Yes! It’s Tuesday!
Everyone gather ‘round and let’s talk about etching our own circuit boards at home. It’s cheap, it’s easy and, while it does have some limitations, it’s FAST!
If you’ve never done it before, hopefully there’s enough info here that you’ll want to give it a shot. If you’re a seasoned veteran, give the rest of us some tips in the comments section!
Adventures in Circuit Etching
Got all that? Okay, so it was a pretty quick overview but the good news is… making your own PCBs at home is super easy and fun! But why would you do it? There are a few reasons. It used to be that PCB manufacturers had no idea that there were hobbyists who might be interested in ordering custom boards. As a result, they weren’t prepared to manufacture or sell small quantities. Beyond that, most hobbyists didn’t have access to the design tools necessary to draw designs for those manufacturers. These days, if you need a bunch of complex boards with multiple layers or tight tolerances, you can order from companies like OSH Park or Advanced Circuits for modest cash. That doesn’t mean, however, that etching your own boards isn’t still a totally relevant skill for makers. Here are a few reasons you might make your own circuit board:
Rapid Prototyping - It takes less than an hour to print a PCB yourself, so if you’re iterating very quickly through a lot of designs, why wait a week or two for every new prototype?
Simple Designs - If all you need is a rough and ready one-layer board, it might be more trouble than it’s worth to order out.
Total Control - Do you want to make a circuit board out of ballistic nylon? Do you need a really thin, rigid PCB? Do you want to embed RFID tags in your PCBs so you can identify them later? Do it yourself!
Doing an Art - Importing arbitrary pictures into a Gerber file can be really tough, and I haven’t found a PCB manufacturer that will take a series of SVG drawings as design files. Most fabricators have trouble with weird shapes and cutouts as well. Making your own PCBs opens up a whole world of unique materials and shapes.
It’s Fun - It really is rewarding to make your own circuit boards; why not give it a shot?
All that being said, there are definitely limitations. Two-layer boards are pretty hard to make at home for two reasons: It’s hard to line up both sides of the board so that your vias are on top of each other, and it’s next to impossible to make clean plated through-holes. Another limitation is feature size; if your design includes parts with a really tight pitch or super skinny traces, you might find it hard to avoid over-etching. Finally, while there are ways to print your own solder mask, it’s another step, and it’s not always consistent. Without a solder mask, it can be hard to solder tightly packed parts without flooding the nearby footprints.
“How it do?”
So you watched the video and now you’re interested, but you’re still confused. No worries! Let’s walk through the process and I’ll try to point out some tips and tricks to make it go a little more smoothly.
First though, a few basics:
Most PCBs are made from a material called FR4, which is a glass-reinforced epoxy composite (basically a sheet of fiberglass) with copper traces on one or both sides for carrying signals. While it may look like the copper traces are printed onto a blank sheet of fiberglass, the fact of the matter is that circuit boards usually start as a fully copper-plated sheet. You can buy this stuff online for super cheap, just do an Amazon search for “copper clad board.” In order to isolate the traces, all of the excess copper needs to be removed. This can be done with a mill or router like the Shapeoko, but traditionally it’s been done chemically. The problem is, your chemical etchant doesn’t know where your traces are supposed to be, so you need to mask them off and keep them away from the etchant.
Step 1) Masking the Board
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For the sake of this post, I’ll assume that you already have a design ready to go. If you want to learn how to design and layout your own circuit, check out our Eagle resources. You can also draw your own circuits in a vector drawing program, or even by hand! For today’s example, I’m using the Nanino, a “minimalistic, single-sided Arduino” by Johan von Konow.
The easiest method for getting your layout onto a piece of copper-clad is a method called “toner transfer,” where you print your design onto transfer paper using a laser printer and then transfer that toner using a press or an iron. Transfer paper is basically a plastic substrate coated in a powdery blue finish. You can order just a few sheets from sellers on eBay and Amazon. If you don’t have the time and money to order it online, you can substitute a glossy magazine page, and I’ve gotten some pretty decent results that way. When you’re printing your design, be sure that you’ve mirrored it so that after you transfer it face down, the design is oriented correctly. Also, print on a normal sheet of paper first to check your scaling and position.
Prepare your piece of copper-clad board by wiping it down with some alcohol. This will help remove oils and gunk that might keep the toner from sticking. If your board has been sitting in a humid environment for a while, it might need a quick shine with a scouring pad. Now cut out your design and place it face down on your freshly cleaned board. You can stick it in place with a few piece of masking tape.
If you have a desktop laminator, this next step is really easy. Just set your laminator to its hottest and slowest setting (usually a preset for 10mil pouches) and run your board with the transfer taped to it through the laminator four or five times. If you don’t have access to a laminator, you can use a clothes iron set on high with no steam. Apply even pressure to the board for maybe five minutes and don’t allow the transfer paper to move or slip against the board. It helps to put a piece of paper between the iron and the transfer sheet. Once your board has cooled off, peel away the transfer paper to reveal your resist! There way be spots that didn’t transfer cleanly; those can be filled in with a permanent marker.
