Nickel-chromium metal micro-etching solution and preparation method and surface modification application thereof

Abstract

The invention discloses a nickel-chromium metal micro-etching solution and a preparation method and surface modification application thereof, and belongs to the technical field of metal surface treatment. The nickel-chromium metal micro-etching liquid comprises ceric ammonium nitrate with the concentration of 150-350 g / L, nitric acid with the concentration of 100-250 g / L, a quaternary ammonium salt surfactant with the quaternary ammonium cation concentration of 0.0235-0.0558 mmol / L, a nitrate ion supplement with the nitrate concentration of 0.375-0.625 mol / L and the balance deionized water. The ceric ammonium nitrate is adopted as a main oxidizing agent, Ce < 4 + > ions are generated in an acid environment provided by nitric acid, the standard oxidation potential of the Ce < 4 + > ions can effectively oxidize a metal layer on the surface of the nickel-chromium alloy, the metal surface is deeply etched, and good longitudinal etching depth and dense cracking textures are formed.

Description

Technical Field

[0001] This invention belongs to the field of metal surface treatment technology, specifically relating to a micro-etching solution for roughening the surface of nickel-chromium alloys and its preparation method, as well as surface modification methods for electroless nickel plating and electroless copper plating, which are particularly suitable for surface pretreatment processes to improve the adhesion of coatings on electronic components. Background Technology

[0002] In the field of precision electronic component manufacturing, nickel-chromium metal is widely used as a substrate for various measuring instruments and meters due to its high resistivity, low temperature coefficient of resistance, large strain sensitivity coefficient, small elastic modulus, low thermal output and hysteresis, and good stability. To meet the demands of increasingly complex applications, there is a pressing need to further improve the corrosion resistance of components. However, direct chemical plating or electroplating (e.g., copper, gold, nickel) on nickel-chromium metal has resulted in insufficient adhesion. Therefore, it is usually necessary to first perform surface modification treatment on the nickel-chromium metal substrate before chemical plating or electroplating of the metal layer (e.g., copper, gold, nickel). Traditional chemical etching solutions often use strong oxidant systems (ferric chloride-hydrochloric acid mixture) or strong acid systems (e.g., hydrochloric acid-nitric acid mixture). While these can achieve surface roughening, they have the following drawbacks:

[0003] 1. The roughening morphology is uncontrollable, which easily leads to excessive corrosion or pitting, severely damaging the surface morphology;

[0004] 2. Surface residues affect the density of the coating, resulting in significant differences in appearance and affecting the adhesion of subsequent coatings;

[0005] 3. It is impossible to form regular micro- and nano-structures to enhance the subsequent mechanical interlocking effect with the coating.

[0006] However, currently only etching solutions for nickel or chromium metals are available, with no specific research and development for nickel-chromium metals. Chinese patent CN106702385B discloses a nickel etching solution using a ferric chloride system that can etch multiple metals. This formulation significantly reduces the lateral etching of nickel but performs poorly on chromium. Furthermore, in nickel-chromium alloy systems, the etching efficiency is reduced due to strong metallic bonds and the influence of chromium. Additionally, US patent US20140045352A1 uses a hydrogen peroxide-organic acid system for etching nickel, which is environmentally friendly and has a fast etching rate. However, due to the self-decomposition of hydrogen peroxide, significant differences in etching depth are unavoidable between batches, and the reagents are consumed too quickly, resulting in poor etching performance on nickel-chromium metals.

[0007] In summary, there is an urgent need to develop a special micro-etching solution for nickel-chromium alloys that can form good longitudinal etching depth, dense crack texture, and high adhesion, so as to improve the surface metal layer modification. Summary of the Invention

[0008] This invention addresses the problems of poor adhesion between the electroless or electroplated nickel-chromium metal coating and the substrate, uneven coating thickness, and complex surface modification processes in existing technologies. It provides a micro-etching solution that can form a good longitudinal etching depth and dense crack texture structure on the surface of nickel-chromium metal. Controllable coarsening is achieved through the synergistic effect of specific components, while ensuring that the micro-etching solution can be reused.

