Ceramic and metal heterogeneous connection method

Abstract

The invention relates to a ceramic and metal heterogeneous connection method, which is characterized by comprising the following steps of: 1, covering a metal surface with a metal plating layer; secondly, tungsten slurry or pure molybdenum powder or molybdenum-manganese composite powder is adopted, and a primary metallization layer is formed on the to-be-brazed surface of the ceramic in a high-temperature sintering mode; 3, forming a nickel layer, a nickel-phosphorus layer or a nickel-boron layer, which is called as a secondary metallization layer, with the thickness of less than 20 microns on the surface of the primary metallization layer in a manner of electroplating, evaporation, chemical plating or sintering; 4, attaching a tertiary metallization layer to the surface of the secondary metallization layer in an electroplating manner; fifthly, a ceramic side brazing filler metal layer is formed, and a metal side brazing filler metal layer is formed; and 6, placing a metal middle buffer layer structure in a gap between the ceramic side brazing filler metal layer and the metal side brazing filler metal layer, wherein the main body of the metal middle buffer layer structure is pure nickel, pure copper, pure silver or pure aluminum. According to the method, cracks can be prevented from being generated on the brazing interface, and the sealing performance and the mechanical connection strength of the brazing interface are improved.

Description

Technical Field

[0001] The invention relates to the application field of ceramic-metal connection, and in particular to a method for heterogeneous connection of ceramic and metal. Background Art

[0002] Ceramic materials have excellent properties such as high insulation, high temperature resistance, corrosion resistance, oxidation resistance, high hardness, high strength, and wear resistance, but their plasticity, toughness, and ductility are extremely poor. Once the force exceeds the elastic strain limit (the strain is very small), they will quickly break. Metal materials have excellent mechanical properties such as conductivity, plasticity, toughness, ductility, and weldability, but under harsh working conditions, such as high temperatures above 700°C, the strength and chemical stability of metal materials decrease rapidly. Therefore, in the application scenarios with harsh working conditions such as aviation, military industry, nuclear energy, chemical industry, and machinery, it is the industry's unified understanding and practice to combine the advantages of the two types of materials (i.e., ceramic metal connectors) in a complementary manner, and it is also one of their core technologies. As a method of connecting ceramics and metals, ceramic metal brazing has the advantages of high connection strength, good sealing, high high-temperature chemical stability, simple operation, high welding yield, and good uniformity. It is the mainstream solution for high-strength, high-wear-resistant, and high-temperature service parts in aviation, military industry, nuclear energy, and chemical industry.

[0003] The physical and chemical properties of ceramics and metal materials are very different. First, the thermal expansion coefficients of ceramics and metal materials are usually quite different. During the high-temperature brazing process, huge stress will be generated at the joints, resulting in a rapid decrease in the sealing and connection strength of ceramic and metal connectors. Second, the internal composition and near-surface chemical properties of ceramics and metal materials are quite different. During the high-temperature brazing process, the wetting degree of the brazing material on the ceramic and metal surfaces will be different, which will easily cause uneven distribution of the brazing material and make it impossible to form a continuous, dense, non-porous brazing layer. In addition, during the high-temperature brazing process, the molten brazing material will diffuse elements and combine with metals and ceramics to form compounds. However, due to the large difference and complexity of the composition near the surface of ceramics and metal materials, the inconsistency of the element diffusion degree and path of the brazing material will lead to uneven composition and distribution of the compounds formed on the ceramic and metal surfaces. Summary of the invention

[0004] The object of the present invention is to provide a method for heterogeneous connection between ceramic and metal, which can avoid the generation of cracks at the brazing interface and improve the sealing performance and mechanical connection strength of the brazing interface.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for heterogeneous connection between ceramic and metal, comprising the following steps:

[0007] Step 1: Covering the metal surface with a metal plating layer;

[0008] Step 2: Use tungsten slurry, pure molybdenum powder or molybdenum-manganese composite powder to form a primary metallization layer on the surface of the ceramic to be brazed by high-temperature sintering;

[0009] Step 3: forming a nickel layer, a nickel-phosphorus layer or a nickel-boron layer with a thickness of less than 20 μm on the surface of the primary metallization layer by electroplating, evaporation, chemical plating or sintering, which is called a secondary metallization layer;

