Case 1238 ยท Public preview
Repeated CTE Stress Can Exhaust SAC305 Joints Without Abnormal Aging
Lead-free solder joints on an immersion-silver assembly had accumulated 4,300 hours of thermal aging and 6,500 temperature cycles, with multiple joints extensively fractured.
Metallographic microsectioningSEMEDSElemental mappingMicrostructure comparison
What the evidence preview establishes
The solder joints were at or beyond thermal-fatigue end-of-life. Cyclic CTE-mismatch stress, rather than abnormal intermetallic growth, segregation, or grain growth, was the primary factor.
Why this case matters
When heavily cycled joints fail, separate cyclic mechanical damage from time-at-temperature effects. Fracture location, grain-boundary deformation, elemental distribution, and an as-received comparison are needed before attributing failure to intermetallic growth or contamination.
Full evidence reserved for MEMBER and STOREThe complete case includes the evidence sequence, four interpreted figures, alternative explanations, limitations, and practical application guidance.