Silicon carbide mold as well as preparation method and application thereof

Abstract

The invention provides a silicon carbide mold as well as a preparation method and application thereof, the preparation method comprises the following steps: firstly, processing a graphite female mold in a target glass curved surface shape, then pressing silicon powder in the female mold to form a preform, carrying out sintering reaction and molten silicon permeation to obtain the silicon carbide mold, and finally polishing the surface of a cavity. The preparation method can be used for efficiently preparing the complex curved-surface silicon carbide mold, the preparation cost is low, and the prepared silicon carbide mold is long in service life and suitable for mass production of curved-surface backboard glass of smart phones.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of special mold manufacturing, in particular to a silicon carbide mold and a preparation method and application thereof. BACKGROUND

[0002] The 3D curved backplate glass of a smart phone needs to be hot-pressed at high temperature (>800℃), and the current mainstream uses graphite molds. However, the camera area is protruding due to the structure, which causes the local glass thickness to increase sharply (usually >1.5mm), and the graphite is prone to plastic deformation and wear under high pressure, with a service life of only 50-100 times, which cannot meet the mass production requirements.

[0003] To avoid this problem, existing manufacturers use the "whole thick glass CNC cutting" scheme, but the processing efficiency is low (single piece >30 minutes), the material utilization rate is <40%, and the cost is high. If SiC molds (hardness >2500HV, high-temperature strength >500MPa) are used directly, the service life problem can be solved, but SiC is extremely difficult to process: traditional bulk SiC needs diamond tooling and takes a long time to process, and the cost of a complex curved surface mold is more than 100,000 yuan per piece, and the tooling is severely worn.

[0004] CN107473574A discloses a preparation method of a curved glass panel, including panel preparation, cutting glass according to the design size, grinding and polishing, and then carving and milling into a preset size; spraying a protective layer on the carved and milled glass surface, and after the protective layer is dried, it is loaded into a forming mold; the forming of the curved glass panel, the forming mold is fixed in a hot bending protective atmosphere furnace, and is heated in three stages to soften the processed glass, and pressure is applied to the surface of the forming mold, so that the protective layer penetrates into the softened glass matrix, and is formed according to the shape of the mold under the action of pressure, and finally the curved glass panel is obtained after cooling.

[0005] CN107867793A discloses a preparation method of a curved glass cover plate, including: making a texture on a curved hot bending mold to obtain a hot bending mold with texture; providing a planar glass substrate; using the hot bending mold with texture to perform hot bending forming processing on the planar glass substrate, so that the planar glass substrate is bent into a curved glass substrate with a desired curved shape, and the texture on the hot bending mold with texture is transferred to one side of the curved glass substrate to obtain a curved glass cover plate. In the above preparation method, the texture mold and the hot bending mold are combined into one, the hot bending mold with texture is used to perform hot bending forming on the cover plate substrate, and the texture is transferred from the hot bending mold to the cover plate, which is suitable for texture making of various forms of curved substrates, does not need to design and make a single texture mold, can quickly make products, and greatly shortens the product development cycle.

[0006] CN108069583A discloses a curved glass hot bending mold, a curved glass and a preparation method thereof, and the curved glass hot bending mold, the curved glass and the preparation method thereof comprise the following steps: providing a set of molds comprising an upper mold, a mold sleeve, a lower mold, a glass blank plate and a glass rod body of the glass blank; heating the molds to make the temperature of the upper mold less than or equal to the temperature of the lower mold, and the temperature of the lower mold less than or equal to the glass transition temperature of the glass blank; after the upper mold and the mold sleeve are combined, the glass rod body in the upper and lower molds expands to hold up the glass blank, and at the same time, the glass blank is pressed on the arc surface to correct the curvature.