[0010] Step 4: attaching a tertiary metallization layer on the surface of the secondary metallization layer by electroplating, wherein the main component of the tertiary metallization layer is pure copper, pure nickel, pure silver, pure gold, pure aluminum, copper-gold alloy, nickel-silver alloy or nickel-gold alloy, and the thickness of the tertiary metallization layer is 20 μm-100 μm;

[0011] Step 5: Degreasing and decontaminating the metal and ceramic, drying and cooling, applying a certain amount of solder on the surface of the tertiary metallization layer to form a ceramic side solder layer, and applying a certain amount of solder on the surface of the metal plating layer to form a metal side solder layer;

[0012] Step 6: Assemble the metal and the ceramic, and place a metal intermediate buffer layer structure in the gap between the ceramic side solder layer and the metal side solder layer, so that the ceramic side solder layer and the metal side solder layer jointly clamp the metal intermediate buffer layer structure to form a metal-ceramic assembly, wherein the main body of the metal intermediate buffer layer structure is pure nickel, pure copper, pure silver or pure aluminum, and a plating layer with the same composition as the tertiary metallization layer is attached to the surface of the main body, and the metal intermediate buffer layer structure is a sheet, mesh or porous structure;

[0013] Step 7: Place the metal-ceramic assembly into a brazing furnace, evacuate the furnace, then heat it to 400-500°C and keep it for 15-20 minutes, then heat it to 1100-1200°C and keep it for 5-10 minutes, and finally cool it down to room temperature along with the furnace.

[0014] Specifically, the metal is a 310S stainless steel tube, the ceramic is an alumina ceramic tube, a countersunk hole is opened at the end of the 310S stainless steel tube, and the alumina ceramic tube is matched with the countersunk hole.

[0015] Specifically, the brazing filler metal is BNi5, and the metal plating layer is pure nickel.

[0016] Specifically, in step 2, the high temperature sintering temperature is 1300°C-1800°C.

[0017] Specifically, in step seven, the brazing furnace is evacuated to a vacuum degree of 10 -4 -10 -5 pa.

[0018] Specifically, in step seven, the temperature is increased to 450° C. at a heating rate of 5° C. / min and kept at this temperature for 15-20 min, and then the temperature is increased to 1150° C. and kept at this temperature for 5-10 min.

[0019] Specifically, after completing step seven, a protective layer is formed on the exposed surface of the brazing seam by spraying, brushing or brazing.

[0020] Specifically, the protective layer is glass glue, ceramic glue or active solder.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. This method can form a ceramic surface buffer layer (tertiary metallization layer) and an intermediate buffer layer (metal intermediate buffer layer structure). The cooperation of the two in different spaces and layers can effectively absorb the thermal stress generated by the difference in thermal expansion coefficients between ceramics and metals during brazing, thereby avoiding the generation of cracks at the brazing interface.

[0023] Second, by constructing a layer of the same coating (pure nickel in this embodiment) on the surface of the ceramic, metal, and intermediate buffer layer (metal intermediate buffer layer structure), the ceramic, metal, and intermediate buffer layer (metal intermediate buffer layer structure) have the same composition and interface chemical properties, thereby reducing the difference in wettability of the solder on each component and the difference in the degree of diffusion of the solder element into each component, which helps to form a uniform, continuous, non-porous solder layer (ceramic side solder layer and metal side solder layer) between the surfaces of the ceramic, metal, and intermediate buffer layer (metal intermediate buffer layer structure) to improve the sealing and mechanical connection strength of the soldering interface. In addition, the coating is similar to the solder in composition and has good interface compatibility with the solder, which can effectively guide the uniform fluidity of the solder in the molten state, and plays an important role in the construction of a non-porous solder layer.

[0024] 3. Construct a protective layer at the brazing joint of the brazed metal-ceramic assembly. The protective layer is glass glue, ceramic glue or active brazing material. The protective layer can prevent the molybdenum-manganese layer or the brazing material layer at the brazing joint from being eroded by oxygen, water vapor or other special gases in a harsh use environment for a long time, thereby increasing the service life of the ceramic-metal assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1This is a view before the stainless steel tube and the alumina ceramic tube are combined;

[0027] Figure 2 This is a view of a stainless steel tube and an alumina ceramic tube combined;

[0028] Figure 3 Schematic diagram of the structure of each layer at the brazing point.

