Online pcb manufacturing welding requirements for production process materials

1.Flux quality control

Flux is very important in the control of welding quality of online pcb manufacturing. Its roles are:

1) Remove oxides from the soldered surface.

2) Prevent solder and solder surface re-oxidation during soldering.

3) Reduce the surface tension of the solder.

4) Helps heat transfer to the weld zone.

At present, most of the wave soldering used is no-clean flux. The following requirements are required when selecting flux:

1) The melting point is lower than that of solder.

2) The immersion spreads faster than the molten solder.

3) Viscosity and specific gravity are smaller than solder.

4) Stable at room temperature.

2. Quality control of online pcb manufacturing solder

The tin-lead solder is continuously oxidized at a high temperature (250 ° C), so that the tin content of the tin-lead solder in the tin pot is continuously decreased, resulting in poor fluidity, quality problems such as tin connection, cold welding and insufficient solder joint strength. There are several ways to solve this problem:

1) Adding a redox agent to reduce SnO to Sn and reducing the generation of tin slag

2) Continuously remove dross.

3) Add a certain amount of tin before each soldering.

4) Using phosphorus-containing antioxidant solder

5) Nitrogen protection is used to allow the nitrogen to separate the solder from the air, replacing the ordinary gas, thus avoiding the generation of scum. This method requires modification of the equipment and supply of nitrogen. The best method at present is the use of phosphorus-containing solder in a nitrogen-protected atmosphere minimizes the scum rate