CN115433928A - Chemical silver plating liquid medicine and chemical silver plating method for 5G high-frequency circuit board - Google Patents
Chemical silver plating liquid medicine and chemical silver plating method for 5G high-frequency circuit board Download PDFInfo
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- CN115433928A CN115433928A CN202211403702.5A CN202211403702A CN115433928A CN 115433928 A CN115433928 A CN 115433928A CN 202211403702 A CN202211403702 A CN 202211403702A CN 115433928 A CN115433928 A CN 115433928A
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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
- C23C18/31—Coating with metals
- C23C18/42—Coating with noble metals
- C23C18/44—Coating with noble metals using reducing agents
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/10—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern
- H05K3/18—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using precipitation techniques to apply the conductive material
- H05K3/181—Apparatus or processes for manufacturing printed circuits in which conductive material is applied to the insulating support in such a manner as to form the desired conductive pattern using precipitation techniques to apply the conductive material by electroless plating
Abstract
The invention discloses chemical silver plating liquid medicine and a chemical silver plating method for a 5G high-frequency circuit board, and relates to the technical field of chemical silver plating of circuit boards. The chemical silver plating liquid medicine for the 5G high-frequency circuit board comprises the following components in parts by mass: 1.0-4.0% of soluble silver ion compound; 0.8-3.0% of composite complexing agent; 0.2 to 2.0 percent of attachment stabilizer; 0.2 to 2.0 percent of silver ion stabilizer; 0.2 to 2.0 percent of discoloration inhibitor; 0.2 to 2.5 percent of wetting agent; the balance being solvent; the composite complexing agent is a mixture of a complexing agent A and a complexing agent B, and the mass ratio of the complexing agent A to the complexing agent B is 1.2-2.0. The chemical silvering liquid medicine can ensure that the thickness of a silver layer reaches 0.6 mu m within 2 minutes, the silver layer is uniform, white and semi-bright, flat and compact, the surface roughness Ra of a plating layer is less than 0.3, and the insertion loss of the silver layer is less than 0.7dB/inch.
Description
Technical Field
The invention relates to the technical field of chemical silver plating of circuit boards, in particular to chemical silver plating liquid medicine and a chemical silver plating method for a 5G high-frequency circuit board.
Background
With the rapid development of the Printed Circuit Board (PCB) industry, especially the coming 5G era, high-frequency and high-speed signal transmission becomes the trend of the PCB industry, however, with the increase of the transmission rate, the working frequency thereof is also gradually increased from 3 GHz to above 15 GHz, and the skin effect becomes more obvious.
The skin effect means that the current on the conductor is almost uniformly distributed inside the conductor at low frequencies; when the frequency is high, an alternating current or alternating electromagnetic field appears in the conductor, so that the current distribution in the conductor is changed, and the current is mainly concentrated on the thin layer on the outer surface of the conductor; the thinner the thin layer is at higher frequency, the closer to the surface of the conductor, the higher the current density is, and the current in the opposite conductor is little or even no current.
The signal loss of the PCB mainly includes conductor loss, dielectric loss, radiation and crosstalk loss, wherein the skin effect is a very important influencing factor in the conductor loss, and the PCB chemical supplier can reduce the influence of the conductor loss by selecting a better processing mode in the surface treatment process.
The final surface treatment process of the printed circuit board commonly used at present comprises the following steps: organic solderability protective coatings (OSP), electroless nickel gold plating, electroless tin plating, electroless silver plating, and the like. The performance of OSP can be degraded along with the time, meanwhile, the performance of repeated welding can not be ensured, and the OSP can not be used on a printed circuit board with higher requirements; the electroless nickel gold plating has the advantages of stable performance, repeated welding, compatibility with various soldering fluxes, assembly modes and the like, but has the defects of difficult control of catalysis on high-density circuits and high cost; the chemical tinning has the advantages of low cost, less discoloration, capability of turning over, surface leveling and suitability for fine lines, but is easy to generate symbiotic alloy to reduce the storage period and the surface conductivity, and thiourea in the components can attack green oil. The chemical silver plating surface treatment mode has the advantages of simple process, environmental protection, capability of meeting various assembly modes, excellent electric and thermal conductivity, stable interface performance and the like, and becomes a hotspot of research in the field of PCBs.
At present, there are some chemical silver plating solutions applied to printed circuit boards. Chinese patent application CN 114959666A discloses an electroless silver plating solution and a novel electroless silver plating method, the components of which comprise 100g/L-120g/L of complexing agent, 5g/L-10g/L of soluble silver cyanide and 0.3g/L-0.6g/L of reducing agent, the adhesive force of the plated silver layer is good, and no pore appears.
Chinese patent application CN 111876760A provides a chemical silver plating solution for printed circuit boards and a preparation method of the circuit boards, wherein the components of the chemical silver plating solution comprise 15-30g/L of water-soluble silver ions, 0-50g/L of copper ion complexing agent B, 3.5-5g/L of water-soluble ionic liquid corrosion inhibitor, 0.5-1.5g/L of stabilizer, 0.1-0.5g/L of crystal grain control agent, 1-5g/L of migration inhibitor, 1-20g/L of pH regulator and 5.5-6.5.
