For the last couple of years I've been successfully using the 'dry film process' for homebrew PCBs, the method of which I described at post 24 of this now closed thread:
https://www.vintage-radio.net/forum/...UV+PCBs&page=2
There are lots of helpful youtube videos on youtube which illustrate the process, which uses negative resist UV film. Hence, the resist of any clear parts of the artwork mask remain in place after exposure and developing, and any masked areas are washed away when developing the board, so the artwork needs to be a negative. It isn't difficult to master the technique and neither the exposure time nor the developer concentration are too critical. The UV film is very cheap and the developer is 'soda ash' which is also cheap and readily available. (Only two level teaspoons of the white powder are needed in 200ml of water).
As I'm coming to the end of the roll of UV film that I bought, I've just ordered another roll. It can be bought from UK suppliers on e-bay, or more cheaply from China. By 'cheaply' I mean a 5 Metre long 300mm wide roll for £2.85 post free! Way cheaper than pre-sensitised boards, and if a board doesn't turn out to your liking when exposed, just clean it off with acetone and apply new film. The only downside to anyone who has never used the film before, is that they may struggle to understand the 'Chinglish instructions, which are probably the most baffling example that I've seen:
Quote:
‘Photoresist for Dry Film for PCB production’
Description:
• Operating steps:
1, grinding CCL, this simple, using the finest polished clean water frosted paper on the line
2, removing film, photographic film is sandwiched between two layers of film, the first side can make use of transparent tape tear torn, try a few on the line
3, and then foil, copper clad laminates can look a little cleaner, pasted, try not to have bubbles.
4, good paste membrane used presses, not too hot, about 100 degrees from the fixing.
5, the printed circuit board film, suggestion is to use film, the fine could reach the highest degree of accuracy if you did not ask for the paper to print it with sulfuric acid trip.
6, the printed circuit on the photographic plate (Note: Dry film is negative, so to highlight the print, which we usually use photographic plate opposite) with ordinary energy-saving lamps 10 or so, if there is exposure Machine 1 minutes on the line, the sun not tried, it should be 30 seconds -60 seconds, the exposure process Obviously, since the photosensitive film will change color when exposed to light, the light becomes dark blue. You will easily see your circuit diagram appeared on the board.
7, developing and tear the protective film on the front panel, into the developer (developer according 1:100,10 gram Total 1L of water) to be used when developing a little harder stick cotton wipe board.
8, etching, this goes without saying (ferric chloride etchant environmental For protection, hydrochloric acid + hydrogen peroxide, etc.) is recommended environmental etching shop, fast, clean, no odor.
9, after a good CCL etching, stripping, from film watered by 1:60 or 70, the board bubble like a few minutes
10, after the completion of the board, very pretty good, most dense line spacing is 0.1mm, width 0.1mm, 0.1mm lines do know though is very easy to do, but do 0.1 lines and 0.1 line spacing dry film can easily do it.
End quote.
It probably all makes sense in Chinese.
All the really matters is that the UV film is great product, and at only 18 pence a square foot, experimentation won't break the bank.
Below is a recent example of a PCB that I've made using the dry film process.