On 29/05/16 00:13, Harvey White
madyn@... [Homebrew_PCBs] wrote:
> On Sat, 28 May 2016 09:29:41 -0400, you wrote:
>
>> What about ammonium persulfate ? when I worked at the electronics plant that
>> was what we used to etch our boards. It is clear and turns blue as it etches
>> . we used to put it in a corningware baking pan and warm it with a hot plate
>> underneath . if you put more into the mix it of course eats away the copper
>> faster. In time it will take the shine off the corningware in the area where
>> the heat source was.
>
> Same kind of problem with price, I think. I could only buy it from a
> chemical supply plant, and it's rather expensive.
>
>> Have also used ferric chloride, it also works better if you warm it. Ferric
>> chloride is usually used in sewage treatment plants to coagulate the solids.
>
> Had used that for years, hard to find in good sized lots, 30
> bucks/gallon or more plus shipping.
>
> Peroxide and muriatic acid is far cheaper.
>
> If I could find a cheap source of ammonium persulphate, that would be
> nice.
>
> The stuff in the pool supply stores (Oxy-shock) is 10 bucks/kilo, and
> has trace ingredients (undisclosed). It does work, but I'm not happy
> at that price.
If you use air agitation which adds oxygen and add half a cup of HCl to the
ferric chloride every few months, the etching will last for years, which is way
cheaper than any ammonium persulfate setup. No heating above room temperature is
needed either. I started with an equal part of water with the ferric chloride
atleast 5 years ago and it still works well.
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