The preservation of lead-free solder paste
should be stored in a sealed form in a refrigerator with constant temperature and humidity (note that it is refrigerated instead of freezing). There are special freezers for lead-free solder paste on the market, and the temperature is 2℃～8℃ If the temperature is too high, the alloy powder in the lead-free solder paste does not chemically react with the flux, which will reduce the viscosity and activity and affect the performance of the lead-containing solder paste; if the temperature is too low , it will cause crystallization and deteriorate the shape of the solder paste.
During the storage process of lead-free solder paste, attention should be paid to maintaining a "constant temperature". If the lead-free solder paste is continuously changed from various environments to different temperature changes in a short period of time, It will also change the flux properties in the solder paste, thereby affecting the soldering quality of the leaded no-clean solder paste.
Scraper speed: ensure that the solder paste rolls rather than slides relative to the scraper. Generally, 10-20mm/s is appropriate;
Squeegee pressure: ensure that the printed solder joint has a clear edge, a flat surface and a suitable thickness.
Printing method: contact printing is appropriate; when using, the lead-free solder paste should be fully stirred, and then added to the printing screen according to the set amount of printing. If the dispensing process is used, the dispensing amount should be adjusted. ; In the case of long-term printing, due to the volatilization of the flux in the solder paste, it will affect the release performance of the solder paste during printing, so the container for storing the solder paste cannot be reused (only for one-time use), after printing The remaining solder paste on the stencil should be stored in other clean containers, and the remaining lead-free no-clean solder paste should be checked for agglomeration or solidification next time it is used.