阅读说明：本技术 一种激光陶瓷与晶体的键合方法 (Bonding method of laser ceramic and crystal ) 是由 马杰 高泰鹏 杨帆 沈吉 沈德元 唐定远 于 2021-09-07 设计创作，主要内容包括：本发明公开了一种激光陶瓷与晶体的键合方法,包括激光陶瓷的第一键合面和晶体的第二键合面经光学加工后,用去离子水和酒精多次清洗并烘干；将激光陶瓷和晶体置于等离子清洗机内,清洗并活化第一键合面和第二键合面；在惰性气体保护气氛或真空下将第一键合面紧密贴合第二键合面,对激光陶瓷和晶体进行光胶；将光胶后的激光陶瓷和晶体固定于夹具中,并随夹具一起置于真空加热炉中退火10-60小时；将保温处理后的激光陶瓷和晶体冷却至室温,并从夹具中取出,完成激光陶瓷和晶体的键合。本发明能够在低温退火条件下实现不同热膨胀系数的激光陶瓷与晶体等异种材料之间的有效键合,具有广泛的应用前景。(The invention discloses a bonding method of laser ceramic and crystal, comprising the steps of cleaning and drying a first bonding surface of the laser ceramic and a second bonding surface of the crystal for many times by deionized water and alcohol after optical processing; placing the laser ceramic and the crystal in a plasma cleaning machine, and cleaning and activating the first bonding surface and the second bonding surface; tightly attaching the first bonding surface to the second bonding surface in an inert gas protective atmosphere or vacuum, and performing optical gluing on the laser ceramic and the crystal; fixing the laser ceramic and the crystal after the optical cement in a clamp, and putting the laser ceramic and the crystal together with the clamp in a vacuum heating furnace for annealing for 10-60 hours; and cooling the laser ceramic and the crystal after the heat preservation treatment to room temperature, and taking out the laser ceramic and the crystal from the clamp to complete the bonding of the laser ceramic and the crystal. The invention can realize effective bonding between different materials such as laser ceramics and crystals with different thermal expansion coefficients under the condition of low-temperature annealing, and has wide application prospect.)

1. A bonding method of laser ceramic and crystal is characterized by comprising the following steps:

after the first bonding surface of the laser ceramic (1) and the second bonding surface of the crystal (2) are optically processed, the first bonding surface and the second bonding surface are washed for multiple times by deionized water and alcohol and are placed in an oven (3) for drying;

placing the laser ceramic (1) and the crystal (2) in a plasma cleaning machine (4), and cleaning and activating the first bonding surface and the second bonding surface;

performing optical gluing on the laser ceramic (1) and the crystal (2) in an inert gas protective atmosphere or vacuum to enable the first bonding surface to be tightly attached to the second bonding surface;

fixing the laser ceramic (1) and the crystal (2) after the optical cement treatment in a fixture (5), and placing the fixture (5) and the laser ceramic in a vacuum heating furnace (6);

heating the temperature of the vacuum heating furnace (6) to an annealing temperature, and keeping the temperature at the annealing temperature for 10-60 hours; the annealing temperature is 50-500 ℃;

and cooling the laser ceramic (1) and the crystal (2) after the heat preservation treatment to room temperature, taking out the laser ceramic and the crystal (2) together with the clamp (5) from the vacuum heating furnace (6), and taking out the bonding material from the clamp (5) to complete the bonding of the laser ceramic (1) and the crystal (2).

2. The method for bonding a laser ceramic to a crystal according to claim 1, wherein the laser ceramic (1) is a transparent sesquioxide ceramic, a garnet ceramic, or a fluoride ceramic; the crystal (2) is a garnet crystal, a fluoride crystal or an oxide crystal.

3. The method of claim 1, wherein the flatness of the optically processed first and second bonding surfaces is better than λ/10, wherein λ =632.8 nm and the roughness is less than 1.0 nm.

4. The method of claim 1, wherein the number of cleaning cycles is at least 3.

5. The bonding method of laser ceramic and crystal according to claim 1, characterized in that the temperature in the oven (3) is 45-155 ℃; the drying time is 1-6 hours.

