PROJECT: PCB Etching Tank

[Spawn]

For a while I am in search for a good etching tank, but the good ones are expensive and cheap ones are crap.
For example the Velleman model or the Taiwan model are known to fail, they start to leak after a while and not even on the glued pieces but on the material they use. There are some examples on the Dutch electronics forum. These models cost around 70 euro till 90 euro.

Before I start, this is not going to be a Tupperware or whatsoever tank, I want nice solid and fast etching tank.

After reading those stories about leaking I decided to go with a glass tank, but the problem was finding right size tank, I don’t need to etch big PCB’s the standard 16cmx10cm (6.2”x3.9”) is more than enough for me. I was in hunt for a glass tank around this measurements: 40cm (15”) high, 30cm (12”) wide and with 15cm (6”) depth.  I want the height for the 500Watt heating element which I will explain why so much power.

The only option for such tank was a battery jar (also known as glass battery box), no glues or silicone kits whatsoever, a nice solid tank, I didn’t want to get some aquarium tank because of the silicone joints. After a long search in the garden stores I was about to give up, the biggest problem was the height, most tanks where around 15 to 20 cm

Today my wife ask me to pick up something in a garden store, I never checked this store before because it was in another city and my wife saw something in a add. While I was walking in that store I was also looking for a battery jar and I found one!
Not the exact measurements I want but it was close enough for me, this thing was pretty cheap too, it was on discount and it cost me 15 euro

Measurements are 30cm (12”) high, 20cm (7.8”) wide and deep, it’s little bit wider than I want but I am still happy with it.


Before we go in to the materials:
I will post every update including pictures and videos in this start post.

The idea is having a tank which heats up in no time and etches pretty fast.

The tank: it looks pretty solid and has 5mm thick glass:



Almost all materials below are from this ebay store: Aquarium HQ

The heater: I ordered 2x 300Watt aquarium heaters (P0w4H in the house ), like I said I want a fast etching tank, the idea is to get around 45C to 50C (113F to 122F) in no time and stay there, but most aquarium heaters are limited till 35C like this one below, so I have to open it up and hack it in some way to make it go till desired temperature, if that won’t work I just take out the thermostat and short it, there are digital aquarium temperature controllers if needed, these are not that expensive.
This is the only decent priced 300W with this length btw:


If anyone wants to buy a heater don’t buy chrome ones, we want as much possible glass made material in our tank


The air pump: I took a pump with high rating and because of the rating I wanted a adjustable pump, we don’t want our PCB’s flying around the room after all. The pump is rated at 192liter air/hour (50gallon air/hour) There are some dual outlet pumps out there but I want minimize the tubing.



The bubble maker: I didn’t want to drill holes in some tubes and see if the bubbles get all over the tank so I went for a aquarium bubble air wall, which has the right length for the tank, I ordered 2 air walls and they will be attached at the bottom of the tank:


A old fashion good trusty glass thermometer:


Last but not least, small materials like T-pieces, small knees, tube, suction pads for the tube and most important a check valve, we don’t want the aggressive etching material in our pump when it is sitting next to the tank.


That’s all I can think of to get, I ordered them all and when these arrive I will keep this topic updated with the test and finishing it.

Price tag till now is still reasonable with 64EUR or 85USD or 81AUD or 54GBP

_{PS: If you find any typo’s or bad English grammar, you can keep it}

[Simon]

yes I have not yet found a decent container for etching and a "cheap" one off ebay just fell apart on me....

[Zad]

I think I would be paranoid that localised heat would crack the glass, as 5mm isn't very thick.

[Simon]

I think I would be paranoid that localised heat would crack the glass, as 5mm isn't very thick.

it would be a sudden temp jump that would crack the glass, if the heater is kept away from the side it will be ok

[Spawn]

Because of my work I tested a lot proto type machines in the past and wrote up testing protocols.

This is not industrial of course, but when the bubbler and the heaters arrive I will do a long term test, like from room temperature water till around 45C and try to keep it there for hour or two with the heaters attached on the glass, if it cracks bad luck we start over again

[george graves]

What the typical use of the "battery boxes" ?  (so the store clerk didn't look at me strange!)

