(1) Contact mode between soldering iron head and two welded parts

Contact position: The soldering iron head should simultaneously contact the two welded parts to be connected to each other (such as welding feet and pads). The soldering iron is generally inclined at 45 degrees, and contact with only one of the welded parts should be avoided. When there is a significant difference in heat capacity between two welded parts, the tilt angle of the soldering iron should be adjusted appropriately. The smaller the tilt angle between the soldering iron and the welding surface, the larger the contact area between the welded part with larger heat capacity and the soldering iron, and the stronger the heat conduction ability. When welding LCD, the tilt angle is around 30 degrees, and when welding microphones, motors, speakers, etc., the tilt angle can be around 40 degrees. The ability of two welded components to reach the same temperature at the same time is considered an ideal state for heating.

Contact pressure: When the soldering iron head comes into contact with the welded part, slight pressure should be applied. The strength of heat conduction is proportional to the amount of pressure applied, but the principle is to not cause damage to the surface of the welded part.

(2) Supply method of welding wire

The supply of welding wire should grasp three key points, namely the supply time, position, and quantity.

Supply time: In principle, the solder wire is immediately sent when the temperature of the welded part reaches the melting temperature of the solder.

Supply position: It should be between the soldering iron and the welded part and as close as possible to the solder pad.

Supply quantity: It should depend on the size of the soldered parts and pads. After covering the pads with solder, the solder should be higher than 1/3 of the pad diameter.

Fpc, fpc connector

(3) Welding time and temperature settings

A. The temperature is determined by actual use, and it is most suitable to weld a tin point for 4 seconds, with a maximum of 8 seconds. Usually, observe the soldering iron head, and when it turns purple, the temperature is set too high.

B. Generally, insert electronic materials directly and set the actual temperature of the soldering iron head to (350~370 degrees); Surface Mount Material (SMC) material, set the actual temperature of the soldering iron head to (330-350 degrees)

C. Special materials require special setting of soldering iron temperature. FPC, LCD connectors, etc. need to use silver containing tin wire, with a temperature generally between 290 degrees and 310 degrees.

D. Welding large component feet should not exceed 380 degrees Celsius, but it can increase the power of the soldering iron.

(4) Welding precautions

A. Before welding, each welding point (copper sheet) should be observed for smoothness, oxidation, etc.

B. When welding items, it is important to look at the welding points accurately to avoid short circuits caused by poor soldering of the circuit