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Etching powder for home use

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lexter

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Hi!

I've started to learn home pcb manufacturing methods. And I need an opinion about the etching powder. There are two options available for me:

1. sodium persulfate
2. ferrichloride

(sorry, if names are bad, just trying to translate it from finnish to english. Please correct me if translation is wrong. Would be good to know right names.)

So, I would like to know, which one is better (if any difference), which one is less dangerous for human beings, etc ...

PS!

I'm speaking about famous "toner transfer" method, if that makes any difference. :eek:
 
Well from personal experience I can say that ferric chloride seems to have nastier fumes. I was told that sodium persulfate is a 'fume-free' chemical process, and I have never really noticed fumes while using it, unlike ferric chloride, where you can taste it in the air, especially when it's heated.

FC also stains easily, and you can't see the etching progress like you can with SP, which is transparent.

SP is more sensitive to heat and agitation - if you heat and agitate it right, it is nearly as fast as FC - but if you don't, FC is usually quite a lot faster. However, SP seems to "wear out" more quickly - I think it etches less copper per ounce of solution than FC. So, it can be more expensive.
 
I'm not sure how common plateing shops are around there but it might not hurt to make a few phone calls to see if you could find one that would dispose of your used sollution. It is small quantity, but it's still just not good to dump this stuff down the drain.
 
I have found FC the best. It is a local thing I can get at a Radio Shack (in the US). It is cheap and can be used over and over. I leave all the copper on the board I can.

I do the boards in the garage with a fan blowing over it.

And like said, do not just dump it down the drain.
 
The disposal of persulfate might be a problem? A metal finishing plant that does copper etching or treats copper bearing waste streams will gladly take ferric chloride off your hands. They usually buy it to help precipitate metals out of their system, and if they regenerate their wastes at all they'll probably end up extracting the copper and reusing it.
 
I've started using cupric chloride.
I made my own using a recipe on the web.
I made the surface mount board for my ir transmitter in the project section using it with a fine tip sharpie for etch resist.

Also I want to add these are dangerous chemicals ,so please check the information and be careful.
 
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Using sodium persulphate, I believe the used solution contains sodium sulphate + copper sulphate. Both relatively harmless chemicals environmentally speaking.

Here in Australia, I use Ammonium Persulphate. After use I just pour it (diluted) on the lawn with no adverse effects. The other way I could dispose of it would be in the pool as the copper would act as an algaecide.

Mike.
 
thanx!

Disposal is not a problem. I've already found a couple of companies, which are taking such things for free. I've bought sodium persulfate recently and it seems to be good enough, however the FC is slightly cheaper:

SP 200g = 5.53 EUR
FC 500g = 3.00 EUR (+22% tax)

But, if there is a problem with nasty fumes ... Then it is not even worse trying now, until I'll finish building my evil laboratory. :) Basically, the SP doesn't seem to give away any gases (and package says that it doesn't), so, perhaps it is the best solution by now.

As for the other chemicals, I tried to find them in local shops (mostly all over Finland) and didn't succeed. :(
 
Unless you abolutely have to use a PCB then use veroboard.
It's far easier and cheaper.
 
Thanx, mbu. Read it through and I think that I will try it. (I think that i should still have access to our university's chem. lab). But, actually, the price of 3 EUR per 500g of etching powder is not that much, however would be really interesting to make it myself.

As for the veroboards, I use them pretty often, but I'm an experimenter. And even though I hate chemistry, PCB etching is quite interesting.
 
Sceadwian said:
I'm not sure how common plateing shops are around there but it might not hurt to make a few phone calls to see if you could find one that would dispose of your used sollution. It is small quantity, but it's still just not good to dump this stuff down the drain.
Ferric chloride itself, there's actually no problem disposing of it down the drain. It's just a metal salt, table salt with rust instead of sodium. It's slightly acidic, though not enough to matter much but you're supposed to neutralize it.

However, the copper in USED ferric chloride solution is a problem. The recommended procedure is to neutralize the solution with a base which will cause the copper to precipitate out into a sludge. Then liquid is then acceptable to pour down the drain. Since you can buy sewer root killer made of copper sulfate that's intended to be poured down the drain in a much larger quantity, and copper pipes shed bits of copper anyways, one might wonder how significant this small glob is. Probably not that much. I think they're more concerned with businesses needing to dispose of tens or hundreds of gallons.
 
lexter said:
As for the veroboards, I use them pretty often, but I'm an experimenter. And even though I hate chemistry, PCB etching is quite interesting.

I gotta agree with you there. It is time consuming and a bit messy but I have enjoyed doing it on the few occasions I've had the time to bother.

BTW as far as getting rid of used ferric chloride is concerened I once poured mine in a circle on the grass behind the place I worked and the grass in that circle died and stayed dead for ages so it could be a great weed killer for use between paving slabs I was thinking.
 
Zed said:
the grass in that circle died and stayed dead for ages so it could be a great weed killer for use between paving slabs I was thinking.

Well some people say it makes plants grow better. Iron, even ferric chloride specifically, is used in many fertilizers: **broken link removed**

But etchant has some HCl in it and it may be acidic enough to kill plants.

It's beside the point though because ferric chloride is bad, bad news for staining concrete. Big reddish-brown splotches.
 
Zed said:
I gotta agree with you there. It is time consuming and a bit messy but I have enjoyed doing it on the few occasions I've had the time to bother.

Well, actually I don't have too much time now, because we've just got a second kid born a month ago, but I still really enjoy making PCBs. At our university, we've got a milling machine, which is fun, of cause, BUT! When I do it (PCB) at home it looks slightly uglier, but still! The thing that it is made without using the expensive technology and the fact that traces are smaller makes me feel really optimistic about this method.

(I've just created a PCB having 3 traces between the pads of 74LS08, which was usual plastic dip-14 package)

Zed said:
BTW as far as getting rid of used ferric chloride is concerened I once poured mine in a circle on the grass behind the place I worked and the grass in that circle died and stayed dead for ages so it could be a great weed killer for use between paving slabs I was thinking.

Well, I kinda agree that note on the package saying smth like "never flush it into the toilet" (flexible translation) is for larger quantities. But, you know, being a father of 2 small kids, who will live in this world, I'm doing my bests to keep it as clean as possible. Especially taking into account the fact that there are a couple of companies arround, which are taking those liquids for free in such a quantities.

Just imagine, if one hobbyist like me will pour his used chemicals somewhere ... well it won't be that dangerous. But what if all of us will start to forget about the fact that those liquids are dangerous ... Just imagine that there are chemistry hobbyists arround as well... what could they pour ... :(
 
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