A copper plating solution for PCB electroless copper plating and a PCB thick copper plating process

Abstract

The application relates to the technical field of PCB production, and particularly discloses a copper plating solution for PCB chemical copper plating and a PCB thick copper plating process. The copper plating solution for PCB chemical copper plating comprises 6-10 g / L of copper sulfate pentahydrate, 30-50 g / L of a complexing agent, 0.012-0.015 g / L of a stabilizer, 15-25 g / L of formaldehyde, 0.001-0.005 g / L of a surfactant and deionized water in excess; the surfactant comprises polyethylene imine and sodium dodecyl alcohol polyoxyethylene ether sulfate; and the pH value is adjusted to 11-12 by using a sodium hydroxide solution. The copper plating solution has the advantages of good stability, fast copper plating speed, uniform copper plating thickness and the like, and can effectively improve the quality and performance of a PCB.

Description

Technical Field

[0001] This invention relates to the field of PCB manufacturing technology, and in particular to a copper plating solution for PCB chemical copper plating and a thick copper deposition process for PCBs. Background Technology

[0002] PCB (Printed Circuit Board) is an indispensable component in modern electronic devices. With the continuous development of electronic devices, the requirements for the quality and performance of PCBs are becoming increasingly stringent. Among these processes, copper plating is a crucial step in PCB manufacturing, providing conductivity for subsequent electroplating processes. Therefore, the quality of the copper plating process directly impacts the quality of the fine circuitry, thus affecting the stability and reliability of the electronic devices.

[0003] Plating copper, also known as plated via (PTH), connects the conductors between layers of a double-sided or multi-layer printed circuit board. The PCB plating copper process mainly relies on chemical copper plating, which involves depositing a copper layer on the surface of an insulating substrate through a chemical reaction.

[0004] However, existing chemical copper plating technologies still have some problems. For example, due to the limitations of the uniformity of the chemical reaction, the resulting copper layer may have a certain degree of roughness and inhomogeneity at the microscale. This affects the conductivity and stability of subsequent electroplating processes on the PCB, thus impacting the overall performance of the PCB. Therefore, how to develop a novel copper plating solution for PCB chemical copper plating to improve the uniformity of the copper layer formed in the PCB copper deposition process has become an urgent problem to be solved in the current PCB manufacturing technology field. Summary of the Invention

[0005] To improve the uniformity of copper layer formation in PCB electroless copper plating processes, this application provides a copper plating solution for PCB chemical copper plating and a thick copper plating process for PCB boards. Through in-depth research, this application has discovered that the copper plating solution possesses advantages such as good stability, fast plating speed, and uniform copper plating thickness, effectively improving the quality and performance of PCB boards. Simultaneously, this process also offers advantages such as ease of operation and environmental friendliness, meeting the current development needs of the PCB board manufacturing industry. The copper plating solution for PCB chemical copper plating of this application has excellent practicality and can be widely used in the manufacturing fields of electronics, communications, and computers.

[0006] Firstly, the copper plating solution for PCB chemical copper plating provided in this application adopts the following technical solution: A copper plating solution for chemical copper plating of PCBs, wherein the mass concentration ratio of the copper plating solution for chemical copper plating of PCBs is as follows: 6-10 g / L copper sulfate pentahydrate, 30-50 g / L complexing agent, 0.012-0.015 g / L stabilizer, 15-25 g / L formaldehyde, 0.001-0.005 g / L surfactant, and the balance being deionized water; The surfactant comprises polyethyleneimine and sodium dodecyl alcohol polyoxyethylene ether sulfate; The pH value of the copper plating solution used for chemical copper plating is 11-12, which is adjusted with sodium hydroxide solution.

[0007] In the above technical solution, this application uses copper sulfate pentahydrate as the copper source to provide the copper ions required for copper plating; the complexing agent can form a stable complex with copper ions, improving the stability and plating speed of the copper plating solution; the stabilizer can maintain the stability of the copper plating solution and prevent precipitation or turbidity during the copper plating process; formaldehyde, as a reducing agent, can reduce copper ions to metallic copper, thereby achieving chemical copper plating; at the same time, this application found in its research that a surfactant composed of polyethyleneimine and sodium dodecyl alcohol polyoxyethylene ether sulfate can effectively improve the stability and plating speed of the copper plating solution and ensure the uniformity of the copper plating thickness. This is because polyethyleneimine has good complexing ability and can form a stable complex with copper ions, while sodium dodecyl alcohol polyoxyethylene ether sulfate has good dispersibility. The synergistic effect of polyethyleneimine and sodium dodecyl alcohol polyoxyethylene ether sulfate can effectively improve the copper plating uniformity of the copper plating solution and make the copper plating thickness more uniform.

