A rhodium-containing PCB substrate chemical plating activation solution and chemical plating method thereof

Abstract

The present invention provides a rhodium-containing PCB substrate chemical plating activation solution and a chemical plating method thereof, belonging to the field of chemical activation and chemical plating. First, a method for preparing an activation modification solution is provided, so that it can be used as an activation bridge layer for modifying the surface of an insulating substrate. The modification solution formula comprises: 20-40 g / L of epoxy resin, 0.03-0.06 mol / L of butanone, 0.1-0.2 g / L of triphenylphosphine carbonyl rhodium (I) acetylacetonate, 0.025-0.05 mol / L of chloroform, and 0.045-0.09 mol / L of ethylenediamine. Secondly, a sodium borohydride solution is used as a reducing agent to reduce the rhodium in the organometallic compound and effectively deposit it on the surface of the insulating substrate to form active species to catalyze chemical plating. Finally, a dense, bright, and highly adhesive coating can be formed in conjunction with a subsequent chemical plating process. The activation modification solution formula is simple to prepare, simple to operate, and has low implementation cost. It will not corrode the printed circuit substrate and process equipment, and has good compatibility with existing printed circuit manufacturing conditions.

Description

Technical Field

[0001] The invention belongs to the field of printed circuit board surface modification and activation technology and chemical plating, and particularly relates to a rhodium-containing PCB substrate chemical plating activation solution and a chemical plating method thereof. Background Art

[0002] Printed circuit boards (PCBs), as carriers of numerous devices (such as integrated circuits, resistors, capacitors, and inductors), are core components of electronic systems and are known as the "mother of electronic products." With the rapid development of modern electronic information technology and the green transformation of production methods, PCB manufacturing and research have garnered widespread attention both domestically and internationally. Currently, selective electroless plating, a key method for fabricating fine copper circuits on printed circuit boards (PCBs) using the fully additive process, effectively addresses issues such as plating bridging and plating leakage that occur with traditional metallization processes for insulating substrate surfaces. Furthermore, it avoids the drawbacks of the fully additive process for directly printing metallic conductive inks, such as the tendency of conductive inks to agglomerate, leading to clogging of the nozzle or mesh by metal nanoparticles during printing, and reduced conductivity of the conductive circuits due to dispersants and stabilizers in the conductive inks. Therefore, selective electroless plating technology for printed circuit board surfaces holds significant research value and application prospects in the development of the electronics and information industry.

[0003] Because most printed circuit board substrates have an inert surface and low surface energy, surface modification is often required. Activation treatment at pre-defined locations is a key process for producing conductive traces using selective electroless copper plating. Activation involves adsorbing a uniformly distributed layer of catalytically active metal particles onto the non-metallic surface of the insulating substrate. This allows the substrate to retain the catalyst at pre-defined locations, initiating the electroless copper plating reaction. The newly deposited copper then acts as a catalyst for copper deposition, ultimately forming copper conductive traces at the pre-defined locations. Uniform surface activation is essential for achieving high-performance electroless copper coatings. Activation treatment prior to selective electroless copper plating directly impacts the proper conduct of the electroless copper plating reaction, the uniformity and regularity of the deposited layer, and the excellent bonding between the copper layer and the insulating substrate. Research on activation solutions for selective electroless copper plating has advanced rapidly in recent years. For example, in his paper "Preparation and Application of an Activation Concentrate for Electroless Copper Plating," Yang Zhifeng developed a colloidal palladium concentrate by adding stabilizers and crystal refiners. This concentrate exhibits colloidal stability, uniform dispersion, and reduced palladium adsorption. In their paper "Preparation and Properties of Nano-palladium Activation Solution for PCB Chemical Copper Plating," Zhang Nianchun et al. use PdCl2 as a raw material, polyvinylpyrrolidone (PVP) as a dispersant, and glucose as a reducing agent to prepare a nano-palladium activation solution. This solution is then used for activation treatment prior to chemical copper plating on through-holes, resulting in a bright and smooth copper coating. The patent "Chemical Copper Plating Activation Solution and Method for Its Use" (Application Publication No.: CN 115948728A) discloses a method for preparing metal nanomaterials using reducing carbon dots to reduce another metal ion besides palladium, thereby partially replacing palladium and reducing palladium content, thereby conserving resources.

