A special corrosion-resistant chromium-free passivating agent for copper and copper alloys and its preparation method

Abstract

This invention belongs to the field of corrosion inhibition of metallic materials, and discloses a special corrosion-resistant chromium-free passivating agent for copper and copper alloys and its preparation method. The passivating agent comprises borax, sodium phosphate, benzotriazole, ethanol, sodium ethylenediaminetetraacetate, anhydrous sodium molybdate, a strong oxidizing agent, a silane coupling agent, and water. Through the synergistic effect of the components, the chromium-free passivating agent of this invention can form a composite passivation film on the surface of copper and its alloys, effectively preventing oxidation and discoloration of copper and its alloys without affecting their conductivity and weldability. Furthermore, the chromium-free passivating agent of this invention is low in cost, stable in performance, and convenient and quick to use.

Description

Technical Field

[0001] This invention belongs to the field of corrosion inhibitors for metallic materials, specifically relating to a corrosion-resistant, chromium-free passivating agent for copper and copper alloys and its preparation method. Background Technology

[0002] In electronic products, copper plating possesses excellent electrical and thermal conductivity, solderability, stability, and reliable adhesion to the substrate. Therefore, electroplated copper is widely used in the electronics, communications, electrical engineering, and decorative industries, particularly in the manufacturing of electronic connectors, semiconductors (LEDs), integrated circuit lead frames (IC load frames), and filters, where copper plating is often required. During the production, transportation, assembly, and use of these electronic components, contact with gases such as H₂S, SO₂, CO₂, and NO in the environment, and even exposure to ultraviolet light, can easily lead to the formation of corresponding corrosion products on the surface of the copper plating, causing discoloration and blackening. This significantly damages the original electrical properties of the copper plating. Therefore, anti-corrosion treatment of the copper plating is necessary to prevent copper and its alloys from oxidizing, discoloring, or corroding in the operating environment, thereby preventing problems such as increased contact resistance, decreased solderability, and reduced lifespan of electronic products.

[0003] Currently, chemical passivation, electrolytic passivation, and solvent-based passivating agents can all improve the corrosion and discoloration of copper plating to varying degrees. However, existing chemical and electrolytic passivation methods are prone to chromium contamination due to the use of chromates as inorganic passivating agents. While solvent-based passivating agents avoid the addition of chromium, the solvents used can pollute the air, worsen the operating environment, and most solvents are carcinogenic. Furthermore, the protective film formed on the copper plating surface by these methods is relatively thick, which can affect the conductivity of the copper plating and reduce its solderability. Therefore, it is necessary to research a corrosion-resistant, chromium-free passivating agent for copper and copper alloys to overcome the shortcomings of existing technologies. Summary of the Invention

[0004] To address the shortcomings of the existing technology, this invention provides a special corrosion-resistant chromium-free passivating agent for copper and copper alloys and its preparation method. The aim is to significantly improve the corrosion resistance of copper and copper alloys when applied to their surfaces by adjusting the formulation of the passivating agent, effectively preventing oxidation and discoloration of copper and its alloys without affecting their electrical conductivity and weldability.

[0005] To solve the technical problem, the present invention adopts the following technical solution:

[0006] This invention first provides a corrosion-resistant, chromium-free passivating agent for copper and copper alloys, comprising the following components by weight: 40-90 parts borax, 70-150 parts sodium phosphate, 40-80 parts benzotriazole, 30-90 parts ethanol, 80-150 parts sodium ethylenediaminetetraacetate, 90-170 parts anhydrous sodium molybdate, 20-70 parts strong oxidant, 20-70 parts silane coupling agent, and 500-1000 parts water.

[0007] As a further improvement to the present invention, the copper and copper alloy special corrosion-resistant chromium-free passivating agent comprises the following components by weight: 60 parts borax, 90 parts sodium phosphate, 60 parts benzotriazole, 60 parts ethanol, 80 parts sodium ethylenediaminetetraacetate, 130 parts anhydrous sodium molybdate, 40-70 parts strong oxidant, 40 parts silane coupling agent, and 700 parts water.

