CHAPTER 22 ■ SOLDERING AND CONNECTING
Soldering the Motors
- Touch the soldering iron tip to one side of the motor terminal and wire, directly at
the point of connection (see Figure 22-5). It is important to make as much contact
with the clean, tinned tip so that heat transfers to the wire and motor terminal.
Figure 22-5. Soldering iron tip on one side of the wire, solder on the other side of the wire
- Press the solder wire against the other side of the motor terminal and wire.
Here is the second rule of soldering: the solder to be applied should be touched against the heated
joint, not the soldering iron tip.
Because the solder wire is heated by the joint instead of the soldering iron tip, the solder-wire flux core
cleans the heated metal and then the molten solder flows over, into, and around the joint.
Sometimes, I’ll briefly place the solder wire at the location where the soldering iron tip meets the joint,
so that a small amount of molten solder provides a high-quality thermal path between the soldering iron
tip and the joint. Then I’ll switch the solder wire to the other side to insure that the joint has been heated up
enough and that the molten solder flows throughout the entire joint.
Beginners often try to apply solder to the soldering iron tip and then brush the molten solder against
the joint. Although this appears to work, the solder wire’s flux core cleans only the soldering iron tip and
burns off before reaching the joint. Also, the solder coats only the surface of the joint; it doesn’t flow into all
the nooks and crannies.
With a properly cleaned and heated tip, the solder wire should melt from the other side of the small
joint in three seconds or less. If it isn’t melting, pull back and let the area cool. On the next attempt, make
sure the tip is clean and is making firm contact against the joint. A bit of molten solder between the tip and
the joint may help.
Thicker leads and larger metal pieces take longer to heat up. This is because the heat is absorbed by the
metal and conducted away before the solder can melt. In these situations, slide the solder wire nearer the
soldering iron tip and the joint. Be a little more patient, it may take up to five seconds for the solder to flow
on larger or thicker metal.
- After the solder first starts to flow, it should only take a second or two more to
completely flow around and through the entire joint. Now you can remove the
solder wire from the joint. - After you have removed the solder wire, you can then remove the soldering iron
tip from the joint. If you remove the soldering iron tip before the solder wire, the
solder wire cools and sticks to the joint or deforms the solder joint’s shape as the
solder wire is pulled off. - You should be pleasantly rewarded with a shiny, strong, rounded, encompassing
solder joint (see Figure 22-6).