Copper deposition method applied to circuit board

Abstract

The invention discloses a copper deposition method applied to a circuit board, and relates to the technical field of circuit board manufacturing, and the method comprises the following steps: S1, circuit board pretreatment: carrying out deep cleaning on the circuit board, immersing the circuit board in a specially-made alkaline cleaning solution, and then carrying out micro-etching treatment; s3, a copper deposition process: carrying out copper deposition operation by adopting a chemical copper deposition solution of an innovative formula, S4, post-treatment: after the copper deposition process is completed, rapidly taking out the circuit board from the copper deposition solution, and washing and removing the residual copper deposition solution on the surface by using deionized water; according to the method, a uniform microscopic rough surface is formed through fine optimization of a pretreatment link of the circuit board, basic sites for uniform deposition of copper ions are increased, and in the copper deposition process, a dynamic circulation stirring device is adopted to ensure uniform distribution of components of a copper deposition solution, so that the thickness uniformity of a copper deposition layer is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit board manufacturing, and in particular to a copper deposition method applied to circuit boards. Background Art

[0002] With the continuous advancement of electronic technology, circuit boards are increasingly used in various electronic devices, and the requirements for their performance and quality are also constantly rising. In the entire circuit board manufacturing process, the copper plating process is an extremely critical link, which is directly related to the conductivity, reliability and subsequent processing of the circuit board. However, the current traditional copper plating method for circuit boards has a prominent problem, namely the uneven thickness of the copper plating layer. This unevenness will cause local differences in the conductivity of the circuit board, which in turn seriously affects the stability of the electronic equipment, resulting in unstable signal transmission and abnormal operation of components during operation. Therefore, the development of a new copper plating method that effectively solves the problem of uneven copper plating layer thickness is of great significance for improving the quality of circuit boards and ensuring the stable operation of electronic equipment. Summary of the Invention

[0003] In order to solve the above technical problems, a copper deposition method applied to a circuit board is provided, which solves the problems in the existing background technology.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a copper deposition method for a circuit board, comprising the following steps:

[0005] S1. PCB pretreatment: Deeply clean the PCB and immerse it in a special alkaline cleaning solution composed of 8-12g / L sodium hydroxide, 12-18g / L sodium carbonate and 3-6g / L high-efficiency surfactant. Soak it in a temperature range of 45-55℃ for 12-18 minutes to effectively remove oil, impurities and oxide layers on the surface of the PCB. After cleaning, rinse it with deionized water for 4-6 minutes to ensure that there is no cleaning solution residue on the surface of the PCB. Then, perform micro-etching treatment and place the PCB in a micro-etching solution containing sulfuric acid and sodium persulfate. The sulfuric acid concentration in the micro-etching solution is controlled at 6-10%, and the sodium persulfate concentration is 12-16g / L. Treat it at 32-38℃ for 4-6 minutes to form a fine and uniform micro-rough structure on the surface of the PCB, which provides more sites for the subsequent copper layer to adhere and enhances the bonding strength. After the micro-etching treatment is completed, rinse the PCB with deionized water again for 4-6 minutes.

[0006] S2. Activation treatment: Place the pretreated circuit board into a specially configured activation solution. The activation solution is mainly composed of a solution containing palladium ions. The palladium ion concentration is precisely controlled at 6-10 mg / L, and an appropriate amount of high-efficiency complexing agent and stabilizer are added to ensure the stability of the palladium ions in the solution. The activation treatment is carried out at a temperature of 26-32°C and lasts for 12-16 minutes. During this process, the palladium ions will be evenly adsorbed on the surface of the circuit board, forming evenly distributed catalytic active centers, laying the foundation for the uniform start of the copper plating reaction;

[0007] S3. Copper deposition process: The copper deposition process is carried out using an innovative chemical copper deposition solution. The main components of the copper deposition solution include 16-22g / L copper sulfate, 12-16mL / L formaldehyde, 16-22g / L potassium sodium tartrate, and 6-10g / L sodium hydroxide. Accelerators and inhibitors with precise control effects are added at the same time. The copper deposition process is carried out in a constant temperature water bath environment at 36-42°C. By precisely controlling the pH value of the copper deposition solution between 12.2-12.8 and utilizing the reducing properties of formaldehyde, copper ions are activated on the circuit board. The surface is uniformly reduced and deposited, and the copper deposition time is flexibly adjusted according to the required copper layer thickness, generally 22-35 minutes. More importantly, during the copper deposition process, a dynamic circulation stirring device is used to stir the copper deposition solution in all directions. The device uses specially designed pipes and nozzles to circulate the copper deposition solution at a flow rate of 3-5L / min and stir it at a speed of 120-180 rpm, ensuring that the various components in the copper deposition solution are always highly evenly distributed in the entire reaction space, greatly promoting the uniform and stable copper deposition reaction.

