How to design your own custom PCB Ruler in KiCad

Who doesn’t love a good PCB ruler? Few engineers would turn their nose up if handed one at an expo. And it makes for a great branded gift. So when thinking of swag ideas for NextPCB, I jumped at the chance of designing my own ruler.

This post sums up my experience creating the DFM RuleR and tips on how you can create your own, including insider tips from a manufacturing perspective to make sure it comes out as pretty as possible. After working in the Chinese PCB manufacturing industry for over 8 years (and exploiting the free PCBs), I have seen a good share of interesting PCB art techniques, failures and their solutions. The discussions here are geared towards online quickturn PCB services like those offered by NextPCB, JLC and PCBWay because - let’s face it, this is what most of us DIYers can afford. 

Many of these tips don’t just apply to rulers. Whatever PCB art you’re making, I am pretty sure you’ll encounter one or two new tips you’ve never heard of.

Close-up view of the NextPCB DFM RuleR design with KiCad

What you are not going to find here

KiCad and Gerber files - This is a post about designing your own ruler - go design one. See the appendix for a detailed rant explanation on why this design is not public.

I like PCB rulers as much as the next person but...

Nowadays, they all look the same except for a change of logo and they’re not all that useful anymore. There are even people selling the standard PCB ruler designs and offering white labeling services. But there are a lot more useful references that engineers could benefit from at hands reach, aside from the standard component footprints and trace widths.

So what would the ruler feature?

My position here at NextPCB provided the answers. Part of my job is to promote NextPCB’s PCB design analysis software called HQDFM. I had used it even before I came to work for NextPCB in the early days when it pretty much helped transform the industry (in China at least). Before then, I had helped write a DFM booklet that had a ton of specific figures on recommended clearance values and dimensions accompanied by illustrations. It wasn’t just generic stuff like ensure there is sufficient space between the board edge and the trace (how sufficient is sufficient?) and it was stuff recommended by manufacturers who would look at customers’ files all day. They had to decide on these rules, and now they were all available in a little booklet, a booklet that I had on my office desk at all times.

To be fair, looking at my desk now, it seems everything is on my desk at all times, but at least I knew exactly where to dig for it.

It was nice to have a physical reference I could just grab and flip to the folded corner, instead of scrolling through hundreds of bookmarks and tabs looking for the right page - something of a rarity in this day and age. I thought it would be nice to preserve that experience with a PCB ruler with DFM rules and helpful manufacturing related information. Oh and the best part? It’s another excuse to play with KiCad during work hours. 

Why use KiCad for PCB Art?

Like many others, KiCad has always been my tool of choice for PCB art. The open-source nature and resident KiCad art fanbase mean there are many tools and workflows available to create some truly breathtaking pieces within the limitations of what is possible on a piece of FR4. A quick Google search will showcase many prime examples of PCB art, most likely made with KiCad in combination with other tools. 

Thankfully, this particular design didn’t need any of that fancy work, and unless you intend to add some complex graphics, KiCad’s built-in tools are more than enough to create everything you see on this ruler.

NextPCB also has a close relationship with KiCad beyond the regular $$$ sponsorship, including hosting KiCon Asia which is always a lot of fun. You can even download KiCad from NextPCB's gateway page and get free PCBs for your KiCad design. So with this ruler, I was hitting all my targets with one stone; KiCad, HQDFM, NextPCB.

Forewarning

Before we get started, as with any PCB art project (not the UV inkjet printing stuff), it is important to remember that the fab house likely doesn’t want you doing this! PCBs are printed circuit boards, not printed paperweights, so, as you can imagine, the entire manufacturing and quality management process is tailored to making qUaliFyinG ciRcuIt BoaRds. Standard DRC and DFM rules don’t apply and the technician looking at your files has to make many non-standard decisions on how to approach your design.

Working circuitry might not necessarily be important for your PCB art, and it probably doesn’t matter if solder mask is broken here or there, or an exposed piece of copper is not large enough to test. Likewise, it is unfair to judge a manufacturer’s quality based on these non-standard elements, as you are essentially rewriting the rulebook. Something may look ugly, but it is perfectly allowed under IPC Class 2 (the most common inspection standard). Likewise, a defect that would usually fail quality inspection could pass through because you said just follow the files. It’s entirely subjective.

