Printed boards should be drilled to eat tin (solder is melted with soldering iron and plated on the surface of copper foil). After eating tin, insert the resistor leg into the hole and then weld it. After cooling, lose the extra legs. Other parts are welded in this way. Transistors and diodes are afraid of scalding. The welding time should be as short as possible, and the legs should not be too short. If necessary, clamp your legs with small pliers to dissipate heat.

Before welding, clean the legs of the parts and remove the oxidized surface (scrape it off with a knife, sandpaper, etc.). ) The soldering iron should be dipped in rosin first, and then in tin. Only with rosin tin can it be easily electroplated on copper.