PCB etching, how care full do you need to be ?

[donnib]

Hi,
I have gathered all the needed parts to try starting the journey of etching my own PCB for the first time. I have few questions :

Info: I am going to use sodium persuflate as etchant.

1. How careful should i be with the board that has etchant on it like can i clean the board in a metal sink after i take it out ?
2. Is ok for sodium persuflate to get on wood, plastic ?
3. Can i use a fabric to wipe drops of sodium persuflate and what should i do with it afterwards ?
4. Can i leave the etchant in my etching tank ? As far as i can read i can, i just need to add more water that has evaporated but will it still work and so for how long ?

donnib

[jpanhalt]

Hi,
I have gathered all the needed parts to try starting the journey of etching my own PCB for the first time. I have few questions :

1. How careful should i be with the board that has etchant on it like can i clean the board in a metal sink after i take it out ?

If the sink is stainless steel, it will be OK.   The action of ferric chloride and other etchants on SS is primarily due to the chloride under acidic conditions.   Your products will contain no chloride.   The salt, sodium bisulfate (NaHSO4) is somewhat acidic; however, it is also used as a food additive.  Dissolved copper (e.g., Cu(I) and Cu(II) ) are somewhat more dangerous.

2. Is ok for sodium persuflate to get on wood, plastic ?

Plastic is generally pretty immune to it for short exposures.  My main concern would be possible oxidation over long periods of some reactive plastics.  Generally, I would not be concerned.   It is shipped most likely in a plastic bottle, right?  For wood, you might get more staining and oxidation.  One of the precautions is that strong persulfate can ignite paper.   However, your solutions will be in water and somewhat dilute, so staining would be my main concern.

3. Can i use a fabric to wipe drops of sodium persuflate and what should i do with it afterwards ?

See #2 answer

4. Can i leave the etchant in my etching tank ? As far as i can read i can, i just need to add more water that has evaporated but will it still work and so for how long ?

Yes, sodium persulfate is reasonably stable so long as there is nothing else in the tank that can be oxidized.   As for how long exactly.   I don't know.  There are too many variables.

ALL of the above responses apply to sodium persulfate.   Remember that once you etch your copper you will have copper sulfate also present.   That is not particularly regulated where I am (we put it in ponds and septic systems), but it may be regulated where you are. 

John

[KL27x]

Acid and base are relative to volume of water. To render harmless, dilution is your main weapon. Just keep a bucket of water handy, if you don't have running water nearby. That cloth/rag you use to wipe up the drops/spills is fine.... just dunk it and wring it out in the bucket of water if you don't want to replace it as often. If you leave the etchant on a dry rag, it will disintegrate fairly quickly.

It's not lead dust. It's not poison like cyanide. It's harmful because it is very acidic/basic. Don't get it in your eye and don't drink it. Don't spill it down the front of your pants.

[Berni]

The stuff is not particularly poisons or dangerous, just treat it as something that's not good for you and for nearby objects and you will be fine.

You can lift the board out of it with bare hands and such, but its best to do it with some tool to do that. In general around all of the chemicals used in etching its best to use plastic or glass containers for everything.

Just in general chemistry is  messy stuff (Tho you don't know messy until you tried ferric chloride etchant) so in general try to not get the stuff everywhere. If you are doing it on a dining table its a good idea to get a large plastic tray and do everything on that, having running water near by is also nice for washing off boards.

[raspberrypi]

Just dont drink it or pour it down the drain.

[ollihd]

Also remember to have good ventilation and or good respirator (for example 3M good ones).

[jpanhalt]

Also remember to have good ventilation and or good respirator (for example 3M good ones).

Why?

[Berni]

You only need that when working with HCl acid and peroxide. But for that id rather recommend you do it outside (a light breeze is also nice to blow the fumes away)

These persulfate based etching chemicals just give off oxygen when you use them. This is also the reason that the stuff makes explosives or rocket fuel if mixed with flammable things (But don't worry it doesn't just suddenly blow up, needs to be mixed well and ignited)

[Buriedcode]

Also should be noted that sodium persulfate (or persulphate) is often sold in anhydrous form.  This means it will warm up when added to water.  It is not a huge increase in temperature but I used to use 40C water and the temperature did climb a fair bit.

Great stuff though, smells very faintly of bleach, but isn't actually bleach and gives off Oxygen.  I've made all my DIY PCB's using this etchant and its generally easy to handle, doesn't 'over-etch' with laser-printer method, and lasts a while.  Just remember to warm it before use as this greatly speeds up etching times.  At room temperature, especially as its getting spent (turns more and more blue from the copper) it can take ages to etch.