I have a board sitting here that I worked on in 1991 (386SX PC motherboard)
which has mounting holes like this, but I haven't seen it done much lately.
Basically it has a mounting hole that has the 0.156" screw hole surrounded
by 8 smaller holes in the middle of 0.375 square block of copper that
doesn't have a solder mask. Looking closer at this board the screw hole is
not plated, so my presumption is that the plated through hole was torn up
by the mounting screws in production and thus it was made non-plated and
the grounding holes under the screw head added.  I have seen this type of
mounting hole used on other designs and I have seen this where a large bus
wire was attached to a PCB.


I assume the DRC violations are for clearance issues since it doesn't like
putting a pad or via on a pad?

The easiest way I can see to do this is to put the mounting hole in the
middle of a top and a bottom polygon or fill the size of the total screw
head area you want (0.225"). Set the pad size relatively small since the
fill will give you the copper area.Now place vias at the additional hole
locations and make them the same net. Next add a design rule saying these
vias can be close to the pad, and add a fill on the top and bottom solder
mask.


Rob



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