Etching solution for nickel-chromium metal layer of flexible circuit board as well as preparation method and application of etching solution

Abstract

The invention relates to an etching solution for a nickel-chromium metal layer of a flexible circuit board as well as a preparation method and application of the etching solution, and the etching solution for the nickel-chromium metal layer of the flexible circuit board comprises the following components in parts by weight: 1.5-4 parts of ammonium hydroxide; 0.5 to 5 parts of ammonium chloride; 1-10 parts of an inorganic oxidant; 1-6 parts of a polyphenol compound; and 75-90 parts of deionized water. According to the method, dynamic coupling of oxidation of the polyphenol compound and the oxidizing agent is adopted, the dissolution-passivation contradiction of traditional etching is broken through, and the nickel-chromium metal etching rate is increased.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of semiconductor manufacturing process, and particularly relates to an etching solution for a flexible circuit board nickel-chromium metal layer, a preparation method and application thereof. BACKGROUND

[0002] In the field of semiconductors and flexible electronics, nickel-chromium (NiCr) alloy is often used as a conductive layer or barrier layer of thin-film resistors and flexible circuit boards (FPC) due to its excellent resistance stability, corrosion resistance and adhesion. However, the etching process of NiCr needs to consider high precision, low damage and compatibility with flexible substrates (such as polyimide PI), and traditional etching techniques face many challenges.

[0003] For the etching of the nickel-chromium metal layer, NiCr needs to be completely removed without damaging the underlying Cu or PI substrate, the etched pattern precision line width / pitch is required to be ≤20 μm (≤10 μm for high-end FPC), and the etching solution cannot cause PI swelling or mechanical property degradation.

[0004] In recent years, acidic etching solutions such as hydrochloric acid / nitric acid mixed acid often cause Cu to be easily corroded and the sidewall roughness to be high, while alkaline etching solutions are widely concerned due to their advantages of precise control of line etching size in industry, safe working environment, no easy corrosion of equipment, no easy over-erosion and fouling of copper layer surface, etc., but have low selectivity to nickel-chromium metal. Therefore, it is necessary to develop an alkaline nickel-chromium etching solution with high selectivity to nickel-chromium metal. SUMMARY

[0005] The technical problem solved by the present application is the low selectivity of the current nickel-chromium etching solution to nickel-chromium metal.

[0006] To solve the technical problems existing in the prior art, the present application designs an etching solution for a flexible circuit board nickel-chromium metal layer, a preparation method and application thereof, which effectively etches fine lines and has high selectivity to nickel-chromium metal and low corrosion to copper.

[0007] It should be noted that in the present application, unless otherwise specified, the specific meaning of "including" involved in the composition limitation and description includes both open-ended "including", "containing" and the like and their similar meanings, and also includes closed-ended "consisting of" and the like and their similar meanings.

[0008] To solve the above-mentioned technical problems, the present application adopts the following scheme:

[0009]

First technical solution

[0010] The etching solution for a flexible circuit board nickel-chromium metal layer, characterized by comprising the following components in terms of weight parts: ammonium hydroxide 1.5-4 parts; Ammonium chloride 0.5-5 parts; Inorganic oxidizing agent 1-10 parts; Polyphenolic compound 1-6 parts; Deionized water 75-90 parts.

[0011] Further, the polyphenolic compound is one or more of procyanidins, fisetin, chlorogenic acid, gallotannin, tannin, humic acid, catechin, and tannic acid.

[0012] Further, the inorganic oxidizing agent is one or more of sodium persulfate, ammonium persulfate, potassium iodate, sodium periodate, and sodium chlorite.

[0013] Further, the mass ratio of the inorganic oxidizing agent and the polyphenolic compound is 0.5-2:1.

[0014] In the present application, in order to further optimize the performance of the etching solution, the components can be preferably selected as follows: ammonium hydroxide 2-3 parts; ammonium chloride 1-3 parts; inorganic oxidizing agent 1-5 parts; polyphenolic compound 2-5 parts; deionized water 75-85 parts.

[0015] In the present application, the inorganic oxidizing agent is preferably sodium persulfate and / or ammonium persulfate.

[0016] In the present application, the polyphenolic compound is preferably any one of chlorogenic acid, fisetin, and procyanidins.

[0017] In the present application, the mass ratio of the inorganic oxidizing agent and the polyphenolic compound is 1:1.

