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Soldering is the process of joining two
metals by melting a filler metal (the solder) in between the two
metals to be joined. Heat is directly applied to the two metals to
be joined, not the filler. Some novice electricians will apply the
heat directly to the solder, which will cause it to stick to the
iron tip instead of the connection.
Before you begin to solder, plug your
soldering iron in, and select the proper heat for your application.
If you are soldering components on a PCB, then I would normally
choose a low wattage setting, or medium heat. Once your iron is hot,
keep the tip "tinned", meaning a thin layer of solder covering just
the tip of your soldering iron. This will let your iron tip heat
evenly, and will keep you from buying a new iron as often.
PCB soldering- When your solder is
laid down on a PCB, it should flow evenly and form a good concave
fillet. Look at the example below.
Some solder joints that are not acceptable
are convex (a giant mound), bridged gap (where your solder has
adhered to another piece of metal that it shouldn't be touching),
and too little solder (where you have pitting or small holes or gaps
in your solder connection).
Another good tip for soldering components
onto a PCB is to always use a thermal shunt, or heat shield that can
connect to your components lead. To use this, attach it between the
component and the point where you will be placing the soldering iron
tip. The heat from your iron will flow into the heat shield and
dissipate instead of into your component and destroying it. Also,
never leave the iron on the connection for more than 5 seconds, any
more than that could cause damage and disbonding of the foil strip. See
below.
Also, you need to
make sure the circuit board is clean. You can either use an eraser
to clean the circuit paths, or common isopropyl alcohol. If you do
not clean the board first, then the solder might not adhere
properly. Also, make sure to always dip your solder in flux before
soldering to help it stick and flow properly.
Wire soldering- When soldering two
ends of wires together to form a connection, first you will want to
strip about 1/2 to 1 inch of wire. Then take the two ends and bend
each bare wire section in half back onto itself (like your trying to
make a loop of it). Now take those two loops and interconnect them,
now it should look like a chain link.
Next twist the wire at the middle to give it
some added strength right off the bat. Finally, coat the entire bare
wire surface with an even amount of solder making one strong
connection.
I would recommend either taping the exposed
surface, or placing a piece of heat shrink tubing over it, and then
melting it down. This will keep the moisture out, and stop it from
touching other metals and shorting out, or shocking someone.
De-soldering- If you mess up and need
to re-solder, or you are removing the old component from the PCB,
you will need to know how to de-solder. There are two common methods
to de-solder a connection. First is using a solder sucker, which
comprises of heating the old solder joint until it melts and then
promptly sucking it up with the sucker. A picture is below.
The second common method to de-solder is
using a de-soldering wick. This is a flat, copper like metal
braiding that you place directly on the old solder joint. Apply heat
to the wick, and when it heats up enough to melt the solder, it will
flow up the wick and off the circuit board.
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