what is soldering

Soldering is the connecting of a two or more conductors together by melting solder, a metal which melts at a low temperature (well, 600 degrees Fahrenheit is low for a metal!), until it flows and forms a mechanical and electrical connection between those conductors. There are two basic soldering methods you are likely to come across. One uses rosin core solder, which is the most common solder around and is good for most applications. This solder contains a resin which helps the solder initially stick to the metal and is usually burnt off rather quickly during the soldering process. Note, this resin is sometimes the cause of cold solder joints. A cold solder joint will have a dull appearance, will yield poor electrical connections and can cause erratic circuit performance. Cold solder joints can also be identified by ball-like lumps instead of a smooth flow between metal and solder. Eliminate cold solder joints by momentarily applying the soldering iron to burn off the excess resin. As a side note, you should always use rosin core solder with electronic equipment. The acid in the acid core solder you can get at a hardware store will eat through the conductors in your circuit. The second soldering method uses a separate liquid flux and non-rosin core solder. This method is especially well suited for surface mount applications. The liquid flux is applied to regions where solder is desired. The soldering iron and solder are then brought simultaneously to the soldering point which contains the flux, the flux functions in the same manner as the resin in the rosin core solder. The previous method is preferred for most applications, however mounting surface mount components can be facilitated using the second method.
Successful soldering is easy to achieve if you remember a few simple rules. The connection to be soldered must be clean. Copper oxidizes and forms a non-conductive layer if left exposed to air. This causes cold solder joints in addition to making it difficult to apply solder. Ajax and a scrub sponge can be used to obtain a clean surface. Alternatively, you can used steel wool, a small file, sanding pen or steel brush depending on what needs to be cleaned – be mindful that you do not remove the copper you are trying to clean!
When first using a new soldering gun or iron, coat the tip with solder to prevent oxides from forming. Immediately brush off the excess solder with a soft cloth or damp sponge so that the tip of the tool has a smooth, silvery appearance. This process is called ‘tinning’, and should be done whenever the soldering tip loses its shine. Do not let the tip buildup excessive junk – this can corrode the tip and cause cold solder joints. Apply the tapered surface of the tip to the connection. Allow the connection to become hot, then apply the solder. Do not let the components become excessively hot – this can change their values or worse destroy the component you are trying to solder! Do not use the tip of the soldering iron or gun to melt the solder; let the connection melt it to avoid cold solder joints. When the solder begins to flow, carefully lift the tip and solder away from the connection, being careful not to move the parts being soldered. That’s it. All that remains is to use the diagonal cutters to cut the excess leads.