Coke Bottle Vertical Etching Tank


Introduction: Coke Bottle Vertical Etching Tank

Not sure if vertical etching is for you? Try it out! Make a small scale, pint-sized, leak-proof etch tank in about 10 minutes, with 2 things you already have lying around: a DVD case and a 2L bottle.

Step 1: Parts List

What you'll need:

DVD case
heat gun

Now go buy:
an aquarium bubbler - $15.00
aquarium tubing - $3.00
a 2L bottle of soda - $2.00

Step 2: Step 1

Step 1:

Cut the top off your 2L bottle.

Step 3: Step 2

Stuff a standard sized DVD case into the top of the bottle.

Step 4: Step 3

Blast it with your heat gun until the bottle becomes DVD-case-shaped.

Step 5: Optional

Instead of hanging your board from a string, you might want to make a pcb holder like the one that I came up with. It's made from styrene.

Step 6: End

Using your heat gun, bend the aquarium tubing into an L shape. Weigh down with something to keep it on the bottom of the tank.

Fill it up and try it out.

The 1/2 oz test board (picture on the title page) took about 10 min to (over) etch at room temp.... and another 5 minutes to photoshop :). The part where my gimpy bubbler was directed over-etched pretty badly. Bubbling really does speed up the process quite a bit!

Step 7: So the Verdict Is In

It's been more than a few years since I wrote this Instructable, and I thought I would give an update on how things have worked out. There are some drawbacks to a vertical etch tank, but these can be overcome with some work. Here's a look at how my etching method has evolved over the years.

Step 8: Space Savings

The first issue with a vertical etch tank is space. It's supposed to save a lot of space. My current etch tank is 11" tall x 11" wide x only 1" thick. That's an 11 square inch footprint. But in reality, you need a stable base for the tank. So instead of taking up 20% of the space of a comparable tank, it ends up taking, say, 40% of the space. That's still great, right? Well, on top of that, you need WATER. When the board comes out, you need to catch the drips and rinse the board. I was using a glass baking dish for this. So now I'm up to 75-80% of the space that a regular setup would take. Clearly, in addition to a vertical etch tank, you need a vertical rinse tank, too. And if you have a good outdoor bench where you can put your tanks, you don't even need a base!

Step 9: PCB Holder

One of the other drawbacks to vertical etching is the question of how do you hold the board in the right position? With a tray + mechanical agitation, you just drop it in. In a horizontal etch tank with sufficiently fine bubblers, you can just lay the board on top of the etchant, and it will float. With a vertical tank, you need a holder of some kind. For single sided boards, you can just tape or hotglue them to a plate, and slide that into the tank. Or you can tie things up with strings. But I have come up with a pretty good PCB holder. This holds the board, firmly, and it allows easy adjustments to the board depth. The nylon hardware on it also keeps the board from tilting against the tank wall.

Step 10: Messy!

Another issue with a thin vertical tank is tank maintenance. The thin lip of the tank makes it difficult to extract the copper-rich etchant that builds up, and to pour in more acid solution. To eliminate the mess, I have finally found the right tools for the job. A turkey baster easily reaches into the tank to extract solution. And to eliminate the drips, I found I could stuff a piece of silicone aquarium tubing into the tip. The tube is melt-sealed on the inside end, and several small holes are drilled in it. And to add the acid solution, I keep a squirt bottle of acid and one of water (actually 97% water, 3% peroxide) in spray bottles. The spray bottles are convenient for adding solution directly to the tank. Also, you can spray the board, directly, if your etchant dies before a board is done. A third good reason to have these solutions in spray bottles is they're what you need to remove etchant stains! If you spill any etchant on concrete, for instance, hose it down with water. Then spray the spot with H202. Finally squirt a little acid on it, then wash away after only a couple seconds. Stain gone! (Always wear eye protection when handling strong acids. And be sure to squeeze some of the air out of the acid bottle before closing it, or some  will dribble out when the ambient temp rises!)