[0018] In the present application, the polyphenolic compound in the etching solution for the nickel-chromium metal layer of the flexible circuit board has the following unique effects:

[0019] First, it promotes the chelation and dissolution of the nickel-chromium metal. The ortho-phenolic or gallol acyl structure of the polyphenol dissociates under alkaline conditions (—OH → —O - ), and forms a water-soluble complex with Ni 2+ / Cr 3+ ;

[0020] Second, it has antioxidant and redox regulation. Some polyphenols can be oxidized to quinones, indirectly enhancing the oxidation and dissolution rate of Ni / Cr;

[0021] Third, it has surface adsorption and passivation. The polyphenol is adsorbed on the Cu surface through the phenolic hydroxyl group, forming a dense passivation layer to block the contact with the etching solution.

[0022] In the present application, the inorganic oxidizing agent in the etching solution for the nickel-chromium metal layer of the flexible circuit board has the following unique effects:

[0023] The core function of the inorganic oxidant is to regulate the dissolution behavior of Ni / Cr by selective oxidation, so that the metal forms a water-soluble complex to adjust the etching rate; and the oxidation potential of the oxidant (such as persulfate) to copper is high under alkaline conditions, and it is difficult to penetrate the passivation layer formed by copper under alkaline conditions, further protecting the copper seed layer.

[0024] In the present application, ammonium hydroxide and ammonium chloride in the etching solution for the nickel-chromium metal layer of the flexible circuit board have a unique role:

[0025] Ammonium hydroxide and ammonium chloride provide OH - ions in the nickel-chromium etching solution, stabilizing the pH of the etching solution in the alkaline range of 8.5-10, ensuring the dissociation of the phenolic hydroxyl group of the polyphenolic compound (—O - form), enhancing the chelating ability of Ni 2+ / Cr 3+ , and the alkaline conditions form a Cu(OH)2 passivation layer on the Cu surface, inhibiting Cu corrosion and protecting the underlying copper seed layer.

[0026]

Second technical solution

[0027] A preparation method of the above-mentioned etching solution for the nickel-chromium metal layer of the flexible circuit board, comprising the following steps:

[0028] Step 1: Dissolve ammonium hydroxide and ammonium chloride in deionized water, monitor with a pH meter, adjust to pH 9.5±1, then add polyphenolic compounds and inorganic oxides to obtain a mixture of components;

[0029] Step 2: Add the mixture of components obtained in step 1 to a container, stir at room temperature until all the materials are completely dissolved, and the nickel-chromium etching solution is obtained.

[0030] Further, in step 1 of the preparation method, if the pH is insufficient, add ammonium hydroxide; if the pH is too high, add NH4Cl solution.

[0031] Further, in step 2 of the preparation method, the stirring speed is 200-1500 r / min at room temperature, and the stirring time is 20-30 min.

[0032]

Third technical solution

[0033] A use method of the above-mentioned etching solution for the nickel-chromium metal layer of the flexible circuit board, comprising the following steps:

[0034] Step 1: Heat the etching solution to 20-50℃, immerse the flexible circuit board containing the nickel-chromium alloy layer in the etching solution, and immerse for 0.5-3 minutes to obtain the immersed flexible circuit board;

[0035] Step 2: Rinse the soaked flexible circuit board twice in ultrapure water, and then blow the surface water stains dry with ultrapure nitrogen gas flow to complete the surface etching treatment of the flexible circuit board.

[0036] [Fourth technical solution]

[0037] The use of the above-mentioned etchant for nickel-chromium metal layers of flexible circuit boards in metal etching. Specifically, it is used for etching nickel-chromium metal layers of flexible circuit boards.

[0038] This invention provides an etching solution for the nickel-chromium metal layer of flexible printed circuit boards, its preparation method, and its application, which have the following beneficial effects:

[0039] 1. The dynamic coupling of polyphenolic compounds and oxidant oxidation in this invention overcomes the dissolution-passivation contradiction in traditional etching. The oxidant oxidizes Ni(0) / Cr(0) to Ni 2+ / Cr 3+ Simultaneously, the phenolic hydroxyl groups (-OH) of polyphenols (such as chlorogenic acid) chelate and dissolve metal ions, forming water-soluble complexes (such as [Ni(chlorogenic acid)2)). 4- ), avoid Ni 2+ / Cr 3+ The accumulation of a passivation layer (such as Cr2O3) while the antioxidant properties of polyphenols protect the Cu surface, inhibiting the erosion of Cu by oxidants and improving the etching selectivity of nickel-chromium metals; moreover, polyphenol compounds are both oxidants and antioxidants, and under alkaline conditions, they can be activated through the phenolic hydroxyl groups (-O... - Selective chelation of Ni 2+ / Cr 3+ This forms a water-soluble complex, increasing the etching rate of nickel-chromium metal.

