I. PCB welding special tools and raw materialsThe soldering tool must have a 25W copper tip small soldering iron, a gold bridge electrode, and a standard soldering station with adjustable temperature and ESD maintenance. Note that the tip of the soldering iron should be thin, and the total width of the top should not exceed mm. A pair of pointed medical tweezers can be used to move and fix the immobile chip and its inspection power circuit. It is also necessary to prepare fine electrodes, flux, isopropyl alcohol, etc. in advance. The purpose of applying flux is mainly to improve the flowability of the solder, so that the solder can be pulled with a soldering iron, and the surface tension can be smoothly encapsulated on the pin and the solder layer. After soldering, use ethanol to eliminate the flux on the board.
II. PCB board welding process1. The circuit board welding technical engineer reminds the readers to apply flux on the solder layer before soldering, and solve it with a soldering iron to prevent the solder layer from being poorly plated or oxidized, resulting in poor soldering, and the chip is generally not Need to be resolved.
2. Use medical tweezers to carefully place the PQFP chip on the PCB, taking care not to damage the pins. Align it with the two ends of the solder layer, make sure that the chip placement is correct. 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, use a special tool to press down the chip at the pointed part, and add a small amount of solder to the pins at the two top corners. Still pressing the chip down, solder the pins on the two top corners so that the chip is fixed and cannot be moved. After soldering the top corner, check again whether the chip is pointing. If necessary, it can be adjusted or disassembled and pointed at the PCB board again.
3. When you start to solder all the pins, you should add solder to the tip of the soldering iron, and apply flux to all the pins to keep the pins wet. Touch the tip of each pin of the chip with the tip of a soldering iron until you see solder injected into the pin. During soldering, the tip of the soldering iron and the pins to be soldered must be processed in parallel to avoid overlapping of reinforcing steel due to excessive soldering.4. After soldering all the pins, wetting all the pins with flux is convenient for cleaning the solder. Remove unnecessary solder in necessary areas to eliminate all short-circuit faults and reinforcement overlap. Finally, use medical tweezers to check whether there is a virtual connection. After the inspection, remove the flux from the circuit board, dip the hard brush with ethanol and scrub carefully along the pin position until the flux subsides.
5. The circuit board welding technical engineer reminds you that the SMD components are relatively easy to solder. You can solder tin on a spot weld first, then put the end of the component, and use medical tweezers to hold the component. After soldering one end, check to see if it has been adjusted; if it has been adjusted, then solder the other end. To truly grasp the welding skills must be a lot of practical activities.