A bonding paste for a crystal and a bonding method and application

Abstract

This invention relates to a bonding paste for crystals, a bonding method, and applications of the bonding method. The bonding paste is formed from the following powders in a specified percentage ratio: SiO₂ 2 20-60%, Al 2 O 3 :30‑45%, MgO: 0‑8%, CaF 2 0-3%, Na 2 O: 0-10%, K 2 O: 0-10%, B 2 O 3 The bonding method includes steps such as synthesizing a bonding slurry for the crystals, applying pressure and bonding, and high-temperature treatment. This invention, by adjusting the proportions of the slurry components and the temperature regime, forms a micrometer-scale glass transition interface between crystals. Compared to high-temperature bonding processes, this invention can achieve bonding between crystal atoms at temperatures far below the crystal's melting point, with strong bonding forces, a smooth and transparent interface, and no cloudiness at the interface. This method greatly simplifies the traditional high-temperature, high-pressure bonding process and significantly improves the yield.

Description

A bonding paste for crystals, a bonding method, and its application. Technical Field

[0001] This invention belongs to the field of crystal bonding technology, and relates to a crystal bonding paste and its bonding method, as well as the application of the bonding method. Background Technology

[0002] Crystal bonding technology involves directly bonding homogeneous or heterogeneous crystals with clean surfaces and atomic-level roughness to form a single unit under certain conditions, with the crystal wafers linked together by chemical bonds. This technology offers significant advantages over adhesive bonding, as it can produce bonded crystal materials with smooth, flat interfaces and optical transparency. This is of great importance for solving problems related to heat dissipation, light guiding, and other innovative applications of crystals.

[0003] Bonding is a complex process. Since most optical crystals have very high melting points, traditional bonding processes require high-temperature heat treatment near their melting points, while applying pressure to the contact surface to induce surface atoms of the two crystals to diffuse and fuse, ultimately forming stable chemical bonds. This process is clearly demanding because: 1. Bonding must be performed at temperatures close to the crystal's melting point, which is often very high. Higher temperatures, higher pressures, and longer periods of high temperature require more sophisticated equipment and consume more energy. 2. The crystal surface needs to achieve atomic-level flatness, generally better than 2 nm, while also requiring a small bonding contact cross-section and avoiding excessively large wedge angles. Bonding success rates are very low for crystals with wedge angles or excessive surface roughness. 3. When using traditional high-temperature, high-pressure processes to bond two different crystalline materials, significant lattice mismatch and other defects can lead to numerous dislocations and other defects at the bonding surface, affecting the bonding effect and even causing bonding failure. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned defects of the prior art and provide a crystal bonding paste and bonding method that can form a micron-level glass transition interface between crystals. The bonding method has mild conditions, low requirements for the flatness of the bonding surface, and effectively realizes bonding between dissimilar crystals.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: a bonding paste for crystals, wherein the bonding paste is formed by mixing the following powders in the following percentages: SiO2: 20-60%, Al2O3: 30-45%, MgO: 0-8%, CaF2: 0-3%, Na2O: 0-10%, K2O: 0-10%, B2O3: 0-10%, wherein the powders are ball-milled with anhydrous ethanol to form a paste, i.e., the bonding paste.

[0006] Preferably, the bonding slurry is formed by mixing the following powders in the following percentages: SiO2: 30-35%, Al2O3: 30-45%, MgO: 2-8%, CaF2: 0-3%, Na2O: 0-10%, K2O: 0-10%, B2O3: 2-10%. The powders are ball-milled with anhydrous ethanol to form a paste, which is the bonding slurry.

[0007] This invention also provides a method for bonding crystals, the method comprising the following steps: 1) synthesizing a bonding slurry, which is formed by mixing the following powders in a certain percentage: SiO2: 20-60%, Al2O3: 30-45%, MgO: 0-8%, CaF2: 0-3%, Na2O: 0-10%, K2O: 0-10%, B2O3: 0-10%, the powders are ball-milled with anhydrous ethanol to form a paste, i.e., the bonding slurry; 2) pressing and bonding: the bonding slurry is diluted and uniformly coated or sprayed onto the surface of the crystal to be bonded, and the crystal is fixed with a jig for bonding; 3) high-temperature heat treatment: the bonded crystal is transferred into a high-temperature furnace for high-temperature sintering, and then cooled to room temperature before being removed.

[0008] Preferably, the crystal includes, but is not limited to, sapphire crystal, YAG system crystal, and spinel system crystal.

