Essentials of manual welding technology
1, the printed circuit board mounting and welding before preparation
Before welding, the component leads should be cut off the excess after hanging tin. If the component surface is oxidized is not easy to hang tin, you can use fine sandpaper or knife to clean up the lead surface, with the tip of the soldering iron dipped in the appropriate amount of rosin core solder to the lead to hang tin (as shown in the figure).
If you can not hang on the tin, you can put the component leads on the rosin block, and then gently touch the lead with the tip of the soldering iron, and at the same time, turn the lead, so that the lead surface can be uniformly hung tin. Each lead should not be too long to hang tin time, generally 2 to 3 seconds is appropriate, so as not to burn the internal components, especially for diodes, transistors pins hanging tin, it is best to use metal tweezers to clamp the lead by the part of the tube shell, in order to pass away part of the heat.
In addition, the pins of various components should not be cut too short, otherwise it is not conducive to heat dissipation, but also not easy to weld.
2, printed circuit board welding
Welding, hang a good tin component leads placed in the location to be welded, such as the printed board pad holes or a variety of joints, sockets and switches in the small holes in the pads, with the appropriate amount of tin soldering iron head in the welding part of the stay for about 3 seconds, to be taken away by the soldering iron, the weld to form a smooth welded joints.
In order to ensure the quality of welding, it is best to weld the position of the component leads beforehand also hung on the tin. Soldering to ensure that the position of the lead does not move, otherwise it is very easy to produce virtual welding.
Soldering iron tip stay time should be moderate, too long will burn the components, too short will be due to welding dissolved insufficiently and cause false welding.
3, post-soldering treatment
After welding, to carefully observe the shape and appearance of the solder joint.
Solder joints should be hemispherical and height slightly less than the radius, should not be too bulging or too flat, the appearance should be smooth and uniform, no obvious air holes or depressions, otherwise it is easy to cause false soldering or false soldering.
In a soldering point at the same time welding several components of the lead, more attention should be paid to the quality of the soldering point.
