Have you ever wondered how circuit boards get those detailed copper circuit traces on them? Magic? Nope, it’s etching PCBs process!
From home hobbyists to large industrial manufacturing facilities, etching PCBs is done all the time.
If you’re getting started building Arduino boards or just curious how PCBs are made by commercial factories, etching is the process that turns plain old copper clad board into a circuit board with connected traces.
In this article, we’ll cover everything about etching printed circuit boards. Let’s get started!
What is PCB Etching?
PCB etching is similar in a way to carving a sculpture. Instead of taking something away, though, you’re depositing a design onto the copper layer of your PCB and then removing the excess copper.
You take your plain copper-clad board. Copper-clad board is basically fiberglass with a thin sheet of copper bonded to one side (both sides for double-sided).
You then add a coating of material on the copper that you’ve transferred your design to that will protect the copper underneath it during etching. The etchant will dissolve unprotected copper, but not the protected copper that you coated with your “resist.”
When all the exposed copper is gone you’re left with just the copper you want remaining to connect up all the components on your board.
Etching removes excess material instead of adding it on so it’s the opposite of 3D printing for example.
Why Do People Etch Their Own PCBs?
Okay sure, you can get your PCBs made by uploading your design to the internet and some magical people in China make it happen.
Professional PCB manufacturing services have gotten really affordable over the last few years. You can get basic PCBs made for next to nothing in a matter of days.
So why would you ever want to etch your own PCBs?
Well, if you need a board right now there’s no waiting involved when you etch at home. Teaching the intricate details of how PCBs work by letting someone else make them for you just doesn’t have the same impact as doing it yourself.
Methods of Etching PCBs
Wet Chemical Etching
Wet etching is how most people think of etching PCBs. You dip your board into a chemical solution that will eat away the copper on your board.
The most common etchant that DIY’ers use is ferric chloride. It’s just a rust colored powder that you mix with water to create an etching solution.
The etchant will work at room temperature, but will go faster if it’s heated. Depending on how hot you make your etchant and how thick your board is will determine how long etching takes. On average you’re looking at 15-30 minutes.
The downside to ferric chloride is that it stains everything it touches. That means your clothes, your board, your work surface, and unfortunately your skin.
Pouring used ferric chloride down the drain is also illegal in most places as it’s considered hazardous waste.
Most commercial PCB manufacturing shops use cupric chloride for their etching needs.
It etches faster than ferric chloride and can be regenerated continuously in industrial setups.
Another option if you’re into the real DIY ethic is to make your own etchant using white vinegar, hydrogen peroxide, and salt.
It actually works, just takes about 30-60 minutes to etch your board. Don’t heat this mixture or you’ll have a Science Project on your hands.
This etchant is much safer to work with than ferric chloride. It doesn’t stain anything, gives off very few fumes, and can safely be poured down the drain when you’re done.
The downsides? It takes forever to etch your board compared to the metal chloride etchants and will only keep for a few days before it goes bad.
Laser Etching
Lasers have become quite affordable for industrial users as well. Lasers can etch your PCB by blasting the board with a laser beam wherever you don’t want copper.
Lasers don’t use chemicals or create any liquid waste you need to clean up. You can achieve incredibly fine detail with a laser etching your PCB.
Unfortunately they’re also expensive. You’re not going to be rigging up a laser etching system in your garage.
Plasma Etching
A more recent innovation in PCB etching is plasma etching. Plasma etching uses a form of ionized gas to “eat away” the copper on your PCB.
It’s much cleaner than using wet chemicals. Like laser etching it’s also incredibly precise. Plasma etching is also becoming common for producing semiconductor grade PCBs as well.
DIY Etching Step By Step
Materials Needed for Etching Your Own PCB
- Copper clad board (ideally FR-4 which is glass-fiber-reinforced epoxy)
- An etchant of some kind
- Transferring material of some kind-glossy magazine paper, photo resist film, or even just a sharpie works
- Chemical resistant gloves, safety goggles, and an apron
- A ventilated working space (outside is best)
- plastic containers (not metal), acetone, drill bits, sandpaper
Toner Transfer Method
Design your PCB in whatever program you like. KiCad, EasyEDA, and Eagle are all popular choices.
Print your design to a glossy magazine sheet of paper using a laser printer. Inkjet printers won’t work for this method.
Cut your PCB to the size you need it and sand the entire copper surface really well. You want to remove as much of the top layer oxidation as possible.
Clean the copper with acetone to remove any remaining oils from your skin.
Place your printed design face down on the copper surface of your PCB. Using a clothes iron, apply heat to the back of your magazine paper. 5-10 minutes with firm pressure should do the trick.
Remove from heat and soak in water. The paper should easily wipe off, leaving behind the toner on the copper.
