CN107868947B - Activating solution, preparation method thereof and palladium-free activated chemical nickel plating method - Google Patents

Activating solution, preparation method thereof and palladium-free activated chemical nickel plating method Download PDF

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CN107868947B
CN107868947B CN201711180597.2A CN201711180597A CN107868947B CN 107868947 B CN107868947 B CN 107868947B CN 201711180597 A CN201711180597 A CN 201711180597A CN 107868947 B CN107868947 B CN 107868947B
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solution
nickel plating
sodium
concentration
activating solution
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CN107868947A (en
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姚俊合
何湘柱
陈云毅
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Guangdong University of Technology
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Guangdong University of Technology
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/18—Pretreatment of the material to be coated
    • C23C18/1803—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces
    • C23C18/1824—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces by chemical pretreatment
    • C23C18/1827—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces by chemical pretreatment only one step pretreatment
    • C23C18/1831—Use of metal, e.g. activation, sensitisation with noble metals
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/18—Pretreatment of the material to be coated
    • C23C18/1803—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces
    • C23C18/1824—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces by chemical pretreatment
    • C23C18/1827—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces by chemical pretreatment only one step pretreatment
    • C23C18/1834—Use of organic or inorganic compounds other than metals, e.g. activation, sensitisation with polymers
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
    • C23C18/31—Coating with metals
    • C23C18/32—Coating with nickel, cobalt or mixtures thereof with phosphorus or boron

Abstract

The invention provides an activating solution, which comprises the following components: nickel salts, boric acid, boron-containing compounds, ammonium chloride and citric acid compounds; the boron-containing compound comprises one or more of sodium borohydride, monomethylamino borane, dimethylaminoborane and trimethylamino borane; the citric acid compound comprises citric acid or sodium salt of citric acid. Compared with the prior art, the invention adopts the activating solution with specific components, under the comprehensive action of various components, noble metal palladium is not needed to be adopted for activation in the chemical nickel plating process, and meanwhile, the plating layer has good corrosion resistance, the activating solution has high stability, and the problem of high cost caused by the activation of the noble metal palladium in the manufacturing process of the printed circuit board is effectively reduced. The invention also provides a preparation method of the activating solution and a palladium-free activated chemical nickel plating method.

Description

Activating solution, preparation method thereof and palladium-free activated chemical nickel plating method
Technical Field
The invention relates to the technical field of chemical nickel plating, in particular to an activating solution and a preparation method thereof and a palladium-free activated chemical nickel plating method.
Background
Printed Circuit Boards (PCBs) are interconnects that provide electronic component connections through copper circuitry on their insulating substrates, which are a necessary component of today's electronic devices. However, in the process of manufacturing the PCB, since the surface of the copper circuit is easily oxidized, resulting in deterioration of the conductive and soldering properties, the copper circuit must be surface-treated to prevent oxidation thereof. Currently, the industry mainly uses electroless nickel/gold plating technology to prevent oxidation of the copper circuit surface of the PCB and improve soldering performance, and the electroless nickel/gold plating technology has been widely used in the current PCB manufacturing field. Electroless nickel/gold plating is a self-catalytic process that can be performed spontaneously on a catalytically active surface. However, the activation energy required in electroless nickel plating using hypophosphite as a reducing agent is so high that the copper surface cannot catalyze oxidation of hypophosphite, so electroless nickel plating cannot be performed spontaneously, and it is necessary to induce electroless nickel plating to proceed by introducing active sites on the copper circuit surface by means of an activation treatment.
Currently, the most widely used method of activation prior to electroless nickel plating of copper circuit surfaces in PCB manufacturing processes is palladium activation. However, in recent years, the price of noble metal palladium is increasing, which brings about some problems in cost; meanwhile, the activating solution of the method has low stability and is easy to be subjected to percolation plating. If a feasible palladium-free activation method can be developed, a major breakthrough is made to the PCB manufacturing industry, a technical problem of high cost at present can be solved, and the method has great significance to the development of the PCB manufacturing industry.