Step 2) Etching the board
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There are a few different etchant solutions you can use to remove copper from a piece of copper-clad board. The most common (old-school) solution is ferric chloride. Ferric chloride is toxic, highly corrosive and acidic, but it’s also inexpensive and easy to get your hands on. I prefer to use it because, well… I know how to judge how fast it’s going to etch, and I’m familiar with it. Another popular solution is cupric chloride, which can also be toxic, but a lot of people prefer it because its etching strength actually increases as more copper is dissolved into it (to a degree), and it can be regenerated by aeration with an aquarium pump. A solution that’s really easy to get your hands on and is rumored to work pretty well is a mixture of muriatic acid (dilute hydrochloric acid from a pool and spa supplier) and hydrogen peroxide. If you’re worried about the toxicity of these solutions and want a slightly safer option you can try using a mixture of vinegar, table salt and hydrogen peroxide, although I’ve tried this in the past (out of curiosity) and it’s really slow and uneven.
You don’t need to be scared of toxic solutions, just be safe. Wear gloves, wear goggles, don’t put the solution into containers you plan to ever use for food – remember high school chemistry lab. That being said, you can get hurt if you do something stupid so be careful. And, by the way, never pour used etchant solutions down the drain no matter which etchant solution you choose. The concentration of dissolved copper is bad for the environment and rough on water processing equipment.
Throw on your personal protective equipment and dunk that masked board in the etch bath. This is gonna take a few minutes. One thing that’s important is to keep the board moving in the solution. As the etchant reacts with the copper, it leaves byproducts that inhibit the etching process, and the best way to keep that stuff from settling is to keep the solution moving around. I stir it with a plastic knife. You can also build etching tanks just for this process which either rock your etch bath back and fourth or bubble air up through the solution to agitate it. If you’re only making a few boards here and there, I would argue that stirring by hand is better because you’re going to be pulling the board out and checking on it pretty regularly anyway.
You can tell when the board is done etching because (surprise) the copper will be gone! As soon as you can’t see any copper, pull that board out of the etchant because it will tunnel its way in sideways under your etch resist and thin out the traces. Rinse the board with some water to get rid of all of the excess etchant, and then you can take off those awful, sweaty gloves.
Step 3) Removing the resist
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This step only deserves its own section because it’s so beautiful and satisfying. Take a paper towel with a little acetone on it (it doesn’t have to be concentrated, nail polish remover works fine) and wipe the etch resist away; it will come right off and reveal all those sweet, shiny traces!
Step 4) Finishing Touches
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Your board is pretty much done, now all you need to do is populate it. If your design requires through-hole parts, you’ll need to drill all of the holes. I used a tiny drill bit on my rotary tool for which I happen to have a fancy drill press. You can also just do this with a hand drill if you’re super careful. Then add your parts and solder everything in place!
Getting Fancy
Flexible PCBs
But wait! Copper-clad FR4 is not the only material you can use in home etching. There’s a material called “Pyralux,” or copper-clad Kapton, which is a flexible circuit board material. It’s more expensive than FR4 and it can be a little harder to work with, but the process is essentially the same! Check out the gallery below for a pictorial overview of my own experience with copper Kapton.
Roll your own substrate
That’s fun, what else can we etch? If you want to get weird, and you know that I do, you can roll your own copper clad board from scratch! In the gallery below, you can see the process that I went through to build my own fiberglass and Kevlar circuit boards. Copper foil can be bought in rolls on Amazon, and there are plenty of woven materials that are designed for composite layup. Simply spray two rigid plastic or glass panels with mold release, stack a few layers of woven fiberglass between the copper foil and then clamp the whole thing together until it hardens. From that point on, etch it just like any other PCB material!
Alternate methods of masking
If you happen to have access to a laser engraver (or if you’ve built your own) you can skip buying toner transfer paper! My preferred method of generating an etch resist is as follows:
Step 1) Wipe down your copper-clad board with some alcohol.
Step 2) Apply an even coat of spray paint to your board. I like to use flat black primer, but any color should work.
Step 3) Invert the color of your design so that you’re etching away the parts of the resist you want etched. This will leave spray paint only in the places that you want masked! Fire the lasers!!!
Step 4) Gently wipe the laser-etched board with alcohol. This will remove the burned spray paint but leave the un-etched paint.
Step 5) Etch your board chemically using your favorite solution!
Step 6) Remove the paint using acetone.
This is an awesome method for intricate or unusual designs like this:
It’s looking at you!
Go try things!
So that’s home circuit board etching: It’s fun, easy and cheap to do! If you have any tips or tricks, I’d love to hear them. If you have any questions, please ask away! If you have any ideas, go make something cool and send pics!
Oh! And if there’s anything in particular that you all want me to talk about on Tech Talk Tuesday, let me know. Until next time, happy hacking!
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