21 Dec
2007
21 Dec
'07
11:52 p.m.
On Friday 21 December 2007 16:54, Chuck Guzis wrote:
If you feel this subject is too far off-topic, please
respond
privately. OTOH, it just might help some who are trying to repair
some of the old gear that uses SMT.
At any rate, I've got some 68-pin TQFP packages that I need to mount
on a PCB. I've searched the web and become throughly confused over
recommendations.
I'd like to stay away from using a hot-air rework iron as I don't
think I have enough skill to use it without causing some damage to
the PCB or component. I'd like to use my temperature-controlled
Weller soldering station as the heat source. I'll also be using Sn-
Pb solder rather than lead-free.
Two approaches that I've seen for conventional soldering iron
mounting involve what I'll call "flood and suck" that involves
covering all of the leads on one side of the QFP on the PCB with
solder and then using a solder "sucker" (such as a Soldapullt) to
remove the excess.
I've *never* heard this recommended. And with that setup you're talking about
pulling the solder out between the part lead and the trace without pulling
the trace off the board. I wouldn't care to try it.
The other approach uses solder wick (solder removal
braid), laying
the braid over the QFP leads and PCB and heating and applying solder
*through* the braid to the leads.
I'm fairly confident that I could do either, but who's had real
success with either method?
I've actually done very little with surface mount, mostly finding it not
worth the bother for salvage, but while attending a technical seminar some
time back (Yamaha P.A.C.E. if anybody's interested) they recommended the
second technique for dealing with some of their stuff that was surface-mount,
most notably a 286 Laptop they had out that had something like 16 MIDI ports
on the back of it. That's how I'd do it, anyhow.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin