Method for ferrite ceramic metallization and brazing

Abstract

The application provides a ferrite ceramic metallization and brazing method, which comprises the following steps: mixing BaCO3 powder, SiO2 powder, CaO powder, MgO powder and Al2O3 powder, calcining the mixture at 1300-1400 DEG C for 1-2 hours, taking out the mixture, and then sequentially performing water quenching and grinding to obtain a low-temperature eutectic; mixing Ag powder, CuO powder and the low-temperature eutectic, grinding the mixture, and then preparing a paste with organic matter; coating the paste on the surface of the ferrite ceramic, drying, and then performing two-stage calcining, and finally naturally cooling to room temperature to obtain metallized ferrite ceramic; and brazing the metallized ferrite ceramic, solder and metal assembly. In the metallization sintering process, the inorganic oxide is metallized to form a metallized layer, and the metallized layer can work at high temperature above 800 DEG C for a long time after sintering with Ag; the metallized layer can resist corrosion of silver-based solder and commonly used low-temperature solder, and effectively realizes brazing of the metallized ferrite ceramic and the metal.

Description

Technical Field

[0001] This application belongs to the field of ceramic and dissimilar material joining technology, and more specifically, relates to a method for metallizing and brazing ferrite ceramics. Background Technology

[0002] Ferrite materials, due to their excellent electromagnetic loss and high-frequency characteristics, can effectively attenuate or absorb radio frequency energy. Ferrite ceramics have been widely used in various microwave applications in modern radar, communications, and electronic warfare. Due to limitations in the integrated manufacturing process of ferrite ceramics, reliable connection technology has become a necessary and important approach to solving this problem.

[0003] To date, research on ferrite bonding is very limited. Intermediate layers commonly used for bonding ceramic materials include adhesives, glass solders, and metal-based solders. The former two involve directly bonding ferrite to other materials using epoxy resin-containing colloids and glass solders, respectively. Metal-based solders, on the other hand, involve forming a firmly bonded metal film on the surface of the ferrite ceramic using a specific process; this process is called ceramic metallization. Common metallization methods include thin-film methods (sputtering multiple thin metal films), high-temperature sintering with silver plating, chemical plating, and electroplating. This gives the ferrite ceramic surface metallic weldability, allowing the ferrite to be welded to other metals using metal solders.

[0004] While adhesive bonding is simple and uses readily available materials, it suffers from drawbacks such as poor high-temperature resistance, susceptibility to aging, low strength, poor thermal conductivity, and a tendency to vent, which can negatively impact microwave devices with long service lives. Glass solder itself has poor thermal conductivity, meaning that the absorbed heat cannot be effectively dissipated when used as a microwave absorber; furthermore, glass solder is a brittle material with low strength, making it prone to breakage. These limitations significantly restrict its application. Magnetron sputtering of metal films involves pre-metallizing the ferrite and then welding it to a metal material using solder. However, magnetron sputtering is a complex process with high production costs.

[0005] The silvering process involves mixing silver powder and a small amount of glass powder with an organic carrier to form a paste, which is then printed onto the ceramic surface and sintered in a furnace at a temperature of around 800°C. The silvering process mainly utilizes the diffusion of silver to generate physical adsorption on the surface of ferrite ceramics, but the bonding force is usually relatively weak. Summary of the Invention

[0006] The technical problem this invention aims to solve is the aforementioned issues inherent in existing ferrite bonding methods, particularly the problem that the silver-bonded method, which produces physical adsorption, typically results in weak bonding forces. This invention improves upon the silver-bonded method by adding inorganic oxides to generate a glassy metal oxide layer. This metal oxide layer and the ferrite ceramic form a strong bond, which helps to improve the bonding strength and thermal conductivity.

[0007] The purpose of this invention is to provide a method for metallizing and brazing ferrite ceramics, comprising:

[0008] BaCO3 powder, SiO2 powder, CaO powder, MgO powder and Al2O3 powder are mixed and calcined at 1300-1400℃ for 1-2 hours. The mixture is then removed and subjected to water quenching and grinding to obtain a low-temperature eutectic.

[0009] Ag powder, CuO powder, and low-temperature eutectic are mixed and ground together with organic matter to form a paste. The paste is then coated onto the surface of a ferrite ceramic, dried, and subjected to two stages of calcination. The first stage of calcination is carried out at a temperature of 300–380°C for 25–35 min, and the second stage of calcination is carried out at a temperature of 950–1100°C for 20–40 min. Finally, the ceramic is allowed to cool naturally to room temperature to obtain a metallized ferrite ceramic.

