At 11:58 AM 7/12/01 -0400, [EMAIL PROTECTED] wrote:
>I'm completing my first board, in 99SE SP5, with connections to internal
>planes. I've noticed some questionable behavior and I'd like to confirm my
>experience is normal.
>
>1.) Protel does not create acceptable thermal reliefs for square pads. The
>thermal relief looks exactly the same as I would expect for round pad.
>
>Is there a way to direct Protel to create a specific relief for specific
>pads? Do I need to make all my pads round?
This has already been answered, but to be more explicit: there are no
flashed "pads" on internal planes. If there is a flash, it is a blowout
creating a clearance for a non-connected pad, and, unless you place it
manually, it is always round, since it is dealing with a round hole. When
the plot routines are going to connect the plane to a pad with a thermal
relief, all that is drawn are four arcs defining the relief.
You can control the arc parameters with
Design/Rules/Manufacturing/PowerPlaneConnectStyle. The expansion is over
the hole size.
>2.) In a split plane design, any pad must be fully within the defined area
>of the plane. If a pad overlaps with an adjacent plane then Protel may
>connect to both planes.
A pad does not need to be fully within the plane. But you may get a DRC
warning if a plane split crosses a pad which is to be connected to the plane.
>If this occurs will the DRC catch it or do I need to plan to be extra careful
>when inspecting the Gerbers? The on-line DRC doesn't appear to catch it. Is
>there a rule I can define?
On-line DRC will not catch this, but it *may* be caught by the full DRC. As
I recall, it is possible under some conditions to short planes together
with an imprudently placed pad. If possible, do not allow plane splits to
cross pads connected to the plane.
As I mentioned, you may get a DRC warning or error when a plane split
crosses a connected pad. DRC *should* detect whenever a plane split crosses
a hole -- my recollection is that it does detect this but the exact
parameters of detection have not been clear to me and I have not done the
detective work necessary to determine them. It never hurts to inspect
planes, there are quite a number of ways that they can go wrong.
The most common is that a pad will be isolated. You might have, for
example, a pattern of pads and vias around a pad that is intended to be
connected, and the blowouts for those pads and vias causes the nominally
connected pad to be isolated. DRC will *not* detect this, not with the
present state of the art of the Protel DRC. It is not a simple problem, or,
at least, it is much more difficult than detecting positive connections. I
don't know any CAD systems that do it, at least not any in Protel's class,
I'll let someone else comment on Mentor or Allegro or the like.
Router Solutions does make a tool that will verify negative plane
connections. Wolfgang told me, as I recall, that he essentially
flood-routes the plane and then looks for positive connection....
This has been discussed here for some time and I would not be terribly
surprised to see Protel 2001 have negative plane checking, it is an obvious
advance, but I have no positive indication that they are working on it.
[EMAIL PROTECTED]
Abdulrahman Lomax
P.O. Box 690
El Verano, CA 95433
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