Does solder paste expire?

Solder pastes can expire. The shelf life of solder pastes generally ranges from 6 months to 1 year, with finer ultra-micro solder pastes or epoxy pastes having a somewhat broken shelf life of 3-6 months storage life. The specific shelf life can be affected by a variety of factors, including manufacturer's labelling, storage conditions and frequency of use.

Factors affecting shelf life

Production date and manufacturer labelling: the shelf life of the solder paste will first be based on the manufacturer's label to determine, usually in the product packaging is clearly marked with the date of production and shelf life.

Storage conditions: The storage conditions of solder paste have a significant impact on its shelf life. Generally speaking, solder paste should be sealed and stored in a cooler with constant temperature and humidity, with the temperature set between 2℃ and 8℃. If the storage temperature is too high, the alloy powder and flux in the solder paste may accelerate the chemical reaction, resulting in a decline in its performance; if the storage temperature is too low, certain components in the flux may solidify and crystallise and grow, again affecting the soldering effect. In addition, solder paste should also avoid moisture and direct sunlight to maintain its performance stability.

Frequency of use: How often solder paste is used also affects its shelf life. Frequent opening and closing of packaging can cause solder pastes to come into contact with moisture and oxygen in the air for extended periods of time, which can accelerate oxidisation and deterioration of their properties.

Consequences of expired solder paste

After the expiration date of the solder paste, its internal composition may change, such as flux failure, viscosity increase, reduced fluidity and so on. These changes will directly affect the use of solder paste performance and soldering performance, resulting in a decline in soldering quality, such as the following tin is not smooth, black solder joints, poor soldering, bubble generation. In addition, expired solder paste may also release harmful gases, posing a threat to the health of operators.

Storage and use recommendations

Storage recommendation: Solder pastes should be kept sealed in a cooler at constant temperature and humidity, with the temperature set between 2°C and 8°C. Some syringe solder pastes or epoxy solder pastes are stored at a somewhat lower temperature and kept in a frozen state, e.g. at -20°C. Unopened solder pastes generally have an expiration date ranging from 6 months to 1 year when storage conditions are met. Opened solder pastes should be used as soon as possible and stored resealed to minimise exposure to air.

Suggestions for use: When using solder paste, the principle of first-in-first-out should be followed, and priority should be given to the use of solder paste opened earlier.At the same time, the state of the solder paste should be checked regularly, and any lumps, discolouration and other phenomena should be disposed of or discarded in time.Before use, the solder paste should be fully rewarmed and then stirred to ensure its uniformity.

In summary, solder pastes can expire and when they do, they can have an adverse effect on the quality of the solder and the health of the operator.Therefore, when using solder paste, you should pay attention to check its production date and shelf life, and strictly in accordance with the storage conditions for preservation and use.