Palladium-free instantaneous plating starting method for chemically plating cobalt on surface of red copper
Through the palladium-free instantaneous plating method, including immersion-plating sealing layer, replacement catalytic layer, activation and electroless cobalt plating instantaneous plating steps, the problems of slow plating and leakage plating on copper surface are solved, and the effects of instantaneous plating and cost reduction are achieved.
Patent Information
- Application Number
- CN202510127017.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-28
- Publication Date
- 2025-04-18
AI Technical Summary
When electroless cobalt plating is used for copper electroless copper surface, the plating speed is slow and there is leakage plating.
A palladium-free instantaneous plating method is adopted, including dip-plating the sealing layer, displacing the catalytic layer, and activating and electroless cobalt plating instantaneous plating steps. The composition and treatment conditions of the blocking liquid and the catalytic liquid can effectively avoid the use of noble metal palladium, and instantaneous plating of cobalt is achieved by activating the liquid.
The instantaneous plating of electroless cobalt plating on copper surface is achieved, which avoids the occurrence of leakage plating and significantly reduces production costs, while ensuring the effect of electroless plating.
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Abstract
Description
Technical Field
[0001] The invention belongs to the field of surface modification of copper and relates to a palladium-free instantaneous plating method for chemically plating cobalt on the surface of copper. Background Art
[0002] The information disclosed in this background technology section is only intended to increase some understanding of the overall background of the invention, and should not be necessarily regarded as an admission or any form of suggestion that the information constitutes the prior art already known to ordinary technicians in this field.
[0003] Cobalt is a metal of the eighth subgroup, which has strong affinity for oxygen. A dense oxide film can be quickly formed on the metal surface, which makes the metal cobalt have excellent corrosion resistance and high-temperature oxidation resistance. In addition, cobalt has excellent catalytic properties of the eighth subgroup metal. For example, in the electrocatalysis of hydrogen and oxygen, cobalt can be used as a catalyst to replace the eighth subgroup platinum, palladium and other precious metals. Not only that, in the field of electronics, since nano-sized metal copper encounters bottlenecks in conductivity, metal cobalt is used to replace metal copper to achieve interconnection. In view of the excellent properties of cobalt in many aspects, chemical cobalt plating is used in many fields. Chemical cobalt plating on the surface of copper can improve the corrosion resistance, catalysis and small-size conductivity of the original surface.
[0004] Chemical cobalt plating can usually use sodium hypophosphite and aminoborane as reducing agents, but since aminoborane is expensive and sodium hypophosphite has higher cost performance and stability, chemical cobalt plating with sodium hypophosphite as reducing agent is more widely used. Since the catalytic oxidation of sodium hypophosphite by cobalt can only be carried out in alkaline solution, unlike chemical nickel plating, chemical cobalt plating usually uses alkaline medium. Since copper has no activity in the catalytic oxidation of sodium hypophosphite, chemical cobalt plating on the surface of copper cannot be directly initiated, and usually activates with the help of precious metal palladium to start chemical cobalt plating. With the continuous upgrading and iteration of the industry, the activation method of chemical cobalt plating needs to be free of precious metals to reduce costs and increase efficiency. This not only requires the use of low-cost metals instead of metal palladium in the activation process, but also cannot use high-priced and low-stability reducing agents such as aminoborane. At the same time, the activation process needs to be able to instantly initiate chemical cobalt plating to prevent leakage plating. Summary of the invention
[0005] In view of the shortcomings of the prior art, the present invention aims to solve the problem of slow plating speed of a palladium-free activation method when chemically plating cobalt on the copper surface, and to provide an instantaneous plating method before chemically plating cobalt on the copper surface.
