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February 2001

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From:
"d. terstegge" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 16 Feb 2001 11:56:56 +0100
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Hi Nicolas,

Here we make a lot of very small batches (sometimes only 1 or 2 boards) and I wouldn't like the idea of throwing about 400 grams of solder paste away after printing 10 grams onto the boards. We don't see a difference in soldering quality between products that we made with a freh jar of solder-paste and products that were made with paste that had been on the screen before. But most of our inspection is done after cleaning, so we won't notice an occasional solderball due to absorbed moisture. In a no-clean environment this could be different....

Kind regards,

Daan Terstegge
Unclassified mail
Personal Website: http://www.smtinfo.net

>>> "Stephen R. Gregory" <[log in to unmask]> 02/16 4:22 am >>>
In a message dated 2/15/2001 8:46:23 PM Central Standard Time,
[log in to unmask] writes:

<< Solder paste reuse: does anybody has this practice? Obviously, my solder
 paste supplier does not recommend it.

 Nicolas Ortiz
 Process Engineering Group Leader
 Conexant Systems >>

Hi Nicolas,

Your supplier is not recommending it to in order to sell you more paste, it
is a valid recommendation.

I'm not quite sure about what you mean by "reuse", but if you mean taking
paste off a stencil, putting it back in a jar after a run, and then keep
using it, that's a bad idea.

The paste will absorb moisture, the volatiles in the paste will evaporate,
basically changing everything about the formulation of the paste = not
performing like it's been advertised to do...I don't know of any manufacturer
of solder pastes that would recommend to reuse solder paste after it's been
dispensed on a stencil...

I do however, understand your concern about the expense when throwing away
solder paste...it's not cheap, anywhere from $50.00-75.00 for a 700-gram jar.
But you can recover some of the costs through recycling...Alpha/Fry Metals
will recycle solder paste and give you back the money that the tin/lead
market prices are at the time you turn it in...

Bottom-line, don't "reuse" your solder paste...it'll bite you...

-Steve Gregory-

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