I had a case a few months ago that seems might be related to this unit
conversion problem. I had created a donut shaped fine pitch shield made up
of concentric 4mil arcs, each 8 mil radius larger than the previous arc. The
two sides of the PCB had traces lined up with the spaces on the opposite
side. Each side had about 80 concentric arcs. About 30 arcs into the
structure an error occurred. An arc was skewed. It crossed other arcs. The
matter was not noticed until the board house examined the files with an
independent gerber viewer. Protel 99SE and Camastic both showed this arc in
the proper position while Gcprevue showed it crossing other arcs. To fix it
I drew the arcs in metric units and the arcs appeared properly in both
Camtastic and GCPrevue. It would seem that Protel 9SE and Camtastic must
share some unit conversion code that has a bug.
Dave Eloranta

-----Original Message-----
From:   Leonard Fischer [mailto:[EMAIL PROTECTED]]
Sent:   Monday, December 17, 2001 5:13 PM
To:     'Protel EDA Forum'
Subject:        Re: [PEDA] bug plotting rotated fill

Wow.  That is interesting and kind of amazing that it is workable.  And the
first paragraph where you just said it was a board with submicron precision
really threw me for a loop.


It seems to me that part of the issue here is that Protel and Camtastic are
both designed for larger physical boards.  Ideally of course Altium would
fix the precision issues.  If they don't, or don't quickly enough to do what
you need, could you work at some multiplication/magnification of the final
scale, say 10x, then just "photographically" reduce the Gerbers?  I'm
assuming there is some way to do that (Camtastic?), not that I know how.

This could help with the precision issue in Protel and the magnification in

Just like working with 4x decals and tape!

I'm also assuming that the ceramic module is relatively small compared to a
PC Board - I'd be interested in hearing more about the ceramic module, like
how big it is and what kind of components you put on it, if that's not

Len Fischer
Trax Softworks

-----Original Message-----
From: Abd ul-Rahman Lomax [mailto:[EMAIL PROTECTED]]
Sent: Monday, December 17, 2001 11:10 AM
To: Protel EDA Forum
Subject: [PEDA] bug plotting rotated fill

I'm working on a board which requires high precision, in the submicron
range. Theoretically, Protel supports photoplotting with four-place decimal
metric, i.e., one-tenth micron resolution; however, I ran into some
problems with PCB and with CAMtastic.

Rotated fills, which are not flashed but which are drawn, were seen to have
some stray draws. I've sent files to [EMAIL PROTECTED], but for
our bug list, I am also reporting the matter here.

That rotated fills (and pads, I expect) are drawn instead of being flashed
is a bit distressing; this board already generates a lot of data and
drawing those fills will make the gerber files huge. Rectangles (and other
shapes) can be created with RS-274X Aperture Macros, which include a
rotation parameter. They would then also be importable as single primitives
(with appropriately modified gerber import routines.)

Fortunately the fills only occur on one layer which will not be fabricated
with the "PCB" (it is a multilayer co-fired ceramic module) but will be
added later as a separate metalization on the top of the module.

Then, looking at the files in CAMtastic, the aperture tables did not
properly import, there were errors in aperture creation  on the order of
1.5 microns. This is a bit hard to fathom; a metric 150 micron draw
embedded in RS-274X should become, one would think, a 150 micron aperture
in the CAMtastic aperture table, but it doesn't, instead it is 149.9
microns. (Some other apertures had higher deviations.) I'd guess that
metric apertures are being translated to inches on creation, then displayed
back as metric. But the aperture tables were editable to the correct
values, so it is not that the database does not support sufficient

However, the maximum zoom level in CAMtastic does not provide as high a
magnification as does PCB, it was barely adequate, if cramped, for working
in the micron range. PCB provides plenty of magnification before it refuses
to zoom in further, it looks to me like roughly 0.1 micron per pixel.
Abdulrahman Lomax
Easthampton, Massachusetts USA

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