fiducial shape ....question

[successmani]

I would like to know the reason for using circular disks or solid disks and donut shape fiducials as the most commonly used fiducials.What is the problem in using other fiducial shapes like diamond or square and many more.

[Tom]

Very good question. The main reason why Square and Diamond shapes are not used for fiducials is because PCB manufacturers use these shapes for outer layer Copper Thieving. They do not use Circle or Donut Shapes for Copper Thieving. No other reason, that's it.