kicad-lib-committers team mailing list archive

[Michał Sałaban <michal@xxxxxxxxxxxx>]

Hi,

First of all, sorry for opening a new thread but I've just subscribed
and have no idea how to reply to an email I hadn't received.

A couple of days ago I submitted two changes to the library and footprints:

a) Added some MOSFETs with the mounting tab present in the form of fourth pin:
https://github.com/KiCad/kicad-library/pull/76

b) Added TO-220 horizontal footprint with a pad and mounting hole for
the tab, both marked as pin 4:
https://github.com/KiCad/Transistors_TO-220.pretty/pull/1

There were several reasons to choose such approach for my proposal.
I've considered the following things:

1. The designer will have freedom of choice whether to connect the tab
electrically or not, as it is represented by a separate pin (in case
of these MOSFETs it is drain, labelled D_tab).
2. In case the tab is connected to anything else than the middle pin,
the footprint is still useful. (Sincerely, I don't know if any
component like that exists.)
2. The pad in the footprint may serve as either connection or
clearance on both copper layers.

I hope this approach doesn't break anything. I might, however, be too
complex solution to a simple thing, especially if tab is never
connected to anything else than pin 2. The only issue I've noticed so
far is that using my 4-pin MOSFET components with a 3-pin footprint
(any vertical one, for example) makes Pcbnew complain about missing
pins.

Regards,

-- 
Michał Sałaban