"Mechanical" fabrication property for SMD pads

[Heath_Raftery]

I’ve been using JST’s PH series connectors, which now come in surface-mount variants. They have a couple of surface mount mounting pins for mechanical strength that are unconnected electrically.

In the past I’ve just rushed it, used the symbols from the Connector_Generic_MountingPin library, and just marked the mounting pin as unconnected in the schematic. This works fine, but gives the wrong idea - I’m never going to use this pin electrically, and having them appear in my schematics only to mark them unconnected is undesirable.

I’d like to keep the pads, but not have them appear in the schematic. It turns out the new(ish) “mechanical” fabrication property allows this… nearly.

The first issue is, this property is not designed for SMD pads, and you’ll be warned as such when applying the property:

The next issue is that you’ll be further chastised for the questionable choice in the DRC:

J1 is associated with the MountingPin symbol. J2 is associated with the Generic symbol. Both have the “mechanical” property set on both MP pads.

Other than those issues, I think this does just what I want - there’s no MP pin in the schematic, I’m not required to connect them together in the PCB, and there’s no “unconnected net” error in the DRC.

Should I heed these warnings, or is this safe to use and the warnings can be removed?

[RRPollack]

I would create/modify the symbol so the pin has the electrical connection type “Unconnected”. That solves your concern about having to mark them as unconnected in the schematic.

I’d define footprint pad just as any other SMD pad and not mess with the fabrication properties.

[teletypeguy]

@Heath_Raftery

I’d like to keep the pads, but not have them appear in the schematic

or, optionally, embrace them in the schematic and connect them to esd-ground which should be running around the edge of the board exactly where they appear.

[Heath_Raftery]

@RRPollack

I would create/modify the symbol so the pin has the electrical connection type “Unconnected”

Oh good idea. You can then make them invisible. But does that also prevent the expectation that they’re connected to each other even though they have the same name?

Still, seems a bit round-a-bout to create and assign a symbol for the purpose of defining a pin that is then not used or visible. Specifying it is “mechanical” and therefore irrelevant to the schematic is a little more intuitive to me, but not a huge deal.

@teletypeguy

embrace them in the schematic and connect them to esd-ground

I’d still like the option to do that, just not the requirement.