6. The bonding method of laser ceramic and crystal according to claim 1, wherein the vacuum pressure in the plasma cleaning machine (4) is 0.1-0.4 mbar; the plasma in the plasma cleaning machine (4) is argon plasma or argon-hydrogen plasma; the power of the plasma cleaning machine (4) is not lower than 50W.

7. The method for bonding laser ceramic and crystal according to claim 1, wherein the clamp (5) continuously applies pressure to the laser ceramic (1) and the crystal (2), and the pressure direction is perpendicular to the first bonding surface and the second bonding surface.

8. The bonding method of laser ceramic and crystal according to claim 1, wherein the fixture (5) is a stainless steel fixture or a graphite fixture.

9. The method of claim 1, wherein the temperature is heated at a rate of 3-5 ℃/min.

10. The method of claim 1, wherein the cooling rate is 1-3 ℃/min.

Technical Field

The invention relates to a bonding method of laser ceramic and a crystal, belonging to the technical field of laser material preparation.

Background

With the increasingly wide requirements of the fields of modern national defense, scientific research, industry, medical treatment and the like on high-power, high-efficiency and high-energy lasers, the research and development of all-solid-state lasers with better performance is an important research direction in the field of laser technology at present.

As a core element of a laser, a laser material is one of key factors determining the performance of the laser, and compared with the currently common single crystal laser material, the transparent laser ceramic has the advantages of simple preparation, low cost, capability of realizing large-size and high-concentration doping, good thermal shock resistance, capability of mass production and the like, and is a very potential solid laser material. Particularly, the ceramic-ceramic and ceramic-single crystal composite structure laser gain material is prepared by bonding and other processes, the realizable forms of the laser gain medium are greatly enriched, and great flexibility is provided for the design of a high-performance solid laser.

The bonding technology is a technology that under the condition without an adhesive, materials with surface flatness meeting the requirement of the optical cement are applied with certain pressure through polishing treatment to be bonded together, van der waals force or other bonding modes are bonded together to realize pre-bonding, and molecules on the surfaces of the materials are mutually diffused and fused through high-temperature heat treatment in atmosphere or vacuum environment to finally form a more stable chemical bond, so that a whole material is formed.

In the technical field of laser, the bonding technology is a common material composite technology, and a bonding crystal is used as a laser working substance, so that the heat effect of a gain medium can be effectively reduced, the heat load is controlled, the deformation and damage of the end face of the gain medium are reduced, and the wavefront distortion of a light beam is reduced, thereby improving the beam quality of a laser, improving the efficiency of the laser, and being very beneficial to the miniaturization and integration of a laser device.

In a conventional crystal thermal bonding method, two precisely processed crystals are subjected to optical glue and then applied with external pressure perpendicular to a bonding surface to be tightly attached together, and then heated to a temperature near the melting point of the crystals to realize mutual permeation of ions at the bonding surface, thereby finally achieving the purpose of bonding. However, the thermal bonding method has the disadvantages that gas in a bonding surface is difficult to diffuse out, the bonding surface is easy to crack due to uneven pressure, the lattice structure is easy to change due to overhigh temperature, and the like, and particularly for bonding between laser transparent ceramics and crystals with different thermal expansion coefficients, stress is formed on the bonding surface due to the difference of thermal expansion changes of different materials in the high-temperature heat treatment process after optical cement, so that the bonding surface is likely to break, and meanwhile, long-time high-temperature heat treatment may also affect the optical performance of the bonding surface, and transmission loss is increased.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a high-quality bonding method of laser ceramics and crystals.

The invention utilizes plasma to pretreat the surfaces to be bonded of the laser ceramic and the crystal, and can obtain a laser ceramic and crystal composite structure material with good bonding under the condition of low-temperature annealing.