[IanB]

What the typical use of the "battery boxes" ?  (so the store clerk didn't look at me strange!)

They are usually antiques in their original form. You would fill the glass jar with acid and suspend lead plates in it from the top to make a lead-acid accumulator. Typically you would not find one made for that purpose since the 1920's.

Today I think they are probably just decorative glass items, perhaps to be used as a small fish tank or display case for aquaculture? I suspect "battery box" is just a name carried over and no longer describes the true function.

[Spawn]

Here a nice history :

Why was a battery required 2000 years ago?
In June, 1936, workers constructing a new railway near the city of Baghdad uncovered an ancient tomb. Relics in the tomb allowed archeologists to identify it as belonging to the Parthian Empire. The Parthians, although illiterate and nomadic, were the dominating force in the Fertile Crescent area between 190 BC to 224 AD. It is known that in 129 BC they had acquired lands up to the banks of the Tigris River, near Baghdad.
Among the relics found in the tomb was a clay jar or vase, sealed with pitch at its top opening. An iron rod protruded from the center, surrounded by a cylindrical tube made of wrapped copper sheet. The height of the jar was about 15 cm, and the copper tube was about 4 cm diameter by 12 cm in length. Tests of replicas, when filled with an acidic liquid such as vinegar, showed it could have produced between 1.5 and 2 volts between the iron and copper. It is suspected that this early battery, or more than one in series, may have been used to electroplate gold onto silver artifacts.

Information is taken from: Allaboutbatteries.com

But near history of it was indeed in 20’s at railroad companies and more.

The jars we use these days are made for putting flowers in them or for decoration.

[Spawn]

The first addition to the tank
Waiting on those orders to finish will take long time lol

I had some lexan tube laying around, I made 2 PCB holders.


Made a flat side, to prevent rolling on the tank:

[M. András]

the liquid will constantly move by the constant air bubbles this will prevent the localized heat buildup at point of the glass? by simply stiring the etching solution.

[Spawn]

Yes indeed, and bubbles are actually for the sodium persulphate because if it gets heated more than 50 Celsius it will looses the etching effect, so bubbles will move the heat around to prevent that.

I received the air pump today, but it is weird because I ordered almost everything from same seller.

[Spawn]

Received all items I ordered from the seller above today, 7 days is great I have seen worse like a month even more.
Unfortunately I ordered the air wall stone from another seller so I can’t test the tank yet.

It looks like I don’t have to modify the heating elements, the temperature knob can be turned further than the max 35 Celsius so I think 40 is possible without any tweak.

To be honest I start to worry about this tank size It needs at least 10 or 11 liters etching stuff that’s a lot, to stock this it would be problem, there are smaller battery jars but I can’t find one.

Another option is the tank from PRO-MA, they build good quality etching tanks but it’s not from glass, the tank takes 1,75 liters and that’s really good . The tank from PRO-MA looks like this: http://www2.conrad.nl/goto.php?artikel=530360
The tank is for this machine: http://www2.conrad.nl/goto.php?artikel=530328

The PRO-MA tank:


Here a photo of the knob from the heater, as you can see the temperature can be set more than the marks on it:





A photo with heating elements in the tank, it looks like these are made for this tank

[kripton2035]

this pro-ma tank has really bad review on the conrad web site ... 

[TerminalJack505]

That looks like a fun project.  You must plan on doing a lot of boards.

I'll stick to the cheapskate method: a foam brush.  Toss the board in the etchant (ferric chloride) and scrub the board with a foam brush.  It's a pretty quick and effective way to etch boards.

[Spawn]

That looks like a fun project.  You must plan on doing a lot of boards.

Lol it's more for the fun part than making a lot boards

this pro-ma tank has really bad review on the conrad web site ... 

Yeah seen it just a minut ago, people say they leak out of the box, nice to have a water tank which leaks out of the box... 

