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billy

PCB Etching Tank - Do it yourself

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Hi Everybody !

I have started to build my own PCB Etching Tank based on the articles I am attaching here.

Soon I will publish all my efforts with photos and descriptions and I am hoping that it is going to be a cover story :) :) (if Mike likes it of course) !!!

EtchingTanks.zip

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That's nice, i was thinking to make my own etching unit also. It would be very nice if you post your experiences, the matterials you used and how you glue them. You can take photos of the entire construction sequence, step by step and finaly make a nice article that will be added under Articles section and why not to be a cover story! ;)

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Nice pdf file, Billy. Looks just like mine on a smaller scale. You might want to add a bit of a warning in your article about heat. The best etch is done with the highest heat of the etchant, with one exception. Above a certain temperature, the etchant chemicals become airborne. Eveything in the room with exposed metal will become rusted and you will be breathing unhealthy fumes. I am pretty sure this temperature is 105 deg. F but you might want to verify the exact temp before adding to the article. I have seen articles printed about this before, but I do not recall ever seeing a warning about the high temperature danger.

MP

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... You might want to add a bit of a warning in your article about heat. The best etch is done with the highest heat of the etchant, with one exception. Above a certain temperature, the etchant chemicals become airborne. Eveything in the room with exposed metal will become rusted and you will be breathing unhealthy fumes. I am pretty sure this temperature is 105 deg. F but you might want to verify the exact temp before adding to the article. I have seen articles printed about this before, but I do not recall ever seeing a warning about the high temperature danger.

MP



It seems like the etching tank is dangerous to built for beginner, any idea how to do simple etching without dealing with dangerous stuff

thanks in advance,

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My warning was about using a heater with the chemical. This causes it to change state when it gets too hot. You can etch without heat. It just takes longer.
But yes, you are correct, any process that uses a chemical to dissolve metal from a substrate has a certain amount of danger built in.

MP

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      hello everybody.
      Plexglass and the glue  is not  cheep so making a tank might cost more then just buying one.
  Some day I might buy a tank but right now I use tupperware cantainers for tanks, there cheep and if you shop around at yard sales or second hand stores you can  usual find one just the right size four under 2 bucks. I look for the one gallon jucie size that will hold a 6 by 8 board noproblem. And there heavy enough to handle a Aquarium heater too. I added a aquarium heater to mine  but it takes a long time to heat the etchent that way, so i pre heat the tank in another tub full of hot water first to get it warm then use the heater to keep it warm, 105F is warm enough. Some one on the web said he microwaved his Sulfuric acid to get it warm, ha he must not like his microware oven. If you get sulfuric acid over  130 F  it starts to evaperates and then sticks to anything that is cooler. like the outside of a  microware oven.  I wouldn't try everything you read on the web.
  Have fun gogo

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Guest Alun

You use sulphuric acid to etch PCBs?

I would say this is a bad idea as it presents a large safety hazard and even more so when it's warm as the sulpher dioxide given off can cause severe lung damage! :o

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    No  I use ferric chloride, I was just repeating what someone eles said about the microwave trick. I didn't think that was a good idea either.
    I like ferric chloride. Its easy to use and last a long time. Just have to be carefull not  to spill it. Makes a nasty stain on everything.
            have fun gogo

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Hi,
did this is a etching tank with a pressure air ? If this is it, then not only the heat well be a problem, heat will increase the temperature, and this will increased the evaporation. But the pressure air will have a more strong effect in this direction. You must have a very good ventilation to save your health.
Actually the feric chloride is not is not a very harmful, and not a dangerous as a nitrogen acid, but you must be carefull with a vapour. In normal temperaute, this is not a problem, but with aeration, and high temperature this may be a problem.
Have a some other way for etching the PCB. Different alkaline solution. Have one more very fast method, and not a very dangerous for hand .. but must have a good ventilation. H2O2 + HCl, use 30% H2O2 and 30% HCl in proportion 2:1 or 3:1. Must know that this solution is very unstable, you must made it before using. The solution is good to be cold. If you have old refrigerator, you can store the botle with a HCl and H2O2 in refrigerator. This is a very fast method, compare to concentrate nitrogen acid, but is more safety. Just remember, you will need a good ventilation.