[0008] As a further improvement to the present invention, the copper and copper alloy special corrosion-resistant chromium-free passivating agent comprises the following components by weight: 60 parts borax, 90 parts sodium phosphate, 60 parts benzotriazole, 60 parts ethanol, 80 parts sodium ethylenediaminetetraacetate, 130 parts anhydrous sodium molybdate, 70 parts strong oxidant, 40 parts silane coupling agent, and 700 parts water.

[0009] As a further improvement to the present invention, the silane coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane or γ-aminopropyltriethoxysilane.

[0010] As a further improvement to the present invention, the strong oxidant is sodium nitrite, potassium permanganate, or hydrogen peroxide.

[0011] The present invention further provides a method for preparing the special corrosion-resistant chromium-free passivating agent for copper and copper alloys, comprising the following steps: adding 200-300 parts of water to a closed reaction vessel; mixing borax, sodium phosphate, benzotriazole, anhydrous sodium molybdate, a strong oxidant, and a silane coupling agent evenly and then adding the mixture to the reaction vessel; maintaining the temperature of the reaction vessel at 40-70°C; stirring and reacting for 0.5-1 hour; then adding ethanol and sodium ethylenediaminetetraacetate and stirring evenly; cooling; adding the remaining water and stirring evenly to obtain the special corrosion-resistant chromium-free passivating agent for copper and copper alloys.

[0012] As a further improvement to the present invention, the temperature of the reactor is maintained at 60°C.

[0013] The method of using the copper and copper alloy special corrosion-resistant chromium-free passivating agent of the present invention is as follows: immerse the copper sheet in the passivating agent for 5 to 10 minutes, and then dry it in an oven at 60 to 80°C for 0.5 to 1 hour.

[0014] The beneficial effects of this invention are reflected in:

[0015] The chromium-free passivating agent of this invention can significantly reduce the corrosive effect of external factors on copper and copper alloys. Its components include: benzotriazole, which prevents the reaction between oxygen in the air and the passivating agent; a strong oxidizing agent, which oxidizes copper into an ionic state, promoting the formation of a passivation film; and a silane coupling agent, which hydrolyzes to generate silanol and OH-. - The silane film formed further seals the pores of the passivation film, improving its density. Borax has bactericidal and bacteriostatic effects. Sodium phosphate and anhydrous sodium molybdate react with copper surface oxides to form heteropolyacid metal salts, providing inorganic passivation for copper and its alloys. Ethanol acts as a co-solvent, improving the dispersibility of the components in the passivating agent. Sodium ethylenediaminetetraacetate acts as a chelating agent, chelating with copper surface ions for further passivation. Through the synergistic effect of these components, the chromium-free passivating agent of this invention forms a composite passivation film on the surface of copper and its alloys, effectively preventing oxidation and discoloration. Furthermore, the chemical immersion method used in this invention results in a thin protective layer that does not affect the conductivity and weldability of copper and its alloys. The chromium-free passivating agent of this invention is inexpensive, stable, can be stored at room temperature, is convenient and quick to use, and essentially does not alter the metallic color. Attached Figure Description

[0016] Figure 1 This is a Tafel curve of the copper sheet treated with passivating agent-1 in Example 1 in 3.5% brine.

[0017] Figure 2 It is the copper sheet treated with passivating agent-1 in Example 1 ( Figure 2 (b) in the middle and blank copper sheet ( Figure 2 (a) is a SEM image of the area after nitric acid droplet corrosion.

[0018] Figure 3 This is a Tafel curve of the copper sheet treated with passivating agent-2 in Example 2 in 3.5% brine.