[0006] The technical solution adopted by the present invention is as follows:
[0007] The present invention provides a palladium-free instantaneous plating method for chemically plating cobalt on the surface of copper, the method comprising the following steps:
[0008] (1) Immersion plating sealing layer: The temperature of the sealing solution is kept at 35-50 °C, and the copper after surface pretreatment is immersed in the sealing solution for 10-20 seconds and then cleaned with water to complete the immersion plating sealing layer; wherein the sealing solution is a mixed solution composed of borax, a composite ligand, cobalt sulfate heptahydrate, thiourea and water, and the pH of the sealing solution is 5.0-6.0;
[0009] (2) replacing the catalyst layer: keeping the temperature of the catalyst liquid constant at 45-60°C, preheating the copper treated in step (1) in water at the same temperature as the catalyst liquid, immersing the copper in the catalyst liquid for 5-10 seconds, and then washing the copper with water to complete the replacement of the catalyst layer; wherein the catalyst liquid is a mixed solution consisting of hydrochloric acid, nickel chloride hexahydrate, hydroquinone, thiourea, bismuth chloride, cuprous chloride and water;
[0010] (3) Activation and chemical cobalt instantaneous plating: The temperature of the activation solution is kept constant at 60-80°C, and the copper treated in step (2) is immersed in the activation solution for 5-10 seconds to complete the activation, and then is directly immersed in the chemical cobalt plating solution without water washing to perform chemical plating, thereby completing palladium-free instantaneous plating; wherein the activation solution contains equal amounts of sodium hydroxide and sodium hypophosphite.
[0011] In the present invention, the copper surface pretreatment is an existing conventional technology, and the main steps include degreasing, cleaning, polishing and passivation, which will not be repeated here.
[0012] In one or more embodiments of the present invention, in step (1), each 1 L of the blocking solution contains 15-18 g of borax, 25-35 g of a composite ligand, 25-30 g of cobalt sulfate heptahydrate, and 120-130 g of thiourea.
[0013] Wherein, the composite ligand is a combination of any two of ammonium chloride, ethylenediamine, potassium sodium tartrate or trisodium citrate. Preferably, the composite ligand is a combination of potassium sodium tartrate and trisodium citrate.
[0014] The composite ligand can regulate the deposition of cobalt ions. If the composite ligand is too much or too strong, the cobalt ions are difficult to be reduced, and it is impossible to replace a layer of cobalt sealing layer. If the composite ligand is too little or too weak, the solution is unstable.
[0015] In one or more embodiments of the present invention, in step (2), the copper treated in step (1) is preheated in water at the same temperature as the catalyst solution for 1 to 3 minutes; preferably, the preheating time is 2 minutes.
[0016] In step (2), each 1 L of the catalyst solution contains 1.5-2.5 mol of hydrochloric acid, 30-50 g of nickel chloride hexahydrate, 2-5 g of hydroquinone, 140-160 g of thiourea, 30-50 mg of bismuth chloride and 20-30 g of cuprous chloride.
[0017] In one or more embodiments of the present invention, in step (3), the chemical cobalt plating solution uses sodium hypophosphite as a reducing agent, and the solution pH is 8.5-9.5.
[0018] In step (3), the amount of sodium hydroxide and sodium hypophosphite in each 1 L of activation solution is 0.8~2.3 mol.
[0019] In the process of step (1), the present invention can replace a very thin layer of cobalt sealing layer on the copper surface in a short time, so that most of the copper surface is covered by the sealing layer, thereby preventing the copper from being over-corroded during the subsequent step (2). However, since the replacement process cannot completely cover the substrate, there are still active sites on the copper surface that are not covered by the sealing layer during step (2). In the process of replacing the catalytic layer, the copper surface that is not covered by the sealing layer obtained in step (1) will replace the nickel ions in the catalytic solution, thereby forming the "seed" of the activation process. The high concentration of hydrogen ions in the catalytic solution can fully activate the copper that is not covered by the sealing layer, and often the higher the hydrogen ion concentration, the higher the catalytic activity of the catalytic layer, but too high a hydrogen ion concentration may cause excessive corrosion of the copper and a large amount of hydrogen precipitation. The cuprous chloride in the catalytic solution can make the copper surface present an active state and can avoid excessive corrosion of the copper; the bismuth chloride in the catalytic solution can inhibit the precipitation of hydrogen, ensuring that the catalytic layer has good binding force. During the treatment process of immersing the activation solution in step (3), the catalyst layer can induce the sodium hypophosphite to decompose violently, and the large amount of hydrogen precipitated can ensure that the nickel in the catalyst layer is in a highly active reduced state, which has an excellent chemical cobalt plating start effect. The activation solution contains equal amounts of sodium hydroxide and sodium hypophosphite to ensure the activation effect of the activation solution. If the ratio of the amount of sodium hydroxide to sodium hypophosphite is not 1, the subsequent chemical cobalt plating cannot be instantaneously started. If the activation is followed by water washing, the oxidation of nickel during the water washing process will be caused, thereby reducing the catalytic activity of the catalyst layer, resulting in a delay in the subsequent chemical cobalt plating start time, and the longer the water washing time, the longer the chemical cobalt plating start time. Therefore, step (3) is directly immersed in the chemical cobalt plating solution after activation to ensure the instantaneous plating effect. When directly entering the chemical cobalt plating solution after activation, since the chemical cobalt plating solution uses sodium hypophosphite as a reducing agent, and the plating solution itself has a certain buffering capacity, it will not cause adverse effects on the chemical cobalt plating solution.
