Black shadow liquid as well as preparation method and application thereof

Abstract

The invention provides a black shadow liquid as well as a preparation method and application thereof, and the preparation method of the black shadow liquid comprises the step of mixing conductive slurry, a dispersing agent, a pH regulator, a stabilizer and a polyoxyethylene ether surfactant to prepare the black shadow liquid, in the black shadow liquid, the mass ratio of the polyoxyethylene ether surfactant is 0.01%-0.2%. According to the invention, the variety and proportion of the surfactant are optimized, so that the long-term stability and dispersity of the black shadow liquid can be improved only by using a small amount of polyoxyethylene ether surfactant, and the problems of precipitation, layering and the like of the black shadow liquid are solved.

Description

Technical Field

[0001] The invention relates to the technical field of printed circuit board manufacturing, in particular to a black hole technology, and in particular to a black shadow liquid and a preparation method and application thereof. Background Art

[0002] As modern electronic devices develop towards higher integration and smaller size, the technical requirements for printed circuit boards (PCBs) are becoming increasingly stringent, especially in the manufacturing process of high-density interconnection (HDI), multi-layer PCBs and miniaturized PCBs. The quality of hole metallization technology directly affects the electrical performance, reliability and stability of the circuit board. The main function of hole metallization is to achieve electrical connection between layers of multi-layer circuit boards, and one of the core challenges of this technology is how to form a uniform, firm and highly conductive metal plating on the hole wall.

[0003] Traditional hole metallization processes mainly include chemical copper plating (ie, chemical plating) and electroplating copper. However, the chemical copper plating process has many disadvantages, including high dependence on chemicals, environmental pollution, cumbersome process, and difficulty in dealing with complex hole structures. At the same time, the waste liquid and waste gas generated during the chemical copper plating process not only increase production costs, but also cause great pollution to the environment, and are subject to increasingly stringent environmental regulations.

[0004] As an innovative hole metallization method, black hole technology (or "black shadow liquid" technology) uses a dispersion formed by conductive materials such as graphite and carbon black to form a conductive film on the hole wall of the PCB, thereby providing a good substrate for subsequent electroplating. Black hole technology does not rely on precious metal palladium, nor does it require complex chemical plating solutions, so it has significant advantages in cost, environmental protection and process simplification. However, due to the hydrophobicity and lamellar structure of graphite itself, simple physical mixing often cannot avoid the aggregation and precipitation of graphite particles, which directly affects the stability of the black shadow liquid and the black hole effect. Therefore, the biggest challenge facing the black hole process is how to achieve uniform dispersion of graphite particles in the liquid.

[0005] CN103167747A discloses a method for preparing a printed circuit board. The black hole solution disclosed in the method comprises, by weight percentage, 2%-4% carbon powder, 0.5%-1% Na 2 SiO 3 3%-4% NH 4 OH, 0.5%-2% anionic surfactant, 0.5%-1% nonionic surfactant, 0.5%-1.5% anionic nonionic composite surfactant and 88%-93% water. The disclosed black hole solution needs to add a large amount of multiple surfactants to achieve stable dispersion of carbon powder.

[0006] CN704562775A discloses a black hole liquid for printed circuit boards and a preparation method thereof. The disclosed black hole liquid includes a conductive matrix, a surfactant, a water-soluble polymer and its corresponding poor solvent, an alkaline substance and a dispersion medium. The preparation method of the black hole liquid includes adding the conductive matrix and the surfactant to the dispersion medium, grinding and then adding the water-soluble polymer, vigorously stirring and then adding the poor solvent corresponding to the water-soluble polymer, and finally adding the alkaline substance to form the black hole liquid. Although the invention enhances the dispersion stability of the black hole liquid, the preparation method is complicated.

[0007] CN108323036A discloses a black hole liquid and a black hole process, wherein the disclosed black hole liquid includes 2%-4% conductive agent, 5%-9% dispersant, 4%-7% surfactant, 1%-2% potassium carbonate, and 78%-88% deionized water. The surfactant accounts for as high as 4%-7% in the disclosed black hole liquid, which will affect the conductive properties of the conductive matrix.

