After the PCBA inspection is completed, the defective PCBA needs to be repaired. The company has two methods for repairing the SMT PCBA. One is to use a constant temperature soldering iron (manual welding) for repair, and the other is to use a repair workbench (hot air welding) for repair. No matter which method is adopted, it is required to form a good solder joint in the shortest time. Therefore, when a soldering iron is used, it is required to complete the soldering point in less than 5 seconds, preferably about 3 seconds.
The soldering iron rework method is the treatment of the new soldering iron before use: the new soldering iron can be used normally after the soldering iron tip is plated with a layer of solder before use. When the soldering iron is used for a period of time, there will Layer oxide layer, so that it is difficult to "eat tin". At this time, you can file off the oxide layer and re-plated solder.
Holding method of electric soldering iron:
a. Reverse grip: Use five fingers to hold the handle of the soldering iron in your palm. This method is suitable for high-power electric soldering irons to weld parts with large heat dissipation.
b. Ortho-grip: Hold the handle of the soldering iron with four fingers except the thumb, and press the thumb along the direction of the soldering iron. The soldering iron used in this method is also relatively large, and most of them are curved soldering iron tips.
c. Pen holding method: holding an electric soldering iron like holding a pen, suitable for low-power electric soldering irons to weld small parts to be welded. The company uses the pen-holding method.
Welding steps:
During the soldering process, the tools should be placed neatly and the electric soldering iron should be held steady and aligned. For general joint welding, it is best to use tube-shaped solder wire with rosin. Hold the soldering iron in one hand and the solder wire in the other.
Clean the soldering iron tip Heat the solder joints Melt the solder Move the soldering iron tip Remove the soldering iron
One is to quickly touch the heated and tinned soldering iron tip to the cored wire, and then touch the solder joint area, use the molten solder to help the initial heat conduction from the soldering iron to the workpiece, and then move the solder wire away to be in contact Soldering iron tip for soldering surface.
One is to touch the soldering iron tip to the pin/pad, and place the tin wire between the soldering iron tip and the pin to form a thermal bridge; then quickly move the solder wire to the opposite side of the soldering area.
However, it is usually caused by improper temperature, excessive pressure, extended retention time, or damage to PCB or components caused by the three together.