[0008] S4. Post-processing: After the copper plating process is completed, the circuit board is quickly removed from the copper plating solution and rinsed with deionized water for 5-8 minutes to thoroughly remove the residual copper plating solution on the surface. Then, the circuit board is placed in a passivation solution containing dilute sulfuric acid for passivation treatment. The sulfuric acid concentration in the passivation solution is 3-6%, and the passivation time is maintained at 6-10 minutes. A dense passivation film is formed on the surface of the copper plating layer, further improving the stability of the copper plating layer. Finally, the circuit board is rinsed with deionized water and placed in an oven at 65-75°C for 18-25 minutes to complete the entire copper plating process.

[0009] Compared with the prior art, the advantages of the present invention are:

[0010] Through fine optimization of the pretreatment process of the circuit board, a uniform microscopic rough surface is formed, which increases the basic sites for uniform deposition of copper ions. During the copper plating process, a dynamic circulation stirring device is used to ensure the uniform distribution of the copper plating liquid components, which greatly improves the uniformity of the copper plating layer thickness. Due to the uniform thickness of the copper plating layer, the current can pass evenly when the circuit board is powered on, greatly improving the conductive performance. DETAILED DESCRIPTION

[0011] The following description is intended to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are merely examples, and those skilled in the art may conceive of other obvious variations.

[0012] Example 1

[0013] Circuit board pretreatment:

[0014] Select a standard FR-4 circuit board and place it in an alkaline cleaning solution containing 10g / L sodium hydroxide, 15g / L sodium carbonate, and 4g / L surfactant. Soak it at 50°C for 15 minutes to thoroughly remove all contaminants from the circuit board's surface.

[0015] Rinse the circuit board with deionized water for 5 minutes to ensure that no cleaning solution residue remains.

[0016] The circuit board is placed in a micro-etching solution containing 8% sulfuric acid and 14g / L sodium persulfate. The solution is treated at 35°C for 5 minutes to form an ideal microscopic rough structure on the surface of the circuit board.

[0017] Rinse the circuit board again with deionized water for 5 minutes.

[0018] Activation treatment: Place the pretreated circuit board into the activation solution with a palladium ion concentration of 8 mg / L and activate it at a temperature of 29°C for 14 minutes.

[0019] Copper deposition process:

[0020] Copper deposition was performed using a copper deposition solution containing 20 g / L copper sulfate, 14 mL / L formaldehyde, 20 g / L potassium sodium tartrate, and 8 g / L sodium hydroxide, and appropriate amounts of accelerators and inhibitors were added.

[0021] The copper deposition solution was placed in a constant temperature water bath at 40°C, and the pH value was maintained at 12.5 through precise control. The copper deposition solution was stirred at a speed of 150 rpm using a dynamic circulation stirring device, while the flow rate of the copper deposition solution was maintained at 4 L / min, and the copper deposition time was set to 30 minutes.

[0022] Post-processing:

[0023] After copper deposition is completed, rinse the circuit board with deionized water for 6 minutes.

[0024] Place the circuit board in the passivation solution with a sulfuric acid concentration of 4% and a passivation time of 8 minutes.

[0025] After rinsing, dry the circuit board in an oven at 70°C for 20 minutes.

[0026] After testing with professional testing equipment, the thickness deviation of the copper layer of the circuit board is controlled within ±2.5μm, the conductive performance is good, and it performs stably in the simulated electronic equipment operation test, fully meeting the performance requirements of high-quality circuit boards.

[0027] Example 2

[0028] Circuit board pretreatment:

[0029] For a multi-layer circuit board, place it in an alkaline cleaning solution with a sodium hydroxide content of 9g / L, a sodium carbonate content of 16g / L, and a surfactant content of 5g / L, and soak it at a temperature of 48°C for 16 minutes.

[0030] Rinse the board with deionized water for 4 minutes.

[0031] The micro-etching solution was placed, wherein the concentration of sulfuric acid in the micro-etching solution was 7%, and the concentration of sodium persulfate was 15 g / L, and the micro-etching solution was treated at 34°C for 4.5 minutes.

[0032] Rinse the circuit board again with deionized water for 4 minutes.

[0033] Activation treatment: Place the circuit board in the activation solution with a palladium ion concentration of 7 mg / L and activate it at a temperature of 27°C for 15 minutes.

[0034] Copper deposition process:

[0035] The copper sulfate content in the copper precipitation solution is 18 g / L, the formaldehyde content is 13 mL / L, the potassium sodium tartrate content is 18 g / L, and the sodium hydroxide content is 7 g / L, and appropriate additives are added.