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Hello
    Were can you buy H2O2, I live in the states and all hydrogen peroxide solutions I have seen is only 3% H2O2 and 97% water.
                                                gogo

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Hi,
I don't know where in the US you can buy this, has a different company that have a catalog for the chemical, but i don't know how you can by something from them. And they price is higer, becouse they material is very clear for laboratory analysis. I know that H2O2 is used in pharmacy industry. The H2O2 is used in hairdressing too, but they used 12% or 18%.

p.s. about this solution, this is not a suitable for the etching tank. You must use how many how you need for the board. When i used this solution use a flat tub. I put the board in to the tub, add H2O2 around 5-10 mm, and then add the HCl to the moment when start a fast reaction /you will see a many small bubble/.
Has a similar solution for industrial use, but with different proportion, 3 parts HCl and 1 part H2O2.

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Ferric Chloride is the safest of all these chemicals. When you start messing around with these other chemicals, you had better know something about science. Be careful to not cause an explosion or injure someone. Ferric Chloride does not need ventilation unless you exceed the heat range. Aeration does not cause it to require ventilation. You are not creating a gas since the ferric chloride is too heavy for this until you get the heat level up. Just use a heater with a thermostat and keep the temperature from going too hot. Boiling your boards in the solution is not going to etch them any faster than a nice warm solution with aeration.

MP

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Wow!  :o What were you using for aeration? I have had a pcb lab for more than 20 years and I have always used a low power air line from an air compressor connected to a manifold in the bottom of the tank that allows for even aeration throughout the tank. i.e.- even flow of tiny bubbles. Have never had a problem with fumes by using this method. Believe me, if I needed ventilation, it would not be for me to decide in a business. I would be required to add it by local regulation during inspections.
I think you are talking about etch systems which pressurize the etchant and spray it on the board instead of using the tank method. These systems are much faster than using a tank with simple aeration, but certainly have their added safety precautions. These pressurized systems produce a mist of etchant that is mixed with air. Obviously, this is going to give you an airborne mixture. This is also too dangerous for a hobbyist (in my opinion).

For those interested, the safety data sheet for Ferric Chloride, section 8 states the following:

SECTION 8 EXPOSURE CONTROL/PERSONAL PROTECTION

ENGINEERING CONTROLS/ VENTILATION
NORMAL GOOD ROOM VENTILATION SHOULD BE SUFFICIENT.

RESPIRATORY PROTECTION
N/A

EYE PROTECTION
RECOMMENDED SPLASHPROOF GOGGLES

HAND PROTECTION
RECOMMENDED IMPERVIOUS GLOVES e.g. NITRILE.

SKIN PROTECTION
RECOMMENDED IN FORM OF COVERALLS.

Always read the safety data sheet for any chemical when in doubt.

MP

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Hi,
presured air, from compresor, via reducer, in compresor tank the presure is around 6 bar, after reducer valve the presure is below 1 bar. But now i think taht temperature of air can be higir that room temperture becouse the compresion, and this may be is a reson for the voaporation.

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Hello All,

Just wanted to put my two cents in on this subject.  I didn't read all of the replys on this tank, so I hope I don't repeat too much!

I built this exact tank (12"x12"x1") 15 years ago with much success.  I used it with Photo Etching and standard copper etching with standard copper etchant.  The only problem is rub off transfers will come off if the heat is too high and bubbles are excessive.  Too low on eather one will cause excessive etching time.  I etched 25-50 hobby pcb's with it before I gave it away.

The artical states that MEK for the glue!  YES!!! but remember to scrape the cut edges of the plexi you plan to glue with a utility knife blade before gluing.  The edges must be as smooth and as close to clear as possibible before applying glue.  For those who don't know, the glue is as thin as water. You have to apply the glue to both edges and let it soften the plexi before mating.  Afterword, the soft glue seems to melt together, giving the appearence of a single piece of plastic.  Mine developed a small leak, so I used a sealant made for aquariums.

I didn't read the articals very well, but don't forget to drill as many holes in the board holder as possibible.  Too few holes will negate the bubbler on the bottom.

Just Food For Thought!

OGPIM

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I keep meaning to build myself an etch tank, but one thing eludes me:

People use aquarium heaters to heat the etchant, but all the aquarium heaters I've seen have a built-in thermostat that keeps the water at a maximum of about 32C, about 10-15 degrees too cool. How do you get around this, or is there something that I'm missing?

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The larger aquarium heaters will get hotter than this. I have actually had to watch out for going too hot in my tank. You do not want to heat up the mixture too much. Everything metal in the room will begin to rust....it is also not good to breath this. Your 32C heater is not real hot, but it is still hot enough to make the etching much faster. The other part of the equation is the aeration. The combination of a bubbler and a little heat makes a big difference.

