Diagnose cold solder joints on PCBs: causes, detection, 5-Why analysis, fishbone diagram, corrective actions. Learn the D0–D8 steps, root cause analysis, cor...
What Is a Cold Solder Joint? A cold solder joint is a connection that formed without enough heat or with contaminated surfaces, so the intermetallic compound (IMC) layer never developed properly. The joint may pass a functional test and then fail intermittently in the field as thermal cycling opens a microscopic crack. Cold solder is a common cause of no-fault-found returns in automotive and industrial electronics, and it is almost always a process-control problem rather than a component problem. Symptoms Dull, grainy or porous joint surface compared with a shiny, smooth good joint Intermittent electrical connection — passes at test but fails in the field Joint resistance above 50 mΩ Cracks at the pad-to-solder or lead-to-solder interface under a microscope Fillet that does not wet properly or pulls away from the pad Affected Components PCBAs in automotive, industrial and consumer electronics Through-hole and surface-mount (SMT) solder joints BGA, QFN and SOIC packages and discrete component joints ENIG, HASL, OSP and immersion-tin pad finishes Detection Methods Visual inspection (10-40x): check gloss, wetting angle and fillet shape X-ray: reveals hidden cold solder under BGA and QFN packages Automated optical inspection (AOI): machine vision checks shape, colour and reflectivity ICT / flying probe:...
