You can hear such questions often if the art of soldering is new for you. Unfortunately, the answer may be a little bit complicated. Flux isn’t always necessary to solder several elements; however, it is quite useful in certain situations. In general, flux allows creating a strong bond between the solder and the metal surfaces to join them together. Without using flux, the solder may not stick properly, and the joint between two surfaces may be weak.
In what cases is it possible to solder without using flux?
There are some cases whether it is possible to solder without using flux. For example, if the solder joint is clean enough and free of contaminants, it may be possible to solder without flux. Besides, sometimes you can not use flux when you are going to bind a tiny component since there is too much metal to heat up and solder.
One more example is when you are going to solder a wire to a connector. In this case, the connector itself will provide the necessary flux. However, when you solder a wire to a certain metal surface, you will need flux to get a good bond.
What is flux, and how does it work?
Soldering is defined as the process of joining two metals by melting a filler metal between them. Most commonly people solder tin and lead alloys, but modern solder processes also contain various other metals, such as silver, copper, and zinc.
Flux is a chemical agent that helps to remove a certain number of oxides from the both surfaces of the metals, and it also helps the solder adhere to the surfaces. In general, flux is unnecessary for good soldering results, but it can make the process easier.
So, here you can find the main functions of flux, which you apply to joints:
- Cleaning action – removing contaminants such as oxides, oils, grease, and contaminants on joint surfaces.
- Flux residue forms a barrier between the molten solder and the atmosphere to prevent re-oxidation of metals.
So, what types of flux are possible to use for soldering?
On the market, nowadays, you can find three main types of soldering flux, such as rosin-core, acid-core, and water-soluble soldering flux. Each of them has specific properties that make it better suited for certain applications.
Rosin-core flux is used for general purpose soldering. It has a mild fluxing agent that easily can clean the solder joint and prevent oxidation.
People often use acid-core flux to sell metals, challenging with rosin-core solders, such as aluminum. The fluxing agent in acid-core solder is more aggressive, which helps break down the metal’s surface and create a stronger solder joint.
As for water-soluble flux, people use it for soldering delicate or sensitive components, such as PCBs. The fluxing agent in water-soluble solder is less aggressive than the fluxing agent in acid-core solder, which helps minimize the potential for damage to the component.
What type of flux do people usually use for soldering?
People commonly use rosin-based flux for soldering. It can be in the form of a paste, a liquid, or a resin. This type of chemical agent is a non-corrosive, organic acid that helps to clean your metal surface and provides a good solder joint. It is also water-soluble, so you can remove it without problems after the soldering process.