[0019] Figure 4 The copper sheet treated with passivating agent-2 in Example 2 ( Figure 4 (b) in the middle and blank copper sheet ( Figure 4 (a) is a SEM image of the area after nitric acid droplet corrosion.

[0020] Figure 5 This is a Tafel curve of the copper sheet treated with passivating agent-3 in Example 3 in 3.5% brine.

[0021] Figure 6 The copper sheet treated with passivating agent-3 in Example 3 ( Figure 6 (b) in the middle and blank copper sheet ( Figure 6 (a) is a SEM image of the area after nitric acid droplet corrosion.

[0022] Figure 7This is a Tafel curve of the copper sheet treated with passivating agent-4 in Example 4 in 3.5% brine.

[0023] Figure 8 This is a Tafel curve of the copper sheet treated with passivating agent-5 in Example 5 in 3.5% brine.

[0024] Figure 9 This is a Tafel curve of the copper sheet treated with passivating agent-6 in Example 6 in 3.5% brine. Detailed Implementation

[0025] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0026] Example 1

[0027] This embodiment provides a corrosion-resistant, chromium-free passivating agent specifically for copper and copper alloys, comprising the following components by weight: 60 parts borax, 90 parts sodium phosphate, 60 parts benzotriazole, 60 parts ethanol, 80 parts sodium ethylenediaminetetraacetate, 130 parts anhydrous sodium molybdate, 40 parts strong oxidant, 40 parts silane coupling agent, and 700 parts water. The silane coupling agent is γ-aminopropyltriethoxysilane, and the strong oxidant is sodium nitrite.

[0028] The preparation method of the above-mentioned special corrosion-resistant chromium-free passivating agent for copper and copper alloys includes the following steps: 250 parts of water are added to a closed reaction vessel, then borax, sodium phosphate, benzotriazole, anhydrous sodium molybdate, strong oxidant and silane coupling agent are mixed evenly and added to the reaction vessel. The temperature of the reaction vessel is maintained at 60°C and the reaction is stirred for 40 minutes; then ethanol and sodium ethylenediaminetetraacetate are added and stirred evenly, cooled, and the remaining water is added and stirred evenly to obtain the special corrosion-resistant chromium-free passivating agent for copper and copper alloys, which is denoted as passivating agent-1.

[0029] The method of using the special corrosion-resistant chromium-free passivating agent for copper and copper alloys obtained in this embodiment is as follows: immerse the copper sheet in the passivating agent for 10 minutes, and then dry the copper sheet in a 70°C oven for 45 minutes.

[0030] Figure 1 The table shows the Tafel corrosion potential of the copper sheet treated with passivating agent-1 in 3.5% brine in this embodiment. Details of the corresponding electrochemical parameters are shown in Table 1. The results indicate that, compared to the untreated blank copper sheet, the copper sheet treated with passivating agent-1 has a significantly higher corrosion potential. E corr With positive shift, the current density of both the cathode and anodic curves decreased significantly, indicating a reduction in corrosion current density. I corrThe corrosion rate decreased by an order of magnitude compared to the blank copper sheet, indicating a significant reduction in the electrochemical activity of the copper sheet surface. This means that the electrochemical corrosion of the copper sheet in salt water was significantly inhibited, resulting in a high corrosion inhibition efficiency. η It reached 77.4%.

[0031] A nitric acid solution was obtained by mixing nitric acid and water at a volume ratio of 3:10. The solution was then dropped onto the surface of a copper sheet treated with passivating agent-1 to conduct a nitric acid drop corrosion experiment. The drop time was 15 s, and a blank copper sheet was used as a control. Figure 2 This is a SEM image of the sample after being etched by nitric acid droplets. Figure 2 In the figure, (a) corresponds to a blank copper sheet, and (b) corresponds to a copper sheet treated with passivating agent-1. As shown in the figure, after nitric acid droplet corrosion, compared with the unpassivated copper sheet, the metal film layer on the surface of the copper sheet treated with passivating agent-1 is smoother and has not been significantly corroded by acid, while the surface of the blank copper sheet is rough, with scaly protrusions, and has been severely corroded, with the metal film layer destroyed. This demonstrates that the passivating agent in this embodiment can significantly improve the corrosion resistance of copper.

