A sapphire window suitable for extreme environments and a method of making the same

Abstract

The application relates to the technical field of sapphire processing, and provides a sapphire window suitable for extreme environments and a preparation method thereof. The preparation method is simple, economical and environment-friendly, and comprises the processes of crystal orientation, cutting, plane grinding, shape processing, fine grinding and polishing and the like. The 0.25-0.5mm large-removal-amount plane grinding process is matched with the 50um or more large-removal-amount fine grinding process, the sub-surface damage layer is effectively eliminated, and an excellent polishing surface foundation is provided; then, the 150-200kg heavy pressure is matched with the damping cloth and the nano silicon oxide to continuously polish, the sub-surface damage of the previous process is further removed, the surface roughness is reduced to <0.2nm, the steps are synergistically combined, the sapphire window surface quality is effectively improved, and the obtained sapphire window product can be applied to the extreme environment application fields such as deep sea and spaceflight.

Description

Technical Field

[0001] This invention belongs to the field of sapphire processing technology, specifically relating to a sapphire window suitable for extreme environments and its preparation method. Background Technology

[0002] As an optical functional component, the primary function of a viewing window is to allow light, laser, or visual signals to pass through without damage while isolating it from harsh environments such as dust, moisture, high pressure, chemical corrosion, or extreme temperatures, thus enabling core functions such as observation, monitoring, sensing, or communication. Common viewing window materials include ordinary glass, quartz glass, and polycarbonate engineering plastics. Ordinary glass is inexpensive but easily scratched, quartz glass is heat-resistant but lacks hardness, and polycarbonate engineering plastics are tough but have poor stability.

[0003] Modern technological demands are placing increasingly stringent requirements on the performance of window materials in extreme environments. Sapphire windows, with their ultra-high hardness, high light transmittance, and excellent chemical stability, maintain stable optical performance even under extreme conditions such as high temperature, high pressure, high vacuum, and strong corrosion. They are widely used in critical fields requiring light transmission, observation, sealing, or protection, covering high-end applications from consumer electronics to military technology. However, applications in extreme high-pressure environments such as deep-sea observation, vacuum coating, semiconductor equipment, aerospace engineering, and high-pressure reactors place very high demands on the subsurface damage (SSD) of sapphire windows. Due to the ultra-high hardness of sapphire and its complex processing techniques, the processed surface is prone to residual subsurface damage, making it difficult to meet the application requirements of extreme environments such as deep sea and aerospace. Therefore, exploring efficient and low-cost sapphire window fabrication technologies, improving the surface processing quality of sapphire windows, and reducing subsurface damage to specific requirements, achieving a roughness of <0.2nm, to meet the needs of applications in more extreme environments, is an urgent problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing sapphire window technologies where the surface quality cannot meet the requirements of extreme environment applications, and to provide a sapphire window suitable for extreme environments and its preparation method. This preparation method can effectively remove subsurface damage generated during the sapphire window preparation process, achieving a surface roughness of <0.2 nm, while reducing processing steps and significantly shortening processing time, thereby reducing processing costs; the resulting sapphire window meets the requirements for use in extreme environments.

[0005] A method for fabricating a sapphire window suitable for extreme environments includes the following steps:

[0006] S1. Orientation: Place the C-axis sapphire ingot on the orientation platform of the 8BD orienter, use the 8BD orienter to determine the C-axis direction of the ingot, and mark the vertical cutting position to ensure that the deviation between the cutting direction and the C-axis crystal orientation is controlled within ±1°.

[0007] S2. Cutting: Place the C-oriented ingot after orientation on the single-wire cutting machine platform and use the single-wire cutting machine to cut vertically. Cut multiple blank crystal plates in sequence according to the final required thickness of the sapphire window product. Continue to use the single-wire cutting machine to cut the blank crystal plates into blank windows of the target shape.

