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What Role Does Flux Density Play in Wave Soldering For Electronic Component Assembly?

Flux Density Play in Wave Soldering For Electronic Component Assembly

The most important role that flux plays in wave soldering for electronic component assembly is to facilitate the formation of a solder joint. A successful soldering connection requires the solder to “wet” the surface of the parts to which it will be joined, and to adhere to it. If there are impurities on the metal surfaces, such as dirt or oil, they will re-oxidize at the elevated temperatures of the soldering process, and prevent the surface from properly wetting the solder. Flux removes these impurities and enables the wetting of the solder.

Typical soldering flux compositions include the main ingredient rosin, which is a natural resin extracted from pine trees. It is combined with a solvent, typically alcohol, and acid activators to produce a liquid that is suitable for use in the soldering process. There are many different types of rosin flux, with differing levels of activity, allowing them to be used for a variety of applications.

In addition to being used for soldering, rosin fluxes have also been shown to be effective in preventing corrosion and in eliminating residues left by previous soldering processes. They can be produced in various formats, such as a liquid flux, a tacky flux or as an additive to solder paste. Each format has its own advantages and is best suited for specific applications.

What Role Does Flux Density Play in Wave Soldering For Electronic Component Assembly?

Soldering without flux is difficult to do well, and can be hazardous to the health of the operator. Attempts to solder directly without flux usually result in the iron failing to heat the parts above their liquidus temperature, resulting in a cold solder joint that is not likely to hold up to electrical or mechanical stress. Flux allows the soldering iron to heat the parts above their oxidation level and wet them thoroughly, guaranteeing that they will be joined to a strong and reliable joint.

While it is possible to perform hand soldering, it is usually not practical for production-scale electronics. For large production runs of printed circuit boards, the manufacturing process is often automated, including the application of a spray flux, preheating, wave soldering, cooling and other processes. This allows the production team to focus on other tasks while ensuring that the quality of the soldering meets high standards.

As the PCB passes through the wave soldering zone, it is inspected by infrared sensors and then by spray nozzles that uniformly apply a thin layer of flux to all exposed areas of the board. The preheating of the flux promotes its activity, allowing it to quickly dry and prevent the formation of solder balls on the surface of the soldered components. Once the PCB has passed through the wave soldering zone, it enters a cooling area, which prevents thermal shock and minimizes defects that can occur during rapid temperature changes. This is essential for maintaining the integrity of the assembly. This cooling process also helps to ensure that the solder joints fully solidify, preventing shifts in position that could damage or degrade the components and/or solder connections.


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