Electronics > Manufacturing & Assembly

Local fiducials under package, it's ok?

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colotron:
Hello.
I was seeing a pcb design with a big module, and this board have 2 local fiducials, one of them below the module itself, and the other outside the module.
Is that a good practice?.
Could be useful to save board space and have more freedom to route the board.
What do you think about it?
Cheers.

Plecharts:
I don't think the fiducials make that big difference in laying out a PCB, so there is a different reason why they did it probably. Was the module right on the PCB, or was it spaced off using some headers and it had some ICs under it. If there was a BGA or something with small pin pitch, it could be to get better pick and place precision.
Please post some photos so we can see it.

colotron:
Of course, a view of the board is attached with some layers disabled to see better.
The board eagle source files are here.
In the attached image, the fiducials are circled in yellow.

Could be some difference - not too big I agree - in laying out small boards when the space is very constrained.

Thanks for your answer.

Jon Chandler:
Since the fiducials are used to align the board and pick&place machine, locating it under a chip should make no difference.

colotron:
Thanks for you answer Jon.
So far no dissent, it seems to be an acceptable practice.
Cheers.

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