[0008] The black shadow liquid disclosed in the prior art uses a large amount of surfactants or a complex preparation process to maintain the stability of the black shadow liquid. Therefore, it is of great significance to optimize the type and ratio of surfactants in the black shadow liquid, improve the dispersion effect of the conductive material, and enhance the long-term stability of the black shadow liquid. Summary of the invention

[0009] In view of the deficiencies in the prior art, the object of the present invention is to provide a black shadow liquid and a preparation method and application thereof. The present invention studies the influence of surfactants on the dispersibility of conductive materials in the black shadow liquid, optimizes the types and ratios of surfactants, and only requires a small amount of polyoxyethylene ether surfactants to improve the surface hydrophilicity of graphite, promote the uniform distribution of conductive materials in the dispersion medium, avoid the re-aggregation of conductive materials, improve the long-term stability and dispersibility of the black shadow liquid, and solve the problems of precipitation and stratification of the black shadow liquid.

[0010] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides a method for preparing a black shadow liquid, the preparation method comprising:

[0012] Mixing conductive paste, dispersant, pH adjuster, stabilizer and polyoxyethylene ether surfactant to prepare the black shadow liquid;

[0013] In the black shadow liquid, the mass proportion of the polyoxyethylene ether surfactant is 0.1‰-2‰.

[0014] Conductive materials (graphite and carbon black) are hydrophobic substances. Polyoxyethylene ether surfactants contain hydrophobic hydrocarbon chains and hydrophilic groups. The hydrophobic hydrocarbons are combined with the conductive materials through hydrophobic association, so that the hydrophilic groups are adsorbed on the surface of the conductive materials to form a dispersed suspension. Polyoxyethylene ether surfactants have a unique molecular structure, and their association with conductive materials is stronger and more solid, which significantly improves the dispersion and stability of the suspension.

[0015] In the present invention, only 0.1‰-2‰ of polyoxyethylene ether surfactant is needed to improve the hydrophilicity of the surface of the conductive material, promote the uniform distribution of the conductive material in the dispersion medium, avoid the re-aggregation of the conductive material, thereby improving the long-term stability and dispersibility of the black shadow liquid, solving the problems of precipitation and stratification of the black shadow liquid, making it have good recycling performance, reducing the need for frequent liquid replacement, and thus reducing production costs.

[0016] The polyoxyethylene ether surfactant used in the present invention has the advantages of low cost, environmental protection and easy acquisition. The preparation method of the present invention also greatly reduces the use of chemical additives, which meets the requirements of modern industry for environmental protection and sustainable development.

[0017] The present invention significantly improves the long-term stability of the black shadow liquid by optimizing the ratio of the polyoxyethylene ether surfactant, so that the black shadow liquid has good recycling performance, reduces the need for frequent liquid replacement, and thus reduces production costs. If the amount of polyoxyethylene ether surfactant added is too small, the stability of the black shadow liquid is poor, and after standing, the conductive material is stratified, which not only requires additional stirring treatment, but also significantly reduces the black hole effect. If the polyoxyethylene ether surfactant is added in excess, the black shadow liquid is prone to foaming during the application process, and the plate and the black shadow liquid are in uneven contact, resulting in a significantly poor black hole effect.

[0018] In the present invention, in the black shadow liquid, the mass proportion of the polyoxyethylene ether surfactant is 0.1‰-2‰, for example, it can be 0.1‰, 0.2‰, 0.3‰, 0.4‰, 0.5‰, 0.6‰, 0.7‰, 0.8‰, 0.85‰, 0.9‰, 1‰, 1.1‰, 1.2‰, 1.3‰, 1.4‰, 1.5‰, 1.6‰, 1.7‰, 1.8‰, 1.9‰ or 2‰, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0019] Preferably, the polyoxyethylene ether surfactant includes any one of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether or nonylphenol polyoxyethylene ether phosphate or a combination of at least two thereof. Typical but non-limiting combinations include fatty alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether phosphate and fatty alcohol polyoxyethylene ether, or alkylphenol polyoxyethylene ether and nonylphenol polyoxyethylene ether phosphate.

