Coating for electroless plating process and method for producing the same

Abstract

This application discloses a coating for electroless plating and its preparation method, belonging to the field of three-dimensional precision machining. The coating is applied to the surface of a substrate and, based on its mass percentage, comprises: 55%–85% crosslinking product of epoxy resin AB agent, 1%–5% nano-metal particles, and 10%–40% water-soluble polymer. Using the coating of this application for electroless plating involves fewer process steps and results in excellent adhesion between the metal circuitry and the substrate in the prepared three-dimensional interconnected molded device.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of three-dimensional precision machining, in particular to a coating for electroless plating process and a preparation method thereof. BACKGROUND

[0002] 3D-MID (Three-dimensional Mechatronic Integrated Device), also known as conformal circuit, is a technology of integrating three-dimensional solid circuit with a line width of 0.3 mm in a plastic shell, manufacturing three-dimensional solid circuit and interconnection device with electrical function.

[0003] In the manufacturing of three-dimensional interconnection molding devices, the laser direct structuring (LDS) process is one of the mainstream technologies for realizing selective metallization. The process forms a catalytic center by laser activation on a special LDS plastic containing special additives, and then realizes line forming through electroless plating. However, this technical route has limitations, i.e., the substrate material is strictly locked to the special LDS plastic, which often cannot match the mechanical properties and cost of widely used general engineering plastics.

[0004] To break through the material limitation, alternative processes such as laser activation forming (LAP) have been developed in the industry. First, a general plastic substrate is roughened on the surface through physical methods such as laser engraving or sandblasting to enhance the bonding force, then immersed in an activation solution containing palladium and other catalysts to adsorb catalytic centers, and finally electroless plated. This method eliminates the dependence on LDS special materials, but introduces an additional pretreatment step, increasing the production cycle and cost, and the severe physical roughening process may damage the precise surface structure or appearance of the product, affecting the precision and yield of the product.

[0005] Therefore, the current three-dimensional interconnection molding device preparation process is complex and costly. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application provides a coating for electroless plating process and a preparation method thereof, aiming to solve the problem of complex and high-cost three-dimensional interconnection molding device preparation process.

[0007] To achieve the above-mentioned purpose, the present application provides a coating for electroless plating process, which is arranged on the surface of a substrate, and based on the mass percentage of the coating, the coating comprises: 55% to 85% of the crosslinked product of epoxy resin AB agent, 1% to 5% of nano-metal particles, and 10% to 40% of water-soluble polymer.

[0008] In some embodiments, the coating is a porous structure, and under microscopic observation, the sum of the areas of the surface micropores in the observation area is 10% to 40% of the total area of the observation area.

[0009] In some embodiments, the thickness of the coating is 5um-40um.

[0010] In some embodiments, the particle size Dv50 of the nano metal particles is 1nm-200nm.

[0011] In some embodiments, the epoxy AB agent comprises an A agent and a B agent, the A agent comprises at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, and the B agent comprises at least one of polyether amine, alicyclic amine, aromatic amine or polyamide.

[0012] In some embodiments, the mass ratio of the A agent to the B agent is 1:(0.1-0.3).

[0013] In some embodiments, the viscosity of the A agent at 25℃ is less than or equal to 2000mPa·s.

[0014] In some embodiments, the nano metal particles comprise at least one of gold, silver, nickel, copper; and / or, the water-soluble polymer comprises at least one of starch, polyacrylamide, polyvinylpyrrolidone; and / or, the substrate comprises at least one of engineering plastic, ceramic, glass.

[0015] To achieve the above-mentioned purposes, the present application further provides a preparation method of the coating, comprising the following steps:

[0016] adding water-soluble resin, metal nano powder and solvent into the B agent of the epoxy AB agent to obtain a mixed product;

[0017] adding the mixed product into the A agent of the epoxy AB agent to obtain a coating slurry;

[0018] arranging the coating slurry on the surface of the electroless plated substrate, and drying to obtain the coating.

[0019] In some embodiments, the drying comprises first normal temperature drying for 10min-2h, and then temperature increasing drying for 10min-30min, the temperature of the temperature increasing drying is 50℃-200℃.

