Chemically Strengthened Glass DOL Calculator
Glass engineering & smartphone optics: Calculate ion exchange Depth of Layer (DOL), surface Compressive Stress (CS), Central Tension (CT), and frangibility threshold.
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Frequently Asked Questions
How does chemical strengthening (ion exchange) strengthen glass?
Glass is immersed in a bath of molten potassium nitrate (KNO₃) at ~420°C. Larger potassium ions (K⁺, radius 138 pm) diffuse into the glass surface, replacing smaller sodium ions (Na⁺, radius 102 pm). When cooled, the crowded larger potassium ions create an immense surface compressive stress layer (CS ~ 600–900 MPa) that seals microscopic flaws and arrests crack propagation.
What is the Depth of Layer (DOL) and why is it important?
The Depth of Layer is the thickness of the surface layer under compressive stress, typically 25 to 50 µm in premium display cover glass. A deep DOL ensures that everyday abrasive gouges and micro-scratches do not penetrate into the underlying tensile core, preventing catastrophic shatter during drop impacts.
What is central tension (CT) and frangibility?
To satisfy internal static equilibrium, the surface compression must be balanced by tensile stress in the central core (Central Tension, CT). If CT exceeds the material's critical frangibility limit, any flaw piercing the outer compressive shell releases immense stored elastic energy, causing spontaneous explosive fragmentation into thousands of tiny blunt dices.