photoresist

Im getting ready to do my first photoresist board. I have a couple questions first:

Do I have to dilute the developer solution?

Should I brush off the photoresist when its in the developer?

Im going to be working on this in my garage where Ill have all the lights off. Of course I need light so I was thinking of getting a 1W red LED and mounting it on my ceiling. Will this be alright for not exposing the baord?

No, you do not have to dilute the solution and no brushing is required. You will see the photoresist simply dissolve away. Just use enough developer to just cover the board.
And, for DIY PCBs, there is no need to go to the extents of working in a dark room. Just don't place the board under intense light sources for extended period.

The photoresists I know are only sensitive to high energy wavelengths- primarily UV. That's present in black lights, sunlight, and most halogen lighting. Content in std florescents and non-halogen bulbs is fairly small.

And realistically as checkmate mentions it's not that sensitive. If you don't put it under a desk lamp or use in a really bright room these low uv sources have little chance of affecting the resist. Just keep the sunlight and halogen bulbs far away. We don't conciously perceive the magnitude of sunlight versus room light- sunlight is many thousands of time the power and a room lit by a window may be hundreds of times brighter than one lit by a bulb. That on top of the UV content is something it is wise to understand.

Thanks guys.

One more question: After I use the developer, can I just dump it back in the bottle like can be done with ferric chloride?

some people say that you can dump it back in the bottle, but the solution never worked again for me.

Well actually the solution I use is so cheap its not worth wasting space to store it. I use sodium hydroxide.

It goes something like 1 teaspoon of 100% strength to 750ml of water ( 1 pint roughly). And keep the solution at room temperature.

Ok so DONT pour it back into the container, store it in a different container, but use it again on your next board if it doesn't work then throw it out.

These boards that come out of this can be very high quality!!!

goodluck

EDIT: sodium hydroxide powder is basically drain cleaner (unblocker)

zachtheterrible said:

Do I have to dilute the developer solution?

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That depends on the strength of the solution you have. Follow the instructions from the mfg for best results. If you have developer which is meant to be diluted and you don't dilute it, you might just see all the photoresist on your board dissolve before your eyes.

zachtheterrible said:

Should I brush off the photoresist when its in the developer?

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Like checkmate says, just let the exposed resist dissolve on its own, don't brush it.

zachtheterrible said:

Im going to be working on this in my garage where Ill have all the lights off.

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I'm never that careful. I leave the lights on, (regular bulbs) and I've never had a problem. The photoresist is nowhere near as sensitive as photographic film. When I first started doing photo-boards, I would set up the whole darkroom thing -- safelight, darkroom, etc. Found that it wasn't necessary for me to go to all that trouble to get good results. I even used to coat my own FR4 with resist from an aerosol can, but GC stopped selling it. (Plus, it was $30 USD+ per spray-paint size can, which would always run out of pressure before all the resist was used out of the can.)

You will probably have to do some experimenting to determine what works best for you -- bulb distance, exposure time, developing time, etc. I don't want to sound negative, but I wouldn't expect perfect results the first time. But, once you figure out your process and you get some super good results, you'll wonder why you didn't do it this way from the start.
JB

Im getting ready to do my first photoresist board.

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So you decide to no longer draw your circuits on the board eh? (or whatever crude method u did before) :lol:

Do I have to dilute the developer solution?

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Depends on timing. If you want the developing process to take about 10 seconds, you don't need to dilute the developer solution, BUT if you don't take out the board immediately, your circuit image will begin to disappear.

Personally, I go with 5 parts of water to 1 part solution, and it takes about 2 minutes to do the developing.

Should I brush off the photoresist when its in the developer?

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I dunk my circuit in the liquid and move it around. Brushing it may work, but don't brush it too hard. and dont brush it if you use full strength solution or you will brush the image off as well.

Im going to be working on this in my garage where Ill have all the lights off. Of course I need light so I was thinking of getting a 1W red LED and mounting it on my ceiling. Will this be alright for not exposing the baord?

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any normal light is good for non-exposure purposes. A halogen bulb turned on and next to the circuit is a good exposure source. Make sure you put glass on top of your circuit when exposing it.

Well I just tried my first board with bad results. When I put it in the ferric chloride all of the copper came off. I probably heavily overexposed it because I let it set in direct sunlight for 5 minutes, and the laser printer that I used is almost out of toner so a lot of sun probably got through.

I diluted my developer 10:1, as it said on the directions.

Ill try a halogen bulb this time. I think that my roomlight is a halogen.

So you decide to no longer draw your circuits on the board eh? (or whatever crude method u did before) Laughing

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CRUDE!?!?! lemme tell you something about crude!! dipping your board in candle wax and then scraping away the wax is crude!!
You're just getting back at me for telling you that your way was crude when you decided to switch to phototransfer. Im sure i can find the post for you :lol: :wink:

By the way, I was using the toner transfer method which isn't crude at all. Just got sick of the less than impressive results.

YES!! IT WORKED!!

I used my halogen room light as an exposure source for 3 1/2 minutes. I removed the UV filter off of it.

I only had one problem: The tracks have small lines in them. Maybe its because the transparency that I made wasn't dark enough due to a almost empty toner cartridge.

My only question is this: Where to find cheap photosensitive boards? Or where to find cheap photosensitive spray? I'd rather go with the boards though. Ive looked on ebay and couldnt find any.