# ratio to mix up lye bath



## cableman (Apr 30, 2015)

I apologize to post such a simple question but I have been searching half a day and still can't find the correct process to prepare a lye bath to remove solder, tin, etc. from circuit boards. My camera is acting up but if you need a picture I may be able to manage one. These board came from satellite equipment and are definitely gold plated though probably not very thick. Even so it should give a decent yield for what it is. I need to know how much lye to mix with what other ingredients for a good lye bath because I don't want to have to battle solder and tin when I start recovering and processing further. Could someone please direct me to the correct information and I apologize in advance for bothering you with such a simple request but I am wary of using a hot lye bath and I want to make sure I do it correctly.


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## philddreamer (Apr 30, 2015)

Try searching "sodium hydroxide".
Here is some information,http://goldrefiningforum.com/phpBB3/viewtopic.php?f=53&t=6666&p=59485&hilit=solder+mask+hydroxide#p59478
Hope it helps!

Take care!

Phil


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## yar (Apr 30, 2015)

A lye bath will not remove solder. Also lye can blind you instantley so please use proper safety equipment.


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## acpeacemaker (Apr 30, 2015)

yar said:


> A lye bath will not remove solder. Also lye can blind you instantley so please use proper safety equipment.



A strong alkali can attack and eat away at some solder depending on the makeup. (Typically a softer solder) It can attack and dissolve tin, aluminum, and zinc. With these reactions it gives off hydrogen gas.

Andrew


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## FrugalRefiner (Apr 30, 2015)

ray (yar) is right. lye is used to remove "solder mask". To remove tin, most use a soak in HCl (hydrochloric acid / muriatic acid).

Dave


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## acpeacemaker (Apr 30, 2015)

I think my wording might have come off wrong, because I wasn't necessarily disagreeing.


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## acpeacemaker (Apr 30, 2015)

I should have mentioned that I was reading a pretty cool .PDF earlier about the electrodissolution of lead from PCB's with sodium hydroxide as a medium . It was used because lead sulfate wouldn't form in the solution. I know the topic was not on electro, but I think thats kinda where my thoughts were. Sorry again

Andrew


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## goldsilverpro (Apr 30, 2015)

An old standard tin or lead or tin/lead from copper stripper in the plating industry is electrolytic lye (sodium hydroxide, caustic soda - all essentially the same thing) solution. Not really feasible for circuit boards since you would have to make electrical contact to each solder area.


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## bswartzwelder (May 1, 2015)

Solder can be removed using a 50% mixture of Lye (NaOH) and Water. However, you must also add a catalyst of hydrogen peroxide. Standard 3% peroxide which is used when cleaning wounds will not work. It needs to be 30% or greater. As has been mentioned previously, lye will cause permanent, irreversible blindness instantly. Wear proper safety gear and keep kids and pets away.


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## goldsilverpro (May 1, 2015)

bswartzwelder said:


> Solder can be removed using a 50% mixture of Lye (NaOH) and Water. However, you must also add a catalyst of hydrogen peroxide. Standard 3% peroxide which is used when cleaning wounds will not work. It needs to be 30% or greater. As has been mentioned previously, lye will cause permanent, irreversible blindness instantly. Wear proper safety gear and keep kids and pets away.


I thought about that but wondered about potential dangers. A 50% caustic soda solution contains 6.25 pounds of NaOH per gallon. Available pre-mixed in 55 gallon drums. Very thick - like syrup. Dangerous to handle. If I were to use the peroxide, I would probably first try a weaker NaOH solution at room temp. In any case, be careful with this and do very small experiments first


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## rickbb (May 1, 2015)

It seems to me that a concentration of lye/peroxide strong enough to dissolve solder would be much more dangerous than a standard solution of HCL.


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## cableman (May 1, 2015)

Typed up my whole reply and lost it so here is the condensed version. The only reason I wanted to use a lye bath is because everywhere I looked someone was recommending it. I may have mislead you by my wording also. I only wanted to use the lye bath to remove the solder mask and any other impurities that could cause problems later on during the gold recovery process. I have read and read until it has been drilled into me to separate all possible metals prior to refining simply because it is easier to precipitate materials when there are none other present than the one you want. Also, I am not trying to do whole circuit boards. I have some small boards from satellite tv use that have some really good looking gold on them (will try to post pictures). I have already depopulated them with a heat gun and need to know the next step. I can use AP solution, sulphuric acid deplating cell, or any other method that is best. Thank you all for your responses and I am very grateful, especially if I can get by without using the lye bath; but I am set up to use it if I have to.


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## Barren Realms 007 (May 1, 2015)

rickbb said:


> It seems to me that a concentration of lye/peroxide strong enough to dissolve solder would be much more dangerous than a standard solution of HCL.




Yes it is.


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## Barren Realms 007 (May 1, 2015)

cableman said:


> Typed up my whole reply and lost it so here is the condensed version. The only reason I wanted to use a lye bath is because everywhere I looked someone was recommending it. I may have mislead you by my wording also. I only wanted to use the lye bath to remove the solder mask and any other impurities that could cause problems later on during the gold recovery process. I have read and read until it has been drilled into me to separate all possible metals prior to refining simply because it is easier to precipitate materials when there are none other present than the one you want. Also, I am not trying to do whole circuit boards. I have some small boards from satellite tv use that have some really good looking gold on them (will try to post pictures). I have already depopulated them with a heat gun and need to know the next step. I can use AP solution, sulphuric acid deplating cell, or any other method that is best. Thank you all for your responses and I am very grateful, especially if I can get by without using the lye bath; but I am set up to use it if I have to.



Because the plating is so thin on these types of boards you would be better off running them in AP.


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## bswartzwelder (May 1, 2015)

You originally led me to believe you wanted to remove solder. Perhaps I misunderstood your word for something other than what was meant. 

If all you want to do is remove the solder mask, then you don't need nearly as strong of a lye solution. I have removed solder mask previously and while I can't remember exactly how much lye was mixed with how much water. Do a search using removing solder mask and I'm sure you will get the right answer. In this instance, mixing up a solution which is precise is not needed. Much like making an AP solution. In that case, pour your HCl into the container you will be using and just pour in a little H2O2.

Even the weaker solutions of NaOH can be very dangerous to use. So the same safety warnings will still apply.


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## necromancer (May 1, 2015)

lye solution: for removing solder mask

slowly ad one *table spoon* of pure lye to 500 mililitres (2 cups) of *warm water* should be fine to start with. *(do not ad lye to boiling water)*

if not good enough, ad (slowly) one more teaspoon of pure lye

remember *SAFTEY FIRST*

lye will cause a reaction with the water and it will heat up. wear good googles or face shield, and gloves


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## necromancer (May 1, 2015)

also a great way to remove the components from small boards is:

get a stainless steel tray, in the tray put half a inch of clean sand over the bottom (no rocks in the sand)

heat the tray & sand then place the boards on the sand. it will melt most of the solder into the sand

pick up the boards with any type of steel tool (Pliers) and bang the board on its side, all components will fall off.

then use lye solution to remove the solder mask, then use the AP method to remove gold plating (foils)

do not use items that with will be ever used to cook food with, use items only for your recovery process (s)

mixing heavy metals with your food is *never* good practice.

you can remove the old components from the sand with a old metal spoon with holes in it or metal kitty litter scoop
after letting the sand cool you can remove the lead / tin (if not stuck to the pan) :shock:


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