calling on all chemists

[Thunderchild]

ok so I'm setting up for pcb etching using HCL and hydrogen peroxide, just to make sure (as I'm going to end up with cupride cloride anyhow and keep regenerating it) I put a peice of plain copper board in and not a lot happened. However I mixed up the hydrogen peroxide and the HCl with an air stone in the tank and it seems that the mix has been eating the air stone and making a lot of soapy type bubbles, now that I've removed it it looks a bit clearer although i have small particles of air stone floating around. has the mix been effected or will it still etch ok ?

I may have to just start from scratch with HCl and some coper and directly make cupride cloride

 

[jpanhalt]

One of the primary uses of HCl is to etch concrete. It is not surprising it attacked your air stone. Most plastics (not nylon) are quite stable to HCl. I use a bubbler called "Bubble Wall" from Penn-Plax. It was available at my local pet shop. They are light blue and are stable to cupric chloride and HCl.

What effect will the dissolved "stone" have on your board? I have no idea, probably none. However, the stone probably contained calcium and magnesium salts. Those are the ingredients in hard water. Thus, although the board may etch, you may be left with a scum on it. For the cost of these materials, I would throw it all out and start over.

John

 

[Thunderchild]

Hi John

You have echoed my fears and thank you for your advice, I'm in the process of creating cupride cloride directly by dumping copper in acid and letting it disolve and then adding the rest of the acid. Will take a few days but should do the trick

 

[JimB]

I'm in the process of creating cupride cloride directly by dumping copper in acid and letting it disolve and then adding the rest of the acid.

Have I missed something here, why do you want to make Cupric Chloride?

JimB

 

[Pommie]

I don't know this method but it appears to be using the peroxide to enhance the action of the Hydrochloric acid. I've read somewhere that the mixture can be regenerated by bubbling air through it. I'm extremely skeptical about this, peroxides do not just form, they need lot's of energy.

Anyway, if you get this to work I would be interested in a write up. I can't see how it can possibly work but am keeping an open mind.

Mike.

 

[jpanhalt]

Hi John

You have echoed my fears and thank you for your advice, I'm in the process of creating cupride cloride directly by dumping copper in acid and letting it disolve and then adding the rest of the acid. Will take a few days but should do the trick

Copper will dissolve very slowly in just HCl. You need to add hydrogen peroxide or bubble air or ozone through the acid to get it to dissolve the copper. The solution should be a brilliant green. If it is at all "muddy" or brownish, you do not have enough oxidizer (peroxide, ozone, oxygen) present. The brownish color is due to cuprous oxide (Cu2O). Peroxide and ozone are efficient oxidizers. Oxygen will work, but is slower. In my tank, for example, after etching one 3X4" board of 1 oz. copper (less than 50% removed), I have to bubble air overnight (12 to 16 h)to regenerate the bath. That should give you an idea of how slow air is as an oxidizer.

To test the color, you can place a small drop on a piece of glass and view against a white background (probably best way) or onto a piece of white paper towel. Paper towels may have residual oxidizers in them from their manufacture, so they may mask a little muddiness.

I would recommend you proceed to use peroxide as indicated in your first post until you get the amount of cupric chloride you want. Otherwise, it will be a very slow process.

John

 

[Thunderchild]

from what I've read: **broken link removed**

you can use the HCl peroxide to etch the board, in etching the copper (reating with the copper) it produces Acid Cupric Chloride which will also continue to etch, this in turn eventually turns into something else turning from a light green to dark brown. at this point the solution is "saturated" but blubling air through it reverses the effect and makes it light green again and you can re etch

 

[jpanhalt]

That is exactly what I was saying. Look at Figure 5 in the link you provide. The brown "something else" is due to cuprous (Cu+1) ion. I called it cuprous oxide speaking very loosely. It is almost certainly a complex and I did not assume you wanted to get into the chemistry that deeply.

Two atoms of cuprous ion are formed from one atom each of cupric ion and copper. Whether it is as the chloride, oxide, or some complex is unimportant in terms of calculating the stoichiometry and how much acid and oxidizer you need to add to regenerate the etching bath.

John

 

[Thunderchild]

John, I'm not good in chemistry at all hence trying to follow instructions scruposely

 

[Sceadwian]

Mind you pouring these spent chemicals down the drain is illegal, and if you have a septic system don't even think about it, does a pretty good number on plants. It needs to be neutralized the solids need to be precipitated out and disposed of legally.

 

[Thunderchild]

yes thats why I've tried to opted for the regenerable method, however I'm not sure now what to do with the 4 odd litres i have oh peroxide + HCl + concrete from the air stone

 

[shortbus=]

Quote-
Have I missed something here, why do you want to make Cupric Chloride?

"jimb"


Quote-
Anyway, if you get this to work I would be interested in a write up. I can't see how it can possibly work but am keeping an open mind.
"mike"

Quote-
Etching with Air Regenerated Acid Cupric Chloride "Thunderchild"


this is the main way the guys at "HomebrewPCBs" a YAHOO GROUPS
forum do there etching. after the cupric chloride is generated you never through it out- just add new peroxide and etch.

adam seychell, that has the site Thunderchild posted is the one that introduced it there. he makes some amazing boards.

cary

 

[jpanhalt]

I have been using cupric chloride with air regeneration for about a year. It seems a little touchy at the end to avoid over etching, and the tracts are not quite as sharp as with ferric chloride. The difference is slight. Then again, it lasts forever.

Here are two additional documents. The Chemcut article has a little more comparative data than Seychell's. The second pdf is my personal recipe. It is very rough, and there are no guarantees. I chose to start with cupric oxide as it is available, cheap, and a whole lot easier than starting with copper and hydrogen peroxide. I only have to regenerate the amount that is used and use air for that.

