Hand soldering is the basis of tin-lead soldering technology. Although modern enterprises have generally used automatic insertion and automatic welding production processes, product trial production, production of small batch products, and production of high-reliability products with special requirements (such as the manufacture of rockets and artificial satellites in aerospace technology) are currently Manual welding is also used.

 

 

Even if the printed circuit board structure is such a miniaturized and mass-produced product that uses automatic welding, there are still a certain number of welding points that need to be manually welded, so there is no welding method that can completely replace manual welding. Therefore, in the process of cultivating high-quality electronic technicians and electronic operators, manual welding technology is an indispensable training content.

Precautions:

1. Choose suitable solder, and low melting point solder wire for soldering electronic components.

2. Flux, use 25% rosin dissolved in 75% alcohol (weight ratio) as a flux.

3. The electric soldering iron should be tinned before use. The specific method is: heat the electric soldering iron, and when the solder can be melted, apply flux, and then apply the solder evenly on the tip of the soldering iron to make the tip of the soldering iron evenly eaten. One layer of tin.

4. The soldering method, polish the pads and component pins with fine sandpaper, and coat them with flux. Dip a proper amount of solder with a soldering iron tip and touch the solder joints. After the solder on the solder joints are all melted and immersed in the component leads, the soldering iron tip is gently lifted up and away from the solder joints along the component pins.

5. The soldering time should not be too long, otherwise the components will be easily burned. If necessary, use tweezers to clamp the pins to help dissipate heat.

6. The solder joints should be in the shape of sine wave peaks, and the surface should be bright and smooth, free of tin thorns, and moderate tin quantity.

7. After the soldering is completed, use alcohol to clean the residual flux on the circuit board to prevent the carbonized flux from affecting the normal operation of the circuit.

8. The integrated circuit should be soldered last, and the electric soldering iron should be grounded reliably, or the residual heat should be used for soldering after power failure. Or use dedicated sockets for integrated circuits, and then plug in the integrated circuits after soldering the sockets.

9. The electric soldering iron should be placed on the stand of the soldering iron.

 

Flux:

The flux can be dripped in a small bottle, and a sealed or refillable flux pen can be used. Often, operators use too much flux. I would rather use flux pens because they limit the amount of flux used. I would also prefer to use flux cored solder, which contains flux and solder alloy. When using solder with a flux core and liquid flux, ensure that the flux is compatible with each other.

 

Surface mount soldering usually requires a smaller diameter tin wire, typically in the range of 0.50~0.75mm. Through-hole soldering usually requires a larger diameter tin wire, ranging from 1.20 to 1.50 mm.

 

The solder paste can also be dripped with a syringe, although many manual soldering methods heat the solder paste too fast, causing splashing and solder balls. Flux glue, not solder paste, is very useful for replacing area array components.