AP ratio and other things

[1dizzy1]

Hi, I am new here and have read most of hokes book. I have also watched a number of Steves' videos. I have used AuCl to dissolve gold and really like it. It is precipating now and I am going to try and get to decanting it this next week. My source for gold is silicon wafers. I use HF to remove the polyimide coating which exposes the gold, followed by the gold lifting off the underlying films, which HF attacks.
I used AR from Shorr which I feel is a waste. Takes too long. I used their nitric replacement sub-zero. I have had components soaling in solution for days, the gold finally removes but it takes considerable time. I would not recommend this solution to anyone.
I could probably just rinse the gold runners and melt, but to ensure a higher purity I dissolved it in HCl-Clorox and precipitated with Bodine which is Sodium Pyrosulfite. I have dark gold flakes still floating on the solution, which I will right now assume is gold. I will test after I decant.
I want to try Acid Peroxide now. From Steves' video it looked like a 2:1 ratio HCl:H2O2, correct?
Also I have 30% unstabilized H2O2, anyone have an idea what the ratio would translate to?
Also I want to try dropping a whole wafer into HCL-Clorox. I have seen and heard that HCl reacts violently with Al, which is a typical metal underlayment, along with copper. My question is does anyone have experience with this? I saw a video that used Al cubes in HCl with no reaction.
Thanks, 1dizzy1

 

[qst42know]

If by HF you mean hydrofluoric acid I hope you have read the MSDS and are using all required safety equipment. Nasty stuff.

I want to try Acid Peroxide now. From Steves' video it looked like a 2:1 ratio HCl:H2O2, correct?
Also I have 30% unstabilized H2O2, anyone have an idea what the ratio would translate to?

Acid peroxide is for dissolving copper alloy base metals and is usually made with 3% first aid disinfectant.

You could dissolve the aluminum with a dilute sodium hydroxide, wash thoroughly and then go on to HCL/Cl.

 

[1dizzy1]

Yes I mean Hydroflouric Acid. Yes it is nasty stuff, and I use semiconductor grade which is 49% then dilute to 100:1. I have worked in the semiconductor industry for 30 years. I have read the MSDS for every chemical I use and also have calcium gluconate on hand. I also fully gown when using acids and solvents.

Okay, I think I have some gold on copper, probably an interlevel metal present also. I have 3% H2O2 also for this. It is not copper because the color is incorrect. More gold in appearance. It is not tantulum because it doesn't dissolve in HF, I could drop it in H2O2 since tantulum isnt supposed to etch in peroxide. I have some wafers with tungsten over the gold, which I dont understand, but I can drop it into peroxide to remove the tungsten and see if the gold is lifted. Aluminum also etches in Peroxide.
I receive wafers from multiple IC manufacturers and all die are considered IP, so the companies are highly reluctant to discuss metal levels even though NDA's are in place.
I did some work with a gold refiner who had a hand held x-ray gun. Very nice since it reports in percentages the make-up of the material. Alas, we couldn't get it calibrated for silicon, but I had him test a piece of inconel I had and reported the percentages of metals.
I could send it all out to refiner, but they typically use a ball mill which destroys the silicon. And the silicon is valuable.
I have a ton of die mounted prior to packaging and the leads are gold, so I will try these in HCL-Clorox and maybe AP.

 

[qst42know]

What do you get for silicon, in what form, and in what quantities?

 

[1dizzy1]

I deal only in 11 9's purity which is IC grade silicon and p-type only. I can process whole and broken wafers to silicon substrate. Rs greater than .5 ohms/sq or higher. 300mm, 200mm, and 150mm sized wafers. Any smaller and the market price drops to the same as broken. I also deal in blue scrap which is difficult to handle and the market doesn't care for that thin of material. But if you get enough of it at the right price it is feasible to pull gold from them. I also deal with a company that is now starting to sputter platinum on their wafers, I am trying to buy their targets. They currently send them to a refiner back east.
Price and quantities I cant discuss on a public forum. Also the spot price changes daily.
I wish I had an easy way to precipitate copper and aluminum. You wouldnt believe how much of this I have just thrown away as part of the process. Also purity levels used for semiconductor is very high.

 

[Palladium]

Chris ( GSP ) use to strip factory reject ic packages for some companies in Silicone Valley you might ask him.

 

[1dizzy1]

Thanks Palladium, right now it is not a priority but I will keep this in mind.

Price of silicon for recycle into the solar market.

roughly 2010 prices:
Bare to silicon broken- $20.00-30.00/kg
Whole bare to silicon- 38.00-48.00/kg

2008 prices:

Bare to silicon broken: $300.00/kg
Whole bare to silicon: $350-400/kg

Prior to summer 2009 there was a shortage of silicon. Countries like Germany and Spain were subsidizing their Solar Market. Solar power was "fairly" inexpensive to persons in these countries. China is a huge power in developing Solar Energy. Major Silicon manufacturers have long term contracts to provide Silicon to the IC industry, probably 99% of their output.
As oil prices and energy prices increased solar power became more attractive. Only problem, not enough silicon to available to support this market. Effect: Silicon prices skyrocketed. For 2-3 years it was a bumper crop. Then Silicon manufacturers noted the market price and that they were missing out on huge sums of money. Everyone started bringing on extra capacity for this market, then in Summer 2009 the bottom fellout, government subsidies expired, the market was in trouble. In one week the price went from 400kg to 100kg, now it has settled to around 20-50kg. One silicon manufacturer boasted a 10yr contract to provide solar grade silicon at $200kg. When the bottom fell out guess who was renogiating their contract. LOL!