[0004] To reduce production costs and simplify process flows, the preparation of metal colloidal catalysts such as silver, copper, and nickel with excellent catalytic properties to replace palladium metal catalysts has become an important research direction. In his article "Study on Non-Colloidal Palladium Activation for Chemical Copper Plating on PET Plastics," Yu Xiong used silver nitrate to replace the palladium chloride used in the traditional two-step process, producing a highly adherent coating by electroless copper plating on PET plastic treated with alkaline potassium permanganate. The patent "A Silver Colloidal Activation Solution Composition for Chemical Copper Plating on Polymer Surfaces and Its Preparation Method" (Application Publication No.: CN115369391A) discloses a method for preparing a silver colloidal electroless copper plating activation solution. The composition has a pH of 6-9 and consists of a soluble silver salt, a first reducing agent, a second reducing agent, a stabilizer, a pH adjuster, and deionized water. The resulting silver colloidal particles have a narrow size distribution and excellent stability, exhibiting no precipitation after storage for over six months. The patent "An Activation Solution for Chemical Plating and a Method for Activating Non-metallic Surfaces" (Application Publication No.: CN101838802A) provides an activation solution for chemical copper plating containing a pyridine compound, cuprous halide, hydrohalic acid, sodium hypophosphite, and ethylene glycol. This formula effectively reduces the use of precious metals and conforms to the development concept of green environmental protection. In addition, LBLi et al. used 90g / L NaOH solution at 85°C to roughen the PI film, then soaked the PI in an activation solution containing 50g / L CuSO4 and 80g / L NaH2PO2. H2O, using sodium hypophosphite to remove Cu adsorbed on the substrate surface. 2+ The nickel is reduced to Cu; finally, electroless copper deposition is achieved on the PI surface in a copper plating solution composed of CuSO₄, EDTA, HCHO, sodium potassium tartrate, and potassium ferrocyanide. Numerous methods exist for activating insulating substrate surfaces prior to electroless plating using metallic nickel as a catalytic metal, including thermal oxidation-reduction and organic nickel thermal decomposition. The patent "Palladium-Free Activation Formula and Process for Electroless Nickel Plating on Plastic Surfaces" (Application Publication No.: CN1772950A) discloses a method for reducing nickel acetate to active metallic nickel at room temperature using sodium borohydride as a reducing agent. The insulating substrate is then placed in the activation solution for a specified period of time to produce a good coating during the electroless nickel plating reaction. While significant progress has been made in the research of selective electroless plating activation solutions, numerous challenges remain. For example, some solutions offer poor activation effects and short service lives, failing to meet industrial needs; and some processes are overly complex, resulting in significant product contamination and limited industrial feasibility. Therefore, developing a novel electroless plating activation solution for insulating substrate surfaces with a simple process and significant activation effects holds great research potential and application value.

[0005] The innovation of the present invention lies in the selection of acetylacetonate triphenylphosphine carbonyl rhodium as the core component of the invention patent. Since acetylacetonate triphenylphosphine carbonyl rhodium, as the catalyst matrix, is very stable in air and soluble in organic solvents, it can form a uniform system with PCB substrate components such as epoxy resin, thereby overcoming the shortcomings of the current PCB surface chemical plating activation system with high viscosity or immiscibility between components, and improving the catalytic efficiency of the activator before chemical plating. Summary of the Invention

