What temperature should be paid special attention to when storing solder paste in Tin Pail?

1. Storage temperature range
Lead-free solder paste (such as SAC305, SAC0307): It needs to be stored in a refrigerator or constant temperature cabinet at **2~10℃**. Too high temperature (over 10℃) may cause the flux to fail, and too low temperature (below 0℃) may cause the alloy powder to crystallize.
Low-temperature solder paste (such as SnBi series): Some models need to be stored at **-5~5℃**, please refer to the supplier's instructions for details.
2. Temperature control and monitoring
Temperature monitoring: There should be a special thermometer in the refrigerator to detect the storage temperature every 12 hours and keep records. The thermometer needs to be calibrated regularly to prevent failure.
Avoid temperature fluctuations: The storage temperature should be kept as stable as possible to avoid temperature fluctuations caused by frequent switching of refrigeration equipment.
3. Reheating treatment before use
Reheating requirements: After taking out the solder paste from the refrigerator, it needs to be naturally warmed up at room temperature (20~25℃). The reheating time is usually 2 to 4 hours, and the specific time depends on the amount of solder paste (such as 500g solder paste takes about 3 hours). If the solder paste is opened and used directly without reheating, it is easy to cause water vapor in the air to condense on the surface of the solder paste, and "tin explosion" may occur during welding.
No heating: It is forbidden to use heating equipment (such as ovens, hot air guns) to accelerate the reheating, otherwise it will cause the flux to volatilize prematurely and destroy the performance of the solder paste.
4. Other precautions
Sealed storage: The solder paste must be kept sealed during storage to prevent water vapor and dust in the air from entering and contaminating the solder paste.
Follow the first-in-first-out principle: store by batch classification, and give priority to the solder paste purchased earlier.
Avoid repeated freezing and thawing: After the solder paste is taken out of the refrigerator, if it is not used up, it cannot be directly put back into the refrigerator for repeated freezing and thawing, otherwise it will cause the flux and tin powder to separate and affect the uniformity.