[0009] Preferably, the crystal refers to a sapphire crystal.

[0010] Preferably, the slurry dilution in step 2) refers to dilution with any one of anhydrous ethanol, distilled water, deionized water, or acetone. During dilution, the mixture is stirred at a speed of 100-400 rpm for 20 minutes.

[0011] Preferably, the pressure range for bonding in step 2) is 10-30 kg / cm. 2 The bonding and pressure holding time is 1.0-3.0 hours.

[0012] Preferably, the high-temperature sintering in step 3) includes vacuum sintering, atmosphere sintering, and hot pressing sintering.

[0013] Preferably, the temperature range of the high-temperature sintering in step 3 is 900-1500℃, and after reaching the temperature range, it is held at that temperature for 2-4 hours.

[0014] Preferably, the heat preservation time in step 3 is 3 hours.

[0015] Preferably, the cooling process in step 3) involves lowering the temperature from the high-temperature sintering temperature to 300°C at a rate of 0.2-0.5°C / min. After maintaining the temperature at 300°C for 24 hours, the cooling rate is reduced to 0.5-5°C / min until the temperature reaches room temperature. This cooling process effectively releases the stress between the interfaces, preventing cracks and scattering centers from forming at the interfaces, and also facilitates the removal of pores between the liquid glass particles.

[0016] The bonding method of this invention refers to the formation of chemical bonds such as Al-O and YO between the slurry and the crystals on both sides after the slurry melts into a transparent glass interface at high temperature. By adjusting the ratio of slurry components and controlling the temperature program, a micron-scale glass transition interface is formed between the crystals. Compared with high-temperature bonding processes, this invention can achieve bonding between crystal atoms at temperatures far below the crystal melting point, with strong bonding forces, a smooth and transparent interface, and no cloudiness at the interface. Actual testing showed that the crystals bonded by this invention, after 200 days of immersion testing and 100 cycles of thermal cycling at 25-500℃, showed no cracks or damage on the bonding surface. This invention greatly simplifies the traditional high-temperature and high-pressure bonding process and significantly improves the yield.

[0017] The beneficial effects of this invention are reflected in:

[0018] 1. Low Energy Consumption. Traditional bonding processes require prolonged heat treatment at temperatures close to the crystal's melting point. For example, bonding sapphire crystals often requires temperatures exceeding 2000℃, while bonding YAG crystals, with their relatively lower melting point of 1970℃, typically requires temperatures above 1800℃. These high-temperature, high-pressure environments consume significant amounts of electricity. This invention utilizes a bonding paste that can complete the bonding process effectively at 900-1500℃ for 3-4 hours. Lower temperatures place lower demands on equipment and reduce energy consumption. This invention significantly reduces equipment energy consumption, making it significant for energy conservation and environmental protection.

[0019] 2. Reduced requirements for bonding surface flatness. Traditional bonding processes require atomic-level flatness of the crystal surface, where atoms diffuse to a certain depth under high temperature and pressure to form new chemical bonds. The bonding slurry of this invention, after dilution, exhibits good fluidity. Under controlled high temperature, it forms a liquid glass that can fill the microscopic grooves on the crystal surface. The surface unevenness increases the contact area of ​​the slurry to some extent. The two crystal sheets are in full contact and bonded together, and chemical bonds are formed during high-temperature heat treatment to complete the bonding process.

[0020] 3. Effectively Achieve Bonding of Heterogeneous Crystals. Different materials possess different physical properties, such as coefficients of thermal expansion, optical absorption characteristics, thermal conductivity, and mechanical properties. With the rapid development of modern technology, a single material often cannot meet all the required optical properties; therefore, it is necessary to integrate two or more materials to obtain the advantages of multiple materials. Traditional epitaxial growth methods can achieve the splicing growth of two heterojunctions. However, even if high-quality heterojunctions can be obtained through epitaxial growth, a large lattice mismatch during the epitaxial growth process will result in a high density of line dislocations. Furthermore, this method is difficult to achieve bonding between large-sized bulk heterojunctions. This invention effectively overcomes this difficulty, achieving low-cost bonding between heterojunctions.

[0021] The bonding slurry of this invention can form an extremely thin glass interface at the bonding interface of crystals. During the glass liquefaction process, partial atomic bonds are formed between the liquid glass and the more reactive ions at the interface of the two crystals, while the liquid glass fills the crystal interface. By controlling the ingredient composition and the heating and cooling process, the interfacial porosity and bonding strength can be adjusted.