[0032] Example 2

[0033] This embodiment provides a corrosion-resistant, chromium-free passivating agent specifically for copper and copper alloys, comprising the following components by weight: 60 parts borax, 90 parts sodium phosphate, 60 parts benzotriazole, 60 parts ethanol, 80 parts sodium ethylenediaminetetraacetate, 130 parts anhydrous sodium molybdate, 40 parts strong oxidant, 40 parts silane coupling agent, and 700 parts water. The silane coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and the strong oxidant is hydrogen peroxide.

[0034] The chromium-free passivating agent in this embodiment is designated as passivating agent-2, and its preparation and usage methods are the same as in Example 1.

[0035] Figure 3 The table shows the Tafel curve of the copper sheet treated with passivating agent-2 in this embodiment in 3.5% brine. Details of the corresponding electrochemical parameters are shown in Table 1. The results indicate that, compared to the untreated blank copper sheet, the copper sheet treated with passivating agent-2 has a significantly higher corrosion current density. I corr The Tafel curve decreased by an order of magnitude, exhibiting lower current density and larger polarization resistance. R p Corrosion inhibition efficiency η The passivation rate reached 74.2%, indicating that the corrosion resistance of the copper sheet was significantly improved after passivation treatment.

[0036] Figure 4 This is a SEM image of the sample after being etched by nitric acid droplets. Figure 4In the figure, (a) corresponds to a blank copper sheet and (b) corresponds to a copper sheet treated with passivating agent-2. As shown in the figure, after nitric acid droplet corrosion, compared with the unpassivated copper sheet, the metal film layer on the surface of the copper sheet treated with passivating agent-2 is smoother and has not been significantly corroded by acid, indicating that the passivating agent in this embodiment can significantly improve the corrosion resistance of copper.

[0037] Example 3

[0038] This embodiment provides a special corrosion-resistant chromium-free passivating agent for copper and copper alloys, comprising the following components by weight: 60 parts borax, 90 parts sodium phosphate, 60 parts benzotriazole, 60 parts ethanol, 80 parts sodium ethylenediaminetetraacetate, 130 parts anhydrous sodium molybdate, 40 parts strong oxidant, 40 parts silane coupling agent, and 700 parts water.

[0039] The silane coupling agent is γ-aminopropyltriethoxysilane, and the strong oxidizing agent is potassium permanganate.

[0040] The chromium-free passivating agent in this embodiment is designated as passivating agent-3, and its preparation and usage methods are the same as in Example 1.

[0041] Figure 5 The table shows the Tafel curves of the copper sheet treated with passivating agent-3 in this embodiment in 3.5% brine. Details of the corresponding electrochemical parameters are shown in Table 1. Compared to the blank copper sheet, the copper sheet treated with passivating agent-3 shows a significant negative shift in both the cathode and anodic curves, and a higher corrosion current density. I corr Significantly reduced corrosion inhibition efficiency η The corrosion resistance of the copper sheet treated with passivating agent-3 reached 70.8%, indicating that the corrosion resistance was significantly improved.

[0042] Figure 6 This is a SEM image of the sample after being etched by nitric acid droplets. Figure 6 In the figure, (a) corresponds to a blank copper sheet and (b) corresponds to a copper sheet treated with passivating agent-3. As shown in the figure, after nitric acid droplet corrosion, compared with the unpassivated copper sheet, the metal film layer on the surface of the copper sheet treated with passivating agent-3 is smoother and has not been significantly corroded by acid, indicating that the passivating agent in this embodiment can significantly improve the corrosion resistance of copper.

