# Depopulating PC boards with salts?



## Gene Gindling (Apr 13, 2008)

I recently read a short piece where a university in England found a process to remove the solder from circuit boards with a salt based process. (Probably patented).
I was wondering if Lou, Irons, Peter, Chris or anyone else would care to describe potential processes to do this. :?: 
The benefits are many. There is no heat required. Components can be resold to make new items providing additional income from the scrap, and toxins would be more containable.
Thanks, Gene


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## Lou (Apr 13, 2008)

Do you have a link or PDF of what exactly it is you're talking about? It is very hard to even guess as to what is being done with just ''a salt based process'' to go off of since there are many, many salts.


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## Gene Gindling (Apr 13, 2008)

Lou,
I will try to find the reference, however it was in the form of a news story, so little technical information was given,
Thanks for the quick response,
Gene


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## donald236 (Apr 14, 2008)

i hope you can find that link i'd like to know more myself
thanks
donald


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## Gene Gindling (Apr 14, 2008)

I have been searching most of the evening without success. I found it Googling a term such as "circuit board recycling" or "Integrated circuit recycling". I will keep looking.

They must have found something which selectively attacks lead, tin or both without dissolving other base metals.
They stated that heat was not applied preventing potential degradation of integrated circuits which are reuseable.
The item was, as I stated above, in the form of a news story. The only description given was that they were using salts.

I was hoping some of the real chemists aboard here would come up with potential processes which we could test.
I will keep looking.
Gene


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## Scott2357 (Apr 14, 2008)

Check the links in your browser history.


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## calgoldrecyclers (Apr 14, 2008)

i believe you were reading an article on ammonium salts used to dissolve tin/ silver solders from boards? it is a rather long, drawn out process with adhering agents, tumbling, crushing, leaching, milling, etc. and yes, it is patented. 
try googling pcb recycling, or processing pcb's for precious metal content.


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## Gene Gindling (Apr 14, 2008)

Scott2357 - My browsing history is like an encyclopedia.

Calgold - I will try to find that article. The one I read was just a short news piece. The article may shed the light I need to start testing. Thanks for the lead.

Gene


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## calgoldrecyclers (Apr 14, 2008)

gene,
try this www.freepatentsonline.com/5238662.html . 

matte with a chloride salt. i had also read an article by a british or maybe an austrian company that was experimenting with salts of ammonia to dissolve the tin/ lead/ silver solders, leaving the remaining board intact.
i believe the process included tumbling in a large mill with the salts adhering to the solders and dissolving. washing the material, leaving boards and ic/ cpu intact.


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## Gene Gindling (Apr 14, 2008)

calgoldrecyclers
The process pointed to by the link seems to have the salts heated above that required to melt the solder. The process mentioned in the news story stated that "no heat is applied thereby not degrading the ic performance" or something to that effect.
The link did at least give clues as to the salts required.
Thanks again,
Gene


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## mizan (Jun 23, 2008)

Process for the recovery of tin, tin alloys or lead alloys from printed circuit boards sounds similar to what you described. I haven't had the chance to look, but there may be other patents that reference this one that would also be useful.


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