Photo PCB chems

[Mark Jones]

Hi, a few quick questions please.

1. Positive photoresist aerosol is exceedingly hard to find. It looks
like lots of places carried it in the past, but now nobody does. Are
there any sources left? Liquid would also work but please, no
55-gallon drums.

2. Positive developer is commonly dilute solution of sodium hydroxide.
Will equal parts potassium hydroxide also work?

3. During exposure, it is said that faster exposure time yields better
resolution. Is this necessarily true?

Thanks.

 

[Leon Heller]

"Mark Jones" <abuse@127.0.0.1> wrote in message
news:arOdnR21P8o-DF7cRVn-tw@buckeye-express.com...

Hi, a few quick questions please.

1. Positive photoresist aerosol is exceedingly hard to find. It looks like
lots of places carried it in the past, but now nobody does. Are there any
sources left? Liquid would also work but please, no 55-gallon drums.

Electrolube makes it, but it doesn't work very well since they changed the
formula. Seno makes a liquid resist in a wipe-on applicator. That works
quite well.

2. Positive developer is commonly dilute solution of sodium hydroxide.
Will equal parts potassium hydroxide also work?

Probably, but NaOH is easier to get hold of.

3. During exposure, it is said that faster exposure time yields better
resolution. Is this necessarily true?

Can't see why.

Leon

 

[John Woodgate]

I read in sci.electronics.design that Leon Heller
<leon_heller@hotmail.com> wrote (in <41c3acb9$0$19154$cc9e4d1f@news-
text.dial.pipex.com&gt about 'Photo PCB chems', on Sat, 18 Dec 2004:

3. During exposure, it is said that faster exposure time yields better
resolution. Is this necessarily true?

Can't see why.

Vibration.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Leon Heller]

"John Woodgate" <jmw@jmwa.demon.contraspam.yuk> wrote in message
news:wv3pNSCIS9wBFwrc@jmwa.demon.co.uk...

I read in sci.electronics.design that Leon Heller
leon_heller@hotmail.com> wrote (in <41c3acb9$0$19154$cc9e4d1f@news-
text.dial.pipex.com&gt about 'Photo PCB chems', on Sat, 18 Dec 2004:
3. During exposure, it is said that faster exposure time yields better
resolution. Is this necessarily true?

Can't see why.

Vibration.

Surely the effect of vibration would be minimal, even if there was any
present. There will be virtually no relative movement between the artwork
and the PCB material, especially if a foam rubber pressure pad or vacuum is
used to keep the two in contact.

Leon

 

[Mike Harrison]

On Fri, 17 Dec 2004 21:10:42 -0500, Mark Jones <abuse@127.0.0.1> wrote:

Hi, a few quick questions please.

1. Positive photoresist aerosol is exceedingly hard to find. It looks
like lots of places carried it in the past, but now nobody does. Are
there any sources left? Liquid would also work but please, no
55-gallon drums.

Don't waste your time with it. Use precoated board.

2. Positive developer is commonly dilute solution of sodium hydroxide.
Will equal parts potassium hydroxide also work?

Use silicate based developer - MUCH less fussy about concentration and temp and almost impossible to
over-develop.

3. During exposure, it is said that faster exposure time yields better
resolution. Is this necessarily true?
Not really.

see www.electricstuff.co.uk/pcbs.html for more info on making good quality homebrew PCBs

 

[John Woodgate]

I read in sci.electronics.design that Mark Jones <abuse@127.0.0.1> wrote
(in <KeednSRmLqSjo1jcRVn-tw@buckeye-express.com&gt about 'Photo PCB
chems', on Sun, 19 Dec 2004:

I have a pound of potassium hydroxide. I'm rusty with chemistry, will
that work in place of sodium hydroxide in the silicate developer mix?
Or should I ask on sci.chemistry.

Yes, it will work. You need more of it, because potassium has heavier
atoms. Think 39/23. But you might see if you could sell it on Ebay. I
think it's quite a lot more costly than sodium hydroxide, which is an
industrial product.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

 

[Carl Ijames]

Use silicate based developer - MUCH less fussy about concentration
and temp and almost impossible to over-develop.



Hmm, interesting. Why isn't this developer more popular? It seems
perfect.

I found one source of sodium silicate solution on ebay, one pint for
$13 at http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3854567841
or even better, one gallon for $11 at
http://www.chemistrystore.com/sodium_silicate.htm

I have a pound of potassium hydroxide. I'm rusty with chemistry, will
that work in place of sodium hydroxide in the silicate developer mix?
Or should I ask on sci.chemistry.

Do you have a full recipe for sodium silicate based developer? I'm
curious about the chemistry involved. Anyway, you should be able to use
the potassium hydroxide, just use 56/40 = 1.4 times as much by weight to
get the same hydroxide concentration.

--
Regards,
Carl Ijames carl.ijames at verizon.net