[0006] The present invention addresses the problems of poor adhesion between the electroless plating layer and the substrate on the surface of printed circuit boards, uneven plating thickness, and complex activation processes in the prior art. A novel rhodium-containing PCB substrate electroless plating activation solution and an electroless plating method are provided. The organic metal compound, triphenylphosphine carbonyl rhodium acetylacetonate, is used as the catalytically active species in the insulating substrate surface modification solution. The organic metal compound, triphenylphosphine carbonyl rhodium acetylacetonate, is fully dissolved and dispersed in a chloroform solution. The rhodium in the organic metal compound is then complexed and fixed with a bisphenol A epoxy resin. Furthermore, because the epoxy resin exhibits excellent physical adsorption properties on any substrate surface, and the active epoxy groups therein can chemically bond with hydroxyl groups (-OH), carbonyl groups (C=O), or groups containing lone pairs of electrons on the substrate surface, the solution system provides excellent bonding strength between the substrate and the plating layer when forming an activated modified layer. Furthermore, sodium borohydride is used as a reducing agent to reduce the rhodium in the triphenylphosphine carbonyl rhodium acetylacetonate, resulting in a highly efficient catalytic effect and effective deposition and accumulation on the insulating substrate surface to catalyze the subsequent electroless copper plating process.

[0007] In order to achieve the above-mentioned purpose of the invention, the technical solutions adopted by the present invention are as follows:

[0008] A rhodium-containing PCB substrate surface modification and activation solution comprises the following components: 20-40 g / L of epoxy resin, 0.03-0.06 mol / L of butanone, 0.1-0.2 g / L of triphenylphosphine carbonyl rhodium (I) acetylacetonate, 0.025-0.05 mol / L of chloroform, and 0.045-0.09 mol / L of ethylenediamine.

[0009] The chemical plating method of the rhodium-containing PCB substrate chemical plating activation solution is characterized by comprising the following steps:

[0010] (1) Surface pretreatment of epoxy resin substrate: The epoxy resin substrate was placed in a beaker containing anhydrous ethanol and ultrasonically cleaned, and then rinsed with deionized water to remove the residual ethanol on the surface of the substrate, and then placed in an oven to dry to obtain a clean epoxy resin substrate;

[0011] (2) Preparation of modified activation solution: Take an appropriate amount of epoxy resin, add butanone solution dropwise, and stir magnetically at room temperature to obtain a colorless and transparent solution. Then weigh acetylacetonato triphenylphosphine carbonyl rhodium, add an appropriate amount of chloroform dropwise, and ultrasonicate at room temperature to fully dissolve the carbonyl rhodium powder. Finally, mix the obtained solution with the above colorless and transparent solution and continue magnetic stirring to obtain a light yellow transparent solution:

[0012] (3) Surface modification of epoxy resin substrate: At room temperature, add ethylenediamine solution as a curing agent to the light yellow transparent solution obtained in step (2), stir magnetically to mix evenly, and then evenly apply the solution to the clean epoxy resin substrate obtained in step (1). After the applied modification solution is cured, a modified insulating substrate board is obtained;

[0013] (4) Activation of the epoxy resin substrate surface: The modified epoxy resin substrate is placed in a reducing agent solution at 50°C for 30-40 minutes to reduce the rhodium in the organometallic compound and effectively deposit it on the surface of the insulating substrate to form active species to catalyze subsequent chemical plating;

[0014] (5) Copper deposition on the surface of the epoxy resin substrate: The epoxy resin substrate activated in step (4) is placed in a chemical plating solution for chemical deposition. During the process, air can be introduced into the plating solution to improve the stability of the plating solution. After the chemical plating is completed, it is washed with an ethanol solution and dried to obtain an epoxy resin substrate with a copper layer deposited on the surface.

[0015] As a preferred embodiment, in step (1), the epoxy resin substrate has a thickness of 0.5 mm, and the length and width are cut into a square or rectangle according to the graphic requirements. The power of the ultrasonic cleaner is 110 W, the frequency is 40 KHz, and the cleaning time is 10 min.

[0016] As a preferred embodiment, the resin used in step (2) is a bisphenol A epoxy resin, which can be effectively dissolved in a butanone solution having a strong lipophilicity, and its mass concentration is maintained at 20 to 40 g / L, and is used to complex and fix the rhodium in the organic metal compound.