Step 11: Etching Capacity

One of the attractions of a vertical tank is that you can use less etchant for a given board size. But less etchant means less etching capacity. My tank hold approximately 1.3L of etchant when properly filled. It will barely eek one double-sided 6"x9" board with a 2oz copper pour if I'm only doing one side (meaning the entire bottom needs to be etched away!) Afterward, it will need several hours to recharge! Vertical tanks can theoretically utilize air bubble regeneration more efficiently than horizontal tanks, because the air bubbles travel a longer distance. But you can't put as many bubblers in a vertical tank, and cupric air-regeneration is slow, regardless! To maximize aeration, I use a bubble wand run from compressed air. The bubbles are extremely fine, versus poking holes in a tube. Running it this way, when my solution is too rich it will precipitate out large amounts of white precipitate (I presume some form of copper oxides) that I have never seen before! But it works good! I haven't done any scientific testing, but it seems to me that my tank recharges in about 4-6 hours. With a regular fish tank pump, it took at least overnight. This fine and copious amount of bubbles also alleviates another con to vertical etching. Some people have a hard time getting a vertical tank to etch, evenly. The bubbles can tend to focus on certain spots on the board. By flooding the entire tank with fine bubbles, etching occurs more evenly. Word of warning, here, if you try this! Do not let your compressor run all the way down! The tank only takes a couple psi before it will froth over, and regulators need a certain amount of positive pressure differential. If your tank pressure drops too low, the regulator will leak higher pressure air.... and when you come back to check on the board, it'll look like a leprechaun got sick on your patio after a weekend of partying. BTDT, so hopefully you don't have to! So make sure your compressor is on! It doesn't take much air, though. While running my tank, my small pancake compressor only turns on once every 1-2 hours.

Step 12:

In the end, a small vertical etch tank fits my needs fairly well. I rarely need more production capacity, and thus, I almost never actually drain the tank. Some minor maintenance is most all that's needed, and my hands and workplace stay clean!



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    very cool but did I miss something? How do you etch the image out? do you use crayon or something to prevent certain areas from being etched while others are?

    4 replies

    No, I used the toner transfer method. I'm not sure if crayon would work, but permanent marker does work pretty well with the right etchant.

    There are already several good websites and instructables that cover the basics of making a pcb, including choosing/making etchant, toner transfer method, UV exposure method, et al.

    Nice instructable! VERY Clever! I've got the 2L bottle on my desk and I'm going to give it a go! Thanks for sharing! =)

    @ ydeardorff - The toner transfer method involves printing an image onto a piece of paper (you can even use glossy magazine paper) with a laser printer, then transferring the image onto the copper using either a laminating machine or household iron. The areas that have the toner protect the areas under it from being etched during the etching process. You can use a green scour pad to remove the toner and Voila! You have a very nice circuit board! I DID want to add my two cents that I've been using the Pulsar products and ( ) and I've been VERY happy with the results! I don't have any more undercutting or botchy so-so areas of copper. I no have very few areas of the board that need touch-up after etching.

    I just figured I'd throw that in! I use the muriatic acid method and have been very happy with that too! Be-Gone GREEN SLUDGE!!!! ;-)

    I tried a ten pack of the Pulsar and been quite pleased with it. It's very good stuff. I still very slightly prefer PnP, although a large part of that is the cost. I'm about to order my third 100 pack of PnP. And I haven't found a place that sells dextrin paper at decent bulk rates.

    Pulsar pros: it's coated paper. It handles like coated paper. It's easy to cut and handle. PnP is plastic, so it curls, generates static cling, and attracts dust/hairs. It is much harder to cut. The easiest way I've found is with a very sharp knife over a cutting board.

    Pulsar pro: it transfers very easily. But if you don't transfer well, the transfer may be damaged by minimal handling or even while in the tank. So this isn't a huge pro for me. PnP takes a lot more heat and pressure to transfer. But once it's on, it's on for good.

