Types and Functions of Solder Paste Flux Carriers


Rosin Resin

As an extremely important part of solder paste products, flux affects important properties such as the performance and reliability of solder paste. The base material is one of the main components of the solder paste flux. What are the functions of the base material in the solder paste flux? What are the commonly used base materials of the flux? How does it work?


The base material for solder paste flux has the functions:

(1) Cooperate with the solvent in the flux to enhance solder paste tackiness, keeping the mechanical position of the component after mounting.

(2) The combined action of the base material, solvent, thixotropic agent, etc., ensures the good printing performance of the solder paste;

(3) The base material in flux is the carrier of the solder alloy powder, and it also has a certain soldering cleaning effect.

Epoxy resin

Common materials and mechanism of the flux carrier:

Natural rosin, modified rosin, artificial resin, and so on are often used as the flux carrier, which forms part of the activator system in the solder paste. Once the flux carrier melts, it spreads over the surface of the metals. In addition, the active substance dissolved in the molten flux flows along the metal surface. Meanwhile, the activator dissolved in the flux carrier will react with oxides on the surface of the alloy powder to prepare for reflow soldering. A chemical reaction begins when the reactants come into contact with each other, and the rate of reaction increases as the temperature increases.


The base material (solid content) in the flux accounts for about 20% to 30% of the mass, and rosin resin is often used. The chemical composition and properties of rosin resin vary by type, origin, and production process. Therefore, the selection of a good rosin resin is the key to ensuring the flux quality.

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