[0009] The technical solution adopted in this invention is as follows:

[0010] A nickel-chromium metal micro-etching solution comprises cerium ammonium nitrate at a concentration of 150-350 g / L, nitric acid at a concentration of 100-250 g / L, a quaternary ammonium salt surfactant with a quaternary ammonium cation concentration of 0.0235-0.0558 mmol / L, a nitrate ion supplement with a nitrate ion concentration of 0.375-0.625 mol / L, and the balance being deionized water.

[0011] Furthermore, sodium citrate at a concentration of 0.19-1.9 mmol / L can be added to the micro-etching solution as a complexing agent to improve the uniformity of micro-etching by more than 10%.

[0012] Furthermore, the surfactant is a quaternary ammonium salt, and the concentration of the quaternary ammonium cation is 0.0235-0.0558 mmol / L.

[0013] Furthermore, the surfactant is one or more of the following quaternary ammonium salts: dodecyl dimethyl benzyl ammonium chloride, dodecyl dimethyl benzyl ammonium bromide, or hexadecyl trimethyl ammonium bromide.

[0014] Furthermore, in the nitrate ion supplement, the concentration of nitrate is 0.375-0.625 mol / L.

[0015] Furthermore, the nitrate ion supplement is one or more of soluble nitrates such as sodium nitrate, potassium nitrate, and ammonium nitrate.

[0016] A method for preparing a nickel-chromium metal micro-etching solution includes the following steps:

[0017] Step 1. Dissolve the quaternary ammonium salt surfactant in deionized water to prepare solution A with a quaternary ammonium cation concentration of 0.0235-0.0558 mmol / L;

[0018] Step 2. Under stirring conditions, add cerium ammonium nitrate particles to solution A from step 1 in batches, mix thoroughly, and obtain mixture B;

[0019] Step 3. Slowly add nitric acid and ammonium nitrate dropwise to mixture B, stirring and controlling the temperature within the range of 55-65℃;

[0020] Step 4. After the addition is complete, continue stirring for 15-60 minutes until the solution color changes from light orange to dark red, thus obtaining the micro-etching solution.

[0021] A method for surface modification application of a nickel-chromium metal micro-etching solution includes:

[0022] The nickel-chromium alloy is completely immersed in a nickel-chromium metal micro-etching solution at a temperature of 40-50℃ for 3-10 minutes to form a nickel-chromium metal with dense surface crack texture.

[0023] A surface-modified metal layer is formed by depositing copper or nickel through chemical plating to fill cracks. The excellent interlocking structure between the nickel-chromium metal and the deposited metal enhances the adhesion of the surface-modified metal layer.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. The present invention provides a nickel-chromium metal micro-etching solution, in which cerium ammonium nitrate is used as the main oxidant, generating Ce in an acidic environment provided by nitric acid. 4 + ions, with a standard oxidation potential of +1.74V, can effectively oxidize the metal layer on the surface of nickel-chromium alloys and deeply etch the metal surface, forming good longitudinal etching depth and dense crack texture. The addition of nitric acid accelerates the surface roughening process while providing an acidic environment. Quaternary ammonium salt cationic surfactants such as dodecyl dimethyl benzyl ammonium chloride can form a directional adsorption layer on the metal surface, guiding the etching process preferentially along grain boundaries, thus forming good longitudinal etching and ultimately creating crack textures with a depth of 5-15 μm. Ammonium nitrate, as a nitrate ion supplement, introduces a large number of nitrate ions, inhibiting Ce in the early stages of etching. 4 Premature reduction requires replenishing the necessary nitrate ions to extend the service life of the micro-etching solution to more than 30 cycles or to be stored and used for more than 10 days.

[0026] 2. The present invention provides a nickel-chromium metal micro-etching solution using a specific concentration of quaternary ammonium salt cationic surfactant. A pre-solution (10 mg / L) of dodecyl dimethyl benzyl ammonium chloride, for example, can serve as the surfactant in the micro-etching solution, promoting the uniform distribution of active ingredients on the metal surface. Actual measurements show that the absence of surfactant significantly affects etching precision and rate, or that too low a concentration fails to reduce the surface tension of the aqueous solution and accelerate the etching process. 4 The etching effect is achieved through the contact of oxidizing agents such as ions with the metal surface. However, excessive amounts of these oxidizing agents can cause them to aggregate into micelles in the solution, which in turn affects the etching rate and contaminates the metal sample.