    Pulsar pro: If your technique is bad, you still get great results. With PnP, too much heat and pressure can result in artifacts, where the blue sticks to the board, even where there's no toner. Dextrin paper can't produce artifacts.

    PnP pros: It's more stable for long-term handling and storage. If you get it wet/damp then you just have to let it dry off. If you get the dextrin paper wet, it messes up the coating and the backing can distort. And if you have a humid environment, you have to keep dextrin paper sealed. PnP has an additional layer over the toner. It seems to me like the traces come out just the tiniest bit sharper. And it's cheaper.

    So if you an learn how to use PnP effectively, it is basically the same thing, maybe just a hair better finished result for cheaper. But Dextrin paper is very nearly the same finished result and is much easier to achieve.

    have u tried there u should find wat u need . but it can take a few weeks to get it all in.

    You ever tried hydrochloric acid?

    To make your first batch, you mix the HCl and H2O2 together (the H2O2 adds the oxygen).  Next you throw in some copper wire over night until it is dark brown.  Now put your aquarium pump in the solution until it turns bright green.

    I bought a 2L bottle of HCl a few years ago.  I have still only used about 250 - 400 mL of it.  It cost $20NZD (About $15USD).  The H2O2 costed $2 a bottle, and I have used two bottles over the years.  You really only need one bottle, and it is for putting the initial oxygen in the solution.  After that you just need an aquarium pump.

    The cost means that I can have a nice large tank, have it really full of acid, and drop my board in.  The acid is completely re-usable.  In fact, it gets stronger with use (as long as you don't use the hydrogen peroxide to re-add the oxygen).

    6 replies

    Hehe, yeah. I've been involved in a little debate on the subject of etchants on another instructable.

    What you're describing is copper chloride etchant.

    Indeed, I use copper chloride, as it is the by product of etching with ferric chloride. My larger plexiglass tank is filled with about 1.5L of etchant. Roughly 1/2 to 2/3 of that starting volume was ferric chloride. The rest is copper chloride, stretched with muriatic acid over the years as needed to keep the concentration right.

    You're correct. If maintained, a batch of copper chloride will last forever. So will ferric chloride (plus copper chloride).

    I was under the impression that you had to dump ferric chloride after using it...  That was the whole reason I decided to use Copper Chloride.

    The topic is heavily debated here :-).  I myself have been the instigator a couple of times.

    The was an awfully large board you used.  Was that expensive..?  In NZ, boards are about $20NZD a pop.  300mmx300mm

    Ok, I'm about to start talking as if I'm an expert. But by no means take any of the following as gospel. I have just recently figured out some of this stuff, and I could be dead wrong on some aspects. But I've been using the same ferric chlroide for a couple years, now, and I learned a thing or 2 about it along the way.

    Etching with ferric chloride is almost exactly the same thing as etching with pure copper chloride.

    There is one difference. When copper chloride solution gets too concentrated, it simply stops etching. You add some HCl, and it's good to go, again.

    When ferric chloride gets too concentrated (I know you're not adding any additional ferric to the tank. I'm talking about the concentration of copper chloride + ferric chloride), the etching slows down and gross solid iron oxide particles start coming out of solution. If you do not maintain your tank, the etching will eventually stop, and a pile of iron oxide will settle on the bottom of the tank. Add some HCl and a bubbler, and this is reversed. You're good to go, again.

    I think a lot of people are under the impression that ferric is disposable, because it etches so darn good with such a small volume, at first. But they mixed it from powder, and there are no excess Cl- ions in solution! So check it out. It works awesome at first, because Fe(III)chloride etches copper. Copper goes into solution as copper chloride. Now Fe(II) chloride is left, and there aren't enough Cl- ions to allow it to revert back to Fe(III), even with a bubbler. Same goes for the copper chloride produced. Some can be reverted to green copper(II) chloride, but it won't be efficient unless you add some Cl- ions to the mix. So things slow does, and eventually iron oxide starts precipitating out. So people throw it away because it's slow and gross.