[0010] The metallized ferrite ceramics, solder, and metal assemblies are brazed.

[0011] As one possible design, the mass percentages of Ag powder, CuO powder, and low-temperature eutectic in the paste are 70–90%, 4–7%, and 3–25%, respectively.

[0012] As one possible design, the mass percentages of BaCO3 powder, SiO2 powder, and CaO powder in the low-temperature eutectic are 30-40%, 30-50%, and 10-20%, respectively; the sum of the mass percentages of MgO powder and Al2O3 powder is 5-10%.

[0013] As one possible design, the heating rate in the first stage of the calcination process is 8–10 °C / min, and the heating rate in the second stage is 6–10 °C / min.

[0014] As one possible design, the cooling is divided into two stages: the first stage cools the temperature to 450-550°C at a rate of 5-10°C / min, and the second stage allows it to cool naturally to room temperature.

[0015] As one possible design, the thickness of the ferrite ceramic surface paste is 40–100 μm.

[0016] As one possible design, the paste is ball-milled on a planetary ball mill for 6 to 10 hours before being applied to the ferrite ceramic surface.

[0017] As one possible design, the solder can be silver-copper solder, silver-copper-nickel solder, gold-tin solder, tin-silver-copper solder, or tin-lead solder. The metal is the material that bonds to the metallized ferrite ceramic, such as copper, iron, aluminum, or other metallic elements.

[0018] As one possible design, brazing is performed in a vacuum furnace or a reflow oven.

[0019] The beneficial effects of this invention are as follows:

[0020] The inorganic oxides added in this invention, such as CuO, Al2O3, SiO2, CaO, B2O3, and BaCO3, form a CaO-BaO-SiO2 glassy phase during the metallization sintering process. CuO also reacts with the ferrite ceramic, effectively wetting it and forming a good bond, which helps improve the bonding strength and thermal conductivity. More importantly, the metallization layer formed by Ag and these inorganic oxides can operate at temperatures above 800°C for extended periods after sintering. The metallization layer is resistant to corrosion from silver-based solders and commonly used low-temperature solders, effectively enabling brazing of the metallized ferrite ceramic to the metal. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a microstructure diagram of the metallized ferrite ceramic surface obtained in Example 1 of the present invention;

[0023] Figure 2 This is a microstructure diagram of the ferrite ceramic-copper joint obtained by welding the metallized ferrite ceramic with SnAgCu solder in Example 1 of the present invention.

[0024] Figure 3 This is a microstructure diagram of the ferrite ceramic-copper joint obtained by welding the metallized ferrite ceramic obtained in Comparative Example 1 of the present invention using SnAgCu solder.

[0025] Figure 4 This is a microstructure diagram of the ferrite ceramic-copper joint obtained by welding the metallized ferrite ceramic obtained in Comparative Example 2 of the present invention using SnAgCu solder. Detailed Implementation

[0026] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0027] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0028] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0029] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0030] Example 1

[0031] (A) Preparation of metallizing paste.

[0032] 1. Take 35 parts of BaCO3 powder, 45 parts of SiO2 powder, 12 parts of CaO powder, 3 parts of Al2O3 powder, and 5 parts of MgO powder. Put all the raw materials into a ball mill jar, mix and ball mill for 5 hours. Then take them out and put them into a crucible for high-temperature calcination at 1400℃ for 2 hours. Take them out and quench them in water and grind them in turn to obtain a low-temperature eutectic.

[0033] 2. Take 75 parts of Ag powder, 5 parts of CuO powder, and 20 parts of low-temperature eutectic to obtain a mixed powder; the average particle size of Ag powder is 2 μm, and the average particle size of the other powders is 5 μm.

[0034] 3. Place the mixed powder in a ball mill jar for mixing, and ball mill it on a planetary ball mill for 8 hours to obtain the ground powder.

[0035] 4. Mix the ground powder with terpineol to form a paste.

[0036] (B) Metallization sintering.

[0037] 1. Apply the above-obtained paste to the surface of the ferrite ceramic with a coating thickness of 60 μm. After coating, place the ferrite ceramic in an oven at 110°C and keep it warm for 30 minutes to dry.