In order to achieve the purpose, the invention is realized by adopting the following technical scheme:

after the first bonding surface of the laser ceramic and the second bonding surface of the crystal are optically processed, the surface of the material is washed by deionized water and alcohol for multiple times and is placed in an oven for drying;

placing the laser ceramic and the crystal in a plasma cleaning machine, and cleaning and activating the first bonding surface and the second bonding surface;

placing the laser ceramic and the crystal in an inert gas protective atmosphere or vacuum for optical gluing, so that the first bonding surface is tightly attached to the second bonding surface;

fixing the laser ceramic and the crystal after the optical cement in a clamp, and placing the laser ceramic and the crystal together with the clamp in a vacuum heating furnace for heat treatment, wherein the clamp is vertical to a bonding surface and keeps certain pressure on the bonding material unchanged;

heating the temperature of the vacuum heating furnace to the annealing temperature, and continuously keeping the temperature at the annealing temperature for 10-60 hours; the annealing temperature is 50-500 ℃;

and cooling the laser ceramic and the crystal after the heat treatment to room temperature, taking out the laser ceramic and the crystal together with the clamp from the vacuum heating furnace, and taking out the bonding material from the clamp to complete the bonding of the laser ceramic and the crystal.

Further, the laser ceramic is a transparent sesquioxide ceramic, a garnet ceramic, or a fluoride ceramic; the crystal is a garnet crystal, a fluoride crystal or an oxide crystal.

Further, the flatness of the first bonding surface and the second bonding surface after optical processing is better than lambda/10, wherein lambda =632.8 nm, and the roughness is less than 1.0 nm. After the laser ceramic and the crystal are respectively ground and polished, when the flatness of the first bonding surface and the second bonding surface is superior to lambda/10 (lambda =632.8 nm) and the roughness is less than 1.0 nm, strong van der Waals force is easily formed between the bonding surfaces.

Further, the number of times of the cyclic cleaning is at least 3. Impurities adhered to the surfaces of the laser ceramic and the crystal can be removed.

Further, the temperature in the oven is 45-155 ℃; the drying time is 1-6 hours. The water vapor at the bonding surface of the laser ceramic and the crystal can be removed.

Further, the vacuum pressure in the plasma cleaning machine is 0.1-0.4 mbar; the inert gas in the plasma cleaning machine comprises argon or argon-hydrogen mixed gas; the power of the plasma cleaning machine is not lower than 50W. And activating the first bonding surface and the second bonding surface for 3 minutes by adopting inert gas argon or argon-hydrogen mixed gas under the power of 50W, and not only can further clean gas such as water vapor and organic impurities adsorbed by the surfaces to be bonded, but also can introduce polar groups and active points on the surfaces of the first bonding surface and the second bonding surface to form dangling bonds on the surfaces to be bonded. The dangling bonds formed by the active groups and the active points on the surfaces to be bonded enable the bonding surfaces to have strong adsorption capacity, partial dangling bonds on the surfaces of the first bonding surface and the second bonding surface are combined to form covalent bonds in the attaching process, and chemical bonds between the two bonding surfaces can be further recombined through further annealing treatment to form a more stable covalent bond network, so that high-quality bonding is realized. The bonding surface is treated by the plasma, so that the problem of thermal mismatch among different materials caused by high temperature in the traditional high-temperature bonding process can be avoided, and the bonding strength of dissimilar materials is greatly enhanced.

Further, the clamp continuously applies pressure to the laser ceramic and the crystal to realize room-temperature pre-bonding; the pressure direction is perpendicular to the first bonding face and the second bonding face.

Further, the clamp is a stainless steel clamp or a graphite clamp.

Further, the speed of the temperature heating is 3-5 ℃/min.

Further, the cooling speed is 1-3 ℃/min.

Compared with the prior art, the invention has the following beneficial effects:

the surfaces to be bonded of the laser ceramic and the crystal are pretreated by the plasma cleaning machine, namely polar groups and active points are introduced into the surfaces of the first bonding surface and the second bonding surface to form dangling bonds on the two surfaces to be bonded, so that the two surfaces to be bonded have strong adsorption capacity, partial dangling bonds of the two bonding surfaces are combined in the attaching process to form covalent bonds, and the chemical bonds between the two bonding surfaces are further recombined through further annealing treatment to finally form a more stable and perfect covalent bond network. The method can greatly enhance the bonding strength of dissimilar materials while solving the problem of thermal mismatch among different materials, thereby realizing the aim of low-temperature bonding; according to the invention, the surface to be bonded is pretreated by adopting the plasma, so that the problems of bonding surface fracture and the like caused by overlarge thermal stress of the bonding surface due to annealing at high temperature in the traditional bonding method can be avoided, and bonding of a dissimilar matrix material with higher bonding strength can be obtained under the low-temperature annealing condition.

