22 Dec
2007
22 Dec
'07
2:08 p.m.
From: pat at computer-refuge.org
On Saturday 22 December 2007 02:52, Roy J. Tellason wrote:
Hi
I've probably reworked 100's of boards. I've found the safes method
is to use a solder sucker and thin blade to move the lead around ( doesn't
absorb too much heat ).
Using the solderwick, I've found it is more likely to lift a lead. If you
make too much contact and can't heat it all, it is difficult to remove the
wick without damage.
I always add fresh solder and flux before sucking. If you don't get
a clean suck, add solder again and repeat. Don't try to clean the last
bit by reheating only, you need to re-add solder.
For through hole ICs, I will first clear the hole and then apply slight
sideways pressure with the iron. The instant the lead moves, remove
the heat. The lead will usually be free or have a tiny connection one
can break with pliers. If it didn't come lose, repeat by adding solder.
For surface devices I may just lift the leads one at a time after cleaning
solder or use a heat gun ( depending on package type ). Patience
and timing are what it takes.
Dwight
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On Friday 21 December 2007 16:54, Chuck Guzis
wrote:
The way that they taught us to do it in college was basically the same
way, except using solderwick to pull up the excess, instead of a solder
sucker.
The technique was basically to tack down the corners of the chip first,
so that the chip is/stays properly aligned with the board, and then
drag the soldering iron along each side (using a wedge tip), with the
solder along the trailing edge.. if you get just the right speed,
you'll get a good connection. Then, just take solderbraid and an iron
to pick up the excess.
It works, and unless you're careless (or using a 100W soldering gun or
something), it works pretty well, once you've tried it a time or two.
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.