Solder paste is traditionally made of a couple of materials. Tin and lead used to be the most common materials in soldering paste. Recent legislation, however, has discouraged the use of lead in many products leading to a movement of lead-free soldering paste manufacturing. One popular mixture for soldering paste consists of 99.7 percent tin and 0.3 percent copper.
Soldering paste is most widely employed in the assembly and mass production of printed circuit boards and prototype PCBs. Soldering paste enables the production of high quality soldering joints when used properly. Some level of expertise is required to use soldering paste properly because very specific amounts need to be applied to the correct places; there is no room for mistakes. Soldering paste should be brought up to room temperature for use and should never be used past its "use by" date.
It is essential to the proper functioning of soldering paste that it be stored under the right conditions. Soldering paste should be stored in an airtight container to prevent oxidation. Soldering paste must also be stored in a low-temperature environment to reduce the rate of oxidation and decrease the degrading rate. However, it should never be stored below freezing.
Soldering paste has a clearly defined shelf life. This material should never be used after its expiration date because of the risk of ineffectiveness and to avoid having to rework a project because degraded paste was used. Excessive heat can cause the flux to separate from soldering paste.
If your skin comes in contact with soldering paste, wash it immediately under running water. Contaminated clothing should be properly cleaned before being worn again. Avoid inhalation of the fumes produced by soldering paste.