Afternoon All!

Just sitting down for lunch, and I have a question about Non Solder Mask
Defined (NSMD)
BGA pads. I have a picture at:
http://www.stevezeva.homestead.com/files/MaskMisregistration2.jpg

Now according to IPC-A-600G, that misregistration is not rejectable,
"because the solder resist does
not encroach on the land except at the conductor attachment"...that's a
quote right out of the - 600. I've
looked at it very closely, the mask is right up against edge of the pad.

Knowing what kind of solder joint you're trying to acheive with a NSMD pad,
and having the mask up
against the edge of the pad, the solder is not going to wet and flow down
around pad like you want, right?
Is that a problem? Will that introduce the possibilty for reliability
issues? Can one reject these boards?

I've heard the statement made that if indeed you want a clear area around
the pad, a note needs to be
put on the fab drawing stating that. Because as it stands now according to
the IPC-A-600G, it is not rejectable.

Any thoughts?

Kind regards,

-Steve Gregory-
Senior Process Engineer
LaBarge Incorporated
Tulsa, Oklahoma
(918) 459-2285
(918) 459-2350 FAX
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