Defect Description
Voids present in a microvia that can lead to local stress concentration and crack initiation upon the exposure to environmental stresses such as temperature cycling and vibration.
Defect Formation Process(s)
Possible causes for this defect can be gases being trapped in microvias cannot escape during reflow [1] and improper control during the copper plating process [2]
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List of Tests to Precipitate this Defect |
Failure Acceleration |
Likihood to Precipitate Defect (condition) |
Failure Mechanism(s) |
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Thermal Shock |
• Cyclic thermal mechanical stress accelerates crack initiation or growth around voids where stress concentration is higher • Thermal mechanical stress causes fracture of the microvia around the voids where local stress concentration is high |
✔ |
Thermal Faitgue Thermal mechanical Oberstress |
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Random Vibration (RS/ED) |
• Random Vibration accelerates fatigue cracking of the microvia around voids where stress concentration is higher • Random Vibration can cause fracture of the microvia around voids where stress concentration is higher |
✔/✇ |
Mechanical Fatigue Mechanical Overstress |
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Combined Environment |
• Combination of Thermal Shock and Random Vibration |
✔ |
Combination of Thermal Shock and Random Vibration |
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Bend Test |
• Bending can cause fracture of the microvia around voids where stress concentration is higher |
✇ (Defect at a location with significant strain due to bending) |
Mechanical Overstress |
References
[1] Ghaffarian R. “Reliability of PWB Microvias for High Density Package Assembly”, NASA Electronic Parts and Packaging Program (NEPP), 2006.
[2] Ning Y., Azarian M. H., and Pecht M., “Simulation of the Influence of Manufacturing Quality on the Reliability of Microvias,” Proceedings of IPC APEX Technical Conference, Las Vegas, NE, 2014
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