Homebrew PCBs

Hi,

I'm from Colombia, excuse my English.
I always wanted to know the formula of "fotorresist" or something similar to make PCBs. 
Does anyone know this?

Here's an example:

1. Silver nitrate .......... 25%
2. Silver Clouro .......... 25%
3. polyvinylpyrrolidone K30 .....0.54% 
4.  sodium carboxymethylcellulose..... 0.9%
5. Distilled Water  .............48.6%

... or anyone knows of a different formula and easily?, if it is possible that "revelator" can use.
 some of these chemicals are not available where I live!

Thanks!


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--- In Homebrew_PCBs@yahoogroups.com, Alberto Colorado <albertocoloradoaxl@...> wrote:
>
> 
> Hi,
> 
> I'm from Colombia, excuse my English.
> I always wanted to know the formula of "fotorresist" or something similar to make PCBs. 
> Does anyone know this?
> 
> Here's an example:
> 
> 1. Silver nitrate .......... 25%
> 2. Silver Clouro .......... 25%
> 3. polyvinylpyrrolidone K30 .....0.54% 
> 4.  sodium carboxymethylcellulose..... 0.9%
> 5. Distilled Water  .............48.6%
> 
> ... or anyone knows of a different formula and easily?, if it is possible that "revelator" can use.
>  some of these chemicals are not available where I live!
> 
> Thanks!
> 
> 
> 



It's hard enough to make the commercial stuff work, I wouldn't even consider trying to make the resist myself. Just buy a can of the stuff, or better yet, buy pre-coated boards. If you cannot buy it locally you can order it online.

On Sat, 06 Mar 2010 00:28:40 -0000
"James" <jamesrsweet@...> wrote:

> > 1. Silver nitrate .......... 25%
> > 2. Silver Clouro .......... 25%

I'm no chemist, but this sounds very much as a photographic layer, not a
photoresist. 

I've read - many years ago - that most photoresist layers are made with
albumine plus several other products to stabilize, sensitize and improve
contrast. A quick search for 'photoresist albumine' popped up several
patents with info on resists.

John

Alberto Colorado wrote: 
> I always wanted to know the formula of "fotorresist" or something
> similar to make PCBs. 


Curiosity can be a great thing but in this case practical results are
only for chemists, or people with number of equivalent readings as a
chemistry degree. (and access to a wide range of chemicals)

One short/light introduction to various types of photoresists can be
read on (page 4 and forward)
http://www.htp.ch/lib/pdf/Liquid%20resist%20for%20PCM.pdf

Your example don't seem to be from any known/working photoresist. But if
it would work will be a positive acting one. Negative acting
photoresists are preferred. Dry film is the most used type and not
liquid photoimaginable resists (LPI). 
Riston from Dupont and Dynachem's Laminar were the first dry films on
the market. The biggest supplier actually is Eternal Chemical Company
(Taiwan) who bought Shipley Company dryfilm business.
Start points for your curiosity:
US3469982 PROCESS FOR MAKING PHOTORESISTS (first dupont dryfilm patent)
US4295948 Photocurable adhesive from acrylic acid, acrylamide,
dimethylaminoethyl methacrylate, benzophenone and methyl ethyl ketone
(some other dry film example)
http://atlas.cc.itu.edu.tr/~yusuf/PDF/288.pdf (see how related chemistry
looks) 
http://books.google.pt/books?id=A-TC5tGGBz8C&pg=PA151 (dry film history
or something like it, and lots of related examples in previous chapters)

If you wish to coat your own boards with positive acting resist the
easiest to buy is Diazo naphto quinone (DNQ) type, is the thing you can
get for serigraph screens locally or from eBay, its priced at about
30eur for base, sensitizer and remover here. But don't know if anyone
tried it on pcb. This Brazilians uses a similar thing:
http://www.inape.org.br/circuito.html
http://eletronicaoob.blogspot.com/2010/02/tutorial-criando-pcb-facil-e-com-alta.html ( se Portugu�s n�o for um problema para ti ).

But just buy the thing. There is so much in the evolution history of dry
film. Going from 50% benzophenone and MMA solvent working dryfilm to <5%
benzophenone and very specific acrylates semi-aqueous working dry film
of todays. And LPI aqueous resists are a really evolute product. I am
sure you won't be able to mix anything similar.


Saludos
Sim�o

Oh! Man, that was great! Thank you.
I served the first file. That was all I needed but any suggestion is welcome.
Thanks again!



--- El vie 5-mar-10, Simao Cardoso <simaocardoso@...> escribió:

De: Simao Cardoso <simaocardoso@...>
Asunto: Re: [Homebrew_PCBs] Fotoresist
Para: Homebrew_PCBs@yahoogroups.com
Fecha: viernes, 5 de marzo de 2010, 20:43

Alberto Colorado wrote: 
> I always wanted to know the formula of "fotorresist" or something
> similar to make PCBs. 


Curiosity can be a great thing but in this case practical results are
only for chemists, or people with number of equivalent readings as a
chemistry degree. (and access to a wide range of chemicals)

One short/light introduction to various types of photoresists can be
read on (page 4 and forward)
http://www.htp.ch/lib/pdf/Liquid%20resist%20for%20PCM.pdf

Your example don't seem to be from any known/working photoresist. But if
it would work will be a positive acting one. Negative acting
photoresists are preferred. Dry film is the most used type and not
liquid photoimaginable resists (LPI). 
Riston from Dupont and Dynachem's Laminar were the first dry films on
the market. The biggest supplier actually is Eternal Chemical Company
(Taiwan) who bought Shipley Company dryfilm business.
Start points for your curiosity:
US3469982 PROCESS FOR MAKING PHOTORESISTS (first dupont dryfilm patent)
US4295948 Photocurable adhesive from acrylic acid, acrylamide,
dimethylaminoethyl methacrylate, benzophenone and methyl ethyl ketone
(some other dry film example)
http://atlas.cc.itu.edu.tr/~yusuf/PDF/288.pdf (see how related chemistry
looks) 
http://books.google.pt/books?id=A-TC5tGGBz8C&pg=PA151 (dry film history
or something like it, and lots of related examples in previous chapters)

If you wish to coat your own boards with positive acting resist the
easiest to buy is Diazo naphto quinone (DNQ) type, is the thing you can
get for serigraph screens locally or from eBay, its priced at about
30eur for base, sensitizer and remover here. But don't know if anyone
tried it on pcb. This Brazilians uses a similar thing:
http://www.inape.org.br/circuito.html
http://eletronicaoob.blogspot.com/2010/02/tutorial-criando-pcb-facil-e-com-alta.html ( se Português não for um problema para ti ).

But just buy the thing. There is so much in the evolution history of dry
film. Going from 50% benzophenone and MMA solvent working dryfilm to <5%
benzophenone and very specific acrylates semi-aqueous working dry film
of todays. And LPI aqueous resists are a really evolute product. I am
sure you won't be able to mix anything similar.


Saludos
Simão




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