CN109338343B - Chemical silver plating solution and silver plating method - Google Patents
Chemical silver plating solution and silver plating method Download PDFInfo
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- CN109338343B CN109338343B CN201811126950.3A CN201811126950A CN109338343B CN 109338343 B CN109338343 B CN 109338343B CN 201811126950 A CN201811126950 A CN 201811126950A CN 109338343 B CN109338343 B CN 109338343B
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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
Abstract
The invention provides a chemical silver plating solution on a printed circuit board and a silver plating method, wherein the chemical silver plating solution comprises the following components: 1.0-2.0 g/L of silver ions, 5-30 g/L of a copper ion complexing agent, 0.5-1.8 g/L of a bis-thiazole compound, 0.5-1.5 g/L of a nitrogen-containing heteroandole compound, 0.05-0.075 g/L of benzotriazole, 40-60 ml/L of methane sulfonic acid, 0.5-1.3 g/L of polybenzimidazole imine, and a proper pH value of the plating solution is 0.5-1, and the plating solution can be prepared at normal temperature. The chemical silver plating solution can obtain bright white silver plating layer, especially has outstanding binding force and corrosion resistance, shortens the process flow, does not need pre-plating, and can improve the reliability and prolong the service life of the circuit board.
Description
Technical Field
The invention belongs to the technical field of chemical silver plating, and particularly relates to chemical silver plating solution for surface treatment on a printed circuit board and a silver plating method of the chemical silver plating solution.
Background
The packaging carrier plate and other printed circuit board surface treatment processes are chemically silver-dipped, and have the advantages of good smoothness, good weldability, good plating solution stability, good oxidation resistance, good light stability, good heat resistance and good long-term stability. Silver has excellent conductivity, and has a small atomic diffusivity and is relatively economical compared with a metallographic phase.
With the rapid update of electronic products, the requirements for printed circuit boards are increasing, and the printed circuit boards are developing towards larger information carrying capacity, smaller size and lighter level, so the requirements for surface treatment technology are also increasing. Compared with an organic solderability protection film (OSP), a hot air leveling process (HASL), chemical tin (ImSn), direct gold (DIG), Electroless Nickel Immersion Gold (ENIG) and nickel palladium gold (ENEPIG), the chemical immersion silver (ImAg) has obvious advantages, is low in cost and economy compared with chemical gold plating, has no atomic interaction force generated between tin and copper of chemical tin, forms an intercompound, has excellent conductivity, and is incomparable to OSP. Compared with other surface treatment technologies, the chemical silver is developed later, the process technology is not mature enough, the silver plating comprises chemical silver plating and electroplating silver, and comprehensively, the chemical silver has the advantages of good compactness of a silver layer, simple equipment and lower cost, the method is suitable for the current environmental protection ecological civilization concept process production requirements, silver plating is divided into acid silver plating and alkaline silver plating from acid-base, the alkaline silver plating generally adopts electroplating, the service life of a silver tank is short, the stability is low, the acid system silver plating generally adopts chemical plating, the silver potential has a more correct potential relative to copper, the silver deposition speed is high, and a faster silver layer can be obtained without adding a reducing agent, however, due to the unstable bonding force of the silver layer, even 'black silver' appears and the stability of the plating solution becomes several problems faced by chemical silver.
In the modern technology, a silver plating solution ammonium citrate system described in patent ZL201310312530.5 can be cited as the chemical silver plating solution, the pH value of the chemical silver plating solution is 8.2-10.2, the chemical silver plating solution is alkalescent to alkalescent, although a certain stability can be achieved, the chemical silver plating solution cannot be used for a long time, and the obtained silver layer is not bright enough in metallic luster.
Patent ZL201310312530.1 uses lanthanum oxide and ceric sulfate as additives to solve the problem of plating leakage, but the ion pollution degree is higher and the stability of the plating solution is not high.
The silver plating solution described in patent zl201210270962.x is composed of silver nitrate, succinimide, tartaric acid, triethanolamine, methanesulfonic acid and water. However, since tartaric acid has reducing properties, the silver layer obtained is bright, but the bath is stable.
Disclosure of Invention
In view of the above problems, a first object of the present invention is to provide an electroless silver plating solution which can be applied to industrial production, and which has the advantages of good stability, low ionic contamination, effective solution of the "black silver problem", and the like.
