Static Electricity and Ferric Chloride (argh!)

Sorry for your troubles. I was once using ferric chloride with the GC "Professional Etching Kit" (before they started including an O-ring to keep the heater from contacting the plastic tank). Combination of circumstances, the heater was touching the wall of the tank when I plugged it in to warm up and melted through just as the solution was reaching temperature. I was in another part of the plant.

By the time I came back to check if the etchant was up to temp most of the contents of the tank had poured out on the floor and had seeped into many different places in the lab. No fun to clean.

Oh, well. DIY etching is a lot of trouble. And always use the included O-ring. ;-)

Cheers Chris

Besides heat, the other thing you might want to check is to make sure that your ferric chloride is not too concentrated. Yes, you read that right: Believe it or not, above a certain concentration etching slows down to a near-standstill. You not only need to attend to this when you buy new etchant (which is sometimes supplied at too-high concentration), but also as it ages. You'll need to ask a chemist for the explanation... it's something to do with site competition (or something equally unintuitive). But in the lab where I used to work, it was standard practice when the etchant started to slow down (after some number of boards were etched), to dilute it a little to bring it back up to speed. I wouldn't have thought that usage would have provoked a concentration increase, though it might have been due to evaporation.

If you want the details on the proper concentration, see

Best regards,

Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis

Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!

Nasty old stuff that. Lately most the of the things I've been doing seem to revolve around the cooker in the kitchen. From using the oven at 250oC for SMD components, to using a saucepan on the stove with a sealable sandwich box floating in a pan of water. That's where the etching gets done. All very technical and high tech.

A sandwich box I've found is the most brilliant thing for etching, and at

50p each in the local supermarket too. Just stick it in a saucepan of hot water. As for storing unused ferric cloride I use an airtight coffee jar (glass being non reactive) stored under the sink in the dark.

I once tipped my mixed solution down a stainless steel sink.... Don't do that.

All experience and memorable though. :-)

upset right now, so please consider that when reading. If

GAWWWWWWD!!!!, Does you mom know you're doing that in her kitchen?

If you ever go to using Ammonium Persulfate etchant, then don't put it in an airtight container. I learnt that the hard way. It makes some kind of gas and my bottle exploded unexpectedly, distributing etchant all over the place.

Chris

I etched a board with I think RS FeCL3; after I did the board, I dumped about a pint of the stuff down the storm drain.

I wonder if I killed any fish? (this was about 5 miles from the ocean).

Thanks, Rich

I ended up getting a 2.2gallon fish tank from petsmart and used an aquarium heater and aerator for the tank. I also drilled a hole in the bottom of the tank (it's a cheap tank, all plastic) and have a pump hooked up to pump the solution into a holding tank(only when using ferric Chloride) there is a valve on the bottom of the tank which allows me to drain the solution after os many uses but it helps being able to use the pump to both empty and fill the etching tank :P Don't use Ammonium Persulphate though in that setup unless your gonna drain teh tank after each use, that stuff doesn't keep very well.

snipped-for-privacy@daqarta.com (Bob Masta) wrote in news: snipped-for-privacy@news.sysmatrix.net:

I read that somewhere. You may have posted it yourself on Usenet previously. The Google Searches turned up quite a bit of good information before I even started.

Puckdropper

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Wise is the man who attempts to answer his question before asking it.

To email me directly, send a message to puckdropper (at) fastmail.fm

Ok, my ferric chloride story, I'm etchimg pcbs in a ¼" glass tray I made

Using silicone to stick sides to a 12"x12" bottom. Working on my wife's NEW

stove that has stainless steel burner covers. To heat the solution I decided to leave

the cover on the burner and set the burner on the lowest setting. So, I'm etching

along just fine until I notice a little etchent on the porcelain, the bottom piece of

glass developed a crack. Now the etchant leaked on to the stainless steel burner

cover and onto the stove top, down the front and into the burner hole.

After a major clean up, the only real damage was to the stainless burner cover,

It has a deep etched line where the crack in the glass was.

I had used this method 5 or 6 times before the heated glass became a problem.

BTW the best trick I learned about etching is to float the pcb on top of the

etchant. Apply a piece of tape to the back side of the pcb to make a little grab

point and just float it on top of the etchant. Etching goes much faster, I'll let

others explain why.

Mike

A sort of Rube-Goldberg method for heating the etchant is to use a hot plate. There are better methods, but this one is cost free for most people.

Ed

The method I use for heating is just to set the plastic etching tray on a waterproof (plastic coated) heating pad. This is the standard commercial home-use pad, with the fabric cover slipped off. It doesn't get anywhere near as hot as a hotplate, but that's a virtue... never boils over, etc.

Best regards,

Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis

Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!

Go to the grocery and get a glass baking dish. :-)

Cheers! Rich

I've only done a few boards so far, but I've found that floating the etchant tank (hahaha--it's a plastic sandwich box) in hot water does the trick nicely. No chance to overheat; spills go only into water, etc.

Torben

Good idea - I just tried the heating pad method tonite, and I like it better than the hot plate. Thanks!

Ed

That's the same method I used to use. The only drawback I found was that it is easy to get careless when agitating the inner tray, & splash water or etchant everywhere.

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   W  "Some people are alive only because it is illegal to kill them."
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Oh man. I don't do the etching in the sink. Got a pregnant woman in the house. :)

I go out to the porch on an old wood bench, with a cube heater blowing warm air over the pre-warmed etchant with the board in it. I use a cotton ball to rub etchant on the soldering side. I also like to float the board in the etchant on the component side for a while first, to give it a head start in dissolving before I start on the soldering side. I can usually do a pretty good 4cm by (say) 6cm board in 5 to 10 minutes.

Torben

Me either. Ever seen what ferric chloride does to stainless steel? ;)

--
   W  "Some people are alive only because it is illegal to kill them."
 . | ,. w ,      
  \\|/  \\|/              Perna condita delenda est
---^----^---------------------------------------------------------------