Ancestors

Toot

Written by Darrell Harmon on 2024-09-29 at 03:33

I think I killed the HBM Virtex in getting it off the board. I shouldn't have trusted the thermal camera as much as I did. It was showing 220 C when the device came off but I think it was much higher. The usual cue of the solder melting was obscured by some remains of corner bonding I was unable to remove prior. Some delamination in the package, VCCINT is 0.001 ohms to ground.

That was an unfortunate mistake as I won't get another another of those. Back to the original plan of multiple XCKU5P.

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Descendants

Written by Darrell Harmon on 2024-09-29 at 03:38

The delamination is on the top of the part in some layers using resin clad copper and no fiberglass.

I did bake at 125 C for 4 hours prior and it was preheated to 150 C before any hot air.

I probably should have practiced more with junk graphics cards for experience with giant packages but the edge bonding still would have been an issue.

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Written by Darrell Harmon on 2024-09-29 at 03:40

There was more edge bond on the corners than the Xilinx docs call for. It was only supposed to go slightly under the part, not touch the balls but it went past the first row of balls in places.

I knew it was a gamble.

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Written by Marsh Ray on 2024-09-29 at 04:11

@dlharmon 😭

Perhaps a cheap (I mean cheap like $250) CNC machine could be used to grind or mill away the PCB material to get to the edge bond.

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Written by Darrell Harmon on 2024-09-29 at 04:14

@marshray I actually had the thought of milling the PCB away from the chip and wish I did now.

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