An efficient complexing electroless copper plating solution and its preparation method

Abstract

The present application provides an efficient complexing electroless copper plating solution. The components of the copper plating solution include: a copper source, a nickel source, an organic compound having at least one N heterocycle, a complexing agent, an accelerator, a reducing agent, a surfactant, and a pH regulator; the organic compound having at least one N heterocycle is selected from any one or a combination of several of phenanthroline-based, imidazole-based, pyridine-based, and bipyridine-based compounds; through the synergistic effect of each component, the copper plating solution of the present application can produce a complexing effect with copper ions and complex with reaction by-products, so that the copper solution has excellent stability, high activity, can prepare a copper coating with high thickness and high plating rate at a lower temperature, the copper plating rate is significantly improved, and the performance of the copper coating is excellent.

Description

Technical Field

[0001] The invention relates to the technical field of C23C, and in particular to a high-efficiency complex-type chemical copper plating solution and a preparation method thereof. Background Art

[0002] Chemical copper plating is a copper plating method for PCB circuit boards. The chemical plating solution is mainly composed of copper salts, reducing agents, complexing agents, stabilizers, pH regulators, etc. In the copper plating reaction, in addition to the copper ions being reduced to elemental copper, there are many side reactions, including connica reaction and non-catalytic reaction. During the process, cuprous ions react to generate copper and copper ions. The side reaction products of the cuprous ions are distributed in the electroplating solution, which will significantly reduce the stability of the plating solution, leading to decomposition of the plating solution, and making the copper coating loose and rough, with poor bonding with the substrate and other undesirable phenomena. Therefore, how to stabilize the copper plating solution, improve the copper plating efficiency and the quality of the copper plating layer are the main problems that need to be solved in this application.

[0003] Chinese patent CN102191491A discloses a chemical copper plating solution and a chemical copper plating method, which effectively improves the stability of the copper plating solution by using a stabilizer N-methylmorpholine, but the working temperature of the copper plating solution is 30-50°C to achieve a thick plating effect, the activity of the plating solution is insufficient, and the copper plating efficiency is also low. Chinese patent CN114540889A discloses a copper plating additive, a copper plating solution and its application to solve the defects of uneven coating and insufficient bright appearance of the coating in cyanide-free brush copper plating, but its technology cannot achieve high-speed and high-thickness copper plating, and the copper plating solution cannot adapt to different electroplating substrates, and the scope of use is relatively narrow. Summary of the invention

[0004] In order to solve the above technical problems, the present invention first provides a high-efficiency complex-type chemical copper plating solution, the components of which include: a copper source, a nickel source, an organic matter having at least one N heterocycle, a complexing agent, an accelerator, a reducing agent, a surfactant, and a pH regulator.

[0005] Furthermore, the copper source is Cu 2+ The solution is selected from a combination of one or more of cupric sulfate pentahydrate, cupric chloride, cupric nitrate, basic cupric carbonate, and copper sulfamate.

[0006] Furthermore, the concentration of the copper source in the copper plating solution is 4-15 g / L, preferably 5-12 g / L.

[0007] Furthermore, the nickel source is Ni 2+ The solution includes, but is not limited to, one or more of nickel sulfate hexahydrate, nickel chloride hexahydrate, nickel nitrate, nickel acetate, nickel carbonate, and nickel sulfamate.

[0008] Further, the concentration of the nickel source in the copper plating solution is 0.05 - 1 g / L, preferably 0.1 - 0.5 g / L.

[0009] Further, the organic compound having at least one N heterocycle is selected from any one or a combination of several of phenanthroline, imidazole, pyridine, bipyridine.

[0010] Further, the phenanthroline has the following structure:

[0011]

[0012] Among them, R1 and R2 are selected from any one of C0 - C20 alkyl groups with polar groups or their salts; the polar groups include, but are not limited to, any one or a combination of several of amino group, primary amino group, secondary amino group, tertiary amino group, hydroxyl group, ether bond, carboxyl group, mercapto group.

[0013] Further, the imidazole has the following structure:

[0014]

[0015] Among them, R3, R4 and R5 are selected from any one or a combination of several of C1 - C20 alkane groups, -H, phenyl group, polar groups.