[0007] However, the above curved glass preparation method is not suitable for complex mobile phone back plate glass containing a camera boss structure. SUMMARY

[0008] In view of the problems in the prior art, the present application provides a silicon carbide mold and a preparation method and application thereof, which first processes a graphite master mold, then uses silicon powder to press and form a preform in the master mold, and obtains a silicon carbide mold through sintering reaction and silicon infiltration. The preparation method avoids the difficulty of direct processing of silicon carbide, can efficiently prepare a complex curved silicon carbide mold, solves the problems of high cost of traditional silicon carbide machining and short service life of graphite molds, and realizes mass production of complex mobile phone back plate glass.

[0009] To achieve this purpose, the present application adopts the following technical solutions:

[0010] In a first aspect, the present application provides a preparation method of a silicon carbide mold, which comprises the following steps:

[0011] (1) processing a graphite master mold based on the target glass curved surface shape;

[0012] (2) mixing silicon powder and a binder, then injecting the mixture into a cavity of the graphite master mold, and obtaining a silicon powder preform through cold isostatic pressing;

[0013] (3) performing sintering reaction on the silicon powder preform with a carbon-containing substance to obtain a silicon carbide mold skeleton;

[0014] (4) performing silicon infiltration on the silicon carbide mold skeleton, and obtaining a silicon carbide mold blank after cooling;

[0015] (5) performing surface finishing treatment on the silicon carbide mold blank to obtain the silicon carbide mold.

[0016] The preparation method of the silicon carbide mold has the advantages that the target glass curved surface graphite master mold is first processed according to the complex mobile phone backboard glass structure containing a camera boss structure, the camera boss, the micro-arc curved surface and other features can be accurately formed, and the precision is ±0.1 mm; then the silicon powder preform is obtained through cold isostatic pressing treatment, and the silicon carbide mold framework is obtained by sintering reaction of the carbon-containing substance and the silicon powder preform; the silicon carbide mold blank is obtained by using the silicon infiltration method; finally, the surface finishing treatment is performed, the silicon carbide mold with complex shape, low cost and long service life is obtained, and the batch hot-pressing forming of the mobile phone backboard glass containing the camera boss structure is realized.

[0017] The preparation method of the silicon carbide mold has the advantages that the target glass curved surface graphite master mold is first processed according to the complex mobile phone backboard glass structure containing a camera boss structure, the camera boss, the micro-arc curved surface and other features can be accurately formed, and the precision is ±0.1 mm; then the silicon powder preform is obtained through cold isostatic pressing treatment, and the silicon carbide mold framework is obtained by sintering reaction of the carbon-containing substance and the silicon powder preform; the silicon carbide mold blank is obtained by using the silicon infiltration method; finally, the surface finishing treatment is performed, the silicon carbide mold with complex shape, low cost and long service life is obtained, and the batch hot-pressing forming of the mobile phone backboard glass containing the camera boss structure is realized.

[0018] Preferably, the graphite master mold of step (1) comprises a camera boss structure.

[0019] Preferably, the height of the camera boss structure is 0.5-2.0 mm, for example, it can be 0.5 mm, 0.8 mm, 1.2 mm, 1.5 mm, 1.7 mm or 2.0 mm, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0020] The side wall inclination is greater than or equal to 30 degrees, for example, it can be 30 degrees, 31 degrees, 33 degrees, 35 degrees, 38 degrees or 40 degrees, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0021] The graphite master mold has a tolerance of ±0.05 mm, and graphite is easy to cut, and the cost is only 1 / 10 of the processing cost of silicon carbide.

[0022] Preferably, the purity of the silicon powder of step (2) is greater than 99.9%, for example, it can be 99.9%, 99.91%, 99.93%, 99.95%, 99.97% or 99.99%, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0023] Preferably, the particle size D50 of the silicon powder is 10~30μm, for example, it can be 10μm, 20μm, 22μm, 24μm, 26μm, 28μm or 30μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] Preferably, the adhesive comprises an aqueous solution of polyvinyl alcohol with a concentration of 8 to 10 wt%, such as 8 wt%, 8.4 wt%, 8.7 wt%, 9.1 wt%, 9.5 wt%, or 10 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0025] The present invention does not impose a detailed limitation on the mass ratio of silicon powder to binder, as long as the silicon powder preform can be obtained through cold isostatic pressing.

