Why does solder paste need to be stored in a refrigerator?

Refrigerating solder paste significantly extends the life of the paste. In general, manufacturers recommend storing solder their pastes between 0 and 10 °C (32 – 50 °F), but customers should confirm this with each manufacturer’s specific instructions for storage. The paste should be stored within this range, either in a refrigerator or cold room, as soon as it is received from Kimco Distributing Corp.

Solder pastes are comprised of flux and powdered solder alloy. (Alternatively, Kimco Distributors also carries flux without powder in it.). The flux in solder paste serves two functions. During the soldering process, it efficiently conducts heat. It also removes impurities, both on the components being soldered and the powdered allow. Thus, even when solder paste is being stored, the flux is reacting with the powder suspended in it.

These chemical reactions that the flux induces can be slowed by storing the solder paste at cool temperatures. Manufacturers recommend the above range of temperatures, because they have designed solder pastes to not react as quickly at cooler temperatures. Their chemists carefully select compounds that will react quickly at higher temperatures but are fairly dormant at lower temperatures.

When properly stored, most of the solder pastes Kimco Distributing Corp. carries have a shelf life of approximately six months. (Again, check with each manufacturer’s specifications to confirm this). Once pastes reach room temperature, though, they will quickly expire – some in as little as 24 hours. This is why refrigerating solder paste is so important.