Chinese patent application CN 111690915A introduces a chemical silver plating solution and a preparation method thereof. The chemical silver plating solution comprises silver salt with the concentration of 0.5-5 g/L, complexing agent with the concentration of 1.5-40 g/L and reducing agent with the concentration of 2.5-30 g/L, and the chemical silver plating solution is suitable in material selection and reasonable in proportion; tests show that the chemical silver plating solution has good stability, and the plating layer has proper thickness and good quality.
Because the standard electrode potential of silver is 0.46V higher than that of copper, the reaction can occur rapidly without adding any additive, so that the formed silver plating layer has a loose structure and cannot meet the requirement of uniformity and compactness, and therefore, various additives are required to be added to control the reaction to be carried out at a reasonable rate.
The existing chemical silver plating liquid medicine technical scheme can basically meet the requirements of surface treatment and has good corrosion resistance, but because the plating uniformity of the produced product is poor, the conductive effect and the roughness of the product are influenced, and the manufacturing requirements of high-frequency signal transmission on a printed circuit board can not be met. Therefore, it is very meaningful to develop a chemical silver plating solution for high-frequency circuit boards.
Disclosure of Invention
Aiming at the defects of the prior art, the chemical silver plating liquid medicine for the 5G high-frequency circuit board is applied to the chemical silver plating process of the circuit board, can ensure that the plating layer of the circuit board is uniform, flat and compact, has low roughness and insertion loss, meets the requirements of the 5G high-frequency circuit board, and ensures that the circuit board has a good conductive effect.
Meanwhile, the invention also provides a chemical silver plating process by adopting the chemical silver plating liquid medicine for the 5G high-frequency circuit board, which can ensure that the thickness of a silver layer reaches 0.6 mu m in 2 minutes, the appearance of the chemical silver plating layer is a uniform white semi-bright silver layer, and the chemical silver plating layer is flat and compact, the surface roughness Ra of the plating layer is less than 0.3, and the insertion loss of the silver layer is less than 0.7 dB/inch; the plating layer has the characteristics of high efficiency, good effect, no cyanogen in the process, green and environmental protection.
On one hand, the invention discloses a chemical silver plating liquid medicine for a 5G high-frequency circuit board, which comprises the following components in parts by mass:
1.0-4.0% of soluble silver ion compound;
0.8-3.0% of composite complexing agent;
0.2 to 2.0 percent of adhesion stabilizer;
0.2 to 2.0 percent of silver ion stabilizer;
0.2 to 2.0 percent of discoloration inhibitor;
0.2 to 2.5 percent of wetting agent;
the balance being solvent;
the composite complexing agent is a mixture of a complexing agent A and a complexing agent B, and the mass ratio of the complexing agent A to the complexing agent B is 1.2-2.0;
the complexing agent A is one or a mixture of more of 5 '-acetamido-2' -carboxyl-4-dimethylamino-2-hydroxybenzophenone and 4 '-acetamido-2' -carboxyl-4-dimethylamino-2-hydroxybenzophenone; the complexing agent B is one or a mixture of more of (S) -3-carboxyl-4-hydroxyphenyl glycine and (R) -3-carboxyl-4-hydroxyphenyl glycine.
Preferably, the attachment stabilizer is one or more of 2-thiopheneacrylic acid, 2-furanacrylic acid and 3- (4-pyridyl) acrylic acid.
Preferably, the silver ion stabilizer is one or more of 1, 2-benzenedithiol, 1, 4-benzenedithiol and m-dibenzyl mercaptan.
Preferably, the discoloration inhibitor is one or a mixture of more of 1-hydroxycyclopentane carboxylic acid, 3-hydroxyadamantane-1-carboxylic acid and trans-4-hydroxycyclohexane carboxylic acid.
Preferably, the wetting agent is one or a mixture of more of cyclohexyl sulfamic acid, 3-aminopropane sulfonic acid and 2, 4-diaminobenzene sulfonic acid.
Preferably, the soluble silver ion compound is one or a mixture of silver nitrate, silver citrate and silver phosphate.
Preferably, the solvent is water.
Preferably, the composition consists of the following components in percentage by mass:
2.0% of soluble silver ion compound;
2.0 percent of composite complexing agent;
1.0% of an adhesion stabilizer;
1.0% of silver ion stabilizer;
1.0% of a discoloration inhibitor;
1.0% of wetting agent;
the balance being solvent.
The invention also discloses a preparation method of the chemical silver-plating liquid medicine for the 5G high-frequency circuit board, which is to mix and stir soluble silver ion compounds, compound complexing agents, adhesion stabilizers, silver ion stabilizers, discoloration inhibitors, wetting agents and the balance solvents to obtain the chemical silver-plating liquid medicine for the 5G high-frequency circuit board.
On the other hand, the invention discloses a chemical silver plating method of a circuit board, which adopts the chemical silver plating liquid medicine containing the tin protection additive for the 5G high-frequency circuit board to carry out chemical silver plating on the circuit board; the technological parameters of the chemical silver plating are as follows: the temperature is 40-50 deg.C, and the time is 2-20min.