[0017] As a preferred embodiment, the concentration of the curing agent ethylenediamine solution in step (3) should be controlled at 0.045-0.09 mol / L, and the curing time should be 20-30 min.

[0018] As a preferred embodiment, the reducing agent in step (4) is a sodium borohydride solution, and the molar concentration is preferably 0.3-0.6 mol / L.

[0019] As a preferred embodiment, the formula of the chemical plating solution in step (5) is as follows: 32 g / L potassium sodium tartrate tetrahydrate, 2.5 g / L disodium ethylenediaminetetraacetic acid dihydrate, 12.5 g / L copper sulfate pentahydrate, 3.5 g / L nickel sulfate hexahydrate, 10 mg / L 2,2'-bipyridine, 20 mg / L potassium ferrocyanide trihydrate, 10 g / L sodium hydroxide, and 12 ml / L formaldehyde solution.

[0020] As a preferred method, in step (5), air is blown into the plating solution during the chemical plating process to improve the stability of the plating solution, and the air flow rate is 2.5-5cm 3 / min, the chemical plating temperature is controlled at 50℃, and the chemical plating time is kept within 30-60min.

[0021] The preparation of the chemical plating activation solution and the chemical plating method thereof have the following benefits:

[0022] In this invention, rhodium has excellent catalytic performance, and its catalytic performance is 10 times that of catalysts such as Co. 2 -10 4 times; using a carbonyl metal organic compound as an active precursor for catalytic electroless copper plating, it is attached to the surface of the insulating substrate through the adhesive effect of bisphenol A epoxy resin, and at the same time, the rhodium in the organic metal compound is complexed and fixed, so that it is stably and evenly distributed in the modified solution. This modified system avoids the catalyst ions being reduced to metal nanoparticles by the epoxy groups in the epoxy resin, which causes the catalyst to agglomerate, thereby resulting in an uneven electroless copper layer. In addition, because the epoxy resin has a physical adsorption effect on any substrate surface, the active epoxy groups in it can chemically bond with the hydroxyl (-OH), carbonyl (C=O) or lone pair electron groups on the substrate surface, thereby ensuring that when the solution system is used to form an activated modified layer, it provides good bonding between the substrate and the coating. Finally, sodium borohydride solution is used as a reducing agent to reduce the rhodium in the acetylacetonatotriphenylphosphine carbonyl rhodium compound evenly distributed in the bridging layer to form catalytic active centers. In combination with the subsequent electroless copper plating process, a dense, bright, and highly adherent copper plating layer can be formed. The substrate of the present invention has the advantages of strong applicability, simple operation, uniform activation, and easily controllable reaction. The prepared modified solution is transparent, clear, and has good stability. It can be used not only in printed circuit board surface metallization processes, but also in the manufacture of fine copper circuits in additive printed circuit board manufacturing processes. The resulting product has excellent bonding strength between the substrate and the metal additive, with bonding strength reaching level 5B using the cross-grid test method (according to standard ASTM D3359). It also does not corrode printed circuit substrates and process equipment, and is highly compatible with existing printed circuit manufacturing conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1A schematic flow chart of a rhodium-containing PCB substrate chemical plating activation solution and its chemical plating method provided by the present invention;

[0024] Figure 2 This is a metallographic microscope image of an insulating substrate with the modified activation solution attached thereto according to the present invention;

[0025] Figure 3 This is a SEM image of the coating after electroless copper plating on the surface of an insulating substrate catalyzed by the modified activation solution of the present invention;

[0026] Figure 4 This is a metallographic microscope image of a cross-section after chemical copper plating on the surface of an insulating substrate catalyzed by the modified activation solution of the present invention. DETAILED DESCRIPTION

[0027] The present invention will be further described below in detail with reference to specific embodiments and the accompanying drawings. Those skilled in the art will readily appreciate the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0028] Example 1:

[0029] (1) Surface pretreatment of epoxy resin substrate: Cut the epoxy resin substrate into pieces with a length and width of 4×3 cm and a thickness of 0.5 mm, place it in a beaker filled with anhydrous ethanol and ultrasonically clean it for 10 min at an ultrasonic power of 110 W and a frequency of 40 kHz. Rinse it with a large amount of deionized water to remove the residual ethanol on the surface of the substrate, and then place it in an oven to dry at 60°C. After drying for 30 min, a clean epoxy resin substrate is obtained.

