A method of joining single crystal alumina and metallic copper

Abstract

This invention relates to the field of nanosecond laser technology, and in particular to a method for joining single-crystal alumina and metallic copper, comprising the following steps: scanning the area to be joined between the single-crystal alumina and metallic copper using a nanosecond laser to achieve the joining of the single-crystal alumina and metallic copper. The nanosecond laser has a pulse width of 50-200 ns, a laser repetition frequency of 50-500 kHz, a laser power of 5-15 W, and a laser spot diameter of 20-50 μm. During the nanosecond laser scanning, the scanning speed is 30-200 mm / s, the scanning line spacing is 40-200 μm, and the number of scans is 1-10. This invention uses a nanosecond laser to join single-crystal alumina and metallic copper, which has the advantage of higher joining efficiency compared to traditional methods such as diffusion joining, brazing, and oxide sintering. Compared to femtosecond laser joining, it has lower cost, and nanosecond lasers are more mature and suitable for industrial applications.

Description

Technical Field

[0001] This invention relates to the field of nanosecond laser technology, and in particular to a method for joining single-crystal alumina and metallic copper. Background Technology

[0002] Transparent ceramic materials possess excellent physical properties, including high strength, high hardness, wear resistance, and good corrosion resistance. They also exhibit excellent optical transparency, high-temperature stability, and chemical stability, making them widely used in high-temperature pressure sensor substrates, microwave device windows, and display covers for smart terminal products, as well as LED light-emitting devices. However, the application of transparent ceramics in these optical-mechanical devices inevitably involves the challenge of bonding them with themselves or other metallic materials. To ensure the optical properties and mechanical strength of these devices during application, the transparent ceramic bonding interfaces must possess high strength and low residual stress.

[0003] Currently, the main methods for connecting transparent ceramics and metals, both domestically and internationally, include diffusion bonding, brazing, and adhesive bonding. However, due to the significant difference in the thermal expansion coefficients of the two materials, these traditional methods are difficult to achieve a reliable connection on their own. They often result in problems such as high residual stress, low joint strength, high joint brittleness, contamination, inability to process complex components, long connection time, and the need for pressure.

[0004] In view of this, the present invention proposes a novel method for joining single-crystal alumina and metallic copper. Summary of the Invention

[0005] The purpose of this invention is to provide a method for joining single-crystal alumina and metallic copper, which has the advantage of higher joining efficiency compared with traditional methods such as diffusion joining, brazing and adhesive bonding.

[0006] This invention provides a method for joining single-crystal alumina and metallic copper, comprising the following steps:

[0007] Nanosecond lasers are used to scan the connection points between single-crystal alumina and metallic copper to achieve the connection between the single-crystal alumina and metallic copper. Specifically, the pulse width of the nanosecond laser is 50-200 ns, the laser repetition frequency is 50-500 kHz, the laser power is 5-15 W, the laser spot diameter is 20-50 μm, the scanning speed is 30-200 mm / s, the scanning line spacing is 40-200 μm, and the number of scans is 1-10.

[0008] In the method for joining single-crystal alumina and metallic copper in this invention, when a nanosecond laser acts on the interface between alumina and metallic copper, the photon energy of the nanosecond laser is converted into electronic excitation energy and transferred to the underlying opaque metallic copper layer. This energy is then converted into heat energy and transferred to the alumina material, causing changes in the physical states of the joined materials, such as temperature increase and melting. During the nanosecond laser processing, under photochemical action, electrons in alumina and metallic copper undergo multiphoton absorption, causing electrons to transition from a steady state to an excited state. When the photon energy is sufficiently high, the connection between the two materials can be achieved by breaking the molecular bonds. This invention solves the problems of complex processes, high connection temperatures, and low joint quality in existing methods for joining transparent ceramic materials and metals. It achieves highly reliable, low-stress, and highly precise integrated fabrication and effective control of nanosecond laser micro-connectors for single-crystal alumina and metallic copper, resulting in a high-precision and highly reliable micro-connector with excellent comprehensive mechanical properties.

[0009] The present invention does not strictly limit the scanning path of nanosecond lasers, including but not limited to any one of the following: parallel line, cross, concentric rectangle, concentric circle and spiral.

[0010] Because of the high spatial selectivity of nanosecond lasers, when using nanosecond lasers to connect single-crystal alumina and metallic copper, the joint forms of single-crystal alumina and metallic copper are diverse, including but not limited to any one of stacking, overlapping, and butt jointing.

[0011] As a preferred embodiment of this technical solution, the following steps are included:

[0012] S1. Polish and ultrasonically clean the single crystal alumina and metallic copper to be joined in sequence to ensure that the surface to be processed is clean and free of contamination and to reduce the occurrence of processing defects.

[0013] S2. The ultrasonically cleaned single-crystal alumina and metallic copper are fixed to a movable processing platform using a fixture.