[0020] Compared with the related art known to the inventor, one of the technical solutions of the present invention has the following beneficial effects:
[0021] The present invention discloses a palladium-free instant plating method for chemically plating cobalt on copper surface, which can avoid the use of precious metal palladium in the activation process before chemically plating cobalt on copper surface, and achieve instant plating of chemically plating cobalt on copper surface, thereby effectively avoiding the leakage plating phenomenon of individual sites of subsequent chemically plating cobalt. In addition, the solution used in the present invention is very stable, which can not only significantly reduce the production cost, but also ensure the effect of chemical plating. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.
[0023] Figure 1 This is the element distribution diagram after immersion plating of the sealing layer in Example 1;
[0024] Figure 2 This is the element distribution diagram after the catalyst layer is replaced in Example 1;
[0025] Figure 3 The potential change after Example 1 is activated and immersed in chemical cobalt plating solution. DETAILED DESCRIPTION
[0026] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.
[0027] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.
[0028] In a typical embodiment of the present invention, a palladium-free instantaneous plating method for chemically plating cobalt on a copper surface is provided, which is carried out in the following steps:
[0029] (1) Immersion plating sealing layer: The temperature of the constant sealing solution is 35-50 °C, and the copper after surface pretreatment is immersed in the sealing solution for 10-20 seconds and then cleaned with deionized water to complete the immersion plating sealing layer; wherein each 1L of the sealing solution contains 15-18 g of borax, 25-35 g of a composite ligand, 25-30 g of cobalt sulfate heptahydrate and 120-130 g of thiourea, and the pH of the sealing solution is 5.0-6.0; the composite ligand is a combination of any two of ammonium chloride, ethylenediamine, potassium sodium tartrate or trisodium citrate;
[0030] (2) replacing the catalyst layer: keeping the temperature of the catalyst liquid constant at 45-60°C, preheating the copper treated in step (1) in deionized water at the same temperature as the catalyst liquid for 2 min, immersing it in the catalyst liquid for 5-10 s, and then washing it with deionized water to complete the replacement of the catalyst layer; wherein each 1 L of the catalyst liquid contains 1.5-2.5 mol of hydrochloric acid, 30-50 g of nickel chloride hexahydrate, 2-5 g of hydroquinone, 140-160 g of thiourea, 30-50 mg of bismuth chloride and 20-30 g of cuprous chloride;
[0031] (3) Activation and chemical cobalt instantaneous plating: the temperature of the activation solution is kept constant at 60-80°C, the copper treated in step (2) is immersed in the activation solution for 5-10 seconds to complete activation, and then is directly immersed in a chemical cobalt plating solution for chemical plating without water washing, wherein the chemical cobalt plating solution uses sodium hypophosphite as a reducing agent, the solution pH is 8.5-9.5, and palladium-free instantaneous plating is completed; wherein the activation solution contains equal amounts of sodium hydroxide and sodium hypophosphite, and the amounts of sodium hydroxide and sodium hypophosphite in each 1 L of the activation solution are both 0.8-2.3 mol.
[0032] The composite ligand described in step (1) is a combination of any two of ammonium chloride, ethylenediamine, potassium sodium tartrate or trisodium citrate; the chemical cobalt plating solution described in step (3) uses sodium hypophosphite as a reducing agent, and the solution pH is 8.5-9.5.
