The choice of solder paste: the melting point matches
In order to match the use of the solder, the melting point of the selected solder paste should be lower than the melting point of the solder by 10-30 °C. If the melting point of the solder paste is too low than the melting point of the solder, it will melt too early and lead to premature failure of the flux active ingredient.
According to the surface oxide film characteristics
For alkaline oxide films, an acidic solder paste should be selected; for acidic oxide films, an alkaline flux should be selected.
According to the brazing process
According to the specific process, choose different types of solder paste. For example, liquid solder paste should be selected for wave soldering. Paste flux should be selected for high frequency or medium frequency induction brazing. Powder flux or paste flux should be selected for flame brazing. and many more.
According to the characteristics of the substrate
Different matrix materials have different types of solder pastes due to different surface oxide films, especially some difficult-to-weld metals, such as magnesium-containing aluminum alloys, stainless steels, and hard alloys. In order to ensure the welding performance of the magnesium-containing aluminum alloy, a flux having a stronger activity is usually selected.