SMT chip components welding should choose 200 ~ 280℃ temperature control tip soldering iron. Most of the substrates of chip resistors and capacitors are made of ceramic materials, which are easily cracked by collisions, so the skills of temperature control, preheating and light touch should be mastered when welding. Temperature control means that the welding temperature should be controlled at about 200 ~ 250℃. Preheating refers to preheating the components to be welded in an environment of about 100 ° C for 1 to 2 minutes to prevent the components from being suddenly damaged by thermal expansion. Light touch means that the soldering iron head should first heat the solder joint or guide band of the printed board during operation, and try not to touch the component. In addition, each welding time should be controlled at about 3 seconds, and the circuit board should be cooled naturally at room temperature after welding. The above methods and techniques are also applicable to the welding of chip type transistor II and triode. The number of pins of the chip integrated circuit is large, the spacing is narrow, and the hardness is small. If the welding temperature is improper, it is easy to cause short circuit of the pin solder, false welding or the copper foil of the printed line is removed from the printed board. When disassembling the chip integrated circuit, the temperature of the adjustable soldering iron can be adjusted to about 260℃. After removing all the soldering tin of the IC pin with the soldering iron head and the tin absorber, gently insert the IC pin with the needle tweezers at the bottom of the IC. While heating with the soldering iron, gently lift the IC pin one by one with the tweezers, so that the IC pin is gradually detached from the printed board. When lifting the integrated circuit with tweezers, it must be synchronized with the part of the soldering iron to prevent the circuit board from being damaged too quickly. Before replacing the new integrated circuit, all the solder left by the original integrated circuit should be removed to ensure the smooth and clean pad. Then, polish and clean the pin of the integrated circuit to be welded with fine sandpaper, evenly tin, and align the pin of the integrated circuit to the corresponding solder spot of the printed board. During welding, gently press on the surface of the integrated circuit with your hand to prevent the integrated circuit from moving. With the other hand, dip the electric soldering iron into appropriate amount of solder, weld the pin of the four corners of the integrated circuit with the circuit board, and then check and confirm the type and direction of the integrated circuit again. After the soldering is correct, the soldering iron temperature is adjusted to about 250℃. One hand holds the soldering iron to heat the IC pin, and the other hand sends the soldering wire to the heating pin for welding until all the pins are heated and welded. Finally, carefully check and eliminate the short circuit and virtual welding of the pin. Prevent residual welding slag. Before troubleshooting the module circuit board, it is advisable to clean the printed board with a brush dipped in anaqueous alcohol, remove dust, welding slag and other debris on the board, and observe whether the original circuit board has virtual welding or welding slag short circuit, and find the fault early to save maintenance time.