AN EXPERIMENTAL METHOD TO INVESTIGATE TRUE STRESS DURING THE FATIGUE OF LEAD-FREE SOLDERSAuthors: Milos Dusek and Chris Hunt
Company: National Physical Laboratory
Date Published: 9/24/2006 Conference: SMTA International
The experimental solder joint under test has typical assembly dimensions. Crack growth in this standard solder joint specimen is confirmed by microscopy, both optical and ultrasonic. Knowing how the true stress develops and the actual values will significantly improve reliability predictions. Furthermore FEA models that include degradation can be refined to replicate the observed behaviour and hence improve life-time modelling in a wider sense. The recent data show that true stress values for fatigued lead-free solder joints are reaching well above 30 MPa which is significantly more when compared to estimated nominal stresses based on unaffected solder joint cross-sectional area.
Key words: fatigue, stress, solder joints
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