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Examples
of common soldering failures
Resin joint
Because a flux film is
present between the metals to be joined (for example,
between a wire and a terminal), the metals are
not electrically connected with each other. Even
if they are temporarily connected, they will come
off when they are used.
This failure frequently occurs in the case of
uneven heat conduction. To prevent this, adjust
the position of the soldering iron placement.
Cold joint
This is the most common
failure. In general, soldering conditions with
a rough surface and no brightness on the soldering
part are called "Cold-Joint". This failure
weakens the joint strength, causing the jointed
parts to come off when they are exposed to impact
or vibration.
This failure frequently occurs when the heating
temperature is low and the soldering tip is removed
before the solder completely melts. Also, a similar
condition is observed in the case where the joint
part is moved before the solder hardens (cold
joint) or where too much heat is applied to the
joint part (overheating).
Insufficient solder
This failure indicates
the condition that solder does not thoroughly
spread over the wire and the wire is partially
exposed. This failure frequently occurs in the
case where the wire or terminal surface is dirty
or oxidized, or exposed to uneven heat application,
or where the amount of heat is not enough to solder.
To prevent this, clean the wire or terminal surface
and adjust the iron position so that the soldering
tip is placed on an appropriate part.
Overheating
This failure indicates the
condition that solder spreads over the terminal
excessively. This failure frequently occurs in the
case where the heating time is too long or too much
or when applying solder too much.
Solder drop will not cause a particularly serious
problem. However, if it causes a short-circuit between
terminals, it will result in a critical failure.
For soldering, we must clean
the parts to be jointed, put the soldering iron
at an appropriate position, apply heat for an
appropriate time, and feed solder in an appropriate
quantity.
When large and small metal pieces are compared,
it is natural that the small metal piece is heated
earlier than the large one. Furthermore, solder
will flow to a part at a higher temperature because
of its characteristic. To do soldering well, we
must make use of this characteristic.
Thermal conductivity is considerably improved
by feeding a small amount of solder to the soldering
tip.
Soldering usually cannot be done well the first
time. Try to solder many times and you can improve
your skill by trial and error.
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