What is The Flux in SMT Patch

In the electronic processing factory, there are many things worth noting in the welding process. For example, the welded metal surface and the pad surface need to be carefully cleaned, otherwise the welding effect of the SMT patch may be affected. Flux: A chemical that aids and facilitates the soldering process in the soldering process while providing protection and preventing oxidation reactions. Flux can be divided into solid, liquid and gas. There is mainly auxiliary heat conduction, removing oxides, reducing the surface tension of the welded material, “removing the oil on the surface of the welded material, increasing the welding area, preventing re-oxidation, etc. There are two key roles in these aspects. That is, to remove oxides and reduce the surface tension of the material to be soldered. There are auxiliary raw materials between the chip components and the solder paste, that is, the flux.

A. Features

1. It should have good thermal stability, and the general thermal stability temperature is not less than 100 ℃.

2. The flux should be fully effective just before the welding material melts.

B. Function

1. Promote heat transfer to the welding area.

2. Remove the oxide on the surface of the welded metal.

3. Prevent high temperature reoxidation of the metal surface during welding.

4. Maintain the continuity of the surface layer of the SMT chip processing and welding raw materials, improve the heat resistance of the welding material, improve the wettability, and improve the solderability.

C. Composition

1. Additives Additives mainly include corrosion inhibitors, surfactants, thixotropic agents and matting agents.

2. Rosin is generally used as a pure natural flux in the rosin SMT foundry material, and it is the most suitable raw material for flux recognized at this stage.

3. Solvents Solvents are mainly ethanol, isopropanol, etc. The function is to dissolve the liquid or liquid components in the organic solvent, and adjust the relative density, viscosity, fluidity, heat resistance and maintenance effect.

4. Activator Activator is also a strong reducing agent, and its main function is to purify the surface of the solder and the welded part. The content is 1%–5%. Commonly used are organic chemical amines and ammonia compounds, citric acid and salts and organic chemical halides.

5. Film formers The most commonly used demulsifiers in SMT chip processing are classified into two categories according to their ingredients. The category is natural resins, and the other category is resin materials and some organic compounds. The key of demulsifiers is to maintain spot welding. and base steel plate to provide corrosion resistance and dielectric strength.