Electronics > Manufacturing & Assembly

Itead brd outline, which layer?

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--- Quote from: gregariz on April 10, 2013, 08:07:22 pm ---I think including the keepout/board outline in a layer like the lop layer etc is somewhat confusing / non-standard practice. In a file where internal cutouts are needed in the .gko I imagine it could be unworkable to include them in a signal layer.

--- End quote ---
My thoughts exactly

Trying to figure out what the best practice would be for outlines. So far I've done them in top silk, but I can see how this would be a bad idea.

As for using the .gko as board outline, see for example this bit:

"The keepout layer is intended to be used by the automation in Protel to guide the automated parts placement as well as the auto router by defining areas within the design that should be avoided by these functions.

This function allows the designer to outline the areas available for these functions thus excluding all other areas.  In many designs this boundary is the same as the boards’ outline and for some designers this is always that case so for them the keepout layer (output as the .gko Gerber file)  has become synonymous with the board outline.

However, many designers actually use the keep out layer for its' intended function and thus this does not represent the outline.  These causes a lot of confusion because the outline in the keepout layer is often very similar to the board outline but not exactly the same.  It is because of this that we do not assume that the .gko file should be used to represent the board outline.

Protel offers multiple mechanical layers that are intended for supplying the outline in the CAD data (typically the .gm1 and .gm4 layers are used for this purpose) or the outline can be added to the drill drawing (.gd1 as an example).  We suggest that you use these layers for supplying not only the drawn outline, but also add confirming dimensions to these layers as well.  If your design protocol requires the use of the .gko files for representing the boards outline please detail that the .gko files should be used for the outline in a readme file or in the Fabrication Print.  Otherwise your order will be placed on CAM hold pending this confirmation."

So for future pcb's I think it just might be best to put the board outline on a seperate mechanical layer. Is there any prefered standard, or is Mechanical 1 just as good as Mechanical 3? Right now I have mechanical 3 as the board outline and mechanical 4 as panel outline. For straight up pcb gerbers I can then use mechanical 3 as the outline for gerbers, and when I want to combine boards onto a panel I draw the new outline on mechanical 4. That way I don't have to edit my pcb source files just because I happen to want to put it on a panel this time.

Anyways, is there any standard? Apart from the "so many standards, you can always pick on you like" kind of standard. :P

And suppose you put your outline in a seperate gerber, what do you call it? .GM3 / GM4 in the above example? Something else?

In my experience .gko has been the most commonly used file extension for a board outline but the way I see it as long as the board outline is in a separate file you can rename it to whatever you like. I notice that batch pcb simply like to call it something like .outline

Programs like mentor call everything with the same extension. Something like .pho IIRC (for photoplot). There doesn't seem to be much of an agreement with regard to names, other than you see alot of .gko. I've seem some programs just number them. Rimu used .g26 for all outlines.

.gm seems to be a reasonable one to pick, however my understanding was that some of those were for mechancial operations like countersinking and v-scoring, so that may confuse other people.

Sorry.. not much help. Maybe .outline is safest.

Edit: I would add that when I worked with some of the larger companies that have specialized cad people, usually orders are accompanied with a 2D autocad type drawing where instructions and dimensions are given so any confusion about what the final article should look like is addressed.


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