This is continuing of thread of making AVR controlled signal generator. This section is devoted for 1 layer PCB prototype making using ultraviolet light exposure and etching.

The circuit isn’t very complicated, so I decided to make 1 layer PCB prototype.

I’ve chosen Eagle as PCB designing software. This is very handy software for making hobby circuits. Firs I designed circuit of AVR controlled signal generator:

AVR controlled signal generator Circuit image

When Circuit is designed, then follows PCB tracing. The resulting PCB I got is here:

Not all traces were routed. I will need to connect some places with wires, because there left some traces unrouted.

For PCB making I am using the board already covered with photosensitive layer. You may buy them in the market:

You have to peel the protective layer and expose through the mask:

Masked PCB:

After UV exposure second phase is development. I used Sodium Metasilicate as developer.

Sodium Metasilicate

This is better choice than NaOH. It is less aggressive and it is not critical to temperature or concentration. Add 50g for one liter of water. Temperature of solution should be inrange 18 - 24 degrees of Celsius. Develop about 1 - 2 minutes.

After PCB is developed, then wash with water and dry. Then put in etching solution (Ammonium Persulphate). Add about 200 - 250g for one liter of water. Temperature of etching liquid should be about 40 - 50 degrees of Celsius (instead you can use FeCl₃, but it is very messy chemical) :

After board is finished, clean the board with abrasive or developer. I use acetone as it cleans faster but stinks. Better do it outside the house.

After board is done inspect if there are any interconnections between tracks. In my case there are some because the mask wasn’t printed very well and probably there was a gap between mask and board left during exposure. The best way to do corrections is to use sharp knife or needle.

Then drill the holes and it is ok to solder.

To be continued…

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This entry was posted on Sunday, June 4th, 2006 at 10:15 pm and is filed under AVR controlled signal generator. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.