As PCB factory china knows that, the HASL process involves the use of special heat flux. Also, this flux plays a crucial role in activating the exposed copper surface of the board. However, heat flux must have the following characteristics to perform well:

Non-toxic and water-soluble

Water-soluble flux has less board residue and is easy to clean. Also, this flux won’t form any ion pollution in the printed circuit board. This flux can meet environmental standards without any special treatment.

Thermal stability

With good thermal stability, the PCB won’t have green oil.

Good activity

Copper surface layer removal facilitates solder wettability on the copper surfaces. Also, it is important to consider the good activity and the minimum corrosion of copper. Also, you need to minimize the solubility of copper in the solder.

Certain viscosity

The flux needs a certain level of viscosity. Also, the flux needs certain viscosity in order to protect the laminate surface.