[0008] S3. Surface grinding: Fix the blank viewing window on the surface grinding machine platform and grind the two surfaces using the surface grinding machine. Preferably, the removal amount on one side is 0.25~0.5mm and the parallelism is ≤0.01mm. This step uses a surface grinding machine for rough processing to remove surface cutting marks and achieve thickness control.

[0009] S4. External Shape Machining: Fix the blank window machined by the surface grinder onto the machining center, and use the machining center machine tool to machine the external shape.

[0010] S5. Fine Grinding: Use a single-axis machine to fine grind the front and back of the blank window. Preferably, the single-axis machine disc is made of marble, and the marble disc is covered with composite material abrasive cloth. The abrasive liquid in the single-axis machine tank is agglomerated 1.5μm diamond liquid, and the single-sided removal amount is ≥50μm. This step uses small-particle diamond liquid for surface fine grinding to increase the single-sided removal amount and ensure the removal of subsurface damage generated in the previous process, providing a good surface foundation for subsequent polishing.

[0011] S6. Polishing: Polish the front and back of the blank window using a single-axis machine. Preferably, the single-axis machine disc is made of marble with black damping cloth attached. The polishing fluid in the single-axis machine tank is 80~120nm silicon dioxide polishing fluid, the pressure is 150kg~200kg, and the single-sided removal amount is ≥5μm. The obtained sapphire window sheet is inspected for surface defects according to GB / T 1185-2006 to ensure that it meets the requirement of B / 2X0.16. This step uses nano-silicon dioxide polishing fluid to ensure the removal of subsurface damage from the previous process, so that its roughness is <0.2nm, which meets the requirements of use in extreme environments.

[0012] In S1, preferably, a 400-800 kg C-oriented sapphire ingot is grown using the modified KY method. Specific growth steps can be found in patent CN103103604B. The resulting sapphire ingot exhibits no obvious defects upon visual inspection, with few bubbles and low stress. Testing confirms it meets the following requirements: low dislocation density (≤1000 ps / cm²). 2 ), with good single crystal properties (≤15 arcseconds).

[0013] In S2, preferably, the diamond wire used in the cutting machine is φ0.15~0.37mm with a particle size of 45~55μm; the coolant in the cutting machine's water tank is a water-based cutting fluid; the diamond wire tension is 50~60N; the tension slope is 4~5N / s; the wire speed is 7~8m / s; the feed rate is 1~2mm / min; and the swing axis amplitude is 14~25mm. The raw crystal plate must meet the following requirements: no bubbles, no stress, and purity ≥99.999%.

[0014] In S3, preferably, the surface grinding wheel is a 170-mesh sintered grinding wheel, the coolant in the surface grinder's water tank is a water-based cutting fluid, the grinding wheel spindle speed is 1500~1800 rpm, and the feed rate is 0.02~0.06 mm / min.

[0015] In S4, preferably, the grinding wheel and electroplating wheel of the machining center are 600 mesh, the coolant in the water tank of the machining center is water-based cutting fluid, the spindle speed of the machining center is 700~800 rpm, and the side dimensions of the blank viewing window are machined and protective chamfered to ensure that C≤0.3mm.

[0016] In S5, the grinding fluid flow rate is 10ml / min, the spindle speed is 15~20rpm, the swing shaft speed is 20~25rpm, and the single-sided processing time is 3~4h.

[0017] In S6, the spindle speed is 25~30 rpm, the swing shaft speed is 15~20 rpm, and the single-sided machining time is 6~8 hours.

