Then comes the really tricky part. For parts on the bottom side, the general rule (not in the IPC standard) is to either view the parts from the bottom with the board mirrored about the Y axis with the same pin one orientation (upper left in the mirrored image) and rotation counter-clockwise, or to view the bottom from the top with rotation clockwise ( with the footprint mirrored about the Y axis so pin one is on the right, in the upper right corner or top) giving the same results.
All X,Y positions are with respect to the centroid of the part.I would expect the software can do all of this, but you need to layout your footprint with this in mind. In Free PCB, they use a centroid vector to specify the location of the centroid of the part and the angle of the zero degree rotational position. Not sure how this is done in gEDA.
As you say, you can deviate from this and the board house will likely still give you correct boards as long as you are consistent. But even though the parts on my board were clearly labeled with pin 1, a board house assembled all of my prototypes with the chips reversed once. Now I am much more cautious about the XYRS file, almost paranoid... 8-S
Rick At 10:42 AM 9/27/2010, you wrote:
Just 10 minutes ago I had my 1st talk with my first assembly house. Guess what! I'm asked to provide rotation data. In the other mail I'm currently editing, I'm trying to provide definitions on where X- and Y-axis is on a part, including where X+ is on mechanically doubly symmetrical polar parts etc. As of now, I'll probably have to check/provide every angle by hand, but for future footprints, the definitions have to be absolutely clear. If there are contradictory standards, we will have to opt for one. As Rick said, they are able to adapt to any coordinate system, but at least the designer must know, what he means himself ;-) Regards, Armin Rick Collins wrote:I am curious about the reasoning for picking values of design rules.I have not found the assembly houses to be very useful for this sort of info. They seem to be willing to work with whatever they are sent and will only give feedback when something causes real trouble for them._______________________________________________ geda-user mailing list geda-user@xxxxxxxxxxxxxx http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
_______________________________________________ geda-user mailing list geda-user@xxxxxxxxxxxxxx http://www.seul.org/cgi-bin/mailman/listinfo/geda-user