Soldering Iron - Use a Heat Gun to Desolder Flat Pack ICs
1. Check the direction of the IC before removing the components, and do not put them upside down when reinstalling.
2. Observe whether there are heat-resistant components (such as liquid crystals, plastic components, BGA ICs with sealants, etc.) next to and on the back of the IC. If so, cover them with a shielding cover or the like.
3. Add appropriate rosin to the IC pins to be removed to smooth the PCB pad after removing the components. Otherwise, burrs will appear and it will be difficult to align when re-soldering.
4. Preheat the adjusted hot air gun evenly in an area of about 20 square centimeters around the component (the air nozzle is about 1CM away from the PCB board, and moves quickly in the preheating position. The temperature on the PCB board does not exceed 130-160°C. )
1) Remove moisture on the PCB to avoid "bubbles" during rework.
2) Avoid stress warping and deformation between PCB pads caused by excessive temperature difference between the upper and lower sides due to rapid heating of one side (top) of the PCB board.
3) Reduce the thermal shock of the parts in the welding area due to heating above the PCB board.
4) Prevent the adjacent IC from desoldering and warping due to uneven heating.
5) Heating the circuit board and components: Set the hot air gun nozzle about 1CM away from the IC, move it slowly and evenly along the edge of the IC, and use tweezers to gently clamp the diagonal part of the IC.
6) If the solder joint has been heated to the melting point, the hand holding the tweezers will feel it immediately. Be sure to wait until all the solder on the IC pin is melted before carefully lifting the component vertically from the board using "zero force" Pick it up, this can avoid damaging the PCB or IC, and also avoid short circuiting the solder left on the PCB board. Heating control is a key factor in rework, and the solder must be completely melted to avoid damaging the pads when the component is removed. At the same time, it is necessary to prevent the board from being overheated and the board should not be distorted due to heating. (For example: If possible, you can choose 140℃-160℃ for preheating and low-temperature heating. The entire process of disassembling the IC should not exceed 250 seconds)
7) After removing the IC, observe whether the solder joints on the PCB board are short-circuited. If there is a short-circuit, you can use a hot air gun to reheat it. After the solder at the short-circuit melts, use tweezers to gently scratch along the short-circuit, and the solder will melt naturally. separate. Try not to use a soldering iron, because the soldering iron will take away the solder on the PCB board. If there is less solder on the PCB board, it will increase the possibility of false soldering. It is not easy to fill the solder pads with small pins.
