A method for preparing an active metal brazing substrate

Abstract

This invention discloses a method for preparing an active metal brazing substrate, relating to the field of brazing technology. The preparation method is as follows: S01: The substrate is placed in a cleaning agent and ultrasonically cleaned. Liquid paraffin floats on the surface of the cleaning agent. The ultrasonic cleaning time is 3-5 minutes, and the water temperature of the cleaning agent is controlled above the melting point of the paraffin. This invention, by placing paraffin on the cleaning agent and distilled water and controlling the temperature of the cleaning agent and distilled water, keeps the paraffin in a liquid state. After cleaning, the substrate passes through the liquid paraffin, allowing the paraffin to encapsulate the substrate. The substrate is then placed in distilled water to remove residual cleaning agent, followed by another pass through the liquid paraffin, causing the paraffin to solidify on the substrate surface for transport. During transport on the assembly line, the solid paraffin protects the substrate, effectively preventing air from contacting the metal surface and preventing oxidation, thus ensuring the activity of the substrate surface.

Description

Technical Field

[0001] This invention relates to the field of brazing technology, specifically to a method for preparing an active metal brazing substrate. Background Technology

[0002] Active metal brazing is a commonly used metal joining technique that utilizes a brazing filler metal containing active metal elements to chemically react with a metal substrate, forming a strong bond. Active metal brazing substrates are materials used for electronic packaging and connections. They typically consist of a metal substrate and one or more layers of active metal to achieve reliable metal-to-metal connections, improving the performance and reliability of electronic devices.

[0003] In industrial production, the substrate surface needs to be treated before manufacturing active metal brazing substrates to ensure cleanliness and improve the strength and reliability of brazed joints. However, in industrial production, due to the assembly line production method, after the substrate is cleaned, it is transported through the assembly line. During transportation, it is easily exposed to air, and the substrate surface may react with oxygen in the air to form oxides. These oxides will affect the activity of the substrate surface, thereby affecting the subsequent plating and brazing processes. To address this, a method for preparing active metal brazing substrates has been invented. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing an active metal brazing substrate to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing an active metal brazing substrate, the preparation method of which is as follows:

[0006] S01: Place the substrate in the cleaning agent and perform ultrasonic cleaning on the substrate. Liquid paraffin floats on the surface of the cleaning agent. The ultrasonic cleaning time is 3-5 minutes. Control the water temperature of the cleaning agent to be above the melting point of the paraffin to ensure that the paraffin is in a liquid state and floats on the cleaning agent. After ultrasonic cleaning, take out the substrate and pass it through the paraffin area on the water to cover the substrate surface with paraffin. After taking out the substrate, lower the temperature of the paraffin on the substrate surface to solidify it.

[0007] S02: Place the substrate in distilled water, where liquid paraffin floats on the surface. Control the temperature of the distilled water to keep the paraffin in a liquid state. The paraffin is affected by the water temperature and falls off the substrate surface. Clean the substrate surface. After cleaning, remove the substrate and pass it through the paraffin area on the distilled water to cover the substrate surface with paraffin. After removing the substrate, lower the temperature of the paraffin on the substrate surface to solidify it.

[0008] S03: The substrate treated by S02 is placed in a connecting tube containing electrolyte. The temperature of the electrolyte is controlled so that the temperature of the electrolyte reaches the melting point of paraffin. The paraffin falls off the surface of the substrate. The substrate is then ultrasonically cleaned again. Since the density of paraffin is less than that of the electrolyte, the liquid paraffin will float on the surface of the electrolyte.

[0009] S04: Move the substrate to the other end of the connecting tube, and electroplate an active metal solder layer on the surface of the substrate in the electrolyte by electroplating. The substrate is connected to the battery cathode, while the active metal solder is connected to the battery anode.

[0010] S05: After electroplating is completed, remove the substrate, avoiding the paraffin layer on the electrolyte during removal. Clean and dry the substrate.

[0011] S06: Place the substrate from S04 into a protective gas furnace, apply pressure to the soldering surface of the substrate by mechanical pressure, so that pressure is generated between the active metal solder layer and the substrate, heat the temperature in the protective gas furnace to one-third to one-half of the melting point temperature of the active metal solder layer, and maintain it for 10-20 minutes.