[0038] 2. After drying, metallization sintering is carried out in a muffle furnace. First, the temperature is raised to 350℃ at a heating rate of 10℃ / min, then held for 30 min, and then raised to 1000℃ at a heating rate of 8℃ / min and held for 40 min. Subsequently, the temperature is lowered to 500℃ at a cooling rate of 8℃ / min, and finally cooled to room temperature in the furnace to obtain the metallized ferrite ceramic.

[0039] (C) Brazing. The metallized ferrite ceramic is assembled with metallized oxide ceramic, silver-copper solder, and metal and then brazed in a vacuum furnace.

[0040] Example 2

[0041] (A) Preparation of metallizing paste.

[0042] 1. Take 35 parts of BaCO3 powder, 45 parts of SiO2 powder, 12 parts of CaO powder, 3 parts of Al2O3 powder, and 5 parts of MgO powder. Put all the raw materials into a ball mill jar, mix and ball mill for 3 hours. Then take them out and put them into a crucible for high-temperature calcination at 1300℃ for 2 hours. Take them out and quench them in water and grind them in turn to obtain a low-temperature eutectic.

[0043] 2. Take 85 parts of Ag powder, 6 parts of CuO powder, and 9 parts of low-temperature eutectic to obtain a mixed powder; the average particle size of Ag powder is 5 μm, and the average particle size of the other powders is 10 μm.

[0044] 3. Place the mixed powder in a ball mill jar for mixing, and ball mill it on a planetary ball mill for 8 hours to obtain the ground powder.

[0045] 4. Mix the ground powder with terpineol to form a paste.

[0046] (B) Metallization sintering.

[0047] 1. Apply the above-obtained paste to the surface of the ferrite ceramic with a coating thickness of 80 μm. After coating, place the ferrite ceramic in an oven at 110°C and keep it warm for 40 minutes to dry.

[0048] 2. After drying, metallization sintering is carried out in a muffle furnace. First, the temperature is raised to 350℃ at a heating rate of 10℃ / min, then held for 30 min, and then raised to 1050℃ at a heating rate of 6℃ / min and held for 30 min. Subsequently, the temperature is lowered to 500℃ at a cooling rate of 6℃ / min, and finally cooled to room temperature in the furnace to obtain the metallized ferrite ceramic.

[0049] (C) Brazing. The metallized ferrite ceramic is assembled with metallized oxide ceramic, silver-copper solder, and metal and then brazed in a vacuum furnace.

[0050] Example 3

[0051] (A) Preparation of metallizing paste.

[0052] 1. Take 40 parts of BaCO3 powder, 38 parts of SiO2 powder, 15 parts of CaO powder, 2 parts of Al2O3 powder, and 5 parts of MgO powder. Put all the raw materials into a ball mill jar, mix and ball mill for 5 hours. Then take them out and put them into a crucible for high-temperature calcination at 1400℃ for 2 hours. Take them out and quench them in water and grind them in turn to obtain a low-temperature eutectic.

[0053] 2. Take 75 parts of Ag powder, 5 parts of CuO powder, and 20 parts of low-temperature eutectic to obtain a mixed powder; the average particle size of Ag powder is 2 μm, and the average particle size of the other powders is 5 μm.

[0054] 3. Place the mixed powder in a ball mill jar for mixing, and ball mill it on a planetary ball mill for 8 hours to obtain the ground powder.

[0055] 4. Mix the ground powder with terpineol to form a paste.

[0056] (B) Metallization sintering.

[0057] 1. Apply the above-obtained paste to the surface of the ferrite ceramic with a coating thickness of 60 μm. After coating, place the ferrite ceramic in an oven at 110°C and keep it warm for 30 minutes to dry.

[0058] 2. After drying, metallization sintering is carried out in a muffle furnace. First, the temperature is raised to 350℃ at a heating rate of 10℃ / min, then held for 30 min, and then raised to 1000℃ at a heating rate of 8℃ / min and held for 40 min. Subsequently, the temperature is lowered to 500℃ at a cooling rate of 8℃ / min, and finally cooled to room temperature in the furnace to obtain the metallized ferrite ceramic.

[0059] (C) Brazing. The metallized ferrite ceramic is assembled with metallized oxide ceramic, silver-copper solder, and metal and then brazed in a vacuum furnace.

[0060] Example 4

[0061] (A) Preparation of metallizing paste.

