A copper plating composition and a process for electroless copper plating

Abstract

The application discloses a copper plating composition and a chemical copper plating process, and relates to the field of copper plating compositions, which is composed of the following components: a copper salt providing divalent copper ions; a complexing agent for complexing the divalent copper ions; a stabilizer for stabilizing the copper plating composition, which is selected from at least one of the group consisting of 2,2'-dipyridyl, potassium selenocyanate, potassium thiocyanate and 2-mercaptobenzimidazole; a reducing agent for reducing the complexed divalent copper ions to metallic copper; an alkaline adjusting agent for adjusting the pH value of the composition to an alkaline range suitable for chemical copper plating; and a solvent. The process stability and product yield are improved: through the optimized combination of the core stabilizer, the complexing agent and the reducing agent, the self-decomposition of the copper plating bath is effectively inhibited, the process stability is significantly enhanced, the incidence of key defects such as backlight defects in the metalization of the circuit board hole is greatly reduced, and the high yield of the final product is ensured.

Description

Technical Field

[0001] This invention relates to the field of copper plating compositions, specifically a copper plating composition and a chemical copper plating process. Background Technology

[0002] In the metallization process of circuit board vias, chemical copper plating is the core technology for metallizing non-metallic substrates. It deposits a uniform copper layer on the walls and surface of the vias through a chemical reduction reaction, laying the foundation for subsequent processes such as electroplating and directly affecting the conductivity, interlayer connectivity, and overall product quality of the circuit board. However, current conventional chemical copper plating compositions and supporting processes still suffer from numerous technical challenges, severely restricting production efficiency and product yield. On the one hand, conventional copper plating baths have poor stability and are prone to self-decomposition. This not only results in the ineffective loss of raw materials such as copper salts, but also produces copper powder precipitates in the bath. These impurities easily adhere to the substrate hole walls, forming defects such as pinholes and nodules, significantly increasing the incidence of backlight defects and leading to a low pass rate for metallization of circuit board holes, thus increasing production rework costs. On the other hand, the existing copper plating system has poor component compatibility. The selection and concentration control of core raw materials such as copper sources, complexing agents, and reducing agents lack scientific optimization. Some processes blindly increase the concentration of reducing agents or reduce the amount of complexing agents in pursuit of deposition efficiency, which can easily cause the copper plating reaction rate to run out of control, resulting in problems such as loose deposition layers and poor adhesion, failing to meet the production requirements of high-precision circuit boards. Summary of the Invention

[0003] The purpose of this invention is to provide a copper plating composition and a chemical copper plating process to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A copper plating composition comprising the following components: Copper salts provide divalent copper ions; Complexing agent, used to complex the divalent copper ions; A stabilizer for stabilizing the copper plating composition, wherein the stabilizer is selected from at least one of the group consisting of 2,2'-bipyridine, potassium selenocyanate, potassium thiocyanate and 2-mercaptobenzimidazole; A reducing agent used to reduce complexed divalent copper ions to metallic copper; An alkaline adjuster is used to adjust the pH of the composition to a suitable alkaline range for chemical copper plating. And solvents.

[0005] As a further aspect of the present invention: the copper salt is at least one of copper nitrate, basic copper carbonate, or copper formate.

[0006] As a further embodiment of the present invention: the complexing agent is EDTA-tetrasodium, potassium sodium tartrate, or a mixture of EDTA-tetrasodium and potassium sodium tartrate, and the concentration of the complexing agent in the copper plating composition is 35-50 g / L.

[0007] As a further aspect of the present invention, the concentration of the stabilizer in the copper plating composition is 20-120 mg / L.

[0008] As a further aspect of the present invention: the reducing agent is formaldehyde, paraformaldehyde or glyoxylic acid, and the concentration of the reducing agent in the copper plating composition is 4-8 g / L.

[0009] As a further embodiment of the present invention: the alkalinity regulator is at least one of lithium hydroxide, sodium carbonate or ammonia water.

[0010] As a further embodiment of the present invention, it also includes a wetting agent, wherein the wetting agent is a polyoxyethylene ether nonionic surfactant, and its concentration in the copper plating composition is 0.02-0.1 g / L.