[IanB]

Have you thought about making your own tank?

http://youtu.be/hT6Ow_cBTps

Acrylic plastic appears to be resistant to most aqueous solutions including ferric chloride, with the only exception I can see being chromic acid.

If you have access to some workshop tools you could make a tank to your exact requirements.

[T4P]

Have you thought about making your own tank?

http://youtu.be/hT6Ow_cBTps

Acrylic plastic appears to be resistant to most aqueous solutions including ferric chloride, with the only exception I can see being chromic acid.

If you have access to some workshop tools you could make a tank to your exact requirements.

I never really had the idea but then , a circular saw should do the job 

[Spawn]

Thanks for heads up IanB, in fact I did use lexan and glued (welded) together where I worked for a medical factory 10 years ago, for some reason they ended up letting loose the “welded” parts when physically abused or higher temperature exposure, I used almost same liquid from that video.
You could say “you just suck at welding lexan” but it was not only my work my coworkers had same issue.
Besides that, I know a company from those days which I have good contact with and I can let them make a tank from lexan with minimum welding like making a U shape and then weld 2 pieces to open sides, and choose a thickness till 25mm and I believe that could work, because the piece you weld has really big surface, but the price would be too much, but you never know with me, if I can’t find any solution I might ask them for a price. They did vacuum tanks for us to test the blisters on leakage and they worked perfect, but then again they used 25mm thick lexan.

Dave.S its best to use a table saw with certain speed and cutting (pushing through) speed, if you go too fast the piece you cut start to smelt and gets really messy. You also can use a electric jigsaw by using mask tape on your piece but you need really steady hands because of the piece you cut needs to be welded.

Since I wrote the last piece here I was looking for another solution for the tank, and I came up with a square glass vase 25 cm high and 10cm each side, inner side would be around 9cm x 9cm and the water will be filled till 22cm and that makes only 1.78 liters of etching liquid which is perfect, with this vase I can use a standard EU PCB in this tank because 9cm square has approx 12,5cm distance between diagonal corners.
This would cost me more money, because the heaters I got are too big for that and i need a new one, but like the title says it’s a project, if it works fine for me total costs of this tank will be even lower than the current one and that might help other people to get a idea.

[T4P]

Dave.S its best to use a table saw with certain speed and cutting (pushing through) speed, if you go too fast the piece you cut start to smelt and gets really messy. You also can use a electric jigsaw by using mask tape on your piece but you need really steady hands because of the piece you cut needs to be welded.

Certainly , i know about that . I would never use a circular saw for cutting acrylic to perfect straights , but sometimes helps to keep tool costs down ...
Maybe .
I saw those proxxon bench saws and my first thought is they are too small 
In the end i must really go to a proper tool shop and take a look at the bench saws .

[Spawn]

Lol, smallest proxxon table saw is even too small for bigger size PCB's

[T4P]

Lol, smallest proxxon table saw is even too small for bigger size PCB's

And there's only one size 

[Spawn]

And there's only one size 

You think so?
http://www.proxxon.com/eng/html/27070.php
http://www.proxxon.com/eng/html/28070.php
http://www.proxxon.com/eng/html/27006.php

But we are going off topic again Dave.S

[T4P]

And there's only one size 

You think so?
http://www.proxxon.com/eng/html/27070.php
http://www.proxxon.com/eng/html/28070.php
http://www.proxxon.com/eng/html/27006.php

But we are going off topic again Dave.S

I know , but on element14 there's only 1 size .

[Spawn]

Dave.S what do I have to do with element14? Let me ask it different way: Who cares what element14 sells? I can buy all 3 sizes here…

[Spawn]

Still no bubble wall stone, but I was in a hunt for another tank today, and came home with a round vase, it is 300mm high and 115mm round inside, good enough for a EU size standard PCB. And it only takes 2.5 liters, I can choose to fill till 2 liters with another heating element which I already ordered.
This is still 10 liters lower than the first tank option.
When the bubbler arrives I will take a video about the temperature, to see how fast it goes to 45 Celsius from room temperature.


Here is a photo with a standard size PCB and the 300W heating element.



I probably use the first tank as safety tank when the small one explodes on me