John

View attachment Cupric-Chloride.pdf

View attachment Cupric Etch Bath Developmen.pdf

 

[Sceadwian]

4 liters isn't much. Neutralize the PH to about 9 or so using caustic soda, baking soda should work but it'll make the sludge MUCH more voluminous and take a lot more to neutralize the acid, mix it very well during the neutralization process till you get the 9PH (roughly) 7-10 should be okay. PH tape is easily purchased and cheap. Once you have the PH at around 9, let it sit for about 2-4 hours, then either slowly siphon or pour off the remaining liquid avoiding pouring off the sludge that has formed at the bottom, this needs to be done without agitating the solution. The sludge should be evaporation dried (put it in the sun) the sludge while not ideally can be safely sent to a land fill IE the trash, the remaining solution should be diluted as much as possible and sent down the sewer. I'd recommend mixing 1 cup of precipitated solution in a gallon container with the remainder being water, shake it well, dump it down the drain just before a shower. If you take a shower every day it'll be gone in three months, you'll have left some sludgy metal residue in a landfill somewhere that will require an extreme acid or caustic to cause it to become mobile again and enter the environment as an active pollutant, and the remaining solution you sent down the drain will have been so far diluted that it's only marginally worse than environmental norms. If you wanna go the extra mile, do what the pros do, evaporate the sludge down till it's nearly a completely dry powder, mix it with a bucket of concrete and toss it in a dump. What little metal is left in the sludge is then evenly dispersed in a concrete block which will slowly dissolve over a few hundred years unless it's left in a neutral inactive environment in which case it'll last a few thousand years. So it even dillutes the possible re-entrance of the metals into the environment.

One important thing to know when you're dealing with concentrated solutions of anything is that EVERY SINGLE last one of those compounds came from raw materials provided by the earth, they're just concentrated and processed. Proper intelligent dilution and reintroduction to the environment of said materials produces the least harm, to both us and the environment.

Large scale metal processing applications tend to send the sludge through a further refining operation to recoup the spent materials, but the scale has to be very large to make things like that practical, usually it's just immobilized in concrete as aggregate and tossed.

The neutralization/precipitation process is used by every metal finishing job shop in the known universe =).

As a side note, after neutralization adding a small amount (not sure how much) of ferric chloride will help precipitate the metals out of the solution. You have to maintain PH neutrality after you add the ferric chloride. Basically the iron is heavy it helps to coagulate and weigh down the lighter metals, dissolved aluminum solution is also sometimes used because it provides very active nucleation sites for other metals, combined with ferric chloride to weigh it down and mixed with a polymer (food grade polymers are available at chemical suppliers) you end up with a heavy dense sludge, and the least possible amount of dissolved/active/ionic metals in the solution.

The EPA standards for some heavy metals in job shop effluent is so high that it's actually higher than for spring water so I think they know what they're doing =)
Everyone in this forum that uses an etching solution or concentrated chemicals of any kind should read this post thoroughly. It's the thousands of people willy nilly dumping this stuff down the drain that's the problem, and the above prescribed method of neutralization, precipitation and immobilization is the least any responsible person should go through. And all it takes is another acid, or base (depending on the solution) some PH tape and a little bit of time for the most basic method. Copper in particularly bad for plant life in high concentrations, heavier metals are bad for pretty much everything, and it builds up over time, hence the importance of removing as much as possible and dilluting the rest as much as possible.

 

[vishal8415]

Add Nitric Acid to Cupric Chloride

Add Nitric Acid to fasten the Cupric Chloride Process instead of adding any kind of peroxide, oxygen or ozone but that also within limit.

Adding the Nitric Acid to any metal will fasten the process of dissolving.

I do manufacture the same industrially.

vishal

 

[jpanhalt]

I do manufacture the same industrially.

vishal

Of course nitric acid will hasten the process. Nitric acid plus HCl in high concentrations will even dissolve gold (common name = aqua regia).

The OP wanted an etchant that can be completely regenerated. Can you provide any reference for using nitric acid in PCB manufacture that meets that need?

Finally, we do not know what resist the OP is planning to use. I have found photoresists to be more sensitive to attack by some etchants than toner transfer appears to be.

You should also consult this link before mixing nitric acid and hydrogen peroxide. The brown fumes fro nitric acid are not good for you.

https://www.electro-tech-online.com/custompdfs/2009/10/HH-1064.pdf

John

 

[vishal8415]

No Idea for etchant

Hello John,

At present I don't have any idea for etchant of PCB.

But If you seach in Google with the title "etching with nitric acid in pcb"

you will find videos and websites.

Vishal

 

[jpanhalt]

Hello John,

At present I don't have any idea for etchant of PCB.

Vishal

So, I take it that you are a manufacturer of nitric acid?

John

 

[Pommie]

It's not a good idea to mix peroxides with anything unless you are aware of the resultant compound. Similar for Nitric Acid. Both can form highly explosive compounds and in the case of peroxide, highly unstable.

In fact, I think peroxides are a watched chemical in the UK. Can anyone in the UK still get peroxide?

Mike.

 

[shortbus=]

I have been using cupric chloride with air regeneration for about a year. It seems a little touchy at the end to avoid over etching, and the tracts are not quite as sharp as with ferric chloride. The difference is slight. Then again, it lasts forever.

John


as far as the track sharpness if i remember right, they are now using a cheap foam paint brush to apply the cupric chloride instead of submerging the board.you just keep brushing over the board and that helps remove the dissolved copper making the etch work faster.

in commercial board manufacture the use a spray bath to apply the etchant
(cupric chloride, i think) to keep the dissolved solids moving.

cary