Introduction: DIY PCB Bubble Etch Tank
How to make a home made bubble etch tank for under a tenner!
First you need
1 tub (pound shop)
1 plastic bin (pound shop)
1 fish bubble pump (Â£7 inc postage off ebay)
Some rubber tubing (hanging around - or could come with pump)
2 Cable ties
Hot glue gun
Red tape (blue might also do.... yellow may do but have problems - white tape cannot be used :-)
1 hour of spare time
1 sunny after noon in the conservatory (optional)
got all that stuff? lets bubble!
Step 1: Make the Hole for the Bubble Tube
Warm up the bottom (thats right mindy - the bottom) of the container as this is where we will insert the tube. Were going to put it here because of pressure issues... namely.. we dont want any!
Heat the bottom with the lighter and make a hole this way: i have tried drilling this type of plastic before and it's pretty brittle... this is the safest... but the tubs are only a quid so knock yourself out.
Don't let the plastic burn though as it stinks and will make the hole too large.
When it is ply-able, stick a screw driver through the plastic to make a small hole (roughly the size of the tube). Be careful not to make it too big otherwise it'll be a lot of hassle trying to seal again!
The reason we are going through the bottom and not poking the pipe through the gaping hole at the top of the container, is so that the top can be sealed off with the container lid - for easier storage and transport - plus.. water tight sealing the bottom isnt that hard.
Step 2: Mount the Bubble Tube
The tube will hopefully share bubbles through a lot more than one hole, IF the holes aren't too big. The sum of all the holes if you think about it, cannot be greater than the diameter of the pump's outlet, otherwise some holes will go un-used.
The holes, are just short of 1mm and on an initial test in a glass of water, all seem to function. As a tip, not all holes will output bubbles if the tube is not completly horizontal. This is because of the atmospheric/hydraulic pressures that exist when air is submersed. Ensure this bubble releaser is flat on the bottom
As hot glue doesnt seem to stick to this particular rubber tubing, i've used tape to adhere to it, and then let the glue adhere to the tape (clever huh). Whats even cleverer though is the making of little hot glue bridges that clamp the pipe to the bottom of the container.
Creating the seal is vital! But.. not that hard, just make sure you use PLENTY of hot glue around the joint. If you have more than 1 hour to spare, try sealing it with silicon sealant (the stuff you seal pipes/bathrooms/shower cubicles with). It takes longet to dry but would produce a better (more flexible joint).
Step 3: Pre-test!
Bite the bullet when you think it's cured and add a little! water. If it leaks after 10 mins of sitting still. try again!
Other wise.. Yay! lovely bubbles
The tube should then be bent up and down the side of the container as in picture three. This is so that incase the water tension does break back into the small holes of the bubble pipe, it won't rise all the way back to the pump - saving you WONGA on a new pump! I didn't think it would go back through the holes but it did... left my floor wet on my pre-test - luckily it wasn't the joint that was leaky!
So what do we have so far.... a wonderful fish tank... but we need to make this bad boy an etch tank
Step 4: Board Holder
Now we don't wanna keep dunking our hands in the solution (espescially seeing as FeO3 is sooo bloody staining)... so we make a small harness for PCBs
The harness will accomodate the boards and allow bubbles/currents to flow through.. for this we need out ÃÂ£1 waste basket!
Cut the mesh stuff out of the bin (note the large holes) and fold back on itself to create a small pouch.
At the bottom of the pouch i used a lighter again to soften the plastic. This is so is do not over stress the plastic and make it snappy snap. This way, the plastic moulds to a v shape.
Check the plastic is the right size for the tub and then start attaching it to the lid with cable ties. The lid of the container seemed a lot softer so i just drilled these holes out and stuffed the cable ties through.
Attach the harness loosely to the top so that it is free to move inside the container.
Step 5: Thats It!
Well thats pretty much it!
i mounted my tank on the bottom of the pump for space constraints, an because i had this pipe exiting the bottom end of my container! It now sits as a pretty individual unit
And boy does it' bubble!
maplin.co.uk or rapidelectronics.co.uk has some good etchant. It's a clear etchant that does not stain half as bad as ferric chloride and is MUCH safer!
Maplin code N06CG @ about Â£2.50 for 0.5L of etchant.
Maplin code MC49D @ about Â£15 for 5 litres worth.
Plus... if you've made a lovely see through tank... you may want the added benefit of seeing the boards develop before your very eyes!
Next development - add a heater unit (it's on order from ebay (fish heater ÃÂ£6)... but i couldn't wait for it to get here before starting)
Hope you enjoyed
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