[0029] In the figure:

[0030] 1. Ceramic; 2. Primary metallization layer; 3. Secondary metallization layer; 4. Tertiary metallization layer; 5. Ceramic side solder layer; 6. Metal intermediate buffer layer structure; 7. Metal side solder layer; 8. Metal plating layer; 9. Metal; 10. Protective layer. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0032] See Figure 1 In this embodiment, the metal 9 is a 310S stainless steel tube, and the ceramic 1 is an alumina ceramic tube. A countersunk hole is opened at the end of the 310S stainless steel tube, and the alumina ceramic tube cooperates with the countersunk hole. As an alternative embodiment: the metal 9 can be a kovar alloy, a nickel-based high-temperature alloy, etc.; the ceramic 1 can be a silicon carbide ceramic, a zirconium oxide ceramic, etc.

[0033] The method for heterogeneous connection between ceramic and metal in this embodiment comprises the following steps:

[0034] Step 1: Plate a metal coating 8 on the surface of the metal 9. In this embodiment, BNi5 is selected as the solder, and BNi5 contains more than 70% nickel, so the metal coating 8 is pure nickel, and the melting point of pure nickel is not lower than the solder BNi5.

[0035] Step 2: Use tungsten slurry, pure molybdenum powder or molybdenum-manganese composite powder to form a primary metallization layer 2 on the surface of the ceramic 1 to be brazed by high-temperature sintering. The primary metallization layer 2 and the surface of the ceramic 1 to be brazed interpenetrate each other, thereby improving the adhesion firmness of the primary metallization layer 2. The construction of the primary metallization layer 2 can change the chemical properties of the surface of the ceramic 1, so that the surface of the ceramic 1 is transformed from a non-metallic surface to a metallic surface.

[0036] Step 3: A nickel layer, a nickel-phosphorus layer or a nickel-boron layer having a thickness of less than 20 μm is formed on the surface of the primary metallization layer 2 by electroplating, evaporation, chemical plating or sintering, which is called the secondary metallization layer 3. The secondary metallization layer 3 can protect the primary metallization layer 2 from being corroded by the solder during the subsequent brazing process, and can improve the wettability and bonding strength with the solder.

[0037] Step 4: A tertiary metallization layer 4 is attached to the surface of the secondary metallization layer 3 by electroplating. The main components of the tertiary metallization layer 4 are pure copper, pure nickel, pure silver, pure gold, pure aluminum, copper-gold alloy, nickel-silver alloy or nickel-gold alloy. The main component of the tertiary metallization layer 4 is determined according to the main component of the solder selected later. In this embodiment, BNi5 is selected as the solder, so the main component of the tertiary metallization layer 4 is pure nickel. The tertiary metallization layer 4 constructs a metal layer (pure nickel) with a composition similar to that of the solder (BNi5) and a melting point not lower than that of the solder on the surface of the secondary metallization layer 3, so as to improve the compatibility with the solder in the subsequent brazing process and the consistency of the properties of the brazing interface, thereby helping to form a uniform and dense brazing layer.

[0038] The tertiary metallization layer 4 has a certain thickness, which is between 20-100 μm. Its purpose is to construct an elastic buffer layer on the surface of the ceramic 1 to absorb the thermal stress generated during the brazing process, slow down the generation of thermal cracks on the ceramic 1 interface and improve the mechanical stability of the ceramic 1 interface.

[0039] Step 5: Degrease and decontaminate the metal 9 and the ceramic 1, dry and cool them, and then apply a certain amount of BNi5 solder on the surface of the tertiary metallization layer 4 (in this embodiment, the tertiary metallization layer 4 is pure nickel) to form a ceramic side solder layer 5, and apply a certain amount of solder on the surface of the metal plating layer 8 (in this embodiment, the metal plating layer 8 is pure nickel) to form a metal side solder layer 7.

