I’ve run into a few projects that I needed to make a custom Printed Circuit Board for doing things around the house. I did a lot of experimenting with this when I was building my own Computer Numerical Controlled (CNC) Routing Machine. (Keep an eye out in the near future for an article on my machine and possibly a series on how to build your own.)
I started my journey in learning about making my own PCB’s with absolutely no background in ever making my own so I had a lot of trial and error that I wanted to share with you all. There are a lot of articles and websites on line, however I wasn’t able to find an article that encompassed everything that I wanted to do and was geared for someone that had never done this before.
The first hurdle that I ran into was finding the supplies necessary for this project. The first and most obvious item you are going to need is a blank copper clad board. This is basically a fiberglass board with a thin layer of copper on one or both sides. For the sake of this demonstration I’m going to stick to a single sided board. There is a variety of different size boards, with different thicknesses both of the board and the layer of copper on them. On-line sources include electronic stores like Digikey and you can find good deals on copper clad board at Ebay. I’ve also been able to source small boards for testing or small projects at your local Radioshack.
Once you’ve secured sources of the copper clad the rest is fairly straightforward and can be obtained locally. Other items and the locations I found them for purchase are:
Now that we’ve got the supplies out of the way, let’s get to setting up. The most important thing here is safety. We are working with Hydrochloric Acid and this can be very dangerous if you do something stupid. One key point to remember is DO NOT use anything metal, they acid will react with any metals.
First let’s get our layout and board setup. I am not going to get into circuit board design because this goes well beyond the scope of this tutorial, however a piece of software that will greatly aid you in the process is called Eagle.
Once you get your layout setup the way you need on the computer, you want to print the tracing onto glossy photo paper using a laser printer. It is essential that this be a true laser printer that uses toner. Alternatively you can print this at home on regular paper and take it to Kinko’s or something similar and have them copy it onto photo paper. Take your printout and tape it to the blank board directly onto the copper with the printed side down. Heat your iron up as hot as it will go and with a piece of thin material (bedsheet, tshirt, or something along those lines) you want to apply firm (read: HARD) pressure with slow movement to prevent burning. This does take a while and I found from my experiences once you think its good enough, keep going another minute or two. It’s ranged for me anywhere from 5-7 minutes.
Once it is good enough, take the entire board and paper, which should now be firmly stuck to the board, and immerse it in warm water for 15-20 minutes. This will cause the adhesives in the paper to break down and you should be able to peel the paper backing layer off. Now if you let it dry after the paper backing is gone you will notice a grayish film that dries onto the copper, this needs to be removed prior to etching. Keep scrubbing, it will come off I promise. Be sure though, not too scrub so hard that the black toner comes off of the copper. I like to prep my board with two holes, one on each adjacent corner. This is used to tie a string to and suspend the board in the solution.
The basic setup that I found to work best for me is to take your plastic bin that you are going to add the solution to and get it prepped before we put the acid in. Get your air pump and tubing setup, and if you’re using the air curtain attachment hook that up to the end of the tubing. The air is important because it stirs the peroxide and acid, and although I haven’t found any proof behind this, I think the turbulence against the copper clad board helps clear the dissolved pieces off of it.
You want to lay the air stone on the bottom of the tub and run the tubing out over the top. Now, what you want to do is figure out exactly how much liquid you are going to need to fill your tub. I’m going to use 10 cups as an example. The ratio of peroxide to acid is 2:1. So for this example you are going to needs 6 1/3 cups peroxide and 3 1/3 cups acid. The other rule of thumb that I learned back in high school was that you should always add the acid to the other liquid to avoid causing a reaction. So, once we have our etching solution set up we are ready to place the board into be “etched”.
Tip: The etching solution works better at a warmer temperature so I found it works nicely if you place our “etching tub” into a larger tub with hot water in it.
Now lets get the board, with the string we tied into the holes we drilled earlier, and tie the other ends of the string to a couple pencils or something that will span across the tub across it’s short dimension. Lower the board into the solution slowly to avoid splashing. You should notice a slight greenish tint coming off into the solution. This is good, that is the copper being dissolved. Turn on your bubbles and adjust the board so that it rests over the top of the bubbles as they travel upward through the solution. This process varies in time depending on the bubbles, concentration of acid, and temperature so I cannot tell you exactly how long it’ll take, but it doesn’t hurt the process to check it every once in a while.
Once you can no longer see any copper in the sections without the black toner printing, you are done. Congratulations, you just made your first DIY Printed Circuit Board. A dish scrubbing sponge saturated in the acetone cleaner will clean up the toner nicely. Inspect your board for any breaks in the traces or areas that the traces smudge together. Breaks in the traces can be fixed by either soldering a jumper to it to bridge the break or Radioshack markets a pen that can draw directly onto the board that has a conductive ink. Tracing “smudges” can be fixed with a bit of a steady hand and an hobby knife.
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Did I miss anything? Share your experiences or any other comments you may have in the comment section below.
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