Application of glass thinning technology in electronic equipment

A piece of glass with a thickness of only 30 microns (0.03mm), which is a quarter thinner than A4 paper, can withstand more than 1 million times Bend without breaking. This achievement, which seems to violate the common sense of materials, is quietly supporting the morphological revolution of consumer electronic products from rigidity to folding.

In the field of smart phones, tablets and wearables, Glass thinning It has gone beyond the simple concept of “thinning” and become a key process to connect optical performance, mechanical strength and industrial design. When the glass thickness exceeds the physical limit, its bending strength will decline in a square order – the strength of 1.6 mm glass is only 25% of that of 3.2 mm glass. Engineers must solve the problem simultaneously Strength collapse, stress control and micro crack propagation Such chain reaction can make the glass still meet the durability requirements of electronic equipment under the limit thickness.

1、 Technological Evolution from Rigid to Foldable

There is always a contradiction in the demand of electronic equipment for glass: it should be light, thin, transparent, and hard and pressure resistant. Although the polymer plastic used in early folding screen mobile phones can be bent, there are serious defects – insufficient surface hardness leads to scratches, low optical transmittance, and irreversible plastic deformation after repeated bending. Glass is an ideal substitute material because of its intrinsic high light transmittance (>90%) and hardness (up to 600HV), but the challenge of brittle fracture must be overcome.

The scientific research team of China Building Materials Group passed the redesign Glass cube Adjust the silicon oxide network structure and alkali metal ion content to keep the structural integrity of 30 μ m ultra-thin glass when the bending radius is 0.5mm. The key to this breakthrough lies in the discovery of the “flexible critical point” – when the glass thickness exceeds the threshold of 70 microns, real folding can be achieved. Combined with ion exchange strengthening technology (immerse the glass into molten potassium salt to replace ions), and finally form on the surface ＞ 700MPa compressive stress layer And realize the service life of millions of times of bending.

2、 Analysis of core thinning technology

The realization of electronic ultra-thin glass requires multidisciplinary integration and innovation:

Progressive thinning+sectional strengthening : The process path developed by China Building Materials Group first pre thinned the glass to 100 microns for the first chemical strengthening, established the surface compressive stress layer, and then continued to thin to the target thickness. This strategy reduces microcrack growth by 50% and increases yield by 30%
Laser precision machining : Femtosecond laser cold processing technology (μ J level pulse energy) enables non-contact cutting, with an accuracy of ± 1 μ m and edge roughness of<5nm. Tongkuai’s Top Clear system can perform curve cutting of 70-200 μ m glass to meet the requirements of folding screen profile design
Chemical mechanical planarization : Combined with nano abrasive and chemical corrosion, the defects such as pits and water ripples on the glass surface after thinning are solved. The optimized process reduces the surface roughness to ＜0.5nm (Atomically smooth), providing an ideal substrate for subsequent coating

3、 Key application scenarios in electronic equipment

1. Folding screen phone cover

The 30 micron ultra thin flexible glass (UTG) has become the core cover material of Samsung Galaxy Z Flip, Huawei Mate X and other folding screen mobile phones. Compared with traditional CPI plastics, UTG provides a touch hardness closer to ordinary glass, and will not yellowing and aging due to ultraviolet radiation. However, the yield of mass production is only 30-50%, and the cost is as high as 800 dollars/square meter, which is still the bottleneck of popularization.

2. Thin display panel

In the field of OLED and Micro LED display, glass substrate thinning directly improves equipment lightweight and optical performance:

Chemical thinning Large area thinned substrate is etched by hydrofluoric acid, but the reaction uniformity needs to be controlled to avoid edge pits
Laser thinning can selectively remove materials and correct lens aberrations, so that AR glasses lenses can be thinned to 0.5mm, field angle can be expanded to 120%, and the overall weight can be reduced by 40%
After thinning, the light transmittance of the glass is improved and the backlight power consumption is reduced. The mobile phone screen thickness is reduced from 0.5mm to 0.2mm, which can reduce the weight of the whole machine by about 8%

4、 Extreme challenge of project implementation

The “Valley of Death” needs to be conquered to convert the laboratory 30 micron glass into mass production products:

Dust sensitivity index increases : The dust with a particle size of 5 μ m can be magnified as a through crack after etching. It needs a 10 level clean room (ISO Class 4) and an electrostatic suspension transmission system to reduce the removal damage rate to<0.1%
Stress management art : Bourne Optics has developed an integrated process of laser engraving+chemical etching to pre carve a chamfer structure inside the glass, reducing 70% of the times of transportation and positioning, and improving the edge strength by 200%
Thickness control precision : Temperature fluctuation of ± 1 ℃ can lead to frequency deviation of quartz crystal vibrator, so it is necessary for constant temperature workshop (± 0.5 ℃) and active damping platform to suppress resonance and ensure thickness uniformity of ± 1 μ m

5、 Environmental protection and cost innovation

Traditional hydrofluoric acid (HF) etching is facing toxic pollution and cost dilemma, and the new generation process is breaking through:

Acid free thinning technology : The environmentally friendly thinner mixed with citric acid, oxalic acid and sodium fluoride is used to realize wastewater recycling treatment and reduce the discharge treatment cost by 30%
Material recycling : The thinner solution can be recycled by cooling crystallization and adding activator; The cleaning water is subject to cold water filtration and ultra purification treatment to achieve zero discharge of production sewage
Cost reduction of composite process : Hainan University has developed pit inhibiting liquid to reduce the defect rate caused by micro scratch by 60%; Dinghongrun Technology reduces the comprehensive cost of UTG parent glass by optimizing the proportion of thinning process

6、 Future Battlefield: Race from Micron to Nano

Glass thinning technology is moving towards a deeper dimension:

Flexibility limit breakthrough : China Building Materials Group marched towards 10 micron glass (close to the diameter of red blood cells) to explore the application of neural interface and implantable equipment
Intelligent function integration : The sensor, dimming film (PDLC) and antenna are fused on the ultra-thin substrate. The smart sensing glass developed by Fuyao Glass in cooperation with Huawei has been installed in Interworld M9, realizing 50 environmental data acquisition per second
Cross industry integration BOE combines flexible display technology with dimming glass to create a new market with an annual output value of 8 billion yuan; Photovoltaic roof glass and Internet of Vehicles communication glass become the next generation integration direction

The glass thinning technology has evolved from a pure thickness competition to a system engineering integrating material science, precision processing and function integration. When the thickness is compressed from millimeter to micron, the molecular bonding mode and stress distribution model of glass need to be reconstructed for each micron breakthrough. Just like that piece in the folding screen phone 30 micron flexible glass It is not only a breakthrough in physical thickness, but also redefines the morphological boundary of electronic devices – in the future, more extreme glass thinning technology will unlock new species such as curly mobile phones, neural interface devices, and let hard and transparent silica show amazing flexibility and wisdom.