Thinking of a small-scale incinerator for pyrolyzing ICs

[skippy]

I found that a single black pyrolyzed IC when put into a spoon with molten sodium hydroxide dissolved the IC apart quite well. I don't know yet if it is practical, and also the silicon chip started fizzing and burning in the sodium hydroxide, so it may be too violent when scaled up to a volume of ICs.

I speculate the hydroxide dissolves the glass filler material and you are left with some carbon, gold wire and legs. I also don't know if the sodium hydroxide would dissolve gold or silver, which could be a problem if it does. I think this idea has potential for higher value material like NS bridges and such.

Note: I did this with a single chip, I advise extreme caution in performing or scaling up this experiment. Sodium hydroxide when molten goes off as a vapor into the air even when it isn't bubbling, which is bad. Silicon and possibly other metals in the chip react very exothermically! This is possibly more dangerous than the wet ashing... but I thought it was still worth bringing up for discussion.

 

[Smack]

Check out this silicon.
http://www.youtube.com/watch?v=ZMByI4s-D-Y

 

[skippy]

I've got a bit of a pigs breakfast of stuff I sheared off boards, resistors, capacitor, small chips, pins etc.
After pyrolyzing it, I was surprised how tough the little chips still were, they wouldn't pulverize very well.
I took the whole mess of stuff, and reacted it with aqueous sodium hydroxide. The sodium hydroxide was very busy vigorously attacking many base metals.
After it slowed down, I poured off as much liquid as I could, added more sodium hydroxide and proceeded to heat it in a stainless pot on a burner outside.
I heated the pot for an hour, driving off all the water and continued heating the mix. I'm not sure if the sodium hydroxide became molten throughout, but I believe that the sodium hydroxide got quite hot throughout, but there wasn't enough sodium hydroxide to fluidize the whole mass. After letting the mix cool, I carefully added water and simmered it overnight on a hotplate. Most of the IC packages are gone now and the few left are quite mushy. I just wanted to confirm my idea works here and maybe it will be useful for those having a hard time getting their chips to incinerate throughout. It doesn't even use much sodium hydroxide, but I can't put a ratio on it yet because I didn't weigh anything, and my material was so varied. And yes, don't forget it is quite dangerous. Hot sodium hyrdroxide will blind you, disfigure you, the fumes will attack your lungs. I think the best way to minimize danger is to maintain distance outdoors, or perform in a hood. All the usual stuff about gloves and glasses apply. Fuming was worst in the initial treatment with the sodium hydroxide solution, with the solution bubbling and wafting off substantial caustic mist. The production of hydrogen was very vigorous so that might be another danger to consider. Depending on concentration of NaOH, temperature, etc the reaction could become too strong, so caution is urged if anyone wants to use this.

The solution afterwards will have a lot of lead and tin in it , which will have to be dealt with. The solution could probably be used to neutralize acid in other waste solutions, although I don't know how easy the silica will fall out when the ph is adjusted. I hope it doesn't pick up too much silver, because that might present complications for recovery. Any thoughts appreciated and welcomed.