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BIG mistake with etching boards

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MrDEB

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I etched 12 boards for the cub scout noise organ project, as well call it. Well all looked good EXCEPT the color of the boards changed and I thought I had etched too much. Well I didn't etch enough.
This is the one problem I have had using some thick boards I got off of Ebay several years ago.
At 5 am this morn I was using a Sharpie pen and covering all the bright copper traces then have to re etch.
Thank goodness the layout is simple.
THEN have to double check all my traces then instruct two den leaders on how to solder and hopefully get all the parts in the right places.
I like the really transparent boards. Easier to tell when you have etch enough.
Good reason to use Muratic acid/Hydrogen Peroxide mix.
The perils of homebrew pc boards
 
When I used Ferric Chloride I used a desk lamp that lit through the bottom of the plastic container. It was bright enough to show through the board when the copper was removed. It also heated up the etchant some.
 
Hi MrDEB,

I suppose you use UV-sensitive PCB material. Using different no-name products exposure time selection and development time become a PITA.

A quick check - if the board is properly developed - is dunking it in etchant for about 15 seconds and then look for glossy areas on it. Etched copper turns dull if the etchant works on it.

If there are some there is no reason to worry. Flush the board thoroughly with water and put it back into the developer. Be careful about the time for re-development and observe the board at all times. Traces start diminishing very rapidly!

When done quickly flush again and etch.

Regards

Boncuk
 
It seems a little unusual that you'd be getting 'thick' boards from e-bay. Unless they were specifically stated as being 2 ounce boards, in generaly they're gonna sell you boards with as thin a copper layer as they can get away with.

MrDeb are you using air agitation and heat in your ferric chloride bath?
 
I think by 'thick' he means the backing material, as he mentions the more transparent board material is better.
 
yes the backing material is thick. I think they are 2 ounce boards?
using muratic acid/hydrogen peroxide mix. It is cold in shop (40 degrees) may have an effect?
 
Heat is called the universal catalyst for a reason =) With very few exceptions all chemical reactions occur faster (sometimes detrimentally so) at higher temperatures. I'm asuming you meant 40degrees F, that's defintly low, You'll want it at least at 'room temperature' IE 72 degrees, and maybe a bit higher if it's convenient to heat it. Ferric chloride HAS to be heated and agitation is highly recommend. At room temperature or at your shops 40 degree temperature I'd be surprised if ferric chloride worked at all. A simple fish tank bubbler and a plastic hose with pin holes in it will provide very good agitation for any chemical bath. The smaller the holes and hence bubbles and the more of them, the better. Though keep in mind the ambient air used as agitation may cool the solution down.
 
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not using ferric cloride, using muratic acid/hydrogen peroxide mix.
QUESTION how to neutralize to dispose of safely?
 
If you don't want to deal with it see if you can find a local plating shop that will take used sollution of your hands. Waste treatement is actually more complex than the etching process. It needs to be neutralized to a PH of 9-10, and a coagulant added, ferric chloride is actually a very good for this, perhaps a little bit of clay. Not sure exactly how much but err on the side of 'just a little bit' After it's mixed at that PH For a few minutes let it sit for an hour, most of the metal and particulates in the solution should sink to the bottom. Drain off the clearer liquid on the top dilute with plenty of water (and actually only dumping it down the sewer drain right before a shower is a good idea) The rest should be used as the liquid part of a concrete mix and land filled at a hazardous waste facility. You can evaporate the leftovers down instead, but that's actually the bad stuff, just tossing that away is worse than dumping the raw solution down the drain.
 
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