Correct use of electric soldering iron in circuit maintenance, precautions and usage tips
1. How to grip an electric soldering iron
① Pen holding technique
The grip method is suitable for low-power and straight soldering iron tips, and is suitable for soldering small heat dissipation components such as printed circuit boards in instruments. The grip technique is the most commonly used method by instrument workers.
② Positive grip technique
The positive grip method is suitable for soldering irons with larger and curved tips. Can be used for soldering when the circuit board is perpendicular to the desktop.
③ Reverse grip method
The reverse grip method is to hold the handle of the soldering iron in the palm with five fingers. This method is suitable for high-power electric appliances, soldering irons, and welded components with high heat dissipation.
2. Select soldering iron according to its purpose
When soldering conventional components on printed circuit boards, such as diodes, transistors, resistive capacitive elements, and integrated circuits, it is advisable to use a 20-30W internal heating soldering iron. For beginners, due to slow welding speed, it is recommended to use a 20W one. When soldering devices with large pins or large-area grounding points and power type connectors on printed circuit boards, it is advisable to use a 45-75W soldering iron to ensure the firmness between the soldered components and the printed circuit board or wires. Do not use a low-power soldering iron to solder the solder joints of large electronic components. Due to fast heat dissipation, the temperature of the soldering iron tip drops quickly, resulting in solder accumulation. It may appear to be soldered, but in reality, it is virtual soldering. Using a high-power soldering iron to solder general electronic components on a printed circuit board often burns out copper foil lines or electronic components.
3. Master the correct welding steps
The level of welding determines the stability and reliability of the instrument being repaired. The quality issue of small solder joints may cause the entire instrument or control system to malfunction, and the fault points are generally very hidden. So mastering the correct welding steps is the key to ensuring welding quality. Now let me introduce it.
① Place the soldering iron tip at the pin of the component to be soldered and heat the solder joint first. When the solder joint reaches the appropriate temperature, melt the rosin solder wire on the solder joint in a timely manner.
② After the tin melts, the soldering iron tip should be slightly moved according to the shape of the solder joint, so that the solder evenly covers the solder joint and penetrates into the gaps of the solder surface. After melting the appropriate amount of solder, the solder wire should be quickly removed.
③ When the solder on the solder joint is almost full, the flux has not completely evaporated, the temperature is appropriate, and the solder is at its brightest and most flowing, quickly move the soldering iron tip along the direction of the component pin. When it is about to leave, quickly bring it back and leave the solder joint at the same time to ensure that the surface of the solder joint is bright, smooth, and free of burrs. Finally, use diagonal pliers to cut off the excessively long component pins, leaving the solder joints slightly exposed.
The time for the operation process in steps ① and ② should be controlled within 2-3 seconds. Beginners usually have longer soldering time, and long heating time may damage the copper foil on the printed circuit board and cannot be repaired. Step 3 plays a decisive role in the quality of solder joints, and it is important to practice and understand its essentials.