Drawings

FIG. 1 is a process flow diagram of a bonding method of the present invention;

reference numeral 1: 1. laser ceramics; 2. a crystal; 3. an oven; 4. a plasma cleaning machine; 5. a clamp; 6. and (5) heating the furnace in vacuum.

Detailed Description

The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

In order to realize the bonding of high-quality laser ceramics and different host materials such as crystals and the like under the condition of low-temperature annealing, the invention provides a bonding method of laser ceramics and crystals, and the bonding method comprises the following steps with reference to fig. 1:

after the first bonding surface of the laser ceramic 1 and the second bonding surface of the crystal 2 are optically processed, the first bonding surface and the second bonding surface are washed for many times by deionized water and alcohol and are placed in an oven 3 for drying;

placing the laser ceramic 1 and the crystal 2 in a plasma cleaning machine 4, and cleaning and activating the first bonding surface and the second bonding surface;

placing the laser ceramic 1 and the crystal 2 in a glove box for optical cement to enable the first bonding surface to be tightly attached to the second bonding surface;

fixing the laser ceramic 1 and the crystal 2 after the optical cement in a clamp 5, and placing the laser ceramic and the crystal in a vacuum heating furnace 6 along with the clamp 5;

heating the temperature of the vacuum heating furnace 6 to the annealing temperature, and keeping the annealing temperature for 10-60 hours; the annealing temperature is 50-500 ℃; during heat treatment, the temperature rising speed is controlled to be 3-5 ℃/min, and the cooling speed is controlled to be 1-3 ℃/min.

And cooling the laser ceramic 1 and the crystal 2 after the heat preservation treatment to room temperature, taking out the laser ceramic 1 and the crystal 2 together with the clamp 5 from the vacuum heating furnace 6, and then taking out the laser ceramic 1 and the crystal 2 from the clamp 5 to complete the bonding of the laser ceramic 1 and the crystal 2.

The present invention is further described in detail with reference to the following examples, which are only used to more clearly illustrate the technical solutions of the present invention, but not to limit the scope of the present invention.

Example 1

The laser ceramic of the embodiment is Yb to Lu₂O₃The crystal is Cr and YAG.

Referring to fig. 1, first, 3 x 2 mm is prepared³Yb of Lu₂O₃(ytterbium-doped 3 at%) laser ceramic 1; preparation of 3X 3 mm³The Cr of (1) is YAG crystal 2; and defines a first bonding surface of the laser ceramic 1 and a second bonding surface of the crystal 2. Respectively to the first bonding surfacesAnd a second bonding surface polishing, wherein Yb: Lu₂O₃The flatness of the bonding surface of the transparent ceramic 1 is 51.2 nm, the roughness is 0.43 nm, the flatness of the bonding surface of the Cr: YAG crystal 2 is 48.7 nm, and the roughness is 0.45 nm. .

And then, alternately and repeatedly cleaning the first bonding surface and the second bonding surface by using deionized water and alcohol, and respectively repeating for 3 times to remove impurities adhered to the first bonding surface and the second bonding surface. And opening the cleaned laser ceramic 1 and the crystal 2 into an oven 3 preheated to 50 ℃ for 4 hours, so that the moisture of the first bonding surface and the second bonding surface is completely dried. But not limited thereto, those skilled in the art can adjust the temperature and the drying time of the oven 3 according to different conditions such as the kind and volume of the material to be bonded, and the water content of the surface to be bonded.

