On Thu, 14 Aug 2008, Robert Butts wrote: > I got pcbs back and now want to assemble them. What is the best way, i.e. > solder paste to use, heating method, solder bridge removal...? Most of the > components are small SMT parts. The through hole parts I'm fine with.
It depends what I'm doing. For discrete components (like 0603 sized Rs and Cs), just a fine tip soldering iron and fine solder wire - what I do is melt a small amount of solder on one pad, get the part with the tweezers, re-melt it and stick the end of the part into the molten blob. Then just solder the other end as normal. I can do this quite quickly. Where I have more components, I find it easiest to use solder paste. Small blobs (you need less than you think!) on each pad. For fine pitch SMD chips, I just put a bead of solder paste where the IC's pins are going to land, rather than attempt to put a blob of solder on each one. I then use a hot air gun. I've found that the air stream won't blow away even 0603 parts - the solder paste prior to melting will hold it, and when it melts, the surface tension is sufficient to stop the part from blowing away. Usually, I need to mop up a little excess solder from fine pitch parts - I just use fine desoldering wick to do this. I use Edsyn CR44 solder paste (available from Farnell if you live in Rightpondia). It has a very good shelf life. The drawback of this particular solder paste is it does tend to spread a little when it's heated, but I have found once it finally melts, it's not an issue (due to the soldermask, and surface tension pulling it back together in a better shaped blob). Generally once you've done a few SMD boards, you'll find you can often do it faster than the equivalent through hole - because you're no longer having to cut off excess bits of wire or turn the board over for each component. _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user