Dissolve lead and tin only!

[Evan2468WDWA]

there are dangers with hot caustic as with hot sulfuric.
it will eat organic matter away fast (skin is organic) best to try other methods or use all necessary personal safety gear.

Thanks for the warning. If I do it I'll be careful.

 

[necromancer]

great,

safety is something we all strive for.

it is one of the most important factors, it is always published on the top of all other methods for a good reason.

no one wants you to be harmed by the teachings here. there have been some scary stories posted in the past.

as one of the members has in there sig line.

"you cant fix stupid, stupid is forever"

 

[bswartzwelder]

One drop of NaOH to the eyes leads to permanent blindness. One drop of NaOH to blue jeans leads to a hole after they are washed. Anyone trying this needs proper safety gear.

 

[DNIndustry]

there is a process using Titanium and fluorboric acid i to remove tin/lead solder
very interesting.

 

[bswartzwelder]

This seems like it might be a good way to get rid of solder on circuit boards. I just don't know how it would work if the solder contains silver. Won't be trying this until after the spring thaw. Was wondering if there is any way to know how much solder could be dissolved in a gallon of this? Also, does this work quickly or should I put a bucket of it next to my AP bucket and sit back for a couple of days?

 

[MarcoP]

Yes interesting, but do you know how to dispose of it? I don't and if you do and would like to share would be a bonus. I stop my self from thinking about it because because it, availability and price.

There are other known ways to do it, pick one or more and study them in details.

Edit: as a general rule I always try to go for manual, mechanic or cold-acidic ways.

 

[bswartzwelder]

Earlier in the thread, a 50% solution of NaOH was recommended. It has been many years since I have had a chemistry class, but I have recently read that a 50% (w/v) solution is made by adding sufficient water to 50 grams of NaOH to bring it to 100 ml. A 50% (w/w) solution of NaOH is made by adding 50 grams of NaOH to 50 grams water.

I know I'm probably mixing apples and oranges, but doesn't the molecular weight of NaOH (40) enter into the equation somewhere? I'm going to have to do some serious digging to find my old college chemistry books. I guess my question is: When we mention a 50% solution, how do we know if we are talking of weight to weight ratio or weight to volume ratio?

 

[MarcoP]

I think, since NaOH's solubility in water is 1090g/L then I should use about 500g/L to produce a 50% concentration.

 

[solar_plasma]

% in chemistry is always weight percent, if nothing else is mentioned.

So 50% is 50g NaOH per 50g water.

Often it is easier to work with a concentration defined in mol: 1M NaOH would be 39,997g NaOH in 1 liter solution. About 12,5M NaOH would be 50wt%.

Why is it easier? Now, if you have used 1liter 12,5M NaOH dissolving tin and each mol of tin will use 2 mol NaOH, then you will have 6,25 mol tin or 741,9375g of tin in solution at the point of complete reaction, which ofcourse never will be reached in a slow reaction. Try to calculate this with wt%, - good luck :mrgreen:

So even you don't want to use sophistcated chemical formulas, it might be worth thinking in mol and you will be able to calculate stoichiometric amounts in your head.

 

[goldsilverpro]

http://www.handymath.com/cgi-bin/naohtble3.cgi?submit=Entry

 

[MarcoP]

Then, if I understand correctly, it needs to be used a saturated NaOH solution.

 

[g_axelsson]

http://www.handymath.com/cgi-bin/naohtble3.cgi?submit=Entry

Good link, I put it on the wiki. I'm going to check the rest of the calculators when my current work period is over. 80 hours in 8 days means not a lot of idle time, but a lot of money in the coffer.

:mrgreen:

Göran

 

[bswartzwelder]

Thanks for the replies. I purchased 8 pounds of NaOH some time ago. When it arrived, it was in 4 two pound bottles. Makes it rather easy to make a 50% solution. Two pounds of NaOH and 2 pounds of water. As a youngster, I was taught "a pints a pound the world around". Not necessarily true, but makes it easy for mixing things up. At any rate, I'm sure it will be accurate enough for removing lead and tin. I plan on using about an ounce or 2 of the 35% H2O2.

 

[solar_plasma]

Have all skin and whole face protected, this concentrated NaOH is etching really fast and deep, the first 10 seconds you even don't feel any burning. Therefafter you will already have a lifelong scar, where the drip has hit you.

 

[bswartzwelder]

Thank you solar_plasma. I am well aware of how nasty this stuff can be. Just putting the powder into cold water can bring the water to almost boiling. As I said in another post, 1 drop to the eyes brings instantaneous, permanent blindness. There just aren't too many ways to recover or refine precious metals without using something nasty. I used some last year and 1 drop landed on my shoes. Next time I got them wet, there was a nice sized hole in them.

 

[rajhlinux]

I know I'm reviving an old thread... but any how, the magic formula of 50% sodium hydroxide and "a little addition" of 30% hydrogen peroxide means exactly what?

I'm assuming 50% sodium hydroxide means:
50 grams of 99% of pure sodium hydroxide mixed in 50 grams of distilled water

Same logic goes for 30% hydrogen peroxide, can easily buy 30% hydrogen peroxide premade.

Now what is the proper mix ratio between the two?
When people here are saying to add this with that, I don't like to eyeball things, that how you start a fire by playing around with the cool guessing game with extremely acidic toxic chemicals...

Can someone who has experience tell me what the proper weight ratio of how many grams or ounces is needed of 50% sodium hydroxide mixed with how many grams or ounces of 30% hydrogen peroxide. (At least provide a legitimate estimate, no one here should play the guessing game of trial and error with such chemicals.)

Also does this "50% sodium hydroxide and 30% hydrogen peroxide" solution will attack the copper base?

Yes, I need to have the copper nice and clean and untouched since I am prototyping a PCB and I need to remove the "Tin" from the PCB which was used as an "etch resist".

Much appreciated, thanks.

 

[canedane]

Yes, I need to have the copper nice and clean and untouched since I am prototyping a PCB and I need to remove the "Tin" from the PCB which was used as an "etch resist".
This helps us a lot to understand what your goal is.
Hot lye (20%)and 80-90 celcius water(80%) will dissolve the solder, but it will take the paint on your board as well.
I do not remenber how fast it goes but i will guess 20-30 min.
I see no reason to use hydrogen peroxide.
Try a sample before you take your importen board.
Lye will destroy your eyes, skin and lungs, specially hot lye!
Take care.
Henrik.

 

[Lino1406]

The available nitric acid tin removers, remove tin moderately quickly as SnO2. The concentrations
are stepped between leaving a thin tin layer to bright copper surface

 

[geedigity]

When I manufactured circuit boards in the 1980's, I seem to remember using 30% to 35% hydrogen peroxide to remove the tin (not sure if there was lead also) coating that was placed over the copper to make traces. After etching the boards using an ammoniacal spray etching system, I soaked the boards in the H2O2 to remove the tin so only the clean copper traces remained. That is what I remember, but it was so long ago that possibly I am mistaken.