[0040] Step 6: Assemble the metal 9 and the ceramic 1, and place a metal intermediate buffer layer structure 6 in the gap between the ceramic side solder layer 5 and the metal side solder layer 7 (refer to Figure 3 ), so that the ceramic side brazing material layer 5 and the metal side brazing material layer 7 together sandwich the metal intermediate buffer layer structure 6 to form a metal-ceramic assembly (such as Figure 2 In this embodiment, the main body of the metal intermediate buffer layer structure 6 is pure nickel. As an alternative embodiment, the main body of the metal intermediate buffer layer structure 6 can be pure copper, pure silver or pure aluminum. The surface of the main body is attached with a plating layer with the same composition as the third metallization layer 4. The metal intermediate buffer layer structure 6 is a sheet, mesh or porous structure.

[0041] The metal intermediate buffer layer structure 6 having a certain thickness serves as a buffer layer. By spatially cooperating with the tertiary metallization layer 4 which also serves as a buffer layer, it can absorb thermal stress in the subsequent brazing process and improve the stability of the brazing interface.

[0042] Step 7: Place the metal-ceramic assembly into a brazing furnace, evacuate the furnace, then heat it to 400-500°C and keep it for 15-20 minutes, then heat it to 1100-1200°C and keep it for 5-10 minutes, and finally cool it down to room temperature along with the furnace.

[0043] Step 8: See Figure 3 A protective layer 10 is formed on the exposed surface of the brazing joint by spraying, brushing or brazing. The protective layer 10 is glass glue, ceramic glue or active brazing material. The protective layer 10 can prevent the molybdenum manganese layer or the brazing material layer at the brazing joint from being corroded by oxygen, water vapor or other special gases in a harsh use environment for a long time, thereby improving the service life of the ceramic metal assembly.

[0044] Specifically, in step 2, the high temperature sintering temperature is 1300°C-1800°C.

[0045] Specifically, in step seven, the brazing furnace is evacuated to a vacuum degree of 10 -4 -10 -5 pa.

[0046] Specifically, in step seven, the temperature is increased to 450° C. at a heating rate of 5° C. / min and kept at this temperature for 15-20 min, and then the temperature is increased to 1150° C. and kept at this temperature for 5-10 min.

[0047] Alternatively, the solder may be silver-based solder, copper-based solder, aluminum-based solder, gold-based solder, etc., and the solder may be in the form of paste, foil or wire. The solder may be used as a connecting material to connect ceramic and metal base materials by vacuum brazing or atmosphere brazing.

[0048] Correspondingly, the metal plating layer 8 can be pure copper, pure nickel, pure silver, pure gold, pure aluminum, etc. Its specific composition is determined according to the composition of the solder. Its purpose is to construct a metal layer on the surface of the metal 9 with a composition similar to that of the solder to improve the interface compatibility with the solder.

[0049] The beneficial effects of the present invention are as follows:

[0050] 1. This method can form a ceramic surface buffer layer (tertiary metallization layer 4) and an intermediate buffer layer (metal intermediate buffer layer structure 6). The cooperation of the two in different spaces and layers can effectively absorb the thermal stress generated by the difference in thermal expansion coefficients during the brazing process between the ceramic 1 and the metal 9, thereby avoiding the generation of cracks at the brazing interface;

[0051] Second, by constructing a layer of the same type of coating (pure nickel in this embodiment) on the surface of the ceramic 1, the surface of the metal 9, and the surface of the intermediate buffer layer (metal intermediate buffer layer structure 6), the surface of the ceramic 1, the surface of the metal 9, and the intermediate buffer layer (metal intermediate buffer layer structure 6) have the same composition and interface chemical properties, thereby reducing the difference in wettability of the solder on each component and the difference in the degree of diffusion of the solder element into each component, which helps to form a uniform, continuous, non-porous solder layer (ceramic side solder layer 5 and metal side solder layer 7) between the surfaces of the ceramic 1, the metal 9 and the intermediate buffer layer (metal intermediate buffer layer structure 6) to improve the sealing and mechanical connection strength of the soldering interface. In addition, the coating is similar to the solder in composition and has good interface compatibility with the solder, which can effectively guide the uniform fluidity of the solder in the molten state, and plays an important role in the construction of a non-porous solder layer.

