UNO chip slightly melted

Hello all,

I've been reading these forums for a couple of months but only just got round to registering because I've just noticed one of the chips on my UNO is a little bit melted. The small square chip to the left of the TX and RX LEDs, it looks like it's labeled ATMEL MEGA8[possibly a B]U2, but the left hand side is melted and the board around it is slightly yellower and shiny, I'm pretty new to this but I think it's delaminated, between the chip and what I think is a crystal (the silver rounded rectangle labeled SPK16.000Y).

I plugged it in to see if it still works, the ON LED does come on but I can't tell if all the pins still work and so on. Can anyone tell me what this chip does and what I could expect to happen if it's damaged?

I've only just noticed it so I'm not sure what caused it, but I was running a 7-segment display without any resistors yesterday (schoolboy error, research afterwards revealed that this was a bad idea), also I just put together a Proto Shield kit and the guide I used said to plug the male headers into the Arduino's pins then solder them to save time, could the heat from the soldering iron (which seems to have been sufficient to singe the board and delaminate it around every contact I've soldered...) have caused this?

I managed to get a photo of the damage:


The 8U2 forms the USB interface to the main Atmega 328. On older boards this function was performed by an FTDI USB/Serial chip. If the 8U2 is fried you won't be able to upload sketches or use serial through the USB.

Ah I see, thanks for the info. I just tried plugging the board into my computer (which recognised it) and reuploaded the sketch and it did so with no errors. Is it possible for the chip to be damaged enough for it to be able to upload sketches but not communicate over serial, or is it either working or not working? Also, how can I find out what caused the damage? I'd imagine if the 8U2 also deals with the USB as a power source (as it is how I power the board) could asking for too much current cause this?

Also, if it were to blow, would it be possible to use an FTDI board designed for Arduino-type boards without USB ports to communicate with the UNO?

Thanks again!

The uploading of sketches proves the serial is working (both ways), so there shouldn't be any problems. Difficult to say what melted the chips case, soldering near it is a likely culprit. Most of the FTDI board's I've seen have an in-line 6 pin plug to fit in-line 0.1" header pins. But if you could connect it to the Uno it should work. The power drawn from the USB doesn't come through the USB chip, it has its own connections to the USB power connectors. The USB chip is connected to this put only draws power for itself.

Thanks again, I guess I’ll put this down to beginner’s luck and be more careful in future!

Is it melted or is that just residue flux? My Uno also as this flux residue on it.

Some unofficial boards also have a kind of varnish finishing through out that may look like what you're seeing, apart from the yellow thing which sounds like flux residue.

It's an official UNO board, but you're both right, it's not actually melted at all; I scraped it with my thumbnail and it just came off. How did it get there, though? I've never noticed it before, I'm pretty sure the board was nice and clean when I first got it (in November).


How did it get there, though? I've never noticed it before, I'm pretty sure the board was nice and clean when I first got it (in November).

The residue has taken some time to oxidize. I noticed some flux residue on my Uno recently and cleaned it off with some alcohol (the rubbing kind, not the the drinking type.) Like you, it looked clean when I first received it.