1) What is the hardness of the coating. A hard coating will tear the
     parts off the panel with a typical CTE mismatch and thermal cylcing.

     2) How are you applying the coating? What is the viscosity? Does the
     material shrink on cure?

     3) What is the component height off the panel. Is it sufficient for
     capillary action to suck coating underneath, or is it too close or too
     large to allow for coating underfill?

These make a difference in whether you properly underfill.



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Subject: [TN] ASSY: SMT/Temp. Cycling Test Failures revisited
Author:  "BROMLEY; Bill" <[log in to unmask]> at INTERNET