Platform forum

Mounting Hole

JohnsonMiller , 08-29-2016, 10:55 AM

I have seen two type of mounting hole, a) simple 3mm hole, b) six via around a 3mm hole; type b looks strange for me, is there any technical reason for those vias?
second related question, where we should connect these mounting holes, board GND? In some design those MHs are connected to GND via high voltage capacitors! any explanations?

mairomaster , 08-29-2016, 11:53 AM
Via stitching around (into) pads can be used to increase the current capacity between the layers (if it is a power pad) or to increase the mechanical strength of the pad - the vias literary stitch the two pads on top and bottom layers together.
robertferanec , 08-30-2016, 06:16 PM
- I assume, the VIAs in mounting holes make better connection. You can often see them on Motherboards.

- Where to connect mounting holes? That is EMC question I normally connect them to GND, but this depends on the type of board you are designing, what kind of enclosure you have and how it is going to be mounted in your system. Capacitors will prevent DC voltage flow e.g. if you have two boards connected together via an interface and they are grounded far away of each other (e.g. plugged in to MAINs in different rooms), but still makes a connection for high frequency signals e.g. in some cases it can help to filter noise or still be able handle some ESD discharge.
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