanks in advance if anyone can shed some light on what the problem may be or where to investigate further.  I will try and find what the 1.1 and 1.3. signifies.

tom66:
If the chip appears to operate 'as normal' I would say it is vanishingly unlikely to be a fake.  However, it is possible that they are recovered and cleaned up from older PCBs (though they look pretty good for this) or it's possible there's a pin compatible variant e.g. without an ADC peripheral that has been remarked.  That could create issues as software would appear to work but as soon as a missing peripheral was accessed it is quite likely to experience 'undefined behaviour'.   

If the STM32's have a device ID, it's worth trying to extract that and comparing it.

It's also worth getting the customer to write some test firmware that exercises the chip, rather than the full suite of software.  Hopefully they have the source code from the original software before the engineer left them, otherwise they are up a certain creek without a paddle.

It's not uncommon to blank out supplier barcodes on greymarket products, as these parts are often sold without authorisation and the supplier doesn't want to lose any deal with ST.  We've had Zynq FPGA's with their 2D barcodes erased, on each device, in the past.

DeanA:
Ok, maybe nothing to do with the marking in bottom right hand corner (11 or 13), looks like it's just date code as shown in datasheet
[attachimg=1]

pcprogrammer:
Take a look at the chips in your photo. The one on the left is Y 0 W 51 and the one on the right is Y 7 W 34

A bit of a problem with the year is the single digit, so hard to say how old it really is.

No idea about the 13 and 11 though.

HwAoRrDk:
Year '0' is probably 2020, and year '7' probably 2017. Especially when you consider that 2020 matches the date on the label shown.

Is it me, or is the style of the legs different between the two chips? The one on the right appears to have legs that are wider at the top where they meet the plastic.

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