[0040] 2. In this invention, ammonium chloride provides NH4. + It reacts with ammonium hydroxide to form NH4 + The / NH3 buffer pair (pKa≈9.25) dynamically maintains pH stability, while at 50℃, NH4+... + Effectively suppresses NH3 volatilization and inhibits H during etching. + pH fluctuations caused by consumption.

[0041] The etching solution of this invention achieves efficient, environmentally friendly, and high-precision NiCr etching through a triple effect of polyphenol chelation, oxidant synergy, and buffer stabilization, making it particularly suitable for the green manufacturing and micro-nano fabrication needs of modern semiconductors and flexible electronic devices. Therefore, the nickel-chromium etching solution of this invention has promising application prospects in the field of semiconductor flexible circuit board etching. Attached Figure Description

[0042] Figure 1: SEM images of the copper seed layer after etching the nickel-chromium metal layer in Embodiment 1 (left) and Comparative Example 1 (right) of the present invention, magnified 20,000 times. Detailed Implementation

[0043] The present invention will be further described below with reference to specific embodiments and accompanying drawings:

[0044] In this invention, Examples 1-8 and Comparative Examples 1-5 disclose various etching solutions, the components and mass ratios of which are shown in Tables 1 and 2.

[0045] Table 1. Components and proportions of etching solutions used for nickel-chromium metal layers in Examples 1-8 of flexible circuit boards.

[0046] Table 2. Components and proportions of etching solutions for Comparative Examples 1-5

[0047] The preparation method of the etching solution for the nickel-chromium metal layer of flexible circuit boards according to the present invention is as follows:

[0048] Step 1: Dissolve ammonium hydroxide and ammonium chloride in ultrapure water, adjust the pH to 9.5±1 using a pH meter, and then add polyphenolic compounds and inorganic oxides.

[0049] Step 2: Add the mixed components to a container and stir at 200-1500 r / min at room temperature for 20-30 min until all materials are completely dissolved to obtain the nickel-chromium etching solution.

[0050] The usage method of the etching solution for the nickel-chromium metal layer of flexible circuit boards is as follows:

[0051] Step 1: Heat the etching solution to 20-50°C in a constant temperature water bath, immerse the FPC flexible circuit board containing the nickel-chromium alloy layer in the etching solution for 0.5-3 minutes, and obtain the immersed FPC flexible circuit board.

[0052] Step 2: Rinse the soaked FPC flexible circuit board twice in ultrapure water, and then blow the surface water stains dry with ultrapure nitrogen gas flow to complete the surface etching treatment of the circuit board.

[0053] Regarding performance testing and explanation:

[0054] The test method for performance 1 etching morphology is as follows:

[0055] Under a test temperature of 50℃, a flexible circuit board with a Cu seed layer, a nickel-chromium layer thickness of 500 Å, and a size of 2cm×2cm was immersed in an etching solution. After the nickel-chromium layer on the surface was completely etched, it was taken out, the residual liquid on the surface was rinsed with ultrapure water and dried with ultrapure nitrogen gas flow, and the cross-sectional morphology and the corrosion of the copper metal layer were observed using a scanning electron microscope (SEM).

[0056] The test method for performance 2 etching rate is as follows:

[0057] Under a test temperature of 50℃, flexible circuit boards with a 2cm×2cm nickel-chromium alloy layer thickness of 500 Å and a 2cm×2cm copper layer thickness of 500 Å were respectively immersed in nickel-chromium etching solution. After timing, they were removed, the surface residual liquid was rinsed with ultrapure water, and dried with ultrapure nitrogen gas. The film thickness before and after etching was measured using a four-probe resistivity meter, and the etching rate was calculated. The performance test results of the etching solutions obtained in Examples 1-8 and Comparative Examples 1-5 are shown in Table 3.

[0058] Table 3 Test Data

[0059] Analysis and explanation of the test results:

[0060] As can be seen from the test data in Table 3, the etching solution for the nickel-chromium metal layer of flexible circuit boards in this embodiment of the invention has a high NiCr etching rate and a low Cu etching rate. Specifically:

[0061] Compared to Example 1, the inorganic oxidant in Comparative Example 1 is sodium perchlorate. Due to its weaker oxidizing power, it may not be effective in oxidizing Cr, especially in alkaline environments (a higher potential is required to oxidize Cr). 3+ →Cr 6+ This leads to a significant decrease in etching rate or a deterioration in selectivity;

[0062] Comparative Example 2 uses sodium 3-mercapto-1-propanesulfonate as the chelating agent. Due to its poor stability under alkaline conditions and insufficient oxidant / complexing ability of the mercapto group, the etching efficiency is reduced and the protection of copper is decreased.

