Soldering flux

July 22, 2024
Latest company news about Soldering flux

Understanding the Role of Flux When Soldering

Anyone who’s ever tried soldering components  with untinned pads without flux will ‎know the problems to go along with the process. The solder will hardly stick to the pads or the ‎components, and even if it does, the solder joints are often brittle and of bad quality. That’s often ‎due to a mix of factors. For example, the copper pads on the PCB start to oxidize as soon as ‎they’re exposed to air after the etching process. This thin oxidization layer builds up on the ‎surface, preventing the solder from sticking to the copper properly. 

This is where flux comes in, as this chemical product helps prepare the surfaces by ‎removing oxidization and wetting the surface. Further, flux helps create a true metallurgic bond ‎between the PCB’s pads and component legs, ensuring that solder joints won’t crack when ‎exposed to thermal and physical stress. Finally, flux also helps prevent new oxidization from ‎forming during the high heat soldering process which would normally accelerate oxidization.‎

The Three Main Types of Soldering Flux in Electronics

Like solder, you can distinguish the types of flux commonly available for use in electronics ‎assembly by the base chemical used to create the flux. The three main types are rosin-based, ‎no-clean, and water-soluble flux. Alternatively, it’s also possible to classify the flux according to ‎its delivered form, such as a spray, liquid, paste, or core embedded within the solder.‎

The first type, rosin-based flux, is made from pine tree sap and then dissolved in a solvent, ‎usually isopropyl alcohol. The resulting product is slightly acidic, which helps dissolve built-up ‎gunk and oxidization. In this state, the flux is called type-R rosin flux. However, manufacturers ‎can add additional acid activators to make the flux more aggressive and increase its ability to ‎dissolve heavier oxide films, which may be required when soldering at higher temperatures, such ‎as lead-free solder. Depending on the activation level, the flux is categorized into RMA (rosin ‎mildly activated) and RA (rosin activated). Due to its acidic nature, this flux must be cleaned off ‎the PCB after assembly to prevent it from corroding the board over time.‎