[0008] Preferably, the mass ratio of polyethyleneimine to sodium dodecyl alcohol polyoxyethylene ether sulfate is 1:(5-6).

[0009] In the above technical solution, this application optimizes the mass ratio of polyethyleneimine and sodium dodecyl alcohol polyoxyethylene ether sulfate, thereby further improving the performance of the surfactant in the copper plating solution, and thus further improving the uniformity and stability of copper plating.

[0010] Preferably, the complexing agent comprises ethylenediaminetetraacetic acid and mercaptoacetic acid.

[0011] In the aforementioned technical solution, this application has discovered through research that ethylenediaminetetraacetic acid (EDTA) and mercaptoacetic acid (MGA) act as complexing agents, exhibiting excellent complexing ability and stability. These properties can effectively improve the stability and plating speed of the copper plating solution, while ensuring the uniformity of the copper plating thickness. This is because EDTA possesses multiple carboxyl and amino groups, enabling it to form multiple coordinate bonds with copper ions, resulting in stable complexes. Furthermore, the thiol groups in MGA exhibit excellent copper affinity, allowing them to form strong complexing interactions with copper ions, further enhancing the stability and plating speed of the copper plating solution.

[0012] More preferably, the mass ratio of ethylenediaminetetraacetic acid to mercaptoacetic acid is (10-15):(1-2).

[0013] In the above technical solution, this application further optimizes the mass ratio of ethylenediaminetetraacetic acid and mercaptoacetic acid, thereby further improving the performance of the complexing agent in the copper plating solution, and thus further improving the uniformity and stability of copper plating.

[0014] Preferably, the stabilizer comprises potassium ferrocyanide and polyethylene glycol, wherein the mass ratio of potassium ferrocyanide to polyethylene glycol is (1-2):10.

[0015] In the above technical solution, this application uses potassium ferrocyanide and polyethylene glycol as stabilizers, which can further improve the stability and copper plating speed of the copper plating solution. Potassium ferrocyanide can effectively prevent precipitation or turbidity during the copper plating process, while polyethylene glycol has excellent lubricity and dispersibility, ensuring the stability and uniformity of the copper plating solution. By optimizing the mass ratio of potassium ferrocyanide and polyethylene glycol, the performance of the stabilizer in the copper plating solution can be further improved, thereby further enhancing the uniformity and stability of copper plating.

[0016] Secondly, the PCB board thick copper deposition process provided in this application adopts the following technical solution: A PCB board thick copper deposition process includes the following steps: Step 1, Pre-treatment: Drill holes in the PCB board; after drilling, ensure that the holes are flat and free of burrs to provide a good substrate for the subsequent chemical copper plating process; Step 2, Pretreatment: This includes degreasing, micro-etching, pre-immersion, and activation. The degreasing process effectively removes oil stains from the PCB surface, ensuring adhesion between the copper plating layer and the substrate. The micro-etching process further cleans the PCB surface, removing oxides and impurities. The pre-immersion process fully wets the PCB surface in the copper plating solution, improving the uniformity of copper plating. The activation process forms an active layer on the PCB surface, which is beneficial for copper ion deposition. Step 3, chemical copper plating: chemical copper plating is performed using the copper plating solution for PCB chemical copper plating described in the first aspect to obtain a PCB board with thick copper plating.

[0017] Preferably, the activation in step 2 refers to immersing the PCB board in an activation solution at 40-50°C for 5-8 minutes. The mass concentration of the activation solution is as follows: 9-11 g / L sulfuric acid and 0.3-0.6 g / L palladium sulfate.

[0018] More preferably, the activation solution has the following mass concentration ratio: 10 g / L sulfuric acid and 0.5 g / L palladium sulfate.

