i have created negative text this way, I put a sample on egroups some
time ago
bit of a pain though, don't think it's really nec

Dennis Saputelli

Abd ul-Rahman Lomax wrote:
> 
> At 01:43 PM 3/27/01 -0500, Thomas Sprunger wrote:
> >I am trying to find a way to place text and components on ground planes
> >(or polygon fills) and to make them an absence of copper (or Anti Copper
> >in Orcad). Is this possible in the PCB portion of Protel?
> 
> Anything is possible, even if we don't know how to do it.... :-)
> 
> A polygon pour will avoid and pour around track on its layer which is not
> assigned to its net. Gerber plots reduce strings to track. These facts can
> be used to produce negative text.
> 
> Protel has no true anti-copper attribute for primitives. Such primitives
> would have fairly drastic impact on many routines, I would think, so I
> would not expect it soon. However, positive-negative merges have been
> suggested and if Protel moves in this direction, it will become possible to
> have anti-copper. Normally we think of a photoplot merge as being
> subtractive-additive, i.e., the anticopper primitives are written to
> subtract copper from a solid layer, and then the normal primitives are
> written to add positive features. But anticopper as Mr. Sprunger is
> conceiving it would require additive-subtractive, or
> subtractive-additive-subtractive; eventually in the process negative shapes
> are drawn or flashed to remove copper from a solid region.
> 
> RS-274X supports such procedures, but Protel does not, because it is
> essentially more complex.
> 
> But we can make negative text, as I indicated above.
> 
> Photoplot some text. Import the plot, which will create track primitives
> representing the text. With appropriate clearance settings, pour copper
> around it; do not remove dead copper and, of course, the net for the
> polygon pour must be different from that of the track primitives (which
> will be no-net ordinarily). Lock the polygon and delete the original
> imported track. This block could be made into a component if you want to be
> able to move it about. A net can be assigned to it by Update or global edit.
> 
> I have not experimented with layer-specific keepouts for this except to
> find that layer specific keepouts cannot be created by global edit. Others
> have complained about this so perhaps we will see such a feature in the
> future. For now, one could manually check keepout for each track primitive
> reduced from the string and this would eliminate the necessity of deleting
> it. One could  modify such primitives en masse in the ASCII database itself
> (or in a spreadsheet???).
> 
> keepout fills can also be placed to create open blocks in a pour, and
> keepout arcs to create open circles.
> 
> As to strings on inner planes, that is extremely simple. Just place the
> strings. Any primitive placed on a negative layer, such as an inner plane,
> is anti-copper already. Protel has no other negative copper layers; the
> solder mask is a negative layer, though.
> 
> [EMAIL PROTECTED]
> Abdulrahman Lomax
> P.O. Box 690
> El Verano, CA 95433

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