November 26, 2020, 10:47:19 AM
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Topic: Help with PCB etchants  (Read 493 times)

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Offline shaheansar

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Help with PCB etchants
« on: October 24, 2020, 12:48:13 AM »
I'm looking into PCB etching,which requires ferric chloride

The issue is that where I live, only anhydrous ferric chloride is sold (Which is stupid. They don't even label it properly as anhydrous - got exposed to HCl fumes for 2-3 hours, thankfully the doctor found nothing abnormal with me and I got sent off with some anti allergy meds).
I've decided to switch to Sodium Persulphate following a discussion over here - https://www.eevblog.com/forum/beginners/etching-pcb-dealing-with-anhydrous-ferric-chloride/
What I'd like to know is if sodium persulphate is safe enough to be used at home without much ventilation?
Also, are there any decomposition issues I need to be aware of for a previous batch of the solution I made by adding anhydrous FeCl3 to tap water? (The mixture is in a plastic juice powder container and is 4-7 days old) I've heard this stuff can release chlorine gas and so I want to deal with it as cautiously as possible - maybe my worry is misplaced but it doesn't hurt to be cautious. I'm looking to dispose off these - both the 500gm jar I got off of Amazon as well as the mixed solution, unfortunately we Indians don't have much in the way of hazardous waste disposal - the only options I see are industry oriented and there's no way an individual like me could pay the fee for industrial waste disposal services. Either way, I'm looking to dispose this stuff away in as responsible a manner as possible.

Please keep in mind I will be using this etchant stuff at home. If you have any suggestions regarding alternatives, do mention them. If I can find it and it's safe enough, I will switch over to it.
If this isn't the proper place to ask these questions, please direct me to a place more suitable for these questions.

Offline chenbeier

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Re: Help with PCB etchants
« Reply #1 on: October 24, 2020, 03:19:39 AM »
You can destroy the ferrichloride by adding slowly baking soda or if available caustic soda solution. Ironhydroxide will be formed. This should be possible at home.
Persulfate is not so easy, need a reducer like bisulfite, before it can be waste. Also the copper has to be removed by precipitation with sodiumsulfide or hydroxide.

Offline shaheansar

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Re: Help with PCB etchants
« Reply #2 on: October 24, 2020, 05:50:05 AM »
You can destroy the ferrichloride by adding slowly baking soda or if available caustic soda solution. Ironhydroxide will be formed. This should be possible at home.
Persulfate is not so easy, need a reducer like bisulfite, before it can be waste. Also the copper has to be removed by precipitation with sodiumsulfide or hydroxide.

What about decomposition regarding anh. FeCl3 mixed with tap water? Should I be concerned or can I use the same method?

I've read that sodium persulphate can be disposed by first reacting the expended etchant with aluminum foil and then diluting the liquid part before throwing it away, and then just throwing the solid precipitate as normal trash. 

Far more important to me is the safety of sodium persulphate - as mentioned, I live in an apartment with my family. I don't want them exposed to any kind of fumes. That's the main reason I'm looking to move away from FeCl3 in the first place. It'd be nice to know from a chemist that sodium persulphate doesn't produce any noxious fumes outside of Oxygen (Which I'm assuming isn't released at concentrations to kill me)

Offline chenbeier

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Re: Help with PCB etchants
« Reply #3 on: October 24, 2020, 12:20:27 PM »
First to work with hazardous chemicals you should work under a hood or with open windows, to do it at home together with family is a crazy idea, you should avoid it. Or find another room where no other people have admittance.
The reaction of ironchloride and water creates HCl gas which is hazardous to the lung.
The reaction with aluminium and passionate creates soluble aluminium which is Poisson for fishes. So you make more waste. Who do PCB manufacturing needs a good waste water equipment. We have only one planet. So avoid also this. There are remanufactured boards with copper lines or dots . No chemicals reaction at all necessary.

https://www.reichelt.de/de/de/streifenraster-c7786.html?r=1

Offline shaheansar

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Re: Help with PCB etchants
« Reply #4 on: October 24, 2020, 12:37:40 PM »
First to work with hazardous chemicals you should work under a hood or with open windows, to do it at home together with family is a crazy idea, you should avoid it. Or find another room where no other people have admittance.
The reaction of ironchloride and water creates HCl gas which is hazardous to the lung.
The reaction with aluminium and passionate creates soluble aluminium which is Poisson for fishes. So you make more waste. Who do PCB manufacturing needs a good waste water equipment. We have only one planet. So avoid also this. There are remanufactured boards with copper lines or dots . No chemicals reaction at all necessary.

https://www.reichelt.de/de/de/streifenraster-c7786.html?r=1

While it is true that perfboards are available, they are only usable to an extent. The reason I'm looking to etch PCBs is very simple - modern parts don't come in a form that is solderable on these perfboards. You can look into LQFP packages or SOP packages. These are incredibly common in this day and age, and it can be difficult to work in electronics without wanting to prototype circuits involving these components - which are of course not usable on perfboards. I could send for PCBs to be made, but it's expensive where I live, and in the course of prototyping it's common for there to be 3-4 reruns to correct errors in layout or calculations - these expenses add up quickly, along with the required time (It normally takes 2 weeks for a board to be fabbed and shipped where I live, we're talking 2 months minimum for even trivial projects)

I will be of course working with open windows, and be going as far as reasonably possible to dispose off these chemicals (Regarding the method for sodium persulphate, it seems that I have made a mistake - the guide mentioned steel wool, not aluminum. That's an error on my part. Sorry for the misunderstanding), but a fume hood or any serious ventilation will be difficult. If there's no other choice, I will refrain from etching PCBs, but if I can do it in a responsible manner, I'd like to do it.