Today, related workers have begun to explore a viable palladium-free activation process. Tian Dong and the like utilize the difference of stability constants of thiourea, monovalent copper ions and nickel ion complexes to reduce the potential of copper on the surface of a PCB copper circuit, so that nickel is deposited, a nickel replacement process is realized, and nickel can be continuously deposited due to self-catalysis of the nickel, so that a chemical nickel plating process is realized; however, this method causes nickel to be deposited on the surface of the copper circuit and simultaneously causes sulfur to be deposited, and thiourea exists, so that the electroless nickel plating is difficult to carry out if the electroless nickel plating process is incomplete because sulfur-containing substances are toxic agents for electroless nickel plating. The Jianhui Lin and the like firstly utilize hydrogen atoms generated by formaldehyde decomposition to be adsorbed on the surface of copper, and then utilize the catalysis of the hydrogen atoms to carry out electroless nickel plating; however, in this method, hydrogen atoms generated by formaldehyde decomposition are adsorbed on the copper surface, if the copper surface is exposed to air, the maintenance time is extremely short, and if electroless nickel plating is successfully performed, the PCB copper circuit board with hydrogen atoms adsorbed thereon must be rapidly transferred to the electroless nickel plating process, which makes industrial mass production very difficult.
Therefore, research on a palladium-free activated nickel plating method which can smoothly carry out chemical nickel plating and is simple in process and suitable for large-scale production becomes an important point of research in the field.
Disclosure of Invention
In view of the above, the invention aims to provide an activating solution, a preparation method thereof and a palladium-free activated electroless nickel plating method.
The invention provides an activating solution, which comprises the following components: nickel salts, boric acid, boron-containing compounds, ammonium chloride and citric acid compounds;
the boron-containing compound comprises one or more of sodium borohydride, monomethylamino borane, dimethylaminoborane and trimethylamino borane;
the citric acid compound comprises citric acid or sodium salt of citric acid.
In the present invention, the nickel salt is preferably one or more of nickel sulfate, nickel chloride, nickel hypophosphite and nickel nitrate.
In the present invention, the concentration of the nickel salt in the activation liquid is preferably 5 to 50g/L, more preferably 10 to 40g/L, and most preferably 20 to 30g/L. In the present invention, the concentration of boric acid in the activating solution is preferably 10 to 50g/L, more preferably 20 to 40g/L, and most preferably 25 to 35g/L. In the present invention, the concentration of the boron-containing compound in the activating liquid is preferably 1 to 50g/L, more preferably 5 to 40g/L, and most preferably 10 to 30g/L. In the present invention, the concentration of the ammonium chloride in the activating solution is preferably 10 to 50g/L, more preferably 20 to 40g/L, and most preferably 25 to 35g/L. In the present invention, the concentration of the citric acid-based compound in the activating liquid is preferably 5 to 40g/L, more preferably 10 to 30g/L, and most preferably 15 to 25g/L.
In the present invention, the pH of the activating solution is preferably 3 to 7, more preferably 4 to 6, and most preferably 5.
In the invention, the preparation method of the activating solution disclosed by the technical scheme comprises the following steps:
dissolving nickel salt in water to obtain a solution A;
dissolving boric acid in water to obtain a solution B;
dissolving a citric acid compound and ammonium chloride in water to obtain a solution C;
mixing a boron-containing compound with the solution B to obtain a solution D;
mixing the solution A and the solution C to obtain a solution E;
and mixing the solution D and the solution E to obtain an activated liquid.
In the present invention, the boron-containing compound is preferably added to the solution B and mixed to obtain the solution D. In the present invention, the solution A is preferably added to the solution C with stirring and mixed to obtain the solution E. In the present invention, the solution D is preferably added to the solution E and mixed with stirring to obtain an activated liquid. In the present invention, the solution D and the solution E are mixed and then the pH is preferably adjusted to 3 to 7 with an alkali or an acid to obtain an activated liquid. In the present invention, the base is preferably sodium hydroxide; the acid is preferably sulfuric acid.
