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Guest Ceawlin BSX029

Bubble etch tanks

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Here's an idea I just came up with whilst cleaning up the kitchen...For those who make their own PCB's, a bubble etch tank is rather appealing for even and quick etching. However, since most of these cost lots of money, and making one seems too much effort, I decided to make my own. How to do it, I wondered... I decided I needed a plastic tub that was large enough, and the correct shape. Tupperware tubs always seemed to be the horizontal type, and seemed great for using as trays as you can seal them solution in the tub. A vertical one was what I was after, but I didn't recall seeing any, until I went to load the washing machine and noticed the tub my missus has bought. It's a plastic tub that the liquid washing sachets come in, and it was the ideal shape. But it was a bit small, and was only suitable for half euro sized boards! My next major discovery came some minutes later whilst refilling the breakfast cereal tubs. These, I discovered, were the exact ideal shape and size for a large PCB!! How could I miss these!! I had been using them morning after morning after morning for goodness knows how long! And I hadn't even realised just how useful these are for making bubble etch tanks!!So after smacking myself on the head, I realised all I needed to do was buy an aquarium air pump, some plastic tubing, and some glue, and I could make my own tank! I also decided that I would have to use plastic clothes pegs to hold the board, making sure that the metal springs (if any) we not submerged in the solution. Doesn't matter if they did, as pegs are cheap and plentiful anyway. So, once I get my next wages in a week, I shall buy the necessary equipment and make my own, and post pics and techniques on my website, which will be posted here when it's done!What do you guys think of that?!

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>major discovery came some minutes later whilst refilling the>breakfast cereal tubs. These, I discovered, were the exact>ideal shape and size for a large PCB!! How could I miss>these!! I had been using them morning after morning after>morning for goodness knows how long! And I hadn't even>realised just how useful these are for making bubble etch>tanks!!Do you know what material the cereal tubs are made of ?Make sure they don't dissolve the plastics.I'd guess PE-LD or something similar.I'm also in the process of collecting parts for my next etching station.I already have a air pump, the chemicals, and a scanner+tanning thing which I merged into a UV exposure unit.I still need a tank and a heater.I haven't found good info on which plastics are good for etching tanks and which ones are not.Manuel

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So far I've used tupperware tubs, plastic take-away tubs, and various other plastic trays/tubs, and so far none of them seem to be affected by the chemicals, so I'mpretty certain it should be ok to use a cereal tub :)

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>So far I've used tupperware tubs, plastic take-away tubs, and>various other plastic trays/tubs, and so far none of them seem>to be affected by the chemicals, so I'mpretty certain it>should be ok to use a cereal tub :)I bet you could get 10 normal plastic boxes for the price of one Tupperware - that stuff is good, but *serious* ripoff for price.Go to your local plastics shop..//Tuomas

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I was going to make a bubble etch tank, but cheaped out. Instead I just used a flat plastic tupperware container, laid the boards in flat and manually moved them to keep the process going. Doing the FSBus key card took about ten minutes using Ferric Chloride at room temps. Also, by using a flat tray, you only need about half an inch of solution above the board to do the job. A bubble etch tank would be more efficient, but I wasn't figuring on going into production.No matter how you do it, remember this!! Triple check your exposed image for shorts BEFORE you put it in the etchant. The simple matter of taking a pin and scribing away a minute stretch of resist will save you hours of digging and scraping copper off of the board after. Hmm...almost sounds like a little first hand experience there?:-mad

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It was a hand-me-down, as if I'd spend that kind of money on a lunch box!

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>So far I've used tupperware tubs, plastic take-away tubs, and>various other plastic trays/tubs, and so far none of them seem>to be affected by the chemicals, so I'mpretty certain it>should be ok to use a cereal tub :)Yeah, but I'm also concerned about the long term effects.I would just keep the etchant in the machine, even when not in use.Then, it should be (long time) restistant against Fe3Cl, cupric chloride, ammonia persulfate, and sodium persulfate.Somebody with knowledge in plastics and chemistry should be able to tell which transparent plastics would work.Manuel

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Well I've had FeCl solution in a couple of different plastic tubs for some months now, and apart from the tubs turning brown, I've not noticed any deterioration at all. Maybe it's just the type of plastic, although I'm not sure what it is exactly

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>Well I've had FeCl solution in a couple of different plastic>tubs for some months now, and apart from the tubs turning>brown, I've not noticed any deterioration at all. Maybe it's>just the type of plastic, although I'm not sure what it is>exactlyFe3Cl is the stuff I least worry about. You can dip your fingers in it, it won't "etch them away" or hurt. It just creates stains that are not easy to remove. I worry more about the other etchants. What I'm after is a more scientific answer. Thats why I was wondering if someone is knowledgeable about chemistry/plastics.Glass should work as the etching machines you can buy are usually made from glass. But for glass, you need to get it cut professionally....and I want to use plastics and make the tank myself.The plastics I'm considering are polycarbonate, polystryrol, pmma(plexiglas), and PETG.I'd like to avoid polystryrol and pmma as the other two are much easier to work with.Manuel

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