Has the advantages that:
(1) In the chemical silver plating liquid medicine for the 5G high-frequency circuit board, the soluble silver ion compound provides silver ions for chemical silver plating, so that the chemical reaction Cu +2Ag is ensured + =Cu 2+ +2Ag can occur; the composite complexing agent has two main functions, namely, the composite complexing agent reacts with copper ions to produce soluble complex to promote copper decomposition and accelerate silver precipitationSecondly, the deposition of silver ions is inhibited, and the silver ions interact with each other, so that the deposition rate of the silver is very stable, and the formed silver layer is uniform; the adhesion stabilizer is used for improving the adhesion of the silver layer and generating a required crystal structure and better silver surface appearance; the silver ion stabilizer is used for preventing photosensitive decomposition of silver salt and enhancing the stability of the solution; the discoloration inhibitor can improve the discoloration resistance of the silver surface and prevent the surface of the plating from discoloring; the wetting agent can enhance the fluidity of each effective functional component of the chemical silver plating liquid medicine and simultaneously promote the uniform formation of a plating layer.
(2) According to the chemical silver plating method of the circuit board, chemical silver plating liquid medicine for the 5G high-frequency circuit board is applied to a chemical silver plating process for circuit board surface treatment, and the chemical silver plating liquid medicine contains active ingredients such as a soluble silver ion compound, a composite complexing agent, an attachment stabilizing agent, a silver ion stabilizing agent, a discoloration inhibitor, a wetting agent and the like; the chemical silver plating liquid medicine is stable, does not generate precipitate, is simple to operate and maintain as a single component, and can be continuously used by adding and supplementing; the chemical silvering speed is high, and the thickness of the silver layer can reach 0.6um after the silver is deposited for 2 minutes. The chemical silver plating method is a cyanide-free operation and has the advantage of environmental protection; after the circuit board is chemically silvered, the production requirement of a 5G high-frequency circuit board is met, and the appearance of the chemical silvered layer is a uniform white semi-bright silver layer, is smooth and compact, and has low surface roughness and insertion loss.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a diagram showing the effect of a circuit board after chemical silver plating is performed on the circuit board in embodiment 1 of the present invention;
FIG. 2 is an SEM image of 1000 times of a plated layer after electroless silver plating of a wiring board according to example 1 of the present invention;
FIG. 3 is a diagram showing the effects of the circuit board after the circuit board is subjected to electroless silver plating by using a comparative example 20;
fig. 4 is an SEM image 1000 times of the plated layer after electroless silver plating of the wiring board using comparative example 20.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It is also to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be further understood that the term "and/or" as used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.
It should be further understood that the term "concentration" as used in the present specification and appended claims refers to mass concentration, while "%" refers to mass percent; unless otherwise indicated.
A chemical silver plating liquid medicine for a 5G high-frequency circuit board,
the composite material comprises the following components in parts by mass:
1.0-4.0% of soluble silver ion compound;
0.8-3.0% of composite complexing agent;
0.2 to 2.0 percent of adhesion stabilizer;
0.2 to 2.0 percent of silver ion stabilizer;
0.2 to 2.0 percent of discoloration inhibitor;
0.2 to 2.5 percent of wetting agent;
the balance being solvent;
the soluble silver ion compound is one or more of silver nitrate (CAS number: 7761-88-8), silver citrate (CAS number: 206986-90-5) and silver phosphate (CAS number: 7784-09-0);
the composite complexing agent is a mixture of a complexing agent A and a complexing agent B, and the mass ratio of the complexing agent A to the complexing agent B is 1.2-2.0;
the complexing agent A is one or a mixture of more of 5 '-acetamido-2' -carboxyl-4-dimethylamino-2-hydroxybenzophenone (CAS number: 166442-37-1) and 4 '-acetamido-2' -carboxyl-4-dimethylamino-2-hydroxybenzophenone (CAS number: 166442-36-0); the complexing agent B is one or a mixture of more of (S) -3-carboxyl-4-hydroxyphenyl glycine (CAS number: 55136-48-6) and (R) -3-carboxyl-4-hydroxyphenyl glycine (CAS number: 13861-03-5);
the adhesion stabilizer is one or more of 2-thiophene acrylic acid (CAS number: 15690-25-2), 2-furan acrylic acid (CAS number: 539-47-9) and 3- (4-pyridyl) acrylic acid (CAS number: 5337-79-1);
the silver ion stabilizer is one or more of 1, 2-benzenedithiol (CAS number: 17534-15-5), 1, 4-benzenedithiol (CAS number: 624-39-5) and m-dibenzyl mercaptan (CAS number: 41563-69-3);
the discoloration inhibitor is one or more of 1-hydroxycyclopentane carboxylic acid (CAS number: 16841-19-3), 3-hydroxyadamantane-1-carboxylic acid (CAS number: 42711-75-1) and trans-4-hydroxycyclohexane carboxylic acid (CAS number: 3685-26-5);
the wetting agent is one or more of cyclohexyl sulfamic acid (CAS number: 100-88-9), 3-aminopropane sulfonic acid (CAS number: 3687-18-1) and 2, 4-diaminobenzene sulfonic acid (CAS number: 88-63-1);
the balance is solvent, which is preferably water, which may be tap water or DI water (non-ionic water).