[0019] Preferably, the copper plating parameters in step 3 are as follows: reaction time is 30-40 min, temperature is 28-32℃, and copper plating thickness is 5-7 μm. By controlling the copper plating parameters, this application can obtain a PCB board with a uniform and stable copper layer. The copper layer thickness of such a PCB board is 5-7 μm, which is more uniform and has better conductivity than the copper layer obtained by the existing copper plating process, meeting the requirements of subsequent fine circuit processing. It also enables subsequent electroplating processes to achieve thinner copper thickness and a more uniform surface copper layer.

[0020] In the above technical solution, the PCB board thick copper plating process of this application achieves thick copper plating on the PCB board through three steps: pretreatment, pre-treatment, and chemical copper plating. The pretreatment step effectively removes oil and impurities from the PCB board surface, preparing it for subsequent copper plating. The pre-treatment step further cleans the PCB board surface and improves the wettability and uniformity of the copper plating solution through degreasing, micro-etching, pre-immersion, and activation. The chemical copper plating step uses the copper plating solution for PCB chemical copper plating of this application, which can quickly and uniformly form a thick copper layer, achieving thick copper plating on the PCB board.

[0021] In summary, this application includes at least one of the following beneficial technical effects: 1. This application uses copper sulfate pentahydrate as the copper source and, in combination with additives such as complexing agents, stabilizers and reducing agents, prepares a high-efficiency and stable copper plating solution for PCB chemical copper plating. This copper plating solution has the advantages of fast copper plating speed, uniform copper plating thickness and good stability, and is suitable for large-scale industrial production.

[0022] 2. The copper plating solution of this application contains a surfactant composed of polyethyleneimine and sodium dodecyl alcohol polyoxyethylene ether sulfate. This surfactant can effectively improve the stability and copper plating speed of the copper plating solution and ensure the uniformity of the copper plating thickness, thus solving the problems of poor stability and copper plating uniformity of the copper plating solution in the prior art.

[0023] 3. The PCB board thick copper plating process of this application achieves thick copper plating on the PCB board through three steps: pretreatment, pretreatment and chemical copper plating. The process is simple to operate and easy to control, and can produce PCB boards with uniform and stable copper layers, which can meet the requirements of subsequent fine line processing and improve the conductivity and reliability of the PCB board.

[0024] 4. In the PCB board thick copper plating process of this application, by controlling the copper plating parameters, the following copper plating parameters are limited: reaction time is 30 to 40 minutes, temperature is 28 to 32°C, and a PCB board with excellent performance can be obtained. The copper plating layer of the PCB board is 5 to 7 μm thick, the copper plating layer is uniform and has good conductivity, which provides a better foundation for subsequent electroplating processes.

[0025] 5. The PCB board thick copper plating process of this application has good economic benefits. Using the copper plating solution and thick copper plating process for PCB boards described in this application can significantly improve production efficiency and reduce production costs. At the same time, because the resulting PCB board copper layer is uniform and has good conductivity, it can meet the production requirements of higher-end electronic products, thereby increasing the added value and market competitiveness of the products.

[0026] 6. The copper plating solution and thick copper deposition process for PCB chemical copper plating of this application have broad application prospects. With the continuous upgrading of electronic products, the requirements for PCBs are becoming increasingly stringent. The copper plating solution and thick copper deposition process of this application can meet the needs of large-scale, high-precision, and high-reliability PCB production, and are suitable for the production of various electronic products, possessing broad market prospects. Detailed Implementation

[0027] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0028] Example 1 A copper plating solution for PCB chemical copper plating has the following mass concentration ratio: The mixture consists of 6 g / L copper sulfate pentahydrate, 30 g / L complexing agent, 0.012 g / L stabilizer, 15 g / L formaldehyde, 0.001 g / L surfactant, and the balance being deionized water. Sodium hydroxide is added to adjust the pH to 11.

[0029] The surfactant is composed of polyethyleneimine and sodium dodecyl alcohol polyoxyethylene ether sulfate in a mass ratio of 1:5.

[0030] The complexing agent is composed of ethylenediaminetetraacetic acid and mercaptoacetic acid in a mass ratio of 10:1.

[0031] The stabilizer is composed of potassium ferrocyanide and polyethylene glycol in a mass ratio of 1:10.