[0016] Further, the bipyridine has the following structure:

[0017]

[0018] Among them, R6 and R7 are any one or more of C1 - C18 alkane groups, C0 - C15 hydrocarbon groups containing at least one of O, N, S.

[0019] In a preferred embodiment, the organic compound having at least one N heterocycle is bipyridine.

[0020] Further, the bipyridine includes, but is not limited to, 1,1 - bis(4 - carboxy - benzylidene) - 4,4'-bipyridine dichloride Ethyl viologen dibromide 1,1 - bis(3,4 - dicarboxy - benzylidene) - 4,4 - bipyridine dibromide 1,1'-bis(2,4 - dinitrophenyl) - 4,4'-dichlorobipyridine at least one of.

[0021] Preferably, the bipyridines are selected from any one of 1,1-bis(4-carboxy-benzylidene)-4,4'-bipyridine dichloride, ethyl viologen dibromide, 1,1-bis(3,4-dicarboxy-benzylidene)-4,4'-bipyridine dibromide, and 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridine dichloride.

[0022] Furthermore, the concentration of the organic compound having at least one N heterocycle in the copper plating solution is 0.003 - 0.1 g / L; preferably 0.003 - 0.05 g / L.

[0023] This application discovers that: when the organic compound having at least one N heterocycle is 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridine dichloride and its concentration in the copper plating solution is 0.005 - 0.02 g / L, the electroplating solution system has the best stability, the porosity of the copper plating layer surface is low, and the copper plating layer is more uniform. The applicant analyzes the reason as follows: the N group in the pyridine substance can form a coordination complex with the copper ions in the copper plating solution. When carboxyl and phenyl groups are grafted outside the pyridine group, the generated Π electron conjugation effect enhances its coordination with copper ions, and the stability coefficient of the complex is higher. This coordination effect enables the copper ions to be well dispersed in the system and further affects the growth process of copper grains, making the particles of the copper plating layer change from conical to spherical, and the plating layer is more uniform and dense; however, when this coordination effect is too strong or the addition amount of 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridine dichloride is too much, the fixing effect on copper ions in the plating solution is too strong, which will instead passivate the electrochemical deposition of copper ions on the surface, resulting in a decrease in the electroplating rate.

[0024] Furthermore, the complexing agent includes but is not limited to one or a combination of more of citric acid, sodium potassium tartrate, sodium salicylate, sodium ethylenediaminetetraacetate, iminodiacetic acid and its alkali metal salts, gluconic acid, gluconates, triethanolamine, tetrapropylhydroxyethylenediamine, modified ethylenediaminetetraacetic acid, phenylethylenediaminetetraacetic acid, and S,S-ethylenediaminedisuccinic acid.

[0025] Furthermore, the complexing agent is selected from at least one of sodium potassium tartrate, sodium salicylate, sodium ethylenediaminetetraacetate, tetrapropylhydroxyethylenediamine, and phenylethylenediaminetetraacetic acid.

[0026] In a preferred embodiment, the complexing agent is sodium potassium tartrate and sodium ethylenediaminetetraacetate.

[0027] Furthermore, the mass ratio of sodium potassium tartrate to sodium ethylenediaminetetraacetate is (2 - 8):1; preferably (3 - 6):1.

[0028] Furthermore, the concentration of the complexing agent in the copper plating solution is 15 - 35 g / L, preferably 20 - 30 g / L.

[0029] Further, the accelerator is selected from any one or a combination of several of sulfonates, carboxylates, thiazoles, thiophenes, diamines or polyamines, and potassium ferrocyanide.

[0030] Further, the sulfonates include, but are not limited to, any one of C2-C15 alkylbenzene sulfonates, alkyl diphenyl ether disulfonic acids, acylmethane alkanesulfonates, p-toluenesulfonates, and mercaptoalkyl sulfonates.

[0031] Further, the carboxylates include, but are not limited to, at least one of 4-pyrimidinecarboxylic acid and its salts, and 5-chloropyrimidine-4-carboxylate.