The invention provides a palladium-free activated electroless nickel plating method, which comprises the following steps:
sequentially carrying out pretreatment, activation treatment and electroless nickel plating on the base material;
the activating solution adopted in the activating treatment is the activating solution in the technical scheme.
In the present invention, the substrate is preferably a circuit board, more preferably a copper circuit board, most preferably a PCB copper circuit board, i.e. a printed copper circuit board.
The invention preferably carries out chemical oil removal, acid etching and activation treatment on the surface of the PCB copper circuit board and then carries out chemical nickel plating. The chemical degreasing is mainly used for removing oil stains on the surface of a PCB copper circuit board, which is important for the subsequent chemical nickel plating step, and ensures that the nickel plating layer with good bonding force with a copper substrate can be obtained only when the oil stains on the surface of the copper circuit board are free of oil stains; the acid etching is used for removing oxide on the surface of the PCB copper circuit board, and exposing fresh copper, so that the subsequent step is combined with the nickel layer more tightly; the activation treatment is to make the surface of the PCB copper circuit board be plated with a layer of nickel in advance, then the electroless nickel plating is carried out by utilizing the self-catalysis of the nickel, so that the electroless nickel plating is carried out.
In the present invention, the pretreatment preferably includes chemical degreasing and acid etching. In the present invention, the chemical degreasing temperature is preferably 30 to 80 ℃, more preferably 40 to 70 ℃, and most preferably 50 to 60 ℃; the chemical degreasing time is preferably 5 to 15min, more preferably 8 to 12min, and most preferably 10min. In the present invention, after the chemical degreasing is completed, the degreased substrate is preferably cleaned with water and then subjected to acid etching.
In the present invention, the acid etching temperature is preferably 20 to 30 ℃, more preferably 22 to 28 ℃, and most preferably 24 to 26 ℃; the acid etching time is preferably 0.5 to 2 minutes, more preferably 1 to 1.5 minutes. In the present invention, the acid etched substrate is preferably washed with water after the acid etching is completed.
In the present invention, the chemical degreasing agent preferably includes sodium hydroxide, sodium silicate, sodium carbonate, and sodium phosphate. In the present invention, the concentration of the sodium hydroxide in the chemical degreasing agent is preferably 10 to 30g/L, more preferably 15 to 25g/L, and most preferably 20g/L. In the present invention, the concentration of sodium silicate in the chemical degreasing agent is preferably 5 to 20g/L, more preferably 10 to 15g/L. In the present invention, the concentration of sodium carbonate in the chemical degreasing agent is preferably 10 to 50g/L, more preferably 20 to 40g/L, and most preferably 25 to 35g/L. In the present invention, the concentration of the sodium phosphate in the chemical degreasing agent is preferably 10 to 50g/L, more preferably 20 to 40g/L, and most preferably 25 to 35g/L. In the invention, the preparation method of the chemical degreasing reagent preferably comprises the following steps:
and mixing sodium hydroxide, sodium silicate, sodium carbonate, sodium phosphate and water to obtain the chemical degreasing reagent.
In the present invention, the water is preferably deionized water.
In the present invention, the acid etching agent preferably includes an inorganic acid and sodium persulfate. In the present invention, the inorganic acid is preferably one or more of sulfuric acid, hydrochloric acid and nitric acid. In the present invention, the concentration of the inorganic acid in the acid etching reagent is preferably 20 to 60mL/L, more preferably 30 to 50mL/L, and most preferably 35 to 45mL/L. In the present invention, the concentration of sodium persulfate in the acid etching reagent is preferably 10 to 80g/L, more preferably 20 to 70g/L, and most preferably 30 to 60g/L. In the present invention, the preparation method of the acid etching reagent is preferably as follows:
inorganic acid, water and sodium persulfate are mixed to obtain an acid etching reagent.
In the present invention, the temperature of the activation treatment is preferably 40 to 80 ℃, more preferably 50 to 70 ℃, and most preferably 60 ℃; the activation treatment time is preferably 2 to 20 minutes, more preferably 5 to 15 minutes, and most preferably 10 minutes. In the present invention, after the activation treatment is completed, the activated substrate is preferably washed with water. In the present invention, the activating solution used in the activating treatment is the activating solution described in the above technical solution, and will not be described herein.
