(snip)
It works just fine. But you might be surprised how much a quart of ferric chloride will consume, and how much gas it gives off. You can but a big box of washing soda lots cheaper than the same amount of neutralizing ability with bicarb. You can also use calcium carbonate (limestone). With either sodium bicarbonate or sodium carbonate you get salt (sodium chloride from the reaction. With limestone you get calcium chloride, the stuff that is sold to melt ice from the sidewalks.
Make that, buy a big box of washing soda...
Of course, but if I routinely dump it, and you routinely dump it, and someone else dumps their favorite stuff down the drain, sooner or later it adds up. Like you, I truly doubt that there are enough hobbiests that use ferric chloride to etch PCBs so ever make a difference in the ecology of the sewage treatment plant.
As an interesting side note, WSSC, the local water and sewer company, for a couple of years used ferric chloride as the flocculating agent for their water purification process... and surprise!! after a couple of years of doing that, the copper plumbed houses in their district started getting pinhole leaks in long horizontal sections of the copper pipe.
Imagine!
-Chuck
Yes, you already said that, and if you will notice, I wrote FeCl, not iron or copper carbonate.
-Chuck
Any municipal water treatment system I've ever heard of uses a "biological" cleaning stage using bacteria -- so it applies here as well. Yes, and it is the copper solution (the Cu++ ions) that are toxic. I don't know just how insoluble the compunds are that you create by adding soda. But if you indeed create some "mud" on the bottom of the container, with the rest of the solution not having any greenish or bluish tint, it's a good start.
robert
Cool!
Thanks! Rich
Add a little HCl to the mix and reuse!
Andrew
Chuck I read this and freaked out. This afternoon I called up the Waste Treatment plant where this stuff is headed (theres only two in the entire county one disposal and one treatment plant... its a county of about 28k people or so ...)
They handle all sorts of chemicals including the stuff used to develope pictures, etch boards, clean spills etc etc.
They were quite knowledgeable with FeCl ... at least they sounded like they were (I am not a Chemical Engineer so sue me).
And as I pointed out the mechanic KNEW what FeCl was. When I pointed out "hey be careful that stuff will eat through .." he replied "dont worry I know what it is"
To get over the guilt trip youve got me on, I am going to HUG a tree on my way home.
...
It only makes sense - they get paid for the recycled oil, they have to pay to have the other poisons disposed of.
Do better than that - if you see any litter along the way, pick it up and put it in the bin. :-)
Cheers! Rich
It should do, only it'll fizz a bit more than with washing soda.
the ocean's got plenty of iron (from rusting ships etc) and heaps of chlorine in it already, a little copper is unlikely to harm anything.
Bye. Jasen
I still like the idea of neutralizing it, just so it's not corrosive or toxic on the way down the pipe.
Plus which, it sounds kinda fun. ;-)
Cheers! Rich
I guess that's a way, but in industry, we did it a little differently. We used a thin rectangular S.S. "bucket" that was just slightly larger than the board we were coating, and dipped the board into the bucket vertically, then after removing it, we let it hang to drip dry. This was all done under yellow lights to keep from exposing the resist.
I did thousands of boards that way, and never had any coating thickness problems.
-Chuck
To apply the positive resist evenly on boards:
4, Tape your pc board tape the board using double sided masking tape to a sanding attachment. Center (balance) it well.
Lots of luck.
Harry ==================
thickness
I've used the "dip method" as a hobyist, too. Not having a made to size container usually meant finding something and pouring in more liquid resist in than I needed. When I was done, I had to decide if I wanted to risk contaminating the resist still in the bottle with that that was in the tray. For a PCB shop the answer is simple, throw it out. For for the hobyist that usually means saving it. I never had problems, but was always concerned that eventually I would get dust/lint from the air in it or have problems with viscosity since some evaporation is unavoidable.
-- James T. White
Our container was made using a bending brake, and some sheet stainless steel. You could easily make one using some pieces of plexiglass, and a little glue.
I don't recall ever actually dumping out the resist. We just kept adding more KPR to the pot. It was quite an ugly mess what with the drips drooling down the sides, turning brown and congealing. The pot had a simple cover (also bent up with the brake) that we put over its top when it wasn't in use.
For for the hobyist that
Our environment wasn't exactly clean, being as we were in an open room just off of the machine shop. I don't recall dust being much of a problem.
We used the same KPR pot to make PCB's, brass shimstock painting stencils, and ID tags for equipment.
-Chuck
Sure,
Go to
-Chuck
It is of course possible to get a nice even coating as a hobbiest, but unless one does this quite often, the effort saved by using pre-coated boards are immense. The boards from bungard also comes with a protective sheet which protects the coating from light and mechanical damage. One can saw, drill, punch, file and basically go bananas without damaging the coating. It is difficult to remove this protective sheet accidentaly, but it is quite easy to remove on purpose. Having good quality pre-coated boards also removes one more variable. When starting out it is often good to have as few as possible variables to play with. Are there any other manufacturers that provide pre-coated PCBs, which can be ordered via the internet ?
Regards Anton Erasmus
I knew a small PCB house that used to mix used FeCl with ordinary builders cement, and it did much the same.
Barry Lennox
"I'd like to add a suggestion about how to dispose of used etching solution. Before you pour it in to the sink, pour it in a plastic tank and drop there scrap of old steel nails, screws, small, nuts, bolts, etc., and let it stay for a few days. It will turn the hazardous mix of copper chloride and Ferric Chloride (FeCl3) into copper powder (sludge) that settles on the bottom and a non-etching and non-corrosive solution of FeCl2. It will save from corrosion, destruction and costly replacement in the future your cast iron drain pipes and it will save from killing bacteria in the septic tank or in sewer treatment plant. They are very sensitive to copper chloride and Ferric Chloride. A current law prohibits disposal of those chemicals in the sewer. For best yet treatment, after separation of solution of FeCl2, mix it with solution of soda (Na2CO3 used as detergent) in a flat tray lined with plastic film. It will turn FeCl2 into Fe(CO3) (insoluble rusty mud) and NaCl (harmless cooking salt). After drying outdoor whole dry rusty powder could be wrapped in plastic film and disposed of in the normal trash container." [From
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