[0020] The present application has the following advantages:

[0021] The coating of this application can be independently applied to various general-purpose 3D-MID materials, eliminating the reliance on expensive and performance-limited specialized LDS plastics. Furthermore, since no additional physical roughening pretreatment such as laser engraving or sandblasting is required for the substrate, the complex process is simplified to a direct chemical plating process after coating, significantly reducing processing costs and potential product damage risks. The water-soluble polymers in the coating dissolve in the chemical plating solution, forming a micro-nano-scale porous structure on the surface. The chemically deposited metal can fully penetrate and fill these pores, forming an internal bond within the coating. This results in a more reliable adhesion compared to relying solely on the surface roughness of the substrate, leading to durable and more stable 3D interconnected molded devices with superior metal circuitry. Attached Figure Description

[0022] The embodiments described in this application are not limited to the accompanying drawings, which are only some of the embodiments described herein. Those skilled in the art can obtain drawings of other embodiments based on the content of this application.

[0023] Figure 1 This is a scanning electron microscope image of an embodiment of this application.

[0024] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0025] To make the technical solutions and advantages of this application clearer, the application and its beneficial effects will be described in further detail below in conjunction with specific embodiments. The following description is provided to enable those skilled in the art to fully understand this application and is not intended to limit the subject matter recorded in the claims.

[0026] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0027] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0028] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0029] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0030] Currently, the fabrication processes for three-dimensional interconnected molding devices, such as LDS and LAP processes, are complex and costly.

[0031] In view of this, this application proposes a coating for a chemical plating process, wherein the coating is applied to the surface of a substrate and, based on the mass percentage of the coating, comprises: 55% to 85% of crosslinking product of epoxy resin AB agent, 1% to 5% of nano-metal particles and 10% to 40% of water-soluble polymer.

[0032] In this method, an epoxy resin coating containing nano-metal particles and water-soluble polymers is directly applied to a clean, smooth, general-purpose plastic substrate via spraying or printing, and only applied to the patterned areas where circuitry is to be formed. The coating itself has excellent adhesion, eliminating the need for pre-roughening of the substrate. A single application simultaneously completes the pattern setup and plating preparation, omitting the roughening and overall activation processes required for traditional substrate patterning. Furthermore, because the coating contains pre-embedded nano-metal particles, coating activation and catalytic center formation are also simultaneously achieved.

[0033] The crosslinking products of epoxy resin AB agent provide a good adhesion substrate, ensuring the initial bond strength between the coating and various substrates. Simultaneously, its crosslinked network possesses a certain degree of flexibility, which can alleviate internal stress during metal deposition and prevent crack formation. Nanoscale metal particles not only catalyze the deposition process but also form a metallurgical bond with the deposited metal, further enhancing the continuity of the interface. (Refer to...) Figure 1 Water-soluble polymers partially dissolve or seep out during the curing of the coating in the electroless plating line, forming a uniform micro-nano-scale porous structure. During the electroless plating process, the metal is deposited and seeps into the porous structure of the coating, which is more robust than relying solely on chemical bonding or rough surface bonding.

[0034] Therefore, by specifying the above three materials within the above range, the chemical plating process for metal circuits using the coating of this solution requires less material and can significantly improve the bonding force between the metal circuits and the substrate in three-dimensional interconnected molded devices.

[0035] For example, the crosslinking product of epoxy resin AB agent may account for 55%, 60%, 65%, 70%, 75%, 80%, 85% of the coating, or fall within the range of any two of the above values.

[0036] For example, the proportion of nano-metal particles in the coating can be 1%, 2%, 3%, 4%, 5%, or within any two of the above values.

[0037] For example, the proportion of water-soluble polymers in the coating can be, or fall within the range of any two of the above values.

[0038] In some embodiments, the selection of epoxy resin (i.e., agent A) in epoxy resin AB agent needs to be based on a comprehensive consideration of its adhesion to the specific material and its compatibility with the added water-soluble resin. Generally, the degree of polymerization should not be too high, and this can be controlled by limiting the viscosity of the epoxy resin.

[0039] In some embodiments, the coating has a porous structure, and under microscopic observation, the sum of the areas of the surface micropores in the observation area is 10% to 40% of the total area of ​​the observation area.

