Introduction to the principle of electric soldering iron
False soldering means that only a small amount of tin is welded at the solder joint, resulting in poor contact and intermittent on and off. False welding means that it seems to be welded on the surface, but it is not actually welded. Sometimes the lead wire can be pulled out from the solder joint by pulling it out by hand. These two situations will bring great difficulties to the debugging and maintenance of electronic production. Both of these conditions can only be avoided with extensive, careful welding practice. When soldering the circuit board, be sure to control the time well. If it is too long, the circuit board will be burnt, or the copper foil will fall off. When removing components from the circuit board, stick the tip of the electric soldering iron on the solder joint, and pull out the component after the tin on the solder joint melts. The temperature of the soldering iron has a certain relationship with the volume, shape and length of the soldering iron tip. When the volume of the soldering iron tip is relatively large, the retention time is longer. In addition, in order to meet the requirements of different soldering materials, the shape of the soldering iron tip is different, and the common ones are cone, chisel, circular bevel and so on.
Use the ohm range of the multimeter to measure whether there is an open circuit or short circuit at both ends of the plug, and then use the Rx1000 or Rx10000 range to measure the resistance between the plug and the shell. If the pointer does not move or the resistance is greater than 2-3MΩ, it can be used safely without leakage. The soldering iron core of the internal heating type electric soldering iron is made of a relatively thin nickel-chromium resistance wire wound on a porcelain tube. Its resistance is about 2.5kΩ (20W), and the temperature of the soldering iron can generally reach about 350OC. Because the internal heating type electric soldering iron has the characteristics of fast heating, light weight, low power consumption, small size and high thermal efficiency, it has been widely used. After the soldering iron is connected to the power supply, if it is not hot or not too hot, check whether the power supply voltage is lower than AC210V (the normal voltage should be AC220V). If the voltage is too low, it may cause insufficient heat and difficulty in soldering. The soldering iron tip is oxidized or the fastening part between the root end of the soldering iron tip and the inner wall of the outer tube is oxidized. The reason for the electrification of the neutral line is that in the three-phase four-wire power supply system, the neutral line is grounded and has the same potential as the earth. If the neon bulb glows when tested with a test pen, it indicates that the zero line is charged (there is a potential difference between the zero line and the earth). The open circuit of the neutral line, the increase of the grounding resistance of the neutral line or the open circuit of the grounding downconductor and the grounding of the phase line will all cause the neutral line to be charged.