[0033] In this embodiment, a very thin layer of cobalt sealing layer is replaced on the surface of the copper in a short time during the treatment process of step (1), thereby preventing the copper from being over-corroded during the subsequent step (2). After replacing the sealing layer, there are still active sites on the copper surface that are not covered by the sealing layer. In the process of replacing the catalytic layer in step (2), the nickel ions in the catalytic solution are replaced, thereby forming the "seed" of the activation process, that is, the catalytic layer. In the process of immersing in the activation solution in step (3), the catalytic layer can induce the violent decomposition of sodium hypophosphite, and the large amount of hydrogen precipitated can ensure that the nickel in the catalytic layer is in a reduced state, thereby having an excellent chemical cobalt plating start-up effect. Directly immersing in the chemical cobalt plating solution after activation in step (3) can prevent the activation effect from being degraded due to oxidation of nickel in the catalytic layer, thereby ensuring an instantaneous plating start-up effect. When directly entering the chemical cobalt plating solution after activation, since the chemical cobalt plating solution uses sodium hypophosphite as a reducing agent and the plating solution itself has a certain buffering capacity, it will not cause adverse effects on the chemical cobalt plating solution. This embodiment can avoid the use of precious metal palladium in the activation process before chemical cobalt plating on the copper surface, and at the same time achieve instantaneous initiation of chemical cobalt plating on the copper surface, which can not only significantly reduce production costs but also ensure the effect of chemical plating.
[0034] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.
[0035] Embodiment 1: A palladium-free instantaneous plating method for chemically plating cobalt on copper surface of this embodiment is carried out in the following steps:
[0036] (1) Immersion plating sealing layer: The temperature of the sealing solution is kept at 35 °C. The copper after surface pretreatment is immersed in the sealing solution for 20 s and then cleaned with deionized water to complete the immersion plating sealing layer. Each 1 L of the sealing solution contains 15 g of borax, 35 g of a complex ligand (25 g of potassium sodium tartrate and 10 g of trisodium citrate), 30 g of cobalt sulfate heptahydrate and 120 g of thiourea. The pH of the sealing solution is 6.0.
[0037] (2) Replacement of the catalyst layer: The temperature of the catalyst solution is kept constant at 45°C, and the copper treated in step (1) is preheated in deionized water at the same temperature as the catalyst solution for 2 min, then immersed in the catalyst solution for 10 s, and then cleaned with deionized water to complete the replacement of the catalyst layer; wherein each 1 L of the catalyst solution contains 2.5 mol of hydrochloric acid, 50 g of nickel chloride hexahydrate, 2 g of hydroquinone, 140 g of thiourea, 50 mg of bismuth chloride and 20 g of cuprous chloride;
[0038] (3) Activation and instantaneous start of chemical cobalt plating: The temperature of the activation solution is kept constant at 80°C, and the copper treated in step (2) is immersed in the activation solution for 5 seconds to complete activation, and then is directly immersed in an chemical cobalt plating solution without water washing for chemical plating, wherein the chemical cobalt plating solution uses sodium hypophosphite as a reducing agent with a concentration of 32 g / L and a solution pH of 8.5-9.5 to complete palladium-free instantaneous start plating; wherein the activation solution contains equal amounts of sodium hydroxide and sodium hypophosphite, and the amounts of sodium hydroxide and sodium hypophosphite in each 1 L of the activation solution are both 0.8 mol.
[0039] pass Figure 1 It can be seen that during the process of immersion plating the sealing layer, a coating containing cobalt and sulfur elements can be formed on the copper surface, thereby better covering the copper surface and preventing the copper from being corroded under the combined action of high-concentration acid and thiourea during the subsequent immersion plating of the catalytic layer. Figure 2 It can be seen that during the immersion plating of the catalyst layer, nickel elements can be deposited on the copper surface, thereby providing active sites for subsequent chemical cobalt plating. After the copper surface replaces the catalyst layer, it is immersed in the activation solution to keep the nickel in the catalyst layer in a reduced state, thus having an excellent chemical cobalt plating effect. Figure 3From the change in potential after immersion in the chemical cobalt plating solution after activation, it can be seen that the catalytic layer has a very high activity, so that the potential can be instantly shifted negatively to the oxidation potential of the hypophosphite to initiate chemical cobalt plating. In contrast, palladium activation requires about 2 s to make the potential reach the potential of chemical cobalt plating, indicating that the palladium-free activation method of this embodiment has a faster chemical cobalt plating start speed than palladium activation when used for chemical cobalt plating on the surface of copper.
[0040] Embodiment 2: A palladium-free instantaneous plating method for chemically plating cobalt on copper surface of this embodiment is carried out in the following steps:
[0041] (1) Immersion plating sealing layer: The temperature of the sealing solution is kept at 50 °C. The copper after surface pretreatment is immersed in the sealing solution for 10 s and then cleaned with deionized water to complete the immersion plating sealing layer. Each liter of the sealing solution contains 18 g of borax, 25 g of a composite ligand (15 g of potassium sodium tartrate and 10 g of trisodium citrate), 25 g of cobalt sulfate heptahydrate and 130 g of thiourea. The pH of the sealing solution is 5.0.