[0018] By adopting the above technical solution, this invention uses 600~800KG C-oriented sapphire ingots grown by the modified KY method to prepare sapphire windows through processes such as orientation, cutting, surface grinding, shape processing, fine grinding and polishing. This effectively removes subsurface damage, achieves a roughness of <0.2nm, improves the surface quality of the product, and is suitable for extreme environment applications such as deep sea and aerospace.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention uses a coarse grinding process with a large removal amount of 0.25~0.5mm combined with a fine grinding process with a deep removal of more than 50μm to effectively eliminate the subsurface damage layer and provide a good polishing surface foundation; then, combined with a heavy pressure of 150~200kg, damping cloth and nano-silica for continuous polishing, the subsurface damage of the previous process is further removed, and the surface roughness is reduced to <0.2nm. The synergistic effect of each step achieves ultra-low surface roughness and excellent surface quality suitable for extreme environments. (2) Compared with traditional processing technology, the technical solution of the present invention has a significant improvement effect on removing subsurface damage of sapphire windows, and can effectively ensure that the surface roughness of sapphire parts is better, so as to meet the requirements of extreme environment use. (3) The technical solution of the present invention reduces the multiple boron carbide grinding processes in the conventional sapphire processing process, and does not use irritating chemical reagents such as concentrated phosphoric acid and hydrofluoric acid to remove the damaged layer through corrosion. The process is simpler, more economical, safer and more environmentally friendly. Attached Figure Description

[0020] Figure 1 This is a flowchart of the sapphire window fabrication method of the present invention;

[0021] Figure 2 This is a schematic diagram of the sapphire blank viewing window clamping planar fixture structure of the present invention, wherein: 1-porous resin plate, 2-damping cloth, 3-aluminum alloy plate, 4-transfer flange, 5-cavity, 6-positioning hole. Detailed Implementation

[0022] Example 1 This embodiment 1 provides a sapphire window suitable for extreme environments. The raw material for the sapphire window wafer is preferably a 400KG C-oriented sapphire ingot grown by the modified KY method. The ingot selection meets the following criteria: low bubble content, low stress, purity ≥99.999%, and dislocation density ≤1000pc / cm². 2 The monocrystalline property measured by XRD is ≤15 arcseconds.

[0023] Methods for fabricating sapphire windows suitable for extreme environments, such as... Figure 1 As shown, the specific steps are as follows:

[0024] S1. Orientation: Place the C-oriented sapphire ingot on the orientation platform of the 8BD orienter, use the 8BD orienter to determine the crystal axis direction of the ingot, mark the vertical cutting position, control the deviation between the cutting direction and the C-oriented crystal direction within ±1°, and attach it to the iron plate.

[0025] S2. Cutting: After orientation, the ingot is placed on a single-wire dicing machine platform. Using the single-wire dicing machine, the ingot is vertically cut into two parts. Then, according to the final required sapphire window thickness, multiple blank crystal plates are cut out sequentially. The thickness of each blank crystal plate is 31.2±0.1mm. A laser pointer is used to detect the air bubbles inside the blank crystal plates. Areas without air bubbles and without stress are selected to cut out 82mm*82mm blank windows. Preferably, the diamond wire of the dicing machine is φ0.37mm with a particle size of 45~55μm. The coolant in the dicing machine's water tank is water-based cutting fluid. The diamond wire tension is 60N, the tension slope is 5N / s, the wire speed is 8m / s, the feed rate is 2mm / min, and the swing axis amplitude is 20mm.

[0026] S3. Surface Grinding: Fix the cut blank onto the surface grinding machine platform and grind the two surfaces using the surface grinding machine, controlling the thickness to 30.2mm ± 0.1mm; preferably, the surface grinding wheel is a 170-mesh sintered grinding wheel, the coolant in the surface grinding machine water tank is a water-based cutting fluid, the grinding wheel spindle speed is 1800rpm, the feed rate is 0.04mm / min, the single-sided removal amount is 0.5mm, and the parallelism is ≤0.01mm.

[0027] S4. External Machining: Fix the blank window machined on the surface grinder onto the machining center. Using the machining center, machine the side dimensions of the blank window to D81±0.1mm*T30.2mm±0.1mm and perform a protective chamfer to ensure C≤0.3mm. Preferably: the grinding wheel and electroplated abrasive wheel of the machining center are 600 grit, the coolant in the machining center's water tank is water-based cutting fluid, and the spindle speed of the machining center is 800 rpm.

