Having clearance DRC errors with custom pads?

[dbur]

I've had difficulties resolving design rule errors on parts with custom pads.  What I finally figured out through a process of trial and error is that when you create a custom pad a default clearance is added to the geometry.  When you place the pad in your footprint editor, that clearance is not carried forward, and you think can set the clearances on the pad in the footprint editor as expected.

This all seems to work fine and you can place the part in your design and turn on clearances and see just what you expect.

But when you run a DRC you get clearance errors that are not shown in the view clearances option.

Turns out the custom geometry default clearances are still in there even though you cannot see them.  The only way to resolve this is to go back and edit your custom pad and set the clearances to 0 or some value smaller than you will ever use.  Then when you set the pad clearances in the footprint editor or in your design you will see what you expect and the DRC's will also work as expected.

I would consider this a fault of the application.  What NI should do is:

1. set default custom pad geometry clearances to 0 (or just don't have any clearances on the geometries.

2. or at least show the custom pad clearances when view clearances is turn on.  That would have saved me a lot of time.

You're welcome.

[stressed_user]

Hi dbur,

Thanks for sharing this research/information. I make custom pads quite often but never encountered this problem.
I recently had a shortcircuit in a customers PCB that was not detected by the DRC.

In the jpg below you can see a short over C51 (on the left of C51, in the blue circle).

The reason was this, the customer added a copper area in this zone with a 0.35 mm clearance but with a 0.000001 mm (= 1 nanometer) width.
The problem was solved when I increased the width to 0.1 mm (picture below).

I hope this information is usefull to you and others in this forum...

Stressed User...