Fuse 1812 footprint wrong?

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Hi,
talking about standard fp library item Fuse:Fuse_1812_4532Metric. I find at least three sources, that 1812 fuse footprint should look like 3.45mm - 1.78mm x 3.50mm:

0435I
0435I728×267 48.4 KB

F_1812 sources:

But Kicad library has ~ 3.16mm - 1.125mm x 3.4mm:

1718J
1718J1441×580 34.8 KB

  1. Is this a mistake in the library? Or is this kind of IPC standard? The problem is sucha, that real 1812 fuse would fit on kicad’s 1812 footprint perfectly, but wider pads should help to spread heat away from the chip…

  2. Should I report this to library team (Issues · KiCad Libraries · GitLab)?

  3. I wish to contribute to the library creation, but was not able to generate a thing 2 years ago when tried using KiCad / KiCad Libraries / KiCad Packages3D Generator · GitLab. I am running windows. Have anybody used (setup and running) this scripting thingy on windows machine recently? Maybe this scripting setup works only on several PC’s, belonging to library keepers, running old OS, or something like that…? My skills are better now, but still, afraid to setup everything again with no success. (I don’t like maintaining pretty generic footprints like this fuse or Diode_SMD:D_SOD-128 just because they do not come with 3D models, I would like to provide these models to the stock library, instead).

2

You can add a 4th. Little fuse also uses the bigger footprint.
https://www.littelfuse.com/media?resourcetype=datasheets&itemid=3f8eb65a-bef8-47bb-aca2-1f80238bfbf2&filename=littelfuse-ptc-1812l-datasheet

And a fifth: “Fuse Tech”
http://www.fuse-tech.com/uploads/pdf/ASMD1812SL.pdf

Which is not what you want in this case.
Those PPTC’s are designed to trip at a certain temperature, and their trip point shifts if the “heatsink” size changes.

I’m guessing that a GND plane directly under it on a 4 layer PCB (thin prepreg) also has a significant influence on their tripping point.

But they are also not very accurate parts to start with.
I don’t know about the IPC, but I’m tempted to give priority to the fuse manufacturers data because of this trip point shift effect.

3

Bourns with two “1812” package variants
https://my.element14.com/bourns/mf-msmf110-24x-2/fuse-ptc-1-1a-24v-1812/dp/2291869

4

So, probably 2nd 1812 variant with 1.78x3.5 mm pads should be proposed to the library, klc allows this, if understood correctly.

Any comments about question point no. 3?

5

But thuis can be changed by drawing your own footprints. When you come across such errors, you correct them by drawing the correct footprint. It is not a must to use the symbols available in the global library but also you can do your own symbols for your project.

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