[0030] (2) Preparation of modified activation solution: Weigh 2g of bisphenol A epoxy resin into a beaker, add 3mL of butanone solution to dissolve it, set the magnetic stirrer speed to 800rpm at room temperature, and stir for 10 minutes to obtain a colorless transparent solution. Then weigh 0.01g of acetylacetonato triphenylphosphine carbonyl rhodium powder and add 2mL of chloroform solution. Ultrasonicate at room temperature for 5 minutes to fully dissolve the carbonyl rhodium powder. Finally, mix the obtained solution with the above colorless transparent solution and continue magnetic stirring for 5 minutes to obtain a light yellow transparent solution. The obtained modified activation solution contains 20g / L of epoxy resin, 0.03mol / L of butanone, 0.1g / L of acetylacetonato triphenylphosphine carbonyl rhodium, and 0.025mol / L of chloroform. Among them, bisphenol A type epoxy resin is used to complex and fix the rhodium in the acetylacetonatotriphenylphosphine carbonyl rhodium compound. At the same time, the epoxy resin has a good adsorption effect on the surface of the substrate. The active epoxy group can chemically bond with the hydroxyl group (-OH), carbonyl group (C=O) or group containing lone pair electrons on the surface of the substrate, thereby effectively ensuring that it provides excellent bonding strength between the substrate and the coating.

[0031] (3) Surface modification of epoxy resin substrate: At room temperature, 3 mL of ethylenediamine was added as a curing agent to the light yellow transparent solution obtained in step (2) at a concentration of 0.045 mol / L. After magnetic stirring at a speed of 800 rpm for 20 min, the solution was evenly applied on the clean epoxy resin substrate obtained in step (1). The solution was then placed in an oven at a temperature of 60°C to cure the modified solution to obtain a modified insulating substrate board.

[0032] (4) Surface activation of epoxy resin substrate: First, 0.456 g of sodium borohydride solid was weighed and 40 mL of deionized water was added to obtain a sodium borohydride solution with a concentration of 0.3 mol / L. Then, the modified epoxy resin substrate was placed in the sodium borohydride solution at 50 °C for 30 min to reduce the rhodium in the organometallic compound and effectively deposit it on the surface of the insulating substrate to form active species to catalyze chemical plating.

[0033] (5) Copper deposition on the surface of epoxy resin substrate: The epoxy resin substrate activated in step (4) is placed in a chemical plating solution for chemical deposition. The specific ingredients of the chemical plating solution are as follows: 32g / L potassium sodium tartrate tetrahydrate, 2.5g / L disodium ethylenediaminetetraacetic acid dihydrate, 12.5g / L copper sulfate pentahydrate, 3.5g / L nickel sulfate hexahydrate, 10mg / L 2,2'-bipyridine, 20mg / L potassium ferrocyanide trihydrate, 10g / L sodium hydroxide, and 12ml / L formaldehyde solution. The temperature of the chemical plating water bath is controlled at 50°C, and the plating time is 40min. During this period, 2.5cm of water is introduced into the plating solution. 3 / min of air to improve the stability of the plating solution, and after the chemical plating is completed, it is rinsed with ethanol solution and dried to obtain an epoxy resin substrate with a copper layer deposited on the surface.

[0034] The metallographic microscope image of the insulating substrate surface with the activation modification solution obtained in the embodiment is as follows: Figure 2 As shown in the figure, it can be seen that the activated modified liquid is evenly distributed on the surface of the insulating substrate and has good bonding force with the substrate surface.

[0035] Figure 3 This is an SEM image of the surface of the insulating substrate after chemical copper plating. From the image, it can be seen that the grain distribution on the surface of the coating is uniform, the crystal particles are refined and the crystals are dense, indicating that the surface of the copper layer on the insulating substrate after chemical copper plating with the modified activation solution of the present invention is flat and smooth, and the thickness is uniform.

