Cam,
Firstly, what "rule for polygon clearance of 12mil" are you talking about? There is
a rule under "Manufacturing" for "Polygon Connect Style" and also one for "Power
Plane Connect Style" and also "Power Plane Clearance", but not one for "Polygon
Clearance".
You may be speaking of some specific "Clearance Constraint" that you have set up
that you have named "polygon clearance", but you will have to explain that one to
me.
I believe that the simple answer to your question would be to set the "Polygon
Connect Style" rule under "Manufacturing" to "Relief Connect", and then than set up
an additional "Clearance Constraint" rule which applies to "Scopes" of "Board",
"Board", and the "Connectivity" of "Same Nets", with the clearance of 12 mils, and
enable this Clearance Rule at the same time that you "Pour" your Polygon Planes with
a "Clearance Constraint" rule enabled which applies to "Scopes" of "Board", "Board",
and the "Connectivity" of "Different Nets" with the clearance set to 97 mils (i.e.
enable both rules, but only these two rules, at the time of the "Pour" of the
Polygon Plane).
If that fails, read on.
I am not quite sure that what you want can be done in P99SE with a specific "rule"
that would be set up by "class" etc., that wouldn't apply to the whole net EARTH as
a whole, or otherwise be complex enough to screw up.
I encounter the problem all of the time, where I want my Polygon Planes to have a
larger clearance or setback than my normal clearances, which sounds something like
what you are trying to describe below.
The trick is to remember that a Polygon Plane clearance is really pretty "dumb", in
that it is actually defined by the "clearance rule" ("Clearance Constraint") in
effect at the time of the actual Polygon "Pour" (i.e.: Each time you generate a
Polygon or "Re-Pour" ("Rebuild") it).
I generally make a "Design Rule" for "Clearance Constraint" which I name "Clearance
PP (for Polygon Plane)", with the "Scopes" of "Board", "Board", and the
"Connectivity" of "Different Nets", and the specific clearance that I want, which in
your case would be 12 mils, but in my case it would be larger than the normal
clearance for everything else.
Normally, this "rule" would be "off" (no "check" in the "Enabled" box) for normal
routing and board work, but then when I am ready to make my Polygon Planes, I
disable (turn off) all of the other "Clearance Constraint" rules, and enable (turn
on) only my "Clearance - PP (Polygon Plane)" rule, and than make or "Pour" my
Polygon Planes.
Again, please remember that every time that you "Pour" or "Re-Pour" (Build or
Rebuild) a Polygon Plane, that it "Pours" at the "Clearance Constraint" in effect at
that time, and that this means that if you have a Polygon Plane already set up, and
you double-click on the Polygon Plane to open it's Dialogue Box for any reason, that
if you click "Yes" to the question "Rebuild 1 Polygons?", that you are liable to
change the clearance of your Polygon Plane. If you really do have to "Re-Pour" the
Polygon Plane, you will have to go into your "Design Rules" and enable and disable
the appropriate rules, and then change them back again when you are done with all of
your "Pours".
Needless to say, if you want to have different clearances for different Polygon
Planes, such as for example for Polygon Planes on different layers, then the "trick"
to accomplishing this is simply to "Pour" (or "Re-Pour") them with different
"Clearance Constraints" in effect at the time of each "Pour" (or "Re-Pour").
Sometimes you may even need different "segments" of a single Polygon Plane in
different areas to have different clearances, such as for example an area around
certain "controlled impedance transmission lines" which may need larger clearances.
This can be easily done by actually making up your Polygon Plane with not a single
Polygon Plane, but using several different but overlapping Polygon Planes of the
same net name, and "Re-Pouring" the different segments with different "Clearance
Constraints" in effect for each "Pour". You may end up with a few little "uglies"
here and there, where the planes overlap, but that's what an occasional little
floating piece of "track" of the same net name (overlaid on the plane at that spot)
is designed to be used for, to clean it up, aesthetically speaking.
Yeah, I know it's a pain, but that's Protel. What else would you expect?
While someone else may come up with some other way to accomplish what you want to
do, for me this is a simple and effective way to accomplish the task that works
reliably for me from board to board (design to design), without any repercussions or
side effects, excepting the "Re-Pour" issue.
Unfortunately, in this case, like so many other things in Protel, you simply have to
manually override the system to get it to do what you want it to do, and every time
that you have to do something like this, you have to take the chance that it will
not be seen or understood by someone else down the line, which means that someone
else could easily screw up the design, in this case simply by "Rebuilding 1
polygons" [sic] (I don't think that Protel can actually "Rebuild" more than "1"
"polygons" at a time, can it?). To prevent such a problem from happening in the
future, you might place a "Note" just outside of the board perimeter, on some unused
mechanical layer, or possibly the same layer you use for the board outline (or even
on the Top Overlay, but again, just outside the board outline), something to the
effect of: "DESIGN NOTE: Polygon Planes poured with 97 mil clearance using
"Clearance-PP Constraint".
Yeah, I know, some idiot will still mess it up somewhere down the line in a future
revision, but what do you expect with this software.
Don't forget that you may have to "juggle" the "Clearance Constraint" Design Rules a
little bit when it comes time to do your DRC, or you might want to actually run a
few separate DRCs with different Rules in effect (possibly using a "copy" of the
database where you would delete the Polygon Planes with the smaller clearance so
that you could check everything else). Here again Protel's preprogrammed
"intelligence" (or specifically the lack thereof) really shines thru, but then
again, I don't think that I have ever done a design in Protel where the DRC didn't
screw up somewhere and complain about something that wasn't really an error (don't
get me started on this one . . . ). Please remember that the board is built to your
"Gerbers" and not to your DRC, and that sometimes the DRC may claim that something
is wrong where the board is actually right.
I hope this helps to answer some the issues you raise with your question.
JaMi
----- Original Message -----
From: "Cam Andruik" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Thursday, August 26, 2004 1:55 PM
Subject: [PEDA] Net with large clearance and polygon
> Help please.
> I want to set the net EARTH to have a clearance of 97mil. This is no
> problem, but when I place a EARTH net Polygon Pour it stays away from
> everything, including the EARTH Through Hole Pads by 97mils.
> Cannot figure out how to edit the rules so the Polygon will stay away from
> all nets by 97mils except EARTH net which should default to the rule for
> polygon clearance of 12mil.
> Any suggestions greatly appreciated.
>
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