[0032] The preparation method of the copper plating solution for PCB chemical copper plating is as follows: First, dissolve the complexing agent in deionized water, then add copper sulfate pentahydrate while stirring. After dissolving, add the stabilizer, formaldehyde, and surfactant. Finally, add sodium hydroxide to adjust the pH to 11.

[0033] Example 2 A copper plating solution for PCB chemical copper plating differs from Example 1 in that its mass concentration ratio is as follows: 10 g / L copper sulfate pentahydrate, 50 g / L complexing agent, 0.015 g / L stabilizer, 25 g / L formaldehyde, 0.005 g / L surfactant, with the balance being deionized water, and sodium hydroxide is added to adjust the pH value to 11.5.

[0034] The surfactant is composed of polyethyleneimine and sodium dodecyl alcohol polyoxyethylene ether sulfate in a mass ratio of 1:6.

[0035] The complexing agent is composed of ethylenediaminetetraacetic acid and mercaptoacetic acid in a mass ratio of 15:2.

[0036] The stabilizer is composed of potassium ferrocyanide and polyethylene glycol in a mass ratio of 2:10.

[0037] The preparation method of the copper plating solution for PCB chemical copper plating is as follows: First, dissolve the complexing agent in deionized water, then add copper sulfate pentahydrate while stirring. After dissolving, add the stabilizer, formaldehyde, and surfactant. Finally, add sodium hydroxide to adjust the pH to 11.5.

[0038] Example 3 A copper plating solution for PCB chemical copper plating differs from Example 1 in that the mass concentration ratio is as follows: 8 g / L copper sulfate pentahydrate, 40 g / L complexing agent, 0.014 g / L stabilizer, 20 g / L formaldehyde, 0.004 g / L surfactant, with the balance being deionized water, and sodium hydroxide is added to adjust the pH value to 11.5.

[0039] The surfactant is composed of polyethyleneimine and sodium dodecyl alcohol polyoxyethylene ether sulfate in a mass ratio of 1:5.7.

[0040] The complexing agent is composed of ethylenediaminetetraacetic acid and mercaptoacetic acid in a mass ratio of 13:1.5.

[0041] The stabilizer is composed of potassium ferrocyanide and polyethylene glycol in a mass ratio of 1.5:10.

[0042] The preparation method of the copper plating solution for PCB chemical copper plating is as follows: First, dissolve the complexing agent in deionized water, then add copper sulfate pentahydrate while stirring. After dissolving, add the stabilizer, formaldehyde, and surfactant. Finally, add sodium hydroxide to adjust the pH to 12.

[0043] Example 4 A copper plating solution for PCB chemical copper plating, which differs from Example 1 in that the complexing agent is ethylenediaminetetraacetic acid.

[0044] Example 5 A copper plating solution for PCB chemical copper plating, which differs from Example 1 in that the stabilizer is potassium ferrocyanide.

[0045] Comparative Example 1 A copper plating solution for PCB chemical copper plating, which differs from Example 1 in that the surfactant is sodium dodecyl alcohol polyoxyethylene ether sulfate.

[0046] Comparative Example 2 A copper plating solution for PCB chemical copper plating, which differs from Example 1 in that the surfactant is polyethyleneimine.

[0047] Comparative Example 3 A copper plating solution for PCB chemical copper plating, which differs from Example 1 in that it does not contain surfactants.

[0048] Application Example 1 A PCB board thick copper deposition process includes the following steps: Step 1, Pre-processing: Drilling holes in the PCB board. Step 2, Pretreatment: including degreasing, micro-etching, pre-immersion, and activation.

[0049] The degreasing parameters are as follows: 50℃, soaking for 8 minutes, and the mass concentration of the degreasing solution is as follows: 10g / L sodium hydroxide, 5g / L sodium carbonate, 2g / L ethylenediaminetetraacetic acid, and 0.5g / L quaternary ammonium cationic surfactant.

[0050] The micro-etching parameters are as follows: room temperature, immersion for 1 minute, and the mass concentration ratio of the micro-etching solution is as follows: 60 g / L sodium persulfate, 30 g / L sulfuric acid, and 10 g / L copper sulfate.

[0051] The pre-soaking parameters are: 30℃, soaking time 1 min, and the mass concentration ratio of the pre-soaking solution is as follows: 10 g / L stannous sulfate and 0.05 g / L hydrochloric acid.