[0012] S07: Remove the substrate from the protective gas furnace and use air cooling to bring the substrate to room temperature. Control the temperature drop rate of the substrate to ensure that the average temperature drop rate of the substrate surface is 4-5.5℃ / min.

[0013] The cleaning agent is composed of the following raw materials by weight: 10-12 parts sherry acid, 4-5 parts sodium hydroxide, 1-2 parts sodium carbonate, 5-6 parts acetic acid, 1-2 parts polyvinyl ether ester and 70-75 parts deionized water.

[0014] Furthermore, the protective gas furnace is filled with inert gas, and the pressure range of the mechanically applied gas is 0.5 MPa to 5 MPa.

[0015] Furthermore, in S02 to S04, a connecting pipe is used so that the liquid paraffin is at one end of the connecting pipe, and in S06, the part that comes into mechanical contact with the active metal solder layer is made of high-temperature resistant ceramic material.

[0016] Furthermore, the substrate is made of one or a mixture of copper, silver, nickel, and iron.

[0017] Furthermore, the electrolyte is one or a mixture of one or more of the electrolytes for copper plating, nickel plating, and zinc plating, and the active metal solder is made of one or more of the mixtures of copper, nickel, and zinc. The metal ions in the electrolyte and the metals in the active metal solder are the same and consistent. When a mixed electrolyte is used, the difference between the ratio of the number of metal ions in the electrolyte and the ratio of the number of metals in the active metal solder is 5%.

[0018] Furthermore, both the cleaning agent in S01 and the distilled water in S02 are deoxygenated by vacuuming.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] The method for preparing this active metal brazing substrate involves placing paraffin wax on a cleaning agent and distilled water, controlling the temperature of the cleaning agent and distilled water to keep the paraffin wax in a liquid state. After cleaning, the substrate is passed through the liquid paraffin wax, allowing the paraffin wax to encapsulate the substrate. The substrate is then placed in distilled water to remove any remaining cleaning agent, followed by another pass through the liquid paraffin wax, causing the paraffin wax to solidify on the substrate surface before transport. During the transport process on the assembly line, the solid paraffin wax protects the substrate, effectively preventing air from contacting the metal surface and preventing oxidation, thereby ensuring the activity of the substrate surface.

[0021] Meanwhile, through electroplating, when voltage is applied, the active metal ions on the cathode are reduced to metal and deposited on the substrate surface to form a uniform and dense coating. This ensures that the coating is evenly distributed on the substrate surface. Electroplating can complete the production of a large number of coatings in a short time, improving production efficiency and facilitating assembly line production. Furthermore, the uniform composite metal layer can provide a consistent welding surface, which helps to obtain higher welding quality. The adhesion between the electroplated metal layer and the substrate is usually very good, which helps to improve the strength of the weld joint, thereby ensuring the quality of subsequent brazing. Attached Figure Description

[0022] Figure 1 This is a flowchart of the present invention.

[0023] Figure 2 This is a cross-sectional view of the connecting pipe during electroplating according to the present invention.

[0024] Figure 3 This is a schematic diagram of the temperature drop curve of the substrate of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0026] like Figure 1 - Figure 3 As shown, the present invention provides a technical solution: a method for preparing an active metal brazing substrate, comprising:

[0027] Its preparation method is as follows:

[0028] S01: Place the substrate in the cleaning agent and perform ultrasonic cleaning on the substrate. Liquid paraffin floats on the surface of the cleaning agent. The ultrasonic cleaning time is 3-5 minutes. Control the water temperature of the cleaning agent to be above the melting point of the paraffin to ensure that the paraffin is in a liquid state and floats on the cleaning agent. After ultrasonic cleaning, take out the substrate and pass it through the paraffin area on the water to cover the substrate surface with paraffin. After taking out the substrate, lower the temperature of the paraffin on the substrate surface to solidify it.

