Summary of soldering essentials for electric soldering iron
1. The contact method between the soldering iron tip and the two parts to be welded
(1) Contact position
The soldering iron tip should be in contact with the two welded parts to be connected to each other (such as solder feet and pads) at the same time. The soldering iron is generally inclined at 45 degrees to avoid contact with only one of the welded parts.
When the heat capacity of the two welded parts is very different, the inclination angle of the soldering iron should be adjusted appropriately. The smaller the inclination angle between the soldering iron and the welding surface, the larger the contact area between the welded part with the larger heat capacity and the soldering iron will be, and the heat conduction capacity will be enhanced.
For example, the inclination angle of LCD pull welding is about 30 degrees, and the inclination angle of welding microphones, motors, speakers, etc. can be about 40 degrees. Two parts to be welded can reach the same temperature in the same time, which is considered as an ideal state of heating.
(2) Contact pressure
When the soldering iron tip is in contact with the workpiece to be welded, a slight pressure should be applied. The strength of heat conduction is proportional to the applied pressure, but it must be based on the principle of not causing damage to the surface of the workpiece to be welded.
2. The supply method of welding wire
The supply of welding wire needs to master three essentials, namely supply time, location and quantity.
(1) Supply time: In principle, the solder wire is sent immediately when the temperature of the welded part reaches the melting temperature of the solder.
(2) Supply position: It should be between the soldering iron and the welded part and as close to the pad as possible.
(3) Quantity to be supplied: It depends on the size of the weldment and the pad. After the solder covers the pad, the solder can be higher than 1/3 of the diameter of the pad.
3. Welding time and temperature setting
(1) The temperature is determined by the actual use. It is most suitable to solder a solder point for 4 seconds, and the maximum is no more than 8 seconds. Usually observe the tip of the soldering iron. When it turns purple, the temperature setting is too high.
(2) For general in-line electronic materials, set the actual temperature of the soldering iron tip to (350~370 degrees); for surface mount materials (SMC) materials, set the actual temperature of the soldering iron tip to (330~350 degrees)
(3) For special materials, the temperature of the soldering iron needs to be specially set. FPC, LCD connectors, etc. should use silver-containing tin wire, and the temperature is generally between 290 degrees and 310 degrees.
(4) When soldering large component feet, the temperature should not exceed 380 degrees, but the power of the soldering iron can be increased.
4. Precautions for welding
(1) Before welding, observe whether each solder joint (copper skin) is smooth and oxidized.
(2) When welding items, look at the welding point to avoid short circuit caused by poor welding of the line.
