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I have a commercially-produced board with an Altera EPF10K30-series FPGA. There is an abnormally high current draw on the board. Where +5V should be present, there is only +2.6V.

When comparing thermal images of a known good, working board to the defective board, it is clear the FPGA is getting much warmer on the defective board than it should. But interestingly enough, the heat bloom is around the entire perimeter of the FPGA. What could be causing something like this to happen? If one or two I/O's were shorted, for example, wouldn't the heat flare be around the pin driver and not the whole chip?

I realize the metal piece in the center of the package could be hiding the fact that the whole chip may be getting hot, but it sure seems to be an even heat all the way around it. I'm used to seeing heat from the center where the die is, not around the entire device.

EDIT 08/30/23

I covered the chip with electrical tape to even out emissivity and now I can see the whole device is heating up nearly evenly (animation added below). Now the mystery to solve is, why is this happening instead of just one hot spot as would normally be the case of a shorted I/O, etc.?

Link to follow-on question (and answer)

FPGA hot around perimeter

Comparison of a working board and overheating FPGA:

Comparison of two identical FPGAs, one working, one overheating

Altera FPGA

FPGA covered with electrical tape heating up over 52 seconds:

Animation of FPGA heating up

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    \$\begingroup\$ The I/O pads (blocks) are located around the periphery of the chip. They could all be damaged, though not likely, unless something bad happened to the I/O bank voltage. \$\endgroup\$
    – SteveSh
    Aug 29, 2023 at 21:46
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    \$\begingroup\$ Based on previous experience in a normal MCU you could definitely see the pins with a short with the thermal camera as distinct hot spot, which could be used to find the root cause much quicker. So this is looking quite odd. \$\endgroup\$
    – Arsenal
    Aug 30, 2023 at 7:55
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    \$\begingroup\$ With the number of circular marks on the chip, triple-check that it is mounted correct way around. Compare the text orientation against datasheet specification. I have had even professional PCBA companies fail this. \$\endgroup\$
    – jpa
    Aug 30, 2023 at 7:58
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    \$\begingroup\$ My FLIR is low-res at 320x240 so the images will not be sharp. The board has been operating perfectly for over 20 years, I can confirm the chip is not installed incorrectly! Clock is stable at 10.00MHz, the same as it has been for two decades. \$\endgroup\$
    – jfriend
    Aug 30, 2023 at 15:26
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    \$\begingroup\$ As has been suggested (and I fully agree), we're onto a new problem than the original question about the heating around the perimeter. As such, I'll open a new question as to why the FPGA is not working. \$\endgroup\$
    – jfriend
    Aug 30, 2023 at 19:11

1 Answer 1

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The shiny heat spreader/transfer section in the middle of the chip almost certainly has a much lower emissivity than the rest of the body so will show lower temp on the IR camera. If you used thermocouples, I suspect you would see similar temp across the whole chip.

You can also see how the darker lettering shows as higher temperature, confirming the effect of emissivity.

(This is also why copper busbars run cooler after a couple of years use. Initially they are shiny, so less radiative cooling. After a while they oxidize, darken, and their emissivity goes up significantly, reducing their equilibrium temperature.)

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    \$\begingroup\$ I will do this and report back with the results. \$\endgroup\$
    – jfriend
    Aug 29, 2023 at 23:25
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    \$\begingroup\$ You may find a bit of thin black tape works even better \$\endgroup\$
    – colintd
    Aug 29, 2023 at 23:28
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    \$\begingroup\$ @jfriend - Hi, "I'm now faced with the question as to why the whole chip is heating up and not just a single point on the die." That's a new / different question. Please don't continue with that question here as it's different from your original question, answered above, about why the FPGA's perimeter appeared to be the only part getting hot. You should include a link back to this question in that new question, for context but without relying on people reading this one. Thanks. \$\endgroup\$
    – SamGibson
    Aug 30, 2023 at 15:31
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    \$\begingroup\$ Agree there should be a new question. Would be useful to know whether any functions of board still work, or if whole thing dead. Also good to know if current draw has gone up despite voltage going down. Also useful to know exact part number, and whether you have verified program integrity? \$\endgroup\$
    – colintd
    Aug 30, 2023 at 18:48
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    \$\begingroup\$ I will open a new question about the FPGA's lack of functionality. This "perimieter" question has been solved, it was only uneven emissivity. \$\endgroup\$
    – jfriend
    Aug 30, 2023 at 19:14

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