Mike,
Thanks for the improved definition. I agree with the regular testing of the solder pot. It is easy to interpret comments incorrectly. I'd be leery of accepting "recycled solder" from someone else to use in my machine, but certainly putting my own stuff back in the pot would be ok.
The caveat here is data is king!
For our volume, sending dross offsite (back to original supplier) is the most cost effective solution rather than buying a machine for solder recovery.
Phil
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Mike Fenner
Sent: Monday, September 17, 2012 10:51 AM
To: [log in to unmask]
Subject: Re: [TN] Recycled solder?
Hi Phil
I think it would be better not to think of this as recycling, its not even re-using.
All you are doing is returning to the solder pot material that you accidentally just removed a moment ago.
In other words to get the dross out you also tend to remove unoxidized metal. So it's prudent to squeeze that out from the oxides, spent flux residues etc that you don't want and return it to pot. This doesn't affect the metallic composition in anyway.
Thereafter yes you are right, you need to run a continuing check programme on the metallic impurities and main ingredient balance on the pot itself.
Small aside.
Analysis of the squeezed out solder maybe very slightly different from the pot, but in reality not much different from your analysis samples as these also are usually just scooped out from the top of the pot. Sorry to be sound slightly cynical here :), I'm trying to be a realist.
In truth the absolute amounts of impurity don't matter so much as long as they are reasonably accurate and consistently taken/done. What you are looking for is trends and results. You know what your soldering results are and you can plot those against the numbers from your assays. These will predict (after the first time or projected to an arbitrary amount) when you next need to change the solder for impurities, or adjust alloy balance. They are also your failsafe to highlight a sudden cause for concern.
Regards
Mike
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-----Original Message-----
From: Phil Nutting [mailto:[log in to unmask]]
Sent: Monday, September 17, 2012 2:56 PM
To: [log in to unmask]; [log in to unmask]
Subject: RE: [TN] Recycled solder?
Mike,
In all my reading of notes here on Technet and in the trade mags and web sites we are supposed to monitor our solder pots for levels of copper, gold etc. that are "stripped off" the boards as they are soldered. If we simply squeeze out the "good" solder from the dross aren't we also getting the higher levels of contaminants that would have been in the solder pots? So, do we really consider this recycled solder as pure as the new stuff that comes from the likes of Metallic Resources, Kester, Alpha Metals, et al.?
Phil Nutting
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Mike Fenner
Sent: Friday, September 14, 2012 4:23 PM
To: [log in to unmask]
Subject: Re: [TN] Recycled solder?
Oh, I think it's stretching a bit to call it recycling, but it was nice of them to tell you.
Most people over-skim their pots and "dross" usually contains a significant amount of good metal. There are a number of mechanical devices which rely on this and work by squeezing out the metal to get it back.
A little while back someone or other promoted a new chemical additive for aiding this process. Bemusingly, at least for me, there was quite a lot fuss about this as I remember, including on this forum. I think one supplier even got an award for it. Actually none of this is new - just another example of recycling. These products/techniques were common from the earliest days of wave soldering.
Footnote.
Ironically, the money/credit they get for their dross will go down dramatically, as it really will be dross. [Assuming their recycler/supplier has been playing an honest game with them.]
Regards
Mike
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Pete
Sent: Friday, September 14, 2012 2:56 PM
To: [log in to unmask]
Subject: Re: [TN] Recycled solder?
My understanding is that they will do the recycling themselves, on site.
They said the recycling would be mechanical, not chemical, so maybe it is just squeezing out the droww. They also said it was an effort to be environmentally conscious, but they are in China, so I'd think it's really cost.
We are among their smaller customers, so I can't make a lot of demands.
They asked if we would accept boards made with recycled solder. I suppose the best I can do is reply with a list of concerns and ask for test results.
Thanks!
Pete
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