Silicon nitride mobile phone back cover plate

Abstract

The utility model discloses a kind of silicon nitride mobile phone back cover, at least four corner regions of the back cover are formed with recess structure by laser engraving;The recess structure is composed of grid by longitudinal and transverse interlaced line groove, and the outside contour length of the enclosed area is 0.5 millimeter to 5 millimeter;The depth of the line groove is 10% to 30% of the cover thickness.By preset gradient recess structure active guidance and dispersion stress, avoid the fatal stress concentration point in local generation.This also has crack inhibiting effect, and the recess structure formed by laser engraving constitutes a large number of micro defects and boundary in material, when crack expands to these recess structure, passivation, deflection, bifurcation or termination will occur, greatly increase the path and required energy of crack propagation, thereby effectively prevent the occurrence of macroscopic rupture.

Description

Technical Field

[0001] This utility model relates to the field of mobile phone component technology, specifically to a silicon nitride mobile phone back cover. Background Technology

[0002] With the development of smartphones, the materials used for phone back covers have evolved from plastic and metal to glass and ceramics. Silicon nitride ceramics, due to its high hardness, good wear resistance, excellent dielectric properties, and smooth feel, has become an ideal material for high-end phone back covers. However, like all ceramic materials, silicon nitride has an inherent brittleness problem; its impact resistance is poor, and it is prone to cracking when the phone is accidentally dropped, leading to the failure of the entire device.

[0003] In existing technologies, impact resistance is typically improved by increasing the thickness of the back cover or using cushioning foam, but this sacrifices the phone's slimness and heat dissipation. Other technologies employ applying an explosion-proof film to the ceramic back, but this has limited effectiveness and affects the appearance and feel. Therefore, how to effectively improve the drop impact resistance of silicon nitride ceramic back covers without increasing thickness or altering the excellent properties of the ceramic itself has become a pressing technical problem to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a silicon nitride ceramic mobile phone back cover. By designing and processing specific gradient microstructures on its surface, it can effectively disperse and absorb impact stress and inhibit crack propagation, thereby significantly improving the product's drop ball test height and drop impact resistance.

[0005] The specific technical solution of this utility model is as follows: A silicon nitride mobile phone back cover, wherein at least four corner areas of the back cover are laser-engraved with groove structures; the groove structures are composed of crisscrossing grooves forming a grid, and the outer contour side length of the enclosed area is 0.5 mm to 5 mm; the depth of the grooves is 10% to 30% of the thickness of the cover.

[0006] In some embodiments, the outer contour side length of the enclosed area is 0.5mm or 1mm or 1.5mm or 2mm or 2.5mm or 3mm or 3.5mm or 4mm or 4.5mm or 5mm, preferably 0.5-2mm; the depth of the groove is 10% or 15% or 20% or 25% or 30% of the cover plate thickness, preferably 20% of the cover plate thickness.

[0007] The groove structure covers the entire outer surface of the cover plate.

[0008] Preferably, in some embodiments, the distribution density of the grooves on the outer surface of the rear cover plate increases in a gradient from the center of the cover plate to the surrounding corner areas.

[0009] The gradient change of the distribution density is continuous and gradual.

[0010] The width of the groove is 10-50 micrometers.

[0011] The grid structure is a square grid, a rectangular grid, or a diamond grid.

[0012] The grooves within the same groove structure are carved to a uniform depth, or the depth of the grooves gradually decreases from the center of the enclosed area to the edge.

[0013] The rear cover plate is a pure silicon nitride cover plate or a composite silicon nitride ceramic cover plate. Compared with the prior art, this utility model has the following significant advantages: This invention does not passively withstand impacts, but actively guides and disperses stress through a pre-designed gradient groove structure, avoiding the formation of fatal stress concentration points in localized areas. Furthermore, it has a crack-inhibiting effect. The groove structure formed by laser engraving creates numerous microscopic defects and boundaries within the material. When cracks propagate to these groove structures, they become blunted, deflected, bifurcated, or terminated, significantly increasing the crack propagation path and the energy required, thereby effectively preventing macroscopic fracture.

[0014] In addition, this patent also features a gradient reinforcement design, which achieves "zonal reinforcement" by setting groove structures in different areas of the back cover. The reinforcement level is highest in the most vulnerable corners and edges, while the reinforcement level is lower in the relatively safe center area, achieving an optimal balance between material performance and lightweight / aesthetics.

[0015] The groove structure utilizes laser engraving technology, which easily enables high-precision and high-efficiency processing of complex microstructures. This process is clean and environmentally friendly, easily integrated with existing ceramic back cover production lines, and does not introduce chemical pollution or significantly increase costs. This strengthening method only processes the surface, without altering the physicochemical properties of the silicon nitride ceramic body, perfectly preserving its advantages of high hardness, wear resistance, good heat dissipation, and a smooth feel. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the distribution on the outer surface of the silicon nitride mobile phone back cover substrate in Embodiment 1 of this utility model. Figure 2 This is a schematic diagram of embodiment 3 of the present utility model.

