SHINHOP laser

With the widespread application of mobile full-screen technology in flagship devices from major manufacturers, the demand for cutting full-screen corners and irregular screens is also rapidly increasing. Laser cutting is a non-contact processing method, with no mechanical external stress applied, and has high cutting efficiency and technical level, showing significant advantages in full-screen cutting. This article will explore the technology of using ultrafast lasers to cut corners on full screens.
1 Application Background
Full screens have excellent display visual effects. With major mobile manufacturers like Apple, Samsung, Huawei, and Xiaomi successively launching their own full-screen products, full screens have become a trend in the industry.
A full screen usually refers to a mobile screen with a screen-to-body ratio greater than 80%, which is the inevitable result of achieving narrow bezels. Traditional mobile screens have an aspect ratio of 16:9, are rectangular, and have right angles at all corners.
Due to the need to place front cameras, distance sensors, earpieces, and other components on the device, there is a certain distance between the screen and the top and bottom edges of the device. Previous narrow bezels have been striving to narrow the left and right edges while avoiding narrowing the top and bottom edges. Narrowing the top and bottom edges requires a complete redesign of all front components of the phone, which is very difficult. Moreover, as the display area of full-screen mobile phones expands, the distance between the right angles of the display area and the rounded corners of the phone edges also decreases, making it easy to cause damage at close distances (Figure 1). Therefore, to reduce the possibility of screen breakage and reserve space for components, it becomes very necessary to process the screen into non-right angle irregular cuts.

Figure 1: Full screens with right angles are prone to damage
Screen corner cutting is performed according to different needs, including R corner cutting, C corner cutting, L corner cutting, and U-shaped grooves. The main purposes are twofold: on one hand, to make C or R corner cuts at the four corners of the screen, while reinforcing the edges with buffer foam to prevent screen breakage; on the other hand, to create U-shaped grooves at the top of the screen to reserve space for front cameras, distance sensors, earpieces, and other components.
2 Ultrafast Laser Corner Cutting Technology
Currently, the mainstream technologies for full-screen cutting include wheel cutting, CNC grinding, and laser cutting. Among them, laser cutting has advantages such as high cutting size accuracy, non-deformation of cutting seams, no burrs on the cutting edge, no tapering, fast cutting speed, high cutting yield, and the ability to achieve arbitrary shape cutting, showing significant advantages over wheel cutting and CNC grinding. Currently, irregular cutting of mobile full screens mainly involves L corners, C corners, R corners, and U-shaped groove cutting (as shown in Figure 2).

Figure 2: Various corner cutting diagrams for full screens
Laser cutting uses a high power density laser beam to irradiate the material being cut, quickly heating the material to its vaporization temperature, causing it to evaporate and form holes. As the beam moves relative to the processed material, cutting seams are formed.
Ultrafast lasers refer to lasers with pulse widths in the femtosecond or picosecond range, which rely on their extremely high peak power to instantly vaporize materials. Compared to nanosecond lasers or continuous lasers, the thermal effects are minimal, and the processed edges are neat, making them very suitable for screen corner cutting.

      (a) Internal etching cutting                          (b) Invisible wire cutting
Figure 3: Diagrams of internal etching cutting and invisible wire cutting
From the perspective of cutting schemes, laser cutting is divided into internal etching cutting and invisible wire cutting (Figure 3). Internal etching cutting utilizes the nonlinear absorption effect of ultrashort pulse lasers for processing, where valence band electrons in the glass absorb multiple photon energies, leading to the breaking of valence bonds in the glass, macroscopically manifesting as the glass material being 'ground' into micron-sized powder. The powder detaches from the glass body due to gravity, eliminating the need for a splitting device, allowing for arbitrary shape processing, but with a larger heat-affected zone; invisible wire cutting compresses the laser beam into a thin, long filamentous beam through special optical devices. The glass absorbs the laser energy, forming a modified layer, which cannot be directly separated due to intermolecular forces and requires external force for splitting. Invisible wire cutting can cut straight lines and some curves, has a small heat-affected zone, and high processing efficiency.
3 Ultrafast Laser Full-Screen Corner Cutting Equipment
For the full-screen laser corner cutting market, devices such as AGC10, AGC20, and AGC30 have been launched, equipped with automatic image positioning systems, automated axes, AOI, etc., ensuring automatic high-speed cutting processing and stable high-quality operation of the products.
The Amber laser adopts a picosecond fiber laser seed source combined with a free-space solid amplifier to achieve high peak power picosecond laser output. The use of a fiber seed source makes the Amber laser more stable in performance, compact in size, and flexible in output parameters compared to traditional solid picosecond lasers, while the solid amplifier ensures high peak power laser output, ensuring stable operation of the laser. The seed laser is amplified through a high-gain multi-pass amplifier to achieve greater than 25W high power picosecond laser output at a frequency of 1MHz, with output pulse width <15ps and beam quality M2<1.3.
The AGC series full-screen corner cutting equipment utilizes an invisible wire cutting method, offering advantages such as minimal edge chipping, high precision, and no cracks. It features a compact structure and a reasonable layout, with a stable motion mechanism that responds quickly, a user-friendly interface, and easy maintenance. The equipment is capable of processing C corners, R corners, U shapes, and other corner types for screens ranging from 3.97 to 8.4 inches, employing mechanical pins or ultrasound for splitting. The edge chipping is less than 10μm, the flange is less than 20μm, and the overall heat-affected zone is less than 80μm, ensuring smooth cutting edges and cross-sections.
4 Conclusion
As users' demands for visual experience and appearance of mobile phones increase, and as upstream manufacturers continuously upgrade their technologies, the application of full screens is becoming more widespread. Currently, flagship devices from major mobile manufacturers have fully adopted full screens. With the maturity of technology and the decrease in costs, full screen technology will further expand to mid-range and even low-end products, leading to a significant increase in demand for irregular cutting, and the demand for full-screen corner cutting equipment will also explode.