Friday, October 11, 2019

why decapping MCU's is so important

Got the next two MCU's from the lot in my hands. Those two proved, why it's so important to decap and secure MCU's, as Emulation-Simulations of the MCU's won't help you to rescue your real board.

Image Fight

I test all MCU's about PIN-connections before i start to decap it. to be sure that the MCU is at least "working" before i put my hands on it.

So i put the MCU in my programmer and got this:

No matter what i did, nearly all pins on the left side had no connection. Only GND had a connection, so i cleaned all other pins, tried again and got the same result.

So i started to open the chip. As it was already dead, i had nothing to loose. I checked the die with my bare eyes and didn't see any faults. So i put on some nail-polish and afterwards made the first pictures of the die with my microscope.

Look what i found:
Can you see it? Two wires are cut.
Now to the interesting thing, this is GND!!!

As i  don't have the equipment to fix this small wires, and solder those back together, i made my own little fixing-tool for it:

When i connected the two wires, i got connections to all pins and could read the mcu.

Sadly the dump matches the existing Image Fight (Japan) dump. As we didn't know for which region this mcu was, we were hoping it is for the missing World revision.

At least it was a great challenge. I'm pretty sure someone mixed up VCC and GND on the board and that's why these two wires got blowed up.


Brian already told me, before he shipped this package from the US, that one of the MCU's is missing many pins.
It was the MCU for Quartet and many of the pins got corroded and really broke away if you just looked at it.
After a short fixing job it at least looked like this:

The other side did look nearly the same, so basically about 20 of the 40 pins were at least partial missing.

The decap and Pin-fixing job worked out and it got constant reads after erasing the lock-bit.

Another mcu preserved!

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