positiv20

[Ahmad_tbp]

hi ..
i m tryin to use positiv20 spray to make pcbs at home , can i use regular fluorescent lamps to expose the pcb ?

[Eva]

The kind of light that is required is UV-A (don't mistake with the harmful UV-C type used to erase EPROMS). Normal fluorescent lamps produce it but only in very small quantities. Altough you may get UV-A light from various sources, like high power halogen lamps, the sun, etc..., the easiest solution is to get "actinic" fluorescent lamps. They are commonly used in fish tanks and their light has a white-bluish distinctive colour. Note that UV-A is not particularly harmful, altough I wouldn't stare at such a lamp if I was you.

[Ahmad_tbp]

so if i wanna use regular fluorescent lamps i should take so much more time ... i couldn t find a cheap uv lamp here , they r so expensive , better use fluorescent , or may go for halogen lamps thnx anyway man

[ilimzn]

You can use regular fluorescent, in fact it takes a shorter time than one owuld expect - perhaps some 10-15 minutes through 3mm glass (used to flatten the transparency ono the board), depends on how thick the layer of Positiv 20 is.
If you can find already presensitized boards, use them instead, Positiv 20 is very finicky, in particular it is very difficult to find a completely dust-free environment to apply it.

[Ahmad_tbp]

i don think i can find any presensitized boards , wat do u suggest to make an easy clean coated board ?

[clem_o]

Originally posted by ilimzn
If you can find already presensitized boards, use them instead, Positiv 20 is very finicky, in particular it is very difficult to find a completely dust-free environment to apply it.

Ditto - I had a can of that stuff and never got it to work satisfactorily. It's difficult to get an even, thin layer on. And, maybe it was a mistake, but I was always spraying it on in very low light, but couldn't figure out how else to not expose it to UV...

Cheers!

[quasi]

I keep my positive 20 in the fridge (refrigerator), this stops it drying too quickly when sprayed, helping it spread more evenly on the blank PCB.

Then I expose it using a 500 watt halogen (with the protective glass removed) for 20 minutes. Look at http://www.diyaudio.com/forums/showt...88#post828688.

I get perfect results every time. Indeed it's been years since I've had a anything but.

Cheers

[Ahmad_tbp]

hi quasi , how r u man ?
thnx for reply , i m keepin my positiv20 spray in fridge too , i m startin to build a light box w fluorescent lamps .. and my first board will be ur mosfet amp quasi ...
i ordered the board to a local store in area , but wat happend ??? it never opened again , after i ordered the mosfet amp board !