[0020] Preferably, in the shadow liquid, the mass proportion of the polyoxyethylene ether surfactant is 0.2‰-1.2‰, for example, it can be 0.2‰, 0.3‰, 0.4‰, 0.5‰, 0.6‰, 0.7‰, 0.8‰, 0.9‰, 1‰, 1.1‰ or 1.2‰, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] Preferably, the preparation method comprises first mixing a conductive paste, a dispersant, a pH adjuster and a stabilizer to obtain an initial black shadow liquid, and then adding a polyoxyethylene ether surfactant to prepare the black shadow liquid.

[0022] In the present invention, the conductive paste, dispersant, pH regulator and stabilizer are first mixed to prepare the initial black shadow liquid, and then the polyoxyethylene ether surfactant is added. On the basis of the initial black shadow liquid, a more targeted association can be performed on the exposed hydrophobic conductive material to ensure the effective use of the surfactant and avoid the polyoxyethylene ether surfactant from associating with other effective ingredients such as ethylene glycol and sodium carboxymethyl cellulose during direct mixing, thereby aggravating the foaming phenomenon.

[0023] Preferably, the mass ratio of the dispersant to the conductive paste is 1:(8-20), for example, it can be 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19 or 1:20, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 1:(10-15).

[0024] Preferably, the dispersant includes any one of ethylene glycol, sodium polyacrylate or polyvinyl pyrrolidone or a combination of at least two thereof. Typical but non-limiting combinations include ethylene glycol and sodium polyacrylate, polyvinyl pyrrolidone and ethylene glycol, or sodium polyacrylate and polyvinyl pyrrolidone.

[0025] Preferably, the mass ratio of the stabilizer to the conductive paste is 1:(10-30), for example, it can be 1:10, 1:12, 1:14, 1:16, 1:18, 1:20, 1:22, 1:24, 1:26, 1:28 or 1:30, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 1:(15-25).

[0026] Preferably, the stabilizer comprises any one of sodium carboxymethylcellulose, carboxymethyl cellulose or carboxyethyl cellulose or a combination of at least two thereof, and typical but non-limiting combinations include sodium carboxymethyl cellulose and carboxymethyl cellulose, carboxyethyl cellulose and sodium methyl cellulose, or carboxymethyl cellulose and carboxyethyl cellulose.

[0027] The shadow liquid provided by the present invention has an absolute value of Zeta potential that increases with the increase of pH value of the shadow liquid, and the dispersibility and stability of the shadow liquid increase, while the black hole effect decreases (i.e., the resistance value of the backlight panel increases after black hole formation). Therefore, it is very important to adjust the shadow liquid to a suitable pH.

[0028] Preferably, the pH of the shadow liquid is 8-12, for example, the pH of the shadow liquid may be 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5 or 12, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 9-11.

[0029] Preferably, the pH adjuster includes any one of potassium carbonate, potassium bicarbonate, sodium carbonate, sodium bicarbonate, sodium hydroxide or potassium hydroxide, or a combination of at least two thereof. Typical but non-limiting combinations include potassium carbonate and potassium bicarbonate, sodium carbonate and sodium bicarbonate, or sodium hydroxide and potassium hydroxide.

[0030] Preferably, the pH adjuster comprises a combination of potassium carbonate and potassium bicarbonate.

[0031] In the present invention, the amount of the pH adjuster added is not particularly limited, and the purpose is to adjust the pH to the range defined in the present invention.

[0032] Preferably, the conductive paste includes a conductive material.

[0033] The conductive paste used in the black shadow liquid provided by the present invention only includes conductive material and water.

[0034] Preferably, the mass percentage of the conductive material in the conductive paste is 7%-9%, for example, 7%, 7.5%, 8%, 8.5% or 9%, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] Preferably, the conductive material comprises any one of graphite, carbon black, carbon nanotubes or graphene, or a combination of at least two thereof. Typical but non-limiting combinations include graphite and carbon black, carbon nanotubes and graphene, graphite and carbon nanotubes, or graphite and graphene.

[0036] Preferably, the conductive material comprises a combination of graphite and carbon black.

[0037] Preferably, the mass ratio of graphite to carbon black is (5-9):1, for example, 5:1, 6:1, 7:1, 8:1 or 9:1, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] In a second aspect, the present invention provides a black shadow liquid, which is prepared by the preparation method described in the first aspect.

