First I will warn everyone that this is actually my first ever attempt at etching a PCB let alone using my laser cutter for it. That said, I was successful with Laser Cutter PCB Etching on my very first try! So that should say enough about how simple it is. Below I will go through what worked for me and what caused some challenges. This motivation is a direct result of needing some PCB boards for my Christmas Light Display I am working on.
Second I want to place my disclaimer up front. As with pretty much everything you read on the internet, you should always be prepared for the worst case and know that I take absolutely no responsibility for anything that occurs as a result of reading this article.
Getting Ready To Perform Laser Cutter PCB Etching
Before I start the tutorial I would like to put out a list of things you will need.
- PCB Copper Clad Board
- Spray Paint (Krylon ColorMaster Flat Black worked for me)
- Safety Equipment (Rubber Gloves, Eye Protection, Mask)
- Plastic or Glass Contained To fit PCB
- Plastic or Glass Measuring Cup
- Plastic Spoon or fork
- Various Rags, Towels and Sponges
- Muriatic Acid
- 3% Hydrogen Peroxide
Step 1 – PCB Design
The first step obviously is to acquire your design. You can do this through Eagle from CADsoft USA or by finding your design some place on the inter webs. Regardless, you should end up with something like this.
There are a few important things to note about this layout.
- The layout is black and white, this allows the laser cutter application to know where to cut
- The image is mirrored Left to Right, I will explain how to do this in Eagle next
- The image colours are reversed. ie black is white and white is black. This is because the black is where we want to remove the copper.
Before printing, you will want to turn off the layers which you do not want included. This is done under View \ Layer Settings. On my board I have Bottom, Pads and Vias visible. Printing in Eagle is straight forward. Although my first thought was to Export… 😉 When you select print you an usually find the Microsoft Print To File (PDF) Writer. You will likely want to save it as a PDF because it maintains the size and resolution. The two options I selected was Mirror and Black. I actually exported using Adobe PDF Writer instead but Print To File (PDF) should also work. Once I had my PDF I opened it inside Adobe Illustrator and ensured that the board met the third requirement above (reversed black and white). How you reverse the image colour may very.
Step 2 – Laser Etching the PCB
The first part of the process actually begins with painting the Copper PCB. I gave my PCB boards a nice even coat of black spray paint over the copper using Flat Black Krylon ColorMaster Paint + Primer I picked up from WalMart. There was not anything special to this process. Although I cleaned off my boards first, they had a little bit of oxidization on them which I did not clean up but I think next time I will before I start the process. I found this article which has lots of ideas for cleaning the copper.
After letting the paint dry overnight, I through them into my 5th Gen 45w Full Spectrum Laser. I started by etching (rastering) the word TEST onto the board and began playing with the settings until I found something that seemed to work well. Interestingly I found that increasing the speed resulted in a better final result. The leftover residue wiped right off with a dry cloth and did not end up being baked onto the board. Something else I did specifically for this was to reverse the etching direction. Because my laser exhaust is at the rear, I began etching from front to back. This results in debris not being dragged over top of the completed piece. In the end I settled with 80% power and 60% speed but keep in mind that these values will fluctuate based on your specific laser / life.
Part 3 – Chemical Etching
I did a bunch of reading on this topic and decided that I would use the Muriatic Acid PCB Etching method. I am not a chemist nor do I know much about chemistry so I relied on others like this instructable.
Safety First – DO NOT SKIP
First and foremost, SAFETY COMES FIRST! Use some Personal Safety Equipment and do this either outside or in a large well ventilated room. Because it is pretty cool outside I opted to do this in the laundry room with the window open. Muriatic Acid is going to dissolve the copper, so you will want to be very careful with this stuff. I can’t stress this enough. You should also be aware that a stainless steal sink will be etched if the acid comes into contact with it! This is why I chose the plastic laundry tub. I also verified that the drain fittings were all plastic and I ran a bunch of water when I was done.
