As Earl says this is most likely to be PCB related
from your description. I still see this when doing failure investigations and
can be a real show stopper.
Bob Willis
Electronic Presentation Services
2 Fourth
Avenue
Chelmsford Essex CM1 4HA
England
www.bobwillis.co.ukTel: (44) 01245
351502 Fax: (44) 01245 496123
----- Original Message -----
Sent: Thursday, November 15, 2001 6:28
AM
Subject: Re: [TN] ENIG-Black Pad
Get back to your board supplier as soon as possible and
discuss. I haven't
seen, or even heard of this problem in over six months
now. I am in touch
with many ENIG users - as designers, assemblers, and
test folks using mostly
the big board fab houses though some protos are
made in smaller shops.
I hope the problems is lessening because board
shops are doing a better job
with better plating/coating chemistries and
processes. Much has been written
on this problem on this forum, so look in
the archives.
Black pad is exactly as you describe and opens are easily
found during test
but that's very unfortunate as then it's way too late. As
received, you
cannot tell the problem exists.
Visually, upon device
removal, non-wetted pads appear black where
non-wetting is observed often
with solder "bumps or ridges" where wetting
did occur.
There is no
possibility of rendering the black surfaces solderable. You
can't scrape it
off and no matter how many times you try, you cannot solder
to it though I
did once have success taking the boards back to the supplier
and have them
HASL coated after stripping off the surface coating.
Wish you the very
best in your unfortunate
situation,
MoonMan
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