[0052] The activation parameters are: 45℃, soaking time 5-8 minutes, and the mass concentration ratio of the activation solution is as follows: 10 g / L sulfuric acid and 0.5 g / L palladium sulfate.

[0053] Step 3, chemical copper plating, with the following parameters: temperature 30℃, immersion for 30 minutes, and copper plating thickness of 5-7 μm.

[0054] The copper plating solution used for PCB chemical copper plating is derived from the above embodiments.

[0055] The PCB board thick copper plating process described above results in a copper layer thickness of 5-7 μm, with uniform thickness and good conductivity, meeting the requirements for subsequent fine circuit processing. This enables subsequent electroplating processes to achieve thinner copper layers and more uniform surface copper layers.

[0056] Performance testing Test samples: copper plating solutions for PCB chemical copper plating in the above embodiments and comparative examples.

[0057] Backlight test: Thick copper was plated using the PCB board thick copper plating process of Application Example 1, and then the backlight was tested under a microscope. The backlight level was divided into 10 levels. The higher the level, the smoother the copper plating surface and the better the plating coverage. The test results are recorded in Table 1.

[0058] Copper thickness uniformity test: The PCB board of Application Example 1 was plated with thick copper using the process of immersion copper. After the copper plating was completed, the board was cut along the center line of the hole and four points were selected to measure the plating thickness, which were recorded as X1, X2, X3, X4, and X5. The variance D(X) of the five measurements was calculated. The smaller the variance, the better the copper thickness uniformity. The results are recorded in Table 1.

[0059] Table 1: Combining Examples 1-5, Comparative Examples 1-3, and Table 1, it is easy to see that the copper layer thickness of the PCB electroless copper plating solution used in Examples 1-5 is more uniform and the copper deposition rate is higher.

[0060] Based on the analysis of Example 1 and Comparative Examples 1-3, it is easy to see that Example 1 added a surfactant composed of polyethyleneimine and sodium dodecyl alcohol polyoxyethylene ether sulfate, while Comparative Example 1, Comparative Example 2, and Comparative Example 3 did not add a surfactant composed of polyethyleneimine and sodium dodecyl alcohol polyoxyethylene ether sulfate. Therefore, it is evident that only by simultaneously adding polyethyleneimine and sodium dodecyl alcohol polyoxyethylene ether sulfate to the copper plating solution for PCB chemical copper plating, allowing them to work synergistically, can the copper plating uniformity of the solution be effectively improved, resulting in a more uniform copper plating thickness.

[0061] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A copper plating solution for PCB chemical copper plating, characterized in that, The mass concentration ratio of the copper plating solution used for PCB chemical copper plating is as follows: 6~10g / L copper sulfate pentahydrate, 30~50g / L complexing agent, 0.012~0.015g / L stabilizer, 15~25g / L formaldehyde, 0.001~0.005g / L surfactant, balance deionized water; The surfactant is composed of polyethyleneimine and sodium dodecyl alcohol polyoxyethylene ether sulfate in a mass ratio of 1:(5~6); The pH value of the copper plating solution used for electroless copper plating is 11-12, which is adjusted with sodium hydroxide solution; The complexing agent comprises ethylenediaminetetraacetic acid (EDTA) and mercaptoacetic acid (MGA); the mass ratio of EDTA to MGA is (10~15):(1~2); the stabilizer comprises potassium ferrocyanide and polyethylene glycol (PEG), wherein the mass ratio of potassium ferrocyanide to PEG is (1~2):

10.

2. A PCB board thick copper deposition process, characterized in that, Includes the following steps: Step 1, Pre-processing: Drill holes in the PCB board; Step 2, Pretreatment: including degreasing, micro-etching, pre-immersion, and activation; Step 3, chemical copper plating: The copper plating solution for PCB chemical copper plating as described in claim 1 is used for chemical copper plating treatment. The copper plating parameters are as follows: reaction time is 30~40min, temperature is 28~32℃, and copper plating thickness is 5~7μm, to obtain a PCB board with thick copper plating.

3. The PCB board thick copper deposition process according to claim 2, characterized in that, The activation mentioned in step 2 refers to immersing the PCB board in an activation solution at 40~50℃ for 5~8 minutes. The mass concentration ratio of the activation solution is as follows: 9~11g / L sulfuric acid and 0.3~0.6g / L palladium sulfate.

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