Method for sintering joining of oxide ceramics using high dislocation density noble metal particle foils in air

Abstract

The application discloses a method for sintering and connecting oxide ceramics in air by using a high-dislocation-density noble metal particle foil, and aims at solving the problems of poor high-temperature stability, poor sealing performance and low mechanical strength of existing ceramic connecting joints. The method for sintering and connecting oxide ceramics comprises the following steps: 1, mechanically ball-milling a noble metal powder; 2, mixing the noble metal particles, a binder, a solvent and a dispersing agent to prepare a slurry, and then flowing the slurry into a noble metal particle intermediate layer foil through a flow forming machine; 3, pre-oxidizing the to-be-welded ceramics by heating to 1000-1100 DEG C in an air atmosphere; 4, ultrasonic cleaning; 5, assembling the to-be-welded parts; and 6, placing the assembled to-be-welded parts in a muffle furnace, and then sintering and connecting the to-be-welded parts by heating to 890-920 DEG C in air. In the application, the noble metal intermediate layer foil is used to connect the ceramics, the noble metal does not react with the ceramics on both sides, the interface is tightly connected, no new phase is generated in the joint, and the high-temperature stability of the joint is enhanced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of ceramic connection, and particularly relates to a method for sintering and connecting oxide or easily-oxidized ceramic in air by using a high-dislocation-density noble metal particle interlayer foil. BACKGROUND

[0002] With the development of science and technology, electronic devices are increasingly miniaturized and high-performing, and in high-frequency, high-speed and high-power electronic devices, higher demands are put forward for ceramic packaging materials in terms of thermal conductivity, electrical conductivity, mechanical strength and chemical stability. However, a single kind of ceramic is difficult to simultaneously have all the required properties, which limits the application of the material.

[0003] Active metal brazing is a widely used ceramic interconnection method, but this method has the following disadvantages: 1. In an oxidizing atmosphere at a high temperature of more than 500 DEG C, the active elements in the brazed joint will be oxidized, resulting in poor high-temperature stability of the joint; 2. Due to the change in oxygen solubility in molten and solid metals, air reaction brazed joints have obvious pores, which reduces the sealing performance and strength of the joint; 3. Welding at a relatively high temperature (higher than the melting point of the metal) will result in large residual stress in the joint, which reduces the mechanical properties of the joint; 4. The tabletting method used in traditional brazing is difficult to make brazing sheets of a larger area and is easy to break during clamping, which is difficult to apply to larger-area and more complex ceramic surface connection. These limit the application of the material to a certain extent. Therefore, a new method is needed to realize ceramic material connection at a lower temperature, obtain a joint with better high-temperature stability, better density and higher mechanical strength, and adapt to larger-area and more complex ceramic surface connection, which provides the possibility for efficient mass production. SUMMARY

[0004] The present application aims to solve the problems of poor high-temperature stability, poor sealing performance and low mechanical strength of the existing ceramic connection joint, and provides a method for sintering and connecting oxide ceramic in air by using a high-dislocation-density noble metal particle foil.

[0005] The method for sintering and connecting oxide ceramic in air by using a high-dislocation-density noble metal particle foil according to the present application is implemented according to the following steps:

[0006] I. Put the noble metal powder into a planetary ball mill for mechanical ball milling to prepare noble metal particles with a particle size of 1-3 microns;

[0007] II. Mix the noble metal particles, binder, solvent and dispersant to prepare a slurry, and the slurry is cast into a flexible noble metal particle interlayer foil by a casting machine;

[0008] III. Put the ceramic to be welded into a muffle furnace, and heat to 1000-1100 DEG C under air atmosphere for pre-oxidation treatment, and then cool to room temperature to obtain the pre-oxidized ceramic;

[0009] IV. Put the pre-oxidized ceramic into anhydrous ethanol for ultrasonic cleaning to obtain the cleaned ceramic to be welded;

[0010] V. Stack the ceramic to be welded and the noble metal particle interlayer foil in the order of ceramic to be welded / interlayer foil / ceramic to be welded, and apply assembly pressure of 0.8-1 MPa to obtain the assembled piece to be welded;

[0011] VI. Put the assembled piece to be welded into a muffle furnace, and gradually heat to 890-920 DEG C under air atmosphere for sintering connection, and gradually cool to room temperature to complete the sintering connection of the oxide ceramic;

[0012] In step I, the material of the noble metal powder is gold, silver, platinum or palladium, and in step III, the ceramic to be welded is an oxide ceramic or an easily-oxidized ceramic.