[0032] Further, the thiazoles include, but are not limited to, at least one of 2-mercaptobenzothiazole and its salts, 2-thiolbenzothiazole and its salts, and 2,2'-dithiobisbenzothiazole and its salts.

[0033] Further, the thiophenes include, but are not limited to, at least one of C1-12 alkyl thiophenes and their salts, thiophene dicarboxylates, and benzodithiophenes and their salts.

[0034] Further, the diamines or polyamines include, but are not limited to, at least one of tetrahydroxypropyl ethylenediamine and triethanolamine.

[0035] Preferably, the accelerator is a combination of diamines or polyamines and potassium ferrocyanide, and more preferably a combination of tetrahydroxypropyl ethylenediamine and potassium ferrocyanide.

[0036] Further, the mass ratio of tetrahydroxypropyl ethylenediamine to potassium ferrocyanide in the accelerator is (1-5):2; preferably (1.5-4.5):2.

[0037] Further, the concentration of the accelerator in the copper plating solution is 0.04-0.5 g / L, preferably 0.08-0.3 g / L.

[0038] Further, the reducing agent includes, but is not limited to, one or a combination of several of formaldehyde, formaldehyde precursors, formaldehyde derivatives, glyoxylic acid, glyoxylic acid derivatives, borohydrides, borohydride substitutes, boranes, dimethylamine borane (DMAB), hypophosphorous acid, and glycolic acid.

[0039] Preferably, the reducing agent is formaldehyde.

[0040] In some embodiments, the concentration of the reducing agent in the copper plating solution is 2-9 g / L, preferably 2-5 g / L.

[0041] Further, the surfactant is selected from one or more of polyvinylpyrrolidone, polyethylene glycol, cetyl alcohol polyoxypropylene polyoxyethylene ether, nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, and nonionic polyacrylamide.

[0042] Further, the polyethylene glycol includes but is not limited to PEG500, PEG600, PEG800, PEG1000, PEG1200, PEG1500, PEG2000; preferably any one or a combination of several of PEG1000, PEG1200, and PEG1500.

[0043] Further, the number average molecular weight of the polyvinylpyrrolidone is 5000 - 150000; preferably 8000 - 130000;

[0044] It was unexpectedly found in this application that when the surfactant is polyvinylpyrrolidone and its number average molecular weight is further limited to 10000 - 50000, the copper plating speed and copper plating quality can be further improved. The applicant speculates that the reason is as follows: Polyvinylpyrrolidone has a large number of polar groups on its surface and has a long molecular chain. The cross-linked structure formed by the molecular chain in the system can disperse and coat copper ions and copper grains, significantly refining the grain size and improving the grain uniformity. However, its special structure will have hydrogen bond interactions and molecular chain entanglements with complexing agents such as potassium sodium tartrate and tetrasodium ethylenediaminetetraacetate, stabilizers, and accelerators in the system, affecting the dispersion of copper ions and grains. When the number average molecular weight of polyvinylpyrrolidone is too large, the internal cross-linking effect is too strong, which will not only directly affect the coordination and complexation of stabilizers and complexing agents with copper ions, but also significantly slow down the deposition rate of copper ions. When the number average molecular weight of polyvinylpyrrolidone is too small, the dispersion effect on copper ions and grains is low, and the compactness and uniformity of the grains will decrease.

[0045] Further, the concentration of the surfactant in the copper plating solution is 0.0005 - 0.01 g / L.

[0046] Further, the pH regulator includes but is not limited to at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate, and sodium borohydride.

[0047] Further, the working temperature of the copper plating solution is 30 - 35 °C, preferably 33 - 35 °C; the pH of the copper plating solution is 11 - 13, preferably 12 - 13.

[0048] Secondly, the present application also provides a method for preparing the copper plating solution: mixing a complexing agent, a pH regulator and water, denoted as solution A; sequentially mixing a copper source, a nickel source and a reducing agent, denoted as solution B; sequentially adding a surfactant, an accelerator, and an organic compound having at least one N heterocycle into water and mixing, denoted as solution C; finally, sequentially mixing solutions A, B, and C in sequence and adjusting the pH of the copper plating solution.

