Soldering is a process of joining two or more members by melting and placing a filler metal at the joint, the filler metal having a lower melting point than the adjacent metal. In contrast to welding, the workpieces are not melted during welding. Welding is a process of joining metal parts to create a mechanical or electrical connection. It typically uses a low melting point metal alloy (solder) that is melted and applied to the metal parts to be joined and bonds to the metal parts and forms a bond when the solder solidifies. Welding is a technique for joining metal parts. A metal called solder is melted into the space between two metal components. As this solder cools and hardens, it forms a permanent bond between the parts. The solder acts as a kind of metallic glue that connects the elements.
Additional metals for soldering used to be lead-based (lead solder). Due to regulations, leaded solders are increasingly being replaced by lead-free solders, which can be made of antimony, bismuth, brass, copper, indium, tin or silver.
Occasionally there is contamination such as oil, dirt or oxidation at the connection point. Flux prevents oxidation and can sometimes chemically clean metal. The flux used is a rosin flux which aids in mechanical resistance and electrical contact of the electrical connections. Sometimes it is also possible to apply a wetting agent to reduce surface tension. There are so many different types of solder on the market today that it can be difficult to choose the right one for your project.