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PCB assemblers require a file describing the component identifiers, the X and Y coordinates of the centre, and the rotation angle. I generate that file automatically from my CAD package (DesignSpark PCB). However the rotation angle that is generated is based on the footprint in the library. When the pick & place machine rotates the component based on the "rotation angle" specified, if it assumes a different footprint for angle=0°, then the component is going to end up the wrong way around.

Therefore, how can I be sure my CAD library and the pick & place database have the same assumption about the components orientations? I can only see one solution, which is to use the datasheet footprint figure (or pinout if not possible) as the initial orientation, but I would like confirmation and perhaps more details about how this works. Also, what happens then for passive components?

I looked around on the web and didn't find a standard, which is odd as in particular, both the designer and the assembler should agree on clockwise or anti-clockwise definition of the angle, even if I assume it is anticlockwise.

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    \$\begingroup\$ I suspect a big part of what you pay for set-up costs on an assembly job is for somebody to go through your design footprint-by-footprint and figure out what you meant by the rotation angle for each one. \$\endgroup\$
    – The Photon
    Commented Oct 12, 2015 at 17:13
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    \$\begingroup\$ blogs.mentor.com/tom-hausherr/blog/tag/ipc-standards \$\endgroup\$
    – Tut
    Commented Oct 12, 2015 at 19:12
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    \$\begingroup\$ You should look at how the part comes out of the reel. That is probably the 0-degree reference for the pick and place machine. In my experience, the first article always has some parts facing the wrong way, and they are corrected, and the correction is stored for that board setup. The first board run through the pick-and-place is not even soldered. I think they cover it with a tacky substance or something. The only purpose is to check all the rotations and placements. \$\endgroup\$
    – user57037
    Commented Oct 12, 2015 at 21:59
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    \$\begingroup\$ @mkeith: that's an excellent point, and since this is based on experience you should turn that into an answer. \$\endgroup\$
    – Mister Mystère
    Commented Oct 13, 2015 at 10:29
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    \$\begingroup\$ @tut: excellent article, thanks a lot. It actually lists the two candidate standards from the IPC and the IEC. I'll follow the IPC from now on (the PDF is free online) and tell the PCB houses, that ought to speed up the process. \$\endgroup\$
    – Mister Mystère
    Commented Oct 13, 2015 at 11:56

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So each part that has a JEDEC standard such as an SOIC8 has the rotation angle defined. Although most fab houses will verify stuff with you.

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