[0062] 1. Take 35 parts of BaCO3 powder, 45 parts of SiO2 powder, 12 parts of CaO powder, 3 parts of Al2O3 powder, and 5 parts of MgO powder. Put all the raw materials into a ball mill jar, mix and ball mill for 4.5 hours. Then take them out and put them into a crucible for high-temperature calcination at 1400℃ for 2 hours. Take them out and quench them in water and grind them in turn to obtain a low-temperature eutectic.

[0063] 2. Take 75 parts of Ag powder, 5 parts of CuO powder, and 20 parts of low-temperature eutectic to obtain a mixed powder; the average particle size of Ag powder is 2 μm, and the average particle size of the other powders is 5 μm.

[0064] 3. Place the mixed powder in a ball mill jar for mixing, and ball mill it on a planetary ball mill for 8 hours to obtain the ground powder.

[0065] 4. Mix the ground powder with terpineol to form a paste.

[0066] (B) Metallization sintering.

[0067] 1. Apply the above-obtained paste to the surface of the ferrite ceramic with a coating thickness of 60 μm. After coating, place the ferrite ceramic in an oven at 110°C and keep it warm for 30 minutes to dry.

[0068] 2. After drying, metallization sintering is carried out in a muffle furnace. First, the temperature is raised to 350℃ at a heating rate of 10℃ / min, then held for 30 min, and then raised to 1050℃ at a heating rate of 8℃ / min and held for 40 min. Subsequently, the temperature is lowered to 500℃ at a cooling rate of 8℃ / min, and finally cooled to room temperature in the furnace to obtain the metallized ferrite ceramic.

[0069] (C) Brazing. The metallized ferrite ceramic is assembled with metallized oxide ceramic, silver-copper solder, and metal and then brazed in a vacuum furnace.

[0070] Comparative Example 1

[0071] (A) Preparation of metallizing paste.

[0072] 1. Take 100 parts of Ag powder, the average particle size of which is 2μm.

[0073] 2. Place Ag powder in a ball mill jar for mixing, and ball mill on a planetary ball mill for 8 hours to obtain the ground powder.

[0074] 3. Mix the ground Ag powder and terpineol to form a paste.

[0075] (B) Metallization sintering.

[0076] 1. Apply the above-obtained paste to the surface of the ferrite ceramic with a coating thickness of 60 μm. After coating, place the ferrite ceramic in an oven at 110°C and keep it warm for 30 minutes to dry.

[0077] 2. After drying, metallization sintering is carried out in a muffle furnace. First, the temperature is raised to 350℃ at a heating rate of 10℃ / min, then held for 30 min, and then raised to 1000℃ at a heating rate of 8℃ / min and held for 40 min. Subsequently, the temperature is lowered to 500℃ at a cooling rate of 8℃ / min, and finally cooled to room temperature in the furnace to obtain the metallized ferrite ceramic.

[0078] (C) Brazing. The metallized ferrite ceramic is assembled with metallized oxide ceramic, silver-copper solder, and metal and then brazed in a vacuum furnace.

[0079] The bonding force between the metallization layer and the ferrite ceramic is poor, such as Figure 3 As shown.

[0080] Comparative Example 2

[0081] (A) Preparation of metallizing paste.

[0082] 1. Take 35 parts of BaCO3 powder, 45 parts of SiO2 powder, 12 parts of CaO powder, 3 parts of Al2O3 powder, and 5 parts of MgO powder. Put all the raw materials into a ball mill jar, mix and ball mill for 4.5 hours. Then take them out and put them into a crucible for high-temperature calcination at 1400℃ for 2 hours. Take them out and quench them in water and grind them in turn to obtain a low-temperature eutectic.

[0083] 2. Take 75 parts of Ag powder, 5 parts of CuO powder, and 20 parts of low-temperature eutectic to obtain a mixed powder; the average particle size of Ag powder is 2 μm, and the average particle size of the other powders is 5 μm.

[0084] 3. Place the mixed powder in a ball mill jar for mixing, and ball mill it on a planetary ball mill for 8 hours to obtain the ground powder.

[0085] 4. Mix the ground powder with terpineol to form a paste.

[0086] (B) Metallization sintering.

[0087] 1. Apply the above-obtained paste to the surface of the ferrite ceramic with a coating thickness of 60 μm. After coating, place the ferrite ceramic in an oven at 110°C and keep it warm for 30 minutes to dry.

[0088] 2. After drying, metallization sintering is carried out in a muffle furnace. First, the temperature is raised to 350℃ at a heating rate of 10℃ / min, then held for 30 min, and then raised to 600℃ at a heating rate of 8℃ / min and held for 40 min; then the temperature is lowered to 500℃ at a cooling rate of 8℃ / min, and finally cooled to room temperature in the furnace to obtain the metallized ferrite ceramic.