[0039] The black shadow liquid prepared by the present invention has excellent dispersibility and stability, the conductive material is evenly distributed in the black shadow liquid, and has good stability, thus overcoming the problem of decreased performance due to precipitation or stratification.

[0040] In a third aspect, the present invention provides an application of the black shadow liquid as described in the second aspect, wherein the black shadow liquid is applied to black hole formation of a printed circuit board.

[0041] The black shadow liquid provided by the present invention can obtain a more uniform and stable conductive film during the electroplating process, ensuring the quality and consistency of the coating. This feature is crucial for the manufacture of high-density, high-performance printed circuit boards.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] (1) The present invention optimizes the type and ratio of surfactants and uses only a very small amount of polyoxyethylene ether surfactants, thereby improving the hydrophilicity of the surface of the conductive material, promoting the uniform distribution of the conductive material in the dispersion medium, avoiding the re-aggregation of the conductive material, and improving the long-term stability and dispersibility of the black shadow liquid. The problems of precipitation and stratification of the black shadow liquid are solved, so that the black shadow liquid has good recycling performance, reduces the need for frequent replacement of the liquid, and thus reduces the production cost.

[0044] (2) The polyoxyethylene ether surfactant used in the present invention is low-cost, environmentally friendly and easy to obtain, and greatly reduces the use of chemical additives, which meets the needs of modern industry for environmental protection and sustainable development.

[0045] (3) The black shadow liquid provided by the present invention can provide a more uniform and stable conductive film during the electroplating process, ensuring the quality and consistency of the coating. This feature is crucial for the manufacture of high-density, high-performance printed circuit boards. DETAILED DESCRIPTION

[0046] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0047] Example 1

[0048] This embodiment provides a method for preparing a black shadow liquid, comprising:

[0049] (1) 24 g of conductive paste, 2 g of ethylene glycol and 1 g of sodium carboxymethyl cellulose were mixed, and the pH was adjusted to 10 using potassium carbonate and potassium bicarbonate to obtain an initial black shadow liquid, wherein the mass percentage of the conductive material in the conductive paste was 7.8%, and the conductive material was graphite and carbon black in a mass ratio of 8:1.

[0050] (2) Mix the initial black shadow liquid obtained in step (1) and 0.01 g of alkylphenol polyoxyethylene ether (brand: TX-10), and add deionized water to a total weight of 45 g to obtain a black shadow liquid.

[0051] The mass proportion of alkylphenol polyoxyethylene ether in the black shadow liquid prepared in this embodiment is 0.22‰.

[0052] Example 2

[0053] This embodiment provides a method for preparing a black shadow liquid, comprising:

[0054] (1) 24 g of conductive paste, 2.4 g of ethylene glycol and 1.6 g of sodium carboxymethyl cellulose were mixed, and the pH was adjusted to 9 using potassium carbonate and potassium bicarbonate to obtain an initial black shadow liquid, wherein the mass percentage of the conductive material in the conductive paste was 7%, and the conductive material was graphite and carbon black in a mass ratio of 7:1.

[0055] (2) Mix the initial black shadow liquid obtained in step (1) and 0.05 g of fatty alcohol polyoxyethylene ether (brand: AEO-9), add deionized water to a total weight of 45 g, and obtain a black shadow liquid.

[0056] The mass proportion of fatty alcohol polyoxyethylene ether in the black shadow liquid prepared in this embodiment is 1.11‰.

[0057] Example 3

[0058] This embodiment provides a method for preparing a black shadow liquid, comprising:

[0059] (1) 24 g of conductive paste, 1.6 g of ethylene glycol and 0.96 g of sodium carboxymethyl cellulose were mixed, and the pH was adjusted to 11 using potassium carbonate and potassium bicarbonate to obtain an initial black shadow liquid, wherein the mass percentage of the conductive material in the conductive paste was 8%, and the conductive material was graphite and carbon black in a mass ratio of 9:1.

[0060] (2) Mix the initial black shadow liquid obtained in step (1) and 0.036 g of alkylphenol polyoxyethylene ether (brand: TX-10), and add deionized water to a total weight of 45 g to obtain a black shadow liquid.

[0061] The mass proportion of alkylphenol polyoxyethylene ether in the black shadow liquid prepared in this embodiment is 0.8‰.