[0049] Furthermore, the present invention does not strictly limit the copper plating substrate for the copper plating solution, and materials with different Tg values can be selected for copper plating. The substrate includes but is not limited to high Tg (S1000-2M) and medium Tg (S1000) type plates of Guangdong Shengyi Technology Co., Ltd.; high Tg (halogen-free IT-958G) and medium Tg (halogen-free IT150G) type plates of Unimicron Technology Corporation; any one of high Tg (lead-free NY7350ANT) and PTFE high-frequency materials (NYHP-255D) of Nan Ya New Materials Technology Co., Ltd.

[0050] Furthermore, the copper plating method of the copper plating solution includes the following steps:

[0051] S1. Treat the substrate, including the steps of swelling-degreasing-pre-neutralization-neutralization-hole conditioning-activation-activation-reduction;

[0052] S2. Place the treated substrate in a copper plating solution at 30-35 °C with a pH of 11-13 for copper deposition process.

[0053] Furthermore, in step S2, the temperature is preferably 32-35 °C, and the pH is preferably 12-13.

[0054] Beneficial effects

[0055] 1. Through the synergistic effect of each component, the copper plating solution of the present application can form a complex with copper ions and complex with reaction by-products, making the copper solution have excellent stability, capable of preparing a copper coating with high thickness and high plating speed, significantly improving the plating speed, and the copper coating has excellent performance;

[0056] 2. By optimizing the component ratio and dosage of the complexing agent, stabilizer and accelerator, the electroplating solution of the present application can match substrates of different materials, has a wide range of substrate applicability, excellent adhesion, and a high reliable yield of the coating;

[0057] 3. The copper plating solution of the present application has high copper plating activity, and can carry out a copper plating process with high thickness, high speed, high quality and high efficiency at an environment of 30-35 °C. Compared with the traditional process, it effectively saves heat energy consumption, reduces the usage amount of raw materials with high cost, and effectively reduces the process cost. Description of the Drawings

[0058] Figures 1 - 10 : Backlight images of the copper plating layers of the copper plating solutions of Examples 1-6 and Comparative Examples 1-6 on the S1000-2M model substrate, respectively;

[0059] Figures 11 - 20 : Backlight images of the copper plating layers of the copper plating solutions of Examples 1-6 and Comparative Examples 1-6 on the IT-150G model substrate, respectively;

[0060] Figures 21 - 30 : Backlight images of the copper plating layers of the copper plating solutions of Examples 1-6 and Comparative Examples 1-6 on the NYHP-225D model substrate, respectively. Detailed implementation manners

[0061] Examples

[0062] Example 1

[0063] This example provides an efficient complexing electroless copper plating solution, and the components of the copper plating solution are: copper sulfate 8 g / L, nickel sulfate 0.3 g / L, 1,1'-bis(2,4-dinitrophenyl)-4,4'-dichlorobipyridine 0.01 g / L, potassium sodium tartrate 20 g / L, tetrasodium ethylenediaminetetraacetate 5 g / L, potassium ferrocyanide 0.04 g / L, tetrahydroxypropyl ethylenediamine 0.06 g / L, 37 wt% formaldehyde solution 11 mL / L, polyvinylpyrrolidone (number-average molecular weight is 20,000) 0.001 g / L, sodium hydroxide 13 g / L, water;

[0064] The preparation method of the copper plating solution is:

[0065] Add the corresponding amounts of potassium sodium tartrate, tetrasodium ethylenediaminetetraacetate, and sodium hydroxide into a beaker in sequence, and add 500 mL of distilled water for dissolution, denoted as Solution A; take another beaker and add the corresponding amounts of copper sulfate pentahydrate and nickel sulfate hexahydrate in sequence, add 50 mL of distilled water for dissolution and mixing, and then add 11 mL of 37 wt% formaldehyde solution, denoted as Solution B; take another beaker and add the corresponding amounts of polyvinylpyrrolidone, potassium ferrocyanide, tetrahydroxypropyl ethylenediamine, and 1,1'-bis(2,4-dinitrophenyl)-4,4'-dichlorobipyridine in sequence, and add 200 mL of distilled water for dissolution, denoted as Solution C. Mix Solution A, Solution B, and Solution C in sequence, make up the volume to 1 L with distilled water, and adjust the pH of the copper plating solution to 13 with a pH meter.

