Thus spake Harold M Hallikainen (haroldhallikainen@JUNO.COM):

>         I also wonder about using a low flow temperature controlled heat
> gun for soldering.  High flow blows the parts off the board.
> Nontemperature controlled melts parts.  Anyone have any experience with

I've successfully soldered quite a few boards using a heat gun (nothing special,
just a standard heat-shrink/paint-stripper type gun). This includes soldering
a 100 pin fine pitch (0.5mm pitch!) device on a non solder-masked board. Of
course you get bridges between the pins - but cleaning up with solder wick
(or coax cable braid soaked in spray flux) fixes all that very nicely!

The way I do it is to squeeze solder paste from a syringe onto the pads (just
lay down a stripe), place the components, then heat (on a heat-proof surface)
with the gun, gently at first then once the whole board is hot I concentrate on
one component at a time until the solder melts, give it about 5 seconds fully
melted (the gun is about 3" above the board at this stage) then move to the
next component. IT takes about 60 seconds total for a 4" square board, and
providing you don't overheat, this is within specs for soldering.

Be sure not to move the board until it has cooled down (or the chips will fall
off - I know!) Then inspect with a magnifying glass, use solder wick to remove
bridges (small ones can be removed just by drawing the iron tip between pins)
and resolder any pins that did not get soldered.

Be sure NOT to get solder paste underneath the component - it can lead to some
 very
hard-to-find faults, because it does not get melted, and can short out pads.

I actually find this easier than hand-soldering lots of through-hole pins. But
 for
any number of boards, it's better to get them automatically done.

Have fun!

--
Clyde Smith-Stubbs    | HI-TECH Software,       | Voice: +61 7 3354 2411
clyde@htsoft.com      | P.O. Box 103, Alderley, | Fax:   +61 7 3354 2422
http://www.htsoft.com | QLD, 4051, AUSTRALIA.   |
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