Selection of Flux Activity

Flux isSteel Solder Pasteone of the main components of the carrier. Solder paste can use three different types of flux, namely R flux (rosin flux), RMA flux (mildly activated rosin flux), and RA flux (fully activated rosin flux). The activators in mildly activated and fully activated rosin fluxes can remove oxides and other surface contaminants from metal surfaces and facilitate the penetration of molten solder into surface mount pads and component terminals or pins. Depending on the cleanliness of the surface-mounted printed circuit board and the freshness of the components, medium activity is usually selected, with high activity or inactive levels and super activity levels chosen as necessary. Steel solder paste.

Selection of Viscosity

The viscosity of steel solder paste is selected based on the coating method, and the viscosity of the paste depends on the characteristics of the coating process (e.g., screen mesh, squeegee speed, etc.). For screen printing, a viscosity of 100-300 Pa is typically chosen; for stencil printing, a higher viscosity in the range of 200-600 Pa should be selected. For injection dispensing, the viscosity should be 100-200 Pa.

Selection of Metal Content

　　Steel Solder PasteThe metal content determines the size of the solder joint. The solder joint increases with an increase in metal percentage; however, when the metal content at a given viscosity increases, slight changes in metal content in the solder will have a significant impact on solder joint quality. For example, for the same thickness of solder paste, a 10% change in metal content can cause the solder joint to go from excessive to insufficient. Typically, the metal content for solder paste used for surface-mounted components should be between 88% and 90%.

Selection of Solder Particle Size

The shape of solder particles determines the oxygen content in the powder and the printability of the solder paste. Spherical powder is superior to oval powder. The smaller the spherical surface, the lower the oxidation capability.