One Head-in-Pillow Joint Can Be Causal Even When a Board Contains Several Other Defects

What the evidence preview establishes

A head-in-pillow separation at one electrically suspect BGA ball was the most likely cause of the board failure. Voiding, warpage-related pad cratering, and solder-mask encroachment were significant additional defects, but they represented different mechanisms at other locations.

Why this case matters

Do not let a board with many anomalies become a single undifferentiated root-cause list. Correlate each defect with its location, morphology, and circuit significance; a head-in-pillow open, warpage-driven pad crater, interfacial void, and mask-induced nonwetting joint require different corrective actions.