PC cold joint
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. They often look harmless, but can cause intermittent failures, unexpected resistance spikes, and field returns long after a product has passed initial testing. While these joints may look acceptable at first glance, they can become problematic over time, especially when exposed to vibration, thermal. This is the most common type of defect especially found under POP packages, where two or more Chip Scale Packages (CSP) or Ball Grid Array (BGA) components are placed one on top of the other and reflow soldered.
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