Jan. 09, 2024
1. Before welding, the solder should be coated on the pad and treated with a soldering iron to avoid poor tinning or oxidation of the pad and poor welding. Chips generally do not require processing.
2.Use tweezers to carefully place the PQFP chip on the PCB board so as not to damage the pins. Align it with the pad and make sure the chip is placed in the right direction. Turn the temperature of the iron to more than 300 degrees Celsius, dip a small amount of solder on the tip of the iron, press down the aligned chip with a tool, and add a small amount of solder on the two diagonal pins. Hold the chip down and weld the pins on the two diagonal positions to hold the chip in place. After welding the diagonal, recheck the alignment of the chip position. If necessary, adjust or remove and readjust the position on the PCB board.
3. When starting to weld all the pins, add solder to the tip of the soldering iron and apply flux to all the pins to keep them moist. Touch the end of each pin of the chip with the tip of the soldering iron until you see solder flowing into the pin. When welding, the tip of the soldering iron should be parallel to the welding pin to prevent overlap due to excessive welding.
4. After soldering all pins, wet all pins with flux to clean the solder. Blot out excess solder to eliminate any short circuits and overlaps. Finally, check for faulty welding with tweezers. After the inspection is complete, remove the solder from the board, soak the stiff brush with alcohol, and wipe it carefully along the direction of the pins until the solder is gone.
5.SMD resistance-capacitance components are relatively easy to weld. You can put it on the solder joint first, and then put one end of the component on it, hold the component with tweezers, and see if the placement is correct after the end is welded. If it is already aligned, then weld the other end.
The main sequence of FPC welding is: FPC paste alignment - tin feed drag welding - appearance inspection - electrical detection. FPC paste alignment: Before pasting alignment, check whether the FPC pad and the corresponding solder surface are smooth and oxidized. Note that after pasting, the pad must be exposed to about 1.00mm of molding, which is convenient for tin.
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