huehnerhose
Hello,
I’ve got a question that isn’t directly related to photography. I need to etch a circuit board soon. And to do that, I need to perform exposure of the layout onto the board somehow. As I’m quite new to the whole subject, I thought that instead of printing it onto film, which is a common method provided you have a good printer, I could print it onto paper and then perform contact exposure on the printing film. For the PCB exposure (UV), the template then needs to be placed in contact with the board again. The template should be completely UV-opaque in the black areas.
So my question is: are the black areas UV-opaque? I seem to recall reading somewhere that you need to use ‘staining’ developers for this?
And a second question: can I get ‘useful’ contact copying using ordinary paper? I had thought that it would be sufficient if the areas to be exposed on the printing film were only ‘lightly’ exposed, so that ‘normal’ development would produce only a grey tone. Since I only need black and white, I thought you could simply push the film until it’s really black. That should be possible, depending on visibility.
Oh, and: It’s important to have fairly high acutance. The lines are 0.01 inches wide; the maximum I could manage would be 0.02 inches.
Regards
Sebastian
Richard
Hi Sebastian,
Well, I don’t want to put a damper on your experiments or take business away from Mirko’s print film sales. But do you really think you’ll achieve success quickly this way? What sort of template do you have to work with?
Did you design it yourself using a circuit diagram editor?
- using a good printer on film
- if that’s not available, then at a copy shop
- or find an exposure studio; that’s not too expensive either
Circuit diagram on paper?
- a good photocopier on film
You need a positive for exposing the PCB. With the printing film, you’ll start with a negative, then contact print it and...
I’ve done this with inkjet printing onto film and laser printing onto film; both worked. Overexposure of the board is a nightmare... How many boards do you want to make? What do you plan to use for etching? Might a PCB service be an alternative?
Best regards
Richard
huehnerhose
Hi Richard,
I just want to make a single circuit board for now. And it’ll probably stay at just this one. My whole problem is that I don’t have a decent laser printer. I hadn’t thought of using a copy shop at all – thanks, I suppose that’ll be the way to go.
I’m designing the layout in Eagle, so yes, I’m doing it myself.
If I print a negative and re-contact it, I’d have the positive I need – surely it shouldn’t matter which way round I print it inverted? I’ve got an inkjet printer here that produces quite good results. I just thought I’d have to buy transparencies for the printer, and since I’ve got my photo chemicals to hand and the printing film will surely come in handy in the long run (at the latest in my one old large-format camera), it would be a ‘cheaper’ investment.
I wanted to etch using ferric chloride. My mate, with whom I’m working on the whole project, still has some plates left. So even with several attempts, it would work out much cheaper than 40
Wolf_XL
...so if it really is just a circuit board, I’d go the good old-fashioned way and draw the whole thing on tracing paper using old-school tools like tracing paper and ink pens – job done. I’ve produced about three hundred circuit board templates this way – so it’s a tried-and-tested method... ;-)
Then there was also this transfer film at one point, which you could use to copy circuit board templates onto a sheet of film. I’ve no idea, though, whether that stuff is still available.
Another alternative would be to use lith film – you’d just have to create a positive first via contact printing and then the negative with another form of contact copying. The effort is only worth it, though, if the template is used frequently or to produce several templates for a small batch.
Richard
Hi Sebastian,
And remember to print it upside down. The printed side goes on the circuit board; that prevents any unsightly marks.
Best regards,
Richard
huehnerhose
Thanks for the tips and feedback on my ideas!
Now I just need to finalise the layout and give it a final check, then we’re good to go :)
Best wishes
Sebastian
Renate
Hello,
I once copied a circuit board from a paper printout onto film. In principle, it worked. However, the tracks are noticeably out of focus and slightly frayed. This doesn’t work with fine tracks. The film itself is perfectly UV-resistant. However, I printed it as a positive and then copied it as a negative and a positive. That makes retouching easier.
The process of making a reproduction of the paper template onto document film, developing it as a hard copy and then making a copy of that onto printing film was quite practical. However, if the tracks are too fine and the circuit board is too large, a 35mm camera may be overwhelmed.
The results from copy shops are hardly usable, and the inkjet printer isn’t exactly brilliant either, though it can work. The laser printers in my area are also useless for printing circuit boards onto film.
Best regards
Renate
Richard
Hello Renate,
That surprises me, even now. I’ve managed to get decent results on Bungard material myself using a laser printer with a drum unit that was starting to fail. OK, in that particular case, I did have to touch up the solid areas with a foil marker. Incidentally, the idea about the copy shop came from a print shop. After all, plate making for the offset press is very similar to the photopositive process used for circuit boards (photopositive exposed with UV light).
But if (assuming a computerised template) the printout isn’t good enough, then copying it again won’t make it any better. In that case, direct film exposure at a repro shop is the method of choice.
As I said, I’ve only really had problems with templates from a laser printer once (and the machine was actually faulty at the time). Well, laser printers do have one problem: those beasts tend to produce low density in large areas. But you can work around this problem.
Best regards from Impexhausen, which is sinking in snow :)
Richard