[0066] Example 2

[0067] This example is the same as Example 1, the difference is that: the 1,1'-bis(2,4-dinitrophenyl)-4,4'-dichlorobipyridine is 0.005 g / L.

[0068] Example 3

[0069] This example is the same as Example 1, except that the amount of 1,1'-bis(2,4-dinitrophenyl)-4,4'-dichlorobipyridine is 0.015 g / L.

[0070] Example 4

[0071] This example is the same as Example 1, except that the amount of 1,1'-bis(2,4-dinitrophenyl)-4,4'-dichlorobipyridine is 0.02 g / L.

[0072] Example 5

[0073] This example is the same as Example 1, except that the amount of tetrapropyleneglycol ethylenediamine is 0.03 g / L.

[0074] Example 6

[0075] This example is the same as Example 1, except that the amount of tetrapropyleneglycol ethylenediamine is 0.09 g / L.

[0076] Comparative Example 1

[0077] It is basically the same as Example 1, except that sodium ethylenediaminetetraacetate is not added.

[0078] Comparative Example 2

[0079] It is basically the same as Example 1, except that nickel sulfate hexahydrate is not added.

[0080] Comparative Example 3

[0081] It is basically the same as Example 1, except that 1,1'-bis(2,4-dinitrophenyl)-4,4'-dichlorobipyridine is replaced with 2,2'-bipyridine;

[0082] The preparation method of the copper plating solution is as follows:

[0083] Add the corresponding amounts of potassium sodium tartrate, sodium ethylenediaminetetraacetate, and sodium hydroxide into a beaker, and add 500 mL of distilled water to dissolve, denoted as Solution A; take another beaker and add the corresponding amounts of copper sulfate pentahydrate and 50 mL of distilled water to dissolve and mix, then dissolve nickel sulfate hexahydrate with 50 mL of distilled water, mix the two, and then add 11 mL of 37 wt% formaldehyde solution, denoted as Solution B; take another beaker and add the corresponding amounts of polyvinylpyrrolidone, potassium ferrocyanide, and tetrapropyleneglycol ethylenediamine and add 200 mL of distilled water to dissolve. Take another beaker and add 1 mL of methanol, 2,2'-bipyridine, and 10 mL of distilled water to dissolve, and mix the two to obtain Solution C. Mix Solution A, Solution B, and Solution C in sequence, and make up to 1 L with distilled water, and adjust the pH of the copper plating solution to 13 with a pH meter.

[0084] Comparative Example 4

[0085] It is basically the same as Example 1, except that: the 1,1'-bis(2,4-dinitrophenyl)-4,4'-dichlorobipyridine is replaced by 2-mercaptobenzothiazole;

[0086] The preparation method of the copper plating solution is as follows:

[0087] Add corresponding amounts of potassium sodium tartrate, tetrasodium ethylenediaminetetraacetate, and sodium hydroxide into a beaker in sequence, and add 500 mL of distilled water to dissolve, denoted as Solution A; take another beaker and add corresponding amounts of copper sulfate pentahydrate and 50 mL of distilled water to dissolve and mix, then dissolve nickel sulfate hexahydrate with 50 mL of distilled water, mix the two, and then add 11 mL of 37 wt% formaldehyde solution, denoted as Solution B; take another beaker and add corresponding amounts of polyvinylpyrrolidone, potassium ferrocyanide, and tetrapropylhydroxyethylenediamine in sequence, and add 200 mL of distilled water to dissolve; take another beaker and add 1 mL of 32 wt% NaOH and 2-mercaptobenzothiazole and dissolve with 10 mL of distilled water; after mixing the two, it is denoted as Solution C. Mix Solution A, Solution B, and Solution C in sequence, make up the volume to 1 L with distilled water, and adjust the copper plating solution to 13 with a pH meter.

