I. Disassembly and Assembly of SMD Capacitor and Precautions
(1) When trimming with an electric iron, if you need to remove the welded capacitor first, please completely melt the solder before removing it to avoid the pressure on the capacitor terminal;
(2) When disassembling, please do not contact the welding head of the soldering iron with the main body of the capacitor;
(3) When disassembling the capacitor, firstly, carry out multi-point welding on the two pins of the capacitor (at present, the substrate adopts large-scale welding technology, and welding is very rare, and the components of the substrate mostly adopt double-sided welding technology, which makes welding difficult to melt. So you can add some solder first, then use the soldering iron), let the solder connect the two pins, and then hold the soldering iron with one hand and the capacitor with the other hand; When the soldering iron melts the solder part, immediately shake the capacitor gently and slowly pull up one pin of the capacitor; Then slowly pull out the other pin of the capacitor; If the two pins can't be pulled out at one time, you can touch the two pins in turn with an electric soldering iron and shake the capacitor by hand. When the two pins of the capacitor are completely loose, the capacitor can be removed;
(4) After removing the damaged capacitor (especially the capacitor of Explosicum), clean the solder in the pin socket of the damaged capacitor and insert a new capacitor. The method is to put the back of the substrate upward and insert the needle into the original capacitor jack position. Touch the lower part of the needle with an electric soldering iron. After the needle is heated, insert it into the needle and shake it from side to side. After the needle passes through the original capacitor jack, move the electric soldering iron slowly, so that the diameter of the jack is exposed. Please note that your fingers must hold the plastic part on the upper part of the needle, not the metal part of the needle;
II. Disassembly and Assembly of SMD Capacitors and Precautions
(1) before removing the capacitor in the circuit, please discharge it first (the bulb can discharge, but can't discharge by short circuit directly). After the capacitor is discharged, voltage (lightning voltage) may still be generated between the terminals. At this time, please discharge with 1kω resistor.
(2) The leakage current of capacitors stored for more than half a year may increase. At this time, please use 1kω resistor for voltage processing.
(3) Do not deform the capacitor body during installation;
(4) Before welding, confirm the rating (electrostatic capacity and voltage) and polarity of the capacitor.
(5) When installing and welding capacitors, make the signs easy to observe.
(6) When welding capacitors with soldering iron, please pay attention to welding conditions (preheating, welding temperature and time, terminal immersion time, etc.).
(7) When welding, do not immerse the capacitor body in the welding material. Insert the printed circuit board and solder only the opposite back side of the capacitor. Except for terminals, solder cannot be attached.
(8) When welding, keep a proper distance between the soldering iron and the capacitor plastic pipe, and the welding action is fast, so as to prevent the overheated plastic pipe from cracking and prevent the electrolyte from leaking.
(9) After the capacitor is welded to the printed circuit board, the main body of the capacitor shall not be tilted, inverted or twisted, and the printed circuit board shall not be moved with the capacitor as the handle.
(10) When installing a new capacitor, cut short and straighten the pins of the new capacitor, and first weld one pin. Weld the upper end of the back of the capacitor on the circuit board at multiple points, and press the pins of the capacitor on the welding holes. After the welding on the back side melts into the welding pin hole, the pressed pin can enter. The other pin enters the soldering hole in the same way. After installing the capacitor, cut off the excessive pins and press the capacitor with one hand to make it closely contact with the circuit. Holding the soldering iron in the other hand, while re-soldering the two pins of the capacitor, gently shake the two pins of the capacitor, so that the solder can fully penetrate into the double panels of the pins.
Third, patch capacitance substitution
(1) For damaged or leaked capacitors, the original capacitors are generally removed first, and then new capacitors are welded;
(2) For capacitors with open circuit fault or insufficient capacity, the new capacitor can be directly welded on the solder joint on the back of the capacitor without disassembling the original capacitor;
(3) After the capacitor is damaged, in principle, the capacitor with the same type, same main parameters and similar shape and size should be used for replacement. However, if no type of capacitor can be found, other types of capacitors can be used instead. Capacitors with high withstand voltage can replace capacitors with the same capacity but low withstand voltage. The replacement capacitor shall not be lower than the original capacitor in terms of withstand voltage and temperature coefficient;
(4) Under normal circumstances, a fixed capacitor with a capacity less than 1pF is nonpolar, and its two pins can not be positive or negative. For a capacitor with polarity, it is necessary to pay attention to polarity;
(5) When installing the capacitor, please visually check the size of the replaced capacitor and confirm that it will not affect other surrounding components after installation;
