Project from A to Z Part 2.

Published by nerdegutta in the blog Index page. Views: 1306


Making the PCB

With reference to this article:
Projects from A-Z. Part 1.

To transfer the boards graphic to a PCB, I'm using the UV method. I bought some UV-LEDs on Ebay, and made a little circuit that controls them. (On request, I will make an artice of my exposure box.) This is my exposure box:

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I print my layout on a transparent sheet, twice. The hardest part is to align the two sheets on top of each other. I to that, so the traces shall be as dark as possible:


When the sheets are aligned and taped together,it is time for the exposure. My box have a rotary switch, which can vary the exposure time. I've set it to approximately 10 minutes. That gives a pretty good result.

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Now its time to develop the board. I do that in 2 teaspoons of Caustic Soda, NaOH, in 1l room temperature fresh water. For about 15-20 seconds. USE PLASTIC GLOVES. This takes only a few seconds. I dip the board up and down, and swirl it around. After that I use a paper tissue to gently rub both sides of the board. Before all the photoresist is cleaned off, the board is kind of slippery, like its covered in thin transparent slime. The board is done, when the slippery is gone. Rinse in cold water and check that all "slime" is washed off.

Now to the etching. Luckily, my girlfriend is extremely patient with me, so she lets me turn the kitchen into an etching laboratory.

I use a plastic container filled with Sodium Persulfate, Na2S2O8, in a kettle of hot water on the stove.
The etching solution can be reused a couple of times, so when its not in use, I store it in an empty plastic bottle.

OR: My new setup with Ferric Chloride.

This is how the board looks like after etching:
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After etching, I sand the component side of the board. I do that so the paint will stick. I know theres a lot of other ways of getting color on the board, but this is my choice. I sand it with superfine paper, and paint it with a color called Emerald Green. This is a waterbased paint, so it dries very fast.

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After the board is sanded, I clean it with Acetone. To take away what I've sanded, and to remove the rest of the photoresist, so soldering will be easier. I think there's a better chemical to rinse the traces than Acetone...

Now for the drilling. I do that with my Dremel drill press.

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If the project is complex and include a lot of parts and components, I need to make a silk screen of the component side. This is done with the toner transfer method. I print the component layer in Eagle mirrored, and use my girlfriend cloth iron to transfer it. I've tried with different types of paper, but the best result comes with use of photo paper, with one glossy side.

This is what it looks like when the board is etched, painted, and drilled:

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All assembled
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This is a work in progress, changes can be made. I take no responsibilities for what others might do with this. This is for educational use only.

Check out my albums for more pictures.
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