[0011] A chemical copper plating process using any one of the above-mentioned copper plating compositions includes the following steps: Provide a substrate; The substrate is pretreated to make its surface catalytically active; The pretreated substrate is immersed in the copper plating composition and subjected to a chemical copper plating reaction for 10 to 15 minutes at a temperature of 45°C to 55°C and a stirring rate of 80 rpm to 320 rpm, thereby forming a metallic copper layer on the substrate surface.

[0012] As a further aspect of the present invention: the surface pretreatment step includes: The substrate is degreased. The substrate after degreasing is subjected to micro-etching treatment, wherein the micro-etching treatment uses an aqueous solution of sulfuric acid-hydrogen peroxide system or sodium persulfate-sulfuric acid system; The substrate after micro-etching is activated using a colloidal palladium solution.

[0013] As a further embodiment of the present invention: the substrate is one of FR-4 epoxy fiberglass cloth substrate, polyimide film or ceramic substrate. Compared with the prior art, the beneficial effects of the present invention are: 1. Improve process stability and product yield: Through the optimized combination of core stabilizers, complexing agents and reducing agents, this solution effectively inhibits the self-decomposition of copper plating solution, significantly enhances process stability, thereby greatly reducing the incidence of key defects such as poor backlighting in circuit board hole metallization, and ensuring a high yield of the final product.

[0014] 2. Enhanced Process Adaptability and Application Breadth: Beyond the core system, the solution offers a variety of conventional and efficient options for components such as copper sources and alkali agents, as well as pretreatment processes, and is clearly applicable to a variety of substrates. This design endows the technical solution with excellent flexibility and versatility, enabling it to adapt to different production raw material and product type requirements.

[0015] 3. Balancing performance, cost, and feasibility: While ensuring excellent copper plating layer quality and a controllable deposition process, this solution avoids the use of complex and expensive special additives, resulting in a relatively simple composition and readily available raw materials. This helps control production costs and simplify the process, making it easier to achieve large-scale, stable industrial applications on production lines. Detailed Implementation

[0016] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0017] It should be noted that, unless otherwise specified, the present invention does not specifically limit the source of the raw materials used in the following embodiments. Commercially available products or products prepared by conventional preparation methods that are well known to those skilled in the art can be used. Experimental methods that do not specify specific conditions are all conventional methods and conventional conditions well known in the art.

[0018] Preparation of plating copper composition Example 1 This embodiment provides a copper plating composition, the formulation of which is as follows: Copper nitrate: Provides a copper ion concentration of 1.5 g / L (in Cu). 2+ count); EDTA-tetrasodium: a complexing agent with a concentration of 40 g / L; 2-Mercaptobenzimidazole: a stabilizer, at a concentration of 50 mg / L; Formaldehyde aqueous solution (37%): reducing agent, with a concentration of 5 g / L based on pure formaldehyde; Lithium hydroxide: an alkaline regulator used to adjust and maintain the pH of a solution at 12.5; Polyoxyethylene (10) octylphenyl ether (wetting agent): concentration 0.05 g / L; Solvent: Deionized water, balance.

[0019] Preparation method: Under stirring, dissolve EDTA-tetrasodium, copper nitrate, 2-mercaptobenzimidazole and wetting agent in deionized water in sequence. After complete dissolution, add lithium hydroxide to adjust the pH to 12.5. Finally, add formaldehyde solution and dilute to the specified volume with deionized water. Stir well and set aside.

[0020] Example 2 This embodiment provides another copper plating composition, the formulation of which is as follows: Copper formate: provides a copper ion concentration of 2.0 g / L (in Cu). 2+ count); Sodium potassium tartrate: a complexing agent with a concentration of 45 g / L; Potassium selenocyanate: a stabilizer, with a concentration of 80 mg / L; Paraformaldehyde: a reducing agent, with a concentration of 4 g / L based on pure formaldehyde equivalent; Sodium carbonate: an alkaline regulator used to adjust and maintain the pH of a solution at 12.8; Solvent: Deionized water, balance.

[0021] Preparation method: Dissolve paraformaldehyde in a portion of deionized water under heating and stirring. After cooling, add potassium sodium tartrate, copper formate, and potassium selenocyanate in sequence. After complete dissolution, add sodium carbonate to adjust the pH to 12.8, and bring the volume to the specified level with deionized water. Stir well and set aside. No wetting agent is added in this embodiment.