[0040] A network of interconnected pores (10%–40%) forms a highly efficient capillary network. The electroless plating solution can quickly and uniformly wet the entire patterned coating area, ensuring consistent initiation of the plating reaction. Conversely, if the porosity is too low, metal deposition mainly occurs on the coating surface, resulting in a weak interlocking structure that cannot generate significant mechanical bonding force, limiting the improvement in adhesion. Excessively high porosity weakens the integrity of the epoxy resin network, leading to a decrease in the coating's cohesive strength, potentially causing coating peeling or cracking during electroless plating or subsequent device use.

[0041] Preferably, the sum of the areas of the surface micropores in the observation area is 20% to 35% of the total area of ​​the observation area.

[0042] In some embodiments, the coating thickness is 5µm to 40µm.

[0043] If the coating is too thin, even if there are pores, it cannot provide enough depth for metal growth during chemical plating, resulting in weak adhesion of the metal lines to the substrate. At the same time, the coating itself will introduce internal stress when applied to the substrate. An excessively thick coating may generate greater stress due to curing shrinkage or mismatch with the thermal expansion coefficient of the substrate, increasing the risk of warping or peeling.

[0044] For example, the coating thickness is 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, or within any two of the above values.

[0045] Preferably, the coating thickness is 15µm to 35µm.

[0046] In some embodiments, the particle size Dv50 of the nano-metal particles is 1 nm to 200 nm.

[0047] Dv50 (median particle size by volume fraction) is a key parameter characterizing the size distribution of the particle population, indicating that 50% of the particles in a sample are smaller than this value. When the particle size of nano-metal particles falls within this range, higher catalytic activity, dispersion stability, and compatibility with the coating's pore structure can be achieved, enabling the electroless plating reaction to occur efficiently, uniformly, and controllably.

[0048] For example, the particle size Dv50 of the nano-metal particles is 1nm, 21nm, 41nm, 61nm, 81nm, 101nm, 121nm, 141nm, 161nm, or 181nm, or falls within the range of any two of the above values.

[0049] In some embodiments, the epoxy resin AB agent includes agent A and agent B. Agent A includes at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and phenolic epoxy resin, and agent B includes at least one of polyetheramine, alicyclic amine, aromatic amine, or polyamide.

[0050] As the continuous phase and structural framework of the coating, the type of epoxy resin system and the choice of curing agent directly determine the mechanical strength, adhesion and chemical resistance of the coating. The synergistic effect with the substrate and other components should be comprehensively considered when making the selection.

[0051] In some embodiments, when the 3D-MID device is used in a high-strength and high-heat-resistant environment, agent A can be phenolic epoxy resin and agent B curing agent can be aromatic amine; when the 3D-MID device is used in applications requiring high toughness and weather resistance, agent A can be bisphenol A / F type epoxy resin and agent B curing agent can be polyetheramine or polyamide; when the 3D-MID device requires more precise post-processing and application, agent A can be low-viscosity bisphenol F type epoxy resin and agent B curing agent can be low-viscosity alicyclic amine or polyamide.

[0052] In some embodiments, the mass ratio of agent A to agent B is 1:(0.1~0.3).

[0053] A lower proportion of agent B results in less curing shrinkage stress, which helps reduce the deformation impact on precision plastic substrates. At the same time, it can form a more ideal phase separation structure, which is conducive to the stable implementation of more precise spraying, printing and other patterned construction on the substrate.

[0054] For example, the mass ratio of agent A to agent B is 1:0.1, 1:0.15, 1:0.2, 1:0.25, 1:0.3, or within any range of two of the above ratios.

[0055] In some embodiments, the viscosity of agent A at 25°C is less than or equal to 2000 mPa·s.

[0056] From the perspective of coating materials, in low-viscosity media, mechanical stirring or ultrasonic treatment can more effectively overcome the van der Waals forces between particles, achieving uniform and stable dispersion of nano-metal particles. The low-viscosity environment facilitates the full miscibility of water-soluble polymers with the system, laying the foundation for controllable and uniform phase separation during subsequent curing.

[0057] From an application perspective, the coating needs to be precisely applied to specific areas of the three-dimensional plastic device to form a circuit pattern. Application methods include precision spraying, inkjet printing, and screen printing. By limiting the viscosity of agent A and its ratio with agent B, the crosslinking strength can be controlled within a certain range, which is beneficial for balancing the accuracy of pattern application and coating strength.

