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Often the footprint I need is not in the existing libraries and I need to make my own. For example one of the dozens of micro USB footprints.

When I make a footprint and then send for assembly at JLCPCB for example the center point I have chosen often does not match what they expect and they give the error "The pad centroid is different from component centroid".

It is easy when the datasheet shows the center, or when the part has obvious symmetry on both axes. But with the example of the USB connector there is no obvious vertical center point and no center is specified in the datasheet.

If I get this center point wrong the part will be rejected or not placed correctly.

What is the correct way to determine the center point of a part?

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  • \$\begingroup\$ Weird. I've never ever needed to worry about this in OrCAD when I had boards assembled. Why would you need to know the pad centroid? I don't even have to worry about the the component centroid. I seem to be able to select whether the (0,0) is on pin 1 or the center of the footprint but I normally just choose center. Does the JLCPCB service you are using have a human look at the board and setup the machine? Or is it a super automated budget service? \$\endgroup\$
    – DKNguyen
    Commented Aug 19, 2021 at 4:59
  • \$\begingroup\$ @DKNguyen It is very budget, and very turnkey. I pay $8 for setup and am expected to have done most of the leg work myself. They do board batches as low as 5 and will assemble as few as 2. \$\endgroup\$
    – HighInBC
    Commented Aug 19, 2021 at 5:07
  • \$\begingroup\$ Do they do BGAs? Like all I really need are BGAs and the ocassional QFN or IC with a bottom mount pad when I don't want to make a big hole under the IC \$\endgroup\$
    – DKNguyen
    Commented Aug 19, 2021 at 5:08
  • \$\begingroup\$ Yes. I don't want to go into too many details as I would hate to sound promotional but they do BGAs. \$\endgroup\$
    – HighInBC
    Commented Aug 19, 2021 at 5:10
  • \$\begingroup\$ Update, it appears that they did correct the placement of the part. I do however still want my footprint corrected, and also to make future footprints correctly aligned. \$\endgroup\$
    – HighInBC
    Commented Aug 19, 2021 at 5:57

1 Answer 1

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Different board houses (probably) have different rules, the rules for one as an example are here.

So, that's the first thing to know. Then when creating the footprint have the origin be in the right spot (according to the 'rules').

When exporting the 'Pick/Place Data...' in Orcad you can select 'Symbol origin', 'Body center' or 'Pin 1'.

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