Best PCB etchant chemical ?

[picbits]

I'm currently using Ferric Chloride in a triple etching tank - a bit messy but does the job cheaply and quickly.

I've also got a small tub of Sodium Persulphate with a couple of other chemicals mixed in for good measure - I've used it before and its a lot cleaner then the FeCl but very expensive. It also has a limited shelf life after mixing but is much better for the environment on its disposal.

On an emergency callout yesterday I noticed the company using a lot of chemicals so asked the chap who does the buying if he could have a word with his supplier and get me a price on Sodium Persulphate. I can get a 25kg bag of the stuff for £50 so that makes it worthwhile.

Is a solution of Sodium Persulphate dissolved in water without any other chemicals going to cut the mustard ? I dont want to get into any exotic chemicals or mess about with acid solutions but do make 30-40 PCBs a month.

Cheers
Dom

 

[zevon8]

Sodium Persulphate is commonly used, at say 250gm per Litre water strength. I always liked it better if for no other reason than you could easily monitor the progress.

 

[3v0]

I use Sodium Persulphate from MG Chemical. I did not see anything to indicate that there are other chemicals in it.

The only other etchan I have used is Ferric Chloride and I would only use it again if I could not get/have SP for the obvious reasons.

 

[picbits]

Cool - I might have to order a sack of the stuff and decant it into airtight containers then.

£50 for 25kg is more favourable than the £23 for 1.1kg that our online electronics stores sell it for.

 

[gootee]

For me, at least, the benefits of using a home-made acid solution definitely outweigh any drawbacks.

I use two parts of the common drugstore/pharmacy/chemist-type 3% Hydrogen Peroxide and one part of the common hardware or paint store type of Muriatic Acid (28% Hydrochloric Acid).

Extremely-widespread availability and low cost are two key benefits. It's also nearly transparent (very light green), and works very quickly; about five minutes, at room temperature, with mild agitation. It can also be rejuvenated (with the need for that being indicated by the solution turning from light green to light blue), so it never needs to be disposed of (although it's so cheap that I always just make a new batch).

I typically put a little of it into a small, shallow plastic tub and wear a latex glove while gently wiping the board's surfaces with a balled-up paper towel, which also enables me to make sure that different areas finish etching at about the same time.

I've never had any problems with it, while using it in my kitchen. I'll never go back to Ferric Chloride, or even one of the persulphates.

Details are at **broken link removed** .

- Tom Gootee