Steve,
Very
glad you decided to stay with us after all...
My
solution to the problem of saying or asking stupid things on the Technet is to
keep my replies off-line whenever they are questionable (to me anyways). That
way the whole group doesn't witness my ignorance. Then when I get straightened
out, I can look all-knowing and wise when I post something sensible. ;-) It took
several ignorant comments and questions from me before I learned, and my
"filter" may still occasionally fail.
We all
have said at some point "I'm not going to do THAT again!", and of course, as is
human nature, we do it again, and feel rotten. Being able to forgive one's self
is important.
Anyway, back to the question you asked, the trace
definitely looks to me like it's reduced by more than 20%. What happened was
either the etch resist (tin) was scratched after it was plated and before it was
etched, allowing partial etching of the trace, or as you suggested, something
prevented plating in that spot to begin with (like a sliver of photoresist
lying on top of the trace when in went in to pattern plate). Too bad your
incoming inspection missed it. Or more appropriately, that your board fab
shipped it to you in the first place.
Tim
Reeves
Hi
all!
I'd like your opinion on something. We're building a prototype
assembly for a customer, and discovered something at final inspection that we
didn't see when we received the bare fabs. We ordered 16-boards in four, 4-up
panels.
We found a trace that has a spot where it looks like it didn't
plate up during final plating. Take a look at "Trace Thickness" at
http://www.stevezeva.homestead.com
There's 4-boards we've found that
have this problem, 1 on one panel, and 3 on another panel, and of course
they're all built up. The 6012 says that thickness can't be reduced by more
than 20% of the minimum conductor thickness. I can't really tell if it's 20%
or 50%.
I've sent pictures both to our customer and the fab vendor. The
customer wants the spot repaired, and there are a number of ways to do that.
The fab vendor says it's not a problem because the stack-up drawing calls out
1-oz. copper after plating on the surface layer, and they said that there's
more like 2-oz. on the surface layer, so there shouldn't be any problem, at
least that's what I was told, I didn't speak to anyone directly. The stack-up
is on my page too, look at "Stack-up"...
The first question that comes
to my mind, if 1-oz after plating was called on the stack-up, why was 2-oz
plated? Or is that normal?. The drawing references our customers internal spec
for fabrication, but it uses MIL-PRF-55110 for references.
What are
your opinions about this?
Thanks everyone!
-Steve
Gregory-
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