Chemical Strengthening (Ion Exchange)

K⁺/Na⁺ Ion Exchange Process for Ultra-Strong Thin Glass — Up to 900MPa

Engineer Consultation

Process Overview

Ion Exchange for Ultra-Thin Glass

Chemical strengthening is the primary hardening method for thin glass (0.2-3mm) that cannot be physically tempered. Glass is submerged in molten KNO₃ at ~400°C for 2-8 hours; smaller Na⁺ ions are replaced by larger K⁺ ions, creating high surface compressive stress (600-900MPa) that dramatically increases strength and impact resistance.

Advantages over physical tempering: works on thin glass (0.2mm min), no optical distortion, no warping, higher surface stress, can be applied after CNC shaping. Ideal for smartphone cover glass, tablet screens, wearables, optical lenses, and medical devices.

Parameters

Process Parameters

Parameter	Value
Bath Temperature	380-420°C
Immersion Time	2-8 hours
Compressive Stress	600-900MPa
DOL (Depth of Layer)	10-50μm
Surface Hardness	Up to 9H
Glass Types	Aluminosilicate, Soda-Lime, Borosilicate

Capabilities

Key Strengthening Capabilities

Thin glass hardening (0.2mm+)

No optical distortion

Dimensional stability (no warping)

Up to 900MPa compressive stress

Post-CNC treatment

Up to 9H pencil hardness

Applications

Smartphone cover glass
Tablet screens
Wearables
Optical lenses
Thin industrial displays
Medical device windows

FAQ

Chemical Strengthening Questions

Chemical strengthening is primarily used for thin glass from 0.2mm up to 6mm thick. For glass thicker than 6mm, physical tempering is generally more effective and economical. Our optimal range is 0.3mm to 3mm for consumer electronics and optical applications. We can process ultra-thin glass down to 0.2mm with special fixturing to prevent breakage during the ion exchange process.

Chemical strengthening offers several advantages over physical tempering for thin glass: no optical distortion or warping (critical for displays and optics), works on much thinner glass (0.2mm min vs ~3mm min for tempering), higher surface compressive stress (600-900MPa vs ~400MPa), and can be applied after CNC machining without affecting dimensional accuracy. Physical tempering is better for thicker glass (3-19mm) where heat distortion is less critical.

DOL (Depth of Layer) is the depth of the compressive stress layer beneath the glass surface, typically ranging from 10μm to 50μm depending on immersion time and temperature. Deeper DOL provides better resistance to deep scratches and edge damage. We can adjust DOL by controlling bath temperature and immersion time: shorter times for shallow DOL, longer times for deeper DOL. Typical DOL for consumer electronics is 20-30μm.

No. Like physically tempered glass, chemically strengthened glass cannot be cut, drilled, or edged after strengthening. All fabrication (CNC machining, hole drilling, edge finishing) must be completed BEFORE the ion exchange process. Attempting to modify chemically strengthened glass will cause it to shatter completely due to the internal stress state. Always provide final dimensions before strengthening.

Our standard chemical strengthening process achieves surface compressive stress (CS) of 600-900MPa, with central tension (CT) controlled to prevent spontaneous breakage. For aluminosilicate glasses like Corning Gorilla or Asahi Dragontrail, we can achieve CS up to 900MPa with DOL 20-40μm. We optimize the process for each glass type and application, balancing CS, DOL, and CT for optimal performance without compromising safety.

Engineer Consultation

Specify your glass type, thickness, and strength requirements — we'll optimize the ion exchange process for your application.

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