[0058] In some embodiments, the nano-metal particles include at least one of gold, silver, nickel, and copper. These four metals are all effective catalysts for mainstream electroless copper plating solutions, enabling them to be adapted to a wider range of electroless plating processes.

[0059] In some embodiments, the water-soluble polymer includes at least one of starch, polyacrylamide, and polyvinylpyrrolidone. Using the above materials, the water-soluble polymer can work synergistically with the previously defined epoxy resin system and nano-metal particles to achieve controllable pore formation. Furthermore, the low cross-linking density network generated by the previously set A:B agent mass ratio of 1:0.1-0.3 is more compatible with the above water-soluble polymer.

[0060] In some embodiments, the substrate includes at least one of engineering plastics, ceramics, and glass.

[0061] In some embodiments, the substrate is preferably an engineering plastic, including polyetheretherketone (PEEK), polycarbonate (PC), polyamide (nylon, polyamide, PA), polyacetal (polyoxymethylene, POM), polyphenylene ether (PPO), polyester (PET, PBT), polyphenylene sulfide (PPS), polyarylate, etc.

[0062] According to some embodiments of this application, regardless of how conventionally the 3D-MID substrate, electroless plating solution, electroless plating metal, electroless plating thickness, etc., are selected, as long as the above-mentioned coating is included, the 3D-MID device can obtain the aforementioned beneficial effects.

[0063] To address the aforementioned problems, this application also proposes a method for preparing the above-mentioned coating, comprising the following steps:

[0064] S1: Water-soluble resin, metal nanopowder and solvent are added to agent B of epoxy resin AB agent and mixed to obtain a mixed product;

[0065] S2: The mixed product is added to agent A of epoxy resin AB agent and mixed to obtain coating slurry;

[0066] S3: The coating slurry is applied to the surface of the chemical plating substrate and dried to obtain the coating.

[0067] In some embodiments, the solvent may be a small molecule fatty alcohol, such as ethanol or IPA, or an alcohol ether solvent, such as ethylene glycol methyl ether or propylene glycol methyl ether, or other high-boiling-point co-solvents, such as PMA.

[0068] In some embodiments, the coating slurry is applied to the substrate by methods such as brushing, dipping, spraying, or inkjet dispensing.

[0069] In some embodiments, drying includes first drying at room temperature for 10 minutes to 2 hours, and then drying at a higher temperature for 10 minutes to 30 minutes, wherein the temperature for the higher temperature drying is 50°C to 200°C.

[0070] During drying at room temperature, most of the low-boiling-point solvents such as ethanol and IPA slowly and uniformly evaporate, allowing the polymer chain segments to slowly rearrange, laying the foundation for the subsequent formation of a uniform microphase separation structure. Subsequently, heating to 50℃~200℃ provides activation energy for the reaction, significantly accelerating the crosslinking reaction between the epoxy resin and the amine curing agent. The epoxy network begins to form rapidly, and the coating transforms from a viscous liquid state to a solid state with mechanical strength.

[0071] The technical solution of this application will be further described in detail below with reference to specific embodiments.

[0072] Example 1:

[0073] 12g of polyvinylpyrrolidone, 1g of silver nanoparticles with a particle size Dv50 of 10nm and 10g of ethanol were added to 6g of diethylaminopropylamine curing agent and mixed. The mixture was stirred evenly at room temperature to obtain a mixed product.

[0074] The mixed product was added to 18g of epoxy resin E51 (CAS:61788-97-4) and mixed. The mixture was stirred evenly at room temperature to obtain a coating slurry, wherein the viscosity of epoxy resin E51 at 25℃ was 650mPa·s.

[0075] The coating slurry was brushed onto the surface of the polyetheretherketone substrate according to the target pattern. It was first dried at room temperature for 10 minutes, and then heated to 200℃ and dried for 10 minutes to obtain a coating with a thickness of 10 μm. After cooling, chemical plating was performed, first copper plating of 10 μm, and then nickel plating of 2 μm to obtain a three-dimensional molded interconnect device.