[0029] S02: Place the substrate in distilled water, where liquid paraffin floats on the surface. Control the temperature of the distilled water to keep the paraffin in a liquid state. The paraffin is affected by the water temperature and falls off the substrate surface. Clean the substrate surface. After cleaning, remove the substrate and pass it through the paraffin area on the distilled water to cover the substrate surface with paraffin. After removing the substrate, lower the temperature of the paraffin on the substrate surface to solidify it.

[0030] S03: The substrate treated by S02 is placed in a connecting tube containing electrolyte. The temperature of the electrolyte is controlled so that the temperature of the electrolyte reaches the melting point of paraffin. The paraffin falls off the surface of the substrate. The substrate is then ultrasonically cleaned again. Since the density of paraffin is less than that of the electrolyte, the liquid paraffin will float on the surface of the electrolyte.

[0031] S04: Move the substrate to the other end of the connecting tube, and electroplate an active metal solder layer on the surface of the substrate in the electrolyte. The substrate is connected to the battery cathode, while the active metal solder is connected to the battery anode.

[0032] S05: After electroplating is completed, remove the substrate, avoiding the paraffin layer on the electrolyte during removal. Clean and dry the substrate.

[0033] S06: Place the substrate from S04 into a protective gas furnace, apply pressure to the soldering surface of the substrate by mechanical application, so that pressure is generated between the active metal solder layer and the substrate, heat the temperature in the protective gas furnace to one-third to one-half of the melting point temperature of the active metal solder layer, and maintain it for 10-20 minutes.

[0034] S07: Remove the substrate from the protective gas furnace and use air cooling to bring the substrate to room temperature. Control the temperature drop rate of the substrate to ensure that the average temperature drop rate of the substrate surface is 4-5.5℃ / min.

[0035] The cleaning agent is composed of the following ingredients by weight: 10-12 parts sherry acid, 4-5 parts sodium hydroxide, 1-2 parts sodium carbonate, 5-6 parts acetic acid, 1-2 parts polyvinyl ether ester and 70-75 parts deionized water.

[0036] The protective gas furnace is filled with inert gas, and the pressure range is from 0.5 MPa to 5 MPa when applied mechanically.

[0037] In S02 to S04, a connecting tube is used so that the liquid paraffin is at one end of the connecting tube. In S06, the part that comes into contact with the active metal solder layer in a mechanical manner is made of high-temperature resistant ceramic material.

[0038] The substrate is made of one or a mixture of copper, silver, nickel and iron.

[0039] The electrolyte is one or a mixture of electrolytes for copper plating, electrolytes for nickel plating, and electrolytes for zinc plating. The active metal solder is made of one or a mixture of copper, nickel, and zinc. The metal ions in the electrolyte and the metals in the active metal solder are the same and consistent. When a mixed electrolyte is used, the difference between the ratio of the number of metal ions in the electrolyte and the ratio of the number of metals in the active metal solder is 5%.

[0040] Both the cleaning agent in SO1 and the distilled water in SO2 use vacuum extraction to remove oxygen from the liquid.

[0041] The metal ions inside the electrolyte and the metals in the active metal solder are the same and consistent. When only copper plating electrolyte is used in the electrolyte, the active metal solder is composed of copper. When both copper plating electrolyte and nickel plating electrolyte are used in the electrolyte, the active metal solder is composed of copper and nickel. This ensures that the metal ions inside the electrolyte and the metals in the active metal solder are the same and consistent, and the difference between the ratio of the number of metal ions in the electrolyte and the ratio of the number of metals in the active metal solder is 5%. For example, when both copper plating electrolyte and nickel plating electrolyte are used in the electrolyte, by controlling the preparation of the electrolyte to make the ratio of copper ions to nickel ions in the mixed solution 1:2, the ratio of copper ions to nickel ions in the active metal solder is 1:1.9-2.1.

[0042] The electroplating process employs composite plating, which is a plating layer composed of two or more different materials. It can be achieved by controlling parameters such as electrolyte formulation, current density, and time during the electroplating process. Therefore, active metal solder is coated onto the substrate surface through composite plating.