[0013] The present application proposes a method for sintering connection of oxide ceramic using high-dislocation-density noble metal particle foil, which realizes sintering connection of ceramic material at a lower temperature (890-920 DEG C). The sintering driving force is provided by the high surface energy and micron-level size of the noble metal particles. Particle size exceeding 3 microns will result in insufficient driving force, while nano-level size will cause the noble metal particle interlayer to densify in advance at a temperature lower than the ceramic / metal connection (890-920 DEG C), thereby affecting the close adhesion of the ceramic and the noble metal particles at the interface. The sintering effect of micron-level noble metal particles and the high-density dislocations introduced in the high-energy ball milling process promote the mutual diffusion of the metal and the ceramic, forming a reliable connection. On the other hand, the oxide ceramic surface has oxygen vacancy defects, and the pre-oxidation process in air increases the oxygen vacancy density on the ceramic surface. The noble metal-O bonds formed at the interface can be embedded into the oxygen vacancies on the ceramic surface, and this interface connection is the key to further improving the mechanical strength of the joint. The flexible metal foil prepared by flow casting solves the problem of small size and fragility of the metal sheet prepared by dry pressing. The present application can be applied to larger areas and more complex ceramic surfaces, and provides the possibility for efficient mass production.

[0014] The method for sintering connection of oxide ceramic using high-dislocation-density noble metal particle foil in air of the present application mainly includes the following beneficial effects:

[0015] 1. The noble metal interlayer foil is used to connect the ceramic, the noble metal does not react with the ceramic on both sides, no new phase is generated in the joint, and the high-temperature stability of the joint is enhanced.

[0016] 2. The high-density dislocations and micron-level sintering driving force promote the complete densification of the noble metal intermediate layer, and the joint is sealed.

[0017] 3. Compared with the traditional ceramic connection method, the mutual diffusion and atomic bonding are realized at the interface between the noble metal and the ceramic in the application, and the mechanical strength of the joint is further improved.

[0018] 4. The flexible noble metal intermediate layer foil prepared by high-energy ball milling and tape casting can be applied to larger area and more complex ceramic surfaces, and is easy to realize efficient, automatic and batch production. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Figure 4 is a backscattering electron image of the microstructure of the AlN ceramic / Al2O3 ceramic joint on the AlN ceramic side obtained by using the high-dislocation-density silver particle foil intermediate layer in Example 1 under the condition of 920℃ / 1MPa / 30min.

[0020] Figure 2 Figure 4 is a backscattering electron image of the microstructure of the AlN ceramic / Al2O3 ceramic joint on the AlN ceramic side obtained by using the high-dislocation-density silver particle foil intermediate layer in Example 1 under the condition of 920℃ / 1MPa / 30min.

[0021] Figure 3 Figure 4 is a backscattering electron image of the microstructure of the AlN ceramic / Al2O3 ceramic joint on the AlN ceramic side obtained by using the high-dislocation-density silver particle foil intermediate layer in Example 1 under the condition of 920℃ / 1MPa / 30min. DETAILED DESCRIPTION

[0022] Specific embodiment one: the method for sintering and connecting oxide ceramics in air by using high-dislocation-density noble metal particle foil according to the following steps:

[0023] I. Put the noble metal powder into the planetary ball mill for mechanical ball milling to prepare noble metal particles with a particle size of 1-3μm;

[0024] II. Mix the noble metal particles, binder, solvent and dispersant to prepare a slurry, and the slurry is cast into a flexible noble metal particle intermediate layer foil by a tape casting machine;

[0025] III. Put the to-be-welded ceramic into a muffle furnace, heat to 1000-1100℃ in air atmosphere for pre-oxidation treatment, and then cool to room temperature to obtain the pre-oxidized ceramic;

