In a previous post, I showed off my etching tank as part of my PCB making process.
But here's the thing: I HAVE JUST HAD IT! with the stupid thing...
My original design was made out of three layers of 1/4" thick tempered glass:
Initially, I thought that my headache was going to be finding an appropriate valve to drain the thing when the FeCl3 lost its potency after processing several PCBs... and it took me a while, but I did find it and it performed quite well.
BUT... my personal pain in the backside turned out to be the thing that I least expected to be an issue (isn't that usually the case?) I used silicone to seal the tank's edges. And after many leaks, fails and catastrophic events that did considerable corrosion damage to the tooling stored in my shop, I finally realized that FeCl3 actually attacks and eats through silicone sealant!
I tried many other sealants after that. Among them there were acrylic-based, polyurethane, and some other stuff that I can't remember. But the result was always the same: after a few days of laying in the tank, the etching solution ate through the sealant and made a mess on my work bench and on the floor. That event happened to me more than once. Trust me, finding a nasty surprise awaiting you inside your workshop after enjoying a normally nice weekend is not the ideal way of starting your mondays.
Here's another downer: I spent a few bucks buying silicon hose at Amazon, only to find out that the frigging etchant also attacks the stupid thing!
On the positive side, I had learned that the only materials I've seen that are (apparently) immune to the etchant are:
So here's my latest design and construction of my etching tank:
The materials I used are:
The front and back plates of the tank were cut in my CNC router, and afterwards several 1/2" threads were tapped in the back piece's perimeter. The front plate was similarly cut, with an equal amount of slightly larger holes (17/32") in the front plate. A NPT 3/8" thread was also tapped in the back plate, to attach the PVC drain valve.
I also cut the "U" shaped acrylic separator for the tank in the CNC router with the same holes in it, but using 1/4" thick acrylic instead.
The three layers were then assembled and bolted together. The 1/4" o-ring material and the 1/4" pvc hose were also placed between the front and back plates. I drilled six small holes (using a needle) in the PVC hose prior to assembling the thing. This is so as to have a more or less uniform bubble curtain inside the tank after the aquarium pump is turned on. But after testing it, I realized I could've gotten away with maybe up to 12 holes instead of just six.
I then replaced my old tank with my new one on my heating fixture and, voilá! ... the thing worked beautifully!
Another advantage of this new tank is that I made it smaller, so it stores considerably less etchant, and therefore its temperature raises much faster than with the previous tank.
I'm just crossing my fingers now and hope that none of the materials I used is affected (on the short term at least) by the FeCl3
But here's the thing: I HAVE JUST HAD IT! with the stupid thing...
My original design was made out of three layers of 1/4" thick tempered glass:
Initially, I thought that my headache was going to be finding an appropriate valve to drain the thing when the FeCl3 lost its potency after processing several PCBs... and it took me a while, but I did find it and it performed quite well.
BUT... my personal pain in the backside turned out to be the thing that I least expected to be an issue (isn't that usually the case?) I used silicone to seal the tank's edges. And after many leaks, fails and catastrophic events that did considerable corrosion damage to the tooling stored in my shop, I finally realized that FeCl3 actually attacks and eats through silicone sealant!
I tried many other sealants after that. Among them there were acrylic-based, polyurethane, and some other stuff that I can't remember. But the result was always the same: after a few days of laying in the tank, the etching solution ate through the sealant and made a mess on my work bench and on the floor. That event happened to me more than once. Trust me, finding a nasty surprise awaiting you inside your workshop after enjoying a normally nice weekend is not the ideal way of starting your mondays.
Here's another downer: I spent a few bucks buying silicon hose at Amazon, only to find out that the frigging etchant also attacks the stupid thing!
On the positive side, I had learned that the only materials I've seen that are (apparently) immune to the etchant are:
- Acrylic
- PVC
- Teflon
- BUNA-N (Nitrile)
So here's my latest design and construction of my etching tank:
The materials I used are:
- a sheet 3/8" clear acrylic
- another sheet of 1/4" clear acrylic
- clear 1/4" PVC hose
- 1/4" diameter o-ring material (actual diameter is 0.275")
- A few 1/2"-13-UNC Hex PVC screws
- One NPT 3/8" PVC valve
- A 2-209 o-ring (11/16" I.D. 1/8" thick) to guarantee a perfect seal between the valve and the back plate.
- An aquarium double-outlet air pump.
- 1/2" PVC hose for the drain valve's output
- One plastic bucket to receive the used etchant
The front and back plates of the tank were cut in my CNC router, and afterwards several 1/2" threads were tapped in the back piece's perimeter. The front plate was similarly cut, with an equal amount of slightly larger holes (17/32") in the front plate. A NPT 3/8" thread was also tapped in the back plate, to attach the PVC drain valve.
I also cut the "U" shaped acrylic separator for the tank in the CNC router with the same holes in it, but using 1/4" thick acrylic instead.
The three layers were then assembled and bolted together. The 1/4" o-ring material and the 1/4" pvc hose were also placed between the front and back plates. I drilled six small holes (using a needle) in the PVC hose prior to assembling the thing. This is so as to have a more or less uniform bubble curtain inside the tank after the aquarium pump is turned on. But after testing it, I realized I could've gotten away with maybe up to 12 holes instead of just six.
I then replaced my old tank with my new one on my heating fixture and, voilá! ... the thing worked beautifully!
Another advantage of this new tank is that I made it smaller, so it stores considerably less etchant, and therefore its temperature raises much faster than with the previous tank.
I'm just crossing my fingers now and hope that none of the materials I used is affected (on the short term at least) by the FeCl3
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