At the end of the day, they are just aesthetics, so don’t get in a fit if something doesn’t turn out right or the same set of files produces different results (such complaints probably won’t get you anywhere except for a bad relationship with your fab house). The best we can do as artists working on a borrowed medium is to minimize the chances for error in the design, experiment, and try not to over-complicate things.

How to select PCB Parameters for your Circuit  Board Art

Color Palette

From the onset, you should have a basic idea of what the final design should look like, especially the color palette. The choice of solder mask color will have a major impact on the range of colors available at your disposal and will influence the overall appearance.

-- If you don’t know what Gerber files, solder mask, silkscreen, surface finish are, I suggest getting familiar with this before diving in. Though the image below pretty much sums it up. Thankfully, the layers in KiCad are very intuitive and pretty much correlate to the Gerber layers that are used for production, with the exception of the drill layer.

Possible PCB art effects

Color Recommendations for artistic PCBs

Generally, green and yellow provide a strong contrast between areas with and without copper beneath the solder mask layer, followed by red then blue. White and black on the other hand produce nearly no contrast at all, in exchange for a more subtle embossing effect. 

Also, note that the exact color and degree of translucency of solder mask and substrates may vary between manufacturers and even batches. FR4 substrate is slightly translucent, so the appearance of lighter substrates can be influenced by lighting and the color of the surrounding solder mask as is evident in the image above. In strong lighting, you may even see features on the other side of the board, especially with thinner substrates which may be undesirable. However, for a quickturn service, you likely cannot dictate what color FR4 the manufacturer uses so my advice would be to just live with it and accept that there will be variations - oh and don’t get me started on custom solder mask colors.

For this matte black ruler with ENIG surface finish, I only had three colors in my palette:

• Dark dull yellow (bare FR4)
• Matte black (solder mask)
• White (silkscreen)
• Gold (ENIG surface finish)

Oily fingers beware! Matte black is very susceptible to grime - You have been warned.

Personally, I think matte black and ENIG were just meant to be so I am more than happy to give up the extra shade. Bonus - NextPCB doesn’t charge extra for matte black. ENIG, on the other hand, is another story..

Surface Finish

With a quickturn service, you really only have two surface finish options - gold (ENIG) or a shiny silver (HASL). The silver shine of HASL surface finishes can look tacky and uneven; however, ENIG surface finish has a layer of real gold, so don’t expect it to come cheap. And if your boards need a lot of gold (large exposed copper surface area), be prepared to pay extra! I intentionally kept the gold surface area below 25% (you can find this value using HQDFM). If you are making a big batch, the costs spread out, so I certainly think it is worth it. 

Also, did I mention that ENIG ages like fine wine? The ENIG finish on a board left out in the open has a stronger, darker hue compared to one ripped out of the package, which is almost whitish. In the photo below, the green board on the bottom is a couple of months old, and the top board was just removed from the heat-shrink wrap.

With HASL, the surface will probably just get more grubby and dull as time goes by.

Board Outline

As with any new design you should start with the board outline. You’ll notice this ruler can’t measure the full 30cm like a typical ruler since it has a rounded end, not unlike many stainless steel rulers. Why? ‘Cause it looks fun with the huge golden plated hole in the middle and it decreases the risk of injury when you swing it around like a pendulum. (If someone knows why these mounting holes have vias please let me know)

The curved edge was made using the arc tool then making sure they lined up exactly with the ends of the straight edges. You can make sure they are lined up exactly by entering the same x and y values in the properties window.

You can also use the outline to add more dimension to your art, in addition to your color palette. But use it sparingly - we are milling out PCBs with a tool bit of 1-2mm diameter, not laser-cutting paper, and too much milling could increase costs. Plated through-hole elements should be limited to small slots and plated drill holes.

And unless you want to file down rough edges yourself and get fibreglass in your eyes, you shouldn’t be panelizing the design. For big batches, be sure to specify singular boards, not a panel for that nice smooth edge.

Background Pattern

The ruler uses a cross-hatched copper plane fill for the background pattern. If the grid size is small enough, this produces a subtle raised gradient effect. I find a hatch gap and width of 0.3mm produces just about the right level of gradient without appearing like a hatched copper pour from arm’s length.

Adding a hatched copper pour for a raiseed gradient effect

Playing with a copper pour background is finicky and it can take some time to get the desired effect. For example, the gradient will impact the clarity of fine silkscreen text printed on top. You can get around this by adding a solid copper block underneath. In the NextPCB ruler design, I used a combination of solid blocks in the same net, in different nets and copper voids to make various raised and depressed effects.

