6.2: Biaxial Strength of Ultrathin AMLCD Glass Substrates

The biaxial strength of ultrathin AMLCD glass substrates with thickness ranging from 0.25mm to 0.70mm was measured in the concentric ring fixture. The data, based on a large sample size of 25mm × 25mm square specimens, show that the strength is independent of glass thickness and approaches 630 MPa. The choice of 25mm × 25mm specimens for measuring the biaxial strength was dictated by minimizing large deflections and associated membrane tension in the test region. The effect of surface area under test was taken into account by using Weibull distribution which demonstrated constancy of surface strength irrespective of substrate thickness. Thus, thin and ultrathin AMLCD susbtrates have similar biaxial strength as measured in the concentric ring fixture.