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 precisions.

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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