[0052] 3. A protective layer 10 is constructed at the brazing joint of the brazed metal-ceramic assembly. The protective layer 10 is glass glue, ceramic glue or active brazing material. The protective layer 10 can prevent the molybdenum-manganese layer or the brazing material layer at the brazing joint from being corroded by oxygen, water vapor or other special gases in a harsh use environment for a long time, thereby improving the service life of the ceramic-metal assembly.

[0053] The above are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. Although the present invention has been disclosed as above in the form of preferred embodiments, it is not intended to limit the present invention. Any technical personnel in the field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for heterogeneous connection between ceramic and metal, characterized in that: The following steps are involved: Step 1: Covering the metal surface with a metal plating layer; Step 2: Use tungsten slurry, pure molybdenum powder or molybdenum-manganese composite powder to form a primary metallization layer on the surface of the ceramic to be brazed by high-temperature sintering; Step 3: forming a nickel layer, a nickel-phosphorus layer or a nickel-boron layer with a thickness of less than 20 μm on the surface of the primary metallization layer by electroplating, evaporation, chemical plating or sintering, which is called a secondary metallization layer; Step 4: attaching a tertiary metallization layer on the surface of the secondary metallization layer by electroplating, wherein the main component of the tertiary metallization layer is pure copper, pure nickel, pure silver, pure gold, pure aluminum, copper-gold alloy, nickel-silver alloy or nickel-gold alloy, and the thickness of the tertiary metallization layer is 20 μm-100 μm; Step 5: Degreasing and decontaminating the metal and ceramic, drying and cooling, applying a certain amount of solder on the surface of the tertiary metallization layer to form a ceramic side solder layer, and applying a certain amount of solder on the surface of the metal plating layer to form a metal side solder layer; Step 6: Assemble the metal and the ceramic, and place a metal intermediate buffer layer structure in the gap between the ceramic side solder layer and the metal side solder layer, so that the ceramic side solder layer and the metal side solder layer jointly clamp the metal intermediate buffer layer structure to form a metal-ceramic assembly, wherein the main body of the metal intermediate buffer layer structure is pure nickel, pure copper, pure silver or pure aluminum, and a plating layer with the same composition as the tertiary metallization layer is attached to the surface of the main body, and the metal intermediate buffer layer structure is a sheet, mesh or porous structure; Step 7: Place the metal-ceramic assembly into a brazing furnace, evacuate the furnace, then heat it to 400-500°C and keep it for 15-20 minutes, then heat it to 1100-1200°C and keep it for 5-10 minutes, and finally cool it down to room temperature along with the furnace.

2. The method for heterogeneous connection of ceramic and metal according to claim 1, characterized in that: The metal is a 310S stainless steel tube, and the ceramic is an alumina ceramic tube. A countersunk hole is opened at the end of the 310S stainless steel tube, and the alumina ceramic tube is matched with the countersunk hole.

3. The method for heterogeneous connection of ceramic and metal according to claim 1, characterized in that: The brazing filler metal is BNi5 and the metal plating layer is pure nickel.

4. The method for heterogeneous connection of ceramic and metal according to claim 1, characterized in that: In step 2, the high temperature sintering temperature is 1300°C-1800°C.

5. The method for heterogeneous connection of ceramic and metal according to claim 1, characterized in that: In step 7, the brazing furnace is evacuated to a vacuum degree of 10 -4 -10 -5 pa.

6. The method for heterogeneous connection of ceramic and metal according to claim 1, characterized in that: In step seven, the temperature is increased to 450°C at a heating rate of 5°C / min and kept at this temperature for 15-20 minutes, and then the temperature is increased to 1150°C and kept at this temperature for 5-10 minutes.

7. The method for heterogeneous connection of ceramic and metal according to claim 1, characterized in that: After completing step seven, a protective layer is formed on the exposed surface of the brazing seam by spraying, brushing or brazing.

8. The method for heterogeneous connection of ceramic and metal according to claim 7, characterized in that: The protective layer is glass glue, ceramic glue or active solder.

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