Soldering iron - SMD component welding method
1 Before soldering, apply flux on the pad, and treat it with a soldering iron to avoid poor tinning or oxidation of the pad, resulting in poor soldering, and the chip generally does not need to be processed.
2 Use tweezers to carefully place the QFP chip on the PCB, be careful not to damage the pins to align them with the pads, and ensure that the chip is placed in the correct direction. Adjust the temperature of the soldering iron to more than 300 degrees Celsius, dip the tip of the soldering iron with a small amount of solder, press down on the aligned chip with a tool, add a small amount of solder to the pins at the two diagonal positions, and still Hold down the chip and solder the pins on the two diagonal positions so that the chip is fixed and cannot be moved. After soldering the opposite corners, check again whether the position of the chip is aligned. Adjust or remove and re-align on PCB if necessary.
3 When starting to solder all the pins, solder should be added to the tip of the soldering iron, and all the pins should be coated with solder to keep the pins wet. Touch the tip of the soldering iron to the end of each pin on the chip until you can see solder flow into the pin. When soldering, keep the tip of the soldering iron parallel to the pin to be soldered to prevent lapping due to excessive solder.
4 After all the pins are soldered, wet all the pins with flux to clean the solder and blot off excess solder where needed to eliminate any possible shorts and laps. Finally, use tweezers to check whether there is any false soldering. After the inspection is completed, remove the flux from the circuit board, soak the hard brush in alcohol and wipe carefully along the direction of the pin until the flux disappears.
5 SMD resistance-capacitance components are relatively easy to solder. You can put tin on a solder point first, then put one end of the component, and use tweezers to clamp the component. After soldering one end, check whether it is placed correctly; if Already placed, and then solder on the other end. If the pins are very thin, you can add tin to the pins of the chip in the second step, then clamp the core with tweezers, lightly tap on the edge of the table, and remove the excess solder. In the third step, soldering iron does not need tinning, and soldering directly . When we finish the welding work of a circuit board, we must check the quality of the solder joints on the circuit board, repair, and repair welding. Solder joints meeting the following criteria are considered to be
Qualified solder joints:
①Solder joints form an inner arc (conical shape)
② The overall solder joints should be complete, smooth, free of pinholes and rosin stains.
③If there are leads and pins, the length of their exposed pins should be between 1-1.2MM.