[0014] S3. Nanosecond laser scanning is used to connect single-crystal alumina and metallic copper.

[0015] As a preferred embodiment of this technical solution, in step S1, the polishing treatment of the single crystal alumina includes: using diamond polishing slurry to polish the single crystal alumina to be joined on a woolen polishing cloth for 10-20 minutes on both sides, and then polishing with clean water for 5-10 minutes; wherein, the average particle size of the diamond polishing slurry is 0.5-2μm;

[0016] The polishing process of the copper metal includes: using a diamond grinding disc to perform single-sided, step-by-step mechanical grinding of the copper metal, and then polishing it on a polishing machine; wherein the diamond grinding disc is of model 200-3000#.

[0017] As a preferred embodiment of this technical solution, in step S1, the ultrasonic cleaning includes: placing the polished single-crystal alumina and metallic copper in anhydrous ethanol for ultrasonic cleaning for 10-15 minutes, and then drying them.

[0018] Furthermore, the monocrystalline alumina and metallic copper to be joined in this invention can also use commercially available double-sided polished monocrystalline alumina and commercially available single-sided polished metallic copper.

[0019] In a preferred embodiment of this technical solution, in step S2, the use of the fixture is to ensure close contact between the single-crystal alumina and the copper material without affecting the nanosecond laser connection process. Furthermore, the gap between the single-crystal alumina and the copper material can be adjusted by adjusting the clamping force of the fixture. Specifically, when the joint of the single-crystal alumina and copper is stacked, to ensure the accuracy and strength of the nanosecond laser welding, the gap between the single-crystal alumina and copper is adjusted to less than 1 μm by adjusting the clamping force of the fixture, so that Newton's rings appear between the single-crystal alumina and copper; when the joint of the single-crystal alumina and copper is lapped, the gap between the single-crystal alumina and copper is less than 1 μm; when the joint of the single-crystal alumina and copper is butt-jointed, the gap between the single-crystal alumina and copper is less than 5 μm; finally, the fixture and the single-crystal alumina and copper to be connected are placed on the processing platform.

[0020] In a preferred embodiment of this technical solution, step S3 specifically includes: adjusting the focus of the nanosecond laser beam; adjusting the fixture placement orientation using a laser pointer to ensure the preset scanning position of the nanosecond laser; adjusting the focus position of the nanosecond laser beam to focus it on the interface between the single-crystal sapphire and the metallic copper to be joined; then, setting the parameters of the nanosecond laser on the laser operating system, including: output power, pulse width, repetition frequency, scanning path, scanning speed, scanning line spacing, and number of scans. After confirming that the information is correct, the laser is controlled to emit laser light for welding.

[0021] The method for joining single-crystal alumina and metallic copper of the present invention has at least the following technical advantages:

[0022] 1. In the method for joining single-crystal alumina and metallic copper of the present invention, when a nanosecond laser acts on the interface between alumina and metallic copper, the photon energy of the nanosecond laser is converted into electronic excitation energy and transferred to the underlying opaque metallic copper layer. This energy is then converted into heat energy and transferred to the alumina material, causing changes in the physical state of the joined materials, such as temperature increase and melting. Under photochemical action, alumina and metallic copper undergo multiphoton absorption, causing electrons to transition from a steady state to an excited state. When the photon energy is sufficiently high, the connection between the two materials can be achieved by breaking the molecular bonds.

[0023] 2. This invention uses nanosecond lasers to connect single-crystal alumina and metallic copper. Due to the strong thermal effect of nanosecond lasers, the material processing efficiency is higher under photochemical action compared to ultrafast lasers. Furthermore, by adjusting the processing parameters of the nanosecond laser, efficient connection between alumina and metallic copper can be achieved without material damage.

[0024] 3. The single-crystal alumina and copper joints obtained by nanosecond laser processing in this invention exhibit high shear strength, and no cracks were observed during optical and electron microscopy, resulting in excellent weld formation. Therefore, this method offers the advantage of higher joining efficiency compared to traditional methods such as diffusion bonding, brazing, and oxide sintering. Attached Figure Description

[0025] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This invention provides a nanosecond laser welding model. Figure 1 ;

[0027] Figure 2 This is a schematic diagram of the cross-scanning path of the nanosecond laser welding system of the present invention;

[0028] Figure 3 This is a schematic diagram of the lap joint configuration of the welded joint of the present invention;

[0029] Figure 4 This invention provides a nanosecond laser welding model. Figure 2 ;

[0030] Figure 5 This is a photograph of the welded sample connection of the present invention.

