Solder does not always adhere well to components, resulting in a bad solder joint, bridged pins, or no connection at all. Use a flux and the correct temperature to fix these problems.
How to Decide What Type of Flux to Use and How to Use Flux! – Workbench Wednesdays
When solder melts and forms a bond between two metal surfaces, it forms a metallurgical bond by chemically reacting with the other metal surfaces. A good bond requires two things:
Remove dirt and dust by cleaning the surfaces or prevent it with good storage techniques. Oxides, on the other hand, require a different approach.
Oxides form on almost all metals when oxygen in the air reacts with the metal. On iron, oxidation is commonly called rust. However, oxidation affects tin, aluminum, copper, silver, and almost every metal used in electronics. Oxidation makes soldering difficult or impossible, preventing a metallurgical bond with the solder. Oxidation occurs all the time. However, it occurs more rapidly at higher temperatures, such as when soldering flux cleans metal surfaces and reacts with the oxide layer, preparing a surface for a good solder joint.