[0062] Example 4

[0063] This embodiment provides a method for preparing a black shadow liquid, comprising:

[0064] (1) 24 g of conductive paste, 1.2 g of ethylene glycol and 0.8 g of sodium carboxymethyl cellulose were mixed, and the pH was adjusted to 8 using potassium carbonate and potassium bicarbonate to obtain an initial black shadow liquid, wherein the mass percentage of the conductive material in the conductive paste was 9%, and the conductive material was graphite and carbon black in a mass ratio of 6:1.

[0065] (2) Mix the initial black shadow liquid obtained in step (1) and 0.0675 g of alkylphenol polyoxyethylene ether (brand: TX-10), and add deionized water to a total weight of 45 g to obtain a black shadow liquid.

[0066] The mass proportion of alkylphenol polyoxyethylene ether in the black shadow liquid prepared in this embodiment is 1.5‰.

[0067] Example 5

[0068] This embodiment provides a method for preparing a black shadow liquid, comprising:

[0069] (1) 24 g of conductive paste, 3 g of ethylene glycol and 2.4 g of sodium carboxymethyl cellulose were mixed, and the pH was adjusted to 12 using potassium carbonate and potassium bicarbonate to obtain an initial black shadow liquid, wherein the mass percentage of the conductive material in the conductive paste was 7.5%, and the conductive material was graphite and carbon black in a mass ratio of 8:1.

[0070] (2) Mix the initial black shadow liquid obtained in step (1) and 0.0045 g of alkylphenol polyoxyethylene ether (brand: TX-10), and add deionized water to a total weight of 45 g to obtain a black shadow liquid.

[0071] The mass proportion of alkylphenol polyoxyethylene ether in the black shadow liquid prepared in this embodiment is 0.1‰.

[0072] Example 6

[0073] This embodiment provides a method for preparing a shadow liquid, which is the same as that of Embodiment 1 except that the pH value is adjusted to 7 in step (1).

[0074] Example 7

[0075] This embodiment provides a method for preparing a shadow liquid, which is the same as that of Embodiment 1 except that the pH value is adjusted to 13 in step (1).

[0076] Comparative Example 1

[0077] This comparative example provides a method for preparing a black shadow liquid, which is the same as Example 1 except that no alkylphenol polyoxyethylene ether is added.

[0078] Comparative Example 2

[0079] This comparative example provides a method for preparing a black shadow liquid, which is the same as that of Example 1 except that the alkylphenol polyoxyethylene ether in Example 1 is replaced by an equal amount of sodium dodecylbenzene sulfonate.

[0080] Comparative Example 3

[0081] This comparative example provides a method for preparing a black shadow liquid, which is the same as Example 1 except that 0.1125 g of alkylphenol polyoxyethylene ether (brand: TX-10) is added in step (2).

[0082] The mass proportion of alkylphenol polyoxyethylene ether in the black shadow liquid prepared in this comparative example is 2.5‰.

[0083] Comparative Example 4

[0084] This comparative example provides a method for preparing a black shadow liquid, which is the same as Example 1 except that 0.00225 g of alkylphenol polyoxyethylene ether (brand: TX-10) is added in step (2).

[0085] The mass proportion of alkylphenol polyoxyethylene ether in the black shadow liquid prepared in this comparative example is 0.05‰.

[0086] Performance Test:

[0087] The blackening process is as follows: at room temperature, using the 72 holes of the backlight plate as a reference, the backlight plate is placed in a cleaning and pore-forming agent for 70 seconds, then the backlight plate is taken out and rinsed, and then added to the black shadow liquid for 60 seconds, and then fixed for 15 seconds, washed and dried, and micro-etched for 15 seconds, and finally washed and dried again. After the whole process is blackened twice, the double-sided resistance of the backlight plate is tested, and the bubbling and precipitation phenomena of the black shadow liquid are recorded. The test results are shown in Table 1.

[0088] Table 1

[0089]

[0090]

[0091] The test results of Examples 1 to 5 prove that the present invention improves the hydrophilicity of the graphite surface by optimizing the type and ratio of surfactants and using only a very small amount of polyoxyethylene ether surfactants, thereby promoting the uniform distribution of graphite particles in the dispersion medium, avoiding the re-aggregation of graphite flakes, improving the long-term stability and dispersibility of the black shadow liquid, solving the problems of black shadow liquid precipitation and stratification, significantly improving the long-term stability of the black shadow liquid, making it have good recycling performance, reducing the need for frequent liquid replacement, and thus reducing production costs.

