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What Is Flux? Function, Classification and Value in SMT Soldering
Flux is an essential auxiliary material in SMT production. It is usually used with solder paste and directly affects solder joint formation, wettability and soldering reliability. It plays an important role in reducing dry joints, non-solder and oxidation defects.

Main Functions of Flux

  1. Remove Oxidation

    Clean the oxide layer on PCB pads and component pins to ensure good solder wetting.

  2. Anti-oxidation Protection

    Form a protective film at high temperature to prevent re-oxidation during reflow.

  3. Improve Wettability

    Reduce surface tension of molten solder, make solder flow evenly and form full and bright solder joints.

  4. Uniform Heat Dissipation

    Relieve thermal shock, avoid component cracking caused by local overheating, and stabilize soldering temperature.

Common Types of Flux

  1. Rosin-based Flux

    Moderate activity, good insulation and low corrosion, widely used in consumer electronics and industrial control products.

  2. No-clean Flux

    Little residue after soldering, no need for manual cleaning. It is the mainstream choice for mass SMT production.

  3. Water-soluble Flux

    High activity and excellent soldering performance. Residues must be cleaned with water, mostly used for medical, aerospace and high-reliability products.

The type, activity and proportion of flux will directly affect voids, dry joints, wettability and dull solder joints. Professional SMT manufacturers will select matched flux according to product grade and solder paste model.
Globalwell strictly matches solder paste and flux types for different products, effectively improving solder joint quality and production first-pass yield.


 

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