i like Jim's second method here
the reason is that a PEM SO-440-XX standoff has an outside diameter of
0.166", whereas a 440 SEMS screw head with washer has an OD approaching
0.300" when you take into account a bit of drift in the hole
so using layer specific keep outs allows different a clearances for the
top and bottom
also you may want to increased the solder mask expansion quite a bit so
that the screw head does not tear it
if the mounting hole is non-plated then the reckoning of the expansion
is complicated by the fact that the pad is probably much smaller than
the hole and the expansion is calculated from the pad
a 'component' is definitely a good a idea for a mounting hole
there is, however, one point to watch out for at least in 99SE
i usually take such component mechanical details and copy and paste them
about, ditto little pin 1 arrow markers
the 'components' then acquire whatever designator prefix the program
feels like assigning (actually that happens at first insertion)
since these designators are generally hidden you may not be aware that
you have a mounting hole or a pin 1 marker named C69
one time this caused a bit of wasted time as i pursued what was a
phantom DRC problem
Dennis Saputelli
_______________________________________________________________________
Integrated Controls, Inc. Tel: 415-647-0480 EXT 107
2851 21st Street Fax: 415-647-3003
San Francisco, CA 94110 www.integratedcontrolsinc.com
Jim Parr wrote:
Very briefly,
You just need to set up a design rule that specifies this exception
Polygon <-> mounting hole (size/component/hole size) - whatever is
applicable - to get the result you want. I often have trouble thinking
the same way the design-rule dialogues work but persistence and patience
is a good start.
Failing this, a very reliable quick fix is to add a 'layer-specific keep
out' (circle or arc) primitive to ensure these special case clearances
are followed (remember that a net-name can be assigned to such a
primitive where polygons will pour over if the net-name is the same - NO
NET is the best course until you have a handle on this. 99SE help is
helpful on this subject. If you like this option, screw/bolt/mounting
holes can be easily created as proper component footprints with all
these clearance details that save you a lot of repetitive work for
something you often use.
Best regards,
Jim Parr
Adeel Malik wrote:
Hi Folks,
In my board I want to place the Polygon such that it is
drawn at a clearance of let say 100 mils from the mounting holes while
for the rest of the Board it is drawn at the clearance of 15 mils.
How can I accomplish that in 99SE.
Regards,
Adeel Malik
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