Hi All,
   So to pad or not to pad, that's not really my question, but it's close. Over the many years I've been designing boards, I have always put a copper ring/pad/solid copper area around mounting holes. If you are going to put a screw and washer in the hole, I want to have something more than FR4 under the hardware. So now we have a situation where the mounting holes are so close to the edge of the board, if I put a copper ring large enough to ensure the hardware is on it, my pad is hanging over the edge of the board or within .010" of it. If our normal copper cut back from the edge is .050" or more, I won't have a ring any longer, but more of a "C" shape ring. That says that most of the washer/hardware is on the copper and the remaining part is on the FR4. I don't have a photo of this, but I think you get the picture... Anyone have any comments about this type of arraignment? I told the mechanical engineers that they need to move the holes inboard more to allow the full ring of copper, but in the current case, that's not an option. Going forward I would like to ensure the ring is at the .050" away, but to ME's that's space wasted and the holes don't have to be that far in... Ironically, the ME says we need to make sure we have a .050" cutback for copper from the board edge, (Yes, I know that, I like .075" or .100" even.) but yet, he's creating a situation where I can't have a full ring.

    Am I still in the dark ages and insisting copper be under all of the hardware or does it matter it's only partly covering? Any data to support having a full ring or not having a full ring?

Thanks in advance...


Scott Decker - Staff Engineer, PCB Design Services CID+ - Electronic Systems Center
UTC AEROSPACE SYSTEMS
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