Method for reducing appearance marks on copper surface after AMB solder etching

Abstract

The invention discloses a method for reducing appearance marks on a copper surface after AMB solder etching, and the method comprises the following specific steps: S1, pressing and cutting a high-purity oxygen-free copper strip into a copper foil with the same size as supplied ceramic, and carrying out surface treatment; s2, stacking the high-purity oxygen-free copper strip and the ceramic for welding; s3, before silk-screen printing, the active metal brazing filler metal is taken out of the environment at the temperature below zero and placed at the room temperature for a period of time, and bubbles in the brazing filler metal are removed; s4, the active metal solder is combined with the high-purity oxygen-free copper strip and the ceramic substrate, and a reaction layer capable of being wetted by the liquid solder is generated; s5, performing chemical etching on the copper on the surface of the ceramic; s6, the preparation ratio of the hydrogen peroxide to the ammonia water to the EDTA-2Na is 13L: 10L: 1260g; s7, cutting the ceramic substrate; according to the method, the problem of copper surface corrosion is solved, the operation time is shortened, and the productivity is improved.

Description

Technical Field

[0001] This invention belongs to the technical field of copper-clad ceramic plates, and specifically relates to a method for reducing the appearance marks on the copper surface after AMB solder etching. Background Technology

[0002] The AMB active metal brazing copper-clad laminate is a further development of the DBC process technology. By adding a small amount of active elements that can react with ceramics to the solder, an active metal solder that can directly braze ceramics is obtained, thus achieving the brazing bonding of ceramics and copper. The entire AMB brazing process is no different from conventional brazing, including assembling the "ceramic / solder / copper" sandwich structure and high-temperature brazing. The key lies in the solder used and the process control of large-area brazing. After obtaining the AMB ceramic copper-clad laminate, a wet etching and plating process similar to that of a PCB board is used to obtain the AMB ceramic circuit board.

[0003] In the early stages of product development, in order to remove the solder bonding layer exposed between the copper layer and the ceramic layer after circuit etching, a solution prepared from hydrogen peroxide, ammonia, and EDTA-2Na was developed to react with the solder bonding layer and achieve the purpose of removing the solder bonding layer. However, this brought a new problem: during the reaction process, it would cause irregular etching on the copper surface, resulting in an uneven copper surface, which affected both functionality and aesthetics. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for reducing the appearance marks on the copper surface after AMB solder etching.

[0005] A method for reducing visible markings on copper surfaces after AMB solder etching, comprising the following steps: S1. Select high-purity oxygen-free copper strip, press and cut the high-purity oxygen-free copper strip into copper foil of the same size as the supplied ceramic, and perform surface treatment on the high-purity oxygen-free copper strip and the ceramic. S2. Stack high-purity oxygen-free copper strips and ceramics together and place them in a vacuum high-temperature furnace for welding. Active metal brazing filler metal is used during welding. The active metal brazing filler metal is a mixed paste material with adhesive properties. The mixed paste material is stored at sub-zero temperature and is thawed and mixed immediately before use. S3. Before screen printing, take the active metal solder out of the sub-zero temperature environment and leave it at room temperature for a period of time to ensure adhesion and printing performance. Before printing, centrifuge and stir the thawed active metal solder to remove air bubbles from the solder. S4. Active metal solder combines high-purity oxygen-free copper strip and ceramic substrate to form a reaction layer that can be wetted by liquid solder; S5. Chemically etch the copper on the ceramic surface to generate the designed patterns and lines; S6. A solution prepared from hydrogen peroxide, ammonia, and EDTA-2Na is used to react with the solder bonding layer to remove the solder bonding layer. The ratio of hydrogen peroxide: ammonia: EDTA-2Na is 13L:10L:1260g. S7. A single core is obtained by laser cutting of a ceramic substrate and performing a single-piece processing. S8. The surface of the ceramic substrate is coated. After the surface electroplating is completed, the substrate surface is cleaned and dried.

[0006] A further improvement of the present invention is that, in step S1, the copper content of the high-purity oxygen-free copper strip is greater than 99.99%, and the oxygen content of the high-purity oxygen-free copper strip is less than 0.0005%.