[0043] Example 4

[0044] This embodiment provides a corrosion-resistant, chromium-free passivating agent specifically for copper and copper alloys, comprising the following components by weight: 60 parts borax, 90 parts sodium phosphate, 60 parts benzotriazole, 60 parts ethanol, 80 parts sodium ethylenediaminetetraacetate, 130 parts anhydrous sodium molybdate, 70 parts strong oxidizing agent, 40 parts silane coupling agent, and 700 parts water. The silane coupling agent is γ-aminopropyltriethoxysilane, and the strong oxidizing agent is sodium nitrite.

[0045] The chromium-free passivating agent in this embodiment is designated as passivating agent-4, and its preparation and usage methods are the same as in Example 1.

[0046] Figure 7 Table 1 shows a comparison of the Tafel curves of the copper sheet treated with passivating agent-4 in this embodiment and the copper sheet treated with passivating agent-1 in Example 1 in 3.5% brine. Details of the corresponding electrochemical parameters are shown in Table 1. The results indicate that, compared to the copper sheet treated with passivating agent-1, the copper sheet treated with passivating agent-4 exhibits a negative shift in both the cathode and anodic curves, and the copper sheet treated with passivating agent-4 has a lower corrosion current density. I corr and higher polarization resistance R p Corrosion inhibition efficiency η The passivation agent-4 can achieve a passivation rate of up to 90.5%, which shows that it has a greater inhibitory effect on the electrochemical corrosion of the copper sheet surface. This indicates that increasing the amount of strong oxidant sodium nitrite can improve the passivation agent's corrosion resistance to the copper sheet.

[0047] Conductivity tests were performed on a copper sheet treated with passivator-4 and a blank copper sheet of the same area (using a Reco FT-361 resistivity meter). The results showed that the conductivity of the blank copper sheet (22438.9 S / mm) was not significantly different from that of the copper sheet treated with passivator-4 (23915.8 S / mm), indicating that passivator-4 had no significant impact on the conductivity of the copper sheet.

[0048] Example 5

[0049] This embodiment provides a corrosion-resistant, chromium-free passivating agent specifically for copper and copper alloys, comprising the following components by weight: 60 parts borax, 90 parts sodium phosphate, 60 parts benzotriazole, 60 parts ethanol, 80 parts sodium ethylenediaminetetraacetate, 130 parts anhydrous sodium molybdate, 70 parts strong oxidant, 40 parts silane coupling agent, and 700 parts water. The silane coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane, and the strong oxidant is hydrogen peroxide.

[0050] The chromium-free passivating agent in this embodiment is designated as passivating agent-5, and its preparation and usage methods are the same as in Example 1.

[0051] Figure 8 Table 1 shows a comparison of the Tafel curves of the copper sheet treated with passivating agent-5 in this embodiment and the copper sheet treated with passivating agent-2 in Example 2 in 3.5% saline solution. Details of the corresponding electrochemical parameters are shown in Table 1. The results indicate that, compared to the copper sheet treated with passivating agent-2, the copper sheet treated with passivating agent-5 exhibits a negative shift in both the cathode and anodic curves, and the copper sheet treated with passivating agent-5 has a lower current density. I corr and higher polarization resistance R pCorrosion inhibition efficiency η Reaching 85.4%, it can be seen that passivator-5 has a greater inhibitory effect on the electrochemical corrosion of the copper sheet surface.

[0052] The resistivity of the copper sheet treated with passivator-5 and the blank copper sheet of the same area were tested (using a Reco FT-361 resistivity meter). The results showed that the conductivity of the blank copper sheet (22438.9 S / mm) was not much different from that of the copper sheet treated with passivator-5 (23409.7 S / mm), indicating that passivator-5 had no significant effect on the conductivity of the copper sheet.