[0027] 3. The nickel-chromium metal micro-etching solution provided by the present invention, when treated at 40-50℃ for 3-8 minutes, can achieve a surface roughness Ra of 1.0-2.1μm, and the copper plating layer adhesion reaches 5B (ASTM D3359 standard), which is more than 30% higher than the traditional process, and the micro-etching rate deviation is less than ±5%. Attached Figure Description

[0028] Figure 1 Metallographic image of the micro-etched surface of the nickel-chromium alloy obtained in Example 1;

[0029] Figure 2 Metallographic image of the electroless copper plating section after micro-etching obtained in Example 1;

[0030] Figure 3 This is a SEM image of the micro-etching on the surface of the nickel-chromium alloy obtained in Example 1. Detailed Implementation

[0031] The present invention is further illustrated by the following examples, but the present invention is not limited thereto.

[0032] Example 1

[0033] Micro-etching solution formulation:

[0034] 320 g / L of cerium ammonium nitrate;

[0035] Nitric acid 200g / L;

[0036] Dodecyl dimethyl benzyl ammonium chloride 10 mg / L;

[0037] Ammonium nitrate 20 g / L;

[0038] The remainder is deionized water.

[0039] Preparation method:

[0040] Step 1. Dissolve dodecyl dimethyl benzyl ammonium chloride in deionized water to prepare a 10 mg / L pre-solution;

[0041] Step 2. While stirring at 500 rpm, add ammonium cerium nitrate in three portions, with a 2-minute interval between each portion;

[0042] Step 3. Heat to 60℃ and add nitric acid dropwise at a rate of 0.8% / min;

[0043] Step 4. Stir at 600 rpm for 30 minutes until the solution turns dark red;

[0044] Step 5. Add ammonium nitrate and sodium citrate, and age at 25°C in the dark for 18 hours.

[0045] Example 2

[0046] Micro-etching solution formulation:

[0047] 160 g / L of cerium ammonium nitrate;

[0048] Nitric acid 200g / L;

[0049] Dodecyl dimethyl benzyl ammonium chloride 10 mg / L;

[0050] Ammonium nitrate 20 g / L;

[0051] The remainder is deionized water.

[0052] The preparation steps are the same as in Example 1, but the aging time is extended to 12 hours.

[0053] Example 3

[0054] The concentration of dodecyl dimethyl benzyl ammonium chloride was adjusted to 0.5 g / L, and the rest was the same as in Example 1. Ra = 1.2 μm, contact angle 29°, and crack density 86 were measured, confirming that the low concentration of dodecyl dimethyl benzyl ammonium chloride still has a certain roughening effect. However, the high concentration inhibited the etching depth, resulting in a decrease in roughness without reducing the number of cracks.

[0055] Comparative Example 1

[0056] The dodecyl dimethyl benzyl ammonium chloride was omitted from the micro-etching solution formulation, and the rest was the same as in Example 1.

[0057] Comparative Example 2

[0058] The nitric acid in the micro-etching solution formulation was replaced with an equal mass of hydrochloric acid, and the rest was the same as in Example 1.

[0059] Comparative Example 3

[0060] Nitric acid and dodecyl dimethyl benzyl ammonium chloride are omitted from the micro-etching solution formulation, while the rest are the same as in Example 1.

[0061] Comparative Example 4

[0062] The cerium ammonium nitrate formula for the micro-etching solution is omitted, and the rest is the same as in Example 1.

[0063] Comparative Example 5

[0064] The entire process was carried out without heating; the components were directly mixed to obtain a light orange solution, and the rest was the same as in Example 1. The overall crack texture was found to be shallow, with only 10-20 cracks, and the surface roughness was even only Ra = 0.33 μm, indicating that heating until the color change was achieved was particularly crucial in the above steps.

[0065] Performance testing:

[0066] A 0.2mm thick Ni80Cr20 alloy sheet was micro-etched by immersion at 45℃ for 5 minutes. Surface roughness was then measured at five locations on a single sample using a 3D confocal microscope. Static contact angles were then measured at three randomly selected locations on the sample surface using a contact angle meter, and the results were observed using a fully automated metallographic microscope. Crack density was then statistically analyzed. Subsequent electroless copper plating was performed using the scratch test method, and adhesion testing was conducted according to ASTM D3359-17 standard. The test results are shown in Table 1.

[0067] Table 1 Comparison of micro-etching performance

[0068]

[0069] *Note: No crack texture was observed on the surface of Comparative Example 4.