[0076] Example 2:

[0077] The amount of polyvinylpyrrolidone used was 15.6g, the amount of nano silver powder was 0.4g, and the rest were as described in Example 1.

[0078] Example 3:

[0079] The amount of epoxy resin E51 used was 31.76g, the amount of curing agent phthalic anhydride used was 10.59g, the amount of nano silver powder used was 2.12g, the amount of polyvinylpyrrolidone used was 4.23g, and the rest were the same as in Example 1.

[0080] Example 4:

[0081] The coating thickness is 20 micrometers, and the rest is as described in Example 1.

[0082] Example 5:

[0083] The coating thickness is 40 micrometers, and the rest is as described in Example 1.

[0084] Example 6:

[0085] The nano-metal particles are copper with a particle size of 100 nm, and the rest are as described in Example 1.

[0086] Example 7:

[0087] The nano-metal particles are nickel with a particle size of 200 nm. Other details are as described in Example 1.

[0088] Example 8:

[0089] The water-soluble polymer is starch; other details are as described in Example 1.

[0090] Example 9:

[0091] Epoxy resin A is bisphenol F diglycidyl ether (CAS: 2095-03-6), and other details are as described in Example 1.

[0092] Comparative Example 1:

[0093] No water-soluble polymer components were added; other details are as per Example 1.

[0094] Comparative Example 2:

[0095] No nano-metal particles were added; otherwise, refer to Example 1.

[0096] Performance testing

[0097] 1. Surface micropore area test

[0098] The sample is placed on the scanning electron microscope stage. Under conditions of accelerating voltage 3-5 kV and working distance 5-10 mm, a selected area is obtained to acquire a clear, high-resolution secondary electron image. Image analysis: The acquired SEM image is imported into the professional image analysis software MATLAB. Grayscale adjustment and thresholding are performed to clearly distinguish between pore and solid regions. The software's measurement function is used to calculate the total area of ​​all pores within the selected area and the total area of ​​the selected region.

[0099] 2. Coating thickness test

[0100] Observe the cross-section under SEM and use the built-in scale of SEM to directly measure the vertical distance from the substrate surface to the outer edge of the coating.

[0101] 3. Adhesion test

[0102] The adhesion of the three-dimensional molded interconnect devices prepared in the examples and comparative examples was tested according to the test conditions of "ASTM-D3359 Cross-cut Adhesion Test": 11 longitudinal and 11 transverse cuts were made with a cross-cut knife with uniform force and speed to form 100 1mm × 1mm squares, ensuring that the cuts penetrated the coating to the substrate. Debris in the marked areas was swept away with a soft brush. 3M 600 pressure-sensitive adhesive was then applied to the marked areas and pressed firmly until no air bubbles were present. The adhesive was then peeled off quickly and smoothly at a 60° angle within 1.0 second. The peeling of the coating within the squares was observed under sufficient light.

[0103] Adhesion evaluation includes: 5B: The cut edge is completely smooth, with no peeling within the squares. 4B: A small portion of the coating peels off, with a peeling area <5%. 3B: The coating peels off partially along the cut edge and within the squares, with a peeling area of ​​5%-15%. 2B: The coating peels off partially along the cut edge and within the squares, with a peeling area of ​​15%-35% (excluding 15%). 1B: The coating peels off over a large area along the cut edge and within the squares, with a peeling area of ​​35%-65% (excluding 35%). 0B: The peeling area is greater than 65%.

[0104] 4. Neutral salt spray test.

[0105] A 5% sodium chloride solution was prepared according to GB / T2423.17-2008 Environmental Testing for Electrical and Electronic Products, and its pH value was adjusted to 6.5-7.2 at 25℃. The sample was placed in a salt spray chamber with the test surface facing upwards at a 30° angle to the vertical. The chamber temperature was stabilized at 35℃, and the salt spray deposition rate was controlled to be 2.0 mL / h in each collection area by adjusting the spray system. The test was conducted for 12, 24, 36, or 48 hours. After the test, the sample was removed, cleaned, and dried. Finally, the corrosion condition of the main surface of the sample was examined under good lighting conditions, and the longest pass time was recorded.

[0106] The performance test results of the examples and comparative examples are shown in Table 1 below.

[0107] Table 1. Performance results of the examples and comparative examples

[0108] .

