The temperature required is just above the melting point of the solder. The solder is allowed to flow in the joint. After reflow, the solder is allowed to cool naturally and re-solidify. Necessary to rid the surface of the metals to be joined of oxides, to promote wetting and obtain intimate contact between the solder and base metal. However, it is difficult to clean off after the process.
Intermediate fluxes contain organic compounds and decompose at soldering temperatures.
They are suitable for all materials that are solderable with mild fluxes. They are a good choice for electronic and critical soldering applications. Common Problems Low unit strength. If the temperature is too high, a strong joint cannot be created.