In the invention, the temperature of the electroless nickel plating is preferably 70-90 ℃, more preferably 75-85 ℃, and most preferably 80 ℃; the electroless nickel plating time is preferably 20 to 30 minutes, more preferably 25 minutes.
In the present invention, the electroless nickel plating reagent preferably includes nickel salt, sodium hypophosphite, sodium acetate, malic acid, lactic acid and thiourea. In the present invention, the types of the nickel salts are the same as those described in the above technical scheme, and will not be described herein. In the present invention, the concentration of the nickel salt in the electroless nickel plating reagent is preferably 10 to 40g/L, more preferably 20 to 30g/L. In the present invention, the concentration of the sodium hypophosphite in the electroless nickel plating reagent is preferably 10 to 40g/L, more preferably 20 to 30g/L. In the present invention, the concentration of sodium acetate in the electroless nickel plating reagent is preferably 10 to 40g/L, more preferably 20 to 30g/L. In the present invention, the concentration of malic acid in the electroless nickel plating reagent is preferably 1 to 10g/L, more preferably 2 to 8g/L, and most preferably 3 to 6g/L. In the present invention, the concentration of the lactic acid in the electroless nickel plating reagent is preferably 5 to 20mL/L, more preferably 10 to 15mL/L. In the present invention, the concentration of thiourea in the electroless nickel plating reagent is preferably 1 to 10mg/L, more preferably 2 to 8mg/L, and most preferably 3 to 6mg/L.
In the present invention, the pH of the electroless nickel plating reagent is preferably 4.4 to 5.4, more preferably 5.
In the embodiment of the invention, the process flow chart of the palladium-free activated electroless nickel plating is shown in fig. 1, and the process flow is as follows:
the substrate is sequentially subjected to chemical degreasing, deionized water cleaning, acid etching (weak etching), deionized water cleaning, activation treatment, deionized water cleaning, chemical nickel plating, deionized water cleaning and drying.
Compared with the prior art, the invention adopts the activation solution to treat the surface of the substrate to carry out nickel preplating, and the boron-containing compound is added into the activation solution as the reducing agent, so that the activation energy of the reducing agent is lower than that of the electroless nickel plating by taking hypophosphite as the reducing agent, and the substrate can have enough self-catalysis effect in the plating solution to carry out self-deposition. The adoption of the activating solution for chemical nickel plating avoids the use of noble metal palladium in the activating process, thereby effectively reducing the cost of chemical nickel plating. In addition, the activating solution provided by the invention has high stability and no infiltration plating phenomenon, and the prepared plating layer is a Ni-P-B alloy plating layer and has better corrosion resistance.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.
FIG. 1 is a process flow diagram of palladium-free activated electroless nickel plating provided by an embodiment of the invention;
FIG. 2 is a scanning electron micrograph of the electroless nickel plated surface of a printed circuit board according to example 1 of the present invention;
FIG. 3 is a Tafil plot of the electroless nickel plating obtained in example 1 of the present invention versus the electroless nickel plating obtained in comparative example 1;
FIG. 4 is a Tafil plot of the electroless nickel plating layer obtained in example 2 of the present invention versus the electroless nickel plating layer obtained in comparative example 1.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The raw materials used in the following examples of the present invention are all commercially available. The PCB copper circuit board is an EP type commodity provided by Shenzhen New Fine Reed electronics Limited company.
Example 1
Preparing an activating solution:
according to the concentration of nickel sulfate in the activating solution of 40g/L, the concentration of boric acid of 30g/L, the concentration of ammonium chloride of 30g/L, the concentration of citric acid of 30g/L and the concentration of sodium borohydride of 1g/L, respectively weighing nickel sulfate, boric acid, ammonium chloride, citric acid and sodium borohydride;
dissolving nickel sulfate in deionized water to obtain a solution A; dissolving boric acid in deionized water to obtain a solution B; dissolving citric acid and ammonium chloride in deionized water to obtain a solution C; adding sodium borohydride into the solution B, and uniformly mixing to obtain a solution D; slowly adding the solution A into the solution C under the stirring condition, and uniformly mixing to obtain a solution E; adding the solution D into the solution E under stirring, uniformly mixing, and regulating the pH value to 7 by using sodium hydroxide or sulfuric acid to obtain an activated liquid.