[0028] S5. Fine Grinding: The front and back sides of the sapphire blank window are finely ground using a single-axis machine. First, the blank window with dimensions D81±0.1mm*T30.2mm±0.1mm is placed in the cavity 5 of the flat fixture. Preferably, as follows: Figure 2 As shown, the fixture is made of porous resin and aluminum alloy, with dimensions of D600mm*T40mm. The fixture consists of three layers: a porous resin plate 1, a 0.5mm thick damping cloth 2, and an aluminum alloy plate 3. The damping cloth 2 is adhered to the front of the aluminum alloy plate 3. Then, the porous resin plate 1 is fixed to the front of the aluminum alloy plate 3 through three positioning holes 6. An adapter flange 4 is fitted to the center of the back of the aluminum alloy plate 3, which works in conjunction with the single-axis machine's ejector pin. Compared to traditional wax bonding processes, this fixture is simpler to place and remove, and is quicker and easier to operate. Preferably, the single-axis machine has a marble disc surface covered with composite material abrasive cloth. The abrasive fluid in the single-axis machine's tank is agglomerated 1.5μm diamond slurry with a flow rate of 10ml / min. The spindle speed is 15rpm, the swing shaft speed is 20rpm, the pressure is 200kg, the single-sided removal amount is 50μm, and the single-sided processing time is 4 hours.

[0029] S6. Polishing: Polish both sides of the sapphire blank window sheet using a single-axis machine. Preferably, the single-axis machine disc is made of marble with damping cloth attached. The polishing fluid in the single-axis machine tank is 80nm silica polishing fluid. The spindle speed is 25rpm, the swing shaft speed is 20rpm, the pressure is 150kg, the single-sided removal amount is 10μm, and the single-sided processing time is 6h. The resulting sapphire window sheet product is inspected for surface defects according to GB / T 1185-2006: the product is qualified. The performance indicators of the obtained sapphire window are detailed in Table 1.

[0030] Example 2 The method is the same as in Example 1, except that the pressure during the S6 polishing process is 200 kg. The performance indicators of the resulting sapphire window are detailed in Table 1.

[0031] Comparative Example 1 Referring to the method of Example 1, the difference is that the pressure of the S6 polishing process was set to 50 kg and 100 kg respectively, and the performance indicators of the resulting sapphire window are detailed in Table 1.

[0032] Comparative Example 2 Referring to the method of Example 1, except that the polishing cloth damping pad is replaced with polyurethane polishing cloth, and the polishing process pressure is set to 50kg, 100kg, 150kg and 200kg respectively. The performance indicators of the obtained sapphire window are detailed in Table 1.

[0033] Comparative Example 3 The method is the same as in Example 1, except that the polishing time is shortened to 5 hours and 4 hours respectively. The performance indicators of the resulting sapphire window are detailed in Table 1.

[0034] Table 1. Process and performance of sapphire windows obtained in Examples 1-2 and Comparative Examples 1-3 Note: In the table, OK indicates that the surface defects meet the requirements of B / 2X0.16; NG indicates that they do not meet the requirements.

[0035] Comparative Example 4 Referring to the method in Example 1, the difference is that a traditional polishing process is used, that is, the polishing equipment is changed to a ring polisher, the polishing disc is changed to an asphalt polishing disc, and the polishing fluid in the ring polisher tank is 1μm alumina polishing fluid. The performance indicators of the obtained sapphire window are detailed in Table 2.

[0036] Table 2. Process and sapphire window properties of Example 1 and Comparative Example 4 Note: In the table, OK indicates that the surface defects meet the requirements of B / 2X0.16; NG indicates that they do not meet the requirements.

[0037] As can be seen from the above embodiments and comparative examples, the technical solution of the present invention can ensure that the surface quality of the obtained sapphire window wafer meets the technical requirements, with a surface roughness Ra < 0.2 nm, satisfying the application needs in extreme environments. Simultaneously, the polishing time is shortened by 106 hours compared to the polishing time of traditional ring polishing equipment, significantly reducing processing costs. Without the specific method of the present invention, the surface quality and surface roughness of the sapphire window wafer cannot meet the application requirements in extreme environments, or the polishing time is excessively long.

