My new etching tank

cmartinez

Joined Jan 17, 2007
7,312
I agree that alignment is a major pain however the few times I have done it I put extra pads in opposite corners of the layout, stuck one side of the layout to the PCB, drilled the smallest hole possible (0.3mm in my case) through the centre of the alignment pads, put needles though the holes and then aligned the layout for the other side on the needles. It wasn't spot on but it was good enough for things like 0.1" pitch PCB headers.
Ha! that sounds pretty much like the plan I had in mind. I'll give it a try and tell you how it went. Thanks!

GopherT

Joined Nov 23, 2012
8,012
These are from the cole-parmer website for materials compatability for Ferric Chloride. Unforatunately, the tests are normally done at room temperature and concentrations may vary if they are literature values because they are rarely all done by the same team. I would guess they use the standard concentration for commercially available FeCl3.

Effect of corrosion is usually much worse as you heat the inorganic solutions.

Material / Compatibility

ABS plastic / A-Excellent
Acetal (Delrin®) / D-Severe Effect
Aluminum / D-Severe Effect
Brass / D-Severe Effect
Bronze / D-Severe Effect
Buna N (Nitrile ) / A-Excellent
Carbon graphite/ A-Excellent
Carbon Steel / D-Severe Effect
Carpenter 20 / D-Severe Effect
Cast iron/ D-Severe Effect
ChemRaz (FFKM) / A-Excellent
Copper / D-Severe Effect
CPVC / A-Excellent
EPDM / A-Excellent
Epoxy / A-Excellent
Fluorocarbon (FKM) A-Excellent
Hastelloy-C® / B2-Good
HDPE / D-Severe Effect
Hypalon® / B-Good
Hytrel® / C-Fair
Kalrez® / A-Excellent
Kel-F® / A1-Excellent
LDPE / A1-Excellent
Natural rubber / A-Excellent
Neoprene / B-Good
Noryl® / A2-Excellent
Nylon / A-Excellent
Polycarbonate / A2-Excellent
Polypropylene/ A-Excellent
Polyurethane / A-Excellent
PPS (Ryton®) / A-Excellent
PTFE/ A-Excellent
PVC / A-Excellent
PVDF (Kynar®) / A-Excellent
Silicone / B-Good
Stainless Steel - 304 / D-Severe Effect
Stainless Steel - 316 / D-Severe Effect
Titanium / A-Excellent
Tygon® / B-Good
Viton® / A-Excellent

cmartinez

Joined Jan 17, 2007
7,312
These are from the cole-parmer website for materials compatability for Ferric Chloride. Unforatunately, the tests are normally done at room temperature and concentrations may vary if they are literature values because they are rarely all done by the same team. I would guess they use the standard concentration for commercially available FeCl3.

Effect of corrosion is usually much worse as you heat the inorganic solutions.

Material / Compatibility

ABS plastic / A-Excellent
Acetal (Delrin®) / D-Severe Effect
Aluminum / D-Severe Effect
Brass / D-Severe Effect
Bronze / D-Severe Effect
Buna N (Nitrile ) / A-Excellent
Carbon graphite/ A-Excellent
Carbon Steel / D-Severe Effect
Carpenter 20 / D-Severe Effect
Cast iron/ D-Severe Effect
ChemRaz (FFKM) / A-Excellent
Copper / D-Severe Effect
CPVC / A-Excellent
EPDM / A-Excellent
Epoxy / A-Excellent
Fluorocarbon (FKM) A-Excellent
Hastelloy-C® / B2-Good
HDPE / D-Severe Effect
Hypalon® / B-Good
Hytrel® / C-Fair
Kalrez® / A-Excellent
Kel-F® / A1-Excellent
LDPE / A1-Excellent
Natural rubber / A-Excellent
Neoprene / B-Good
Noryl® / A2-Excellent
Nylon / A-Excellent
Polycarbonate / A2-Excellent
Polypropylene/ A-Excellent
Polyurethane / A-Excellent
PPS (Ryton®) / A-Excellent
PTFE/ A-Excellent
PVC / A-Excellent
PVDF (Kynar®) / A-Excellent
Silicone / B-Good
Stainless Steel - 304 / D-Severe Effect
Stainless Steel - 316 / D-Severe Effect
Titanium / A-Excellent
Tygon® / B-Good
Viton® / A-Excellent
There's one item in the list that I have to disagree with, and that is nylon. I've been using nylon strings (the fishing reel type) to fish the boards out of the tank for several years now, and they do last a while (but not forever) if the process is at room temperature. But if the process is run at 50°C the string will melt and break.
Also, that's one of the reasons why I had to buy a special PVC valve from USplastics. They're the only ones I know that manufacture those valves using PVC exclusively. The rest of the commercially available valves that I know of use a nylon sphere (or some other similar material) in them that after a few days reacts with the FeCl3 and melts away.
I'm now using a special PVC string that I found hard to find, but that perfectly withstands the heated process. Only slight disadvantage is that it's quite elastic and feels a little like a rubber band ready to break if it's stretched too much. But that hasn't happened yet.

GopherT

Joined Nov 23, 2012
8,012
There's one item in the list that I have to disagree with, and that is nylon. I've been using nylon strings (the fishing reel type) to fish the boards out of the tank for several years now, and they do last a while (but not forever) if the process is at room temperature. But if the process is run at 50°C the string will melt and break.
Also, that's one of the reasons why I had to buy a special PVC valve from USplastics. They're the only ones I know that manufacture those valves using PVC exclusively. The rest of the commercially available valves that I know of use a nylon sphere (or some other similar material) in them that after a few days reacts with the FeCl3 and melts away.
I'm now using a special PVC string that I found hard to find, but that perfectly withstands the heated process. Only slight disadvantage is that it's quite elastic and feels a little like a rubber band ready to break if it's stretched too much. But that hasn't happened yet.