Board pretreatment of the surface of a PCB copper circuit board:
adding sodium hydroxide, sodium silicate, sodium carbonate and sodium phosphate into deionized water according to the concentration of 10g/L of sodium hydroxide, 10g/L of sodium silicate, 30g/L of sodium carbonate and 30g/L of sodium phosphate, and uniformly mixing to obtain chemical oil removal liquid;
slowly adding concentrated sulfuric acid with the concentration of 20mL/L into deionized water to obtain solution F, adding sodium persulfate with the concentration of 40g/L into the solution F, and uniformly mixing to obtain an acid etching solution;
immersing the PCB copper circuit board in chemical degreasing liquid with the temperature of 70 ℃ for degreasing for 5min, and then taking out the PCB copper circuit board to be cleaned by deionized water; and under the normal temperature condition, immersing the PCB copper circuit board subjected to chemical degreasing treatment into the acid etching liquid to react for 1min, and cleaning with deionized water to finish the board pretreatment of the PCB copper circuit board.
Activating treatment and electroless nickel plating:
heating the prepared activating solution to 50 ℃, immersing the PCB copper circuit board obtained by pretreatment in the activating solution, keeping for 5min, and then cleaning with deionized water;
according to the concentration of nickel sulfate of 30g/L, sodium hypophosphite of 30g/L, sodium acetate of 30g/L, malic acid of 5g/L, lactic acid of 6ml/L, thiourea of 1mg/L, and regulating pH value of 4.8, the chemical nickel plating solution is obtained;
immersing the PCB copper circuit board obtained by the activation treatment in chemical nickel plating solution at 80 ℃ for reaction for 25min, and completing the chemical nickel plating process.
In the embodiment 1, the PCB copper circuit board is subjected to chemical degreasing, oil stains on the copper surface are removed, weak acid etching treatment is performed to remove an oxide film on the copper surface, and then the PCB copper circuit board is immersed into an activating solution to perform activation treatment, so that a catalytic layer of the PCB copper circuit board is obtained, and the subsequent chemical nickel plating step can be smoothly performed through the catalytic layer.
The surface of the PCB copper circuit board subjected to chemical nickel plating in the embodiment 1 of the invention is observed by a scanning electron microscope, the test result is shown in figure 2, and as can be seen from figure 2, the nickel particles on the surface of the circuit board are distributed uniformly and compactly, and nickel is plated successfully.
An electrochemical experiment was performed by using a PGSTAT302N electrochemical workstation manufactured by swiss vanton, and the tafel curve of the nickel plating layer obtained in example 1 of the present invention was tested, the test results are shown in fig. 3, and fig. 3 is the tafel curve of the nickel plating layer obtained in example 1 of the present invention and the nickel plating layer obtained in comparative example 1. As can be seen from fig. 3, the nickel plating layer obtained in example 1 of the present invention has a smaller corrosion current, has a better corrosion resistance than the nickel plating layer obtained by palladium activation, and is suitable for industrial production of PCBs.
Example 2
Electroless nickel plating was performed on a copper PCB according to the method described in example 1, differing from example 1 in that an activation solution was prepared at a concentration of 30g/L nickel chloride, a concentration of 35g/L boric acid, a concentration of 35g/L ammonium chloride, a concentration of 25g/L sodium citrate, and a concentration of 3g/L monomethylaminoborane, and pH was adjusted to 8.
The tafel plot of the nickel plating layer obtained in example 2 of the present invention was tested according to the method of example 1, and the test results are shown in fig. 4. As can be seen from fig. 4, the electroless nickel plating layer obtained in example 2 has better corrosion resistance than the nickel plating layer obtained by palladium activation, and is suitable for industrial production of PCBs.
