Lighting that wont expose my board

[bitem2k]

Hi all what sort of lighting should i use, when im spraying the photoresist onto my pcb.

thanks
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[spuffock]

red or yellow or green leds, or a mixture.
a low pressure sodium lamp

 

[bitem2k]

Do you mean ultra bright or just the indicator type.

thanks

 

[spuffock]

ultra bright will be fine.
dont use white or blue,though

 

[bitem2k]

Ok thanks very much.

 

[justDIY]

what board are you using?

when I started with photo lithography, I treated the boards like photographic negatives or print media - absolute darkroom until they're in the developer ... but that's not really necessary. now I just leave the room lights on, setup the board under my fluorescents (using two 15w tubs), and switch on the tubes for 8-10 min. when its done, I just carry the board out to the kitchen for developing. The emulsion is not very sensitive. I wouldn't take it out in the sun, or park it under a high powered spot light, but it's not going to be clouded by brief exposure to normal room lighting while setting up or developing.

 

[Hero999]

Red is your safest bet.

 

[bitem2k]

Hi, i did a few test boards yesterday. I took little precaution with regards to exposure with house lights. Results seemed okish, apart from some random splatterings of copper left, and a few of my pads were a bit shite.
Quite good though for first atempt.

I exposed with sad lamp, plus 10 UV and 5 white leds. seemed to do the trick!
Im getting a strip blacklight soon, which hopefully will cut exposure time, and increase quality of boards.

One question, How do you get rid of the foul ferric chloride stuff?

thanks

 

[Sceadwian]

It's not safe to just dump it, it needs to be treated first. The easiest/cheapest way to treat it is to add caustic soda (lye) to it until the PH is between 7 and 8 and then agitate the solution for a while then let it sit. The copper will fall out of it, the sludge needs to be disposed of properly (I'm not sure of local regulations) but the liquid remainder of the sollution can be diluted and dumped down the drain after treatment. You could find a local metal finishing shop and ask them if they'd treat it for you. If it's a small quantity they should be glad to get rid of it for you.

 

[spuffock]

I have seen packs of a powder which believe to be a mixture of plaster of paris and lime. You pour the muck in and it sets to a solid lump which goes in the landfill.
Try ammonium persulphate, you'll never want ferric bloody chloride again.

 

[bitem2k]

Ok thanks very much.