Here is one descenting vote.
There is another side to this, it does make field repair that is done away
from the primary site easier if components are identified; less
interpretation of prints, overlays or whatever else is done to find the
suspected problem part.
----------
From: [log in to unmask]
To: [log in to unmask]
Subject: RE: FAB: Silk-screen ink on surface mount pads
Date: Thursday, May 30, 1996 7:34PM
I totally agree with all who responded to Lou Hart's
question about legend ink on surface mount pads. It should
be unacceptable, and spec'ed out as such. My company
standardly clips (removes) any legend ink falling within
.008" of a solderable feature, due to the tolerancing
required for the screen print operation.
I would like to take this conversation one step
further, however. Why are we still using silkscreens on our
circuit boards (other than for hand assembly)? When the
board shops clip silkscreen alpha-numerics from solderable
features, "R"s start looking like "P"s, "B"s like "3"s, etc.
Board designs are getting tighter and tighter, and there's
barely any room for this stuff anymore. Folks are being
charged an average of $0.50 a side for silkscreens, and now
with double-sided surface mount, we're dealing with two
silkscreens, or a buck a board! It's amazing how most of my
customers are looking for ways to save pennies on their
boards, but don't seem to mind shelling out money for
silkscreens which in many cases are becoming next to
impossible to read. I realize that not using silkscreens
requires a culture change, but more and more of our astute
customers are taking a second look at whether or not they
are really needed, and some have taken the plunge and
discontinued their use.
I certainly don't want to disgruntle anyone (especially
inspection folks!), but maybe it's time to evaluate whether
silkscreens are really of any value, or simply a dinosaur
from the past. Thanks for letting me throw in my $0.50!
Regards,
Tom Coyle
Field Services Engineer
HADCO Corporation
|