gEDA-user: 274x Gerber Files

[Ryan Seal]

>
>> I guess I didn't think about it that way. When I fill in my order, I
>> am required to check the polarity of each file submitted. So you are
>> telling me that my soldermask would positive then - right?
>>     
>
> Welcome to the confusing world of gerber.
>
> The soldermask plots are negatives, so check the negatives box.  The
> other layers are positives.
>
> The confusion is that the polarity of a layer is NOT the same as what
> the layer ends up looking like.  It's a means of defining the layer;
> either by drawing the parts you want or by drawing the parts you don't
> want.  In the case of soldermask, we draw the parts we don't want -
> the holes.  But the layer is the mask, hence we tell it we're drawing
> HOLES in the mask, not the mask itself.  If the layer were positive,
> we'd have to draw a lot of complex polygons to define the mask shape.
>
> Also, sublayers within each gerber can have a dark or light polarity,
> which basically lets you draw or erase within each layer.  In theory,
> we could have had a positive mask layer, drawn a big (dark polarity)
> rectangle, then erased (light polarity) the holes.
>
>
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>   
Thanks for the help,
Ryan