[0026] IV. Put the pre-oxidized ceramic into anhydrous ethanol for ultrasonic cleaning to obtain the cleaned to-be-welded ceramic;

[0027] V. The ceramic to be welded and the noble metal particle interlayer foil are stacked in the order of ceramic to be welded / interlayer foil / ceramic to be welded, and a fitting pressure of 0.8-1 MPa is applied to obtain a fitted part to be welded;

[0028] VI. The fitted part to be welded is placed in a muffle furnace, and sintering connection is performed in air by (gradually) heating to 890-920 °C, with a holding time of 30-60 min, and then gradually cooling to room temperature to complete the sintering connection of the oxide ceramic;

[0029] In step I, the noble metal powder is gold, silver, platinum, or palladium, and in step III, the ceramic to be welded is an oxide ceramic or an easily oxidizable ceramic.

[0030] In step III, the Al2O3 ceramic and the AlN ceramic can also be pre-oxidized only at the connecting interface.

[0031] The high dislocation density and micron-sized noble metal particles in this embodiment can provide a sintering driving force, promote the densification of the metal interlayer, and promote the interdiffusion between the metal and the ceramic matrix, thereby forming a tight bond; the oxide ceramic surface has oxygen vacancies, and the density of the surface oxygen vacancies can be further increased by pre-oxidation. When heated in air, a noble metal-O bond is formed at the noble metal / ceramic interface, which can be embedded in the oxygen vacancies near the surface of the oxide ceramic. This interface bonding further improves the connection strength.

[0032] This embodiment uses a high-energy ball milling and tape casting method to prepare a high-dislocation-density noble metal particle interlayer foil, which is used for sintering connection of oxide or easily oxidizable ceramics. Compared with the pressing method, the high-energy ball milling method obtains a higher dislocation density, and the flexible metal foil prepared by tape casting solves the problem of small size and fragility of the metal sheet prepared by dry pressing. It can be applied to larger areas and more complex ceramic surfaces, and provides the possibility for efficient batch production.

[0033] The method for sintering connection of oxide ceramics using a high-dislocation-density noble metal particle foil in this embodiment mainly has the following beneficial effects: 1. The use of a noble metal interlayer foil for ceramic connection does not react with the two side ceramics, no new phase is generated in the joint, and the high-temperature stability of the joint is enhanced. 2. The high-density dislocation and micron-sized sintering driving force promote the complete densification of the noble metal interlayer, and the joint is good in sealing. 3. Compared with the traditional ceramic connection method, interdiffusion and atomic bonding are achieved at the interface between the noble metal and the ceramic in this method, further improving the mechanical strength of the joint. 4. The flexible noble metal interlayer foil prepared by high-energy ball milling and tape casting can be applied to larger areas and more complex ceramic surfaces, and is easy to realize efficient, fully automated, and batch production.

[0034] The embodiment provides a process for sintering and connecting oxide ceramics in air using high dislocation density noble metal particle foils, which can combine the excellent properties of various ceramic materials together to form an electronic packaging material with excellent comprehensive performance and provide the possibility for high-efficiency batch production.

[0035] Specific embodiment two: different from the specific embodiment one, the noble metal powder is put into a planetary ball mill in step one, the ball-to-material mass ratio is controlled to be 7:1, and the mechanical ball milling time is 10-20 hours.

[0036] Specific embodiment three: different from the specific embodiments one or two, the mass ratio of the noble metal particles, the binder, the solvent and the dispersant in step two is 1:(0.08-0.25):(0.1-0.3):(0.02-0.06).

[0037] Specific embodiment four: different from one of the specific embodiments one to three, the binder in step two is an acrylate resin; the solvent is one or a mixture of multiple of ethanol, isopropanol and ethylene glycol butyl ether; and the dispersant is one or a mixture of multiple of polyacrylic acid, polyvinylpyrrolidone or polyacrylamide.

[0038] Specific embodiment five: different from one of the specific embodiments one to four, the thickness of the noble metal particle interlayer foil in step two is 300-500 μm.

