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'[PICLIST] [OT] Reuse of Photo Resist Developer'
2001\04\06@200653 by John Waters

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Hi All,

I'm a newbie in fabricating PCB. The Photo Resist developer I'm using is
marked with "Sodium Hydroxide" on the bottle. I found that the solution
turned blue after each development, I want to know if I need to use freshly
prepared Developer every single time I develop a PCB. If I can reuse the
solution, about how long I need to replace it with new one? I saw on this
List that someone suggested putting some vegetable oil on the tracing paper
to make it more transparent, but in so doing I'll make the Developer
solution covered with oil. Does it mean that I have to use new Developer
soultion everytime, if I apply oil on the tracing paper?

Thanks in advance!

John



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2001\04\07@064036 by mike

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On Fri, 6 Apr 2001 20:06:53 -0400, you wrote:

>Hi All,
>
>I'm a newbie in fabricating PCB. The Photo Resist developer I'm using is
>marked with "Sodium Hydroxide" on the bottle. I found that the solution
>turned blue after each development, I want to know if I need to use freshly
>prepared Developer every single time I develop a PCB. If I can reuse the
>solution, about how long I need to replace it with new one? I saw on this
>List that someone suggested putting some vegetable oil on the tracing paper
>to make it more transparent, but in so doing I'll make the Developer
>solution covered with oil. Does it mean that I have to use new Developer
>soultion everytime, if I apply oil on the tracing paper?
>
>Thanks in advance!
>
>John
Don't use sodium hydroxide developer it's rather temperature
sensitive, prone to over or under develop, and made-up solution
doesn't last long. The only good thing about it is it's cheap, but
this is false economy after you've wrecked a couple of boards due to
over or underdevelopment.
Silicate based developer is WAY better - the solution lasts basically
forever - you can just top-up when it gets weak, and it has a HUGE
margin between developing and overdeveloping, i.e. you can leave the
board in for several (>10) times the normal develop time without
damage. In practice this means you can use it really strong, so boards
develop in 5-10 seconds. Once you've used this stuff you'll never go
back to hydroxide!
More info, including a silicate developer recipie, at
http://www.netcomuk.co.uk/~wwl/pcbs.html

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2001\04\11@042340 by P.J. McCauley

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You can reuse the developer but it will, as far as I know, degrade slightly
with each use until you will have to change it. As regards the oil, I used
to use isodraft to make paper transparent. It is also quite oily. I washed
the pcb after exposure in warm soapy water so as not to have oil on the
board going in to the developer. This method served me well for many years.

Joe

{Original Message removed}

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