Home Made PCB – Etching Photo Resist Layer (Part 1)

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I’ve always wanted to make my own Arduino Prototype Shield. This shield allows the user to use a breadboard on an Arduino. It’s a very simple shield but if I were to buy it, it will cost me at least RM30. An example would be this Prototype Shield from sparkfun.com. It is sold for USD 15, which translates to approximately RM 45.

That is a colossal amount of money for something so simple. So I took the challenge to make this myself. I bought all of the tools needed for this process and if you’ve not checked it out, you might want to read this first.

I found an Eagle PCB file for this at the arduino website and I did some modifications like adding my own name on it.

Then I tried to print it out on a transparency paper but it didn’t turn out well.

It didn’t turn out well because I printed it using an inkjet printer. The ink will dry up very quickly and the printing will fade in just a matter of minutes. To do this properly I need to print it with a laser printer or any printer that uses toner, not ink. Unfortunately I don’t have such luxury so I have to get it done outside.

I print them out on a normal piece of A4 paper first and went to a photocopying shop to ask them to print it out on my transparency paper. Believe it or not most shops were not willing to print on transparency paper because they worry that it might get stuck in their machines. I finally get it done at a shop near my house and that’s the 5th shop that I tried. Thank God the owner was kind enough to try it after some persuasion.

This is the result. It’s a million times better than what my printer can do.

I printed a few examples of the same circuit on the transparency paper and I stacked two of them on top of each other to get a perfect image.

The preparation is done and now it’s time to go into a dark room for the rest of the process. When I said dark room I meant a room without any fluorescent or sun light. It is just like developing camera films the old school way. I can have a light but it must not be fluorescent, white or sunlight. Single coloured lights such as red, blue or yellow can be used. I’m using an old spotlight and it uses a traditional yellow bulb. My webcam automatically turned on its’ white balance mode and the light appears to be white but in fact it is yellow.

I opened up the PCB packaging and the PCB is covered by a blue sticker to prevent it from accidently exposed to light. This blue sticker also allows me to draw some lines to guide me when cutting the PCB to length.

The protective blue sticker layer.

Tried to be as accurate as possible but the low lighting condition doesn’t help at all.

Used a small hand saw to cut it. I did this in my room and now the floor is covered with dust. Bad choice of work area.

Sanded off the rough edges using an 80 grit sand paper. The roughest I can find. Looks pretty decent to me.

Now it’s time to peel off the protective layer (the blue sticker).

I must now stick the transparency paper on it as quickly as possible to avoid any unwanted exposure.

To properly press the transparency paper against the PCB, I used my sister’s photo frame.

Set my phone’s timer to 8 minutes to properly expose the board. I’m using a normal fluorescent lamp so that’s why it took so long. If you’re using UV light, 90 seconds is more than enough.

The waiting begins.

While waiting, I prepared the etchant for the photo resist layer. Just mixed some sodium hydroxide crystals with water. Two to three teaspoons is enough.

After 8 minutes I took out the PCB and dipped it into the etchant solution. Constantly agitated the board in the solution for around 10 minutes and the unwanted areas were washed off. Here’s the final result.

I’ll continue this in the next post. The next step will be to etch the unwanted copper areas. Stay tuned 🙂

Part 2 is up. Click here.

  1. Arun02-17-2014

    Hi nice project, I have also just got an Arduino Uno n Leonardo. Would like to make my own Shield sometime…
    May I know where you got the Presensitized PCBs…

    • Wai Hung02-17-2014

      Hi. I got them at my local electronics store. If you don’t have one nearby you can try element14.

  2. vick07-20-2013

    Hey, fluorescrent light can be used to expose the PCB right ?

    Thank you

  3. Alan06-19-2012

    Can you tell me where you got your copper clad pcb? Thanks.

  4. Gil04-06-2012

    HI I would like to know if you are able to give a link were I can download the eagle pcb file
    Thanks

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