Re: Newbie questions: Recommendations on tools for SMT board repairs
- From: Smitty Two <prestwhich@xxxxxxxxxxxxx>
- Date: Sun, 19 Mar 2006 12:44:53 -0800
In article <HX9Tf.2918$vy.2145@trnddc01>,
"Ray L. Volts" <raylvolts@xxxxxxxxxxxxxxxxxxx> wrote:
Liquid flux. I hardly ever require it. If you need to solder a large area
such as a thick ground braid to a metal RFI cover, yeah, you'll probably
need some extra flux. For 25+ years, I've consistently made beautiful pcb
and terminal (pots, switches, etc.) joints using quality rosin-cored solder.
Liquid and paste flux is at best overhyped for general electronics work. At
worst, it's a time waster. It's one extra step in the soldering process you
can eliminate simply by using quality cored solder, the right iron temp and
proper technique (ensuing flame fest to be summarily dismissed ;)
Granted, flux requirements are different for lead-free applications, but if
you have a cored flux that's identical to a bottled flux designed for the
task, you should be able to achieve good joints with the same small amount
of flux delivered by the solder wire as with leaded cored solder for leaded
apps. For more on lead-free considerations:
http://www.kester.com/en-us/leadfree/flux.aspx
What flame fest? I'm the only liquid flux advocate around here, and I'm
not interested in being unpleasant. You don't want to use it, don't use
it.
One of these days I'm going to get around to posting a video or two
extolling the virtues of flux. One of the greatest advantages is
one-handed soldering. I often need one hand to hold the part, and one to
hold the iron. That doesn't leave much to feed solder with.
So, I stretch some wire solder out on the bench, hold the part in
position with one hand, add a drop of flux, put the flux bottle down,
and pick up the iron. Now, I drop the iron on the wire solder a half
inch or so from the end, pick up the drop of molten solder, and touch it
to the joint. This technique works very well in many circumstances,
including splicing wires or component leads.
As far as flux being a waste of time, let's apply my technique to a
little sixteen pin surface mount IC of 50 mil pitch or so. Right hand
positions IC, left hand uses wood Q-tip stick (or orange stick) to hold
IC down snug. Right hand applies flux, then grabs iron and loads with
solder (A half inch length of 0.020 or 0.025 solder.)
Start at the end away from you, slide tip along pins towards you. Eight
pins soldered absolutely perfectly in two seconds. That's one quarter of
one second per pin. You can actually move much faster, but may not get a
full heel fillet if you do. You never lift the iron from the board. Does
that sound like a waste of time?
.
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