[0109] Compared with Comparative Example 1, Examples 1-9 demonstrate that the formation of microporous structures by water-soluble polymers is the key to obtaining high adhesion; compared with Comparative Example 2, Examples 1-9 demonstrate that the chemical plating process cannot be started without nano-metal particles as catalytic centers.

[0110] Compared to Example 1, Example 2 shows that increasing the amount of water-soluble polymer can increase the micropore area ratio of the coating from ~30% to ~40% without affecting adhesion and corrosion resistance. Compared to Example 1, Example 3 shows that changing the use of phthalic anhydride as the curing system leads to densification of the cross-linked network, inhibiting micropore formation and reducing adhesion and corrosion resistance, which is not as good as the optimal example. Compared to Example 1, Example 5 shows that excessive coating thickness leads to decreased adhesion, possibly due to increased internal stress or increased difficulty in metal penetration and filling. Compared to Example 1, Example 6 shows that replacing nano-silver with nano-copper can maintain adhesion, but reduces corrosion resistance because copper is more easily corroded. Compared to Example 1, Example 7 shows that replacing nano-silver with larger-particle-size nano-nickel slightly reduces adhesion due to decreased catalytic site density or binding uniformity.

[0111] The above performance results demonstrate that this application eliminates the reliance on expensive and performance-limited specialized LDS plastics. Furthermore, by eliminating the need for additional physical roughening pretreatments such as laser engraving and sandblasting of the substrate, the complex process is simplified to a direct chemical plating process after coating, significantly reducing processing costs and potential product damage risks. The water-soluble polymers in the coating dissolve in the chemical plating solution, forming a micro-nano-scale porous structure on the surface. The chemically deposited metal can fully penetrate and fill these pores, forming an internal bond within the coating. This results in a more reliable adhesion compared to relying solely on substrate surface roughness, thereby obtaining a durable and more stable three-dimensional interconnected molded device with superior metal circuitry.

[0112] Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples.

[0113] The above description is only a part or preferred embodiment of this application and should not be construed as limiting the scope of protection of this application. All equivalent structural transformations made using the content of this application specification under the overall concept of this application, or direct / indirect applications in other related technical fields, are included within the scope of protection of this application.

Claims

1. A coating for use in a chemical plating process, characterized in that, The coating is applied to the surface of the substrate, and based on the mass percentage of the coating, the coating comprises: Crosslinking products of 55%~85% epoxy resin AB agent, 1%~5% nano-metal particles, 10%~40% water-soluble polymers; The coating has a porous structure, and under a microscope, the sum of the areas of the surface micropores in the observation area is 10% to 40% of the total area of ​​the observation area. The thickness of the coating is 5µm to 40µm; The particle size Dv50 of the nano-metal particles is 1nm~200nm; The nano-metal particles include at least one of gold, silver, nickel, and copper; The water-soluble polymer includes at least one of starch, polyacrylamide, and polyvinylpyrrolidone.

2. The coating for electroless plating according to claim 1, characterized in that, The epoxy resin AB agent includes agent A and agent B. Agent A includes at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and phenolic epoxy resin. Agent B includes at least one of polyetheramine, alicyclic amine, aromatic amine, or polyamide.

3. The coating for electroless plating according to claim 2, characterized in that, The mass ratio of agent A to agent B is 3:(0.3~1).

4. The coating for electroless plating according to claim 3, characterized in that, The viscosity of agent A at 25°C is less than or equal to 2000 mPa·s.

5. The coating for electroless plating according to claim 1, characterized in that, The substrate includes at least one of engineering plastics, ceramics, and glass.

6. A method for preparing a coating as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Water-soluble polymer, nano-metal particles and solvent are added to agent B of epoxy resin AB agent and mixed to obtain a mixed product; The mixture is added to agent A of epoxy resin AB agent and mixed to obtain a coating slurry; The coating slurry is applied to the surface of a chemically plated substrate and dried to obtain a coating.

7. The method for preparing the coating according to claim 6, characterized in that, The drying process includes first drying at room temperature for 10 minutes to 2 hours, and then drying at a higher temperature for 10 minutes to 30 minutes, wherein the temperature for the higher temperature drying is 50°C to 200°C.

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