# Best Method to Remove Gold From Silicon Wafers



## kevscott (May 21, 2015)

Hi,

I'm new here, please take it easy on me if this topic has been covered.

I have a few hundred whole & partially picked 6" Silicon Wafers, with Gold, Silver as well as Platinum on them, a vast majority have already been cleaved & on wafer tape

I am interested to learn the best process to remove the metals from the different types of wafers & best way to remove the chips from the tape?

Other than the obvious would there be any extra safety precautions I should use? 

I have checked out UW-860G from Taiwan, but, hesitant simply due to unknown costs for me to import it into Canada, shipping, plus duty, plus tax on shipping as well as tax on duty.

Any feedback would be greatly appreciated 

Thank you in advance

Kevin

Update: 

I now have almost 161pounds of gold wafers, each wafer with the tape weighs 27g, if my math is correct, I have about 2700 wafers. 

I am unable to upload pics because as I was uploading the site rejected the pic saying it was a potential attack ???
Any help uploading these pics would be greatly be appreciated

.


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## goldscraphobby (May 21, 2015)

I have done some but they only had a layer of gold, no silver or other PM. I just used HCl and chlorox until the thin layer of gold was removed.


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## goldsilverpro (May 21, 2015)

Is the back of those covered with gold? If not, I can't see how there would be much value. If they are covered with gold, I would probably use aqua regia (AR), if cyanide is out of the question. AR won't get much of the silver (too little money in this situation - so, who cares?) but it will get Au and Pt. 

To repeat, if the back of these aren't coated with gold, I would guess that they're not worth processing, although I haven't seen them. Photos on both sides?


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## richard2013 (May 21, 2015)

As per electronic industry record gold layer thickness will only be around 1 micro m so we may need at least 40 pounds and up for it to be worth processing. :mrgreen:


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## goldsilverpro (May 21, 2015)

richard2013 said:


> As per electronic industry record gold layer thickness will only be around 1 micro m so we may need at least 40 pounds and up for it to be worth processing. :mrgreen:


Where is the gold? On the circuit side or on the back? Photos? What would 40# be worth, in your estimation? One cm2 of 1 micron gold is worth about $0.08. I would expect any gold that is present would be yellow. In other words, I would think you could see it. Can you see yellow gold?

Photos - both sides?


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## acpeacemaker (May 21, 2015)

:?: http://m.ebay.com/itm/like/321045228380?lpid=82&chn=ps&ul_ref=http%253A%252F%252Frover.ebay.com%252Frover%252F1%252F711-117182-37290-0%252F2%253Fmtid%253D1588%2526kwid%253D1%2526crlp%253D53601919689_324272%2526itemid%253D321045228380%2526targetid%253D74194843147%2526rpc%253D0.17%2526rpc_upld_id%253D49229%2526rlsatarget%253D%2526device%253Dm%2526mpre%253Dhttp%25253A%25252F%25252Fwww.ebay.com%25252Fitm%25252Flike%25252F321045228380%25253Flpid%25253D82%252526chn%25253Dps%2526adtype%253Dpla%2526gclid%253DCNrkpbay1MUCFQqIaQodwKgAWA%2526srcrot%253D711-117182-37290-0%2526rvr_id%253D834492948787&ul_ref=http%3A%2F%2Frover.ebay.com%2Frover%2F1%2F711-117182-37290-0%2F2%3Fmtid%3D1588%26kwid%3D1%26crlp%3D53601919689_324272%26itemid%3D321045228380%26targetid%3D74194843147%26rpc%3D0.17%26rpc_upld_id%3D49229%26rlsatarget%3D%26device%3Dm%26mpre%3Dhttp%253A%252F%252Fwww.ebay.com%252Fitm%252Flike%252F321045228380%253Flpid%253D82%2526chn%253Dps%26adtype%3Dpla%26gclid%3DCNrkpbay1MUCFQqIaQodwKgAWA%26srcrot%3D711-117182-37290-0%26rvr_id%3D834492948787&_mwBanner=1


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## goldsilverpro (May 21, 2015)

acpeacemaker said:


> :?: http://m.ebay.com/itm/like/321045228380?lpid=82&chn=ps&ul_ref=http%253A%252F%252Frover.ebay.com%252Frover%252F1%252F711-117182-37290-0%252F2%253Fmtid%253D1588%2526kwid%253D1%2526crlp%253D53601919689_324272%2526itemid%253D321045228380%2526targetid%253D74194843147%2526rpc%253D0.17%2526rpc_upld_id%253D49229%2526rlsatarget%253D%2526device%253Dm%2526mpre%253Dhttp%25253A%25252F%25252Fwww.ebay.com%25252Fitm%25252Flike%25252F321045228380%25253Flpid%25253D82%252526chn%25253Dps%2526adtype%253Dpla%2526gclid%253DCNrkpbay1MUCFQqIaQodwKgAWA%2526srcrot%253D711-117182-37290-0%2526rvr_id%253D834492948787&ul_ref=http%3A%2F%2Frover.ebay.com%2Frover%2F1%2F711-117182-37290-0%2F2%3Fmtid%3D1588%26kwid%3D1%26crlp%3D53601919689_324272%26itemid%3D321045228380%26targetid%3D74194843147%26rpc%3D0.17%26rpc_upld_id%3D49229%26rlsatarget%3D%26device%3Dm%26mpre%3Dhttp%253A%252F%252Fwww.ebay.com%252Fitm%252Flike%252F321045228380%253Flpid%253D82%2526chn%253Dps%26adtype%3Dpla%26gclid%3DCNrkpbay1MUCFQqIaQodwKgAWA%26srcrot%3D711-117182-37290-0%26rvr_id%3D834492948787&_mwBanner=1


I know what a Si wafer looks like. I've processed them by the drum full. I want to see what his wafers look like. If there's gold, you can see it.


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## acpeacemaker (May 22, 2015)

I was curious if that's what you guys were referring to was all.


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## goldsilverpro (May 22, 2015)

acpeacemaker said:


> I was curious if that's what you guys were referring to was all.


Sorry. Yes, on your link is an example of a silicon wafer, with circuitry applied. The individual chips are then cut and separated.


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## acpeacemaker (May 22, 2015)

goldsilverpro said:


> acpeacemaker said:
> 
> 
> > I was curious if that's what you guys were referring to was all.
> ...



No problem Chris  
My commons were au,ag, and occasionally some pd. I don't think I ran into pt much, if any.

Andrew


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## richard2013 (May 22, 2015)

goldsilverpro said:


> richard2013 said:
> 
> 
> > As per electronic industry record gold layer thickness will only be around 1 micro m so we may need at least 40 pounds and up for it to be worth processing. :mrgreen:
> ...



Sorry goldsilverpro I have just read from one website before that 1 micron is the ideal thinkness, but thickness varies from different company innovation some even using .3 micron or less, it will have adhesion plating also using titanium or chromium under the Au. Au is a protective layer for the silicon glass and connecting point for bond wires too. Please see details in these link below.
http://www.azonano.com/article.aspx?ArticleID=3458


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## goldscraphobby (May 22, 2015)

The pieces I have are gold on both sides, one side is etched to the pattern needed. These were used in RF circuits so it is only patterned gold, bottom side was all gold for grounding to the housing.
I put them in the HCL, couple drop of Clorox and swish them around. I have a nice bottle of very yellow AuCl.


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