[0070] Metallurgical microscope image of the roughened metal substrate obtained in Example 1 is shown below. Figure 1 As shown in the figure, the micro-etching solution uniformly etches the metal, forming a crack texture on the metal surface. The texture is evenly distributed and arranged in a regular pattern, providing a good roughened surface for the subsequent coating bonding.

[0071] Figure 2 The image shows a cross-sectional SEM image of Example 1. The image shows that the crack texture penetrates deep into the metal, with the deepest area reaching more than 10 μm. This indicates that the micro-etching solution formulation can selectively etch the metal surface and penetrate deep into the inner layer of the metal without damaging the visible structure of the metal, forming a crack texture and providing a surface structure that further enhances the adhesion between the surface and the coating through mechanical interlocking.

[0072] Figure 3 The image shows a metallographic microscopy section of a chemical copper plating test conducted in a subsequent test of Example 1. As can be seen from the image, chemically deposited metal (e.g., copper) can be deposited in the cracks of the crack texture, thereby forming a stronger mechanical interlocking structure to improve the adhesion of the plating layer.

[0073] The roughening treatment time was extended from 5 minutes to 15 minutes, and the temperature was increased from 45°C to 55°C, with the rest remaining the same as in Example 1. The measured Ra was 2.5 μm, and the contact angle was 10°. The excessive number of cracks made statistical analysis difficult indicates that the reaction is temperature and time-dependent. Further control of temperature and time is necessary to achieve a finer bonding effect.

[0074] Data shows that the embodiments of the present invention are significantly superior to the comparative examples in terms of surface roughening effect, contact angle test, adhesion test, and etching accuracy. Among them, cerium ammonium nitrate is the main oxidant responsible for generating the cracked structure, and the directional adsorption of dodecyl dimethyl benzyl ammonium chloride is crucial for the formation of the crack texture. Furthermore, the nitric acid system produces more uniform oxidative corrosion than hydrochloric acid; within a suitable range, an appropriate concentration formulation can achieve better and more efficient results. This invention achieves controllable surface morphology roughening through the synergistic effect of its components, which has significant application value in the field of electronic component manufacturing.

Claims

1. A nickel-chromium metal micro-etching solution, characterized in that, It includes cerium ammonium nitrate at a concentration of 150-350 g / L, nitric acid at a concentration of 100-250 g / L, quaternary ammonium salt surfactant at a quaternary ammonium cation concentration of 0.0235-0.0558 mmol / L, nitrate ion supplement at a concentration of 0.375-0.625 mol / L, and the balance is deionized water.

2. The nickel-chromium metal micro-etching solution according to claim 1, characterized in that, Sodium citrate at a concentration of 0.19-1.9 mmol / L was added to the micro-etching solution as a complexing agent.

3. The nickel-chromium metal micro-etching solution according to claim 1, characterized in that, The surfactant is one or more of dodecyl dimethyl benzyl ammonium chloride, dodecyl dimethyl benzyl ammonium bromide, and hexadecyl trimethyl ammonium bromide.

4. The nickel-chromium metal micro-etching solution according to claim 1, characterized in that, The nitrate ion supplement is one or more of sodium nitrate, potassium nitrate, and ammonium nitrate.

5. A method for preparing a nickel-chromium metal micro-etching solution, characterized in that, Includes the following steps: Step 1. Dissolve the quaternary ammonium salt surfactant in deionized water to prepare solution A with a quaternary ammonium cation concentration of 0.0235-0.0558 mmol / L; Step 2. Under stirring conditions, add cerium ammonium nitrate to solution A in step 1 in batches, mix well, and obtain mixture B; Step 3. Add nitric acid and ammonium nitrate dropwise to mixture B, stir, and control the temperature within 55-65℃; Step 4. After the addition is complete, continue stirring until the solution color changes from light orange to dark red, thus obtaining the micro-etching solution.

6. A method for surface modification application of a nickel-chromium metal micro-etching solution, characterized in that, include: Immerse the nickel-chromium alloy in a nickel-chromium metal micro-etching solution at a temperature of 40-50℃ for 3-10 minutes to form a nickel-chromium metal with a cracked texture. The process involves depositing metallic copper or nickel using chemical plating to fill in cracks and create a surface-decorated metal finish.

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