Jameco Tech Post: Environmentally Friendly PC Board Etchant

[Hank The Curmudgeon]

For those of you that etch your own PC boards I got this today via a Jameco Electronics email blast. Have not tried it. Sounds interesting.

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Eco Friendly Etchant
I thought I would share my experiences with creating quality circuit boards using an eco-friendly etchant. The basic goal I set out to achieve when I started was to create a factory quality; double-sided circuit board without using the environmentally unfriendly ferric chloride. After many years of research I learned that a basic pool chemical combined with simple over-the-counter hydrogen peroxide creates one of the best eco-friendly etchants.

I set out to create an eco-friendly etchant that by my calculation would be roughly 8 times cheaper than ferric chloride. I used two common household chemicals: muriatic acid (pool chemical) and hydrogen peroxide. Anytime you decide to mix chemicals, it's a good idea to wear protective gear like gloves and goggles.

Mixing your own etchant is not without its hassle factor, but the wonderful part is that this etchant can be easily mixed on the fly in a measuring cup and only requires a 3 oz mixture to etch a 1" x 1" board in one minute at room temperature. I know that may sound unbelievable, but simply mixing 1 oz of muriatic acid with 2 oz of over-the-counter hydrogen peroxide yields one of the most economical etchants one can ever find.

Supplies:

      1. 16 oz 3% Hydrogen Peroxide
      2. 32 oz 31.45% Muriatic Acid (available from pool supply or hardware store)
      3. 150ml measuring cup
      4. Plastic TableSpoon

Recipe for an eco-friendly etchant:

Wearing gloves and goggles, simply pour 50ml of Hydrogen peroxide (3%) in your 150ml measuring cup then add 25ml of Muriatic Acid (31.45% Hydrogen Chloride). Stir this mixture with a plastic spoon for a few seconds. Remember never to add the peroxide to the acid. Instead make sure you add the acid to the peroxide.

Through trial and error I have successfully timed and etched .5 oz copper clad boards (double and single sided) without an etching tank or heater in less than 2 minutes. Boards smaller than 2" x 2" can take considerably less time.

I don't recommend you make an extra supply and store it, because the moment these two chemicals combine, a reaction starts which slowly neutralizes the solution. Happy etching, and thanks for thinking about the environment.

John Macklin
Wichita, Kansas

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Hank The Curmudgeon
- Inventor And Builder of Obscure Things, Odd Mechanisms and Curious Objects
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