Desoldering

At some stage you will probably need to desolder a joint to remove or re-position a wire or component. There are two ways to remove the solder:

1. With a desoldering pump (solder sucker)

• Set the pump by pushing the spring-loaded plunger down until it locks.

• Apply both the pump nozzle and the tip of your soldering iron to the joint.

• Wait a second or two for the solder to melt.

• Then press the button on the pump to release the plunger and suck the molten solder into the tool.

• Repeat if necessary to remove as much solder as possible.

• The pump will need emptying occasionally by unscrewing the nozzle.

2. With solder remover wick (copper braid)

• Apply both the end of the wick and the tip of your soldering iron to the joint.

• As the solder melts most of it will flow onto the wick, away from the joint.

• Remove the wick first, then the soldering iron.

• Cut off and discard the end of the wick coated with solder. After removing most of the solder from the joint(s) you may be able to remove the wire or component lead straight away (allow a few seconds for it to cool). If the joint will not come apart easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling the joint apart, taking care to avoid burning yourself.

 

What is solder?

Solder is an alloy (mixture) of tin and lead, typically 60% tin and 40% lead. It melts at a temperature

of about 200°C. Coating a surface with solder is called ‘tinning’ because of the tin content of solder.

Lead is poisonous and you should always wash your hands after using solder.

Solder for electronics use contains tiny cores of flux, like the wires inside a mains flex. The flux is

corrosive, like an acid, and it cleans the metal surfaces as the solder melts. This is why you must melt

the solder actually on the joint, not on the iron tip. Without flux most joints would fail because metals

quickly oxidise and the solder itself will not flow properly onto a dirty, oxidised, metal surface.

The best size of solder for electronic circuit boards is 22swg (swg = standard wire gauge).

For plugs, component holders and other larger joints you may prefer to use 18swg solder.