[0026] Preferably, the pressure of the cold isostatic pressing in step (2) is 20~80MPa, for example, it can be 20MPa, 30MPa, 40MPa, 50MPa, 70MPa or 80MPa, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] The holding time is 5 to 8 minutes, for example, it can be 5 minutes, 5.5 minutes, 6 minutes, 6.8 minutes, 7.2 minutes or 8 minutes, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] Preferably, the silicon powder preform is degreased at a temperature of 600~650℃ after demolding, for example, 600℃, 610℃, 615℃, 625℃, 638℃ or 650℃, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0029] Preferably, the carbon-containing material in step (3) includes any one of methane, propane, or solid carbon felt.

[0030] The present invention does not specify the specific process parameters for preparing silicon carbide mold skeletons by sintering carbon-containing materials and silicon powder preforms. Any sintering method feasible in the field can be used, as long as a silicon carbide mold skeleton can be prepared.

[0031] Preferably, the sintering reaction is carried out in a vacuum furnace.

[0032] Preferably, the heating rate of the sintering reaction is 10~13℃ / min, for example, it can be 10℃ / min, 10.5℃ / min, 11℃ / min, 11.6℃ / min, 12.3℃ / min or 13℃ / min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] Preferably, the sintering reaction temperature is 1450~1550℃, for example, it can be 1450℃, 1465℃, 1480℃, 1500℃, 1525℃ or 1550℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] The heat preservation time is 1~1.5h, for example, it can be 1h, 1.1h, 1.2h, 1.3h, 1.4h or 1.5h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] Preferably, the molten silicon infiltration in step (4) uses a high-purity silicon block with a purity of 95% or higher, such as 95%, 96%, 97%, 98% or 99%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] Preferably, the temperature for molten silicon infiltration is 1600~1650℃, for example, it can be 1600℃, 1605℃, 1615℃, 1625℃, 1638℃ or 1650℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0037] The time is 2 to 2.5 hours, for example, it can be 2 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours or 2.5 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] Preferably, the cooling is performed under a protective atmosphere. The protective atmosphere of this invention includes argon.

[0039] Preferably, the surface finishing process in step (5) includes sequentially grinding the cavity surface of the silicon carbide mold blank with a diamond wheel and polishing with colloidal silicon dioxide to meet the requirements of glass optical grade surface.

[0040] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0041] (1) A graphite master mold is fabricated based on the shape of the target glass surface; the graphite master mold includes a camera boss structure; the height of the camera boss structure is 0.5~2.0mm, and the side wall tilt angle is ≥30°;

[0042] (2) Silicon powder with a purity of 99.9% or higher and a particle size D50 of 10-30 μm is mixed with a binder and injected into the cavity of the graphite master mold. The mixture is then subjected to cold isostatic pressing at a pressure of 20-80 MPa and a holding time of 5-8 min to obtain a silicon powder preform. After demolding, the silicon powder preform is degreased at a temperature of 600-650℃. The binder comprises a polyvinyl alcohol aqueous solution with a concentration of 8-10 wt%.

[0043] (3) A silicon carbide mold skeleton is obtained by sintering carbon-containing material and silicon powder preform in a vacuum furnace at a heating rate of 10~13℃ / min, a temperature of 1450~1550℃, and a holding time of 1~1.5h; the carbon-containing material includes any one of methane, propane or solid carbon felt.

[0044] (4) The silicon carbide mold skeleton is subjected to molten silicon infiltration at a temperature of 1600~1650℃ for 2~2.5h, and then cooled under a protective atmosphere to obtain a silicon carbide mold blank; the molten silicon infiltration uses high-purity silicon blocks with a purity of 95% or higher.

[0045] (5) The cavity surface of the silicon carbide mold blank is successively subjected to diamond wheel grinding and colloidal silicon dioxide polishing to obtain the silicon carbide mold.

