Flux, is used to remove oxide film on the metal surface, increase wetting, accelerate the soldering process, and improve soldering quality.
1. The type of flux.
According to the different characteristics of the flux, the flux is divided into three categories: inorganic flux, organic flux and resin flux.
1) Inorganic flux.
The main component is zinc oxide, ammonia chloride or a mixture thereof. It has strong activity and good welding performance, but has a large corrosive effect, so it is often used for welding of metal products that can be cleaned, and is generally not used in the assembly of electronic products.
2) Organic flux.
The main component is an organic acid halide, which has good fluxing performance and low corrosivity, but has poor thermal stability .
3) Resin flux.
The main ingredient is rosin, or pine perfume prepared by dissolving pine with alcohol. It has little corrosiveness and high insulation resistance at room temperature. It is the most widely used flux in electronic product welding.
2.The role of flux
Helps remove oxides and various contaminants from metal surfaces to keep the welding work surface clean.
Improves heat transfer during soldering, causing heat to diffuse from the heat source to the pad. There is always a gap between the soldering iron tip and the contact surface between the soldered metal and the pad. The air between them has a heat insulating effect, which hinders the heat transfer, and the flux is added because the melting point of the solder is much lower than that of the solder. Therefore, it is first melted into a liquid state and filled with voids, which improves the preheating speed of the welding.