At 11:42 AM 5/25/2006, Brad Velander wrote:
>Abd ul-Rahman,
> While I understand your comments, I offer the following.
> Importing Gerber back to Protel is not the solution for this
> documentation issue because of course the Gerber contains no
> intelligent part information.
The gerber solution is only for the purpose of producing flipped
human-readable documentation; I've never needed to do this except for
bottom-side assembly drawings. Yes, the gerber contains no
intelligent part information, but this solution allows a single
drawing to show both top and bottom assembly. If you want to make
separate drawings, you might do something different, but.... you
might still do what I suggested, only in a separate file.
> Using Gerber would definitely not bring anything to the table when
> creating P&P files because of the loss of the intelligence. Our P&P
> files must have the bottom side flipped and re-oriented because our
> manufacturing insists on have the documentation oriented as viewed
> by the user and we manipulate these at the PCB file level prior to
> generating P&P files and prints from a flipped and often rotated
> version of the original PCB file.
I'd think a better solution would be a transformation of the bottom
side Pick and Place file, for the file part of it. This would then
match the assembly drawing created as I suggested. I don't recall if
Protel will mirror a P&P file, but it would be terribly easy to write
a utility to do it. And I'd think any assembler would have software
to do this....
The original PCB file is all that machine intelligence needs; if the
rotation and reference information are correct in the footprints, I'd
think manipulation would not be necessary.
> Similar issues arise when creating solder paste screens
> because we must manipulate footprint apertures on certain specific
> footprints, thus not having the footprint names would significantly
> hinder our ability to identify the footprints needing manipulation
> or doing it in an intelligent global editing type manner.
All that data is in the intelligent part of the board. The
bottom-side assembly drawing is just that, a drawing. Yes, you
regenerate it whenever you make changes to a board. It would be nice
to have a facility to do this; I think at least one service bureau
created a utility for this purpose.... Again, solder paste screens
are created from the Paste Mask layer, and the manipulation would be
done in the intelligent part of the PCB board file. The "dumb" part,
the bottom assembly drawing, is not used for generating pick and
place files, nor should it be used for paste masks. It's just to
present a bottom-side view to a human....
Assembly drawings may or may not show SMT pads. If placement density
is such that there is no room for pads and component legend
("silkscreen") then I may autoposition legend inside the part, and
print it in the assembly drawing, but not in the silkscreen.
Without going into all the details, the goal is to have a single
board file that automatically will generate the needed fab files.
I've always provided pick and place files that were not mirrored, and
I never saw a fab house that wanted to be provided the flipped files.
If they want to flip them, it ought to be practically one-button for
them. Just like I don't flip bottom copper. It is less confusing if
everything is generated as viewed from the top. Fabricators have been
dealing with this for donkey's ages. (Yes, they mirror them in
photoplot, or, perhaps more accurately, the *don't* mirror them,
since with some processes they would mirror the *top* plot. Since I
don't necessarily know which process they are going to use, I've
always just given them the files one way; they know what to do with them.
____________________________________________________________
You are subscribed to the PEDA discussion forum
To Post messages:
mailto:[email protected]
Unsubscribe and Other Options:
http://techservinc.com/mailman/listinfo/peda_techservinc.com
Browse or Search Old Archives (2001-2004):
http://www.mail-archive.com/[email protected]
Browse or Search Current Archives (2004-Current):
http://www.mail-archive.com/[email protected]
