The influence of electron beam evaporation coating technology on the strength of chemically tempered glass cover plates is a complex problem involving materials science, mechanical properties, and interface engineering. The following is a systematic analysis from the perspectives of mechanism of action, experimental data, and process optimization:

1. The mechanism of electron beam evaporation coating on glass strength

(1)Reconstruction of surface stress field

Characteristics of chemically tempered glass:passK?-Na?Ion exchange forms a surface compressive stress layer (usually500-800MPa, Depth30-100μm）It is the main source of strength.

The impact of coating introduction:

Thermal stress: Local high temperature during electron beam evaporation (aluminum evaporation source approximately)1500℃) may cause surface micro zone annealing and reduce compressive stress10-15%.

Intrinsic stress:Al?O?Hard films typically exhibit200-400MPaTensile stress, when combined with glass compressive stress, forms a stress gradient.

(2)Defect repair and introduction

Positive effects:Coating can fill surface microcracks (such as<100nmofGriffithCrack), prevent crack propagation, enhanceWeibullModulus.

Experimental data: Plating100nm Al? O?Glass with fracture toughnessK?cIncrease approximately8%(From)0.75→0.81 MPa·m1/2）.

Negative effects:Electron beam bombardment may generate new defects (such as non bridging oxygen vacancies), especially in high-speed deposition (>5nm/s）At that time.

2. Key influencing factors and experimental data

(1)Selection of membrane material

(2)The influence of process parameters

Substrate temperature:

＜150The effect on the tempered layer at ℃ can be ignored (the thermal stability threshold of the ion exchange layer is about300℃）。

＞200℃ will causeK?Reverse diffusion, compressive stress loss can reach up to30%.

Sedimentation rate:

Low speed（1-2nm/s）Form a dense film with significant improvement in strength;

High speed (>)5nm/s）Easy to produce columnar crystals, reducing interfacial bonding strength.

(3)Strength test comparison

#Four point bending strength test data (unit:MPa）

uncoated= 850± 50

Al?O?coating= 920 ± 40

TiO?coating= 780 ± 60

3. Process optimization plan

(1)Low temperature sedimentation technology

Electron beam scanning strategy:Adopting time-sharing scanning（duty cycle＜30%）Reduce heat load and control substrate temperature rise within<80℃。

Plasma assisted:introduceECRPlasma (power<500W）Promote low-temperature densification and reduce thermal impact.

(2)Interface Engineering

Gradient transition layer design:Sedimentation first10nm SiO?Buffer layer (thermal expansion coefficient transition), then platedAl?O?, which can improve the interface integration to>5J/m2.

Post treatment annealing:
250℃/2hVacuum annealing can release30-40%Tensile stress on the film layer without damaging the tempered layer.

(3)online monitoring

Laser ellipsometer: real-time monitoring of membrane stress (sensitivity)±10MPa）.

Surface Acoustic Wave Testing: Evaluating the Depth Change of Tempered Layer (Accuracy)±2μm）.

4. Typical application cases

(1)Smartphone cover plate

Requirement:
0.5mmChemical tempered glass（CS＞600MPa）Plated with anti fingerprint film（AF+Al? O?）.

Solution:

electron beam evaporation50nm Al? O?（1.5nm/s, substrate temperature120℃）

Ion beam assisted deposition（IAD，200eV Ar?）

Result:

Strength enhancement12%(From)620→695MPa）

Pencil hardness reaches9H

(2)Car display cover

Challenge:Requirements for resistance to sand and gravel impact（ISO 20567-1）.

Solution:adoptAl?O? /SiO?Multilayer film (total thickness)200nm）Through stress compensation design:

single layerAl?O?：+300MPaTensile stress

single layerSiO?：-150MPacompressive stress

Net stress after multi-layer combination<+50MPa

5. Failure Analysis and Improvement

6. Future development direction

(1)Ultra-low heat load sedimentation

Laser assisted electron beam evaporation:use1064nmLaser locally heats the target material to reduce the energy demand of the electron beam.

Cold electron beam technology:Using a field emission electron source (cathode temperature<500℃）。

(2)Intelligent stress regulation

Machine learning optimization:Predicting the optimal membrane system combination based on historical data (such asAl?O? /Si? N?Proportion).

Adaptive Coating System:Adjust sedimentation parameters through real-time stress feedback (closed-loop control).

(3)Composite functionalization

antibacterialAgdopingAl?O?：Co evaporationAgTarget (content<)3at.%）At the same time as increasing strength, achieve antibacterial rate>99%.

Conclusion:

The effect of electron beam evaporation coating on the strength of chemically tempered glass cover plate has bidirectional regulation:

Positive improvement: Through defect repair and surface strengthening, it can be achieved10-20%The intensity of growth;

Risk control: Strict management of thermal effects (substrate temperature<) is required150℃) and stress matching (net tensile stress of film layer ＜200MPa）.

Future technological breakthroughs will focus on:①Ultra low temperature deposition process (substrate temperature<50℃）；②coating-Collaborative design of tempered glass layer;③Integrated application of online non-destructive testing technology.