[0007] A further improvement of the present invention is that, in step S1, the ceramic contains silicon nitride formed in powder form.

[0008] A further improvement of the present invention is that, in step S2, the ceramic sheet is weighed and compared before and after printing to ensure that sufficient solder remains on the surface of the printed ceramic sheet.

[0009] A further improvement of the present invention is that, in step S5, chemical etching is formed by a lamination etching process, and the etching depth is controlled by the concentration of the acid solution and the speed of the steel strip.

[0010] A further improvement of the present invention is that, in step S7, a full visual inspection is performed on the cut ceramic substrate, and corresponding defects are identified and recorded.

[0011] A further improvement of the present invention is that, in step S7, the laser is a femtosecond laser pulse, which is used to concentrate energy in a limited area for rapid cutting.

[0012] A further improvement of the present invention is that, in step S8, the plating process includes silver plating, gold plating, and nickel plating.

[0013] Compared with existing technologies, the method for reducing visible marks on copper surfaces after AMB solder etching provided by this invention achieves at least the following beneficial effects: This invention weighs and compares ceramic sheets before and after printing to ensure sufficient solder remains on the surface of the printed ceramic sheets. After treatment with a developer, the patterned master card is immersed in an acid solution for etching. The copper parts of the master card surface not covered by photoresist are etched away, leaving the parts protected by photoresist to form the etched pattern; the solder under the copper is not etched by the acid solution, and the etching depth can be controlled by controlling the concentration of the acid solution and the immersion time of the master card. By adjusting the ratio of hydrogen peroxide:ammonia:EDTA-2Na from 8L:5L:1260g to 13L:10L:1260g, the problem of copper surface etching is solved, the appearance marks on the copper surface are reduced, and the operation time is shortened by 30%, thereby increasing production capacity. Detailed Implementation

[0014] Various exemplary embodiments of the present invention will now be described in detail. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0015] Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0016] A method for reducing visible markings on copper surfaces after AMB solder etching, comprising the following steps: S1. Select high-purity oxygen-free copper strip, press and cut the high-purity oxygen-free copper strip into copper foil of the same size as the supplied ceramic, and perform surface treatment on the high-purity oxygen-free copper strip and the ceramic. S2. Stack high-purity oxygen-free copper strips and ceramics together and place them in a vacuum high-temperature furnace for welding. Active metal brazing filler metal is used during welding. The active metal brazing filler metal is a mixed paste material with adhesive properties. The mixed paste material is stored at sub-zero temperature and is thawed and mixed immediately before use. S3. Before screen printing, take the active metal solder out of the sub-zero temperature environment and leave it at room temperature for a period of time to ensure adhesion and printing performance. Before printing, centrifuge and stir the thawed active metal solder to remove air bubbles from the solder. S4. Active metal solder combines high-purity oxygen-free copper strip and ceramic substrate to form a reaction layer that can be wetted by liquid solder; S5. Chemically etch the copper on the ceramic surface to generate the designed patterns and lines; S6. A solution prepared from hydrogen peroxide, ammonia, and EDTA-2Na is used to react with the solder bonding layer to remove the solder bonding layer. The ratio of hydrogen peroxide: ammonia: EDTA-2Na is 13L:10L:1260g. S7. A single core is obtained by laser cutting of a ceramic substrate and performing a single-piece processing. S8. The surface of the ceramic substrate is coated. After the surface electroplating is completed, the substrate surface is cleaned and dried.

[0017] A further improvement of the present invention is that, in step S1, the copper content of the high-purity oxygen-free copper strip is greater than 99.99%, and the oxygen content of the high-purity oxygen-free copper strip is less than 0.0005%.

[0018] A further improvement of the present invention is that, in step S1, the ceramic contains silicon nitride formed in powder form.

[0019] A further improvement of the present invention is that, in step S2, the ceramic sheet is weighed and compared before and after printing to ensure that sufficient solder remains on the surface of the printed ceramic sheet.

[0020] A further improvement of the present invention is that, in step S5, chemical etching is formed by a lamination etching process, and the etching depth is controlled by the concentration of the acid solution and the speed of the steel strip.