[0017] Wherein 1-line groove; 2-groove structure. Detailed Implementation

[0018] To make the technical problems solved, technical solutions, and beneficial effects of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model. Example 1

[0019] See Figure 1 As shown, a silicon nitride ceramic mobile phone back cover with a thickness of 0.5mm has a large number of evenly distributed grid-like groove structures engraved on its outer surface by picosecond laser, with an engraving depth of 0.1mm. Engraving these grooves divides the back cover surface into multiple independent small units. Figure 1 From left to right, the grid sizes are as follows: Figure 1 a is 0.5×0.5mm, Figure 1 b is 1×1mm. Figure 1 c is 5×5mm. Drop ball tests were conducted on the three groups of samples and the blank control (un-laser-engraved silicon nitride ceramic plate). Each test involved dropping the ball from the center point, with a hollow acrylic plate underneath. The drop ball height data are shown in Table 1. It was found that the drop ball height of the laser-engraved samples was greater than that of the un-laser-engraved silicon nitride mobile phone substrate, with the 0.5mm×0.5mm and 1×1mm groups reaching a drop ball height of 17cm. This is because in small grid cells, the crack propagation path is strictly confined to a very small area, preventing the formation of long-distance, penetrating main cracks. Crack energy is rapidly consumed, passivated, deflected, or terminated upon encountering multiple boundaries, effectively establishing a dense "firewall" for crack propagation. As the grid cell size increases, the "free region" within a single cell increases. When a crack forms, it can freely propagate a longer distance within a larger cell before encountering a boundary. During this process, the crack is more likely to accumulate energy and develop into a destructive large crack. Although the crack may eventually be prevented by the mesh boundary, it may have reached the critical size that leads to material failure during this period. Example 2 On the outer surface of a 0.5mm thick silicon nitride mobile phone back cover substrate, a large number of uniformly distributed 1×1cm grid-like groove structures were laser-engraved. The groove depths were 0.05mm, 0.1mm, and 0.25mm, respectively. Drop ball tests were then conducted on the three samples and a control group, with each drop landing on the center point, one point at a time, with a hollow acrylic plate underneath. The experiments showed that the highest drop ball height (17cm) was achieved when the engraving depth was 1 / 5 of the silicon nitride substrate depth (0.1mm). The drop ball height was 16cm when the engraving depth was 1 / 10 of the silicon nitride substrate thickness (0.05mm), and 11cm when the engraving depth was 1 / 2 of the silicon nitride substrate thickness (0.25mm). This indicates that an engraving depth of 1 / 5 of the silicon nitride substrate depth (0.1mm) achieves an optimal balance between stress dispersion, crack suppression, and structural strength, fully utilizing the impact resistance of the microgrooves without compromising the overall load-bearing capacity of the substrate.

[0020] Example 3: As demonstrated in Example 1, laser engraving on the silicon nitride mobile phone back cover substrate can effectively increase its drop height. To address the most common corner impacts and for aesthetic reasons, groove structures can be distributed in the four corner areas of the back cover. These groove structures utilize a 1×1mm mesh grid, with an engraving depth of 1 / 5 of the substrate thickness. Other areas remain untreated. Figure 2 As shown. Next, a drop ball test was conducted on the treated corner areas of the substrate, dropping a small ball at each corner with a hollow acrylic sheet underneath. The drop ball experiment revealed that the drop ball height in the blank control group was 12cm, while the drop ball height in the treated corner area reached 16cm. This indicates that the method effectively increases the drop ball height, and this structure can form the strongest "protective armor zone."

[0021] The laser engraving process described in this invention can use picosecond or femtosecond lasers. By precisely controlling the laser power, scanning speed, and defocusing amount, precise control over the engraving depth and shape can be achieved.

[0022] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A silicon nitride mobile phone back cover, characterized in that, At least four corner areas of the rear cover are laser-engraved with groove structures; the groove structures are formed by crisscrossing grooves forming a grid, and the outer contour of the enclosed area has a side length of 0.5 mm to 5 mm; the depth of the grooves is 10% to 30% of the cover thickness.

2. The silicon nitride mobile phone back cover according to claim 1, characterized in that, The groove structure covers the entire outer surface of the cover plate.

3. The silicon nitride mobile phone back cover according to claim 2, characterized in that, The distribution density of the grooves on the outer surface of the cover plate increases gradually from the center of the cover plate to the surrounding corner areas.

4. The silicon nitride mobile phone back cover according to claim 3, characterized in that, The gradient change of the distribution density is continuous and gradual.

5. The silicon nitride mobile phone back cover according to claim 1 or 2, characterized in that, The width of the groove is 10-50 micrometers.

6. The silicon nitride mobile phone back cover according to claim 1, characterized in that, The grid structure is a square grid, a rectangular grid, or a diamond grid.

7. The silicon nitride mobile phone back cover according to claim 1 or 2, characterized in that, The grooves within the same groove structure are carved to a uniform depth, or the depth of the grooves gradually decreases from the center of the enclosed area to the edge.

8. The silicon nitride mobile phone back cover according to claim 1 or 2, characterized in that, The rear cover is a pure silicon nitride cover or a composite silicon nitride ceramic cover.

Images