[0089] (C) Brazing. The metallized ferrite ceramic is assembled with metallized oxide ceramic, silver-copper solder, and metal and then brazed in a vacuum furnace.

[0090] The reaction temperature between the metallization layer and the ferrite ceramic is low, resulting in poor adhesion. Figure 4 As shown.

[0091] The metallized ferrite ceramic obtained in Example 1 was then observed under a microscope, and the results are as follows: Figure 1 As shown, by Figure 1 It can be seen that the metallization layer and the ferrite ceramic are tightly bonded together, indicating that the two have good bonding performance.

[0092] The microstructure of the ferrite ceramic-copper joint obtained by welding the metallized ferrite ceramic obtained in Example 1 with SnAgCu solder is as follows: Figure 2 As shown, by Figure 2 It is evident that the metal oxide layer and the solder are well bonded, therefore the metallized ferrite ceramic prepared by this invention is worthy of widespread use in the welding field.

[0093] In summary, the inorganic oxides such as CuO, Al2O3, SiO2, CaO, B2O3, and BaCO3 added in this invention form a CaO-BaO-SiO2 glassy phase during the metallization sintering process. CuO also reacts with the ferrite ceramic, effectively wetting it and forming a good bond, which helps improve the bonding strength and thermal conductivity. More importantly, the metallization layer formed by Ag and these inorganic oxides can operate at temperatures above 800°C for extended periods after sintering. The metallization layer can withstand the corrosion of silver-based solders and commonly used low-temperature solders, effectively enabling brazing of the metallized ferrite ceramic to the metal.

[0094] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for metallizing and brazing ferrite ceramics, characterized in that, The method includes: BaCO3 powder, SiO2 powder, CaO powder, MgO powder and Al2O3 powder are mixed and calcined at 1300-1400℃ for 1-2 hours. The mixture is then removed and subjected to water quenching and grinding to obtain a low-temperature eutectic. Ag powder, CuO powder, and low-temperature eutectic are mixed and ground together with organic matter to form a paste. The paste is then coated onto the surface of a ferrite ceramic, dried, and subjected to two stages of calcination. The first stage of calcination is carried out at a temperature of 300–380°C for 25–35 min, and the second stage of calcination is carried out at a temperature of 950–1100°C for 20–40 min. Finally, the ceramic is allowed to cool naturally to room temperature to obtain a metallized ferrite ceramic. Brazing of metallized ferrite ceramics, solder and metal assemblies; The mass percentages of BaCO3 powder, SiO2 powder, and CaO powder in the low-temperature eutectic are 30-40%, 30-50%, and 10-20%, respectively; the sum of the mass percentages of MgO powder and Al2O3 powder is 5-10%.

2. The method for metallizing and brazing ferrite ceramics according to claim 1, characterized in that, The mass percentages of Ag powder, CuO powder, and low-temperature eutectic in the paste are 70–90%, 4–7%, and 3–25%, respectively.

3. The method for metallizing and brazing ferrite ceramics according to claim 1, characterized in that, During the calcination process, the heating rate in the first stage is 8–10 °C / min, and the heating rate in the second stage is 6–10 °C / min.

4. The method for metallizing and brazing ferrite ceramics according to claim 1, characterized in that, The cooling process is divided into two stages. In the first stage, the temperature is reduced to 450-550℃ at a rate of 5-10℃ / min. In the second stage, the temperature is naturally cooled to room temperature.

5. The method for metallizing and brazing ferrite ceramics according to claim 1, characterized in that, The thickness of the paste on the ferrite ceramic surface is 40–100 μm.

6. The method for metallizing and brazing ferrite ceramics according to claim 1, characterized in that, Before applying the paste to the ferrite ceramic surface, ball mill it for 6 to 10 hours on a planetary ball mill.

7. The method for metallizing and brazing ferrite ceramics according to claim 1, characterized in that, The solder is silver-copper solder, silver-copper-nickel solder, gold-tin solder, tin-silver-copper solder, or tin-lead solder.

8. The brazing method for metallized ferrite ceramics according to claim 1, characterized in that, Brazing is performed in a vacuum furnace or reflow oven.

9. A metallized ferrite ceramic obtained by the method according to any one of claims 1 to 8.

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