Vias, plated holes, text, shapes

All the other features on this ruler were made with KiCad’s basic tools and stock footprints so there is not much to say about these. As said before, keep plated elements small since these are typically are drilled out (not milled). If you need larger plated holes and slots, they will likely incur additional processing costs.

Importing and modifying simple graphics

So you are probably going to need some simple graphics on your ruler to make it your own. KiCad’s in-built Image Converter tool is perfect for the job and is very simple to use.

The KiCad Image Converter tool was used to add the main logo and certification logos to the design

How to import graphics into KiCad

1. 1. Open the Image Converter tool via the main KiCad menu:
   
2. 2. Upload your image (doesn’t have to be a bitmap, png is fine).
   
3. 3. Change the output size to whatever looks nice on your PCB.
4. 4. Select Output Format -> Footprint (.kicad_mod file).
5. 5. Choose the layer you want to export the graphic to: front copper, solder mask or silkscreen.
6. 6. Click Export to File.. and give your new footprint a name.

Now, like any other footprint, you can add it to your layout and even edit it in the footprint editor.

Tips:

• Use a large, high resolution image then change the output size to whatever size you need. A small image will produce a vector with fewer points, resulting in a less accurate representation.
• To make multilayer effects like this ruler’s logo, you can edit the footprint in the footprint editor. Select the vector shape you want to change and change the layer in the properties window. To create the exposed copper effect, ensure the shape is present in both the solder mask and copper layers. You can also tweak the shape in the footprint editor if a section looks too thin etc.
• Be aware of the minimum size limits for certain effects. The small text in the ISO logo is 0.4mm in height. 0.4mm! That’s less than three times the standard minimum trace width/spacing for most fabs. I am surprised that it even came out somewhat legible - and it may not every time. With HASL surface finish, it will be harder to get the fine details out so more space should be left between exposed copper elements. 
• Always use the 3D KiCad Viewer to preview your design! It updates almost instantly so you can leave it open as you tweak the design. Note that some features such as the outline can be difficult to interpret correctly - the curved edge and milling slot have not appeared correctly in this case.
  
• If you need more complicated graphics, you can use an SVG to KiCad workflow which involves some scripting (the workflow I used before is now discontinued and I haven’t tried other ones for myself so no recommendations yet!)

Time to produce!

Tips for manufacturing PCB Art

Silkscreen on pads

This is the moment you remember that you are borrowing a circuit board fab to make your art. 

It is typically standard practice to remove any silkscreen printing present on top of exposed copper areas. Why? Because most of these exposed copper areas are going to be copper pads that required soldering onto in some way. The silkscreen ink will burn with the solder, potentially affecting the quality of the solder joint. Fab houses have automated tools to process Gerber data for production. This includes tools to remove silkscreen on exposed copper or even areas with no solder mask. KiCad even has the option to Subtract solder mask from silkscreen (should that be the other way round?) when exporting Gerber files so you can preview and have better control of the final result. Imagine with one click of the mouse, a huge chunk of silkscreen is deleted from your board without your knowledge.

How to work around this? Here are some solutions:

1. 1. Don’t put silkscreen on exposed copper
   
   Why would you deliberately do this anyway? White silkscreen on HASL or gold is barely visible and does not print as well as it would on solder mask. If you really need the silkscreen on copper effect, put solder mask underneath the silkscreen areas as well.
    
2. 2. Tell your fab not to delete the silkscreen beforehand.
   
   This is risky by itself because such a note can be easy to miss or misinterpret, especially with fab houses where the native language is different or there is no option to add a note (and ensure they follow it). 
    
3. 3. Ask to see the Production or Working Gerbers
   
   Working Gerbers, production files whatever you call it, these are the Gerber files after modification by the fab house’s engineers to suit their production processes. This includes tweaking trace widths, unifying the outline, widening solder mask openings, drill holes etc. and changes such as deleting parts of the silkscreen. Importantly, these are the files that they use to produce your boards and some fab houses have the option to let you review these files before they go into production. They are in Gerber format though, so you’ll need a Gerber Viewer and an understanding of how to read them. HQDFM has an online Gerber Viewer version as well for quick checks though the offline version offers much more depth.
   