A preparation method of chemical silver plating liquid medicine for a 5G high-frequency circuit board,
and (3) stirring and mixing a soluble silver ion compound, a composite complexing agent, an attachment stabilizer, a silver ion stabilizer, a discoloration inhibitor, a wetting agent and the balance of solvent to obtain the chemical silver plating liquid medicine for the 5G high-frequency circuit board.
The preferred technological parameters of stirring and mixing are as follows: the temperature is 20-40 ℃, and the time is 20-40min; preferably, the temperature is normal temperature and the time is 30min.
Example 1
The chemical silver plating liquid medicine is prepared by sequentially weighing soluble silver ion compounds, compound complexing agents, attachment stabilizers, silver ion stabilizers, discoloration inhibitors, wetting agents and the like and the balance of water according to the following formula, adding the components and the balance of water into a reaction kettle, stirring and mixing for 30 minutes at normal temperature to obtain chemical silver plating liquid medicine, and sealing and storing the liquid medicine for later use.
The content of soluble silver ion compound is 2.0%, specifically silver nitrate;
the content of the composite complexing agent is 2.0 percent, specifically, the complexing agent A is 5 '-acetamido-2' -carboxyl-4-dimethylamino-2-hydroxybenzophenone, and the complexing agent B is (S) -3-carboxyl-4-hydroxyphenyl glycine; the mass ratio of the complexing agent A to the complexing agent B in the composite complexing agent is 1.5;
the content of the attachment stabilizer is 1.0 percent, in particular to 2-thiophene acrylic acid;
the silver ion stabilizer content is 1.0%, specifically 1, 2-benzenedithiol;
the content of the discoloration inhibitor is 1.0 percent, in particular to 1-hydroxycyclopentane carboxylic acid;
a humectant content of 1.0%, specifically cyclohexylsulfamic acid;
the balance being tap water.
Example 2
The chemical silver plating liquid medicine is prepared by sequentially weighing the components of soluble silver ion compound, composite complexing agent, adhesion stabilizer, silver ion stabilizer, discoloration inhibitor, wetting agent and the like and the balance of water according to the following formula, adding the components and the balance of water into a reaction kettle, stirring and mixing for 30 minutes at normal temperature to obtain chemical silver plating liquid medicine, and sealing and storing the liquid medicine for later use.
The content of soluble silver ion compound is 2.0%, specifically silver citrate;
the content of the composite complexing agent is 2.0 percent, specifically, the complexing agent A is 5 '-acetamido-2' -carboxyl-4-dimethylamino-2-hydroxybenzophenone, and the complexing agent B is (R) -3-carboxyl-4-hydroxyphenyl glycine; the mass ratio of the complexing agent A to the complexing agent B in the composite complexing agent is 1.5;
the content of the attachment stabilizer is 1.0 percent, in particular to 2-furan acrylic acid;
the content of silver ion stabilizer is 1.0%, specifically 1, 4-benzenedithiol;
the content of the discoloration inhibitor is 1.0 percent, in particular to 3-hydroxyl adamantane-1-carboxylic acid;
the humectant content is 1.0%, specifically 3-aminopropanesulfonic acid;
the balance being tap water.
Example 3
The chemical silver plating liquid medicine is prepared by sequentially weighing soluble silver ion compounds, compound complexing agents, attachment stabilizers, silver ion stabilizers, discoloration inhibitors, wetting agents and the like and the balance of water according to the following formula, adding the components and the balance of water into a reaction kettle, stirring and mixing for 30 minutes at normal temperature to obtain chemical silver plating liquid medicine, and sealing and storing the liquid medicine for later use.
The content of soluble silver ion compound is 2.0%, specifically silver phosphate;
the content of the composite complexing agent is 2.0 percent, specifically, the complexing agent A is 4 '-acetamido-2' -carboxyl-4-dimethylamino-2-hydroxybenzophenone, and the complexing agent B is (R) -3-carboxyl-4-hydroxyphenyl glycine; the mass ratio of the complexing agent A to the complexing agent B in the composite complexing agent is 1.5;
the content of the attachment stabilizer is 1.0 percent, in particular to 3- (4-pyridyl) acrylic acid;
the content of the silver ion stabilizer is 1.0 percent, and concretely is m-dibenzyl mercaptan;
the content of the discoloration inhibitor is 1.0 percent, and specifically is trans-4-hydroxycyclohexane carboxylic acid;
the content of the wetting agent is 1.0 percent, in particular to 2, 4-diaminobenzene sulfonic acid;
the balance being tap water.
Example 4
The chemical silver plating liquid medicine is prepared by sequentially weighing soluble silver ion compounds, compound complexing agents, attachment stabilizers, silver ion stabilizers, discoloration inhibitors, wetting agents and the like and the balance of water according to the following formula, adding the components and the balance of water into a reaction kettle, stirring and mixing for 30 minutes at normal temperature to obtain chemical silver plating liquid medicine, and sealing and storing the liquid medicine for later use.