    Some people add table salt to ferric chloride baths. I prefer to use HCl. It speeds up the etching of copper chloride, but it also increases undercutting. So don't add too much.

    Check my facts here:

    If you look at the reactions, it clearly shows how you can make ferrous chloride from iron oxide and HCl.

    Furthermore, ferrous chloride turns into ferric chloride in the presence of chlorine.

    Final piece of the puzzle:
    Chlorine is produces by HCl + oxygen

    So In my experience, ferric is indefinitely recycleable with a little HCl and a bubbler, and in the last 15 minutes (just cuz you seem skeptical), I backed that up with research.

    That is very interesting :-D

    I was under the impression you didn't need to maintain Copper Chloride(II) with HCl.  I just added some the other night, as I needed more etchant to cover the board.  It then got very fast.  I hadn't done that for many, many boards.  That explains why it got so slow.  An etch would take up to an hour, or more!  The most recent one turned out great, and took about 30minutes.

    Thanks for doing all that research.  It is very interesting to hear that FeCl(III) is actually re-usable.  That makes life a whole lot cheaper for many people...  Although, I'm sure that CuCl(II) is cheaper.

    NP. I'm not good at chemistry, so I might be explaining things wrong. But the bottom line is that it does work. Think about it. Each time a cupric chloride etches a molecule of copper, you're left with 2x cuprous ions. They will naturally want to have 2 chloride ions to balance them out. So you will run out of chloride ions in your etchant! The resulting solution will be difficult to recharge and slow to etch. You'll also end up with some copper hydroxide, which will raise the pH of the tank, I think.

    FYI, excess HCl does NOT etch copper directly, in absense of peroxide. But it does enhance the etching speed of copper chloride solution, partly for reasons I have just explained. But from what I read, too much HCl can cause excessive lateral etching/undercutting. So be warned.

    1 hour etch? Wow, that's slow. I wonder what you're etching? If you're doing circuit boards, you will get cleaner edges if you speed up the etching with heat and agitation. A bubbler will work wonders, and will help to keep your etchant oxydized.

    There is one benefit of copper chloride besides cost. Cuprous chloride regenerates faster when exposed to oxygen than does ferrous chloride. But as long as you keep the solution with excess HCl, ferrous does regenerate with a bubbler. And every time you add muriatic acid, you are adding some aqueous chlorine, which speeds up the regeneration. ?? (again, not a chemist, but it does work)

    Either way, if you keep reusing ferric chloride etchant, you'll end up with mostly copper chloride. There ARE ways to get the copper chloride to precipitate out, if you want to repurify your ferric, though. Putting elemental iron in your tank with increase ferric content by addition of Fe ions and causing copper to precipitate out. Try putting a drop of your copper chloride etchant on a piece of iron/steel. Copper will plate out onto the object.

    waht is difference between vertical etch and normal?

    3 replies

    Well, you'd have to define "normal." For me, normal was dropping a pcb into a shallow tray, blasting it with a heat gun, and rocking it back and forth for 10-15 minutes.

    Pro's for vertical etching: 1. Space. I found out that as the size of your etchant tray gets bigger, it gets easier to accidentally spill etchant while you move it, even if you only keep a shallow amount in there. With a vertical tank, it's easy to move without having the skills of a waiter.
    2. Air agitation: can be done with a horizontal tray, too, with a bit more effort. But with a vertical tank, air agitation is always going to be more efficient for the same amount of bubbling.
    3. Heating: I've found that a vertical tank with a bubbler is easy to heat evenly, by putting a heater across the bottom of the tank.

    My main purpose was convenience. I wanted to flip a couple switches, put my board in, and then come back in 10 minutes... and a vertical etch tank seems like an elegant, space-saving solution. I'm liking it, so far.

    As I'm getting ready to etch a double-sided board, I just realized another benefit. I'm about to give a go at etching both sides at once!

    Awesome! Both sides cleanly etched in 10 min. They finished etching within a minute of each other.

    So clever, great work.