Homebrew PCBs

I've not read a lot of the comments on this subject so this may already be 
covered. My two roubles worth if I may!

Part of the problem seems to be sealing submerged joints with a sealant 
which does not react to corrosive etchants.
Whatever the sealant, I thought maybe there was something else could be done 
to prevent the reaction, or at least slow it right down to a minimum. Paint 
for example.
Or better still perhaps, Shellac. (You probably know all this?)
Shellac is a PCB resist used in the past  It's quite robust and insoluable 
in water. Disolved in Methylated spirits (meths) it can be built up in 
layers by painting it on (meths evaporates much faster than it can desolve 
Shellac)

Since this is about building an eching tank, testing the materials is always 
a good idea.
This is probably what I'd go for:
Test the shellac theory first! If Shellac is worth it's salt, construct a 
"fishtank" to personal spec from glass, angle iron or aluminium using the 
most suitable sealant available. Paint any visible outside metalwork and 
exposed surfaces (except the glass) to prevent splash corrosion. Apply 
several coats of a Shelllac to the inside glass joints already sealed with a 
suitable sealant. Another possibility is Shellac varnish although I don't 
know what else it might contain besides shellac.
Every once in a while check the seals just in case. Any signs of 
deterioration, clean them up and apply another coat or two of Shellac.
I'm willing to bet several coats will last a very long time. (10p/10c in 
case I'm wrong!)
Take great care if using Meths. It is very highly inflamable with an 
invisible flame - you cannot see it to put it out!
Hope this helps.

And incidentally, Shellac can also be used to cover large areas of PCBs to 
preserve the copper. Removal is easy if you are not in a hurry! The process 
is quite painless but slow. Simply drop the etched board into Meths until it 
disolves.

One more unrelated incidental, Meths can be used to remove those ugly white 
circular stains left by hot cups on poIished tables. Wipe a small amount 
over the stain and light it. Allow a few seconds for it to burn out, or blow 
it out. Do NOT allow it to blister. Finish off with soft cloth. The heat 
will take out that stain. You might want to take the sensible approach and 
test it first.

I'm new to the group, located on the Shetland Islands (the one across the 
pond from Alaska)
Also fairly new to PCB making and no expert. Apologies for lack of 
qualifications.

Peter
MM5PSL


----- Original Message ----- 
From: kabowers@...
To: Homebrew_PCBs@yahoogroups.com
Sent: Saturday, January 15, 2011 4:10 AM
Subject: Re: [Homebrew_PCBs] Re: Building an etching tank?



On Sat, 15 Jan 2011 03:35:11 -0000, you wrote:

>
>> Rubbermaid or the equivalent plastic cereal container. Takes lots of
>> etchant, but has never deteriorated. Be careful with some of the
>> sealing rings, they disintegrate.
>>
>> Worked with FeCL3 and CuCL etchants, never leaked.
>>
>
>
>After I gave up on the Fish Tanks and using FeCL3 I now use CuCL in a 
>Plastic Container that I keep on the back porch. CuCL is a lot cheaper to 
>use than FeCL3.
>
>
>Ben
>
>
When I switched over from FeCl to CuCl I used the same plastic
tray with snaps on all four sides that I had used for several years.
It had a red plastic seal. A few weeks later I went to use the CuCl
to etch another board and the cover was really loose. The CuCl
had destroyed the seals; turned them into a white, crumbly substance.
There was a tray containing several partially discharged batteries sitting
beside the tray. The terminals on both ends were severely corroded.

Keith Bowers WB4LSJ- Thomasville, NC





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