In next sentences I will describe what Photo Etching Process is, what material do we need and how much does it cost. I will also give my opinion about this process.
- UV lightning chamber (approximately 7 €/light bulb, we need approx. three of them. The best solution is to use old scanner box and install them).
- FR4 laminate one side coated with photosensitive lacquer positive 20 (200×300 mm approx. 14 €/pc). You can prepare it by yourself, but it’s quite complicated and nasty process (lacquer is never equally spread).
- Sodium Hydroxide Developer (NaOH 250 g approx. 3,6 €).
- Hydrochloric Acid (H2SO4 1 L approx. 3 €).
- Hydrogen Peroxide (H2O2 30% 1 L approx. 3 €).
- Acetone 1 L (approx. 4,5 €).
Total: approximately 50 €
Put foil with printed PCB layout on a FR4 laminate coated with photosensitive lacquer. Then put both together into a UV lightning chamber with PCB layout facing UV light. It’s important that print on foil is very quality and dark, that no light will go through. Someone solve this problem with two print, one over the other. In there we have to leave it for approx. 4 minutes, it depend on power of the light bulbs. Next step is to make a developing solution. How long to leave it in there? Well, if it is too long or not enough time, later we will have many problems with etching. The best to check is with your fingers. Slide with your finger at part of PCB where should not be any lacquer; if the feeling is a bit slimy then you should leave it a bit longer, if the feeling is not slippery then you are done. You can help yourself to speed up a process with a soft brush. Next step is to prepare an etching solution from one part of Hydrochloric Acid, one part of Hydrogen Peroxide and two parts of Water (1:1:2). Put developed board into solution. When we are done with etching, we just have to clean board with acetone.
My views on this process:
- It’s quite financially expensive process (FR4 coated into photosensitive lacquer is very expensive also foil for printing).
- We need developer solution that can be used only a several times, later it get saturated and the time to develop board is very long.
- First big investment is UV lightning chamber.
- Constant cost is very expensive FR4 coated with photosensitive lacquer.
- We need more bowls and we have more dirt.
Laminating process of developing PCB is my favourite and is described and presented under projects. It’s less expensive and with less dirt, it’s even easier.