Etching Circuits at Home

Reading Time: 5 minutes

Long before Netflix or VCRs, a famous filmmaker once compared writing for television to building elaborate sandcastles – despite all your effort, after the broadcast, your masterpiece was lost to time. Sometimes I feel that way about breadboarding too.

Three years ago, a friend gave me my first Arduino. I’d never soldered anything or even made an LED blink, but after breadboarding the 15 circuits in the SparkFun Inventors’ Kit, I was hooked on hobby electronics. The problem was that once I got a circuit working, I’d want to keep it around to show friends or family, but also to clear the breadboard and start the next project. I ended up buying several more breadboards.

I recently wanted to learn more about microphones, so I breadboarded this simple volume meter circuit.

VU Meter Breadboard
All Photos: Mark Moran

My 3-year-old daughter loves alternating between whispering and shouting and watching the LED bar move in response. When I finally took the circuit apart, she wanted to know where her toy had gone. Luckily, in the past few years, I’ve also learned how to make my own circuit boards and build more lasting projects.

The simplest option is to order an existing kit and solder that together. I’ve made dozens of these and love doing so, but it doesn’t compare to the satisfaction of designing your own circuit.

The first permanent circuit I made was Project 14 in Charles Platt’s Make: Electronics, built on plain perf board where the component leads are simply soldered to each other. I found this technique maddening.

A big step up for my next circuit was to use copper-clad ProtoBoard. Now I could solder each component to the board and then route the connections together. A definite improvement, but still a bit messy with inadvertent solder bridges.

I realized it was time to learn how to make a printed circuit board.

There are dozens of fab houses that will make these for you, and I tried SparkFun’s BatchPCB when it existed and last year switched to OSH Park, famous for their purple boards. But a 2″ PCB costs about $30 and takes over a week, often too much and too long for something I’m building just for the fun of it.

My first experience with etching my own PCBs was inspired by Collin Cunningham’s excellent Circuit Skills video for Make and Jameco. I bought a desk lamp, pre-sensitized copper boards, transparency paper, a heavy glass frame, Datak developer, and ferric chloride. Unfortunately, converting our condo’s only bathroom into a chemical dark room was a long and messy process, and the results were inconsistent. The first two boards I made turned out fine, and it was extremely rewarding to make PCBs from scratch. But follow-up attempts never worked as well. I’d try five or six in a row that were either overexposed or underexposed or over-etched and in several hours I’d ruined $40 worth of boards. At that rate I should keep ordering professional PCBs.

I still loved the idea of rolling my own, so I started looking for alternatives. The next product I tried was Technik’s Press-N-Peel Blue sheets. Instead of printing a circuit onto transparency paper, you print it onto special blue paper and then iron it onto a regular copper board. This has the advantage of no darkroom, no exposure time, no developing time or chemicals, and cheaper boards. The problem is that no matter how hard or long I pressed with my iron, or how much I tried prepping the boards, I could never get the circuit to transfer well enough to make a working circuit.
Finally, I discovered PulsarProFX’s toner transfer system. This has all the advantages of the Press-N-Peel system, but uses a different type of transfer paper and then a second layer to seal the toner. The images are transferred onto the copper board using a modified laminator. I’d never owned a laminator, but the Apache 13P was only $80 on Amazon, and I figured with two little kids making art projects in nursery school, I might find other uses for it anyway.

This system works very well for me. It’s not perfect – occasionally my Laser printer prints traces that have small holes in them – but I can usually eliminate those by rotating the image 45 degrees before printing, or failing that, making minor repairs with a Sharpie before applying the green sealing foil.

I haven’t tried double-sided boards yet, although I plan to soon. So far I’ve just designed the circuits as single layer boards with a few manual jumpers.

There are several fancier alternatives I haven’t tried yet. One is using a desktop mill like the Roland MDX-20 or Othermill or the upcoming Carvey. I’d love to own a CNC mill someday, but for now they still cost over $2,000. Voltera recently showed off their amazing PCB printer, but I don’t think the cost or ETA have been announced yet. The best part about these options is they don’t require any etching.
If you are interested in etching at home, one tip I’ve learned is to etch quickly. When I first started with the Jameco kit, I was using GC Electronics’ ferric chloride, which is diluted with water, and then submerging the board into the etchant and rocking it for over 20 minutes. Using Pulsar’s Direct Etch method, I instead put on disposable gloves, dip a small sponge into undiluted ferric chloride from MG Chemicals, and rub the sponge against the board. This way I can etch a board in about a minute, especially if I warm up the ferric chloride first.

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