[0031] Figure 6 This is a displacement-stress curve of the joint shear force test in Embodiment 1 of the present invention. Detailed Implementation

[0032] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0033] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application. As used herein, the singular form includes the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this description, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0034] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1

[0036] S11. Polish and ultrasonically clean the single-crystal alumina and copper to be joined sequentially: Polish the single-crystal alumina and copper to be joined on a woolen polishing cloth for 15 minutes using 0.5-2μm diamond polishing fluid, and then polish with water for 10 minutes; Grind the copper to be joined on one side using a 2000# diamond grinding wheel in a stepwise manner, and then polish it on a polishing machine until there are no large scratches under a metallographic microscope; Place the polished single-crystal alumina and polished copper to be joined in anhydrous ethanol and ultrasonically clean them at 80Hz for 15 minutes, then remove them with tweezers and blow them dry.

[0037] S12. Fix the ultrasonically cleaned single crystal alumina and metallic copper to a movable processing platform using a fixture: stack the treated single crystal alumina and metallic copper in the fixture for fixing and clamping. Adjust the clamping force of the fixture so that Newton's rings appear when the single crystal alumina and metallic copper are stacked. At this time, the gap between the single crystal alumina and metallic copper is less than 1μm.

[0038] S13. Connecting single-crystal alumina and metallic copper using nanosecond laser scanning: Adjust the focus of the nanosecond laser beam, and use the laser pointer to adjust the fixture placement to ensure the preset scanning position of the nanosecond laser; adjust the focus of the nanosecond laser beam to focus on the interface between the single-crystal sapphire and metallic copper to be connected; then, set the nanosecond laser parameters on the laser operating system: pulse width 100ns, laser repetition frequency 200KHz, laser power 9.5W, laser spot diameter 30μm, laser scanning speed 100mm / s, number of scans 1, and scanning path cross-shaped (e.g., ...). Figure 2 As shown), the scan line spacing d is 50μm, which is approximately 1.5 times the spot diameter.

[0039] Example 2

[0040] S21. Polishing and ultrasonic cleaning are performed on the single-crystal alumina and metallic copper to be joined in sequence: Polish the single-crystal alumina to be joined on both sides of a woolen polishing cloth for 10 minutes using 0.5-2μm diamond polishing fluid, and then polish with water for 10 minutes; perform single-sided mechanical grinding of the metallic copper to be joined using a 200# diamond grinding wheel, and then polish it on a polishing machine until there are no large scratches under a metallographic microscope; place the polished single-crystal alumina and polished metallic copper in anhydrous ethanol and ultrasonically clean them at 80Hz for 10 minutes, remove them with tweezers and blow them dry.

[0041] S22. Secure the ultrasonically cleaned single-crystal alumina and metallic copper to a movable processing platform using a clamp: overlap the treated single-crystal alumina and metallic copper (e.g., ...). Figure 4 (As shown), and use a clamp to fix and clamp it, adjusting the clamping force of the clamp to make the gap between the single crystal alumina and the metallic copper less than 1μm;

[0042] S23. Connecting single-crystal alumina and metallic copper using nanosecond laser scanning: Adjust the focus of the nanosecond laser beam and use the laser pointer to adjust the fixture placement to ensure the preset scanning position of the nanosecond laser; adjust the focus of the nanosecond laser beam to focus on the interface between the single-crystal sapphire and metallic copper to be connected; then, set the parameters of the nanosecond laser on the laser operating system: pulse width of 100ns, laser repetition frequency of 500KHz, laser power of 11.5W, laser spot diameter of 30μm, laser scanning speed of 100mm / s, number of scans of 1, scanning path of cross-shaped and stacked, and scanning line spacing d of 120μm, approximately 4 times the spot diameter.

[0043] Compare with Example 1

[0044] The stacked single-crystal alumina and metallic copper are connected by brazing. The specific processing method is as follows:

[0045] First, prepare the single-crystal alumina and copper to be joined, and treat their surfaces to obtain pretreated single-crystal alumina and copper ceramics. Then, perform metallization treatment on the surfaces of the single-crystal alumina and copper to be joined to form an intermediate metal layer that bonds with the single-crystal alumina and copper to be joined. The coefficient of thermal expansion of the intermediate layer matches the coefficient of thermal expansion of the materials on both sides. Stack the single-crystal alumina, brazing filler metal, and copper in sequence and braze them. During brazing, heat to a first temperature at a first heating rate in a muffle furnace, hold at that temperature for a first predetermined time, then heat to a second temperature at a second heating rate, hold at that temperature for a second predetermined time, then heat to a third temperature at a third heating rate, hold at that temperature for a third predetermined time, then cool at a certain cooling rate, and finally cool with the furnace.

