1. The degree of surface wetness: the molten solder shall spread out on the surface of the metal to be welded and form a complete, uniform and continuous covering layer with a contact Angle of no more than 90 degrees.
2.The amount of solder > correct amount of solder, solder enough but not too much or too little.
3, the surface of the solder joint surface solder joint surface should be complete, continuous and smooth, but does not require an extremely bright appearance.
4. Solder joint position The position of the solder joint or the lead of the component on the pad is within the specified range.