Opps, not talking solder mask but silk screen. IPC-A-610 markings,
Clause 8.2 Screened Markings shall not interfere with soldering
requirements of section 12. Even if your design guys blew it ( IPC 2221
clause 4.6 warns designers not to put markings so close to lands as to
impair solderability), the board house should have contacted the user
and requested disposition, before proceeding with marking.

I would add another caution. Screened marks can act as shims under the
stencil. The marks can vary in height. This can cause variation in
solder paste deposition that can produce variation in process
performance. It can easily be enough to introduce squeeze balls and
tombstones. You will see board to board and lot to lot variation. Not
good. Keep the marks away from the land patterns.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of West, Jim
Sent: Wednesday, September 24, 2003 3:33 PM
To: [log in to unmask]
Subject: [TN] Silkscreen in solder pad


Hi,

Is there a IPC standard for how much, if any silkscreen can overlap a
solder pad?  What process is recommended for cleaning a solder pad with
silkscreen overtop of it?  Examples I have are silkscreen on 0805 pads
halfway through it, and some with silkscreen just barely touching.

Thanks,
Jim
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