Magnetic Drive Etchant Pump

It's possible my boards won't float... I'm doing the poor mans ground plane and gluing 2 boards together prior to etching. Like this....

top

--------SMD components

--------Cu

--------FR4

--------Epoxy glue

--------Cu

--------FR4

It might be bizarre but my app needs the FR4 on the bottom for isolation reasons.. ....And it's also nice I don't have to put etch resist on the additional copper layer. D from BC

I recently saw one of these on sale for 16.50 euros:

I found it in a surplus shop on Schillerstrasse in Munich. That street is near the railway station and would probably be of interest to many people in this NG.

Chris

Yeah...I spotted some mag drive aquarium pumps on the net. I suspect they're good for salt water aquariums. All plastic inside.

I did try pumping etchant with a scrap car windshield wash pump....I don't know if I burned out the motor due to overheating or the etchant messed up the mechanics.. I got the motor smokn hot... I should have cracked open the pump to find out what failed.

I wonder if a 12V windshield wash pump can be submersed in cold fresh water (or oil) for more continuous lifespan.

D from BC

No. Even submerged, washer pumps aren't rated for continuous duty.

And it'd have to be submerged in the etchant, so it would eventually disappear anyway. ;-)

Good Luck! Rich

I saw a very effective etching tank that used minimal etchant. It was a *very* thin vertical tank made from two sheets of glass, but the side "walls" were only strips of glass. 5 mm thick. The cunning part was the bottom was 5 mm dia glass tube, with about 10 holes drilled along it's length. One end was blocked off, and the other fed, via PVC tubing, from an aquarium pump.

The drilling took some time and care with a special glass drill (Lee Valley has them) but it was the only tricky part of the whole tank, and the results were worth it.

It was all bogged together with RTV intended for aquarium tank construction.

Heating of the tank and etchant was done by a sheet of about 3mm alloy held against one glass side with plastic clamps.The other side of the alloy sheet has about 10-12 WW power resistors epoxied to it, these are connected to a variable DC supply set to provide whatever heat is required.

The PCB is lifted out via a length of thin fishing line attached to a tiny hole in one corner.

It was important to have a solid lid, otherwise the room filled with etchant vapour.

Barry

I've been using things like these:

model VA80 etc. Found at pet shop here for a similar price (~$10). Internally, the magnet runs on a stainless steel pin, which does corrode away eventually. I use it maybe twice a month and they last about 2-3 years. If you go this way, wash the innards carefully after etching and do add some oil on the pin when it's in storage.

I park it in a shallow glass bowl next to the pcb, and put a piece of 8mm fuel hose on the exit and loop it back down so it points at the pcb. 30mil tracks are no problem. My artwork doesn't allow much better, usually.

Haven't tried floating the pcb as recommended by others here, but will now.

L

And don't forget about Nylon. Ferric Chloride also attacks Nylon.

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On Fri, 10 Aug 2007 08:40:53 +1200, Barry Lennox wrote: [snip]

I tried something similar except I made it out of polycarbonate and sunk the thing in a bath of hot tap water. The bubbler was a polyethylene tube at the bottom with holes punched in it.

Etchant leaked out from around the tubing. I tried to silicone seal around polyethylene tubing...Futile... :( I might get it going again once I glueweld in some polycarbonate tubing.

_______ __ /______/| _/ 6mm | || |/\\/\\/\\|| | * * || | * * ||

I checked out that link..Looks like a fresh water pump....

I think the salt water pet pumps have a better chance at being nonreactive to etchant. Like on:

"Magnetic Drive pumps are ideal for salt water aquariums and live fish holding tanks. These true Mag-drive pumps are completely sealed and do not have shaft seals to wear out. Only a single casing O-ring is used and prevents the liquid from leaking. They are manufactured using the latest engineering plastics to prevent corrosion. The permanently split capacitor start ( PSC ) motors are totally enclosed fan cooled ( TEFC ).Continuously rated, Class E insulation, Thermal overload protection and suitable for indoor use."

D from BC

If you can come up with a way make it entirely of glass and silicone tub caulk (the kind that stinks of acetic acid), you should be able to make a very stable assembly. Glass and silicone bond to each other very strongly.

Agreed, That's exactly why the whole thing is made from glass. No plastic-RTV bond anywhere.

The only tricky bit is drilling the glass tube, but it can be done with the right drill, care and a little practice helps too.

I also have a friend who blows glass for a uni lab. He reckons it's easier to heat the glass tube where you want the hole, and just pick a little hole out with an old nail or similar. Sounds doable but messy to me.

It sounds to me like it'd be much less messy than drilling! You'd need a sufficiently small flame, of course, and use Pyrex so it doesn't crack from the differential expansion. (or is that a dumb thing to say because it's so glaringly obvious?) :-)

Cheers! Rich

Quite probably, but I'd give the whole job to my friend, he reckons it's less than a 10 minute job !

Barry

I had my polycarbonate pieces cut by laser within 10 minutes. It's one of the main reasons why I like polycarbonate projects.

D from BC

Actually I would not use Pyrex - you need to get it much hotter than ordinary (soda) glass in order to melt it. Think oxy-torch instead of Bunsen burner. And it can still crack if you don't cool it slowly and gently. Quartz has a really low coefficient of thermal expansion, but then that is even harder to melt than Pyrex.

Chris

You guys are making this ALL to complex!

I've got LOTS of etching tank setups. Cheap and effective. I build a tall thin (about 1 inch gap) somewhat wider than the circuit board you wish to etch out of plexiglas. Make it rather taller than the boards. It's easy to glue with solvent glue and you put a couple of cross pieces on each end for feet. Fit a L shaped piece of PVC pipe (capped) into the bottom and up the side. Drill two rows of small holes in the bottom leg. (Use a PC board drill! ... You ARE making PCBs right?) down one side of the tank (inside) you hang a glass fish tank heater to heat the etchant. These heaters usually have a temp control which you turn up to get some decent heat. Supply some air to the bottom pipe from say an air brush pump and you are in business! The bubbler etches nicely (works better with other etchants than Ferric Chloride but does work with that too.) Basically just a plastic tank partly filled with etchant covering the board, heated with the heater and stirred with bubbles. Build one, you'll love it.

Yeah, they get all stained with ferric Chloride after a while but who cares the things cost very little to make if you have some access to plastic scraps of some kind. Glass? We doan need no stinking glass! Just make sure the seams are nice and tight all around before you start to try it with etchant.

OR if you insist, my previous setup was a pyrex baking dish mounted on a hotplate for heating which was mounted on a pivoting board and gearmotor that gently rocked the dish so etchant sloshed form one end to the other. Believe me the bubbler is MUCH better!

Benj