[0046] Secondly, the present invention also provides a silicon carbide mold prepared using the silicon carbide mold preparation method described in the first aspect, wherein the surface roughness Ra of the cavity of the silicon carbide mold is ≤0.1μm; and the density of the silicon carbide mold is ≥2.9g / cm³. 3 .

[0047] The silicon carbide mold described in this invention has low manufacturing cost, long service life, and can be applied to the batch hot pressing of mobile phone back panel glass with complex shapes and camera bump structures. The resulting mobile phone back panel glass is free of cracks and optical distortion, and the camera step area has a clear outline.

[0048] The surface roughness Ra of the silicon carbide mold cavity described in this invention is ≤0.1μm, for example, it can be 0.1μm, 0.09μm, 0.08μm, 0.05μm, 0.04μm or 0.02μm, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0049] The density of the silicon carbide mold is ≥2.9 g / cm³. 3 For example, it could be 2.9 g / cm³. 3 3g / cm 3 3.2g / cm 3 3.5g / cm 3 3.8g / cm3 or 4g / cm 3 This applies to, but is not limited to, the listed values; other unlisted values ​​within this range also apply.

[0050] Thirdly, the present invention also provides an application of the silicon carbide mold as described in the second aspect, the silicon carbide mold being used to prepare 3D curved back glass for smartphones.

[0051] Preferably, the silicon carbide mold is used to prepare the 3D curved back panel glass of the smartphone at a temperature of 800~950℃ and a pressure of 10~20MPa.

[0052] The silicon carbide mold described in this invention can be used for hot pressing to prepare 3D curved back glass for smartphones, with high glass yield and clear contours in the camera step area, meeting usage requirements.

[0053] The temperature described in this invention is 800~950℃, for example, it can be 800℃, 825℃, 850℃, 880℃, 920℃ or 950℃, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0054] The pressure is 10~20MPa, for example, it can be 10MPa, 12MPa, 14MPa, 16MPa, 18MPa or 20MPa, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0055] Compared with the prior art, the present invention has at least the following beneficial effects:

[0056] (1) The method for preparing silicon carbide molds provided by the present invention first prepares a graphite master mold that conforms to the shape of the target glass surface, and then prepares a silicon carbide mold. The graphite master mold can be reused, and the direct processing of bulk silicon carbide is avoided, which can reduce the preparation cost by 90%.

[0057] (2) The silicon carbide mold provided by this invention can accurately form features such as mobile phone camera protrusions and micro-arc curved surfaces with an accuracy of ±0.1mm, and can perfectly replicate complex structures:

[0058] (3) The silicon carbide mold provided by the present invention has a heat-resistant pressing cycle of >1000 times, which is 10 times longer than the heat-resistant pressing cycle of existing graphite molds of <100 times.

[0059] (4) The coefficient of thermal expansion of the silicon carbide mold provided by the present invention is 4.5 × 10⁻⁶. -6 / ℃, matching the glass, reduces thermal stress cracking, and the hot pressing yield is >95%. Attached Figure Description

[0060] Figure 1 This is a partially enlarged view of the silicon carbide mold prepared in Example 1. Detailed Implementation

[0061] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0062] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0063] The following examples use ISO-68 grade isostatically pressed graphite with a density of 1.85 g / cm³. 3 The target glass surface shape, including the camera protrusion area, is sculpted using computer numerical control (CNC engraving) with a surface Ra=0.4μm.

[0064] Example 1

[0065] This embodiment provides a method for preparing a silicon carbide mold, the method comprising the following steps:

[0066] (1) A graphite master mold is fabricated based on the shape of the target glass surface; the graphite master mold includes a camera boss structure; the height of the camera boss structure is 1mm and the side wall tilt angle is 35°;

[0067] (2) Silicon powder with a purity of 99.9% and a particle size D50 of 20 μm is mixed with a binder and injected into the cavity of the graphite master mold. The mixture is then subjected to cold isostatic pressing at a pressure of 80 MPa for a holding time of 5 min to obtain a silicon powder preform. After demolding, the silicon powder preform is degreased at a temperature of 600 °C. The binder comprises an aqueous solution of polyvinyl alcohol with a concentration of 8 wt%.