MP

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OK, what sort of wattage heater should I be looking at then? It seems to be the case that a more powerful heater is meant to heat a larger volume of water (i.e. larger fish tank) to the same temperature (about 32C), rather than actually increase the temperature any further and kill your fish.

I can see how a more powerful heater would pump out more heat initially and then pretty quickly turn itself off as the etchant reached temperature, but it would still try and keep the temperature at about 32C.

Obviously I'm mistaken, since lots of people have done it and it works, but I'd like to understand why...

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All of the ones I have purchased have an adjustment on the top of them. You just set it according to needs. For etching, this is usually near the top of the scale. There is no temperature sensor inside these heaters. It is a metal strip that works like a mechanical thermostat. When the heat expands it enough, it triggers the switch. It is possible that you do not have enough bubbler movement in the tank to allow the heated etchent to move away from the heater and to the other side of the tank well enough. If you have poor circulation, the heat around the heater will turn it off prematurely, causing a lower overall temperature to the etchant. My tank can hold 4-  12" x 12" panels. I use 2 of the longest heaters I could find in the aquarium stores, I do not recall the wattage, but it was quite a jump from the wattage ratings of the smaller ones. I think your problem is with the internal thermostat. If you cannot get the adjustment to go high enough, you could open it up and modify the metal strip of the thermostat to cause it to stay on longer. But check for the circulation problem first. You don't want to cook the etchant near the heater just to get the rest of it warm.
Hope this information is helpful.

MP

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I haven't actually bought anything yet, I'm collecting information.

I'll only be etching one-off boards, so I won't have a lot of etchant to heat.

I'm still not sure about this, you say:

All of the ones I have purchased have an adjustment on the top of them. You just set it according to needs. For etching, this is usually near the top of the scale.


Well "top-of-the-scale" for the aquarium heaters I've seen is about 32C. Presumably you get your etchant hotter than that, so how do you do it? Do your heaters go higher than that temperature, or is it a result of heating much less liquid that they were actually designed to heat?

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hello Fowkc

    Hey guy if you just want to see how it works you don't need all this stuff. To etch one board, first is the transfer of the image to the board, once you have that any tank that the board will fit into will do. Hot water from a kitchen sink and a plastic bowl will work. Ferric Chloride dose good at 32C% or 100F%(same I think).
    When I did my first one  I bought a kit for about 14.00 dallors U.S. I got all the stuff ready and put on some plastic gloves and went to work. First thing I did is prewarm the Ferric Chloride in a double bath (plastic bowl inside a plastic bowl) hot water from the sink.
    Then the board went in, one hand on the inside bowl and rocked it back it back and forth, I could see the stuff work but I though it would happen faster. No it took 15 minutes, but it worked and I didn't need to buy all that stuff. It was my first board and it looks good.
  Oh I use press_on transfers that came with the kit.
        I now have a tank set up with the heater and air pump, works much faster, and use a laser iron-on
transfer. (office gloss paper).
        After of about two months of reading and another month of planning  I tryed this, I could do it, and now I make my own double sided boards. COOL.
                                          Have fun
                                            gogo

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Well "top-of-the-scale" for the aquarium heaters I've seen is about 32C. Presumably you get your etchant hotter than that, so how do you do it? Do your heaters go higher than that temperature, or is it a result of heating much less liquid that they were actually designed to heat?


It is actually a combination of smaller tank and more circulation from the bubbler. The smaller tank causes more efficiency of a small heater (more wattage per mass to heat up). Then you have the bubbler action which aerates and moves the water more than you would with an aquarium. Again small mass of water, more circulation. This will pull the heat away from the heater more efficiently so that the internal thermostat does not turn it off prematurely. Thus, the entire body gets more overall heat than what you would see in an aquarium with it's larger mass of water and poor circulation.

My larger etch tank holds approximately 17 to 18 liters of etchant. For this, I use two heaters. One on each side. Not that two heaters are required fo the temperature, but to keep things even from one side to the other. I also have a very aggressive bubbler system.
However, I have had one of the small hobbyist tanks in the past, like what you see at www.circuitspecialists.com and they are just as efficient with their small tank, fish aquarium heater and fish aquarium bubbler. It is all the same principal.

BTW: Gogo is correct. 32C will help the etch process considerably over cold etch. It is around 90F, but you don't want to get ferric too hot or it will vaporize and you will breath it.

MP

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