Correct use of electric soldering iron in circuit maintenance
The electric soldering iron is an essential tool for electronic maintenance, the correct use method, precautions and skills of the electric soldering iron in the maintenance of the instrument circuit. To improve soldering technology, you must first master the use of electric soldering iron.
1. How to hold the soldering iron
① Pencil grip
The pen holding method is suitable for electric soldering irons with low power and straight iron tips, and is suitable for welding parts with small heat dissipation, such as printed circuit boards in welding instruments. The pen-holding method is the most commonly used method for instrumentation workers.
②Forehand grip
The positive grip method is suitable for electric soldering irons with relatively large and curved soldering iron tips. It can be used for soldering when the circuit board is vertical to the desktop.
③ reverse grip
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, soldering iron, and welding parts with large heat dissipation.
2. Select the electric soldering iron according to the purpose
When soldering conventional components on the printed circuit board, such as diodes, triodes, resistance-capacitance components, and integrated circuits, it is advisable to use a 20-30W internal heating electric soldering iron. For beginners, it is recommended to use 20W due to the slow welding speed. When soldering devices with thick pins or large-area grounding points on the printed circuit board, or power-type connectors, it is advisable to use a 45-75W electric soldering iron to ensure the firmness between the soldered components and the printed circuit board or wires. Do not use a low-power electric soldering iron to solder the solder joints of large electronic components. Due to the rapid heat dissipation, the temperature of the soldering iron tip will drop rapidly, which will form solder accumulation. It looks welded, but it is actually a virtual weld. Soldering general electronic components on a printed circuit board with a high-power electric soldering iron often burns copper foil lines or electronic components.
3. Master the correct welding steps
The level of welding determines the stability and reliability of the repaired instrument. The quality problems of small solder joints may cause the entire set of instruments or control systems to fail to work normally, and the fault points are generally very hidden. Therefore, mastering the correct welding steps is the key to ensuring the welding quality, and we will introduce it now.
① Place the tip of the soldering iron at the pin of the component to be soldered, and heat the solder joint first. When the solder joint reaches the appropriate temperature, put the rosin solder wire on the solder joint in time to melt.
② After the tin is melted, the tip of the soldering iron should be moved slightly according to the shape of the solder joint, so that the solder can evenly cover the solder joint and penetrate into the gaps of the soldered surface. After the solder has melted an appropriate amount, the solder wire should be removed quickly.
③When the solder on the solder joint is nearly full, the flux has not yet evaporated completely, the temperature is appropriate, and the solder is brightest and most fluid, quickly move the tip of the soldering iron along the direction of the component pin. When it is about to leave, quickly bring it back, and at the same time Leave the solder joints to ensure that the surface of the solder joints is bright, smooth and free of burrs. Finally, use diagonal pliers to cut off the overly long component leads, and the component leads can be slightly exposed to the solder joints.
The operation time of the above steps ①-② should be controlled within 2-3s. Beginners usually take a long time to solder. Long heating time may damage the copper foil on the printed circuit board and cannot be repaired. The third step plays a decisive role in the quality of the solder joints, and it is necessary to practice a lot to understand its essentials.
4. Protection method of soldering iron tip
Before using the newly purchased electric soldering iron, the tip of the soldering iron should be tinned. For the copper soldering iron tip, you can use sandpaper or a file to polish the tip of the iron. When the temperature rises to the melting point of the solder, use it to dip the rosin solder wire, the surface of the soldering iron tip will be dipped in a layer of bright tin, and the soldering iron tip can be used. A soldering iron tip that is not dipped in tin will not be tinned during soldering, and soldering cannot be performed.
The tip of the soldering iron should be kept clean. Unclean soldering iron tips will oxidize quickly and cannot be tinned. After a long time, it will cause corroded pits on the soldering iron tip, making the soldering work more difficult. The electric soldering iron is in the waiting state for a long time, and the temperature is too high, which will also cause the tip of the soldering iron to "burn to death". Turn off the power supply of the soldering iron immediately when not soldering. The oxides and carbides derived from the residual flux on the soldering iron tip will damage the soldering iron tip and reduce its thermal conductivity. Therefore, the tip of the soldering iron should be cleaned frequently with a temperature-resistant wet sponge to prevent damage to the tip of the soldering iron. After each use, the tip of the soldering iron should be wiped clean and dipped in a layer of tin to protect the tip of the soldering iron.