[0022] Example 3 This embodiment provides another copper plating composition, the formulation of which is as follows: Basic copper carbonate: provides a copper ion concentration of 1.8 g / L (in Cu). 2+ count); Mixture of EDTA-tetrasodium and potassium sodium tartrate: complexing agent, total concentration of 35 g / L (mass ratio 1:1). 2,2'-Bipyridine: a stabilizer, at a concentration of 30 mg / L; Glyoxylic acid (50% aqueous solution): reducing agent, with a concentration of 6 g / L based on pure glyoxylic acid; Ammonia: An alkaline regulator used to adjust and maintain the pH of a solution at 12.0; Polyoxyethylene (20) dehydrated sorbitan monolaurate (wetting agent): concentration 0.02 g / L; Solvent: Deionized water, balance.

[0023] Preparation method: Slowly dissolve basic copper carbonate in dilute ammonia water, add complexing agent, stabilizer and wetting agent, stir until clear, adjust pH to 12.0 with concentrated ammonia water, add glyoxylic acid solution, dilute to volume with deionized water, stir well and set aside.

[0024] Comparative Example 1 This comparative example provides a comparative copper plating composition that differs from Example 1 in that it does not contain a stabilizer (2-mercaptobenzimidazole), while the remaining components and contents are exactly the same.

[0025] Comparative Example 2 This comparative example provides a comparative copper plating composition, which differs from Example 2 in that the concentration of the complexing agent sodium potassium tartrate is reduced to 20 g / L, while the other components and contents are exactly the same.

[0026] Comparative Example 3 This comparative example provides a comparative copper plating composition, which differs from Example 1 in that the concentration of the reducing agent formaldehyde is increased to 12 g / L, while the other components and contents are exactly the same.

[0027] Chemical copper plating process Using the copper plating compositions prepared in the above embodiments and comparative examples, chemical copper plating was performed on the substrate under the following process conditions: Substrate pretreatment: a) Degreasing treatment: Immerse a 10cm×10cm FR-4 epoxy fiberglass cloth substrate (with through holes) in a commercially available alkaline degreasing agent (at a temperature of 50°C) for 3 minutes, and then rinse with deionized water.

[0028] b) Micro-etching treatment: Immerse the degreased substrate in sulfuric acid-hydrogen peroxide micro-etching solution (H2SO4 10% v / v, H2O 2 5% v / v) at room temperature for 40 seconds, and then rinse with deionized water.

[0029] c) Activation treatment: Immerse the micro-etched substrate in colloidal palladium activation solution (Pd concentration 50mg / L, pH=1.5-2.5, temperature 40℃) for 3 minutes, and then rinse thoroughly with deionized water.

[0030] Chemical copper plating: The pretreated substrate was immersed in a copper plating composition preheated to 50°C. During the copper plating process, the mechanical stirring rate was maintained at 200 rpm. The immersion time was 12 minutes. After the copper plating was completed, the substrate was removed, rinsed with deionized water, and dried with cold air.

[0031] Performance Tests and Results The following performance tests were performed on the substrate after copper plating, and the results are recorded in Table 1.

[0032] Copper plating rate: Measured using a gravimetric method. The substrate weight was accurately weighed before copper plating (W1), and accurately weighed again after copper plating, cleaning, and drying (W2). The average copper plating rate (μm / 10min) was calculated based on the weight gain, plating time, copper density, and substrate surface area.

[0033] Backlight defect rate: Referring to the IPC-6012 standard, under the backlight inspection light box, visually inspect 10 substrates with the same treatment and count the percentage of holes with no metal deposition (light transmission) on the hole walls out of the total number of holes.

[0034] Solution stability: The freshly prepared copper plating solution was left to stand in the open at 50°C. The time from the completion of preparation to the point where the solution color darkened significantly and a small amount of reddish-brown precipitate appeared (indicating the start of self-decomposition) was recorded.

[0035] Appearance and adhesion of deposited layer: The surface morphology of the copper deposited layer was observed using scanning electron microscopy (SEM), and the adhesion was evaluated by tape peel test.