[0042] (2) Replacement of the catalytic layer: The temperature of the catalytic solution is kept constant at 60°C, and the copper treated in step (1) is preheated in deionized water at the same temperature as the catalytic solution for 2 min, then immersed in the catalytic solution for 5 s, and then cleaned with deionized water to complete the replacement of the catalytic layer; wherein each 1 L of the catalytic solution contains 1.5 mol of hydrochloric acid, 30 g of nickel chloride hexahydrate, 5 g of hydroquinone, 160 g of thiourea, 30 mg of bismuth chloride and 30 g of cuprous chloride;
[0043] (3) Activation and instantaneous start of chemical cobalt plating: The temperature of the activation solution is kept constant at 60°C, and the copper treated in step (2) is immersed in the activation solution for 10 seconds to complete activation, and then is directly immersed in an chemical cobalt plating solution without water washing for chemical plating, wherein the chemical cobalt plating solution uses sodium hypophosphite as a reducing agent with a concentration of 32 g / L and a solution pH of 8.5-9.5 to complete palladium-free instantaneous start plating; wherein the activation solution contains equal amounts of sodium hydroxide and sodium hypophosphite, and the amounts of sodium hydroxide and sodium hypophosphite in each 1 L of the activation solution are both 2.3 mol.
[0044] Embodiment 3: A palladium-free instantaneous plating method for chemically plating cobalt on copper surface of this embodiment is carried out in the following steps:
[0045] (1) Immersion plating sealing layer: The temperature of the sealing solution is kept at 45 °C. The copper after surface pretreatment is immersed in the sealing solution for 15 s and then cleaned with deionized water to complete the immersion plating sealing layer. Each 1 L of the sealing solution contains 16 g of borax, 30 g of a complex ligand (18 g of potassium sodium tartrate and 12 g of trisodium citrate), 28 g of cobalt sulfate heptahydrate and 125 g of thiourea. The pH of the sealing solution is 5.5.
[0046] (2) Replacement of the catalytic layer: The temperature of the catalytic solution is kept constant at 50°C, and the copper treated in step (1) is preheated in deionized water at the same temperature as the catalytic solution for 2 min, then immersed in the catalytic solution for 8 s, and then cleaned with deionized water to complete the replacement of the catalytic layer; wherein each 1 L of the catalytic solution contains 2.0 mol of hydrochloric acid, 40 g of nickel chloride hexahydrate, 3 g of hydroquinone, 150 g of thiourea, 35 mg of bismuth chloride and 25 g of cuprous chloride;
[0047] (3) Activation and chemical cobalt instantaneous plating: The temperature of the activation solution is kept at 70°C, and the copper treated in step (2) is immersed in the activation solution for 8 seconds to complete activation, and then is directly immersed in a chemical cobalt plating solution without water washing for chemical plating. The chemical cobalt plating solution uses sodium hypophosphite as a reducing agent with a concentration of 32 g / L and a solution pH of 8.5-9.5 to complete palladium-free instantaneous plating; wherein the activation solution contains equal amounts of sodium hydroxide and sodium hypophosphite, and the amounts of sodium hydroxide and sodium hypophosphite in each 1 L of the activation solution are both 1.5 mol.
[0048] The copper obtained in Examples 1 to 3 after being subjected to sealing layer immersion plating, catalytic layer immersion plating and activation treatment was directly immersed in the chemical cobalt plating solution, and the time when hydrogen bubbles began to precipitate on the surface of the copper after being immersed in the chemical cobalt plating solution was recorded. The results were compared with those of traditional palladium activation, and are shown in Table 1.
[0049] Table 1 The precipitation time of hydrogen bubbles after the copper surface was activated without palladium and immersed in the chemical cobalt plating solution
[0050] first Second time The third time After treatment in Example 1 Instantaneous precipitation Instantaneous precipitation Instantaneous precipitation After treatment in Example 2 Instantaneous precipitation Instantaneous precipitation Instantaneous precipitation After treatment in Example 3 Instantaneous precipitation Instantaneous precipitation Instantaneous precipitation After palladium activation Precipitation after 1 s Precipitation after 2 s Precipitation after 2 s
[0051] It can be seen from Table 1 that the copper of Examples 1 to 3, after being treated with palladium-free activation, will instantly induce the precipitation of hydrogen bubbles when immersed in the chemical cobalt plating solution, indicating that chemical cobalt plating can be instantly induced, which is faster than the initiation speed of chemical cobalt plating after palladium activation treatment. The rapid initiation of chemical cobalt plating on the copper surface can avoid the occurrence of leak plating.
