WS2812B Neopixels

Hello Guys,
I am working on a WordClock with a lot of Neopixels. All the neopixels have very specific locations, thats why I decided to work for the first time with a PCB software: KiCad. This way I can position al the neopixels precisely. I used one of the footprints available in the library. The neopixels have a small piece for its connections (see picture). When I make the PCB, it will be completely covered with Soldermask. This way I can’t solder the Neopixels on the PCB. How can I add pieces of exposed copper in KiCad so I can solder the Neopixels on the board?


If I understand the question correctly, the answer is something like “Make a proper footprint for the Neopixel. The bits of copper where the Neopixel solders to the board are called a “pad”, and will be clear of soldermask if it is defined correctly.”

Can you attach, or post a link, for a manufacturer’s Datasheet for the Neopixel? Chances are, a usable footprint has already been defined.


These are the Neopixels.

I found them already in a library as: WS2812B. I thought it was exactly what I need.
This is how it looks in my Gerber file. The way it seems, I won’t be able to solder on this right? Thanks for your reply.

Typically a component in a design is represented by a footprint (or more precisely the land pattern of a component is part of the footprint)
This land pattern defines the interface between the pcb and the component via so called pads. Pads contain a definition for the copper area needed and also a definition for the soldermask cutout.
This soldermask cutout can be disabled in the padsettings so it might well be that you do not have it for your design.

With your screenshot we can however not really tell for sure if you have soldermask or even pads (A gerber does no longer contain information about pads and you did not select the mask layer as the active layer which means it could simply be “below” the copper layer.)

These FAQ articles might help you:

Thanks for your reply. It looks like the only thing I have on Soldermask are the ‘pins’ of the neopixels.

How can I actually add soldermask. I also mailed with someone from a PCB manufacturer and she said I didn’t have soldermask.

If you have the pins on the soldermask layer then you have soldermask. The soldermask layer in all design programs defines where no soldermask should be (that is why i talk about cutouts)

Is it possible the guys at your manufacturer missed that file or did you forget to send that one? Another option would be that they expect it to be named differently than what you named it.

Or also possible: They did not mean that you do not have soldermask but that your pad to soldermask clearance is too small.
There are many options so it might be required to ask for clarification.

Another possibility is that there is a misunderstanding. Maybe they thought you asked about bottom soldermask which might really be empty if you do not have any pads there.

Thanks man, I will ask them again. And I know for sure I send all Gerber Files double checked on that. This is what she said:
“And your file seems ok,but no drill holes, bottom copper and solder mask.Could you please check and fix ?”.

I have 3 traces on the bottom Layer (the 3 green lines on the picture above). I made them using vias. My intention was that I could solder wires on those traces, but I can’t. Can’t I add pads there? I did some research and found out that somewhere in the library there are: Wire pads. Can’t I use those to make some pads?

Thus so far I understand it like this: On the Front Soldermask layer in Kicad, wherever I see things, those are the pads, the places with no soldermask?

And my last question: I also wanted some mounting holes. I did that on the edge.cut layer, just like the board layout. Is that OK?

This is the footprint I used, it seems like there are pads (or am I wrong). Because if those are pads, I don’t have to worry anymore.

That is correct footprint. I’m using it on regular basis.

So I can solder the small Neopixels on the PCB with this (I need to be sure ahahah)? Thanks for your reply.

I start my traces exacty on the pads. Is that a problem?

Correct. The Solder Mask layer is the only negative layer, it shows the areas that will not have Solder Mask. This can typically be easily seen in the 3D viewer.

Probably not, but it does depend upon the Fab House that you are using. It also depends on whether or not the holes are to be plated/through plated or not. Typically the holes will be drilled with the Drill File, and not the Gerbers.

That should be fine.
In the Layers Manager move the selection arrow down to the F.Mask layer. This will bring that layer up front and give an representation of the pad that you will be able solder to; this is affected by some of the Design Rules Settings.

I am new to this community, damn you guys are awesome. Thanks this helped me a lot. Do you also know how to add a pad random on the back of my board. I want to connect the green lines to a wire.

Any through-hole pad will have copper lands on both sides of the board. I vaguely recall that KiCAD has a library of single-pad footprints intended for exactly the purpose you have in mind: soldering wires directly to a board. Or maybe they are called “Test Points” in the official libraries. Many of us just plunk down the schematic symbol for a generic one-pin connector (from one of the "Connector . . . " libraries) and associate it with a single-pad footprint. From a library, or self-made. (If you’re gonna do more than half a dozen boards over the next few years, you REALLY SHOULD learn how to make your own footprints. It’s not difficult, and a one-pad footprint is about as easy as they come.) The factors to consider are making the drill hole an appropriate size for the wire you’ll use; and making the copper pad large enough to give the attachment point some strength and enough room to get a soldering iron into place, but not so large that it eats up too much acreage on your board, or sucks all the heat out of your soldering iron. If you add a handful of vias to the copper rings on your wire attachment footprints, the attachment point will be stronger, and people who see it will think you have your feces amalgamated when it comes to designing PC boards.

NOTHING beats hardware, but a picture is worth 1x10^3 words. Play around with the nearly unlimited ways that KiCAD can display information. Perhaps even cobble together a test project using a couple Neopixels, some vias, a few wire attachment pads, perhaps even a filled zone. Use the “Layer Mangler” on the right side of the PCBNew window to step through the available layers, one at a time, and see what information is on each one. Then try various combinations - depending on which stage of a design I’m in, I seldom display more than three or four layers at once. Try the “Outline” and “Hi Contrast” display modes. Turn various “Items” (Pads, Hidden Text, Values, etc) ON and OFF, to see how they improve (or degrade) your personal perception of the project as a whole.


Thanks again for your response. I have looked up for that Test Point library and I found the pads. Can I place them just on the green lines on the bottom layer?

Your helping me a lot. I am a Mechanical Engineer in the Netherlands, but I love electronics. That is why I am doing projects like this, learning to work with PCB Software etc. Trying to improve my electronics skills. Thanks for your help again.

Select your test point and press “f” to flip it to the bottom of the PCB.
Then use the 3D viewer [Alt + 3] to get an idea of what the PCB looks like.

I think it’s also a good idea if you start reading some user manuals and tutorials instead of firing questions at the forum every hour or so, but if you get stuck somewhere or have non trivial questions you can of course always ask for a bit of help.

Thanks. Yeah you are right man. I watch some tutorials of course, I will do some more research!

You are in good company. In ancient times (1960’s into 1980’s, when PCB layout was done with tape on mylar) many of the people who designed layouts - perhaps the majority - were mechanical engineers, or draftsmen, by training. They did good work. I recall one PCB designer, from several incarnations ago, who claimed that laying out boards, even with multiple layers, was easier than designing piping in chemical plants - his previous job.


Yep that was fun.

We have been laying out pcb tracks with brady tape symbols and strings off of the roll on aluminium reinforced grid paper at scale 1:4 :+1:

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