Steve

As Ingemar correctly pointed out, electromigration is NOT the same as electrochemical
migration. I'm a little puzzled by your description: if it was ECM, as would be the
most likely, the appearance would not be copper-coloured: difficult to judge the colour
but dark grey is more usual. Aslo, dendrites are non-adherent to the surface, so the
chances are you wouldn't see them, anyway, by the time you examined them. Any dendrite
formation is usually accompanied by some greenish deposits on the side opposite to the
"trunk" of the "fern". My guess is you may have somethinng a little bit more profound.
Now, I think a key phrase is the non-adherence of the mask. This is indicative of
contaminants, of some sort, under the mask amd these may be the cause of your problems.
I would really want to know a lot more about your boards, your processes, the
conditions of use and have the opportunity to examine and analyse them before really
pronouncing.

Brian

"Stephen R. Gregory" wrote:

> Hi All!
>
> I've learned about electromigration, and fortunately have never had a real
> problem with (that I know about anyway). But recently, we've had some boards
> returned to us that have failed for a short from VCC to Ground, usually at
> the same area on the board.
>
> It's beneath a keyed header that is hand soldered on the board. The first
> couple of boards we got back, we couldn't find the problem. But we just got
> back 3 more and I did see something. In trouble shooting we remove the header
> (it's got a plastic body that has the plastic key molded into it) so we can
> see if anything beneath the plastic.
>
> Well, on one board today I think I saw something. There's traces that run
> between the header pins and on one trace, it looked like the mask was not
> adhered to the trace well. Then looking at it under higher magnification,
> there was what appeared to look like these copper fern like structures
> between the trace and the anular pad of the PTH on the laminate.
>
> Will the dendrites be copper colored? All the pictures I've seen they have a
> silvery gray to white appearance...I guess it would depend on which was the
> cathode and which was the Anode in the scheme of things as to what the
> dendrites would look like huh?
>
> Has anybody else ever seen this?
>
> Thanks ya'll!
>
> -Steve Gregory-
>
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