Choosing the right flux types for solder

Solder is universally used for electronics to form solder joints and attach your parts to the PCB. Choosing the right solder for your electronic application can be challenging because there are many different features of solder for particular situations. Flux type is one of the features to keep in mind that can help to make a good solder joint. Here are three common flux types listed below.

  1. No-Clean
    The term “No-clean” means that this flux is formulated such as to avoid interfering with your board and cleaning is not necessary. However, the residues from no-clean flux are very difficult to remove and it requires the use of flux cleaners. You do not need to clean this residue, but it will be there regardless.

  2. Rosin typed
    Rosin flux is a traditional solder which is based on pine tree rosin. Roxin flux is active enough to solder electronic assemblies and the residue has a very good insulation resistance.
    Two common types of rosin flux are Rosin Activated (RA) and Rosin Mildly Activated (RMA). RA is the most acidic one. The residues from rosin flux are mildy corrosive and should be removed after soldering to avoid eventual failure of the board. RMA solder has been formulated such that the cleaning, while recommended, can be omitted. Rosin flux can be removed with isopropyl or isopropanol alcohol followed by a de-ionized water rinse. Some agitation with a soft bristle brush is usually necessary.

  3. Water Soluble
    Water soluble flux is relatively easy to remove. Rinse the circuit under warm water and agitate with a soft bristle brush if necessary. An ultrasonic cleaner can be used as well. Follow up with a rinse in de-ionized water or steam distilled water.