It could be zillions of reasons and unless proper FA is done you are NEVER going to figure out what exactly caused the problem. ------Original Message------ From: Ramakrishnan Saravanan Sender: TechNet To: [log in to unmask] ReplyTo: TechNet E-Mail Forum ReplyTo: Ramakrishnan Saravanan Subject: [TN] corrosion under Solder Mask Sent: Mar 2, 2013 18:13 Dear all, We have received few MLBs from a contract supplier. The board was inspected and accepted for wiring. The assembly is for high reliability applications. We conformal coated, tested,thermal cycled and closed the package. We opened the package for some rework, we found corrosion under solder mask on some tracks. The corrosion is in the form of blisters and localized. Center of the tracks or edge or localized and not covering the entire width of the tracks. What could be the reason for corrosion under solder mask ?. How to diagnosed for root cause analysis ? regards, R.Saravanan Regards, Vladimir SENTEC Testing Laboratory Inc. 11 Canadian Road, Unit 7. Scarborough, ON M1R 5G1 Tel: (647) 495-8727 Cell: (416) 899-1882 www.sentec.ca ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________