Generally, the pins of the circuit board should be as short as possible (about 1mm) after welding, so as to avoid mutual discipline affecting the welding. Secondly, if the pin is held for too long, a large local capacitance will be generated between the two pins, which will have a great influence on the high-frequency circuit.

The main skills of circuit board welding are as follows:

A. After soldering all pins, soak all pins with flux to clean the solder. Absorb excess solder when necessary to eliminate any short circuit and lap joint. Finally, use tweezers to check whether there is virtual welding. After the inspection, remove the flux from the circuit board, soak the hard brush in alcohol, and carefully wipe it along the pin direction until the flux disappears.

B, the circuit board welding engineer reminds you that patch resistance-capacitance components are relatively easy to weld. You can solder a solder joint first, then put one end of the component, clamp the component with tweezers, and see if it is put right after welding one end; If it is already in place, weld the other end. It takes a lot of practice to really master welding skills.

C, the circuit board welding engineer reminds readers that before welding, the solder pad should be coated with flux and treated with soldering iron to avoid poor soldering due to poor tin plating or oxidation of the solder pad, and the chip generally does not need to be treated.

D carefully place the PQFP chip on the PCB with tweezers, and be careful not to damage the pins. Align it with the pad and make sure that the chip is placed in the correct direction. Adjust the temperature of the soldering iron to above 300 degrees Celsius, dip the tip of the soldering head with a small amount of solder, press the chip at the aligned position with a tool, add a small amount of flux to the pins at two diagonal positions, still press the chip, and weld the pins at two diagonal positions to make the chip fixed. After the diagonal is soldered, check the alignment of the chip again. If necessary, it can be adjusted or removed and realigned on the PCB. E. When soldering all pins, solder should be added to the tip of soldering iron, and all pins should be coated with flux to keep wet. Touch the tip of the soldering iron to the end of each pin of the chip until the solder flows into the pin. When welding, the welding head should be parallel to the capillary to avoid overlapping due to excessive solder.