Why does not the DRC tell the planes are shorting?
============
Henrik Thurfjell
Megatron Engineering
Direct 408 737 1718
FAX & Messages 408 739 2429
email: [EMAIL PROTECTED] or [EMAIL PROTECTED]
----- Original Message -----
From: Andrew Lowy Sybrandy <[EMAIL PROTECTED]>
To: Multiple recipients of list proteledausers
<[EMAIL PROTECTED]>
Sent: Friday, February 09, 2001 1:54 PM
Subject: RE: [PROTEL EDA USERS]: Just a hole
> Bingo!! Thanks Dwight, and everyone else that replied.
>
> Now I understand why they said the inner planes were shorted. I assigned
> the pad to the top layer, and it was plated. Duh!!
>
> >From what I've gathered in all the responses, I can summarize what I've
> learned.
>
> 1. Mounting holes should be multilayered. This prevents shorting to inner
> power layers.
> 2. Don't forget about additional mounting screw clearances!! Do something
> to prevent traces from being routed beneath the head of the screw, as
> tightening the screw may scrape off the solder mask and cause a short.
This
> can be accomplished by defining the X and Y size larger than the OD of the
> head of the screw.
> 3. Define a large enough pad to provide for imprecise drills. If the
drill
> is too large on a small pad, this may also cause shorts between layers.
> 4. Of course when one defines a pad, one must also choose a net on which
to
> place that pad. I believe this should be "No Net"
>
> I still have a one question:
>
> 1. Why is it important to change the X and Y size to zero before
production.
> It was said this prevents "flashing" from within the Gerber file, but I
> don't know what that means.
>
>
> > Andy,
> > As far as why AC said the holes shorted, I'll take a guess: If
> > you made the pads single-layer (e.g., Top Layer) instead of
> > MultiLayer, that's why. If you look at the PCB in single-layer
> > mode (Shift-S), for a single layer pad there won't be 'negative
> > copper' on the inner planes to keep the planes away from the hole
> > edges. So if the hole is plated, you've got a definite short. If
> > unplated, your mounting screw could still easily short the planes.
>
>
>
>
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