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AVR controlled signal generator-1 layer PCB prototype

2014-12-23 18:52  
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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.

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:

image003.jpg

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:

image005.jpg

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

image007.jpgMasked PCB:image009.jpg

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.

image013.jpgAfter 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) :image015.jpgAfter 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.image017.jpg

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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