The content of soluble silver ion compound is 2.0%, specifically silver nitrate;
the content of the composite complexing agent is 2.0 percent, specifically, the complexing agent A is 5 '-acetamido-2' -carboxyl-4-dimethylamino-2-hydroxybenzophenone, and the complexing agent B is (S) -3-carboxyl-4-hydroxyphenyl glycine; the mass ratio of the complexing agent A to the complexing agent B in the composite complexing agent is 1.5;
the content of the attachment stabilizer is 1.0 percent, in particular to 2-thiophene acrylic acid;
the silver ion stabilizer content is 1.0%, specifically 1, 2-benzenedithiol;
the content of discoloration inhibitor is 1.0%, specifically 1-hydroxycyclopentane carboxylic acid;
a humectant content of 1.0%, specifically cyclohexylsulfamic acid;
the balance being tap water.
Example 5
The chemical silver plating liquid medicine is prepared by sequentially weighing soluble silver ion compounds, compound complexing agents, attachment stabilizers, silver ion stabilizers, discoloration inhibitors, wetting agents and the like and the balance of water according to the following formula, adding the components and the balance of water into a reaction kettle, stirring and mixing for 30 minutes at normal temperature to obtain chemical silver plating liquid medicine, and sealing and storing the liquid medicine for later use.
The content of soluble silver ion compound is 1.0%, specifically silver nitrate;
the content of the composite complexing agent is 0.8 percent, specifically, the complexing agent A is 5 '-acetamido-2' -carboxyl-4-dimethylamino-2-hydroxybenzophenone, and the complexing agent B is (S) -3-carboxyl-4-hydroxyphenyl glycine; the mass ratio of the complexing agent A to the complexing agent B in the composite complexing agent is 1.2;
the content of the attachment stabilizer is 0.2 percent, in particular to 2-thiophene acrylic acid;
the silver ion stabilizer content is 0.2%, specifically 1, 2-benzenedithiol;
the content of discoloration inhibitor is 0.2%, specifically 1-hydroxycyclopentane carboxylic acid;
humectant content of 0.2%, specifically cyclohexyl sulfamic acid;
the balance being tap water.
Example 6
The chemical silver plating liquid medicine is prepared by sequentially weighing soluble silver ion compounds, compound complexing agents, attachment stabilizers, silver ion stabilizers, discoloration inhibitors, wetting agents and the like and the balance of water according to the following formula, adding the components and the balance of water into a reaction kettle, stirring and mixing for 30 minutes at normal temperature to obtain chemical silver plating liquid medicine, and sealing and storing the liquid medicine for later use.
The content of soluble silver ion compound is 4.0%, specifically silver nitrate;
the content of the composite complexing agent is 3.0 percent, specifically, the complexing agent A is 5 '-acetamido-2' -carboxyl-4-dimethylamino-2-hydroxybenzophenone, and the complexing agent B is (S) -3-carboxyl-4-hydroxyphenyl glycine; the mass ratio of the complexing agent A to the complexing agent B in the composite complexing agent is 1;
the content of the adhesion stabilizer is 2.0 percent, in particular to 2-thiophene acrylic acid;
the content of silver ion stabilizer is 2.0%, specifically 1, 2-benzene dithiol;
the content of the discoloration inhibitor is 2.0 percent, in particular to 1-hydroxycyclopentane carboxylic acid;
a humectant content of 2.5%, specifically cyclohexylsulfamic acid;
the balance being tap water.
The following comparative examples, in particular table 1 below, were set up according to example 1.
TABLE 1 Table for distinguishing comparative examples from example 1
Chemical silver plating method for circuit board
Carrying out chemical silver plating on the circuit board by adopting chemical silver plating liquid medicine for the 5G high-frequency circuit board; the technological parameters of the chemical silver plating are as follows: the temperature is 40-50 deg.C, and the time is 2-20min.
The chemical silver plating surface treatment process comprises the chemical silver plating method, and specifically comprises S1 alkaline washing → S2 water washing → S3 micro-etching → S4 water washing → S5 chemical silver plating → S6 water washing → S7 drying. The chemical silver plating method level is S5 chemical silver plating working procedure.
