Solder paste is applied to surface mount boards prior to pick and place and when passed through an infra-red reflow machine, melts to provide the soldered joints.
◉ Solder paste is a mixture of minute solder spheres held within a specialised form of solder flux. As the name indicates it has the texture of a paste, and hence the name.
◉ The fact that it is a paste means that it can be easily applied to the board during PCB assembly.
◉ The solder particles are a mixture of solder. Traditionally this used to be tin and lead, but with the legislation has been introduced around the world, to only use lead free solders. These may be made from a variety of mixtures. One is 99.7% tin and 0.3% copper, whereas there are other mixtures that include other metals including tin.
