PCB Etching Tank - Do it yourself

[MP1]

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

 

[Fowkc]

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...

 

[MP1]

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

 

[Fowkc]

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?

 

[gogo2520]

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

 

[MP1]

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

 

[Pete9]

Hi guys I have been reading with interest the various methods of etching a board,I have tried most of them over the years and my final equipment is a plastic bucket that I put the board in etching face up ,pour in about 10mm of ferichloride stand it in some warm water and agitate,a swirling action is the best,I find the board will be etched in about 3-4 minutes. Total equipment cost 2$. Another tip if you are making a UV exposure box,use the UV tubes that are sold for Insect sappers,also sold for killing mosquitos, and seen in most butcher shops, these tubes are a fraction of the price,you can also get them in a U shape which will give a bigger area of light.If you are not conversant with wiring these tubes get an electrician to do it for you,or run them from a home made inverter.I do all my artwork with cad drawing,or in the case of good quality art work that is published copy and print on a inkjet printer ,5 minutes on my uv light box with presenstised board gives good results,with most  presensitised boards they supply a developer that is quite expensive ,try using sodium hydroxide 20 grams to 1 litre,very cheap,use at about 20degrees centigrade .  I printed the artwork for the 0-30volt power supply and had it etched and drilled in 4 hours.Hope this has been useful.       

 

[Fowkc]

I already etch lots of one off boards, current process is printing onto tracing paper, UV exposure, develop and etch in a plastic tray. This would be fine if I didn't share a house with four other guys. If it could go a bit quicker and be a bit more "self-contained", I'd get in the way less.

Thanks for all the help, sorry I was a bit insistent. I was sure it would work, I just like to understand why.

 

[Omni]

1. Slightly oversize a pyrex glass tray to the copper clad board.
2. Pour some common Ferric Chloride in the tray and place your board in the latter solution.
3. Every 20 min using your hand lift one side and allow the ferric to wave over the board.
4. After 1 hour your board should be complete (depending on size).
5. Using tongs remove board and flush with water, clean resist from PCB.
6. Pour the Ferric back into its bottle and use on the next project!
7. Clean tray with water and allow the faucet to run for 45 sec - min (flush pipes).

The above process has been used since the dawn of time, why try to reinvent the wheel.
Furthermore, when making a PCB at home remember it is an enjoyable hobby, time is not a big concern... 

 

[MP1]

The above process has been used since the dawn of time, why try to reinvent the wheel.

Electronic parts are much smaller than they were at the dawn of time. There are new requirements to make traces much closer and the parts have all gotten smaller. If you etch one of the newer footprints for one of the surface mount chips with closely spaced pins in a cold bath that will take an hour, it will undercut the traces and pads leaving a layout that is not useable. As technology changes, you must change with it. It is not just about the time.
Also note that the etchant is trying to get through your pattern as well as the copper. You will have to make sure your developing process was real good if you are going to subject it to an hour of etching. The longer you etch, the more light flaws from your original pattern will show up. With a faster etch, the solution is a little more forgiving of these flaws.

MP

 

[Omni]

MP,

I mean no disrespect concerning my statement.

The majority of hobbyist use the typical component size, i myself avoid using surface mount which would require more detail concerning PCB design along with the control method of etching.

Truthfully, i never expect to duplicate a printed circuit board manufacturer nor would i waste the money in trying.
Being able to make a decent PCB along with a pseudo tinning process is more than enough.
The few flaws that appear in the copper is a part of the process that give's the board a home made character. 

Like an old wooden floor that has a few squeaks.  ;D

 

[MP1]

No disrespect taken. Just pointing out that more precise methods of board manufacture that are available today are not really a re-inventing of the wheel. Whatever makes my work easier is ok with me.  ;D

MP

 

[Enrico1]

I've built one too.

But since i discovered Hydrogen Peroxide + Muriatic Acid, i just don't use it anymore.
You can find (at least here in italy) Hydrogen Peroxide 40% vol from airdressers, it is present in the products they use to make air shiny blonde.

I just lay the pcb in the plastic box and cover it with a small amount of muriatic acid (just enough to cover the pcb), then i squirt a small amount of air product and wait around 10 minutes, less if you give it a little shake sometimes.

I agree that this solution is far more dangerous than using ferric cloride, but if the right precautions are taken, you save a lot of money:

- No pcb tank nedeed, just a little plastic box (the mixture i mentioned above is very powerful in very little quantity)
- 10 minutes maximum etching time, even for large pcbs, i had perfect results in less than 10 minutes without eating nor shaking.