   Checking the final working Gerbers is the most reliable way of predicting how your boards will appear when produced and is a must have for artistic PCBs. What’s more, when you are happy with how a design came out, you can use the same working Gerbers to ensure they come out pretty much the same way (allowing for slight manufacturing tolerances) without having to answer the same questions over and over again.
   
   Even better, leave a note and check the working Gerbers for peace of mind. That way you can double check if the engineers have understood and followed your notes and if not, have them make changes.

About leaving notes..

If you can reliably add notes and get them noticed before production, you might as well add some other, important notes. Some order forms have the option to select these features directly, which is always better than adding it to the notes section. 

• No production mark on the boards: This refers to the custom code added to working Gerbers to identify the boards as they go through production and after. There’s no telling where they’ll put it and it can be a real eyesore. But without it, it can cause some extra hassle during production and complicate the quality complaint process (how can you prove your boards were produced with company A, and not company B?)
   
• Aesthetic boards: To be honest, I am not sure how to word this so non-fluent speakers get it, but this is how it translates from Chinese and has worked for me in the past. What this implies is that the design is for aesthetics only and therefore does not need to work electronically. The appearance matters, not the circuitry. It’s a one-up from “just follow the files” which carries it’s own risks.
  
  If you want to go further, you can also try negotiating the testing fees off the price for larger batches. Prototyping and small batches - not so much as there is generally no testing component to the price.
  
  You can say something like, ”These are aesthetic boards, no testing required, do not remove silkscreen from solder mask openings, do not add production marks”.

PCB Manufacturers

So it may come as no suprise that this ruler was made by NextPCB. As a NextPCB employee, I’d be told off for not exploiting this opportunity to advertise our services but even before joining NextPCB, most of my art PCBs were made by them and I worked with them even before they were called NextPCB. Quality aside, the two most important features that ensured the boards came as expected were firstly, the ability to add precise notes that will be reviewed and secondly, the option to review working Gerber files. With these two features, you can catch many potential issues beforehand and have much better control over the results.

Why the NextPCB DFM RuleR design files are not available

I have had a number of people ask for the Gerber files of this design and I am all for open-source but after some thought, sharing this particular design doesn’t make sense:

1. 1. I’m flattered you like the design, but who would pay $50+ for a few copies of a ruler advertising someone else’s services? No matter how much you love them, would you fork out your own cash to print out a Walmart branded mug? I don’t think so. 
   
   Yes, you could make it cheaper by changing it to green with leaded-HASL - but it looks cheap and is still quite expensive, not to mention the tarnishing. A truly cheap ruler would be less than 100mm, but what are you going to measure with that?
    
2. 2. This design is non-standard. If you've read my post you will understand why chucking the files at a random board house will not get you the same result. You will either get a ruler full of fugly mistakes or be bombarded with questions. To make my point, if you run DFM analysis on this design in HQDFM, depending on your computer’s specs, it may crash due to all the errors in it. These errors are what fabs have to deal with and after years of working with NextPCB’s engineers, I’ve devised ways of maximizing success (some of which is shared above) that works with their standard processes and doesn’t bother them too much.
    
3. 3. To be frank, this ruler it is designed for promotional purposes; advertising NextPCB’s workmanship, the HQDFM software and showcasing the capabilities of KiCad while containing some useful information from HQDFM. We hand them personally to visitors at expos and events. If you really really want one, come to one of our shows! We’d rather you had a personally quality inspected ruler rather than you going off printing one yourself.

So to stop it from becoming the next ‘standard template’ distributed online with someone else’s logo slapped on it, I have decided not to make the files public. What I can give you however, is a KiCad template with stuff that rulers have like numbers and lines, because that’s what makes a ruler a thing that measures lengths.

Hey, you made it!

Congrats on making it to the end of the article (or did you skip here for the source files?). I hope you enjoyed it as much as I enjoyed writing it. Has it inspired you to go forth and create some of your own PCB art? Have other tips not listed here? Share it in the comment section below.

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About the Author

Carmen Zheng, content creator at NextPCB

With over eight years of experience in China's PCB manufacturing industry, Carmen has built a diverse expertise spanning operations, technical support, sales, content creation, and community engagement in electronics manufacturing, assembly, and EDA software. A UK native with a Master's degree in Electrical and Computer Engineering, her innate curiosity for how things are made and unique Western-Eastern perspective enable her to bridge cultural and technical gaps while amplifying Chinese manufacturing expertise globally.

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