At 12:22 PM 8/26/2003, Brad Velander wrote:
Tim, Igor and others,
I did a little experimenting last night on this issue and confirmed my suspicions. The mid P&P point is calculated from the center of all pads locations.
I made up several parts that had identical pad locations, then I added other details like silkscreen, copper fills, copper tracks, text and other lines. The mid location never changed as long as I didn't change the pad locations. Changing pad locations by 10 mils resulted in the expected 5 mil shift in the mid P&P point.

That still leaves two possibilities.


(1) Location is calculated by finding extents of pad centers and taking the midpoint of the X extent and the Y extent.

(2) Location is calculated by finding extents of *pads* and taking the midpoint of the extents.

If all the pads are the same size and shape, including rotation, there would be no difference between the two. I do not know if pad shape and rotation affect component centroid. They would certainly affect extents *if* extents were calculated as true copper extent.

I don't recall which it is. If I had to make a choice, I'd go for pad centers.

Abd ul-Rahman Lomax
LOMAX DESIGN ASSOCIATES
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Protel EDA license resales
Easthampton, Massachusetts, USA
(413) 527-3881, efax (419) 730-4777
[EMAIL PROTECTED]

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