I was wondering what does FIDU mean in the schematic below and what is it used for ?
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3\$\begingroup\$ "Fiducial" probably \$\endgroup\$– Criticize SE actions means banCommented Sep 23, 2020 at 14:24
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4 Answers
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In your image, FIDU is the symbol's name for fiducial. Fiducials are used by optical equipment (a pick and place machine) to visually see and locate the board's origin relative to the machine's origin. A small fiducial is probably a 1 mm diameter footprint. Typically, I would place 3 on the top-side of the PCB near the corners and 3 for the bottom-side. I suppose that's why there are 6 shown in your image. Sometimes, additional fiducials are added in close proximity to a large chip/ASIC to help perfectly place (minimize placement tolerances) the chip onto the PCB during PCB assembly.
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"Fidu" is short for fiducial marker.
They are used on printed circuit boards (PCB) to assist in lining up the various layers.
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1\$\begingroup\$ Either for lining up the various layers, or for positional calibration for component placement machines. \$\endgroup\$– user16324Commented Sep 23, 2020 at 14:29
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\$\begingroup\$ Are they really necessary ? I have never used them in the past. \$\endgroup\$– Amen0Commented Sep 23, 2020 at 14:33
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\$\begingroup\$ Your PCB fabricator or assembly house will tell you if they are needed. I know what fiducials are, but I've never had to use them. \$\endgroup\$– JRECommented Sep 23, 2020 at 14:40
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1\$\begingroup\$ At the place I work, we have to use them because the supplier of the boards wants them. Personally though, I’ve ordered boards from JLCPCB for small side projects, and have never included them. If you send without, they’ll tell you if you need them or not. It’s probably a bigger deal if they are loading the parts onto the board for you. \$\endgroup\$ Commented Sep 23, 2020 at 14:44
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\$\begingroup\$ It is clear for me now. Thank you guys your help. \$\endgroup\$– Amen0Commented Sep 23, 2020 at 14:52
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If that is what I think it is, it is a Fiducial. They are used for the board manufacturer as a reference so that they know where everything is located on the board coordinate-wise.
If you want to learn more about them, there is plenty of information online if you look up ‘Fiducial’.
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I would guess it refers to Fiducial Marks, measuring points on PCBs for positioning.