[0036] Example 2:

[0037] (1) Surface pretreatment of epoxy resin substrate: Cut the epoxy resin substrate into pieces with a length and width of 4×3 cm and a thickness of 0.5 mm, place it in a beaker filled with anhydrous ethanol and ultrasonically clean it for 10 min at an ultrasonic power of 110 W and a frequency of 40 kHz. Rinse it with a large amount of deionized water to remove the residual ethanol on the surface of the substrate, and then place it in an oven to dry at 60°C. After drying for 30 min, a clean epoxy resin substrate is obtained.

[0038] (2) Preparation of modified activation solution: Weigh 4 g of epoxy resin into a beaker, add 6 mL of butanone solution to dissolve it, set the magnetic stirrer to 800 rpm at room temperature, and stir for 15 minutes to obtain a colorless transparent solution. Then weigh 0.02 g of acetylacetonato triphenylphosphine carbonyl rhodium powder, add 4 mL of chloroform solution, and ultrasonicate at room temperature for 5 minutes to fully dissolve the carbonyl rhodium powder. Finally, mix the obtained solution with the above colorless transparent solution and continue magnetic stirring for 5 minutes to obtain a light yellow transparent solution. The obtained modified activation solution contains 40 g / L of epoxy resin, 0.06 mol / L of butanone, 0.2 g / L of acetylacetonato triphenylphosphine carbonyl rhodium, and 0.05 mol / L of chloroform.

[0039] (3) Surface modification of epoxy resin substrate: At room temperature, 6 mL of ethylenediamine was added as a curing agent to the light yellow transparent solution obtained in step (2) at a concentration of 0.09 mol / L. After magnetic stirring at a speed of 800 rpm for 20 min, the solution was evenly applied on the clean epoxy resin substrate obtained in step (1). The solution was then placed in an oven at a temperature of 60°C to cure the modified solution to obtain a modified insulating substrate board.

[0040] (4) Surface activation of epoxy resin substrate: First, 0.76 g of sodium borohydride solid was weighed and 40 mL of deionized water was added to obtain a sodium borohydride solution with a concentration of 0.5 mol / L. Then, the modified epoxy resin substrate was placed in the sodium borohydride solution at 50 °C for 40 min to reduce the rhodium in the organometallic compound and effectively deposit it on the surface of the insulating substrate to form active species to catalyze chemical plating.

[0041] (5) Copper deposition on the surface of epoxy resin substrate: The epoxy resin substrate activated in step (4) is placed in a chemical plating solution for chemical deposition. The specific ingredients of the chemical plating solution are as follows: 32g / L potassium sodium tartrate tetrahydrate, 2.5g / L disodium ethylenediaminetetraacetic acid dihydrate, 12.5g / L copper sulfate pentahydrate, 3.5g / L nickel sulfate hexahydrate, 10mg / L 2,2'-bipyridine, 20mg / L potassium ferrocyanide trihydrate, 10g / L sodium hydroxide, and 12ml / L formaldehyde solution. The temperature of the chemical plating water bath is controlled at 50°C, and the plating time is 30min. During this period, 5cm of water is introduced into the plating solution. 3 / min of air to improve the stability of the plating solution, and after the chemical plating is completed, it is rinsed with ethanol solution and dried to obtain an epoxy resin substrate with a copper layer deposited on the surface.

[0042] The metallographic microscope image of the section after chemical copper plating on the surface of the insulating substrate of the present invention is as follows: Figure 4 As shown in the figure, it can be seen that after electroless copper plating on the insulating substrate with the modified activation solution of the present invention, a metal copper layer with uniform thickness can be effectively deposited.

