Hi Simao,
Thanks a lot for your reply. It contains full of information. I tried phosphoric acid + ammonium per-sulfate it works fine. It didn't etch the tin plated side of the copper. The problem is ammonium per-sulfate is very slow etcher and tin becomes black. I'll try Adam's wet lamination method, I think it will reduce pressure change inside the holes.
Regards,
Volkan
--- On Fri, 1/8/10, Simao Cardoso <simaocardoso@...> wrote:
From: Simao Cardoso <simaocardoso@...>
Subject: Re: [Homebrew_PCBs] Dry film tenting problem & pattern plating
To: "Homebrew_PCBs@yahoogroups.com" <Homebrew_PCBs@yahoogroups.com>
Cc: "Simao Cardoso" <simaocardoso@...>
Date: Friday, January 8, 2010, 4:00 PM
Simao Cardoso wrote:
> I think that in 'printed circuits handbook' is written that adding
> phosphoric acid to ammonia persulfate makes it tin compatible i will
> try to check that too.
refered on this page
http://books. google.pt/ books?id= 1Pbkeu6dZ_ sC&pg=SA34- PA3
more on this page
http://books. google.pt/ books?id= 1Pbkeu6dZ_ sC&pg=SA34- PA16
the page before is also on-topic
Google is easier than the heavy book :>
To Volkan Sahin:
Trying to find a recipe got me to really old patents like 3476624 (1969)
where 2.25% phosphoric acid is added to a 25% solution of ammonium
persulfate, among a prohibited hazard etch accelerator. And later claim
that 0.5% to 15% phosphoric acid leaves the solder usable. You must know
this will leave the plated pure tin black.
While googling more 3 old patents came out 4419183 4636282 4130454, all
using Sulfuric acid, Hydrogen Peroxide (35%), Phenolsulfonic acid, not
tin compatible but tin compatible patents differ in the 5% phosphoric
acid and some not important things to a chemistry ignorant like me.
If you wish to try any off this, phosphoric acid can be bought as rust
remover, in almost anyplace where inks are sold. The one i got only says
about content 'contains solution of phosphoric acid', it's like a
yellowish gel that dries in to a white paste.
The 1L bottle of 85% phosphoric acid i got from the drug store it's less
yellowish, almost as low viscous as water. So the rust remover must have
a thicker but guessing that is something non hazard, cheap additive,
maybe it's PVP and maybe won't interfere in the etch.
But if you accept any advise from me. If you are doing this to test your
incredible good and fast UV laser raster flatbed printer. Using it with
laminated dry film, pattern plating, metallic resist plating and
metallic resist compatible etchant, won't make your machine so
incredible if you have to go trough all this. It's required if inkjet
used, but with laser direct print you should use LPI resist and CuCl
etchant and enjoy some free time and effort. And a repeatable process
for soldermak.
Can you get acrylic resin? Isn't expensive, mine was 5eur a 1L bottle. I
bought it on one supermarket (as we call those stores here) where i also
buy food, household things and so. Don't know what for people buy this
but bottle says 'used to make inks and to brighten hood floor'. The
benzophenone, ebay last item, was 260452044449, contact seller it may
still have it. He/she is listing the 50 packages off it from July at
least and only sold a few. I would bought it and oversea price given was
good, but unfortunately i asked customs if they will consider it as drug
or ask laboratory test and it went from office to office up to the
government secretary responsibly and no one know to answer. Local
chemical suppliers all ignore me. But this should be a good homebrew ink
to use in the epson print head, i passed acrylic resin with a syringe in
a hp head using those special clips and it passes like water.
I don't have a recipe from a book to make the resist but should be 5%
photoinitiator like in pva dichromated.
Recently when searching for a copper plating additives supplier i was
impressed by Atotech. (They are also in US) And don't only have the
chemicals to plating and finishings but also LPI resists soldermask and
one part legend. (Among things that make phophorizated copper anodes
and anode bags in PTH useless) With my luck with chemical suppliers i
didn't yet stop on the near by store but i hope they be better.
Good luck!
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