Gold in solder

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brijes

Member
Joined
May 28, 2015
Messages
8
Location
Ottawa, On
Hi guys, been reading alot, first question post for me.
I am led to believe that gold is used (in small amounts) to make certain types of solder(80Au/Sn).
If this was placed in hot HCL, apparently the only thing remaining would be au? If so can I assume the residue left would be black in appearence?
 
I think the gold(80%) will protect Sn(20%) from HCl, so you may have to "inquart"
 
denim said:
Where does one find solder that is 80% AU? Are you sure it is not 8% AU? Even 8% seems like a lot to me. If it is 80% I want some!

Aircraft stator blades for one.
 
anachronism said:
denim said:
Where does one find solder that is 80% AU? Are you sure it is not 8% AU? Even 8% seems like a lot to me. If it is 80% I want some!

Aircraft stator blades for one.
Sure you don't mix it up with the AuNi 82/18 braze (melting point 950 C)? The only place I can imagine using AuSn 80/20 is in electronics... a quick googling gives...
https://www.ametek-ecp.com/-/media/ametek-ecp/v2/files/cwtechnicalpapers/coining_english_gold_tin_paper.pdf
AuSn 80/20 is among other things used as a preform for sealing electronic devices in ceramic capsules and to attaching laser diode dies in packages. It melts at 280 C.

And as Owltech said, the high gold content will protect the tin from the acid. You need to lower the gold content to around 25% or less to be able to dissolve the tin selectively.

Very few modern components are mounted in ceramic capsules any longer and CPU:s with gold soldered lids are becoming rare.

Göran
 
So by your definition that alloy wouldn't be able to be processed using reverse AR?

Yeah I am probably mixing the OP's question up with Denim's question though -

Jon
 
denim said:
Where does one find solder that is 80% AU? Are you sure it is not 8% AU? Even 8% seems like a lot to me. If it is 80% I want some!
I read somewhere 98%Au/2%Si
alloy used in silicon die-attach. Id imagine this is an extremely small amount.
 
anachronism said:
So by your definition that alloy wouldn't be able to be processed using reverse AR?

Yeah I am probably mixing the OP's question up with Denim's question though -

Jon
The original question was about processing AuSn 80/20 solder with HCl. The high gold content in the solder gives it superb corrosion properties and that would also protect it against straight HCl.
Ordinary AR would work fine but it would create some metastannic acid. I can't see any reason for reverse AR not working or any reason to use it. It could be a bit slow to filter depending on how much solder you process.
You have probably refined some in your days as part of some lot of ceramic CPU:s. I don't know how common it is but it isn't super rare at least in older IC:s.

There was a thread about it in the past... http://goldrefiningforum.com/phpBB3/viewtopic.php?f=34&t=2662&#p39316

Göran
 
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