A couple posts ago I talked about the LED Matrix project we’re collaborating on as a group. Rick one of our in-house electronics gurus put together a great PCB layout. He was able to get eight of our LED driver boards up on one 4″x6″ photosensitive PCB blank. Chris was chugging along running his tests on daisy chaining the LED drivers on the prototyping bread boards. So far so good!
In an effort to learn electronics I volunteered to try my hand at circuit board etching the team’s custom LED driver boards. I’m happy to report that I got it to turn out awesome on the second try thanks to Collin Cunningham and his how-to video on DIY etching your own circuit boards. His instructions were excellent, but off a little. I don’t think it was his fault though; my positive developer, light source, and timing were a bit different than the ones he used.
PCB Etching First Attempt
As you can see here on this epic fail, there were two main problems. It didn’t “bake” under the light source long enough and I think I watered down the developer too much. See how gun-metal gray the entire board is? That was the problem. Too much of the photo resist was still stuck on the board before I put it into the etchant.
Check the Instructions on Your PCB
Collin’s video said to use a compact florescent bulb 6 inches above the board for 8-10 minutes. The instructions on the PCB I bought said 3 inches for 20 minutes. I also bought a small UV-C LED that I used at a close range just to be sure. The instructions also said you can use a germicidal UV bulb for 90 seconds. I think we may try to set one of those up at the makerspace, it would definitely would speed things up we have 3 more boards to do.
You can tell it was under the light long enough when you put the board into the developer. The photo-resist almost disappears within the first 10-15 seconds once submerged. The first board hardly changed from that green color even after being agitated in the developer for 5 minutes.
Don’t Water Down Your Etchant
In Collin’s video, he did a 1:1 ratio of etchant (ferric chloride) to water. I found this not to work very well…yes it feels like you are wasting more, but it can be reused. Plus be sure if it is cold in the room that you use a hot plate on warm to heat the solution otherwise it takes for freakin’ ever! That said, keep a digital food or laser thermometer on hand to make sure the solution doesn’t get over 130 degrees.
Agitating the etchant manually is a pain in the ass, so if I were to do it again, I would set up some sort of vertical chamber with a fish tank bubbler to keep the fluid moving. Oh, and it took about 35 minutes to etch this specific board, but honestly, it more so because we didn’t leave extra copper on the board outside of the main circuits.
Get A Micro Table Saw
Rick had a slick PCB table saw. The blade is only like 1/32 inch thick and made a great cut. Here is what they looked like after I removed the photoresist with lacquer thinner cut them into eight pieces. We now have hundreds of holes to drill and lots of molex connectors to solder.
Come by the Makerspace to Learn How
I’ll be glad to show you how it works if you’d like to learn how to etch your own circuit boards. As you can see the resolution is excellent and looks amazingly professional.
Once we’ve finished with the other PCB boards I will put together a full video on all the steps and post it on the Red Mountain Makers YouTube channel. Here is our first test. Stay tuned, much more to come. We’re almost half way there.