[0021] A further improvement of the present invention is that, in step S7, a full visual inspection is performed on the cut ceramic substrate, and corresponding defects are identified and recorded.

[0022] A further improvement of the present invention is that, in step S7, the laser is a femtosecond laser pulse, which is used to concentrate energy in a limited area for rapid cutting.

[0023] A further improvement of the present invention is that, in step S8, the plating process includes silver plating, gold plating, and nickel plating.

[0024] In summary, this invention provides a method for reducing surface markings on copper after AMB solder etching. The ceramic sheet is weighed and compared before and after printing to ensure sufficient solder remains on the surface after printing. After treatment with a developer, the patterned master card is immersed in an acid solution for etching. The copper portions not covered by photoresist on the master card surface are etched away, leaving the photoresist-protected portions, forming the etched pattern. The solder beneath the copper is not corroded by the acid solution. The etching depth can be controlled by adjusting the concentration of the acid solution and the immersion time of the master card. By adjusting the ratio of hydrogen peroxide:ammonia:EDTA-2Na from 8L:5L:1260g to 13L:10L:1260g, the problem of copper surface etching is solved, resulting in a smooth copper surface and reduced surface markings. This method is convenient and efficient.

[0025] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method of reducing the appearance of marks on a copper surface after AMB solder etching, characterized by, The specific steps include: S1. Select high-purity oxygen-free copper strips, press and cut the high-purity oxygen-free copper strips into copper foils with the same size as the supplied ceramic, and perform surface treatment on the high-purity oxygen-free copper strips and the ceramic; S2. Stack the high-purity oxygen-free copper strips and the ceramic in a vacuum high-temperature furnace for welding, using active metal filler metal during welding, which is a mixed paste material with adhesion, stored at zero temperature, thawed and mixed immediately before use; S3. Before screen printing, the active metal filler metal is taken out from the zero temperature environment and placed at room temperature for a period of time to ensure adhesion and printing performance. The thawed active metal filler metal is centrifugally stirred before printing to remove bubbles in the solder; S4. The active metal solder combines the high-purity oxygen-free copper strips and the ceramic substrate to form a reaction layer that can be wetted by liquid solder; S5. Chemically etch the copper on the ceramic surface to form a designed pattern and line; S6. The solution prepared from hydrogen peroxide, ammonia, and EDTA-2Na is used to react with the solder bonding layer to remove the solder bonding layer. The preparation ratio of hydrogen peroxide, ammonia, and EDTA-2Na is 13L:10L:1260g; S7. Laser cut the ceramic substrate to obtain a single core after singulation processing; S8. The surface of the ceramic substrate is plated, and after surface plating, the substrate surface is cleaned and dried.

2. A method of reducing the appearance of copper surface marks after AMB solder etching according to claim 1, wherein, In step S1, the high-purity oxygen-free copper strip contains more than 99.99% copper and less than 0.0005% oxygen.

3. A method of reducing the appearance of copper surface marks after AMB solder etching according to claim 1, wherein, In step S1, the ceramic contains silicon nitride formed in powder form.

4. A method of reducing the appearance of copper surface marks after AMB solder etching according to claim 1, wherein, In step S2, the ceramic sheet is weighed before and after printing and compared to ensure that the surface of the printed ceramic sheet has enough solder.

5. A method of reducing the appearance of copper surface marks after AMB solder etching according to claim 1, wherein, In step S5, chemical etching is formed by laminated etching process, and etching depth is controlled by acid solution concentration and steel strip speed.

6. A method of reducing the appearance of copper surface marks after AMB solder etching according to claim 1, wherein, In step S7, the appearance of the cut ceramic substrate is inspected, and corresponding defects are picked out and recorded.

7. A method of reducing the appearance of copper surface marks after AMB solder etching according to claim 1, wherein, In step S7, the laser is a femtosecond laser pulse used to concentrate energy in a limited area for rapid cutting.

8. The method of claim 1, wherein the method further comprises, In step S8, the plating treatment includes silver plating, gold plating, and nickel plating.