Solder is used to fuse electrical contact points together in small quantities, as occurs in circuit boards. It is applied with a soldering iron that heats the solder, melting it so that it fuses the two points together and prevents the circuit from being broken. Different types of solder exist for different applications, but they are most commonly made of metals with a low melting point, including lead and tin as the most common choices.
Soldering involves a soldering iron, which is a pen-like device whose tip heats to more than 750 degrees Fahrenheit, hot enough to melt lead and tin. Before creating a connection, clean all parts on both ends with a sponge so heat can transfer. Dirt, grime and oil prevent the solder from solidifying and creating a proper connection.
Apply a small amount of solder to the connecting points, then apply the soldering iron to the connection to heat it. Never heat the solder directly; instead, heat the connection and allow its heat to melt the solder and form a strong bond. Leave the connection to cool for a few minutes. Upon inspection, the surface of the solder should look shiny and metallic, indicating a clear join.