Assign a pin to a thermal pad?

Layout Footprints
1

Hi

I have a few MOSFET where their thermal pads (drain) have to be connected to the cupper layer.
The package is a TO-220AB.

Do I have to create a new footprint and add a new pad for the thermal pad?
In that case, I would have 4 pads?

Thanks for your help.

2

Sadly such a footprint is missing in the official lib. (We only have TO-220 footprints for packages without a Tap.)

Depends on your mosfet.
If the Tap is connected to one of the other 3 pins you can just give this pad the same pin number as the pin it is connected to.
Otherwise you need to give it a separate pin number

Have a look at TO_SOT_Packages_SMD:TO-252-3_TabPin2 for inspiration. (Yes this is a SMD package but it shows the principle of how it can be done.)

3

Do either of these atch footprints help you?

There is some discussion about how to create them at Pad Holes Under SMT for Heat Sinking and other questions and at How to add via holes on a thermal pad of QFN footprint? .

Dale

TO-220_Horiz_ThermalPad.kicad_mod (6.5 KB)

TO-220_Horiz_ThermalPad_Alt.kicad_mod (8.8 KB)

1 Like
4

Thanks for your replies.
I am using some IRFB4110. Pin2 and thermal pad are connected. So the LM7805 (TO-220_Horiz_ThermalPad.kicad_mod) is pretty similar and I will go for it :slight_smile:

I like the fact that we can import _mod files into FreeCAD with the kicad StepUp tools. The representation in 3D is better with the different layers. However, the Pads numbers are not imported; probably complicated to achieve and not so important finally!