An introduction to the difference between the power ratings of electric soldering irons
In the process of electrical repair, an electric soldering iron is an essential tool, but many maintenance personnel who have just come into contact with the soldering iron do not know the standard to choose the power of the soldering iron during the welding process. Often, a soldering iron will go global. The most direct consequence is that the welding effect is not ideal due to not paying attention to the power of the selected soldering iron.
The power of the electric soldering iron used is too high, which can easily burn out the components (usually when the junction temperature of the transistor and transistor exceeds 200 ℃, it will burn out) and cause the printed wires to fall off the substrate; The power of the soldering iron used is too low, the solder cannot be fully melted, the flux cannot evaporate, the solder joints are not smooth and firm, and are prone to false soldering. Generally, it is used for soldering integrated circuits, printed circuit boards, CMOS circuits, decorating transistors, IC type recorders, televisions, and conducting ordinary circuit experiments. It is generally recommended to use 20W. For repairing vacuum tube machines, such as biliary machines and old instruments, it is recommended to use 35W, while for externally heated ones, it is recommended to use 45W. For welding the wiring of large transformers and grounding main lines on metal substrates, internal heated 50W and external heated 75W are used. When welding metal materials, an externally heated electric soldering iron with a capacity of over 100W should be selected. If conditions permit, amateur radio enthusiasts can equip themselves with a 20W internally heated, a 35W internally or externally heated, and a 150W externally heated soldering iron, which can basically meet various welding needs.
The solder we use is generally divided into two types: lead solder and lead-free solder, but the most commonly used is lead solder, which consists of 63% tin, 37% lead, and a melting point of 183 ℃. On the other hand, lead-free solder has a composition of 99% tin, about 1% flux, and a melting point of 227 ℃. The advantages of lead solder are low melting point, easy soldering, low price, but it is not environmentally friendly. Lead is harmful to the human body, so after welding, it is necessary to wash your hands carefully. During the welding process, it is best to wear a mask or a bright place to ensure a certain distance between the head and the welded part. With the increasing awareness of environmental protection among people, lead-free soldering is now used for machine welding in factories. Due to the high melting point of lead-free solder, it is not difficult to understand why it is sometimes difficult to melt when repairing imported electrical appliances.
An electric soldering iron is an electric heating device that can generate a high temperature of about 250 ℃ when energized. During the welding process, an electric soldering iron is actually a process of heat conduction. When it comes into contact with the welding surface, the heat from the soldering iron head is transferred to the solder, which absorbs the heat and melts, forming a bright and smooth solder joint under surface tension. In the process of welding heat conduction, due to the fact that metals are good conductors of heat, heat transfer is faster. During the melting process of solder, due to the heat loss of the soldering iron head, its temperature decreases to some extent. If the solder joint area is large, it needs to absorb more heat to make the solder on top reach the melting point. If the volume of the soldering iron head is small, it stores less heat, and the temperature drops quickly. Due to the small power of the soldering iron core, the heat generated is not enough to replenish the lost heat. At this time, the most intuitive phenomenon is that the solder does not melt or does not melt completely. In this situation, we need to choose high-power soldering iron for welding. On the contrary, if the welded part is small, we do not need to use high-power soldering iron; If using a high-power soldering iron, it is important to pay attention to the soldering time, otherwise excessive heat can easily cause damage to the circuit board and circuit board, resulting in the detachment of printed copper foil. There is no specific quantitative requirement for the specific power of the soldering iron, and the accumulation of long-term work experience by maintenance personnel is the best way to choose a soldering iron that is suitable for oneself.
