i not read back all my IPC book since some time so it not very fresh to my memory
but i will find funny that a pcb shop will use lead-free pcb that not handle lead free process (reflow)
any pcb will go higher that it TG point during reflow and that make stress on via barrel (z)
but normally it only < 3 reflow run so it not a every day thermal stress or operating condition
normally standard commonly used laminate was now isola 410
if you have relfow delamination issue i will check first reflow most small batch oven (IR)
have bad /uneven temperature ... or check pcb quality old prepeg may cause that issue to
during year that i have run a pcb shop only time i see delamination issue was whit very old prepeg
now i have close my shop since asian pcb shop like internationalcircuits.com do it for less that my material cost ....
whit really good quality
Marc Lalonde CID.
IPC Certified PCB Designer.