[0036] In a constant temperature water bath at 38°C, the pH value was controlled at 12.3, the copper precipitation solution was stirred at a speed of 140 rpm using a dynamic circulation stirring device, the flow rate of the copper precipitation solution was maintained at 3.5 L / min, and the copper precipitation time was 25 minutes.

[0037] Post-processing:

[0038] Rinse the board with deionized water for 7 minutes.

[0039] Add passivation solution, the sulfuric acid concentration in the passivation solution is 5%, and the passivation time is 7 minutes.

[0040] After rinsing, the circuit board was dried in an oven at 68°C for 22 minutes.

[0041] After testing, the thickness deviation of the copper layer of the multi-layer circuit board is within ±3μm, the copper layer is tightly bonded to each layer, and the conductive performance is stable, meeting the use requirements of complex structure circuit boards.

[0042] It can be clearly seen from the above embodiments that the copper plating method applied to circuit boards of the present invention can effectively solve the problem of uneven thickness of the copper plating layer on circuit boards of different materials and structures, significantly improve the conductive performance and stability of the circuit boards, and has extremely high practical value and promotion significance.

[0043] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions merely illustrate the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A copper deposition method for a circuit board, characterized in that: The following steps are involved: S1. PCB pretreatment: Immerse the PCB in an alkaline cleaning solution consisting of 8-12g / L sodium hydroxide, 12-18g / L sodium carbonate, and 3-6g / L high-efficiency surfactant at a temperature of 45-55°C for 12-18 minutes. Rinse with deionized water for 4-6 minutes. Next, place the PCB in a micro-etching solution containing 6-10% sulfuric acid and 12-16g / L sodium persulfate at a temperature of 32-38°C for 4-6 minutes. After micro-etching, rinse again with deionized water for 4-6 minutes. S2. Activation treatment: Place the pretreated circuit board into an activation solution with a palladium ion concentration of 6-10 mg / L and an appropriate amount of high-efficiency complexing agent and stabilizer, and perform activation treatment at a temperature of 26-32°C for 12-16 minutes; S3, copper deposition process: using a copper deposition solution containing 16-22 g / L copper sulfate, 12-16 mL / L formaldehyde, 16-22 g / L potassium sodium tartrate, 6-10 g / L sodium hydroxide and an appropriate amount of accelerator and inhibitor, in a constant temperature water bath environment of 36-42 ° C, controlling the pH value of the copper deposition solution between 12.2-12.8 for copper deposition; using a dynamic circulation stirring device during the copper deposition process, the copper deposition solution is circulated at a flow rate of 3-5 L / min and stirred at a speed of 120-180 rpm, and the copper deposition time is 22-35 minutes; S4. Post-processing: After copper deposition is completed, rinse the circuit board with deionized water for 5-8 minutes, then place the circuit board in a passivation solution with a sulfuric acid concentration of 3-6% for passivation for 6-10 minutes, and finally rinse it with deionized water and dry it in an oven at 65-75°C for 18-25 minutes.

2. A copper deposition method for a circuit board according to claim 1, characterized in that: The alkaline cleaning solution contains 10 g / L of sodium hydroxide, 15 g / L of sodium carbonate, and 4 g / L of surfactant. The soaking temperature is 50° C. and the soaking time is 15 minutes.

3. The copper deposition method for a circuit board according to claim 1, characterized in that: The concentration of sulfuric acid in the micro-etching solution is 8%, the concentration of sodium persulfate is 14 g / L, the micro-etching treatment temperature is 35° C., and the treatment time is 5 minutes.

4. The copper deposition method for a circuit board according to claim 1, characterized in that: The palladium ion concentration in the activation solution is 8 mg / L, the activation treatment temperature is 29° C., and the treatment time is 14 minutes.

5. The copper deposition method for a circuit board according to claim 1, characterized in that: The copper precipitation solution contains 20 g / L of copper sulfate, 14 mL / L of formaldehyde, 20 g / L of potassium sodium tartrate, and 8 g / L of sodium hydroxide. The copper precipitation temperature is 40° C., the pH value is 12.5, the stirring speed of the dynamic circulation stirring device is 150 rpm, the flow rate of the copper precipitation solution is 4 L / min, and the copper precipitation time is 30 minutes.

6. The copper deposition method for a circuit board according to claim 1, characterized in that: The sulfuric acid concentration in the passivation solution is 4%, the passivation time is 8 minutes, the drying temperature is 70° C., and the drying time is 20 minutes.

7. The copper deposition method for a circuit board according to claim 1, characterized in that: The circuit board is a FR-4 material circuit board or a multi-layer structure circuit board.

8. The copper deposition method for a circuit board according to claim 1, characterized in that: The dynamic circulation stirring device realizes the circulation and stirring of the copper plating solution through specially designed pipes and nozzles.