[0088] Comparative Example 5

[0089] It is basically the same as Example 1, except that: the 1,1'-bis(2,4-dinitrophenyl)-4,4'-dichlorobipyridine is replaced by ethyl viologen dibromide.

[0090] Comparative Example 6

[0091] It is basically the same as Example 1, except that: the number-average molecular weight of the polyvinylpyrrolidone is 60,000.

[0092] Performance test method:

[0093] 1. Pretreatment and electroless copper plating process:

[0094] The electroless copper plating solutions described in the examples are all used to conduct copper plating tests on three different types of substrates, namely high Tg (S1000-2M), medium Tg (halogen-free IT150G), and PTFE high-frequency material (NYHP-225D). The treatment process of the substrate is as follows:

[0095] (1) The substrate is swollen with a swelling agent (amide substance, SCC-A01H, Guangdong Shuocheng Technology Co., Ltd.) at 80 °C for 6 min; then at room temperature, the substrate is rinsed with tap water for 1 min and rinsed with distilled water for 1 min

[0096] (2) Use a degumming agent (SCC-A02, Guangdong Shuocheng Technology Co., Ltd.) to perform degumming treatment at 80 °C for 12 min. The degumming system is a sodium permanganate system, aiming to oxidize and dissolve the gum residue to produce roughness on the dielectric surface. Then, rinse the substrate with tap water for 1 min and distilled water for 1 min at room temperature;

[0097] (3) Use an H2SO4 and H2O2 system to perform ultrasonic treatment for 2 min at room temperature, aiming to remove the residual liquid after degumming residue adhered to the substrate. Then, rinse the substrate with tap water for 1 min and distilled water for 1 min at room temperature;

[0098] (4) Use an organic neutralizer (SCC-A03H, Guangdong Shuocheng Technology Co., Ltd.) to perform neutralization treatment at 50 °C for 40 s. Then, rinse the substrate with tap water for 1 min and distilled water for 1 min at room temperature;

[0099] (5) Use an adjuster (SCC-A04H3, Guangdong Shuocheng Technology Co., Ltd.) to perform adjustment treatment at 50 °C for 1 min, aiming to clean the copper surface and further adjust the glass fiber filaments in the holes. Then, rinse the substrate with tap water for 1 min and distilled water for 1 min at room temperature;

[0100] (6) Treat in a mixed solution of 80 g / L sodium persulfate and 8 wt% sulfuric acid (the volume ratio of the two is 1:1) at room temperature for 1 min;

[0101] (7) Use a pre-impregnating agent (SCC-A05LP, Guangdong Shuocheng Technology Co., Ltd.) to treat at 45 °C for 20 s and an activating solution (SCC-A06H, Guangdong Shuocheng Technology Co., Ltd.) to treat at 45 °C for 45 s respectively, aiming to attach metal activators to the substrate surface and hole walls to enhance activity. Then, rinse the substrate with tap water for 1 min and distilled water for 1 min at room temperature

[0102] (8) Use a reducing agent (SCC-A07H, Guangdong Shuocheng Technology Co., Ltd.) to treat at 35 °C for 35 s, aiming to reduce palladium ions to palladium atoms, which play a catalytic role in the copper plating process;

[0103] (9) Use the electroless copper plating solutions in Examples 1-10 to perform electroless copper plating at 33 °C for 15 min respectively.

[0104] 2. Evaluation of the copper deposition rate performance:

[0105] After completing the electroless copper plating process, calculate the copper deposition rate of the substrate. The calculation formula is as follows:

[0106]

[0107] v is the thickness of electroless copper deposit, in μm; M1 and M2 are the masses before and after electroless copper deposition respectively, in g; ρ is the density of copper, 8.9 g / cm 3 ; S is the surface area of the board, in cm 2 .

[0108] 3. Performance evaluation of backlight level:

[0109] Multiple 1-mm thick side slices are selected from the hole walls cut from each board, and the slices of each substrate are observed under a metallurgical optical microscope at a magnification of 50X. The quality of the deposited copper film is determined by light measurement under the microscope, and the thickness of the copper film covering the through-hole walls is measured using the European backlight grading scale. The backlight value shows the influence of the reducing composition of the present invention on the backlight.

