Voids in solder joints are internal cavities or areas of trapped gas that form within solder during the assembly process. Small amounts of voiding may be acceptable depending on the application, but excessive or strategically located voids can reduce the mechanical, thermal, and electrical reliability of a solder connection. Voids are particularly important in electronic assemblies where solder joints are responsible for both mechanical attachment and electrical or thermal conduction.
Voiding can occur in surface-mount assemblies, power electronics, semiconductor packages, LED assemblies, automotive electronics, and other high-reliability applications. The problem may be discovered through X-ray inspection, during thermal cycling, after mechanical testing, or when a component fails in service.
Determining why voids formed requires more than simply measuring their size. The composition of the solder, condition of the surfaces, reflow profile, flux chemistry, pad design, component configuration, and manufacturing conditions may all contribute to void formation. Analytical testing can help determine whether voiding is associated with contamination, material chemistry, process conditions, or another manufacturing issue.
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