First, in principle, the higher the wave soldering peak is, the larger the surface is in contact with the air, and the more severe the solder oxidation, the more the dross is. Therefore, the wave soldering peak should not be too high, generally not more than 1/3 of the thickness direction of the printed circuit board, that is, the peak tip should exceed the soldering surface of the printed circuit board, but can not exceed the component surface.
Secondly, if the peak of the wave soldering is unstable, the liquid solder will easily bring the air into the molten solder when it falls back from the peak, which accelerates the oxidation of tin. During the wave soldering process, the copper on the surface of the printed circuit board and the lead of the electronic components The copper on it will continuously dissolve into the molten solder. A Cu6Sn5 intermetallic compound is formed between copper and tin, and the melting point of the compound is above 500 ° C, so the solder bar exists in a solid form. At the same time, since the density of the compound is 8.28 g/cm3, and the density of the Sn63Pb37 solder bar is 8.80 g/cm3, the compound generally exhibits a bean curd floating on the surface of the liquid solder.
Finally, the work of removing copper from the wave soldering process is very important. The operation is as follows: stop the peak, the heating device of the tin furnace works normally, first clean the various residues on the surface of the tin furnace, expose the mercury-like mirror state, and then reduce the temperature of the tin furnace by 190-200 ° C (the solder is still in the liquid state at this time) Then, stir the solder for 1-2 minutes with a tool such as an iron spoon to help the tin-copper compound inside the solder float and then let stand for 3-5 hours. Since the density of the tin-copper compound is small, the tin-copper compound naturally floats on the surface of the solder after standing, and the tin-copper compound on the surface can be cleaned by using a tool such as an iron spoon.