Question about etching boards

[Mike]

I'm planning to get this:<p>http://circuitspecialists.com/prod.itml/icOid/4231<p>and this etching solution:<p>http://circuitspecialists.com/prod.itml/icOid/2825<p>The solution crystals are very expensive. Do they last a long time in this system? If so, how long?<p>I was also reading this:<p>http://st4.yahoo.com/lib/webtronics/410.htm<p>According to section 10, it decomposes when heated, and there is a heater in the solution. Would I be better off sticking with the nasty Ferric Chloride?<p>Finally, how is it disposed of?<p>thanks!

[jwax]

Etchants work faster at the elevated temperature, and do "load up" with dissolved copper after awhile. I haven't used the ammonium persulfate, but ferric chloride is quite cheap for the casual user. All Electronics (www.allelectronics.com) has a 1/4 lb, enough for a pint, for $4. That will etch 200 sq. inches of board. That's a lot of board!
As for the mechanical agitator, again, if you're doing a lot, it may be worthwhile, but for the casual user, sink a tray in a hot water bath (larger tray), sit and "rock" the tray for 15 minutes. Of course wear rags, use apron, gloves and safety glasses! Etch safe!

[Mike6158]

Speaking from experience, or inexperience as the case may be, I'm with jwax. I bought the "kit" with the agitator (which is nothing more than an aquarium bubbler and a holder for a piece of air tubing with holes poked in it) and I have never used it. The kit came with a simple, small lidded container and I used that etch with. I heated the ferric chloride and then poured it in the container until it just covered the boards. Like jwax said- about 15 minutes of gentle rocking and the board was done.

[Bob Scott]

Mike,<p>The first time that you accidentally spill a few drops of etchant on your clothes, you'll be glad that you bought the "expensive" ammonium persulfate instead of ferric chloride. Clothes are even more expensive. Ammonium persulfate is clear in color and does not leave stains.<p>I used a similar etching kit with the bubble etcher using ammonium persulphate about 20 years ago so. It lasts about as long as ferric chloride. I think that one gallon etched about 400-500 2.5" X 3" single sided boards coated with "one ounce copper". Two oz. copper will use etchant twice as fast.<p>Disposal is a problem these days because we have developed a greater respect for the environment. Ideally you would take any type of exhausted etchant to a hazardous waste disposal center. Don't dump it down a street drain. It'll kill the fish. If you dump it down the kitchen drain, it'll corrode trap under the sink if you don't flush with lots of water. Another idea is to make sure that it has absolutely no corroding properties left before dumping down a sewer (not a street flood drain) by first SLOWLY feeding it small pieces of aluminum until it stops reacting. Be careful. Etchant and aluminum react can violently if you drop too much aluminum in the etchant all at once. ie: frothing bubbles and heat.<p>Bob <p>

[Mike]

Thanks everybody.<p>I think I'm still going to use the heater and agitator because it speeds etching and I can do other things while it works.<p>Has anybody done this? I ask because it says the solution decomposes when heated.

[Bob Scott]

I use the kit heater with ammonium persulphate. I did not find any problems.<p>Bob <p>[ November 27, 2004: Message edited by: Bob Scott ]</p>

[Mike6158]

Just in case I'm missing something-<p>The bubbler system that I bought would require about a quart of etchant to be used ( I believe that the capacity of the container is 2 quarts) for a small board. That's why I didn't use it. I only had a pint of etchant (came with the kit) and it was premixed so dilution didn't seem like a viable alternative.<p>I only used 4 or 5 oz's to etch a couple of small boards vs at least a quart (that I didn't have anyway)...<p>If I could find a container that was about 1" or 2" wide x 12" high the bubbler system wouldn't require so much etchant...

[philba]

I've used 3 different etchants: FeCl, Ammonium Persulfate (AP) and Cupric Chloride (CuCl). I use CuCl becuase I can regenerate it and dont have to dispose it. I do not recommned this for the beginner. <p>I hate FeCl because of its nasty stains and you cant see the board (which means you have to lift it out, thus increasing the odds of a spill or drips). <p>I really like AP. It starts out clear but does turn a deep blue when used up. You can see the progress with out lifting the board out.<p>The bubbler is a very good idea and I highly recommend it. I made a very thin tank that held less than a quart (with the heater and bubbler). it worked pretty well.

[Mike6158]

What did you use for your thin tank? How did you make it? I am very interesting in what you've done. Thanks for the feedback on etchants.

[Engineer1138]

I've used an aquarium air pump bubbler with FeCl and it works really well. Even better with a heater, but I don't remember what temps I used (I'd guess around 90F or so). The problem with the bubbler is that you get a small amount of invisible fluid atomization. In my case, after a few days I noticed that my nearby Dremel drill press and other non-plated tools were getting "rusty." It took a while (I can be slow sometimes before I realized that tiny drops of ferric chloride were being sprayed into the air and corroding metal objects on the benchtop.<p>I used a deep Rubbermaid container (about 8x3x4" I think) with a thick slab of plastic glued to the inside to take up space. Because of the plastic displacing fluid, a single bottle of Radio Shack etchant was enough to fill the container. Keeping the board vertical greatly decreases etching time. It's been about 5 years since I made a PC board, but it rarely took more than 10 minutes. It etches so fast that you need to be careful with thin lines. My boards were small so I could reuse the etchant a few times.

[philba]

I made it out of "plexiglass". Initially, I used aquarium sealer but it didn't like the heat so I re-did it with a fusing cement I got from TAP http://www.tapplastics.com/shop/product.php?pid=130&<p>If you use plexiglass, make sure to get the special knife to cut it. <p>My tank is about 9"x9"x 1" (make it just wide enough to get an aquarium heater in it). I can etch 6x8" boards pretty easily. When using AP, position a light behind the tank and you can see the progress of the etch. no muss, no fuss...<p>For the bubbler, get HDPE 1/4" tubing and use an aquarium "airstone" or 2. Make a lid for the tank as the bubbling causes splashes.<p>Note that this tank will work ok for AP and FeCl but NOT for CuCl (it attacks the plastic). For that you need HDPE.<p>Phil

[Dean Huster]

I, too, made my own tank and I've used commercial ones. GC Electronics put out the better commercial tank that wasn't expensive and I accidentally bought one for a school that was a joke, made from a Rubbermaid container designed for breakfast cereal. It was awful.<p>I used two standard aquarium heaters set for maximum temperature to get the mixture warm and then one to keep it at idle. I use a bubbler at the bottom -- the good ol' aquarium tubing with holes -- and ammonium persulfate for the etchant. With fresh etchant at temperature, a board would etch in 5-10 minutes, longer as the etchant started getting used up.<p>Regarding the tank I built ...
It was 10" x 8" x 3/4" inside dimensions. That's too thin because you can't load it up with enough etchant. Otherwise, it worked OK. It was made of 1/4" plexiglass sealed with RTV (silicone sealant) and screws. Standard plexiglass cement probably would have been better, but this was 30 years ago and I had the RTV.<p>Dean

[Mike6158]

<p> <blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>I accidentally bought one for a school that was a joke, made from a Rubbermaid container designed for breakfast cereal. It was awful.<hr></blockquote><p>It's still aweful and I just bought one on purpose (but I didn't know any better). It is unused and it will likely stay that way. My first thought when I saw it? "I got hosed. Live and learn"