[0022] Compared to traditional high-temperature bonding methods, the heating conditions of this invention are very mild, with low temperature and low energy consumption; the requirements for the flatness of the bonding surface are low; and it effectively achieves bonding between dissimilar crystals. This invention greatly simplifies the traditional high-temperature, high-pressure bonding process and significantly improves the yield. This invention is easy to implement, enables rapid bonding, has a high yield, and significantly reduces costs. Detailed Implementation

[0023] To fully understand the purpose, features and effects of the present invention, the technical solution of the present invention will be further described below with reference to the embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0024] Example 1: Vacuum High-Temperature Bonding of Two-Inch Sapphire Crystals

[0025] 1. Crystal bonding slurry, formed from the following powders in the following proportions: SiO2: 30%, Al2O3: 45%, MgO: 2%, CaF2: 3%, Na2O: 10%, B2O3: 10%. The powders are ball-milled with anhydrous ethanol for 24 hours to form a paste slurry.

[0026] 2. Surface cleaning treatment: The end faces of two 50.8×20 sapphire crystals are precision polished, placed in an ultrasonic vibration cleaning tank and cleaned with deionized water for 20 minutes, wiped with alcohol cotton and then dried in a clean room.

[0027] 3. Uniform coating: Fix the sapphire on the centrifuge and turn it on at 200 rpm. Use a 1×1×60 sapphire rod that has been cleaned in the same way to dip an appropriate amount of bonding slurry that has been fully diluted with anhydrous ethanol and drop it onto the center of the sapphire. After uniformly coating the sapphire surface, remove it.

[0028] 4. Apply pressure and secure: Use clamps to fix the two wafers, with a pressure range of 10–30 kg / cm². 2 Pressure holding time: 2.0 hours.

[0029] 5. High-temperature heat treatment: Place the tightly bonded crystal sheet into a high-temperature furnace, evacuate to a vacuum degree of 1.5×10^-3 Pa, heat to 1400℃ and hold for 3 hours.

[0030] 6. Cooling: Programmed cooling, slowly cooling to 500℃ in a vacuum environment for 12 hours, then purging with nitrogen to accelerate cooling, and removing and cleaning after 8 hours of cooling to room temperature.

[0031] Example 2: Vacuum bonding of 3×5×60 YAG transparent ceramic rods

[0032] 1. Crystal bonding slurry, formed from the following powders in the following proportions: SiO2: 30%, Al2O3: 45%, MgO: 2%, CaF2: 3%, Na2O: 10%, B2O3: 10%. The powders are ball-milled with anhydrous ethanol for 24 hours to form a paste slurry.

[0033] 2. Surface cleaning treatment: The bonding surfaces of two 3×5×60 YAG transparent ceramic rods are precision polished, placed in an ultrasonic vibration cleaning tank and cleaned with deionized water for 20 minutes, wiped with alcohol cotton and then air-dried in a clean room.

[0034] Uniform coating: Using a 1×1×60 sapphire rod that has been cleaned in the same way, dip an appropriate amount of bonding slurry that has been fully diluted with distilled water and coat it evenly on the transparent ceramic bonding surface. The surface should be free of obvious air bubbles.

[0035] Pressure bonding: Two wafers are fixed with clamps, with a pressure range of 10-30 kg / cm². 2 The pressure holding time is 2.0 hours.

[0036] 3. High-temperature heat treatment: After the crystal is pressed and tightly bonded, it is placed in a sintering furnace, and the vacuum is drawn to a vacuum degree of 1.5×10^-3Pa. The temperature is raised to 1400℃ and held for 3 hours.

[0037] Cooling: Programmed cooling, slowly cooling to 500°C in a vacuum environment for 12 hours, then purging with nitrogen to accelerate cooling, and finally removing and cleaning after 8 hours of cooling to room temperature.

[0038] Implementation Example 3: High-Temperature Air Bonding of 3×5×60 Sapphire Strips

[0039] 1. Crystal bonding slurry, formed from the following powders in the following proportions: SiO2: 30%, Al2O3: 45%, MgO: 2%, CaF2: 3%, Na2O: 10%, B2O3: 10%. The powders are ball-milled with anhydrous ethanol for 24 hours to form a paste slurry.

[0040] 2. Surface cleaning treatment: The bonding surfaces of two 3×5×60 Y-shaped sapphire bars are precision polished, placed in an ultrasonic vibration cleaning tank and cleaned with deionized water for 20 minutes, wiped with alcohol cotton and then air-dried in a clean room;

[0041] Uniform coating: Using a 1×1×60 sapphire rod that has been cleaned in the same way, dip an appropriate amount of bonding slurry that has been fully diluted with anhydrous ethanol and coat it evenly on the bonding surface of the sapphire rod, requiring that there are no obvious air bubbles on the surface.

