At 09:25 14.03.02 +0000, you wrote:
>Quoting Brad Velander <[EMAIL PROTECTED]>:
>
> > Kiernan,
> >       Ian's explanation below is correct. What you're seeing are drawn
> > pads rather then flashed rectangular pads. A major shortcoming of Protel
> > if
> > you are doing very fine or finicky work. As for your soldermask
> > encroachment, that will not be an issue because the soldermask pad will
> > be
> > drawn similarly and won't encroach.
>
>Thanks guys. We're using FPC connectors with an 0.3mm pitch. I've got the 
>pads
>designed so that there's virtually no visible land after soldering, so I will
>get soldermask encroachment under the pad even though the soldermask lines up
>with the copper because the pad that I'm getting out of the gerber is smaller
>than the one on the screen (ie smaller than the pin). At the very least, I'll
>get severe solderballing.
>
>I've put a sample of the gerber output for a couple of pads below and I 
>wonder
>whether anyone knows enough about gerber to see if there's a quick fix that
>will produce the correct result. One of the pads is supposed to be a 
>rectangle
>and the other actually uses the octagonal option.
>
>Are there any other Non-WYSIWYG features that I should know about before I
>spend too many hours on this?? I thought gerber output was the gold standard
>for PCB packages.

Yes, if you use soft-arcs. They are made from small track segments. If you 
have a polygon arround a round pad, the clearence from the poly to the pad 
is slightly smaller as expected. The smaller the pad (radius) the larger 
the error.
Workaround: Use arcs in the gerbers.

Edi




>Cheers
>
>
>Kiernan Fitzpatrick
>
>
>%ADD10C,0.0600*%
>%ADD11C,0.0150*%
>D10*
>X102723Y83933D02*
>X102879Y83353D01*
>D11*
>X101100Y83387D02*
>X101268Y84015D01*
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>X101356Y83862D01*
>X101549Y83810D01*
>X101446Y83424D01*
>X101253Y83476D01*
>
>
>
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