Hi Susan,
Unless there is an excursion past Tg, there is no loading condition that
would create the stresses necessary to cause either barrel cracking or
inner-layer separation. HASL certainly would do that, but on ENiG boards
there is no reason for such a temperature excursion. So you should not see
any  barrel cracking or inner-layer separation prior to Thermal Stress
testing even on very low-quality PCBs. If you do, they saw some thermal
excursion somewhere after wet processing.

Regards,
Werner Engelmaier

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