[0052] The sealing liquid, catalytic liquid and activation liquid used in Examples 1 to 3 all have good stability. The solutions do not self-decompose when stored at room temperature or used at high temperature. The chemicals used to prepare the solutions all have high cost-effectiveness, which can effectively control costs compared to palladium activation and other palladium-free activation methods.
[0053] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.
Claims
1. A palladium-free instantaneous plating method for chemically plating cobalt on copper surface, characterized in that: The method comprises the following steps: (1) Immersion plating sealing layer: Keep the temperature of the sealing liquid constant at 35-50 °C, immerse the copper after surface pretreatment in the sealing liquid for 10-20 seconds, and then rinse with water to complete the immersion plating sealing layer; The sealing solution is a mixed solution composed of borax, a composite ligand, cobalt sulfate heptahydrate, thiourea and water, and the pH value of the sealing solution is 5.0-6.0; (2) Replacement of the catalyst layer: The temperature of the catalyst solution is kept constant at 45-60°C, the copper treated in step (1) is preheated in water at the same temperature as the catalyst solution, and then immersed in the catalyst solution for 5-10 seconds, and then cleaned with water to complete the replacement of the catalyst layer; The catalyst liquid is a mixed solution consisting of hydrochloric acid, nickel chloride hexahydrate, hydroquinone, thiourea, bismuth chloride, cuprous chloride and water; (3) Activation and chemical cobalt plating instant start: the temperature of the activation solution is kept constant at 60-80°C, the copper treated in step (2) is immersed in the activation solution for 5-10 seconds to complete the activation, and then it is directly immersed in the chemical cobalt plating solution without water washing to complete the palladium-free instant start plating; The activation solution contains equal amounts of sodium hydroxide and sodium hypophosphite.
2. The palladium-free instantaneous plating method for chemically plating cobalt on copper surface as claimed in claim 1, characterized in that: In step (1), each 1 L of the blocking solution contains 15-18 g of borax, 25-35 g of a complex ligand, 25-30 g of cobalt sulfate heptahydrate and 120-130 g of thiourea.
3. The palladium-free instant plating method for chemically plating cobalt on copper surface as claimed in claim 1 or 2, characterized in that: The composite coordination agent is a combination of any two of ammonium chloride, ethylenediamine, potassium sodium tartrate or trisodium citrate.
4. The palladium-free instantaneous plating method for chemically plating cobalt on copper surface as claimed in claim 3, characterized in that: The composite complexing agent is a combination of potassium sodium tartrate and trisodium citrate.
5. The palladium-free instant plating method for chemically plating cobalt on copper surface as claimed in claim 1, characterized in that: In step (2), the copper treated in step (1) is preheated in water at the same temperature as the catalyst solution for 1 to 3 minutes.
6. The palladium-free instantaneous plating method for chemically plating cobalt on copper surface as claimed in claim 5, characterized in that: The copper treated in step (1) is preheated in water at the same temperature as the catalyst solution for 2 min.
7. The palladium-free instant plating method for chemically plating cobalt on copper surface as claimed in claim 1, characterized in that: In step (2), each 1 L of the catalyst solution contains 1.5-2.5 mol of hydrochloric acid, 30-50 g of nickel chloride hexahydrate, 2-5 g of hydroquinone, 140-160 g of thiourea, 30-50 mg of bismuth chloride and 20-30 g of cuprous chloride.
8. The palladium-free instantaneous plating method for chemically plating cobalt on copper surface as claimed in claim 1, characterized in that: In step (3), the chemical cobalt plating solution uses sodium hypophosphite as a reducing agent, and the solution pH is 8.5-9.
5.
9. The palladium-free instant plating method for chemically plating cobalt on copper surface as claimed in claim 1, characterized in that: In step (3), the amount of sodium hydroxide and sodium hypophosphite in each 1 L of activation solution is 0.8~2.3 mol.