The S1 alkaline washing process is to perform alkaline washing treatment on a circuit board to be plated (with a copper circuit on the surface) to remove oil stains and fingerprints on the board surface, and the solution in the alkaline washing tank is as follows: 5% NaOH,5% Na 2 CO 3 The balance being tap water; the technological parameters are as follows: adopts a dipping mode, the bath length is 2.0m, the bath solution temperature is 25 +/-5 ℃, the linear velocity is 4.0 +/-0.2 m/min, and the pressure is 1.5 +/-0.5 kg/cm 2 ；
And the S2 water washing procedure is to wash the circuit board subjected to the S1 alkali washing procedure by using tap water, and the technological parameters of water washing are as follows: adopting a spraying mode, the length of the groove is 2.0m, the washing temperature is 25 +/-5 ℃, the linear speed is 4.0 +/-0.2 m/min, and the pressure is 1.5 +/-0.5 kg/cm 2 ；
And the S3 microetching step is to microetch the circuit board after the S2 water washing step, the surface after the microetching is rough, so that the silver is conveniently deposited, and the solution in the microetching groove is as follows: 5% of Na 2 S 2 O 3 ，5%H 2 SO 4 The balance being tap water; the technological parameters are as follows: the film is removed by adopting a spraying mode, the length of the tank is 2.0m, the temperature of the tank liquor is 25 +/-5 ℃, the linear velocity is 4.0 +/-0.2 m/min, and the pressure is 1.5 +/-0.5 kg/cm 2 ；
And the S4 washing procedure is to wash the circuit board subjected to the S3 micro-etching procedure by using tap water, and the technological parameters of the washing procedure are as follows: adopting a spraying mode, the length of the groove is 2.0m, the washing temperature is 25 +/-5 ℃, the linear speed is 4.0 +/-0.2 m/min, and the pressure is 1.5 +/-0.5 kg/cm 2 ；
The S5 chemical silver plating deposits a layer of silver on the circuit board after the S4 washing procedure, and the chemical silver plating tank uses the chemical silver plating liquid medicine of the invention, and the process parameters are as follows: adopting a dipping mode, the length of the tank is 4.0m, the washing temperature is 45 +/-5 ℃, the linear speed is 2.0 +/-0.2 m/min, and the pressure is 1.5 +/-0.5 kg/cm 2 ；
The S6 water washing process is to wash the circuit board after the S5 chemical silver plating by tap water, and the process of water washing is carried outThe number is as follows: adopting a spraying mode, the length of the groove is 2.0m, the washing temperature is 25 +/-5 ℃, the linear speed is 4.0 +/-0.2 m/min, and the pressure is 1.5 +/-0.5 kg/cm 2 ；
And S7, drying is to dry the circuit board after the S6 water washing procedure, and the drying process parameters are as follows: the temperature is 70 plus or minus 5 ℃, and the length of a drying section is 4.0 m; linear speed 2.0 + -0.3 m/min, pressure 1.5 + -0.5 kg/cm 2 。
Performance test
The chemical silver plating liquid medicine of the invention mainly has four aspects:
the first is the chemical silvering thickness of the circuit board, a hand-held silvering layer thickness gauge (brand: jiangsu Tianrui instruments, inc., model: explorer 5000T) is adopted to detect the circuit board after silvering and drying, six different positions are detected, and an average value is taken;
secondly, observing the color of the silver layer on the circuit board after the silver plating is dried, wherein whether the silver layer is discolored or not is judged;
thirdly, the roughness of the silver coating is detected by adopting a white light interferometer (brand: bruker, model: cintour GT-IM), the circuit board after silver plating and drying is detected, three different positions are detected, and an average value is obtained;
and fourthly, the signal insertion loss of the silver layer surface is obtained, the circuit board after silver plating drying is taken and detected by a vector network analyzer (brand: agilent, model: E5063A), the measuring frequency is 12.89 GHz, sine waves are input and measured, and the ratio of the transmission sine waves to the incidence sine waves is calculated, so that the insertion loss value sigma (dB/inch) can be obtained. The high-frequency signal loss value of the PCB is generally characterized by the insertion loss in the industry, and the transmission loss of a 12.89 GHz signal is required to be less than 1.067 dB/inch.
Where ρ is the metal resistivity, f is the signal frequency, and μ is the free space permeability.
The chemical silver plating liquid medicine prepared by the embodiment and the comparative example is combined with a chemical silver plating method and a chemical silver plating surface treatment process of the circuit board to carry out chemical silver plating treatment on the same batch of circuit boards; then, the circuit board after the chemical silver plating surface treatment is subjected to performance detection, and the detection results are shown in tables 2-3.
TABLE 2 results of measuring the properties of electroless silver plating baths prepared in examples 1 to 6
TABLE 3 results of testing the performance of electroless silver plating solutions prepared in comparative examples 1 to 20
After the circuit board is subjected to chemical silver plating by adopting the method of embodiment 1, the effect picture of the circuit board is shown as figure 1, and the SEM picture of the plating layer is shown as figure 2 by 1000 times. After the circuit board is subjected to chemical silver plating by using the comparative example 20, the effect picture of the circuit board is shown in figure 3, and the SEM picture of the plating layer is shown in figure 4 at 1000 times.
As can be seen from the experimental data of the examples 1-6 in the table 2, the chemical silvering liquid medicine has high silvering speed, and the thickness of the silver layer can reach 0.6um after 2 minutes; the chemical silver plating method is a cyanide-free operation and has the advantage of environmental protection, the appearance of the chemical silver plating layer is a uniform white semi-bright silver layer, the chemical silver plating layer is flat and compact, the surface roughness Ra of the plating layer is less than 0.3, the insertion loss of the silver layer is less than 0.7dB/inch, and the production requirement of a 5G high-frequency circuit board is met.