Then, the laser ceramic 1 and the crystal 2 were simultaneously put into the plasma cleaning machine 4 and treated with plasma for 3 minutes. The vacuum pressure of the plasma cleaning machine 4 is 0.2 mbar, and the plasma in the plasma cleaning machine 4 is argon plasma, namely, the argon plasma is used for treating the first bonding surface and the second bonding surface for 3 minutes in the plasma cleaning machine with the vacuum pressure of 0.2 mbar. But not limited thereto, those skilled in the art can adjust the plasma power, vacuum pressure and processing time of the plasma cleaning machine 4 according to different conditions such as the kind and volume of the material to be bonded, flatness and area of the surface to be bonded, and the like. At the moment, after argon plasma treatment, dangling bonds can be formed on the surface to be bonded, so that the bonding surface has strong adsorption capacity.

And then, immediately bonding the laser ceramic 1 and the crystal 2 processed by the plasma cleaning machine in an argon atmosphere, namely, tightly bonding the first bonding surface and the second bonding surface in the argon atmosphere without a gap.

And then, placing the attached laser ceramic 1 and crystal 2 into a clamp 5, and continuously applying pressure 500N to the laser ceramic 1 and the crystal 2 by the clamp 5, wherein the pressure direction is vertical to the first bonding surface and the second bonding surface. And in the process of fitting and pressing, dangling bonds with strong surface activity of the first bonding surface and the second bonding surface are combined to form covalent bonds, so that preliminary covalent bond connection is realized. But not limited thereto, those skilled in the art may reasonably adjust the magnitude of the applied pressure according to different conditions such as the type and area of the materials to be bonded, and the like, so as to avoid unexpected deformation of the materials to be bonded due to excessive pressure during the heat treatment process.

And (3) placing a clamp 5 tightly clamping the laser ceramic 1 and the crystal 2 into a vacuum heating furnace 6, heating the temperature in the vacuum heating furnace 6 to 400 ℃ at the speed of 3 ℃/min, keeping the constant temperature for 24 hours after the temperature in the vacuum heating furnace is stable, and finally cooling the temperature in the vacuum heating furnace 6 to room temperature at the speed of 1 ℃/min. Under the condition of low-temperature annealing, chemical bonds between the two bonding surfaces can be further recombined to finally form a more stable and perfect covalent bond network, so that the aim of high-quality bonding between dissimilar materials is fulfilled. But not limited thereto, a person skilled in the art can reasonably adjust the temperature rising speed, the annealing temperature and the temperature lowering speed according to different conditions such as the type and the area of the materials to be bonded, and avoid the fracture of the bonding surface caused by the excessive thermal stress generated between the bonding materials.

And finally, taking the clamp 5 out of the vacuum heating furnace 6, and taking the laser ceramic 1 and the crystal 2 out of the clamp 5, namely finishing the bonding of the laser ceramic 1 and the crystal 2.

The detection shows that under the irradiation of helium neon laser, the bonding surface of the laser ceramic 1 and the crystal 2 is intact, and no air holes or scattering phenomenon exists.

Example 2

The laser ceramic of the embodiment is Yb: Y₂O₃The crystal is Cr and YAG.

Referring to fig. 1, first, 3 x 2.5 mm is prepared³Yb of (b) Y₂O₃(ytterbium-doped 3 at%) transparent ceramic 1; preparation of 3X 3 mm³The Cr of (1) is YAG crystal 2; and defines a first bonding surface of the laser ceramic 1 and a second bonding surface of the crystal 2. Polishing the first bonding surface and the second bonding surface respectively, wherein Yb: Y₂O₃The flatness of the bonding surface of the transparent ceramic 1 is 59.4 nm, the roughness is 0.47 nm, and the flatness of the bonding surface of the Cr-YAG crystal 2 is 59.6nm, roughness 0.49 nm.

And then, alternately and repeatedly cleaning the first bonding surface and the second bonding surface by using deionized water and alcohol, and respectively repeating for 3 times to remove impurities on the first bonding surface and the second bonding surface. And opening the cleaned laser ceramic 1 and the crystal 2 into an oven 3 preheated to 80 ℃ for 2 hours, so that the moisture of the first bonding surface and the second bonding surface is completely dried. But not limited thereto, those skilled in the art can adjust the temperature and the drying time of the oven 3 according to different conditions such as the kind and volume of the material to be bonded, and the water content of the surface to be bonded.

