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PCB Photoresist Chemical

A

Animesh Maurya

Jan 1, 1970
0
Hi everybody,

Sorry, although this is not anyhow related with electronics,
but I think you people can me.

Can anybody exactly mention which chemical is used to photoresist PCB.

Thank you,

Animesh Maurya
 
R

Robert Baer

Jan 1, 1970
0
Animesh said:
Hi everybody,

Sorry, although this is not anyhow related with electronics,
but I think you people can me.

Can anybody exactly mention which chemical is used to photoresist PCB.

Thank you,

Animesh Maurya

In the "good old daze" of hand-layouts ("taping"), Kodak Photo Resist
(KPR) was commonly used, along with KMER.
However, an el-cheapo way is to use egg-white sensitized with
Potassiun DiChromate.
Exposure to UV in either case polymerized the material, allowing the
solvent to wash away the un-exposed material.
For the sensitized egg-white, warm water is the developer, and one can
do some careful baking to achieve a more robust covering.
Be careful with that chemical; water becomes more corrosive as the
purity increases (no joke).
Ordinary water is bad enough on mountains!
 
J

John Woodgate

Jan 1, 1970
0
I read in sci.electronics.design that Robert Baer
water becomes more corrosive as the
purity increases (no joke).

When do you collect your Nobel Prize for that discovery? (;-)
 
A

Adam S.

Jan 1, 1970
0
Robert said:
Be careful with that chemical; water becomes more corrosive as the
purity increases (no joke).

Corrosive to what ?, sodium metal?
 
L

Leon Heller

Jan 1, 1970
0
Adam said:
Corrosive to what ?, sodium metal?

Lead springs to mind - lead pipes are more dangerous with soft water.

Leon
 
C

cpemma

Jan 1, 1970
0
Leon Heller said:
Lead springs to mind - lead pipes are more dangerous with soft water.

But traces of chloride ion make water much more corrosive on damn near every
other metal.
 
J

John Woodgate

Jan 1, 1970
0
But traces of chloride ion make water much more corrosive on damn near every
other metal.
Well, this is one of those Usenet 'true, but...' things. Lead chloride
is soluble in water, so traces of lead chloride get into water that is
virtually free of carbonate ions - 'soft' water. 'Hard' water, with
carbonate, forms an insoluble coating on the inside of lead pipes - you
can see a sort of fawn coloration.
 
M

Mark Zenier

Jan 1, 1970
0
Hi everybody,

Sorry, although this is not anyhow related with electronics,
but I think you people can me.

Can anybody exactly mention which chemical is used to photoresist PCB.

Last I checked, the dominant resist is a dry film that is heat
laminated on the board. Dupont "Riston", or something
like that. Maybe there's a MSDS (chemical safety form) on the
web for it that would tell the active ingredients.

There are a zillion types of photoresist, etchant, and plating
solutions. Try Coomb's "Printed Circuits Handbook".

Mark Zenier [email protected] Washington State resident
 
R

Robert Baer

Jan 1, 1970
0
Adam S. said:
Corrosive to what ?, sodium metal?

*EVERYTHING*
Plastics, glasses, metals, minerals, other liquids and gasses,
anything - except nothing (ie a vacuum).
Water is a *polar* molecule and that dipole moment is not exactly weak
in the chemical scheme of things.
If you get into serious work requiring pure water measured in the
megohms, you will find that the purest available water does not last
very long - as it dissolves the container and becomes less pure,
eventually becoming in equlibrium with the container material.
 
G

Glenn Ashmore

Jan 1, 1970
0
They don't call it the "universal Solvent" for nothing.

Robert said:
*EVERYTHING*
Plastics, glasses, metals, minerals, other liquids and gasses,
anything - except nothing (ie a vacuum).
Water is a *polar* molecule and that dipole moment is not exactly weak
in the chemical scheme of things.
If you get into serious work requiring pure water measured in the
megohms, you will find that the purest available water does not last
very long - as it dissolves the container and becomes less pure,
eventually becoming in equlibrium with the container material.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com
 
P

petrus bitbyter

Jan 1, 1970
0
Robert Baer said:
*EVERYTHING*
Plastics, glasses, metals, minerals, other liquids and gasses,
anything - except nothing (ie a vacuum).
Water is a *polar* molecule and that dipole moment is not exactly weak
in the chemical scheme of things.
If you get into serious work requiring pure water measured in the
megohms, you will find that the purest available water does not last
very long - as it dissolves the container and becomes less pure,
eventually becoming in equlibrium with the container material.

Pity you can't train them to solve PCB-copper only.

petrus
 
S

Sam B.

Jan 1, 1970
0
If you are looking for photo-resist, Think and Tinker has some dry
film. I've used it and it works very well down to 5mil traces, if
you know what you are doing.

Sam
 
A

Animesh Maurya

Jan 1, 1970
0
Robert Baer said:
In the "good old daze" of hand-layouts ("taping"), Kodak Photo Resist
(KPR) was commonly used, along with KMER.
However, an el-cheapo way is to use egg-white sensitized with
Potassiun DiChromate.
Exposure to UV in either case polymerized the material, allowing the
solvent to wash away the un-exposed material.
For the sensitized egg-white, warm water is the developer, and one can
do some careful baking to achieve a more robust covering.
Be careful with that chemical; water becomes more corrosive as the
purity increases (no joke).
Ordinary water is bad enough on mountains!

Thanks, Robert for the info.

In addition to KPR, I would also like to try out egg-white one.

Can you please put detailed preparation of it. What should be the
ratio of egg-white and Potassium Dichromate?

Thanks again,

Animesh Maurya
 
R

Robert Baer

Jan 1, 1970
0
Animesh said:
Thanks, Robert for the info.

In addition to KPR, I would also like to try out egg-white one.

Can you please put detailed preparation of it. What should be the
ratio of egg-white and Potassium Dichromate?

Thanks again,

Animesh Maurya

Cannot say, i only heard about that, and seen an equivalent using a
variant of Elmer's glue.
I do not think you need very much, as potassium dichromate is a rather
powerful oxidizer.
Try adding just enough to get a pink mixture.
Powedered egg-white is easily available and seems a lot less expensive
than using whole eggs for the source.
 
R

Robert Baer

Jan 1, 1970
0
Mark said:
Last I checked, the dominant resist is a dry film that is heat
laminated on the board. Dupont "Riston", or something
like that. Maybe there's a MSDS (chemical safety form) on the
web for it that would tell the active ingredients.

There are a zillion types of photoresist, etchant, and plating
solutions. Try Coomb's "Printed Circuits Handbook".

Mark Zenier [email protected] Washington State resident

Riston has been a commonly used resist for ages.
 
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