Defect Description
Separation of internal trace from the resin laminate that is prone to propagation upon the exposure to environmental stresses
Defect Formation Process(s)
During wave solder process or SMT reflow operation, CTE mismatch in the material together with poor adhesive properties can cause overstress at the laminate interface that exceeds the adhesion strength. Contamination at the laminating interface can also reduce adhesion strength of the interfaces [1-2].
Moisture absorption by the laminate and incomplete curing of the material during production results in high vapor pressure during soldering process can also create delamination [1-2].
Another cause for this defect can be incorrect speed/feed ratio, worn drill bit, or incorrect drill geometry that results in the high temperature for localized thermal expansion copper inner layer during drilling [2]
|
List of Tests to Precipitate this Defect |
Failure Acceleration |
Likihood to Precipitate Defect (condition) |
Failure Mechanism(s) |
|
Thermal Shock |
• Cyclic thermal mechanical stress accelerates growth of delamination at the interface • Thermal mechanical stress accelerates cracking of the thin layer of copper that does not have sufficient mechanical support by fatigue or overstress |
✔ |
Thermal Fatigue Thermal Mechanical Overstress |
|
Random Vibration (RS/ED) |
• Random Vibration accelerates separation of the poorly bonded interface due to vibration-induced fatigue • Random Vibration accelerates cracking of the thin layer of copper that does not have sufficient mechanical support by fatigue or overstress |
✔/✇ |
Mechanical Fatigue Mechanical Overstress |
|
Combined Environment |
• Combination of Thermal Shock and Random Vibration |
✔ |
Combination of Thermal Shock and Random Vibration |
|
Bend Test |
• Bending can separate poorly bonded interface due to mechanical overstress • Bending can cause fracture of the thin layer of copper that does not have sufficient mechanical support |
✇
(Defect at a location with significant strain due to bending) |
Mechanical Overstress |
|
Hot Step Stress |
• Delamination growth caused by high vapor pressure due to the evaporation of absorbed moisture at high temperature [1] |
✇ (presence of moisture) |
Thermal mechanical overstress |
References
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