[0092] According to the data results of Example 1, Example 6 and Example 7, if the pH of the black shadow liquid is adjusted to be too low, the black shadow liquid will bubble, the black hole formation will be uneven, and more precipitation will appear after standing for 12 hours, that is, the dispersibility and stability of the black shadow liquid will be significantly reduced. If the pH of the black shadow liquid is adjusted to be too high, the resistance value of the backlight panel will be too large, and the black hole effect will be significantly deteriorated.

[0093] According to the test results of Comparative Examples 1 and 2, if polyoxyethylene ether surfactants are not added or other types of surfactants, such as sodium dodecylbenzene sulfonate, are added, not only will the black shadow liquid foam significantly, affecting the uniformity of black hole formation, but also a large amount of precipitation will appear after standing for 12 hours, and the dispersion stability will be significantly reduced. More importantly, the black hole effect will also be significantly reduced, and the resistance value of the backlight panel will be too large.

[0094] According to the data results of Example 1 and Comparative Examples 3 and 4, if the polyoxyethylene ether surfactant is added in excessive amounts, the foaming phenomenon of the black shadow liquid will be significantly enhanced during use, the backlight panel and the black shadow liquid will be in uneven contact, resulting in the black hole effect being affected and the resistance value of the backlight panel being significantly increased. If the polyoxyethylene ether surfactant is added in insufficient amounts, the amount of precipitation in the black shadow liquid will increase significantly after standing, the dispersion stability of the black shadow liquid will be significantly reduced, the black hole effect will be affected, and the resistance value of the backlight panel will be increased.

[0095] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a black shadow liquid, characterized in that: The preparation method comprises: Mixing conductive paste, dispersant, pH adjuster, stabilizer and polyoxyethylene ether surfactant to prepare the black shadow liquid; In the black shadow liquid, the mass proportion of the polyoxyethylene ether surfactant is 0.1‰-2‰.

2. The preparation method according to claim 1, characterized in that The polyoxyethylene ether surfactant includes any one or a combination of at least two of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether or nonylphenol polyoxyethylene ether phosphate; Preferably, in the black shadow liquid, the mass proportion of the polyoxyethylene ether surfactant is 0.2‰-1.2‰.

3. The preparation method according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: firstly mixing a conductive paste, a dispersant, a pH regulator and a stabilizer to obtain an initial black shadow liquid, and then adding a polyoxyethylene ether surfactant to prepare the black shadow liquid.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The mass ratio of the dispersant to the conductive paste is 1:(8-20), preferably 1:(10-15); Preferably, the dispersant includes any one of ethylene glycol, sodium polyacrylate or polyvinyl pyrrolidone, or a combination of at least two thereof.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The mass ratio of the stabilizer to the conductive paste is 1:(10-30), preferably 1:(15-25); Preferably, the stabilizer includes any one of sodium carboxymethyl cellulose, carboxymethyl cellulose or carboxyethyl cellulose, or a combination of at least two thereof.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The pH of the shadow liquid is 8-12, preferably 9-11.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The pH regulator includes any one of potassium carbonate, potassium bicarbonate, sodium carbonate, sodium bicarbonate, sodium hydroxide or potassium hydroxide, or a combination of at least two thereof; Preferably, the pH adjuster comprises a combination of potassium carbonate and potassium bicarbonate.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The conductive paste includes a conductive material; Preferably, the mass percentage of the conductive material in the conductive paste is 7%-9%; Preferably, the conductive material includes any one of graphite, carbon black, carbon nanotubes or graphene, or a combination of at least two thereof; Preferably, the conductive material comprises a combination of graphite and carbon black; Preferably, the mass ratio of graphite to carbon black is (5-9):

1.

9. A black shadow liquid, characterized in that: The black shadow liquid is prepared by the preparation method according to any one of claims 1 to 8.

10. An application of the black shadow liquid as claimed in claim 9, characterized in that: The black shadow liquid is used for black hole formation of printed circuit boards.

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