If PVC works well, you could try PVC cement. That is just PVC polymer dissolved in a solvent. It might take some time for the solvent to evaporate against your glass but the solvent is somewhat soluble in water so you can extract it with water to get the edges to firm up.

cmartinez

Joined Jan 17, 2007
7,312
If PVC works well, you could try PVC cement. That is just PVC polymer dissolved in a solvent. It might take some time for the solvent to evaporate against your glass but the solvent is somewhat soluble in water so you can extract it with water to get the edges to firm up.
That's a very good idea... and maybe I could experiment by adding a few PVC shavings in the cement, to thicken it a bit... see how that works. Thanks!

GopherT

Joined Nov 23, 2012
8,012
That's a very good idea... and maybe I could experiment by adding a few PVC shavings in the cement, to thicken it a bit... see how that works. Thanks!

It would be easier to thicken it by pouring it into a large pan and letting some solvent evaporate instead. The manufacturing process requires extensive mixing time to get the PVC shavings into solution. Do it outdoors and away from flame/spark sources. The solvent is flammable.

Robin Mitchell

Joined Oct 25, 2009
819
Two glues come to mind for sealant.

Two part epoxy: This is the strongest stuff that will not only bond just about any two things together but also provide a great seal for water and or etchant. However, only ferric chloride has been tested so I cannot suggest if any other etchant is being used.

Silicone Glue: This is good for general sealing but again no idea how it reacts with mineral acid based etchants.

My advice would be to use a chem proof pump (like a brush-less aqua pump), and have pipes into a premade tanks with the pipe going through the top instead of through the container.

All the best,
Robin

strantor

Joined Oct 3, 2010
5,534
Very sexy. I'm turned on by your apparatus.
I see you're not content to just do it in a tupperware floating in hot water? That's how I've done it; it was a kluge but I was able to make 2-sided boards no problem. I think you're working it up to be a bigger issue than it really is.

I did toner transfer on one side of the board, take it to the drill press and drill all my holes. Then get my other side toner transfer paper ready, hold the drilled board up to the light so I can see the little dots of light come through, and line everything up, tape in place. The only issue I had doing 2-sided boards with toner transfer, was squash-melting the first side while transferring the second side.

sirch2

Joined Jan 21, 2013
1,029
The only issue I had doing 2-sided boards with toner transfer, was squash-melting the first side while transferring the second side.
Which is why I did both sides at once. Also I was concerned that any damage to the first side during drilling may not be picked up until after the board was etched.

Lestraveled

Joined May 19, 2014
1,946
C @cmartinez
A while ago you wanted to know about etching times for sodium persulfate. Tonight I etched five, 4" X 6" boards. I mixed 2 Kg of sodium persulfate in 2 liters of tap water. The tank temperature was just below 50 Deg C. I etched the boards one at a time. The first three boards were complete in 22 minutes and the fifth board was complete in 31 minutes. (Times include pulling the boards in and out of the tank.) The etchant still had plenty of capability. I put the last board (5th) into the tank, took the fourth board into the bathroom to wash it off, picked up another beer, and by the time I got back to the bench the fifth board was half done.

Attachments

• 117.8 KB Views: 117
Last edited:

cmartinez

Joined Jan 17, 2007
7,312
C :cmartinez
A while ago you wanted to know about etching times for sodium persulfate. Tonight I etched five, 4" X 6" boards. I mixed 2 Kg of sodium persulfate in 2 liters of tap water. The tank temperature was just below 50 Deg C. I etched the boards one at a time. The first three boards were complete in 22 minutes and the fifth board was complete in 31 minutes. (Times include pulling the boards in and out of the tank.) The etchant still had plenty of capability. I put the last board (5th) into the tank, took the fourth board into the bathroom to wash it off, picked up another beer, and by the time I got back to the bench the fifth board was half done.

Nice! In FeCl3 my boards are done in less than 7 minutes. But I hate that chemical. It stains everything it touches, and its vapors corrode every metal that sits close by. That's why I had to add a lid to my tank when it wasn't in use.
I see you're using a fish tank heater to warm your etchant up. The reason I use a high power halogen light is because my tank's cavity is quite narrow (less than 1/4") and nothing will fit in it but the board. On the other hand, my etchant's vapors would probably affect any heating device exposed to them.

Lestraveled

Joined May 19, 2014
1,946
Nice! In FeCl3 my boards are done in less than 7 minutes. But I hate that chemical. It stains everything it touches, and its vapors corrode every metal that sits close by. ..............
I didn't even use gloves tonight. You should get some sodium persulfate and try it. It is a much kinder etchant. I have been doing work for a chemical company in South Tucson. They had a few 25 lB bags of sodium persulfate left over from a project and they gave me one. I seriously lucked out.

cmartinez

Joined Jan 17, 2007
7,312
Well, I'm happy to inform everyone that my tank has stayed in pristine conditions for more than 60 days now. Not a single component (including the valve, and buna-n seal) has shown deterioration, or any sign that it's being attacked by the continuous presence of the FeCl3 ... I now consider this little project of mine a success

nerdegutta

Joined Dec 15, 2009
2,676
Great. Good job. How much FeCl do you use for each etch? How many etches do you get out of the FeCl?

cmartinez

Joined Jan 17, 2007
7,312
Great. Good job. How much FeCl do you use for each etch? How many etches do you get out of the FeCl?

Last edited:

Wendy

Joined Mar 24, 2008
22,368