Build Your Own Combat Robot

338 Build Your Own Combat Robot
■ Not too hot/ too cold The solder temperature must be hot enough to
create a solder that will hold. You also need to protect the components
you are soldering from excessive heat or you can ruin them.
If you’re new at soldering, practice soldering with scrap components, wire, and
metal before committing to a particular project.
Soldering Printed Circuit Boards
To gain soldering skills on printed circuit boards, you might want to find a piece
of electronic equipment that’s been trashed and rip it apart to solder and unsolder
the parts from the circuit boards until you feel competent. You may find that unsoldering
is more difficult than soldering, yet this practice will help you in learning
how to apply only just enough of the hot iron’s tip to the board without damaging
it. Practice is really the best teacher and you don’t have to worry about ruining a
one-of-a-kind board.
Before embarking on any type of soldering, you should clean the soldering iron’s
hot tip with a wet rag or with the small, dampened sponge on a soldering station. It
must be clean to do a good job. Most people like to use rosin core 60/40 solder,
which is 60 percent tin and 40 percent lead, for electronic work. It is basically a tube
of solder containing a tiny bit of rosin in the center. Never use acid core solder.
Smaller 0.032-inch diameter solder is good for smaller joints; and larger,
0.050-inch and 0.062-inch diameter can be used for larger, non-circuit board joints.
Next, dab a bit of solder on the tip—that is called tinning the iron. Holding the
soldering iron in one hand, feed a bit of solder from a reel onto the tip. The trick is
to melt the solder and quickly apply it to the joint to be soldered. Use only enough to
make a “tent” of the solder around the component’s wire lead protruding through
the circuit board’s hole and neatly covering the O-shaped circuit “pad” surrounding
the hole. Most soldering iron tips are of the chisel tip variety, and you want to
place one of the chisel’s faces flat on the surface you intend to solder to transfer the
heat as rapidly as possible.
If you did it right, the tent of solder will cover the pad and taper up the wire a
bit, and it will be shiny. If the solder forms a ball or is not shiny, you didn’t get it
hot enough. These are called cold joints. For printed circuits, you must be careful
not to overheat the traces and cause them to lift off the board. You’re working in
that narrow area of getting it hot enough for a good joint but not too hot to damage
the board. A 15–40 watt soldering iron, or “pencil,” works best for printed circuits.
Be careful to not cause “solder bridges” from one trace to another.
Another important consideration is protecting the components you are soldering
from excessive heat and static electricity. Integrated circuits (ICs), small transistors
and diodes, capacitors, small resistors, and other smaller components can be ruined
by too much heat. As with the circuit board’s traces, you must keep the iron on the
board and protruding lead only as long as it takes to make a clean, shiny solder
joint. Tiny clip-on heat sinks can route heat away from a component. Soldering one
lead of a component, and then waiting until the component cools a bit before soldering
another lead, especially on ICs, helps to prevent heat damage.