Lead tin solder paste is a type of solder paste specially designed and developed for SMT assembly production lines. It is an indispensable soldering material in the SMT pick-and-place machine industry. Lead tin solder paste is composed of flux and alloy components, with tin and lead being the main components, hence the name lead tin solder paste. Solder paste alloys typically contain trace amounts of impurity metals such as antimony, zinc, copper, aluminum, silver, mercury, and arsenic. The melting point is 183°C, and the composition is Sn63Pb37. It is mainly divided into LED-specific solder paste, QFN lead tin solder paste, and SMT-specific solder paste.
The viscosity determination can be done using the following method:
- Take out the lead tin solder paste and let it thaw for 3-4 hours at room temperature.
- Mix manually with a stirring knife for 3-5 minutes.
- Use a knife to pick up some solder paste from the jar and observe its descent when held about ten centimeters away from the jar.
- If the solder paste slowly and evenly descends, it indicates that the viscosity is moderate. If the solder paste does not come down from the knife, it indicates that the viscosity is too high, meaning the solder paste has low moisture retention. If large chunks fall down, it indicates that the viscosity is too low, and the solder paste has excessive moisture retention. Generally, solder paste with appropriate viscosity should be used.
As for cleaning solder paste stencils, there are specialized cleaning devices available, such as the Silman Tech Stencil Cleaning Machine DEZ-C730. It is a fully pneumatic stencil cleaning machine designed for cleaning various types of stencils used in the electronics industry, including SMT stencils, silk screens, photoresist stencils, micro-hole stencils, and wafer carriers. This equipment operates entirely on compressed air as the energy source, eliminating any risk of fire hazards. It features user-friendly design, one-button operation, and easy completion of cleaning and drying tasks. It is a high-performance cleaning device that operates fully automatically using air pressure.