Example 3
The electroless nickel plating of the copper PCB was performed as described in example 1, with the difference from example 1 in that the electroless oil remover was formulated with a concentration of 12g/L sodium hydroxide, 12g/L sodium silicate, 25g/L sodium carbonate, and 25g/L sodium phosphate.
The tafel plot of the nickel plating layer obtained in example 3 of the present invention was tested according to the method of example 1, and as a result of the test, the electroless nickel plating layer obtained in example 3 had better corrosion resistance than the nickel plating layer obtained by activation with palladium, and was suitable for industrial production of PCBs.
Comparative example 1
The method for chemically plating nickel on the PCB copper circuit board by adopting palladium activation and chemical plating comprises the following specific processes:
the activating solution is as follows: palladium chloride 0.1g/L,36.5% concentrated hydrochloric acid 5mL/L.
The board pretreatment process of the surface of the PCB copper circuit board is the same as that of the embodiment 1;
the activation treatment process comprises the following steps: immersing the PCB copper circuit board obtained by pretreatment in an activating solution for 1min, and then cleaning with deionized water;
the electroless nickel plating process was the same as in example 1.
The tafel curves of the nickel plating layers obtained in comparative example 1 of the present invention were measured in the same manner as in example 1, and the measurement results are shown in fig. 3 to 4.
From the above examples, the present invention provides an activating solution comprising: nickel salts, boric acid, boron-containing compounds, ammonium chloride and citric acid compounds; the boron-containing compound comprises one or more of sodium borohydride, monomethylamino borane, dimethylaminoborane and trimethylamino borane; the citric acid compound comprises citric acid or sodium salt of citric acid. Compared with the prior art, the invention adopts the activating solution with specific components, under the comprehensive action of various components, noble metal palladium is not needed to be adopted for activation in the chemical nickel plating process, and meanwhile, the plating layer has good corrosion resistance, the activating solution has high stability, and the problem of high cost caused by the activation of the noble metal palladium in the manufacturing process of the printed circuit board is effectively reduced.

Claims (6)

1. An activating solution comprises the following components: the concentration of nickel chloride is 30g/L, the concentration of boric acid is 35g/L, the concentration of ammonium chloride is 35g/L, the concentration of sodium citrate is 25g/L, and the concentration of monomethylamino borane is 3g/L;
the pH value of the activating solution is 8.
2. A method of preparing the activation liquid of claim 1, comprising:
dissolving nickel chloride in water to obtain a solution A;
dissolving boric acid in water to obtain a solution B;
sodium citrate and ammonium chloride are dissolved in water to obtain solution C;
mixing the monomethylamino borane with the solution B to obtain a solution D;
mixing the solution A and the solution C to obtain a solution E;
and mixing the solution D and the solution E to obtain an activated liquid.
3. A palladium-free activated electroless nickel plating method comprising:
sequentially carrying out pretreatment, activation treatment and electroless nickel plating on the base material;
the activating solution adopted in the activating treatment is the activating solution of claim 1;
the temperature of the activation treatment is 40-80 ℃; the activation treatment time is 5-15 min.
4. A method according to claim 3, wherein the pre-processing comprises:
sequentially carrying out chemical degreasing and acid etching on the base material;
the chemical degreasing agent comprises: sodium hydroxide, sodium silicate, sodium carbonate and sodium phosphate;
the acid etching reagent comprises: inorganic acids and sodium persulfate.
5. A method according to claim 3, wherein the electroless nickel plating reagent comprises:
nickel salts, sodium hypophosphite, sodium acetate, malic acid, lactic acid and thiourea;
the pH value of the chemical nickel plating reagent is 4.4-5.4.
6. A method according to claim 3, wherein the electroless nickel is at a temperature of 70-90 ℃;
the electroless nickel plating time is 20-30 min.
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CN110724943A (en) * 2019-11-29 2020-01-24 四川英创力电子科技股份有限公司 Palladium-free activating solution before chemical nickel plating on copper surface, preparation method and nickel plating method
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