Hi,

can anyone explain to me, what the purpose of these dots is? It is a mounting hole, and a screw will sit on them.

Cheers,

Toby

 

Probably on the GND plane and the dots transfer the continuity from board to chassis via the screw?

 

Probably on the GND plane and the dots transfer the continuity from board to chassis via the screw?

But there is already a coppersurface on the other side, connected to the vias to the right. Why is there then not just a free coppersurface too?

 

So they rise above the solder mask to make contact.

 

You would have to contact the board manuf?
Or could have been done at the board layout time

 

Hi,
Does the unassembled PCB have a lacquer spray finish?
E

 

But there is already a coppersurface on the other side, connected to the vias to the right. Why is there then not just a free coppersurface too?

Could be a few reasons, the raised spots reduce the chance of the screw doing any damage when tightened, also, and especially if the screws have serrations under the head, it enhances grip of the screw.

 

Hi,
Does the unassembled PCB have a lacquer spray finish?
E

Yes.

 

The board manuf would have the answer, any thing else is pure speculation!

 

The board manuf would have the answer, any thing else is pure speculation!

This is quite a common design ,so it should be know by some people.

 

This is quite a common design ,so it should be know by some people.

I would say the suggestions you have had so far pretty much covers it?

https://electronics.stackexchange.com/questions/313397/should-mounting-holes-have-solder-bumps
https://www.eevblog.com/forum/chat/solder-dots-around-mounting-hole-what-are-they-for/

 

I put "VIAs" around the hole for the bolt. It looks something like what you showed. See picture below.
I found that sometimes the bolt strips out the feedthrough and disconnects the top pad from the bottom pad. Also disconnects the internal layers.