PCB footprint...origin in cetnre, or pin one?

[cupoftea]

Where's the best place to put the origin on a PCB footprint....geometric centre, or pin 1?

And with the 2173157-3 (TE connectivity) Micro USB connector, where would you put the origin? (since neither pin 1 is defined, and the location of the “centre” depends on your “Point of view”.
Also, the pads are extremely close together, so any pick and place error will result in shorting.......

2173157-3 (TE connectivity) Micro USB connector

https://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Customer+Drawing%7F2173157%7FA1%7Fpdf%7FEnglish%7FENG_CD_2173157_A1_2173157-C_revA1.pdf%7F2173157-3

 

[HasHx]

Hi,

I always use center of symbol as my origin, with uneven parts i pick the center of the pads, if the pads were uneven as well i would go with pin #1

do not worry about manufacturing and shorting etc.. the manufacturing engineers will fix anything if needed.

regards,
Hashem

 

[andre_luis]

One thing is the reference for drawing in the layout design, another thing is the reference center defined for the pick-and-place process, which as Hashem mentioned above will be adjusted by the assembler company, based on, among with other factors, the center of mass of the device, the gripping mechanism, and the proximity to the smaller pads, for example. As a rule, the choice of the center reduces the maximum error of the process, distributing the error evenly at each extreme of the whole geometry.

If you chose the 1st pad for example, this one would have a null error and the last one could be with an error of, let's say 'E'. By choosing the center of both first and last pads, you would be assigning an expected error of +E/2 and -E/2 to the pads at each end.

 

[Mattylad]

Always use the centre.
This allows best rotation and pick and place file output.
If you use pin1 then the assembly dept will have to first figure out which is pin 1 then adjust the origin to the centre for the placement machine.