[0043] Paraffin wax does not react with the substrate. Therefore, after cleaning the substrate surface, paraffin wax is wrapped around the substrate to ensure that the substrate does not come into contact with air and react, which would lead to a deterioration in the surface quality of the substrate.

[0044] The cleaning agent contains succinic acid, which increases the viscosity and wettability of the cleaning solution, improving the cleaning effect. Sodium hydroxide, a strong alkali, has excellent degreasing and cleaning capabilities, effectively removing grease and dirt from metal surfaces. Sodium carbonate softens the water. Acetic acid adjusts the pH value of the cleaning solution, improving the stability of the cleaning agent. Polyvinyl alcohol ether ester, a surfactant, reduces the surface tension of the cleaning solution, enhances the cleaning agent's penetration into metal surfaces, and improves the cleaning effect. Furthermore, the use of polyvinyl alcohol ether ester can form a molecular film on the substrate, reducing the adsorption between the substrate and paraffin wax. This results in less residual paraffin wax on the substrate during subsequent paraffin melting. The impact of polyvinyl alcohol ether ester on electroplating is also minimal. Deionized water, the main component of the cleaning agent, helps other components mix thoroughly and also dilutes the cleaning agent, preventing corrosion of the metal during the cleaning process.

[0045] In step S02, the substrate is cleaned again to reduce residual cleaning agent on the substrate and avoid the impact of subsequent cleaning agents on electroplating, such as... Figure 2 As shown, the substrate is placed in one end of the connecting tube. The electrolyte in the connecting tube melts the paraffin and immerses the substrate in the connecting tube. The substrate is then ultrasonically cleaned to further remove residual paraffin and cleaning solvent. The paraffin on the surface melts due to the temperature of the electrolyte and floats on the surface of the electrolyte. The substrate is then moved to the other end of the connecting tube, where electroplating is performed. After electroplating is completed, the substrate is removed from that end, avoiding contact between the substrate and the paraffin.

[0046] In S07, controlling the rate of temperature decrease is crucial. Air cooling allows for better control of the substrate's temperature drop rate. Ensuring an average temperature decrease rate of 4-5.5℃ / min effectively reduces lattice deformation or breakage caused by excessively rapid temperature drops. A slower cooling rate helps maintain the stability of the substrate's lattice structure, preventing lattice distortion or internal stress caused by rapid cooling. A stable lattice structure improves the substrate's quality and performance. Furthermore, the temperature decrease does not necessarily have to be absolute; a combination of cooling and heating can be used, as long as the average decrease rate remains at 4-5.5℃ / min. Figure 3As shown, a temperature drop curve for the substrate is given. Within 1 minute, it undergoes a cooling process during time period T1 and a heating process during time period T2, with T1 > T2 and a T1:T2 ratio of (1.1–1.2):1. The temperature drop during time period T1 is B, and the temperature drop during the 1-minute period is A, where A is 4–5.5℃. B > A, and the B:A ratio of (1.1–1.3):1. This setting makes the cooling and heating times nearly equal, with a slightly longer cooling time to achieve a certain degree of heat preservation, while the heating amplitude is relatively small, approximately 20% of the cooling amplitude. This provides better protection for the substrate, significantly reducing lattice deformation or cracking, and achieving better stability. Moreover, as... Figure 3 As shown, this cooling curve exhibits better smoothness, greater flexibility, and is more conducive to the protection of the substrate.

[0047] By placing paraffin wax on the cleaning agent and distilled water, and controlling the temperature of the cleaning agent and distilled water, the paraffin wax is kept in a liquid state. After cleaning, the substrate is passed through the liquid paraffin wax, allowing the paraffin wax to encapsulate the substrate. The substrate is then immersed in distilled water to remove residual cleaning agent, followed by another pass through the liquid paraffin wax, causing the paraffin wax to solidify on the substrate surface for transport. During the transport of the substrate on the assembly line, the solid paraffin wax protects the substrate, effectively preventing air from contacting the metal surface and preventing oxidation, thus ensuring the activity of the substrate surface. Through electroplating, when voltage is applied, the active metal ions on the cathode are reduced to metal and deposited on the substrate surface, forming a uniform and dense coating. This ensures that the coating is evenly distributed on the substrate surface, and electroplating can complete a large number of coatings in a short time, improving production efficiency and facilitating assembly line production. Furthermore, the uniform composite metal layer provides a consistent welding surface, contributing to higher welding quality. The adhesion between the electroplated metal layer and the substrate is typically excellent, which helps improve the strength of the weld joint, thus ensuring the quality of subsequent brazing.

