On a single-layer board with no through-hole and no machine placed components, is there any need for fiducials (for example to route the board outline)? Board house has asked for permission to add fiducials to gerbers. Of course I will say yes, but I am surprised. I definitely don't need the fiducials for assembly. But the vendor seems to be saying that the fiducials will assist in cutting the board outline.
According to this application note from norcott, three global fiducials are used to determine the correct orientation of the board (or panel).
It is important that only three fiducials are used. This ensures that if a panel is accidently inserted into the placement equipment rotated through 180°, the equipment can detect it and halt assembly.
And for a single board without a panel, those fiducials are placed on the board, and will show up in the end:
(images taken from the application note)
There is no specific mention of routing the board outline in that document, but I can imagine that they use this also in the routing machine to make sure that the board has the right orientation.
Fiducials are required when you use any kind of computer vision. The fiducials are the calibration point for the vision system and the board coordinates.
You need them for vision assisted drilling, pick and place, but also Automated Optical Inspection (AOI).
Basically any machine that automatically recognizes the board position and angle.
You don't know their process, and just how many things they have automated, requiring machine vision, for processing and maintaining the quality of their boards.
Perhaps the most important thing is that they want to process your boards through their standard flow. If your board is a 'special', so it doesn't need this station, and it can't be put through that station, then it has to be handled differently, and it will cost them 10x more.
If their outline router uses fiducials, they will want to add them.
Fiducials are also used to line up stencils for applying solder paste.