Case 999 ยท Public preview
Heel-Fillet Fractures Can Reveal Vibration Fatigue in Heavy QFPs
An assembly failed during vibration testing after numerous solder joints fractured around two large, heat-sink-equipped QFP components.
Optical microscopySEM fractographyEDSFracture-location mappingAssembly survey
What the evidence preview establishes
High-cycle vibration fatigue initiated in the heel fillets and propagated toward the toes through eutectic Sn-Pb solder near the Cu-Sn intermetallic interface. Component mass, excessive vibration loading, or both produced the damaging stress.
Why this case matters
For vibration-related QFP opens, map fracture distribution against the loading axis and examine the heel-to-toe propagation direction. Pair fractography with board-response measurements before changing the solder process.
Full evidence reserved for MEMBER and STOREThe complete case includes the evidence sequence, four interpreted figures, alternative explanations, limitations, and practical application guidance.