[0048] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended embodiments and their equivalents.

Claims

1. A method for preparing an active metal brazing substrate, characterized in that: S01: Place the substrate in the cleaning agent and perform ultrasonic cleaning on the substrate. Liquid paraffin floats on the surface of the cleaning agent. The ultrasonic cleaning time is 3-5 minutes. Control the water temperature of the cleaning agent to be above the melting point of the paraffin to ensure that the paraffin is in a liquid state and floats on the cleaning agent. After ultrasonic cleaning, take out the substrate and pass it through the paraffin area on the water to cover the substrate surface with paraffin. After taking out the substrate, lower the temperature of the paraffin on the substrate surface to solidify it. S02: Place the substrate in distilled water, where liquid paraffin floats on the surface. Control the temperature of the distilled water to keep the paraffin in a liquid state. The paraffin is affected by the water temperature and falls off the substrate surface. Clean the substrate surface. After cleaning, remove the substrate and pass it through the paraffin area on the distilled water to cover the substrate surface with paraffin. After removing the substrate, lower the temperature of the paraffin on the substrate surface to solidify it. S03: The substrate treated by S02 is placed in a connecting tube containing electrolyte. The temperature of the electrolyte is controlled so that the temperature of the electrolyte reaches the melting point of paraffin. The paraffin falls off the surface of the substrate. The substrate is then ultrasonically cleaned again. Since the density of paraffin is less than that of the electrolyte, the liquid paraffin will float on the surface of the electrolyte. S04: Move the substrate to the other end of the connecting tube, and electroplate an active metal solder layer on the surface of the substrate in the electrolyte by electroplating. The substrate is connected to the battery cathode, while the active metal solder is connected to the battery anode. S05: After electroplating is completed, remove the substrate, avoiding the paraffin layer on the electrolyte during removal. Clean and dry the substrate. S06: Place the substrate from S04 into a protective gas furnace, apply pressure to the soldering surface of the substrate by mechanical application, so that pressure is generated between the active metal solder layer and the substrate, heat the temperature in the protective gas furnace to one-third to one-half of the melting point temperature of the active metal solder layer, and maintain it for 10-20 minutes. S07: Remove the substrate from the protective gas furnace and use air cooling to bring the substrate to room temperature. Control the temperature drop rate of the substrate to ensure that the average temperature drop rate of the substrate surface is 4-5.5℃ / min. The cleaning agent is composed of the following raw materials by weight: 10-12 parts sherry acid, 4-5 parts sodium hydroxide, 1-2 parts sodium carbonate, 5-6 parts acetic acid, 1-2 parts polyvinyl ether ester and 70-75 parts deionized water.

2. The method for preparing an active metal brazing substrate according to claim 1, characterized in that: The protective gas furnace is filled with inert gas, and the pressure range of the mechanically applied gas is 0.5 MPa to 5 MPa.

3. The method for preparing an active metal brazing substrate according to claim 1, characterized in that: The substrate is made of one or a mixture of copper, silver, nickel and iron.

4. The method for preparing an active metal brazing substrate according to claim 1, characterized in that: The electrolyte is one or a mixture of copper plating electrolyte, nickel plating electrolyte, and zinc plating electrolyte. The active metal solder is made of one or a mixture of copper, nickel, and zinc. The metal ions in the electrolyte and the metals in the active metal solder are the same and consistent. When a mixed electrolyte is used, the difference between the ratio of the number of metal ions in the electrolyte and the ratio of the number of metals in the active metal solder is 5%.

5. The method for preparing an active metal brazing substrate according to claim 1, characterized in that: Both the cleaning agent in SO1 and the distilled water in SO2 are deoxygenated by vacuuming.

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