[0039] Specific embodiment six: different from one of the specific embodiments one to five, the oxide ceramic in step three is Al2O3 ceramic, YSZ ceramic, SiO2 ceramic or perovskite oxide ceramic.

[0040] Specific embodiment seven: different from one of the specific embodiments one to six, the easily-oxidized ceramic in step three is AlN ceramic, SiC ceramic, Si3N4 ceramic or MAX phase ceramic (Ti3SiC2, Ti2AlC, Cr2AlC).

[0041] Specific embodiment eight: different from one of the specific embodiments one to seven, the pre-oxidation treatment time in step three is 1h-2.5h.

[0042] Specific embodiment nine: different from one of the specific embodiments one to eight, the temperature rising speed in air in step six is 4-8 ℃ / min.

[0043] Specific embodiment ten: different from one of the specific embodiments one to nine, the temperature decreasing speed after sintering and connection in step six is 10-15 ℃ / min.

[0044] Eleven, the difference between this embodiment and the first to tenth embodiments is that the sintering connection in step four is carried out in air (gradually) to 900-920℃, and the holding time is 30-40 min.

[0045] Example one: the method for sintering and connecting oxide ceramics using high dislocation density noble metal particle foils in air is carried out according to the following steps:

[0046] I. Put silver powder with a particle size of 400 mesh into a planetary ball mill for mechanical ball milling for 20 hours, and the ball-to-material mass ratio is 7:1, to obtain noble metal particles with a particle size of 2 μm;

[0047] II. Mix silver powder, acrylic ester resin, anhydrous ethanol and polyacrylamide according to a mass ratio of 1:0.12:0.1:0.03 to prepare a slurry, and the slurry is cast into a noble metal particle intermediate layer foil with a thickness of 400 μm by a casting machine;

[0048] III. Put Al2O3 ceramic and AlN ceramic into a muffle furnace, heat to 1100℃ in air atmosphere, and pre-oxidize for 2 h, and then cool to room temperature to obtain pre-oxidized ceramics;

[0049] IV. Put the pre-oxidized ceramics into anhydrous ethanol for ultrasonic cleaning for 10 min to obtain cleaned ceramics to be welded;

[0050] V. Stack the ceramics to be welded and the noble metal particle intermediate layer foil according to the order of AlN ceramic / metal particle intermediate layer foil / Al2O3 ceramic from top to bottom, i.e. the metal particle intermediate layer foil is sandwiched between the AlN ceramic and the Al2O3 ceramic, and apply an assembly pressure of 1 MPa to obtain an assembled piece to be welded;

[0051] VI. Put the assembled piece to be welded into a muffle furnace, heat to 920℃ in air at a rate of 5℃ / min, and hold for 30 min for sintering and connection, and cool to room temperature at a rate of 10℃ / min, to complete the sintering and connection of the oxide ceramics.

[0052] The shear strength of the joint obtained in this example is about 85 MPa.

[0053] Figure 1The backscattered images of the AlN / Al2O3 joint obtained at 920℃ / 1MPa / 30min in air using micron-sized silver particle interlayer foil are shown. In this condition, the silver interlayer is fully densified without any voids, and the interfaces on both sides form a dense bond. Because silver has good plasticity, and the ceramic surface is uneven, when a pressure of 1MPa is applied, the silver will embed into the ceramic surface grooves, forming a mechanical interlocking. Figure 2 The enlarged image of the AlN ceramic / silver interface is shown, Figure 3 The enlarged image of the silver / Al2O3 ceramic interface is shown. Because at this temperature, silver does not react with the ceramic on both sides, no reactants are observed at the interface on both sides. The interface connection is tight, without any microvoids or microcracks.

[0054] The present application uses a high dislocation density noble metal particle interlayer foil to sinter and connect ceramics. The noble metal interlayer is fully densified, the interface connection is tight, no new phase is generated, and there are no any microvoids or microcracks. Compared with the traditional ceramic connection method, the present application realizes a joint with better high-temperature stability, sealing performance and higher mechanical strength at a lower temperature. At the same time, the flexible metal foil prepared by flow casting solves the problem of small size and easy breakage of the metal sheet prepared by dry pressing method, and can be applied to larger area and more complex ceramic surfaces, and provides the possibility for high-efficiency batch production.