[0042] Pressure bonding: Two wafers are fixed with clamps, with a pressure range of 10-30 kg / cm². 2 Pressure holding time: 2.0 hours;

[0043] High-temperature heat treatment: After the crystal is tightly bonded, it is placed in a muffle furnace and slowly heated to 1400℃ and held for 3 hours;

[0044] Cooling: Use programmed cooling, slowly cool down to 25°C for 20 hours, then remove.

[0045] Example 4: High-temperature air bonding of a two-inch sapphire crystal to a two-inch YAG transparent ceramic sheet

[0046] The crystal bonding slurry is formed from the following powders in the following proportions: SiO2: 35%, Al2O3: 33%, MgO: 20%, Na2O: 10%, B2O3: 2%. The powders are ball-milled with anhydrous ethanol for 24 hours to form a paste-like slurry.

[0047] Surface cleaning treatment: The Φ50.8×20 sapphire crystal and the Φ50.8×16 transparent ceramic end face are precision polished, placed in an ultrasonic vibration cleaning tank and cleaned with deionized water for 20 minutes, wiped with alcohol cotton and then air-dried in a clean room.

[0048] Uniform coating: Fix the sapphire on the centrifuge and turn it on at 200 rpm. Use a 1×1×60 sapphire rod that has been cleaned to dip an appropriate amount of bonding slurry that has been fully diluted with deionized water and drop it onto the center of the sapphire. After uniformly coating the sapphire surface, remove it.

[0049] Pressure bonding: Two wafers are fixed with clamps, with a pressure range of 10-30 kg / cm². 2 Pressure holding time: 2.0 hours;

[0050] High-temperature heat treatment: After the crystal is tightly bonded, it is placed in a muffle furnace and slowly heated to 1400℃ and held for 3 hours;

[0051] Cooling: Use programmed cooling, slowly cool down to 25℃ for 20 hours, then remove.

[0052] The crystals bonded in Examples 1 to 4 were subjected to a 200-day immersion test and 100 thermal cycles at 25-500°C. No cracks or damage appeared on the bonding surface.

[0053] This invention, by adjusting the proportions and temperature of the slurry components, forms a micrometer-scale glass transition interface between crystals. Compared to high-temperature bonding processes, this invention achieves atomic bonding between crystals at temperatures far below the crystal's melting point, resulting in strong bonding forces, a smooth and transparent interface, and no cloudiness at the interface. This method significantly simplifies traditional high-temperature, high-pressure bonding processes and substantially improves the yield.

[0054] Compared to traditional high-temperature bonding methods, the heating conditions of this invention are very mild, with low temperature and low energy consumption; the requirements for the flatness of the bonding surface are low; and it effectively realizes bonding between dissimilar crystals; this invention is easy to implement, enables rapid bonding, has a high yield, and greatly reduces costs.

[0055] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0056] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0057] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for bonding crystals, characterized in that, The bonding method includes the following steps: 1) Synthesizing the bonding slurry: The bonding slurry is formed by mixing the following powders in the following percentages: SiO2: 30-35%, Al2O3: 30-45%, MgO: 2%, CaF2: 3%, Na2O: 10%, B2O3: 2-10%. The powders are ball-milled with anhydrous ethanol to form a paste, which is the bonding slurry; 2) Pressurizing and bonding: The bonding slurry is diluted and uniformly coated or sprayed onto the surface of the crystal to be bonded, and the wafer is fixed with a jig for bonding; 3) High-temperature heat treatment: The bonded crystal is transferred to a high-temperature furnace for high-temperature sintering, and then cooled to room temperature before being removed; The bonding pressure in step 2) is 10-30 kg / cm². 2 The bonding and pressure holding time is 1.0-3.0 h; the temperature range of the high-temperature sintering in step 3) is 900-1500℃; after reaching the temperature range, it is held for another 2-4 hours; the cooling process in step 3) is to reduce the high-temperature sintering temperature to 300℃, with the cooling rate set at 0.2-0.5℃ / min, and after holding at 300℃ for 24 hours, the cooling rate is 0.5-5℃ / min until it drops to room temperature.

2. The crystal bonding method according to claim 1, characterized in that, Step 2) refers to diluting the slurry with any one of anhydrous ethanol, distilled water, deionized water, or acetone.