In general, electronic waste is processed by:
1. Removing high grade components for labor-intensive processing.
2. Depopulating the printed circuit board.
3. Separating the copper, usually by incineration.
I've been doing some experiments with step #2 in this process. By using various dilutions of so-called "Basic Piranha" solution (sodium or potassium hydroxide in water, plus strong hydrogen peroxide), the solder is removed, with little effect on other metals except aluminum, which is also removed. The photo below shows that the green solder mask is removed, and you can see that nearly all the solder is gone from the Pentium 4 CPU. The RAM chips and other surface mounted components come off easily with a little pressure from a spatula.
The finger connectors show that some of the gold was dissolved by the process, so this is an indication to remove gold-rich pieces first, and to use a weaker dilution.
SAFETY: Sodium hydroxide (lye, caustic soda) is one of the more hazardous chemicals we use. It forms a corrosive mist when added to water which is easily inhaled. It is particularly harmful to the eyes. Adding hydrogen peroxide increases this danger considerably, so the smallest amount possible should be used.
The waste water from this procedure contains lead, which is a cumulative toxin. It may also contain silver, so it should be saved, concentrated and smelted.
So it looks like boards might be depopulated with lye+peroxide. In any case this is a good way to remove solder before incineration, cutting down on lead fumes.
* * *
One thing that struck me about the magazine article was the information that hard drive platters contain aluminum + magnesium. Aha -- finally a use for these things. There is a very useful alloy called Zamak or ZA-27, that is made from 28% aluminum, 70% zinc, 2% copper, and 0.02% magnesium. The magnesium is present in a small quantity and yet it is vital to the performance of the alloy. Now here is a source. You can fill your melter with aluminum heat sinks, zinc wheel weights, and a platter and a bit of wire, and what you'll get after it's all melted in a very castable (at 530 degrees C.), low-temperature melting alloy (i.e. a pot metal) that has metallurgical characteristics close to those of mild steel.
For more details, see
www.matweb.com
What can you make from it? Clamps for your glassware! Most glassware clamps are made from pot metal, plated with nickel. A kettle clamp will cost over $100.
You can nickel plate without electricity as follows:
Add:
nickel chloride, 5 oz/gal or 30 gm/L.
sodium hypophosphite, 1.5 oz/gal or 10 gm/L.
sodium acetate, 8 oz/gal or 50 gm/L.
Use at a temperature of 88 - 94 degrees Celsius. Agitate occasionally.
Keep the pH between 4 and 6 with sodium hydroxide.
Add small amount of stock as it is used up.
Rate of deposition: 15 microns per hour. That's 600 microinches.
The hardness can be almost doubled by heat treating.
Note: This formula is for plating on iron. I haven't tried it in zinc/aluminum alloy.
