Copper Fill Area Not Working

I am having some trouble getting a filled zone to work. I read in a separate discussion here (cant like as new users can only put 2 links) that I might try putting a trace so the layer will fill, with no luck.

I have checked to make sure they are on the same net list.

Maybe someone has a better idea to accomplish what I am trying to do. What I want is to have a 4mm diameter via connected to a copper “island” for thermal purposes (FET package). Is it a problem with the fill area settings not allowing such a small island? I did some quick tests in the +12V net list and it worked fine, but drawing a similar sized fill area in my Thermal Net still doesn’t fill any copper?

As this is my first time using KiCAD I did do something suspicious, in order to get a new netlist in the Layout i did the following in my schematic.

Is there a better way to go about this? I was unable to find in the data sheet which pin, if any, the body of the FET is attached to. FQP30N06L MOSFET (cant link again only 2 links for new users)

See How to create a power plane (using zones).

Thanks for the reply @eelik . That was helpful, I assume my problem was the VIA i had only fills if its connected to a pad. (read from your post) I ended up doing more research and realized the body of a MOSFET package is almost always connected (electrically) to the GATE. Drew a race to the correct pad (middle) and my copper is all filled in.

Are they? That surprises me, as this would increase the gate capacitance, and also the gate has no need of increased current capacity. I would have thought NC (in the case of your device), or source or drain.

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Is it?
As far as I know, it is connected to DRAIN

is a power FET in TO220.

As far as I know the Tab of a TO220 is always connected to pin 2 (which usually seems to be the Drain for MOS Fet’s)

There are Footprints for TO-220’s in KiCad, for example:

Package_TO_SOT_THT / TO-220-3-Horizontal_TabDown

The mounting hole is listed as a Non Plated Through mechanical pad with a 3.5mm hole:

If you want to create an exposed copper area with a zone, then the zone must be connected to the net you want to connect it to. (Oops, apparently handled).
Do you have other zones which are drawn filled?
Zones are not always filled in Pcbnew.
You may also have to gecalculate zone boudaries with ‘b’.

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