Afterthe PCBA inspection is completed, the defective PCBA needs to be repaired. Thecompany has two methods for repairing the SMT PCBA. One is to use a constanttemperature soldering iron (manual welding) for repair, and the other is to usea repair workbench (hot air welding) for repair. No matter which method isadopted, 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 solderingpoint in less than 5 seconds, preferably about 3 seconds.
The soldering iron rework method is thetreatment of the new soldering iron before use: the new soldering iron can beused normally after the soldering iron tip is plated with a layer of solderbefore use. When the soldering iron is used for a period of time, there willLayer oxide layer, so that it is difficult to "eat tin". At thistime, 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 thehandle of the soldering iron in your palm. This method is suitable forhigh-power electric soldering irons to weld parts with large heat dissipation.
b. Ortho-grip: Hold the handle of thesoldering iron with four fingers except the thumb, and press the thumb alongthe direction of the soldering iron. The soldering iron used in this method isalso relatively large, and most of them are curved soldering iron tips.
c. Pen holding method: holding an electricsoldering iron like holding a pen, suitable for low-power electric solderingirons to weld small parts to be welded. The company uses the pen-holdingmethod.
Welding steps:
During the soldering process, the tools shouldbe placed neatly and the electric soldering iron should be held steady andaligned. For general joint welding, it is best to use tube-shaped solder wirewith rosin. Hold the soldering iron in one hand and the solder wire in theother.
Clean the soldering iron tip Heat the solderjoints Melt the solder Move the soldering iron tip Remove the soldering iron
One is to quickly touch the heated and tinnedsoldering iron tip to the cored wire, and then touch the solder joint area, usethe molten solder to help the initial heat conduction from the soldering ironto the workpiece, and then move the solder wire away to be in contact Solderingiron tip for soldering surface.
Oneis to touch the soldering iron tip to the pin/pad, and place the tin wirebetween the soldering iron tip and the pin to form a thermal bridge; thenquickly move the solder wire to the opposite side of the soldering area.
However, it is usually caused by impropertemperature, excessive pressure, extended retention time, or damage to PCB orcomponents caused by the three together.