Comparative examples 1 to 6 are different from example 1 in that the chemical silver plating solution of the present invention lacks soluble silver ion compound, complex complexing agent, adhesion stabilizer, silver ion stabilizer, discoloration inhibitor, and wetting agent as single components, respectively. The experimental data in Table 3 show that the soluble silver ion compound provides silver ions for the chemical silver plating process, and ensures the chemical reaction of Cu +2Ag + =Cu 2+ +2Ag can occur, and if a soluble silver ion compound is absent, a silver layer cannot be formed; the composite complexing agent, the adhesion stabilizer, the silver ion stabilizer and the wetting agent play unique roles, and if one of the components is lacked, the thickness of the silver layer is reduced,The surface roughness and insertion loss of the silver layer are both increased; the discoloration inhibitor plays a role in inhibiting the discoloration of the silver layer, if the discoloration inhibitor is lacked, the discoloration condition of the coating occurs, the thickness of the silver layer is reduced, and the surface roughness and the insertion loss of the silver layer are increased, which shows that the functional components in the chemical silver plating liquid can be synergistic with each other, so that the uniformity, the flatness and the compactness of the silver layer can be influenced, the surface roughness and the insertion loss of the silver layer are further influenced, and the silver plating effect can be influenced by the lack of any one of the components.
Comparative examples 7 to 8 differ from example 1 in that the composite complexing agent component contained only complexing agent a and complexing agent B, respectively. The experimental data in table 3 show that the complexing agent of a single component has poor complexing performance, the silver layer has low thickness, and the surface roughness and the insertion loss of the silver layer are both large, so that the standard requirements of a 5G high-frequency circuit board cannot be met.
Comparative examples 9 to 14 are different from example 1 in that the soluble silver ion compound, complex type complexing agent, adhesion stabilizer, silver ion stabilizer, discoloration inhibitor, and wetting agent in the electroless silver plating solution of the present invention are respectively higher than the upper limit of the concentration of the present invention. The experimental data in table 3 show that if the content of the soluble silver ion compound is too high, the deposition rate of the coating is increased, so that the thickness of the coating is increased, and the surface roughness and the insertion loss are large; if the content of the wetting agent is too high, the flowability of each component in the liquid medicine is enhanced, the deposition rate of the coating is accelerated, the thickness of the coating is increased, and meanwhile, the surface roughness and the insertion loss are also large; if the concentrations of the complex complexing agent, the adhesion stabilizer, the silver ion stabilizer, and the discoloration inhibitor are too high, the experimental effect is not changed much as compared with example 1, but the concentrations of these components may be within the concentration range defined in the present invention from the viewpoint of cost.
Comparative example 15 and comparative example 16 differ from example 1 only in that the mass ratio of complexing agent a to complexing agent B in the composite complexing agent is lower and higher than the requirements of the present invention, respectively. The experimental data in table 3 show that the silver plating effect is affected by too low or too high ratio of the complexing agent a to the complexing agent B because the composite complexing agents with different proportional concentrations have different action strengths between promoting the deposition of silver and inhibiting the deposition of silver, so that the plating layer is not uniform, and therefore, the mass ratio of the complexing agent a to the complexing agent B is controlled within the requirements of the invention.
Comparative example 17 differs from example 1 only in that complexing agent B is replaced by glycine of equal mass. The experimental data in table 3 show that the complexing effect of the replaced complexing agent B is poor, which proves that glycine cannot replace the complexing agent B of the present application, and specifically, the complexing agent B defined in the present application is a glycine derivative containing hydroxyl groups and benzene rings, and can act synergistically with the complexing agent a, thereby having a better complexing effect.
The difference between the comparative example 18 and the example 1 is only that the adhesion stabilizer is replaced by acrylic acid with equal mass, and the experimental data in table 3 shows that the replaced adhesion stabilizer has poor effect, which proves that the acrylic acid cannot replace the adhesion stabilizer of the present application, and specifically, the adhesion stabilizer defined in the present application is an acrylic acid derivative containing a ring-shaped functional group, which can cooperate with a composite complexing agent to improve the adhesion of the silver layer and promote the generation of a desired crystal structure and a better silver surface appearance.
The comparative example 19 is different from the example 1 only in that the silver ion stabilizer is replaced by 1, 3-propanedithiol with equal mass, and the experimental data in the table 3 show that the replaced silver ion stabilizer has poor effect, and the 1, 3-propanedithiol can not replace the silver ion stabilizer in the application, specifically, the silver ion stabilizer defined in the application is an acrylic acid derivative containing a benzene ring functional group, can cooperate with a soluble silver ion compound and a compound complexing agent to control the silver ion concentration, stabilize the chemical silver plating rate, ensure that a silver layer is uniform, flat and compact, and has low surface roughness and insertion loss.
The comparative example 20 is compared by using chemical silvering liquid medicine in the prior art, and experimental data in the table 3 show that the deposition speed of a silver layer formed by using the chemical silvering liquid medicine is higher, the silver layer is more uniform and does not change color, the surface roughness and the insertion loss are low, and the process requirements of a 5G high-frequency circuit board can be met; and the silver layer formed by the chemical silver plating liquid medicine of the comparative example 20 has slow deposition speed, can generate color change, and the surface roughness and the insertion loss can not reach the process requirements of the 5G high-frequency circuit board.
