First, the correct PCB repair should pay attention to the following points:

1. Correctly select materials such as solder paste, flux, welding wire, etc., and use lead-free solder wire containing lead-free special flux;
2. Select appropriate PCB rework equipment and tools;
3. Proper use of PCB rework equipment and tools;
4. Set the welding parameters correctly.

The temperature of the soldering iron used in manual repair welding should be improved, but avoid excessive temperature, and pay attention to the mastering of welding time to prevent the components from failing due to excessive welding temperature and long welding time. Lead-free solder has a high melting point and poor fluidity, so lead-free PCB rework requires training of the soldering iron operator and strictly follows the manual soldering process described above.

Second, the PCB repair process should pay attention to:

1. The operator should also be able to identify the lead-free soldering iron and its workstation, isolate the lead-free and lead-free operating areas, wear an anti-static wrist strap, and use an anti-static thermostatic soldering iron.
2. The shape of the soldering iron tip should be changed according to the shape of the component pins, such as flat shovel type, horseshoe type, double flat shovel type and square shape.
3, the soldering iron head should be kept smooth, no hooks, no thorns, no heavy touch pads, not a long time heating at a point, not to scratch the pads and wires.
4. It is not allowed to directly heat the soldering end of the Chip component and the upper part of the pin root with a soldering iron.
5, do not apply excessive pressure during the welding process to compensate for the lack of wetting, otherwise it will cause deformation of the tip, should use the contact method; timely clean the black surface oxide or rust stains of the iron tip, otherwise it is not easy to tin.
6. When cleaning, use a sponge that is wetted and then squeezed to clean the tip. If it is cleaned with an unwetted sponge, the tinned layer on the surface of the tip will peel off and lead to no tin.
7. PCB lead-free product rework should ensure that the flux and solder are consistent or matched with the solder, especially to prevent solder contamination. The main rework material for lead-free products is SnAg alloy, which can be processed into a wire, which does not cause intermetallic compound problems, and effectively prevents the slag-like particles caused by intermetallic compounds.