Claims

1. A method for sintering and bonding oxide ceramics in air using high dislocation density noble metal particle foil, characterized in that... The method for sintering and bonding oxide ceramics in air is carried out according to the following steps:

1. Place the precious metal powder into a planetary ball mill for mechanical ball milling to produce precious metal particles with a particle size of 1-3 μm; 2. The precious metal particles, binder, solvent and dispersant are mixed to form a slurry, and the slurry is cast into a flexible precious metal particle intermediate layer foil strip by a casting molding machine; 3. Place the ceramic to be welded into a muffle furnace and heat it to 1000-1100℃ in an air atmosphere for pre-oxidation treatment, and then cool it to room temperature to obtain the pre-oxidized ceramic. IV. The pre-oxidized ceramic is placed in anhydrous ethanol for ultrasonic cleaning to obtain the cleaned ceramic to be welded.

5. Stack the ceramic and precious metal particles in the intermediate layer foil strip in the order of ceramic to be welded / intermediate layer foil strip / ceramic to be welded, and apply an assembly pressure of 0.8 to 1 MPa to obtain the assembled part to be welded; 6. Place the assembled parts to be welded in a muffle furnace, heat it to 890-920℃ in air, hold it at that temperature for 30-60 minutes for sintering connection, and gradually cool it to room temperature to complete the sintering connection of oxide ceramics. In step one, the precious metal powder is made of gold, silver, platinum, or palladium, and in step three, the ceramic to be welded is an oxide ceramic or an easily oxidized ceramic.

2. The method for sintering and bonding oxide ceramics in air using high dislocation density noble metal particle foil strips according to claim 1, characterized in that... In step one, the precious metal powder is placed in a planetary ball mill, the ball-to-material mass ratio is controlled at 7:1, and the mechanical ball milling time is 10 to 20 hours.

3. The method for sintering and bonding oxide ceramics in air using high dislocation density noble metal particle foil strips according to claim 1, characterized in that... In step two, the mass ratio of precious metal particles, binder, solvent and dispersant is 1:(0.08-0.25):(0.1-0.3):(0.02-0.06).

4. The method for sintering and bonding oxide ceramics in air using high dislocation density noble metal particle foil strips according to claim 1, characterized in that... The adhesive mentioned in step two is an acrylate resin; the solvent is one or more of the following mixed solvents: ethanol, isopropanol, and ethylene glycol butyl ether; and the dispersant is one or more of the following mixed dispersants: polyacrylic acid, polyvinylpyrrolidone, or polyacrylamide.

5. The method for sintering and bonding oxide ceramics in air using high dislocation density noble metal particle foil strips according to claim 1, characterized in that... In step two, the thickness of the intermediate foil strip of the precious metal particles is 300-500 μm.

6. The method for sintering and bonding oxide ceramics in air using high dislocation density noble metal particle foil strips according to claim 1, characterized in that... The oxide ceramic mentioned in step three is Al2O3 ceramic, YSZ ceramic, SiO2 ceramic, or perovskite oxide ceramic.

7. The method for sintering and bonding oxide ceramics in air using high dislocation density noble metal particle foil strips according to claim 1, characterized in that... The easily oxidizable ceramics mentioned in step three are AlN ceramics, SiC ceramics, Si3N4 ceramics, or MAX phase ceramics.

8. The method for sintering and bonding oxide ceramics in air using high dislocation density noble metal particle foil strips according to claim 1, characterized in that... The pre-oxidation treatment time in step three is 1h to 2.5h.

9. The method for sintering and bonding oxide ceramics in air using high dislocation density noble metal particle foil strips according to claim 1, characterized in that... In step six, the heating rate in the air is 4–8 °C / min.

10. The method for sintering and bonding oxide ceramics in air using high dislocation density noble metal particle foil strips according to claim 1, characterized in that... In step four, the temperature is raised to 900-920°C in the air and held for 30-40 minutes for sintering connection.

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