On Fri, 13 Jun 2008 12:20:07 -0400, Joseph Gwinn
wrote:
In article dvs4k.36013$lE3.12345@trnddc05, GeorgeD
wrote:
Tom Gardner wrote:
My good friend asked me to repair his Dell laptop, an Inspiron 5150 that
has a
well documented problem with mechanical stress cracking solder joints. The
door
for the communication cards has little tabs that bump on a surface mount
chip
causing the joints to crack and fail. I could see the cracks with a
hand-held
microscope. I made a tip for my soldering station using a piece of 28 ga.
copper wire and fluxed the joints with a brush having a single strand of
horse
hair and some melted "No-Corrode" paste. I didn't add any solder, just
remelted
the existing. It took me over an hour to do the whole chip, it was like
circumcising gnats with an axe!
This job was beyond my limits but I got lucky and the laptop works. I want
a
REAL boom microscope with a built in camera! I wonder how this job would
be
done by real repair people?
Carefully. If you are referring to the brand "No Corrode" soldering
paste, it is corrosive. It was developed for the plumbing trade a
century ago. The definition of no corrode for plumbers is different
that for electronics. ³No Corrode² brand flux can not be used electronics.
Been there done that. Talked to the ³No Corrode² flux people.
While it's true that NoCorrode is for plumbing, before I knew any better
I put a Heathkit VTVM kit together with plumbers solder and flux. I
still have that VTVM, and it worked the last time I used it, so the
corrosion wasn't too aggressive.
We had a customer use acid-core solder on a triac and it burned up as
a result (the flux residue is ionic, so it conducts electricity, which
led to carbon tracking, burning, sizzling, smoke etc.). Do not use
acid flux on anything electrical or electronic. You might get a
situation wherein your meter works fine on a dry day and reads wildly
off on a humid day.
I also used plumbers flux to solder cadmium-plated steel alligator
clips. Again, I still have those test leads, 40 years later. The
problem is that the rubber insulation has gotten hard.
Joe Gwinn
Best regards,
Spehro Pefhany
--
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