How to Choose a Footprint (solved)

I am having difficulty choosing the footprint of a component (diode for example), from the long list of available ones offered.
Is there a more detailed explanation of how to choose and select a particular footprint from the ones offered?
I am reading this tutorial:

Jim.

The answer is blowin’ in the …diode’s datasheet

To put what @straubm said in another way: you need to pick a specific diode that you will order and place on your board* and then the choice of footprint becomes whatever is the appropriate footprint for that specific diode. The schematic symbol for a diode doesn’t correspond to any specific part that you might install, so there are many possible footprints.

*technically, there may be many possible specific diodes that fit the same footprint. The details of how to select an appropriate family of diodes will depend on your actual circuit’s needs, and other constraints such as mechanical space available, thermal issues, etc.

3 Likes

Good answers, thanks for the prompt reply.
Back to the drawing board…

Jim.

If you wish (your choice) you can skip the step of selecting footprints for symbols at schematic (I have never went through this step).
I am using only symbols from my own libraries. Each symbol has associated with it footprint also from my own library. Symbols I draw myself, footprints I copy from KiCad library to my library and verify with datasheet of my element.
Having only my libraries at library list guarantees that I will not use any symbol without footprint associated with it. So when I have schematic I go strait to PCB.

2 Likes

Not really.
You can hardly expect beginners in PCB design to start with creating and maintaining some libraries before they make their first PCB. The flexibility in Kicad where any schematic symbol can be combined with any PCB footprint makes it quite easy to start building some experience. It’s only that after you’ve done a handful of designs that the idea of having personal libraries, with footprints already attached, and maybe even part numbers and ordering info becomes attractive.

Apparently Jim_Thompson is unfamiliar with footprint naming and conventions, and having such a library does not help if for example diode or resistor symbols are linked to the wrong size footprints.

1 Like

Yes, this is correct, I am as yet unfamiliar with footprint naming and conventions.
I will read more about this before asking any more questions.
Thanks for coming back to my assistance Paul. (After our first exchange over a previous thread!).
I trust that the quality of my questions are perceived as “improved” according to your assessment?

Thanks for the reply Piotr.
I have only a vague impression of what you describe above, but have no idea (yet) how these instructions would or could be implemented.
But…I will go back to the manual for a closer read on this.

Jim.

It’s all right.
A small hint for the next time:

A title like:

is not very encouraging to read a thread. It’s much better to have a title that actually describes the problem, for example something like:

How to choose a footprint?

Ok. Point taken.
I have edited the title of this thread and will choose better one next time.

Jim.

Many thanks again Paul.

I don’t know if manuals you find now are closer to V6 or still more about V5. Reading them you have to have in mind that something can work differently then manual says just because KiCad is faster being developed then documented.
For me good way of learning KiCad is to make my own list of all menu positions (of all applications) with my own description of what each function does.
KiCad (in my opinion) is destined to be used with one hand at mouse and second at keyboard - using hot-keys allow you work fast. So I have also made cheat sheet of Hot-keys organised by state of design when each hotkey is expected to be used and ordered by expected frequency of use.

Thanks for the reply Piotr.
Can you please explain further how this is done?
“Menu positions”?

If I have to get familiar with a new software I open each menu and read through the menu item lists. I try to think what it means. I open some dialogs (three dots in the end means it opens a dialog). I also hover over icons and see if they show tooltips.

And I find it difficult to understand why other people don’t do the same. It’s so easy, and gives a good overview of what the program can do.

If the program has a drawing area or something similar (like KiCad does), I try to create items there and open the context menu to see what I can do with the objects.

I have learned KiCad mostly that way. I quickly went partly through the Getting Started tutorial (which was then for v4) but most of the rest I have learned by researching the GUI and experimenting.

May be I used wrong wording (thinking in Polish, writing in English). I had in mind ‘menu items’.
Practically I do a spreadsheet like:

But now I have it for V5 and in Polish so no idea to copy that file here.
See how many tabs there are.

The main advantage is that after doing something like that I am almost sure that there are no software possibilities I don’t know about their existence at all. Practically I don’t need to look into that file later so someone can said I lost time doing it, but for me doing it is the good way of learning KiCad.
But if something I am doing rarely and it is not easy task my file allows me to not learn it from beginning once more (I am 60+ and I just don’t remember how I have solved a problem an year ago if I have done it only once). The FC-3D tab in my file is one that I get back to it several times. I described there step by step several methods to make 3D model using FreeCAD what is not easy for me as I have never used any 3D CAD program before. In FreeCAD I had a problems with disappearing colors. For example try to make one pin of terminal block (having metal inside and green plastic outside). Exported to KiCad have its colors preserved. Now try to generate 2,3,4,5,…10 pin terminal blocks trying to make array of your one pin.

This topic was automatically closed 90 days after the last reply. New replies are no longer allowed.