From @dbrgn on Wed Apr 04 2018 19:49:13 GMT+0000 (UTC)
We should try to come up with consistent, practical and beautiful-looking recommendations for designing libraries. This should include all things like package design, signal naming and category naming.
First question: When designing footprints, e.g. for an SOT-23-5:
…should we (1) include the outline of the plastic case in the footprint?
According to @ubruhin, “the solder mask is automatically subtracted from silkscreen to avoid silkscreen on copper”, so this would work.
Or should we (2) make the rectangle smaller to avoid the pads?
Or should we (3) work with lines?
I tend to favor (1) because it looks best in my eyes, as long as silkscreen - copper is not a problem.
On a sidenote, I’m not sure if a single RFC issue is a good place to discuss these questions. Maybe we should open a separate repo / issue tracker where every question can be discussed in a separate issue, similar to https://github.com/rust-lang-nursery/fmt-rfcs/issues?
I like #1 myself for sure. It doesn’t make sense not to match the real outline.
Other questions:
Where should the text “U1, R3, etc” and the value go by default, and what font and size is used?
What kind of polarity mark should be used? Dot, notch, or both? (I like both).
What marking should indicate pin 1 of a connector?
For batteries and capacitors in the schematic symbol, do we want an explicit plus sign, or is the long and short line notation enough?(I’m a fan of explicit).
Should IC pins on the schematic match the layout of the actual chip, or ba arranged logically?(I like a chip-based arrangements, but logical seems more popular).
After some discussions with @ubruhin I think that it would be best to follow the IPC standard as much as possible when designing footprints. First, your questions:
I’d stick with IPC and extend a line along pin 1, like this:
In contrast to a notch on the silkscreen, it has the advantage that it’s still visible after assembly.
Note that only the top and bottom line are silkscreen, the center rectangle is on the documentation layer. The documentation layer should include the projection of the actual package, see the package conventions for reference.
Regarding a notch, if there is one on the physical package, I’d put it on the documentation layer.
That’s a good question that could be discussed in a separate thread. I definitely wouldn’t put plus signs next to SMD capacitors, but probably next to battery connectors.
This is part of the symbol conventions, where we have decided to go with logical for now.
If you want to discuss any of those decisions or open issues (even the ones already in the docs), feel free to open a separate issue per discussion item so we can find a consensus there We’re still trying to figure out what works best.
And make sure to take a look at the current library conventions section in the docs.
well maybe then our windows librepcb is broken . just downloaded this a week ago to give it a try. the library is installed but there are no sot components.
I will download libre for linux and try again. thanks!
Maybe we are not talking about the same thing. The mentioned package is in the base library, and I’m pretty sure it is there also on Windows But that’s only a package, not a device so you will not find that thing in the schematic editor. You first need to create a device which uses that package (that’s a very simply process which you can do in your local library, see docs). As an example, in the Texas Instruments library there’s a device LP5907-Q1 which uses the package SOT95P280X145-5.
Thanks, But I am not sure I want to create anything from scratch here. There are components like the HDMI ports already selectable and I can add them easily. According to the document you sent this is too much effort for one SOT-23-5. there should be a simple sot-23-5 component that we can simply drop like the HDMI port OOB.
SOT-23-5 it not a part you can buy, it is only the form factor of a device. It does not define what function it has. Is it a transistor? A voltage regulator? A diode? So it makes no sense to add a SOT-23-5 to a schematic because it’s not clear what symbol is needed to represent it.
You can only add devices to a schematic which have a clear function. Currently the following devices with SOT-23-5 package exist in the Microchip, Texas Instruments and Diodes Incorporated libraries:
74AHC1G14W5
AP2112K
LP5907-Q1
MCP3221
MCP3021
It’s not much effort, it’s done in maybe 2 minutes. It’s really easy and then you have the correct device in your library, with correct name, and you can generate a BOM from your schematic which will contain the correct part name, not just the (useless) package name.
But that’s all off-topic here, please open a new forum thread if you have a question which is not really related to this thread here. Thanks