[0068] (3) A silicon carbide mold skeleton is obtained by sintering carbon-containing material and silicon powder preform in a vacuum furnace at a heating rate of 10℃ / min, a temperature of 1500℃, and a holding time of 1h; the carbon-containing material is a mixture of CH4 and H2 in a volume ratio of 1:4.

[0069] (4) The silicon carbide mold skeleton is subjected to molten silicon infiltration at a temperature of 1620℃ for 2 hours, and then cooled under a protective atmosphere to obtain a silicon carbide mold blank; the molten silicon infiltration uses a high-purity silicon block with a purity of 95% and an excess of 30 wt%;

[0070] (5) The cavity surface of the silicon carbide mold blank is successively ground with diamond wheel and polished with colloidal silicon dioxide to obtain a silicon carbide mold with Ra=0.08μm.

[0071] A partially enlarged view of the silicon carbide mold prepared in this embodiment is shown below. Figure 1 As shown in the figure, the molten silicon in the silicon carbide mold fully fills the porous structure.

[0072] Example 2

[0073] This embodiment provides a method for preparing a silicon carbide mold, the method comprising the following steps:

[0074] (1) A graphite master mold is fabricated based on the shape of the target glass surface; the graphite master mold includes a camera boss structure; the height of the camera boss structure is 0.5 mm and the side wall tilt angle is 30°;

[0075] (2) Silicon powder with a purity of 99.93% and a particle size D50 of 30 μm is mixed with a binder and injected into the cavity of the graphite master mold. The mixture is then subjected to cold isostatic pressing at a pressure of 20 MPa and a holding time of 8 min to obtain a silicon powder preform. After demolding, the silicon powder preform is degreased at a temperature of 650°C. The binder comprises a polyvinyl alcohol aqueous solution with a concentration of 10 wt%.

[0076] (3) A silicon carbide mold skeleton is obtained by sintering a carbon-containing material and a silicon powder preform in a vacuum furnace at a heating rate of 13℃ / min, a temperature of 1550℃, and a holding time of 1.5h; the carbon-containing material is propane.

[0077] (4) The silicon carbide mold skeleton is subjected to molten silicon infiltration at a temperature of 1600℃ for 2.5h, and then cooled under a protective atmosphere to obtain a silicon carbide mold blank; the molten silicon infiltration uses a high-purity silicon block with a purity of 97% and an excess of 30wt%;

[0078] (5) The cavity surface of the silicon carbide mold blank is successively ground with diamond wheel and polished with colloidal silicon dioxide to obtain a silicon carbide mold with Ra=0.05μm.

[0079] Example 3

[0080] This embodiment provides a method for preparing a silicon carbide mold, the method comprising the following steps:

[0081] (1) A graphite master mold is fabricated based on the curved shape of the target glass surface; the graphite master mold includes a camera boss structure; the height of the camera boss structure is 2mm and the side wall tilt angle is 38°;

[0082] (2) Silicon powder with a purity of 99.95% and a particle size D50 of 10 μm is mixed with a binder and injected into the cavity of the graphite master mold. The mixture is then subjected to cold isostatic pressing at a pressure of 50 MPa and a holding time of 5.8 min to obtain a silicon powder preform. After demolding, the silicon powder preform is degreased at a temperature of 620°C. The binder comprises a polyvinyl alcohol aqueous solution with a concentration of 9 wt%.

[0083] (3) A silicon carbide mold skeleton is obtained by sintering carbon-containing material and silicon powder preform in a vacuum furnace at a heating rate of 12℃ / min, a temperature of 1450℃, and a holding time of 1.2h; the carbon-containing material is methane.