[0043] The embodiments described above are intended only to illustrate the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the embodiments described above without departing from the spirit and scope of the present invention. Therefore, any equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A chemical plating method for a rhodium-containing PCB substrate chemical plating activation solution, characterized in that: The following steps are involved: S1: Surface pretreatment of epoxy resin substrate: The epoxy resin substrate was placed in a beaker of anhydrous ethanol for ultrasonic cleaning, and then rinsed with deionized water to remove the residual ethanol on the surface of the substrate. The substrate was then dried in an oven to obtain a clean epoxy resin substrate. S2: Preparation of modified activation solution: Take epoxy resin, add butanone solution dropwise, and stir magnetically at room temperature to obtain a colorless transparent solution, then weigh acetylacetonate triphenylphosphine carbonyl rhodium (I), and add chloroform dropwise, and ultrasonically dissolve acetylacetonate triphenylphosphine carbonyl rhodium (I) powder at room temperature, and finally mix the obtained solution with the above colorless transparent solution and continue magnetic stirring to obtain a light yellow transparent solution, that is, obtain a rhodium-containing PCB substrate surface modification activation solution, the activation solution includes 20-40 g / L epoxy resin, 0.03-0.06 mol / L butanone, 0.1-0.2 g / L acetylacetonate triphenylphosphine carbonyl rhodium (I), and 0.025-0.05 mol / L chloroform; S3: Surface modification of epoxy resin substrate: At room temperature, add ethylenediamine solution as a curing agent to the light yellow transparent solution obtained in step S2, stir magnetically to mix thoroughly, and then evenly apply the solution to the clean epoxy resin substrate obtained in step S1. After the applied modification solution is cured, a modified insulating substrate board is obtained; S4: Surface activation of epoxy resin substrate: placing the modified epoxy resin substrate in a reducing agent solution at 50°C for 30-40 minutes to reduce triphenylphosphine carbonyl rhodium (I) acetylacetonate and deposit it on the surface of the insulating substrate; S5: Copper deposition on the surface of the epoxy resin substrate: The epoxy resin substrate activated in step S4 is placed in an electroless copper plating solution for chemical deposition, during which air is introduced into the plating solution to improve the stability of the plating solution. After the electroless plating is completed, it is washed with an ethanol solution and dried to obtain an epoxy resin substrate with a copper layer deposited on the surface.

2. The chemical plating method of a rhodium-containing PCB substrate chemical plating activation solution according to claim 1, wherein In step S1, the epoxy resin substrate has a thickness of 0.5 mm, and the length and width are cut into a square or rectangle according to the graphic requirements. The power of the ultrasonic cleaner is 110 W, the frequency is 40 KHz, and the cleaning time is 10 minutes.

3. A chemical plating method for a rhodium-containing PCB substrate chemical plating activation solution according to claim 2, characterized in that, The epoxy resin used in step S2 is bisphenol A epoxy resin.

4. The chemical plating method of a rhodium-containing PCB substrate chemical plating activation solution according to claim 3, wherein The concentration of the ethylenediamine solution in step S3 is controlled to be 0.045-0.09 mol / L, and the curing time is 20-30 min.

5. A chemical plating method for a rhodium-containing PCB substrate chemical plating activation solution according to claim 4, characterized in that, The reducing agent in step S4 is a sodium borohydride solution with a molar concentration of 0.3-0.6 mol / L.

6. a chemical plating method of a rhodium-containing PCB substrate chemical plating activation solution according to claim 5, is characterized in that, The formula of the chemical copper plating solution in step S5 is as follows: 32 g / L potassium sodium tartrate tetrahydrate, 2.5 g / L disodium ethylenediaminetetraacetic acid dihydrate, 12.5 g / L copper sulfate pentahydrate, 3.5 g / L nickel sulfate hexahydrate, 10 mg / L 2,2'-bipyridine, 20 mg / L potassium ferrocyanide trihydrate, 10 g / L sodium hydroxide, and 12 ml / L formaldehyde solution.

7. A chemical plating method for a rhodium-containing PCB substrate chemical plating activation solution according to claim 6, characterized in that, When air is introduced into the plating solution in step S5, the air flow rate is 2.5-5 cm 3 / min, the chemical plating temperature is controlled at 50℃, and the chemical plating time is kept within 30-60min.

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