I print out a negative on acetate paper, I stick it on a copper plate with dry film, and I press it with an iron. While doing these operations, we have to be in the yellow light, what is the content of this yellow light?

 

I don’t understand your process. Is there a UV exposure involved? The yellow light would minimize UV exposure.

 

I don’t understand your process. Is there a UV exposure involved? The yellow light would minimize UV exposure.

Red light is better.

 

Copper laminate is coated with a thin layer of photo resist that is sensitive to UV light. That is why all preparation before exposure and treatment with photo resist developer must be done under UV-free light, red or yellow light.

 

If it's like the positive photoresists I've used, low wattage incandescent light is just fine, at least for the minute or so it takes to hacksaw and deburr the PCB stock or ready it for exposure. It's vastly less light-sensitive than B&W photographic paper (red or amber safe light) or film (disorienting inky blackness). Red LEDs should be fine, too.

 

thank you everyone, i found what i was looking for

 

thank you everyone, i found what i was looking for

Great. So what did you discover?
Were the replies correct and helpful in solving your puzzle?

AAC forums are not just for helpful in solving your problem.
Answers are helpful to others finding themselves in the same situation.
When the problem has been solved it is common courtesy to respond with what problem has been solved.

 

You are right, but I will try the answers given now and determine their accuracy, I will write the final result accordingly.

1. Amber light
2. incandescent light

and i found a light like this, i need to use it but i don't have it in turkey instead i will try one of the above 2 options.

 

You can put an orange or red filter over your light bulb.
Make sure that any plastic filter does not touch a hot bulb.

 

Hmmm. I expose and develop my positive boards in normal room light. And my problems tend to be under-exposure, leaving resist on rather than taking it off where it should stay.

 

Hmmm. I expose and develop my positive boards in normal room light. And my problems tend to be under-exposure, leaving resist on rather than taking it off where it should stay.

Your statement is confusing. You mean,
”leaving resist on rather than taking it off where it should stay”.

With positive resist, UV should activate the resist over areas where the resist is to be removed.

 

I think that is what I said. I am not having problems with traces being removed because of ambient light exposure. My boards tend to leave more copper than I want. So ambient light is not causing me problems. If ambient light was a problem, I would end up with too little copper after etching, no?

 

So it sounds like exposure time is too short. Have you ever done a test strip? Like this, but minutes not seconds. https://www.smoothguide-photography.com/making-a-test-strip.html

 

You can get somtjing like this... should be available anywhere.

https://www.amazon.com/iNextStation...la-832466489016&ref=&adgrpid=80210701404&th=1

 

So it sounds like exposure time is too short. Have you ever done a test strip? Like this, but minutes not seconds. https://www.smoothguide-photography.com/making-a-test-strip.html

Yes, but I think my fluorescent bulb has weakened. I did 12 min last time and it was not enough, left resist in places.

 

Yes, but I think my fluorescent bulb has weakened. I did 12 min last time and it was not enough, left resist in places.

nice

 

So it sounds like exposure time is too short. Have you ever done a test strip? Like this, but minutes not seconds. https://www.smoothguide-photography.com/making-a-test-strip.html

i didn't try, i will try amber light