The closest IPC comes to saying anything on the location tolerance on legends and
markings is from IPC-2221 (newly released):

para 4.6  "Liquid screened markings require clearances that are typically 0.4 - 0.5
mm from solderable surfaces."


Lisa Williams
IPC
2215 Sanders Road
Northbrook, IL  60062
URL:  www.ipc.org

>>> Don Vischulis <[log in to unmask]> 05/07/98 09:32PM >>>
John:

This is a subject that IPC has avoided.  The last specification that I can remember
was in the
+/-0.020" area, which is not adequate for today's designs.  You must decide what you
want for
your legend.  Conventional, screened legend can maintain somewhere between +/-0.015
to 0.010 inch
(optimum conditions).  If you are willing to pay for LPI legend, you should
experience +/-0.005".

The real question is why do you need tight registration tolerances?  Automated
assembly equipment
doesn't use legend to assemble the boards, and once the parts are on the boards most
modern
designs can't be read.  IMO, legends on modern designs should only be used for
warnings, assembly
identification, test points, and similar designations.  Assembly drawings (scaled
larger than
1:1) should be used for component identification.

Don Vischulis
[log in to unmask]

John Bauer wrote:

> Is there a specification that specifies the registration tolerance of the
> silkscreen legend to the PWB?

snip --------------------------------------

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet
################################################################
Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional
information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700
ext.311
################################################################

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
################################################################