Delamination or blistering may occur in clad laminate materials either between plies of laminate, or between the laminate and the foil cladding. Any occurrence, either in the as-received condition or after routine thermal stress testing at receiving inspection is evidence of a major flaw, and the material should be rejected, since the defect will almost always propagate during the normal stresses of manufacturing.
Causes of Delamination "Quality Assessment Of Printed Circuit Boards