How to place components on the underside of the PCB - Special case

Hello, I’m new to the forum.

I want to place some TO-3P and TO-126 power devices on the bottom side of the PCB but not flipped - so the device Heatsink tab will still face downwards. The device legs will be bent upwards and inserted from the bottom side of the board. Is there a way to do this in KiCAD?

Thank you

I would make a new footprint for this that represents the part mounted with the tab away from the board, then flip it to the bottom side. There are actually already footprints in the KiCad library for this: see Package_TO_SOT_THT:TO-3P-3_Horizontal_TabUp and Package_TO_SOT_THT:TO-126-3_Horizontal_TabUp.

Here’s a screenshot of the 3D model of the TO-220 version to illustrate (the TO-126 didn’t have a 3D model):

Fantastic! Thank you

The clean way is to create a modified footprint with reverse pin order. I would mark such footprint very clearly with a special name in the library and with informative text in some layer so that it wouldn’t be used in a wrong way accidentally.

If you want to, nothing prevents you ignoring correct pin numbering and just wiring it according to their functions, as long as the end product works correctly. You can also play Russian roulette.

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There really is no need for all of this:

… and this:

As gkeeth already mentioned. KiCad already has a Tab UP and a Tab Down version of the TO220 footprint. So just use the bog standard Tab UP version, and then flip it to the bottom of the PCB. No need to modify anything at all. Except, maybe:…

When mounting multiple TO220 packages on a heatsink, my preference is to not use the normal mounting hole at all. Just put the TO220 packages in a neat row with around 3.5mm in between them, put a 3.5mm hole through the PCB and put an M3 Screw in between the packages. This makes the PCB itself an integral part of the heatsink construction, and you don’t need thin isolation discs for the screws.

This is what I’ve done and how I normally design my PCB’s.