To spot them, use a magnifying lens to check solder joints for convex shapes or gaps that allow light to pass through the joints. Unlike proper welds where the base metal melts and blends seamlessly with the filler material, cold joints create weak mechanical. This guide explains what a cold solder joint is, what it looks like, why it happens, and how to reliably identify, fix, and prevent it. Whether you're troubleshooting a failed board or optimizing an SMT production line, this article gives you a practical, engineering-level reference for eliminating. Are you struggling with unreliable connections on your PCB due to cold solder joints? Hot air rework is a powerful technique to fix these issues and restore your board's functionality. Cold solder joint are the most common problems during PCB soldering. Let's follow ELE PCB to get a deep understanding of cold solder.