Claims

1. A method for fabricating a sapphire window suitable for extreme environments, characterized in that, Includes the following steps: S1. Orientation: Determine the C-axis direction of the sapphire ingot, mark the cutting position, and ensure that the angle deviation between the cutting direction and the C-axis is within ±1°. S2. Cutting: The sapphire ingot is cut using diamond wire to obtain a rough viewing window; S3. Surface grinding: Use a surface grinder to perform double-sided rough grinding on the blank viewing window, with a single-sided removal amount of 0.25~0.5mm and a parallelism of ≤0.01mm; S4. External machining: The external shape of the blank window after surface grinding is machined. S5. Fine grinding: The blank window after the outer shape is processed is finely ground on both sides using a single-axis machine. Composite material abrasive cloth is used in combination with 1.5μm agglomerated diamond liquid as abrasive liquid, and the single-sided removal amount is ≥50μm. S6. Polishing: The finely ground window is polished on both sides using a single-axis machine. Damping cloth is used in conjunction with nano-silica polishing slurry. The polishing pressure is 150~200kg, the polishing time on one side is 6~8h, and the removal amount on one side is ≥5μm, so that the surface roughness of the obtained sapphire window is <0.2nm.

2. The method for preparing a sapphire window suitable for extreme environments as described in claim 1, characterized in that, In S1, the ingot is a C-oriented sapphire ingot grown using the modified KY method, with a dislocation density ≤1000 ps / cm². 2 The monocrystalline property measured by XRD is ≤15 arcseconds.

3. The method for preparing a sapphire window suitable for extreme environments as described in claim 1, characterized in that, In step S2, the crystal ingot is first cut to obtain a blank crystal plate. The blank crystal plate with no bubbles, no stress, and a purity of ≥99.999% is selected and cut again to obtain a blank viewing window.

4. The method for preparing a sapphire window suitable for extreme environments as described in claim 1 or 3, characterized in that, In S2, the diamond wire has a diameter of φ0.15~0.37mm, a particle size of 45~55μm, a tension of 50~60N, a tension slope of 4~5N / s, a wire speed of 7~8m / s, a feed speed of 1~2mm / min, and a swing axis amplitude of 14~25mm.

5. The method for preparing a sapphire window suitable for extreme environments as described in claim 1, characterized in that, In S3, the surface grinder uses a 170-mesh sintered grinding wheel, with a grinding wheel spindle speed of 1500~1800 rpm and a feed rate of 0.02~0.06 mm / min.

6. The method for preparing a sapphire window suitable for extreme environments as described in claim 1, characterized in that, In S4, both the grinding wheel and the electroplated abrasive wheel of the machining center are 600 mesh, and the spindle speed of the machining center is 700~800 rpm; the outer shape is chamfered to ensure that C≤0.3mm.

7. The method for preparing a sapphire window suitable for extreme environments as described in claim 1, characterized in that, In S5, the single-axis machine disc is made of marble, and the marble disc is covered with composite material abrasive cloth. The abrasive fluid flow rate is 10ml / min, the spindle speed is 15~20rpm, the swing shaft speed is 20~25rpm, and the single-sided processing time is 3~4 hours.

8. The method for preparing a sapphire window suitable for extreme environments as described in claim 1, characterized in that, In S6, the nano-silica particle size is 80~120nm, the spindle speed is 25~30rpm, the swing shaft speed is 15~20rpm, and the single-sided processing time is 6~8 hours.

9. The method for preparing a sapphire window suitable for extreme environments as described in claim 1, characterized in that, In S5 and S6, the blank window is placed into the cavity (5) of the planar fixture, wherein the planar fixture consists of three layers in sequence: a porous resin plate (1), a damping cloth (2), and an aluminum alloy plate (3).

10. A sapphire window suitable for extreme environments, characterized in that, It is prepared using the method for preparing sapphire windows suitable for extreme environments as described in any one of claims 1 to 9.

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