Lou,

I also agree with Roger and Lisa. Ink should not be allowed on surface 
mount pads. For thru-hole pads, 
however, it depends on the classification of your design. For CLASS 1 and 2 
designs it is acceptable as long as
the ink does not get into the hole. For CLASS 3 designs it is not allowed.

Reference IPC-A-600D section 12.2 and 12.3


Lou Takach
Union Switch & Signal Inc.
412.688.2574
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Subject: Re: FAB: Silk-screen ink on surface mount pads (fwd)
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---------- Forwarded message ----------
Date: Tue, 28 May 1996 08:43:24 -0700
From: Bilal Khalaf -Applications <[log in to unmask]>
To: [log in to unmask]
Subject: Re: FAB: Silk-screen ink on surface mount pads


Lou,
I agree with Roger.  Silkscreen on pads should be addressed at design
stages and should not be allowed on pads.  Most of the Gerber editors have
the capability to clear the silkscreen from any pads and hopefully, your
designers/contractors are aware of that capability and know they should not
have silkscreens on pads: SM or thruhole.

bilal


>     Lou,
>
>     We have never allowed silkscreen ink on the pads.  We have had our
>     vendors put the silkscreen on the pads before due to misregistration
>     or errors in their fab artwork.  We have seen solderability problems
>     due to this kind of defect.  If it's not in an industry spec., then 
it
>     would have to be a requirement in your company's specs. or your
>     individual specs.  PC boards should be DESIGNED such that there is no
>     silkscreen on the pads.
>
>     Regards,
>
>     Roger Held
>     Hitachi Computer Products (America), Inc.
>
>
>______________________________ Reply Separator
>_________________________________
>Subject: FAB:  Silk-screen ink on surface mount pads
>Author:  [log in to unmask] at Internet-HICAM-OK
>Date:    5/28/96 8:42 AM
>
>
>Recently I have seen PC boards with silk screen ink on surface mount
>pads.  Is any of this allowed?  Looking at the PC board IPC standards, I
>don't see this subject addressed.  May I have some guidance?
>Lou Hart   412-858-6117
>
>
>.
>