Mounting holes and nets

Making PCB Layouts, Manual routing, Auto-routing, Copper pouring, Updating from Schematic, Manufacturing Output
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Qrper
Posts: 21
Joined: 31 Jul 2015, 02:34

Mounting holes and nets

#1 Post by Qrper » 18 Aug 2017, 13:44

Gang,

Every pcb has mounting holes. I'd like mine to be connected to the ground net and have the holes plated through. Right now, I get hole with no plating and I can't connect them to any of my nets.

Is there a way to do this?

thanks!

Mike,

Tomg
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Re: Mounting holes and nets

#2 Post by Tomg » 18 Aug 2017, 14:29

Use a through-hole pad with a hole diameter large enough for the mounting screw threads (+ a little extra wiggle room) and a pad diameter large enough to accommodate the screw head/washer (+ a little extra to prevent head/washer overhang and to account for chassis mounting tolerances). For example, one of my through-hole pads for a standard 3 mm mounting screw has a hole size of 3.4 mm and a pad diameter of 8 mm. (Your mileage may vary.) Since it is a pad, it can be tied to a trace/pour/net. Later, if you think it will be necessary, you can add a circular pattern of Vias to each mounting hole pad (after placing them into the PCB layout) to give them more resistance to possible crushing/breaking of the plated surface inside the hole if the screw should ever be over-tightened.

p.s. Don't forget to account for the size of the chassis standoff to be used on the opposite side of the PCB.
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Tom

Qrper
Posts: 21
Joined: 31 Jul 2015, 02:34

Re: Mounting holes and nets

#3 Post by Qrper » 18 Aug 2017, 15:18

That's been what I've been doing. And for the most part, that works.

however, if I update the board from the schematic, then the through hole loose its net and properties revert back to the original size.

Right now, I wait to the very end to modify the through holes before making my gerber files

mike

Tomg
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Re: Mounting holes and nets

#4 Post by Tomg » 18 Aug 2017, 19:04

I should have mentioned that I attached my mounting screw pattern to a custom mounting screw component, placed the mounting screw component on the schematic, connected it to the desired Net and then brought it into the PCB layout. This keeps it properly connected during updates and repours. Here's an example...
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Tom

Qrper
Posts: 21
Joined: 31 Jul 2015, 02:34

Re: Mounting holes and nets

#5 Post by Qrper » 19 Aug 2017, 17:34

Great Idea!

Will make up some hardware mounting hole with a connection.

Mike

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KevinA
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Re: Mounting holes and nets

#6 Post by KevinA » 20 Aug 2017, 00:05

:cry: That must be the Tomg library! Mine doesn't look like that

Stin
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Joined: 05 Sep 2017, 08:57

Re: Mounting holes and nets

#7 Post by Stin » 05 Sep 2017, 09:02

Hi, friends!
Can you help me?
Can I have a DipTrace (version of 3.0.0.2) on the board to make a blind slot/hole for the square shape?
I tried through cuts in the board, but in 3d rendering, indicates that the square is through.
Also I attempted to do so by typing the additional signal layer "central" and indicated both (top and central) cut of the board. The result is similar to a through hole in a 3d preview.

Tomg
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Re: Mounting holes and nets

#8 Post by Tomg » 06 Sep 2017, 19:46

The closest I could get to what you are looking for was to create a slotted, rectangular, blind pad with an oval, plated hole. The Board Cutout feature does not have an option to limit it to only a few specific layers. If the layer-limited slotted-pad is not the right solution for your problem then you will need to contact your board vendor and ask them what kind of documentation they require to give your PCB a layer-limited rectangular opening.
Tom

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