[0110] The criteria for backlight level discrimination are as follows: Grade 1: Translucent, with the translucent area greater than 90%; Grade 2: Translucent, 80% < translucent area ≤ 90%; Grade 3: Translucent, 70% < translucent area ≤ 80%; Grade 4: Translucent, 60% < translucent area ≤ 70%; Grade 5: Translucent, 50% < translucent area ≤ 60%; Grade 6: Dim light, 40% < visible light area ≤ 50%, fibrous and clear; Grade 7: Dim light, 30% < visible light area ≤ 40%, dim light in fibrous form; Grade 8: Dim light, 20% < visible light area ≤ 30%, partial dim light initially in fibrous form; Grade 8.5: Dim light, 10% < visible light area ≤ 20%, starting to see < 10 scattered dim light points; Grade 9: Dim light, 5% < visible light area ≤ 10%, starting to see < 5 scattered dim light points; Grade 9.5: Dim light, 1% < visible light area ≤ 5%, starting to see < 2 scattered dim light points; Grade 10: Completely black.

[0111] 4. Evaluation of the stability of electroless copper plating solution

[0112] The electroless copper plating solutions obtained from the examples are respectively placed in beakers, and 20 mL of a palladium chloride solution with a concentration of 0.18 g / L is added to every 100 mL of the electroless copper plating solution for catalytic decomposition reaction, and the start decomposition time is recorded.

[0113] Performance test results:

[0114] The test results are shown in Table 1.

[0115] Table 1

[0116]

[0117] Table 2

[0118]

[0119] Table 3

[0120]

Claims

1. An efficient complexing electroless copper plating solution, characterized in that, The components of the copper plating solution include: a copper source, a nickel source, an organic compound having at least one N heterocycle, a complexing agent, an accelerator, a reducing agent, a surfactant, and a pH regulator; The organic compound having at least one N heterocycle is a bipyridine type; The bipyridine type has the following structure: Wherein, the R6 and R7 are any one or more of an alkyl group with 1 to 18 carbon atoms, a hydrocarbon group with 0 to 15 carbon atoms containing at least one of O, N, and S; The bipyridine type is selected from any one of 1,1-bis(4-carboxy-benzylidene)-4,4'-bipyridine dichloride, ethyl viologen dibromide, 1,1-bis(3,4-dicarboxy-benzylidene)-4,4-bipyridine dibromide, 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridine dichloride; The surfactant is polyvinylpyrrolidone with a number average molecular weight of 10,000 - 50,000.

2. The electroless copper plating solution according to claim 1, wherein The concentration of the organic compound having at least one N heterocycle in the copper plating solution is 0.003 - 0.1 g / L.

3. The electroless copper plating solution according to claim 1, wherein The complexing agent is selected from at least one of sodium potassium tartrate, sodium salicylate, sodium ethylenediaminetetraacetate, tetrahydroxypropyl ethylenediamine, and phenyl ethylenediaminetetraacetic acid, and the concentration of the complexing agent in the copper plating solution is 15 - 35 g / L.

4. The electroless copper plating solution according to claim 1, wherein The accelerator is selected from any one or a combination of several of sulfonates, carboxylates, thiazoles, thiophenes, diamines or polyamines, and potassium ferrocyanide, and the concentration of the accelerator in the copper plating solution is 0.04 - 0.5 g / L.

5. The electroless copper plating solution according to claim 1, wherein, The working temperature of the copper plating solution is 30 - 35 °C.

6. The preparation method of the electroless copper plating solution according to any one of claims 1-5, characterized in that, The preparation method is as follows: Mix the complexing agent, pH regulator and water, denoted as solution A; successively mix the copper source, nickel source and reducing agent, denoted as solution B; successively add the surfactant, accelerator, and organic compound having at least one N heterocycle to water and mix, denoted as solution C; finally, successively mix solution A, solution B, and solution C in sequence and adjust the pH of the copper plating solution.

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