# Using tin as PM collector



## Marcel (May 1, 2013)

In all chemical recovery processes tin is regarded as an disturbing factor that must be eliminated before dissolving PMs or precipitating them.
Tin itself is a precipitant, since it is a metal that ranks very low in the electrochemical chart plus we all know it in conjunction with HCl as "Stannous Chloride", which is not only an indicator for gold, palladium and platinum, but works as a very strong precipitant as well. Moreove tin in a solution can create so called metastasic compounds that make it hard to work with and extract the precious metals.

It is well known to use HCl as a pretreatment step in order to remover the solder(=tin) from electronic components. The remains are regarded as waste and must be disposed.
Since I lived from and with soldering and I really like to solder and desolder, I found this waste a "waste" somehow and decided to try some other concepts and look into their yields etc.

Now if you have the time, the tools and the skills, you can remove tin from any PCB !
Not fully, but quite effective. You can use a heatgun to melt the tin ( better would be a infrared light source, such as a quartzlight, a hot plate from underneath etc, because the heatgun will create fumes that are likely to be inhaled, which makes it not unacceptable for long time using.)

If you do so, you should focus on the areas with the BGA (Ball-GridArrays) solderballs. (see also: http://en.wikipedia.org/wiki/Ball_grid_array)

Let me tell you shortly how the SMD solderpaste usually is applied onto a PCB: The machine that does it is called a screen printer. The screen printer uses a very fine metallic mesh or a sheet of metal, where a laser has cut all the areas out that are supposed to be solder pads for all these small SMD components. Now this machine will press a thick tin paste through the screen and the paste will end up on the PCB. 

In old times the solder was often made of 65% sn and 35% pb or a similiar composition.
Lateron or in mil and other applications silver was used in different fractions. 2%-5% is normal.

Now the area below the BGAs, which are often CPUs or Chipsets, GPUs and other here called "flatpacks", that do not have leads but only balls underneath the chip, is quite interesting. 

Those balls must be of very high quality. Not only in their shape, but also in their composition. They must be able to carry very high signal rates very clean and that is why these solderballs are NOT printed on the boards with this screenprinter, but brought onto them in a second different process!

So solder is not solder on your boards! There are areas with low/medium quality tin solder, and areas with very high quality tin/silverPd/ even Indium alloys!

Try to locate those areas, heat them and scrap this tin together and collect it. It is worth a try. Once You have 1 Kg or so, you may have it tested and see what it contains. It is very easy to melt (tin has a melting point around 230°C) and to handle.
Through "migration" there may be PMs in that tin such as gold, palladium and others.
Palladium is found in the terminal of the solderpad. It mixes very well with silver and may migrate from the terminal to the solderballs.
Here is an overview of alloys used by one single manufacturer. 
There are hundreds of different alloys out there, so you never know and should always keep an eye on these BGA solderballs!




Here is a video I made, that will show you how to scrap this solder together, forming small balls with a SS tool. Just scrap them together, use force and then move that liquid ball to an area, where there are no solderpads. Once it cools down, you can just remove it without any force. I speak german there, but I think you only need to see the image after reading this here, if someting remained unclear.Dont forget the CPUS/Chips. they have the solderballs underneath as well!

[youtube]www.youtube.com/watch?v=YEiMavFolq0[/youtube]

1. This is a way to remove tin prior to recover. Something you have to do anyway.
2. Instead of creating waste, you create value, even if only minimal.
3. It all adds up. PMs may be in there, one day will be pay day!
4. It´s fun.


I dont get the Youtube link to display the preview window . Can someone please instruct me, how to do that?


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## stardust18 (May 2, 2013)

Good day. Here's the video? http://www.youtube.com/watch?v=YEiMavFolq0


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## jmdlcar (May 2, 2013)

Wish the video was in English. What type was that soldering iron was that?

Jack


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## solar_plasma (Oct 6, 2013)

Interesting.

Has anybody already found Pd or In in solder balls from computer boards?


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## chlaurite (Oct 6, 2013)

Nice video!

I have actually collected a few hundred grams of those exact balls... I didn't know what they contained, but had noticed they behave very differently than normal solder, and sometimes they have a strange internal structure when they crack in half (sort of a reddish - but not copper-red - square hollow area).

Now I just need to figure out what to _do_ with them. 

As an aside, I have a totally offtopic question which I hope the mods will forgive - Doesn't German have its own words for things like "slot" and "balls"? Or do they just sound more-or-less the same as the English words?


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## solar_plasma (Oct 6, 2013)

> Doesn't German have its own words for things like "slot" and "balls"? Or do they just sound more-or-less the same as the English words?



I think in this world today it could be interpreted as a kind of "anti-american" attitude, if you call solder balls for Lotkügelchen and a slot for a Steckplatz, interface for Schnittstelle and a download for ein Herunterladen. :lol: Well, you are right, we have words for everything. But when you have gained some special technical knowlegde from mostly english sources, it is easier to use the assimilated english term.


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