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Topic: Automatic determine concentration of compound  (Read 3841 times)

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Offline zuzu

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Automatic determine concentration of compound
« on: June 19, 2009, 12:50:11 AM »
Hi friends,

Hope posting in right section. I'm not a chemist competent at all (that's why I need help) but as electronist, I use since many years ferric chloride, I guess FeCl3 is formula. Purpose is to etch cooper from my boards. We usually buy this compound from hobby store at 35% concentration. Now 2 problems I have:

1) how to measure this concentration? There are some PH sensors on market and I can easily interface, make a project with a LCD display, but I'm not sure I measure correct thing  ::) Or what sensor should I search (what parameter to measure?)

2) more complicate problem is after eatching few boards, the compound is not so strong as when bought from store and I guess it is normal, since cooper particles are now part of compound. Effect is etching boards is taking slower and slower, let's say on first board takes 10 minutes, and after 10 boards can take 1 hour. So I think to find another sensor to measure cooper concentration from ferric chloride  :o or something, this is possible?

I ask these questions because I always wanted to make myself a computerized etching tank, with temperature control (I saw over years ferric chloride etch much better at higher temperatures), some ultrasonic shaking system (cooper particles are dislocated quicker with ultrasounds) and of course, to introduce some parameters before like : board size (computer calculates cooper volume), compound quality (this is where I need sensors to measure), etc.

Hope I wasn't so boring with my project.

Any idea very appreciate,
Edi


 

Offline Borek

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Re: Automatic determine concentration of compound
« Reply #1 on: June 19, 2009, 12:57:44 PM »
pH and concentration of FeCl3 are unrelated. You need correct pH for copper etching, but pH alone is not what you need.

FeCl3 solution can be regenerated, but I don't remember details. Google should help you find regeneration procedures.

Note, that there are other etching reactants, FeCl3 is considered environment unfriendly.
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