1. 1 operating posture. When operating manually, we should pay attention to maintaining the correct posture, which is beneficial to health and safety. The correct operating posture is: sit up straight, hold your chest out, and don't bend over. The distance from the tip of the nose to the tip of the welding head should be at least 20cm, usually 40cm. 1.2 Holding method of electric soldering iron. Generally, the posture of holding an electric soldering iron is as shown in the figure, about 45 degrees away from the welding surface like holding a pen. Solder procurement
1.3 welding wire. -The commonly used solder wire is a kind of solder wire coated with flux, which has various specifications such as 0.8mm in diameter, 1.0mm, 1.2mm, etc., and can be used as appropriate; -Flux, which can remove impurities on the surface of welded metal, prevent oxidation, increase the penetration of solder and improve the reliability of welding;
2 welding
Manual welding, as an operation technique, is very effective for mastering welding technology quickly through the training of five-step welding method. Five-step welding method, also called five-step operation method, is the basic method to master manual welding. 2. 1 ready. Prepare the workpiece to be welded, heat the soldering iron to the working temperature, keep the welding head clean, eat tin well, hold the soldering iron in one hand and solder wire in the other, and separate the soldering iron and solder wire on both sides of the workpiece to be welded. Solder procurement
2.2 heating. When the welding head touches the weldment, the whole weldment, including the workpiece terminal and pad, should be heated uniformly. Do not apply pressure or drag the soldering iron at will, and the appropriate time is about 1 ~ 2 seconds. Solder procurement
2.3 Add welding wire. When the welding part of the workpiece is heated to the welding temperature, the welding wire is sent to contact with the welding spot of the workpiece, melting and wetting the welding spot. The solder should contact the weldment from the reverse side of the soldering iron. The amount of tin should be appropriate. Generally, it is better to use a uniform and thin layer of solder, which can completely wet the whole solder joint. Qualified solder joints should be conical, without tailing, with slightly concave surface and metallic luster, and the lead outline can be vaguely distinguished from the solder joints. If too much solder is piled up, some hidden defects may be hidden inside, and the strength of solder joints may not be high; However, if the solder is filled too little, the whole solder joint cannot be completely wetted. Solder procurement
2.4 Move to bonding wire. After a proper amount of solder melts (at this time, the welding part has fully absorbed the solder and formed a thin solder layer), the welding wire is quickly taken out. Solder procurement
6.2.5 Remove the soldering iron. After removing the solder wire, remove the soldering iron quickly before the flux (contained in the tin wire) has completely evaporated, otherwise it will leave a bad solder joint. The vacuumizing direction of electric soldering iron is related to the amount of residual solder, which is generally vacuumizing at 45 degrees to the axial direction. The soldering iron should be recycled after it is evacuated, and the recycling action should be quick and skilled to avoid the formation of sharp points; When the electric soldering iron is used, it should be rotated gently to absorb excess solder. The whole process from removing the soldering iron to welding parts to removing the soldering iron takes 2 ~ 3 seconds. The time is too short and the welding is unreliable; It is easy to damage parts if it takes too long. Solder procurement
3 welding precautions
3. 1 There should not be too much solder, only the terminals can be soaked. One solder joint was successful. If repair welding is needed, the welding head can only be removed after the two solders are melted together. If the solder joint is not smooth, it can be repaired with solder wire until it is satisfactory. 3.2 In the process of solder cooling, the weldment should not shake, otherwise it will easily lead to virtual welding.
4 Manual welding technical essentials
4. 1 The surface of weldment shall be clean, and the welding head shall be kept clean. 4.2 The amount of solder should be appropriate, and do not use excessive flux. Solder procurement
Too much flux not only increases the workload of cleaning after welding and prolongs the working time, but also causes "slag inclusion" when heating is insufficient. Suitable flux can only wet the solder joint to be formed when melting, and will not flow into the component surface or socket. 4.3 Adopt correct heating method and appropriate heating time. When heating, heat transfer should be accelerated by increasing the contact area. Don't use soldering iron to exert force on butt welding parts, because this will not only accelerate the loss of welding head, but also cause damage or hidden dangers of components. Therefore, the welding head and the weldment should be in surface contact, not point or line contact, and the part of the weldment that needs solder infiltration should be heated evenly. When heating, the appropriate heating time should be selected according to the operation requirements, and the whole process should be 2 ~ 3 seconds. If the heating time is too long and the temperature is too high, the components will be damaged, the solder joints will turn white and even the copper foil on the printed circuit board will fall off. However, if the heating time is too short, the solder has poor fluidity and is easy to solidify, making the solder joint "tofu residue". 4.5 The weldment shall be fixed before the solder solidifies. Do not move or vibrate the weldment, otherwise it will cause "cold welding", which will make the internal structure of the solder joint loose, reduce the strength and have poor conductivity. 4.6 Pay attention to the evacuation of soldering iron, and don't use soldering head as a tool to carry soldering tin. The soldering iron should be evacuated in time, and the angle and direction of evacuation have a certain relationship with the formation of solder joints. Generally, 45 axial dispersed soldering iron is suitable. Because the temperature of welding head is generally above 300℃, the flux in solder wire is easy to decompose and fail at high temperature, so using welding head as a tool to carry solder is easy to cause solder oxidation and flux volatilization; During debugging or maintenance, when welding with welding head, the action should be quick and agile to prevent the poor quality of solder joints caused by oxidation.