- Rubber Gloves
- Eye Protection
- Lots of water on hand to rinse off anything that contacts the acid
- DO NOT Work in a stainless steal sink
Get Everything Ready
Before mixing your chemicals, you should get everything ready and laid out in front of you.
I picked up the following at Dollarama;
- Plastic Measuring Cup
- Plastic Container with Lid to fit PCB and Store Chemicals
Mixing the Acid
Before mixing the materials you will need to find them first right? I am in Canada and this turned out to be a little harder than I first thought. Although Muriatic Acid is used to clean / etch concrete, neither Lowes or HomeDepot stock Muriatic Acid any longer (or at least in Ottawa). I eventually found it at a small Rona in Stittsville. The bottle was sealed inside a bag on the shelf. This might give you a hint that you’d better be careful with it! It is most likely you can find it at pool chemical supply stores since it is also used to clean concrete pools. In fact the stuff I found at Rona was labelled as such.
The Hydrogen Peroxide is easy to find. Just make sure it is the 3% mixture. I found mine at Dollarama but drug stores will also carry this.
I had some Acetone that I got at the drug store in the nail polish remover isle. It was 100% Acetone (don’t get anything with other chemicals or perfumes in it). The problem with this stuff was the price! Man is it expensive and was only a small bottle of 240 ml. I later found a 1 Litre jug at HomeDepot for the same price and that is what you see in the photo below.
Before starting to mix the chemicals, I filled the bottom of the sink with about 2 inches of HOT water. This provided me with three things during the process. First it warmed up my solution when I placed the container inside the sink. Second it gave me a supply of water on hand to rinse the board or anything the touched the acid without touching the faucet. And third it provided a nice frictionless surface to float the container on while swishing.
- Once your sink and supplies are ready, put on your safety equipment
- Measure out two parts (1 cup) of Hydrogen Peroxide and place into the container
- Measure out 1 part (1/2 cup) of Muriatic Acid and carefully pour into the container
- Swish or stir the mixture together with a plastic spoon and place into the HOT water in the sink and allow to warm up for about 3 minutes
Once your solution is nice and warm you should be ready to go you can carefully place your PCB into the container Painted/Etched side up. I let the board sit for about a minute and then took a soft sponge and carefully wiped the board. Do not use the hard scrub pad as it will remove paint if you are not careful. I did this because there seemed to be a layer of paint residue which was still on the board. Now I placed the board back into the solution and began rocking the container which swished the solution over the board. This seemed to take about 10-15 minutes to remove all of the copper. Once the board looks ready, rinse it off in the sink water and set it aside to dry. Repeat the process again if you have another board to etch. You may need to re-heat the water in the tub before you start.
Removing The Paint Mask
Now you will need to remove the paint. This is easily accomplished by putting some acetone on a rag and wiping away the paint. You will need to continually use a clean part of the rag to remove all of the paint residue.
Once it is clean, wash it off and dry it right away! I forgot to do this and the acetone caused the copper to tarnish once I left it alone for 30 minutes. As a result I needed to clean it up with Salt and Vinegar Solution.
Step 4 – Etching the Top (Optional)
I have no idea how safe this is yet as I still have to look into what the boards are made of. But my initial research seems to indicate it should be OK (or at least as “OK” as anything that is laser cut… I am using FR4 and it seems to etch pretty well although initial tests to vector holes has not gone very well.
I followed the same steps as above except this time I had the following layers visible; Top, Dimension and tPlace. I also did not Mirror the print or reverse the black and white. I placed my labels on the Top layer for simplicity. Alignment is the biggest challenge here and may take some practice to figure out. But in my opinion it is certainly the coolest part of the whole process! For my laser I rastered the image at 1% Power and 100% speed which produced a nice charred look almost like ink. If you really want you could probably wipe paint into this etching and end up with a permanent color etch. For my purposes, the black char works fine.
UPDATE: I found rastering the board for etching too slow so I switched to vectoring outlines. For this I vector at 100% Speed and 30% Power. This takes about 20% of the time.
Congratulations, you now have your very first Home Etched PCB! This is a wonderful feeling!