In article ,
micky wrote:
http://www.tegger.com/hondafaq/mainrelayfix/index.html
Next to the fourth picture, it says:
"Removal of old solder As much of the old solder as possible was
removed in preparation for re-soldering. It is possible to simply
re-flow the old solder, but this method is better. "
Does anyone agree with that?
I think "it depends".
There may be some advantages to clearing off the old solder and
replacing it entirely. Two possible such:
(1) Some years ago I had a problem with an audio amplifier...
intermittent solder joints. The manufacturer informed me that
their contract assembly house had "use the wrong solder" in the
wave-solder machine, and that this had resulted in a poor joint on
the transistor connections. I'm not sure whether it was a poor
bond due to the alloy used, or whether there was a difference in
thermal expansion rates which caused the joint to suffer more
stress due to power-on-heat/power-off-cold cycling.
The manufactuer specifically recommended that I strip out the old
solder and replace it.
(2) In some cases, the problem with a bad solder joint might be due to
the contact materials being soldered - oxidation, other
contamination, or an alloy which didn't "wet" well with the
solder/flus combination originally used.
In this case, stripping off the old solder, perhaps cleaning or
lightly scraping the metal, applying some proper flux to the
metal, and re-soldering would give you the best chance of a good
solder bond. Simply re-flowing the existing connection would not
necessarily get enough flux into the joint area to address any
problems on the contact surfaces.
Issue (2) might hold, even if the joint was originally OK. If the
solder bond has cracked away from the contact metal, then the metal
surface has had the oppotunity to oxidize... and so getting some good
flus into the contact surface when re-soldering is probably a good
idea.
--
Dave Platt AE6EO
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