A cold solder joint forms when solder does not melt or wet the pad and component lead completely. Instead of creating a unified bond, the solder cools prematurely or never flows correctly, resulting in a dull, grainy, or uneven connection. This lack of proper bonding can lead to various issues, including increased electrical resistance, intermittent functionality, and a higher likelihood of component. A cold solder joint is one of the most common reliability defects in PCB and PCBA assemblies, and it continues to be a major source of intermittent failures across consumer electronics, industrial controls, medical devices, automotive modules, and aerospace hardware. It has two main functions: Mechanical connection: Fix the components firmly and prevent them from moving.