Then, the laser ceramic 1 and the crystal 2 were simultaneously put into the plasma cleaning machine 4 and treated with plasma for 3 minutes. The vacuum pressure of the plasma cleaning machine is 0.3 mbar, the plasma in the plasma cleaning machine 4 is argon plasma, namely, the argon plasma is used for treating the first bonding surface and the second bonding surface for 3 minutes in the plasma cleaning machine with the vacuum pressure of 0.3 mbar. Without being limited thereto, those skilled in the art can adjust the plasma, the vacuum pressure and the processing time in the plasma cleaning machine 4 according to various conditions such as the kind and volume of the material to be bonded, the flatness and area of the surface to be bonded, and the like. And similarly, through argon plasma treatment, dangling bonds are formed on the surface to be bonded, so that the bonding surface has strong adsorption capacity.

And then, immediately carrying out bonding treatment on the laser ceramic 1 and the crystal 2 which are treated by the plasma cleaning machine in vacuum, namely, tightly bonding the first bonding surface and the second bonding surface in vacuum without a gap.

And then, placing the attached laser ceramic 1 and crystal 2 into a clamp 5, and continuously applying pressure 100N to the laser ceramic 1 and the crystal 2 by the clamp 5, wherein the pressure direction is vertical to the first bonding surface and the second bonding surface. And in the process of fitting and pressing, dangling bonds with strong surface activity of the first bonding surface and the second bonding surface are combined to form covalent bonds, so that preliminary covalent bond connection is realized. But not limited thereto, those skilled in the art may reasonably adjust the magnitude of the applied pressure according to different conditions such as the type and area of the materials to be bonded, and the like, so as to avoid unexpected deformation of the materials to be bonded due to excessive pressure during the heat treatment process.

And (3) placing a clamp 5 tightly clamping the laser ceramic 1 and the crystal 2 into a vacuum heating furnace 6, heating the temperature in the vacuum heating furnace 6 to 450 ℃ at the speed of 5 ℃/min, keeping the constant temperature for 48 hours after the temperature in the vacuum heating furnace is stable, and finally cooling the temperature in the vacuum heating furnace 6 to room temperature at the speed of 2 ℃/min. Under the condition of low-temperature annealing, chemical bonds between the two bonding surfaces can be further recombined to finally form a more stable and perfect covalent bond network, so that the aim of high-quality bonding between dissimilar materials is fulfilled. But not limited thereto, a person skilled in the art can reasonably adjust the temperature rising speed, the annealing temperature and the temperature lowering speed according to different conditions such as the type and the area of the materials to be bonded, and avoid the fracture of the bonding surface caused by the excessive thermal stress generated between the bonding materials.

And finally, taking the clamp 5 out of the vacuum heating furnace 6, and taking the laser ceramic 1 and the crystal 2 out of the clamp 5, namely finishing the bonding of the laser ceramic 1 and the crystal 2.

The detection shows that under the irradiation of helium neon laser, the bonding surface of the laser ceramic 1 and the crystal 2 is intact, and no air holes or scattering phenomenon exists.

In summary, in the present invention, the plasma is introduced to treat the surface to be bonded in the bonding process of the ceramic and the crystal, so that not only are impurities on the surface to be bonded further cleaned, but also a polar group and an active site are introduced to the surface to be bonded, so that a dangling bond is formed on the surface to be bonded, so that the bonding surface has a strong adsorption capacity, part of dangling bonds on two surfaces to be bonded are combined to form a covalent bond in the bonding process, and then further annealing treatment is performed, so that the chemical bond between the first bonding surface and the second bonding surface is further recombined to form a more stable covalent bond network, thereby achieving high-quality bonding. Compared with the traditional method, the method can realize the bonding between different heterogeneous materials such as laser ceramics and crystals under the condition of low-temperature annealing, and improve the bonding strength.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.