Welding techniques and essentials of electric soldering iron
1. Surface treatment of welding parts
The welding components encountered in manual soldering iron welding are various electronic parts and wires. Unless electronic components within the "insurance period" are used under large-scale production conditions, surface cleaning work is usually required to remove rust, oil stains, dust and other impurities that affect the welding quality from the welding surface. Simple and easy methods such as mechanical scraping and alcohol, acetone scrubbing, etc. are commonly used in manual operations.
2. Pre welding
Pre soldering refers to wetting the lead wires or conductive welding parts of the components to be soldered with solder in advance, commonly known as tin plating, tin coating, tin coating, etc. Prewelding is accurate because its process and mechanism are all the entire process of soldering - the solder wets the surface of the solder, and forms a bonding layer through the diffusion of metal, resulting in a layer of solder coating on the surface of the solder.
Pre soldering is not an indispensable operation for soldering, but it is almost essential for manual soldering, especially for maintenance, debugging, and development work.
3. Do not use excessive flux
An appropriate amount of flux is essential, but don't think that more is better. Excessive rosin not only causes the workload of cleaning around the solder joint after welding, but also prolongs the heating time (rosin melting, volatilization, and heat carried away), reducing work efficiency; When the heating time is insufficient, it is easy to be mixed into the solder and form "slag inclusion" defects.
When welding switch components, excessive flux can easily flow to the contacts, resulting in poor contact. The proper amount of soldering flux should be that the loose perfume can only wet the solder joint to be formed, and the loose perfume should not flow into the component surface or socket hole (such as IC socket) through the printed board. For welding wires with rosin core, there is basically no need to apply flux again.
4. Keep the soldering iron tip clean
Because the soldering iron head is in a high-temperature state for a long time during welding and comes into contact with substances such as flux that undergo thermal decomposition, its surface is easily oxidized and forms a layer of black impurities, which almost form an insulation layer, causing the soldering iron head to lose its heating effect. Therefore, it is necessary to wipe away impurities on the soldering iron frame at any time. It is also a common method to wipe the soldering iron head with a damp cloth or sponge at any time.
5. Heating relies on solder bridges
In non assembly line operations, there are various shapes of solder joints that can be welded at once, and we cannot constantly change the soldering iron head. To improve the heating efficiency of the soldering iron head, it is necessary to form a soldering bridge for heat transfer. The so-called solder bridge is a bridge that retains a small amount of solder on the soldering iron as a heat transfer bridge between the soldering iron head and the weldment during heating.
Obviously, due to the much higher thermal conductivity efficiency of liquid metal compared to air, the weldment is quickly heated to the welding temperature. It should be noted that the amount of tin retained as a solder bridge should not be too much.
6. The soldering amount should be appropriate
Excessive soldering not only unnecessarily consumes more expensive tin, but also increases soldering time and correspondingly reduces working speed. More seriously, in high-density circuits, excessive tin can easily cause undetectable short circuits. However, too little soldering cannot form a solid bond, reducing the strength of solder joints, especially when soldering wires on the board, insufficient soldering often leads to wire detachment.
7. Weldments should be firm
Do not move or vibrate the solder before it solidifies, especially when using tweezers to clamp the solder. Be sure to wait for the solder to solidify before removing the tweezers. This is because the solidification process of solder is a crystallization process. According to crystallization theory, external forces (welding piece movement) during the crystallization process will change the crystallization conditions, leading to crystal coarseness and the so-called "cold welding".
The appearance phenomenon is that the surface is matte and in the shape of bean residue; The internal structure of the solder joint is loose, prone to air gaps and cracks, resulting in a decrease in the strength of the solder joint and poor conductivity. Therefore, before the solder solidifies, it is necessary to keep the solder stationary. In practical operation, various suitable methods can be used to fix the solder or reliable clamping measures can be used.
8. Tips for removing soldering iron
The evacuation of soldering iron should be done in a timely manner, and the angle and direction during evacuation have a certain relationship with the formation of solder joints. Gently rotate the soldering iron when removing it to maintain the appropriate amount of solder at the solder joint, which needs to be experienced in practical operation.
