Difference between flux and solder paste

Fluxes and flux pastes both play an important role in the soldering process, but there are some distinct differences in their composition, use, form, and application      scenarios.

Here are the main differences between them:

1, composition:

① flux is usually a variety of chemical substances composed of liquid-like compositions, the main component is volatile organic solvents and a small amount of rosin, active agents.

② flux paste is composed of a variety of chemical compositions of paste combinations, the main components are made of organic solvents, resins, organic acids, thixotropic agents, surfactants and other chemicals. In addition to removing the oxidised layer on the metal surface, it also provides adhesion, anti-oxidation and other functions. The composition of flux paste varies according to the use, such as conventional flux paste may contain organic solvents, rosin, halogen salts, organic acids, thixotropic agents, etc., while the lead-free flux paste may contain organic solvents, rosin resins, organic acids, antioxidants, surfactants and so on.

2, use:

① Flux is mainly suitable for soldering scenarios at high temperatures, such as electronic high temperature spot soldering, plate gold soldering and so on. It is added to the solder to improve the welding performance, such as reducing the welding temperature, extend the welding time. As well as in wave soldering to remove the oxide film on the metal surface.

② Flux paste, on the other hand, is suitable for a variety of soldering scenarios due to its good forming ability and deoxidation and anti-oxidation effects, most of which are matched with solder powder prepared into solder paste for use together in SMT as well as semiconductor packaging. It not only removes the oxides on the metal surface, but also provides moulding, adhesion and deoxidation and anti-oxidation functions to enhance the reliability of soldering.

3, form:

① flux is usually in liquid form, need to be stirred well when used, and then coated, sprayed, dipped and stuck in the welding parts.

② flux paste is similar to paste paste, can be more convenient to apply, printing in the welding parts, more convenient to use.

4, application scenarios:

① flux in the SMT soldering process is an indispensable auxiliary material, especially in the wave soldering, flux and solder are used separately. In reflow soldering, flux is used as an important part of solder paste.

② Because of its diverse components and wide range of uses, flux paste is widely used in the fields of watch and clock instruments, precision parts, medical devices, stainless steel handicrafts, tableware, mobile communications, digital products, air conditioning and refrigerator refrigeration equipment, eyeglasses, cutlery, automobile radiators, and all kinds of PCB boards and the brazing of BGA solder balls, and so on.

In summary, there are obvious differences between flux and flux paste in terms of composition, use, form and application scenarios. When choosing which auxiliary material to use, you need to consider according to the specific soldering needs and scenarios.

Here I would like to recommend Fitech, Fitech's flux and flux paste products have high competitiveness in the microelectronics soldering materials market by virtue of their excellent performance, good wettability and stability, wide range of applications and professional customised services. Whether it is microelectronic packaging, automotive electronics or other fields, Fitech can provide suitable solder material solutions. If you have any questions or needs you are welcome to contact us at any time, we look forward to communicating with you.