I'm wary of buying paste at any warehouse distributor. They have it in
stock for who knows how long and probably not even refrigerated. I've
thrown away most of the stuff.
Now I buy it at a small distributor, who orders the paste directly at
the manufacturer each time. This might not be an option for homebrew
stuff but I would still ask about shelf time and refrigeration.
The paste from dealextreme is not very good, I ordered it because I
was curious but quickly after opening the seal it dried out (the
plastic lid is not tight it seems).
Regarding the dangers of lead, I usually agree with your opinion,
however with solder paste more attention is required. The lead is
ground to a fine powder, ideally suited to get ingested and absorbed
by the body. Clean working is very much recommended and don't leave
paste drying out and making a mess. I always have a spare board on the
SMD bench where I will "start" the syringe and adjust volume, this
board is thrown on the hotplate to reflow the paste and render it
safe. Dispose of unused paste properly, and wash your hands after
handling it. This task is the only one where I stick to the no eating
at the workplace rule....
I really don't understand the gmail spell checker, what is wrong with
"manufacturer" and "refrigerated"?
ST
On Mon, Jul 13, 2009 at 5:38 PM, Steve Greenfield<alienrelics@...> wrote:
>
> Recent discussion on Seattle Dorkbot list about solder paste, so I've cut-and-pasted the messages to save them.
>
> Steve
>
>
> The best pricing I have found for Kester solder paste is from Techni-tool
> (http://www.techni-tool.com/static-products/kester/KesterSolderPaste.html)
> The Kester R500 water-soluble in a 35g syringe is only $13.13. (The link is
> at the bottom of the page, but is too long to paste here).
>
>
> I use Zephyrtronics. Fast, no hassle.
>
> http://www.zeph.com/zephpaste.htm
>
>
> If you want it in a syringe, Digikey is probably the best source. They
> have a couple brands, but this one does not require paying for
> overnight shipping:
> http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=SMD291AX-ND
>
> If you will be using a paste mask, you don't need a syringe, so you
> can get it really cheap from DealExtreme:
> http://www.dealextreme.com/details.dx/sku.7952 (There has been some
> discussion of trying to mix this with some extra liquid flux in a
> standard glue applicator syringe that you can get at many hardware
> stores, but I haven't tried it). DealExtreme is great, but expect to
> wait at least two weeks to receive your package (it ships for free
> from Hong Kong).
>
> Unless you are a professional, do not try to use lead-free. You will
> not get good results unless you have a commercial reflow oven. I used
> to work for a commercial electronics manufacturing, and even with all
> of our special equipment, we avoided lead-free because it is a huge
> pain. A toaster will help, but you will get much better results with
> standard leaded solder. There are a lot of myths about the lead being
> a health hazard, but unless you plan on licking the boards they are
> perfectly fine. The smell & smoke when soldering is the flux burning,
> not the lead, so it is not a problem.
>
> The dangers from leaded solder come not from it's use, but from it's
> disposal. The lead in landfills creates a problem. While I try to be
> environmentally conscious, this is an area where I don't see the
> point. Not only is the amount of lead my soldering adds to the waste
> stream minuscule relative to the overall problem, but the increased
> failure rate due to the difficulty with lead-free soldering will
> probably offset any benefit it would produce.
>
>
> ------------------------------------
>
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>
>