QFN centre pad won't connect to GND

Making PCB Layouts, Manual routing, Auto-routing, Copper pouring, Updating from Schematic, Manufacturing Output
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fastbike
Posts: 61
Joined: 06 Mar 2021, 06:42

QFN centre pad won't connect to GND

#1 Post by fastbike » 31 May 2021, 18:59

I have a schematic with a 49 (48 pin + pad) QFN component.

This schematic has the pad connected to the GND net.

In the PCB layout I have added a via that connects from the top layer (placed in the pad) through to the GND layer (layer 3 of a 4 layer board).

The copper pour on layer 3 shows an isolation ring around the via. If I place the same type of via on any other pin it connects fine.

What am I missing ? How do get the pad connected to GND ?
Ardent hobbyist

Alex
Technical Support
Posts: 3897
Joined: 13 Jun 2010, 23:43

Re: QFN centre pad won't connect to GND

#2 Post by Alex » 31 May 2021, 21:10

I guess you just dropped the via on center pad of QFN component. If so, the via is not connected to GND net even though it has physical contact with GND pad. Please place ratline from the via to any GND pad then update copper pour on GND layer.

fastbike
Posts: 61
Joined: 06 Mar 2021, 06:42

Re: QFN centre pad won't connect to GND

#3 Post by fastbike » 29 May 2023, 06:52

Hmmm. I never thanked you for this answer, from my question back in the day when circuit design and PCB layout was quite new to me. So thanks from my current self for such a wonderful product and making it better all the time.
I also found I can right click a via and select "Add to net" and from there connect it to the GND net.
Ardent hobbyist

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