If you find any spots you messed up, just use a sharpie to cover.
Photoresist Method
This method takes a bit more work than the toner transfer method, but will create nicer results with complex PCBs.
Pre-sensitized boards come with a photo resist already applied. You’ll need to create a transparency of your circuit board design.
Print your design on a transparency using a laser printer. Exposure to UV light will harden the photo resist.
Place your transparency on your PCB and expose it to UV light. Fluorescent light works if you don’t have anything better.
Develop your board in the included solution. The unexposed photo resist will wash away, revealing the copper that will be etched away.
Etching Process
- Once you’ve applied your design to your board you’re ready to etch! Grab a plastic container big enough to fit your board in and fill it with your etchant of choice.
- Place your PCB copper side up into the etchant. This is important because copper that has been dissolved will sink to the bottom.
- Agitate the solution the entire time your PCB is in there. Rock your container back and forth, swirl the liquid around, or brush the solution over the surface of the board.
- Stirring your PCB ensures that fresh etchant is constantly flowing over the surface of your board which dramatically increases etching speeds.
- You’ll start to see the exposed copper disappear. Periodically check on your board to see how things are going.
- You don’t want to over-etch your board or you risk your traces becoming too thin or even breaking apart.
- Rinse your PCB off well with water when you’re finished. The more water the better. Soak your board in water to halt the etching process.
- If you used a photoresist you’ll need to strip it off using acetone or a dedicated photoresist stripper.
- Inspect your board carefully under a strong light to make sure you didn’t miss any spots and everything looks as it should.
Troubleshooting Common Problems with Etching
If your board hasn’t etched completely there are a few things you can check. Weak etchant, not enough agitation, and cold etchant are usually the culprits.
Make sure you mix up a fresh batch of etchant if it’s been sitting for a while. Etchant also etches faster when it’s warm-aim for 40-50*C.
Too much agitation can cause thin traces so don’t go overboard, but not enough and you’ll have etching that just doesn’t finish.
If your PCB traces are too thin or broken, you’ve over-etched your board. Agitate constantly and check your board every 5 minutes to ensure you don’t overdo it.
Poor transfer means gaps will be left in your design. Use the correct type of paper and make sure you’re applying enough heat and pressure.
Safety!
Do NOT skimp on safety when working with chemicals. Wear chemical resistant gloves, goggles, and an apron to protect your skin from splashes.
Etchants will cause severe chemical burns if they come into contact with your skin. If you get etchant in your eyes, seek medical attention immediately.
Ventilation is also extremely important. Etching should be done outside if possible. Some of these reactions give off nasty fumes you don’t want to breathe.
Stay away from food and kitchen areas. It’s way too easy to accidentally contaminant food with PCB etching chemicals.
Have water handy to rinse yourself off if you get any chemical spills on yourself. Store chemicals in clearly labeled bottles away from children and pets.
Used etchant is considered hazardous waste so you’ll need to follow your local governments lead on proper disposal methods.
Dumping used etchant down the drain is illegal in most places. The etchant contains copper which is considered polluting water supplies.
Talk to your local environmental protection agency about how to dispose of used etchant safely.
DIY PCB Etching vs Sending Your Board Out For Manufacture
If your board is single-sided and doesn’t have super tight trace spacing etching at home is a great option.
You also want to consider how long you need your board. Ethernet needs it now kind of projects are great candidates for DIY etching.
Anything you want to learn about or use as a teaching tool also benefits from DIY etching. There’s something about holding a circuit board in your hands and realizing you made that from scratch that just isn’t the same coming in a kit from someone else.
Sending your design out to be manufactured wins if you need anything more complex than very basic single-sided boards.
Double-sided boards with connections on both sides, multi-layer boards, fine-pitch parts with tight trace spacing, or when you need multiple copies of your board all come out better when made by professionals.
Prices have come way down on ordering custom PCBs as well. You can get professionally manufactured PCBs from China for just a few dollars now and they’ll ship within a few days.
You really aren’t saving that much money by etching your own really simple PCBs if you have to go out and buy all the materials.
However, if you need a board designed and in your hands quickly there’s nothing beats etching at home. Same goes for the knowledge and education you gain from doing it yourself.
Conclusion
Start with simple projects if you want to try your hand at etching your own PCBs. A single-sided board with large trace spacing is a good beginner board to work with.
Like anything, the more you do it the better you’ll get. Build up to more complex projects as you gain confidence in your skills.
Safety should be your number one concern when working with chemicals. Don’t take any shortcuts with gloves, goggles, and other protective gear.
For Rush PCB UK, wet and dry etching are two necessary processes for manufacturing printed circuit boards. While both aim to achieve the same results, their modes of operation differ. They also use different chemicals for the process.