In conclusion, the chemical silver-plating liquid medicine for the 5G high-frequency circuit board is applied to the chemical silver-plating process for processing the surface of the circuit board, and the chemical silver-plating liquid medicine contains active ingredients such as a soluble silver ion compound, a composite complexing agent, an attachment stabilizer, a silver ion stabilizer, a discoloration inhibitor, a wetting agent and the like; the chemical silver plating liquid medicine is stable, does not generate precipitate, is simple to operate and maintain as a single component, and can be continuously used by adding and supplementing; the chemical silver plating speed is high, and the thickness of the silver layer can reach 0.6um after silver is deposited for 2 minutes. The chemical silver plating method is cyanide-free operation and has the advantage of environmental protection; after the circuit board is chemically silvered, the production requirement of a 5G high-frequency circuit board is met, and the appearance of the chemical silvered layer is a uniform white semi-bright silver layer, is smooth and compact, and has low surface roughness and insertion loss.
In the above embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes performed by the present specification and drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. The chemical silver plating liquid medicine for the 5G high-frequency circuit board is characterized by comprising the following components in parts by mass:
1.0-4.0% of soluble silver ion compound;
0.8-3.0% of composite complexing agent;
0.2 to 2.0 percent of attachment stabilizer;
0.2 to 2.0 percent of silver ion stabilizer;
0.2 to 2.0 percent of discoloration inhibitor;
0.2 to 2.5 percent of wetting agent;
the balance being solvent;
the composite complexing agent is a mixture of a complexing agent A and a complexing agent B, and the mass ratio of the complexing agent A to the complexing agent B is 1.2-2.0;
the complexing agent A is one or a mixture of more of 5 '-acetamido-2' -carboxyl-4-dimethylamino-2-hydroxybenzophenone and 4 '-acetamido-2' -carboxyl-4-dimethylamino-2-hydroxybenzophenone; the complexing agent B is one or a mixture of more of (S) -3-carboxyl-4-hydroxyphenyl glycine and (R) -3-carboxyl-4-hydroxyphenyl glycine.
2. The electroless silver plating solution for 5G high-frequency circuit boards according to claim 1, wherein the adhesion stabilizer is one or a mixture of 2-thiopheneacrylic acid, 2-furanacrylic acid and 3- (4-pyridyl) acrylic acid.
3. The electroless silver plating solution for 5G high-frequency circuit boards according to claim 1, wherein the silver ion stabilizer is one or a mixture of 1, 2-benzenedithiol, 1, 4-benzenedithiol and m-dibenzylmercaptan.
4. The electroless silver plating solution for 5G high-frequency circuit boards according to claim 1, wherein the discoloration inhibitor is one or a mixture of 1-hydroxycyclopentane carboxylic acid, 3-hydroxyadamantane-1-carboxylic acid and trans-4-hydroxycyclohexane carboxylic acid.
5. The electroless silver plating solution for 5G high-frequency circuit boards according to claim 1, wherein the wetting agent is one or a mixture of more of cyclohexylsulfamic acid, 3-aminopropane sulfonic acid and 2, 4-diaminobenzene sulfonic acid.
6. The electroless silver plating solution for 5G high-frequency circuit boards according to claim 1, wherein the soluble silver ion compound is one or a mixture of silver nitrate, silver citrate and silver phosphate.
7. The electroless silver plating solution for 5G high-frequency circuit boards according to claim 1, wherein the solvent is water.
8. The chemical silvering solution for the 5G high-frequency circuit board according to claim 1, which comprises the following components in percentage by mass:
2.0 percent of soluble silver ion compound;
2.0 percent of composite complexing agent;
1.0% of an adhesion stabilizer;
1.0% of silver ion stabilizer;
1.0% of a discoloration inhibitor;
1.0% of wetting agent;
the balance being solvent.
9. The preparation method of the chemical silver plating liquid medicine for the 5G high-frequency circuit board according to any one of claims 1 to 8, characterized in that the chemical silver plating liquid medicine for the 5G high-frequency circuit board is obtained by stirring and mixing a soluble silver ion compound, a composite complexing agent, an attachment stabilizer, a silver ion stabilizer, a discoloration inhibitor, a wetting agent and the balance of a solvent.
10. A chemical silver plating method of a circuit board is characterized in that the 5G high-frequency circuit board according to any one of claims 1 to 8 is subjected to chemical silver plating by using chemical silver plating chemical; the technological parameters of the chemical silver plating are as follows: the temperature is 40-50 deg.C, and the time is 2-20min.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006316315A (en) * | 2005-05-12 | 2006-11-24 | Ishihara Chem Co Ltd | Displacement-silver-plating bath |
| US20100116168A1 (en) * | 2006-11-16 | 2010-05-13 | Kin Kwok Daniel Chan | Alkalescent Chemical Silver Plating Solution |
| CN110484901A (en) * | 2018-05-15 | 2019-11-22 | 上海新阳半导体材料股份有限公司 | A kind of chemical plating liquid, preparation method and application |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006316315A (en) * | 2005-05-12 | 2006-11-24 | Ishihara Chem Co Ltd | Displacement-silver-plating bath |
| US20100116168A1 (en) * | 2006-11-16 | 2010-05-13 | Kin Kwok Daniel Chan | Alkalescent Chemical Silver Plating Solution |
| CN110484901A (en) * | 2018-05-15 | 2019-11-22 | 上海新阳半导体材料股份有限公司 | A kind of chemical plating liquid, preparation method and application |
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