[0036] Table 1: Comparison of copper plating effects between the examples and the comparative examples Results Analysis As can be seen from the data in Table 1: The crucial role of stabilizers: Examples 1-3 all contained specific stabilizers, resulting in high-quality copper plating layers, long bath stability time, and extremely low backlight defect rates. In contrast, Comparative Example 1, which did not add stabilizers, showed significant self-decomposition of the bath within 8 hours, unstable copper plating rates, a rough and porous deposited layer, and an extremely high backlight defect rate. This demonstrates that stabilizers (such as 2-mercaptobenzimidazole, potassium selenocyanate, and 2,2'-bipyridine) are essential for stabilizing the reaction and obtaining high-quality deposited layers.

[0037] Effect of complexing agent concentration: Example 2 used a complexing agent within the specified concentration range (45 g / L), resulting in uniform deposition. In Comparative Example 2, the complexing agent concentration (20 g / L) was too low, leading to insufficient copper ion complexation, uneven copper deposition reaction, localized plating defects, decreased deposition layer quality, and increased backlight defect rate.

[0038] Optimization of reducing agent concentration: Example 1 used an optimized concentration of reducing agent (5 g / L), resulting in a dense and bright copper layer. Comparative Example 3 used an excessively high concentration of reducing agent (12 g / L). Although the copper deposition rate was fast, the reaction was too violent and difficult to control, resulting in a loose deposition layer with nodules, poor adhesion, and a high backlight failure rate. This demonstrates that the reducing agent concentration needs to be controlled within an appropriate range (e.g., 4-8 g / L).

[0039] Overall performance: The copper plating composition and process provided in Examples 1-3 of this invention exhibit excellent performance in terms of copper plating rate, uniformity / density of the deposited layer, backlight qualification rate, and bath stability. They balance deposition efficiency and deposition quality, and verify the rationality and synergistic effect of the components, concentrations, and process conditions described in the claims.

[0040] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

[0041] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A copper plating composition, characterized in that, It consists of the following components: Copper salts provide divalent copper ions; Complexing agent, used to complex the divalent copper ions; A stabilizer for stabilizing the copper plating composition, wherein the stabilizer is selected from at least one of the group consisting of 2,2'-bipyridine, potassium selenocyanate, potassium thiocyanate and 2-mercaptobenzimidazole; A reducing agent used to reduce complexed divalent copper ions to metallic copper; An alkaline adjuster is used to adjust the pH of the composition to a suitable alkaline range for chemical copper plating. And solvents.

2. The copper plating composition according to claim 1, characterized in that, The copper salt is at least one of copper nitrate, basic copper carbonate, or copper formate.

3. The copper plating composition according to claim 1, characterized in that, The complexing agent is EDTA-tetrasodium, potassium sodium tartrate, or a mixture of EDTA-tetrasodium and potassium sodium tartrate, and the concentration of the complexing agent in the copper plating composition is 35-50 g / L.

4. The copper plating composition according to claim 1, characterized in that, The concentration of the stabilizer in the copper plating composition is 20-120 mg / L.

5. The copper plating composition according to claim 1, characterized in that, The reducing agent is formaldehyde, paraformaldehyde, or glyoxylic acid, and the concentration of the reducing agent in the copper plating composition is 4-8 g / L.

6. The copper plating composition according to claim 1, characterized in that, The alkalinity regulator is at least one of lithium hydroxide, sodium carbonate, or ammonia water.

7. The copper plating composition according to any one of claims 1-6, characterized in that, It also contains a wetting agent, which is a polyoxyethylene ether nonionic surfactant, and its concentration in the copper plating composition is 0.02-0.1 g / L.

8. A chemical copper plating process using the copper plating composition as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Provide a substrate; The substrate is pretreated to make its surface catalytically active; The pretreated substrate is immersed in the copper plating composition and subjected to a chemical copper plating reaction for 10 to 15 minutes at a temperature of 45°C to 55°C and a stirring rate of 80 rpm to 320 rpm, thereby forming a metallic copper layer on the substrate surface.

9. The chemical copper plating process according to claim 8, characterized in that, The surface pretreatment step includes: The substrate is degreased. The substrate after degreasing is subjected to micro-etching treatment, wherein the micro-etching treatment uses an aqueous solution of sulfuric acid-hydrogen peroxide system or sodium persulfate-sulfuric acid system; The substrate after micro-etching is activated using a colloidal palladium solution.

10. The chemical copper plating process according to claim 8 or 9, characterized in that, The substrate is one of FR-4 epoxy fiberglass cloth substrate, polyimide film or ceramic substrate.

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