Defect Description
A PTH is not fully filled 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)
Defects introduce in the copper plating during the hole drilling process can affect PTH solderability and hole fill during soldering process [1-3].
|
List of Tests to Precipitate this Defect |
Failure Acceleration |
Likelihood to Precipitate this Defect (condition) |
Failure Mechanism(s) |
|
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 PTH around the voids where local stress concentration is high |
✔ |
Thermal Faitgue Thermal mechanical Oberstress |
|
Random Vibration (RS/ED) |
• Random Vibration accelerates fatigue cracking of the PTH around voids where stress concentration is higher • Random Vibration can cause fracture of the PTH around voids where stress concentration is higher |
✔/✇ |
Mechanical Fatigue Mechanical Overstress |
|
Combined Environment |
• Combination of Thermal Shock and Random Vibration |
✔ |
Combination of Thermal Shock and Random Vibration |
|
Bend Test |
• Bending can cause fracture of the PTH around voids where stress concentration is higher |
✇ (Defect at a location with significant strain due to bending) |
Mechanical Overstress |
[5]
References
[1] Viswanadham P., Singh P., Failure Modes and Mechanisms in Electronic Packages. New York: Chapman & Hall, 1998.
[4] IPC, PCB Quality Evaluation Handbook, IPC-QE-605A Revision A, 1999
Permission for pictures
[5] IPC, PCB Quality Evaluation Handbook, IPC-QE-605A Revision A, 1999
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