Solder paste is generally produced for small and medium batches and multiple varieties. A bottle of solder paste will take a long time and be used many times. In this way, the preservation of solder paste is different from those mass production lines that use one bottle, several bottles, or even dozens of bottles at a time.
One: The basic principle for the use and storage of solder paste is to minimize its contact with air, the less the better. After the solder paste is in contact with the air for a long time, it will cause the oxidation of the solder paste and the imbalance of the proportion and composition of the flux. The consequences are: the solder paste appears crusty, lumpy, refractory and produces a large number of solder balls.
Two: Precautions when using a bottle of solder paste multiple times
1: The time for opening the cover should be as short as possible. After taking out enough solder paste, the inner cover should be closed immediately. Do not take a little and use a little, open the lid frequently or keep the lid open all the time.
2: Close the cover, take out the solder paste, cover the inner cover immediately, press down firmly, squeeze out all the air between the cover and the solder paste, and make the inner cover closely contact with the solder paste. Make sure that the inner cover is tightly pressed before screwing on the outer large cover.
3: The removed solder paste should be printed as soon as possible, and the removed solder paste should be printed and used as soon as possible. The printing work must be continuous without stopping, and all the PCB boards to be processed on duty are printed in one go, and they are placed flat on the workbench to wait for the surface mount components to be placed.
4: Disposal of the excess solder paste that has been taken out. After all printing is completed, the remaining solder paste should be recycled into a special recycling bottle as soon as possible, and kept in isolation from the air as in Note 2. Never put leftover solder paste back into an unused solder paste bottle! Therefore, when taking solder paste, try to accurately estimate the amount of solder paste used on duty, and take as much as you use.
5: Troubleshooting, if there is a crust on the surface of the solder paste and hardening, do not stir it! Be sure to remove the hard skin and lumps. The remaining solder paste should be tested before it is officially used to see how it works. If it doesn’t work, it can only be scrapped.
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