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. While these joints may look acceptable at first glance, they can become problematic over time, especially when exposed to vibration, thermal. Cold solder joints are one of the most common — and most dangerous — soldering defects in PCB assembly. They often look harmless, but can cause intermittent failures, unexpected resistance spikes, and field returns long after a product has passed initial testing.
