Getting Somewhat More Serious 109Experiment 12: Joining Two Wires Togethertheory
Soldering theory
The better you understand the process of soldering, the easier it should be for
you to make good solder joints.
The tip of the soldering iron is hot, and you want to transfer that heat into the
joint that you are trying to make. In this situation, you can think of the heat as
being like a fluid. The larger the connection is between the soldering iron and
the joint, the greater the quantity of heat, per second, that can flow through it.
For this reason, you should adjust the angle of the soldering iron so that it
makes the widest possible contact. If it touches the wires only at a tiny point,
you’ll limit the amount of heat flow. Figures 3-45 and 3-46 illustrate this con-
cept. Once the solder starts to melt, it broadens the area of contact, which helps
to transfer more heat, so the process accelerates naturally. Initiating it is the
tricky part.
The other aspect of heat flow that you should consider is that it can suck heat
away from the places where you want it, and deliver it to places where you
don’t want it. If you’re trying to solder a very heavy piece of copper wire, the
joint may never get hot enough to melt the solder, because the heavy wire
conducts heat away from the joint. You may find that even a 40-watt iron isn’t
powerful enough to overcome this problem, and if you are doing heavy work,
you may need a more powerful iron.
As a general rule, if you can’t complete a solder joint in 10 seconds, you aren’t
applying enough heat.
Figure 3-45. With only a small surface
area of contact between the iron and
the working surface, an insufficient
amount of heat is transferred.
Figure 3-46. A larger area of contact
between the soldering iron and its target
will greatly increase the heat transfer.tools
Desoldering
Desoldering is much, much harder
than soldering. Two simple tools
are available:- Suction pump. First, you apply
the soldering iron to make the
solder liquid. Then you use
this simple gadget to try to
suck up as much of the liquid
as possible. Usually it won’t re-
move enough metal to allow
you to pull the joint apart, and
you will have to try the next
tool. Refer back to Figure 3-10. - Desoldering wick or braid.
Desoldering wick, also known
as braid, is designed to soak
up the solder from a joint, but
again, it won’t clean the joint
entirely, and you will be in the
awkward position of trying to
use both hands to pull com-
ponents apart while simulta-
neously applying heat to stop
the solder from solidifying.
Refer back to Figure 3-11.
I don’t have much advice about
desoldering. It’s a frustrating experi-
ence (at least, I think so) and can
damage components irrevocably.