[0084] (4) The silicon carbide mold skeleton is subjected to molten silicon infiltration at a temperature of 1650℃ for 2.3h, and then cooled under a protective atmosphere to obtain a silicon carbide mold blank; the molten silicon infiltration uses a high-purity silicon block with a purity of 95.7% and an excess of 30wt%;

[0085] (5) The cavity surface of the silicon carbide mold blank is successively ground with diamond wheel and polished with colloidal silicon dioxide to obtain a silicon carbide mold with Ra=0.057μm.

[0086] Hot pressing tests were conducted on the silicon carbide molds prepared in Examples 1-3, and the results showed that the hot pressing cycle resistance was >1000 cycles and the hot pressing yield was >95%. After 1200 cycles of continuous hot pressing of the glass prepared by the above silicon carbide molds at 900℃ and 15MPa, the cavity size change was <0.01mm; the glass had no cracks or optical distortion, and the outline of the camera step area was clear.

[0087] As can be seen from Examples 1-3, the silicon carbide mold preparation method provided by the present invention can prepare high-quality silicon carbide molds with a cavity surface roughness Ra≤0.1μm, and can accurately form features such as mobile phone camera protrusions and micro-arc curved surfaces. The preparation cost is low, the mold has a long service life, and it is suitable for mass hot pressing of 3D curved back glass for smartphones.

[0088] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a silicon carbide mold, characterized in that, The preparation method includes the following steps: (1) Fabricate a graphite master mold based on the shape of the target glass surface; (2) After mixing silicon powder with binder, the mixture is injected into the cavity of the graphite master mold and subjected to cold isostatic pressing to obtain silicon powder preform; (3) A silicon carbide mold skeleton is obtained by sintering carbon-containing materials with silicon powder preforms. (4) The silicon carbide mold skeleton is subjected to molten silicon infiltration and cooled to obtain a silicon carbide mold blank; (5) The silicon carbide mold blank is subjected to surface finishing treatment to obtain the silicon carbide mold.

2. The preparation method according to claim 1, characterized in that, The graphite master mold in step (1) includes a camera boss structure; Preferably, the height of the camera boss structure is 0.5~2.0mm, and the side wall tilt angle is ≥30°.

3. The preparation method according to claim 1 or 2, characterized in that, The purity of the silicon powder mentioned in step (2) is above 99.9%; Preferably, the particle size D50 of the silicon powder is 10~30μm; Preferably, the adhesive comprises an aqueous solution of polyvinyl alcohol with a concentration of 8-10 wt%.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The pressure of the cold isostatic pressing process in step (2) is 20~80MPa, and the holding time is 5~8min; Preferably, the silicon powder preform is degreased at a temperature of 600~650℃ after demolding.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The carbon-containing material mentioned in step (3) includes any one of methane, propane, or solid carbon felt; Preferably, the sintering reaction is carried out in a vacuum furnace; Preferably, the heating rate of the sintering reaction is 10~13℃ / min; Preferably, the sintering reaction temperature is 1450~1550℃, and the holding time is 1~1.5h.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The molten silicon infiltration in step (4) uses high-purity silicon blocks with a purity of 95% or higher; Preferably, the temperature for molten silicon infiltration is 1600~1650℃, and the time is 2~2.5h; Preferably, the cooling is performed under a protective atmosphere.

7. The preparation method according to any one of claims 1 to 6, characterized in that, The surface finishing process in step (5) includes sequentially grinding the cavity surface of the silicon carbide mold blank with diamond wheel and polishing with colloidal silicon dioxide.

8. A silicon carbide mold prepared by the method for preparing a silicon carbide mold according to any one of claims 1 to 7, characterized in that, The surface roughness Ra of the silicon carbide mold cavity is ≤0.1μm; the density of the silicon carbide mold is ≥2.9g / cm³. 3 .

9. An application of the silicon carbide mold as described in claim 8, characterized in that, The silicon carbide mold is used to prepare 3D curved back glass for smartphones.

10. The application according to claim 9, characterized in that, Using the silicon carbide mold, 3D curved back glass for smartphones is prepared at a temperature of 800~950℃ and a pressure of 10~20MPa.

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