[0046] Compare with Example 2

[0047] The stacked single-crystal alumina and metallic copper are joined using a diffusion bonding method, and the specific processing method is as follows:

[0048] The monocrystalline alumina and copper to be joined are pretreated, and then an intermediate layer material is prepared. The pretreated intermediate layer material is placed between the monocrystalline alumina and copper, with its area slightly larger than the materials on either side. The parts to be joined are then secured using clamps. The parts are placed in a furnace, and a pressure of 10 MPa is applied to the assembly using a pressure head to ensure tight contact between the monocrystalline alumina, copper, and the intermediate layer material. A vacuum is then evacuated to a vacuum level of 5 × 10⁻⁶. -3Pa Start heating at a rate of 5-15℃ / min to reach the first temperature. Then adjust the pressure applied by the pressure head to 20MPa, maintain the temperature and pressure for 30 minutes, and then cool down to below the second temperature at a rate of 2℃ / min. Finally, remove the workpiece to complete the process.

[0049] Depend on Figure 1-6 It can be seen that no cracks were observed when connecting single-crystal alumina and metallic copper by nanosecond laser scanning, indicating that the weld formation effect is good. At the same time, after mechanical property shear test, based on the ratio of force to connection area, its shear strength can reach 64MPa, which can fully meet the needs of daily working conditions.

[0050] Compared to the traditional methods of joining single-crystal alumina and metallic copper in Examples 1-2, while the mechanical properties of the resulting connectors can meet the needs of daily working conditions, the processing often suffers from problems such as high residual stress, low joint strength, high joint brittleness, susceptibility to contamination, inability to process complex components, long connection time, and the need for pressurization. Therefore, compared to traditional methods such as diffusion bonding, brazing, and adhesive bonding, the nanosecond laser joining method of this invention has unparalleled convenience and environmental friendliness. The nanosecond laser scanning processing method of this invention has the advantages of simple operation, short processing time, low production cost, and higher connection efficiency.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of joining single-crystal aluminum oxide and metallic copper, characterized by, Includes the following steps: Nanosecond lasers are used to scan the connection points between single-crystal alumina and metallic copper to achieve the connection between single-crystal alumina and metallic copper. The nanosecond laser has a pulse width of 50-200ns, a laser repetition frequency of 50-500KHz, a laser power of 5-15W, a laser spot diameter of 20-50μm, a scanning speed of 30-200mm / s, a scanning line spacing of 40-200μm, and a scanning number of 1-10 times. During the connection process, when the nanosecond laser acts on the interface between the single-crystal alumina and the metallic copper, the photon energy of the nanosecond laser is converted into electronic excitation energy and transferred to the lower opaque metallic copper layer. Then it is converted into heat energy and transferred to the single-crystal alumina material, causing the connected materials to undergo changes in temperature and melting physical state.

2. The method of joining according to claim 1, wherein, The path of the nanosecond laser scanning includes any one of the following: parallel line, cross, concentric rectangle, concentric circle, and spiral.

3. The method of joining according to claim 1, wherein, When using nanosecond lasers to join single-crystal alumina and metallic copper, the joint type for single-crystal alumina and metallic copper can be any one of stacking, overlapping, or butt jointing.

4. The method of joining according to claim 1, wherein Includes the following steps: S1. Polish and ultrasonically clean the single-crystal alumina and metallic copper to be joined in sequence. S2. The ultrasonically cleaned single-crystal alumina and metallic copper are fixed to a movable processing platform using a fixture. S3. Nanosecond laser scanning is used to connect single-crystal alumina and metallic copper.

5. The method of joining according to claim 4, wherein, In step S1, the polishing process of the single-crystal alumina includes: The monocrystalline alumina to be joined is polished on both sides for 10-20 minutes using diamond polishing slurry on a woolen polishing cloth, and then polished with clean water for 5-10 minutes. The diamond polishing slurry has an average particle size of 0.5-2 μm. The polishing process for the copper metal includes: The copper metal is mechanically ground on one side in stages using a diamond grinding disc, and then polished on a polishing machine. The diamond grinding disc is model 200-3000#.

6. The method of joining according to claim 4, wherein In step S1, the ultrasonic cleaning includes: placing the polished single-crystal alumina and metallic copper in anhydrous ethanol for ultrasonic cleaning for 10-15 minutes, and then blowing them dry.

7. The method of joining according to claim 4, wherein In step S2, when the joint between the single crystal alumina and the metallic copper is stacked, the gap between the single crystal alumina and the metallic copper is adjusted to be less than 1 μm by adjusting the clamping force of the fixture. When the joint between monocrystalline alumina and metallic copper is lapped, the gap between the monocrystalline alumina and metallic copper is less than 1μm. When the joint between monocrystalline alumina and metallic copper is butt joint, the gap between the monocrystalline alumina and metallic copper is less than 5μm.

8. The method of joining according to claim 4, wherein Step S3 specifically includes: adjusting the focus of the nanosecond laser beam to focus it on the interface between the single crystal alumina and the metallic copper, and setting the operating parameters of the nanosecond laser to perform nanosecond laser connection.

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