Offline chenbeier

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Re: Help with PCB etchants
« Reply #5 on: October 24, 2020, 02:15:18 PM »
With steel wool or any other iron source is a good idea, you can do it with it.
Good luck with your projects and your family.
Modern PCB are multilayer bords and got also the electrical connection through the holes (PTH) by chemical processes.  I worked 30 years in this industry, also in India Bangalore.

Offline shaheansar

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Re: Help with PCB etchants
« Reply #6 on: October 24, 2020, 03:13:38 PM »
Thank you for the help. I really appreciate it.
Have a good day!

Offline Borek

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Re: Help with PCB etchants
« Reply #7 on: October 24, 2020, 07:05:53 PM »
2 or 3 years ago I used sodium persulfate for prototyping simple PCBs at home, safe enough. Etching is actually the easiest part. Preparing PCBs for etching and drilling turned out to be much more challenging. I did it with thermotransfer and laser printer, and bough a fast Dremel fro drilling.

Then, I had no problem with utilization, as friend of mine works in a place which produces plenty of chemical waste and he can simply pour my used solutions into their tanks, otherwise it could be quite a challenge.
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Offline shaheansar

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Re: Help with PCB etchants
« Reply #8 on: October 25, 2020, 06:49:36 AM »
2 or 3 years ago I used sodium persulfate for prototyping simple PCBs at home, safe enough. Etching is actually the easiest part. Preparing PCBs for etching and drilling turned out to be much more challenging. I did it with thermotransfer and laser printer, and bough a fast Dremel fro drilling.

Then, I had no problem with utilization, as friend of mine works in a place which produces plenty of chemical waste and he can simply pour my used solutions into their tanks, otherwise it could be quite a challenge.

That's reassuring. What kind of PPE would I need when dealing with the powder?
Regarding the drilling - you can completely bypass that part if you stick to surface mount components.

Offline Borek

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Re: Help with PCB etchants
« Reply #9 on: October 25, 2020, 02:01:55 PM »
That's reassuring. What kind of PPE would I need when dealing with the powder?

As far as I am aware nothing more than typical glasses/gloves/lab coat.

Quote
Regarding the drilling - you can completely bypass that part if you stick to surface mount components.

Connectors and switches rarely come in the form of SMD, so at least in the devices I designed holes were quite difficult to avoid.
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Offline shaheansar

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Re: Help with PCB etchants
« Reply #10 on: October 26, 2020, 04:03:23 AM »
That's reassuring. What kind of PPE would I need when dealing with the powder?

As far as I am aware nothing more than typical glasses/gloves/lab coat.

Quote
Regarding the drilling - you can completely bypass that part if you stick to surface mount components.

Connectors and switches rarely come in the form of SMD, so at least in the devices I designed holes were quite difficult to avoid.

That is very nice to know. I was asking around on reddit as well and was told I could get a fatal asthma attack if I didn't use a dust mask or a glove box and so was planning on building one.

As for connectors and switches, you can find connectors as well as switches in SMD form. You can get these from the usual chinese sources (eBay, AliExpress) or a distributor if you want a datasheet. Tend to be cheaper in bulk too - although they are not very good for high current/power stuff. Through hole is the way to go there.

Offline Borek

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Re: Help with PCB etchants
« Reply #11 on: October 26, 2020, 04:28:10 AM »
was told I could get a fatal asthma attack if I didn't use a dust mask or a glove box and so was planning on building one.

Avoiding breathing powder is part of a standard precautions. Persulfate is sold in crystalline form and doesn't get easily powdered/airborne, so the risk of breathing dust is very small as long as you are reasonably careful.

It is sold here (with some kind of activator already added) in a granulated form, ready to dissolve. Just checked the leaflet and apart from gloves and glasses (or faceshield, which protects from splashes, but not from dust) no special requirements mentioned (and I live in EU, so the regulations are relatively strict).
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Offline chenbeier

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Re: Help with PCB etchants
« Reply #12 on: October 26, 2020, 10:44:56 AM »
Quote
    Regarding the drilling - you can completely bypass that part if you stick to surface mount components.
If you want only make single side boards in P&E yes. But at least boards have two sides and also components on both side and the two sides connected via PTH holes. More complicated are Multilayer boards which have tracks inside and also theses are connected via hole  some have blind vias.
Drilling is still needed.
And by the way : Pattern etching is done by CuCl2/ HCl/ H2O2 in closed chambers or NH3/ CuCl2 and the mentioned FeCl3

Persulfate is only used for desoxidation and etch back of drilled innerlayers.

Has something to do get the right track shape, almost square. Not to get railway shape tracks.

Offline Borek

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Re: Help with PCB etchants
« Reply #13 on: October 26, 2020, 04:28:56 PM »
Pattern etching is done by CuCl2/ HCl/ H2O2 in closed chambers or NH3/ CuCl2 and the mentioned FeCl3

Persulfate is only used for desoxidation and etch back of drilled innerlayers.

You are confusing industrial process with DIY environment.

Unless you are trying to say I did not made my PCBs using persulfate. That would be a bold statement.
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Offline chenbeier

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Re: Help with PCB etchants
« Reply #14 on: October 26, 2020, 05:37:12 PM »
Pattern etching is done by CuCl2/ HCl/ H2O2 in closed chambers or NH3/ CuCl2 and the mentioned FeCl3

Persulfate is only used for desoxidation and etch back of drilled innerlayers.

You are confusing industrial process with DIY environment.

Unless you are trying to say I did not made my PCBs using persulfate. That would be a bold statement.

I work in this industry since about 30 years, I only stated how it is done there.
What people do in DYI is another case.
I don't confuse anybody.  Where did I said you didn't made your boards using SPS.
Where should I know what you did. And my statement was adressed to the TES not to you Borek.
And drilling is necessary, if not single side boards made.

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