Sunday, 9. December 2007, 09:38:43
The two things that bug me about copper circuit board etching are A> the amount of time each board takes B> the stubborn stains Ferric Chloride leaves.
I found this brilliant new method which does away with both problems.
Seven words: Cupric Chloride in Aq. Hydro Chloric Acid.
The method is very cheap, easy,fast and clean, both "stainlessly" and environmentaly.
Describing the method in brief here:
:: Ingredients ::> Hydrochloric Acid [12 Molar] (commercial concentration) This is also sold as "pool acid" and drain "cleaning acid". Its trade name is "Muratic Acid". You can find this at any hardware store. Be VERY carefull with this.
> Water Keep a bucket-full handy, incase you spill the acid on yourself or on the fruniture, wash with plenty of water.
> Hydrogen peroxide [6%] (reagent concentration) This is sold at most medical stores. You may find this in 3% concentration only, in that case do not add any water (as described in the next stage)
:: Perpatation ::Do this in a well lit ventilated place, and keep water handy. Please use rubber gloves and safety glasses.
Pour out 25ml of peroxide in a
PLASTICcontainer (Do not use metal)followed by 25 ml of acid, and step away, because the acid will fume a bit. DO NOT inhale the fumes, they cause damage to your respiratory system.
Note: if you are doing this indoors, do not handle more than 25 ml of the acid at a time, if you are donig this outdoors AND have plenty of lab/hemistry experience, you can scale the quantities as required.
After the mixture stops fuming add:
-> 50ml of water, to make a lightning fast etchant. [If you are using 3% peroxide, dont add water here]
-> 75ml to make a soft etchant [3% peroxide users, 25ml water here.]
:: The Main Part ::Pour out the etchant in a clear plastic tray, preferably kept on a white background [to observe the color of the liquid]
Right now the etchant should be clear. After a little copper dissolves, it will turn emerald green.
The green stuff is a bouns etchant! Its Copper ii Chloride! After the acid-peroxide etchant exhausts itself, the Copper ii Chloride will take over!
Over time the solution will turn muddy brown, here you can either dispose it, and start over or regenerate the copper ii chloride.
:: Regeneration ::Bubble air throught the solution to regenerate the etchant. This way, the etchant is virtually infinitely reusable.
For reaction rates and more info read this wonderfull post:
http://members.optusnet.com.au/~eseychell/PCB/etching_CuCl/index.html by Adam Seychell.
Thats all folks!
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