Hello TechNet,

I've recently received some boards that have a defect I've never seen
before.

There is a linear depression in a 2oz outer copper layer on two out of 45
boards. One of the boards was on a solder sample panel, the other was
assembled with the defect.

The depression has the appearance of a wrinkle or groove, it is
approximately straight and square to the edge of the board. At its
widest point it is about 0.006" wide, and as far as we can measure it is
between 0.0015" and 0.002" deep. There are a couple of small delaminations
nearby (on a panel that has not been reflowed).

I looked through IPC-A-600 and did not find anything about this type of
issue. I don't have the equipment to microsection or x-ray the board, so
I'm not sure whether the foil is damaged under the plating (Which is RoHS
ENIG).

Hopefully this image link works:
https://snag.gy/Kx58Oy.jpg

Please let me know if you've seen this before or otherwise know how I can
find more information.

Thank you!
Tom Brendlinger
Senior Electrical Engineer
Superpedestrian, Inc.