[0053] Example 6

[0054] This embodiment provides a special corrosion-resistant chromium-free passivating agent for copper and copper alloys, comprising the following components by weight: 60 parts borax, 90 parts sodium phosphate, 60 parts benzotriazole, 60 parts ethanol, 80 parts sodium ethylenediaminetetraacetate, 130 parts anhydrous sodium molybdate, 70 parts strong oxidant, 40 parts silane coupling agent, and 700 parts water.

[0055] The silane coupling agent is γ-aminopropyltriethoxysilane, and the strong oxidant is potassium permanganate.

[0056] The chromium-free passivating agent in this embodiment is designated as passivating agent-6, and its preparation and usage methods are the same as in Example 1.

[0057] Figure 9 Table 1 shows a comparison of the Tafel curves of copper sheets treated with passivating agent-6 in this embodiment and those treated with passivating agent-3 in Example 3 in 3.5% saline solution. Details of the corresponding electrochemical parameters are shown in Table 1. The results indicate that, compared to the copper sheet treated with passivating agent-3, the cathode curve of the copper sheet treated with passivating agent-6 shows a certain negative shift, while the anodic curve shows no significant change. Increasing the amount of the strong oxidant potassium permanganate does not significantly improve the passivation ability of the passivating agent.

[0058] Table 1 Electrochemical parameters of copper sheets after passivation agent treatment in each embodiment

[0059]

[0060] The above description is merely a preferred embodiment of the present invention, and while it is quite specific and detailed, it should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various improvements and equivalent substitutions without departing from the principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A corrosion-resistant, chromium-free passivating agent specifically for copper and copper alloys, characterized in that, It includes the following components by weight: 40-90 parts borax, 70-150 parts sodium phosphate, 40-80 parts benzotriazole, 30-90 parts ethanol, 80-150 parts sodium ethylenediaminetetraacetate, 90-170 parts anhydrous sodium molybdate, 20-70 parts strong oxidant, 20-70 parts silane coupling agent, and 500-1000 parts water.

2. The copper and copper alloy corrosion-resistant chromium-free passivating agent according to claim 1, characterized in that, It includes the following components by weight: 60 parts borax, 90 parts sodium phosphate, 60 parts benzotriazole, 60 parts ethanol, 80 parts sodium ethylenediaminetetraacetate, 130 parts anhydrous sodium molybdate, 40-70 parts strong oxidant, 40 parts silane coupling agent, and 700 parts water.

3. The copper and copper alloy corrosion-resistant chromium-free passivating agent according to claim 2, characterized in that, It includes the following components by weight: 60 parts borax, 90 parts sodium phosphate, 60 parts benzotriazole, 60 parts ethanol, 80 parts sodium ethylenediaminetetraacetate, 130 parts anhydrous sodium molybdate, 70 parts strong oxidant, 40 parts silane coupling agent, and 700 parts water.

4. The copper and copper alloy corrosion-resistant chromium-free passivating agent according to claim 1, 2, or 3, characterized in that, The silane coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane or γ-aminopropyltriethoxysilane.

5. The copper and copper alloy corrosion-resistant chromium-free passivating agent according to claim 1, 2, or 3, characterized in that, The strong oxidizing agent is sodium nitrite, potassium permanganate, or hydrogen peroxide.

6. A method for preparing a special corrosion-resistant chromium-free passivating agent for copper and copper alloys as described in any one of claims 1 to 5, characterized in that, The process includes the following steps: 200-300 parts of water are added to a sealed reactor. Borax, sodium phosphate, benzotriazole, anhydrous sodium molybdate, strong oxidant, and silane coupling agent are mixed evenly and then added to the reactor. The reactor temperature is maintained at 40-70°C, and the mixture is stirred for 0.5-1 h. Ethanol and sodium ethylenediaminetetraacetate are then added and stirred evenly. The mixture is cooled, and the remaining water is added and stirred evenly to obtain a special corrosion-resistant chromium-free passivating agent for copper and copper alloys.

7. The preparation method according to claim 6, characterized in that, Maintain the reactor temperature at 60℃.

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