From: Gideon Zweijtzer (gideonz_at_dds.nl)
Date: 2002-10-17 12:37:58
|I've never had to solder SMT chips before, but I thought I'd pass along a
|technique I saw in a magazine one, for a hobby project using a
surface-mount
|IC. It called for low-melting point (about 200 degrees F, I think)
|indium-based solder paste (a quick Google check showed indium solder
|suppliers, so you should be able to order some). The idea is to apply
spots
|of the solder paste to the pads with something like a toothpick, set the IC
|in place, then float the board in a pan of almost-boiling water. The
author
|said it worked great.
It still works best for me to just use a soldering iron and regular
solder... just with some flux to make sure the pins won't get connected to
each other rather than to the pads. If you use that, you can just use a
thick tip and solder 5 or 6 pins at at time as you slide along all the pins.
I've soldered SMT's down to a pitch of 0.4 mm like that, with a stronger
pin-to-pad connection than what you get when you use solder paste and an
oven.. (0.4 is not even used much anymore as BGA's came into the picture.
The regular fine pitch is now 0.5 mm.)
Of course this method doesn't solve the BGA problem. I did, however,
DEsolder BGA's by using a hot-air gun (paint-remover!)... But I am afraid
that when I use the same method for soldering them, that the BGA would move
because of the air flow.
Gideon
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