[0063] Comparative Example 3 uses phenol as the chelating agent. Since phenol contains only one phenolic hydroxyl group, it can only provide monodentate coordination. Its complexing ability is much weaker than other polyphenols, and its coordination ability is low under alkaline conditions, which leads to reduced etching efficiency and decreased protection effect on copper.

[0064] Comparative Example 4 used hydrogen peroxide as an inorganic oxidant because its standard reduction potential under alkaline conditions is much lower than that of sodium persulfate, making it difficult to effectively oxidize Cr. 3+ This leads to the formation of a passivation layer, hindering subsequent reaction processes;

[0065] Comparative Example 5 does not contain polyphenolic compounds, which leads to the formation of insoluble precipitates under alkaline conditions, resulting in loss of stability and a significant decrease in etching rate.

[0066] Further comparison can be made using the accompanying diagrams in the instruction manual:

[0067] Figure 1 These are SEM images of the copper seed layer after etching the nickel-chromium metal layer in Example 1 (left) and Comparative Example 1 (right) of the present invention, magnified 20,000 times.

[0068] from Figure 1 It can be seen that Example 1 provides better protection for the copper layer, resulting in a smoother appearance and less copper loss, while Comparative Example 1 causes more severe damage to the copper layer, resulting in an uneven appearance. Furthermore, the data shows that the average linewidth and line height of Example 1 are 4.51 micrometers and 3.06 micrometers, respectively, which are higher than the average linewidth and line height of Comparative Example 1 (3.76 micrometers and 2.93 micrometers, respectively), proving that Example 1 provides better protection for the copper layer and has higher etching selectivity.

[0069] The present invention has been described above by way of example with reference to the embodiments and accompanying drawings. Obviously, the implementation of the present invention is not limited to the above-described manner. Any improvements made by adopting the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. An etching solution for the nickel-chromium metal layer of flexible circuit boards, characterized in that, Based on parts by weight, it includes the following components: 1.5-4 parts ammonium hydroxide; Ammonium chloride 0.5-5 parts; 1-10 parts of inorganic oxidizing agent; Polyphenolic compounds 1-6 parts; 75-90 parts deionized water.

2. The etching solution for the nickel-chromium metal layer of flexible circuit boards according to claim 1, characterized in that: The polyphenolic compounds are one or more of the following: proanthocyanidins, flavonoids, chlorogenic acid, gallotannin, ellagitannins, humic acid, catechins, and tannic acid.

3. The etching solution for the nickel-chromium metal layer of flexible circuit boards according to claim 1, characterized in that: The inorganic oxidant is one or more of sodium persulfate, ammonium persulfate, potassium iodate, sodium periodate, and sodium chlorite.

4. The etching solution for the nickel-chromium metal layer of flexible circuit boards according to any one of claims 1-3, characterized in that: The mass ratio of the inorganic oxidant to the polyphenolic compound is 0.5-2:

1.

5. A method for preparing an etching solution for a nickel-chromium metal layer of a flexible circuit board according to any one of claims 1-4, characterized in that... Includes the following steps: Step 1: Dissolve ammonium hydroxide and ammonium chloride in deionized water, adjust the pH to 9.5±1 using a pH meter, then add polyphenolic compounds and inorganic oxides to obtain a mixed component; Step 2: Add the mixed components obtained in Step 1 to a container and stir at room temperature until all materials are completely dissolved to obtain the nickel-chromium etching solution.

6. A method of using the etching solution for the nickel-chromium metal layer of a flexible circuit board as described in any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Heat the etching solution to 20-50℃, immerse the flexible circuit board containing the nickel-chromium alloy layer in the etching solution for 0.5-3 minutes, and obtain the immersed flexible circuit board. Step 2: Rinse the soaked flexible circuit board twice in ultrapure water, and then blow the surface water stains dry with ultrapure nitrogen gas flow to complete the surface etching treatment of the flexible circuit board.

7. The use of the etching solution for the nickel-chromium metal layer of a flexible circuit board as described in any one of claims 1-4 in metal etching.

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