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.htmIf 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-NDIf 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.