Defect Description
Any combination of edge roughness, copper spikes, etc., that reduces the specified minimum conductor spacing in isolated areas[1], which is prone to electrochemical migration upon the exposure to humid environment [2][3].
Defect Formation Process(s)
This defect can be a result of poor process control. For example, nodules can be a result of inclusion of foreign materials at the core of the nodule, from other procedures such as laser drilling [4].
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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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Temperature, Humidity, Bias |
• Humidity and high temperature accelerates dendrite growth by electrochemical migration [3-5] • The increase in voltage gradient increase probability of dendrite formation [6] |
✔ |
Electrochemical migration |
|
Hot Step Stress |
• High temperature increases the propagation rate of dentrites given the presence of moisture [4-5] |
✇ (The presence of moisture) |
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|
Thermal Shock |
• Same as Hot Step Stress |
✇ (Same as Hot Step Stress) |
|
|
Combined Environment |
• Same as Hot Step Stress |
✇ (Same as Hot Step Stress) |
[7]
References
[1] IPC, Acceptability of Printed Boards, IPC-A-600-H, 2010.
[2] Zhan S., Azarian M. H., Pecht M., “Reliability of Printed Circuit Boards Processed Using No-Clean Flux Technology in Temperature-Humidity-Bias Conditions” IEEE Transactions on Device and Materials Reliability, vol. 8, no. 2, 2008.
[4] P. Lall, M. Pecht, and E. Hakim, Influence of Temperature on Microelectronics and System Reliability: A Physics of Failure Approach, CRC Press, New York, 1997.
[5] 8. G. DiGiacomo, “Metal Migration (Ag, Cu, Pb) in Encapsulated Modules and Time to Fail Model as a Function of the Environment and Package Properties,” IEEE/ Proceedings of the IRPS, pp. 27 – 33. 1982.
[6] L. Zou and C. Hunt, “The Effect of Test Voltage, Test Pattern and Board Finish on Surface Insulation Resistance Measurements for Various Fluxes,” NPL Report CMMT(A) 222, September 1999.
Permission for pictures
[7] IPC, Acceptability of Printed Boards, IPC-A-600-H, 2010. illman C., “Reliable plated through via design and fabrication.” DFR Solutions
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