The chemical silver plating solution comprises the following raw materials in concentration: 1.0-2.0 g/L of silver ions, 5-30 g/L of copper ion complexing agent, 0.5-1.8 g/L of bis-thiazole compound, 0.5-1.5 g/L of nitrogen-containing heteroandole compound, 0.05-0.075 g/L of benzotriazole, 40-60 ml/L of methane sulfonic acid and 0.5-1.3 g/L of poly-tetramethylbenzimide.
Preferably, the electroless silver plating solution comprises the following raw materials in concentration: 1.2-1.8 g/L of silver ions, 5-20 g/L of copper ion complexing agent, 0.5-1.5 g/L of bis-thiazole compound, 0.5-1.5 g/L of nitrogen-containing heteroandole compound, 0.05-0.075 g/L of benzotriazole, 45-55 ml/L of methane sulfonic acid and 0.5-1.0 g/L of poly-tetramethylbenzimide.
In the electroless silver plating solution, the bis-thiazole compound may be selected from pyrrolo [2, 3-d: 5,4-d ' ] bis thiazole, 2' -diamino-4, 4' -bis thiazole and derivatives thereof, at least one of phenylphosphonic acid bis thiazole; preferably, the bis-thiazole compound is selected from the group consisting of pyrrolo [2, 3-d: 5,4-d' ] bisthiazole.
Wherein, in the chemical silver plating solution, the azaindole-containing compound can be at least one selected from dibenzopyrrolo [1,2-a ] [1,8] naphthyridine, 2 amino- (4-azaindolyl) -4-methylthiazoline and 3- (1-arylsulfonyl alkyl) -7-azaindole compounds; preferably, the azaindole-containing compound is selected from dibenzopyrrolo [1,2-a ] [1,8] naphthyridine.
In the chemical silver plating solution, the silver ions are introduced in the form of a silver compound, and the silver compound can be silver oxide and/or silver nitrate.
In the electroless silver plating solution, the copper ion complexing agent is at least one selected from the group consisting of EDTA (ethylenediaminetetraacetic acid) and salts thereof, DTPA (diethyltriaminepentaacetic acid) and salts thereof, NTA (nitrilotriacetic acid) and salts thereof, and IDS (iminodisuccinic acid sodium salt). Preferably, the copper ion complexing agent is selected from EDTA-2 Na.
Wherein, in the chemical silver plating solution, the pH value of the chemical silver plating solution is between 0.5 and 1, for example, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0.
Wherein the chemical silver plating solution also contains an emulsifier OP-10, and the concentration of the emulsifier OP-10 is 2-10 ml/L.
The second purpose of the invention is to provide a silver plating method, which comprises the step of carrying out chemical silver plating on a printed circuit board in the chemical silver plating solution.
The silver plating method specifically comprises the following steps: pre-microetching, alkaline degreasing, post-microetching and chemical silvering treatment. Preferably, the treated printed wiring board is washed with water, for example, deionized water, three times after the completion of the steps.
Wherein, the treatment processes of pre-microetching, alkaline degreasing and post-microetching are conventional operations in the field; preferably, the operation of pre-microetching comprises: and soaking the printed circuit board in a solution containing hydrogen peroxide and sulfuric acid for 80-100 seconds. Preferably, the operation of alkaline degreasing comprises: and immersing the printed circuit board subjected to the pre-microetching treatment in a sodium hydroxide solution for 80-100 seconds. Preferably, the operation of post-microetching comprises: and (3) immersing the printed circuit board subjected to alkaline degreasing treatment in a sulfuric acid solution for 80-100 seconds.
Preferably, the electroless silver plating process comprises: and (3) immersing the printed circuit board subjected to the micro-etching treatment into the chemical silver plating solution at normal temperature (for example, 20-30 ℃), and soaking. For example, the soaking time is adjusted according to the required coating thickness, such as soaking for 2 minutes (the coating thickness can reach 0.2 micron within 2 minutes), 3 minutes and 4 minutes.
The invention has the beneficial effects that:
1) and (3) stabilizing the plating solution: according to the invention, a copper ion complexing agent is added to prevent the influence of copper ions on the reaction, and the stability and the service life of the plating solution can be enhanced (the stability can reach 6MTO) by using a light stabilizer benzotriazole.
2) The plating layer has good binding force: the invention uses the surfactant poly tetra acetyl diphenyl imine to improve the complex compound generated by silver and the surfactant and spread on the surface of the printed circuit board similarly to a film to promote the organic framework of the silver layer to form so as to improve the binding force, the 3M adhesive tape is tightly stuck on the surface of a sample to be tested at 90 degrees, the adhesive tape is quickly torn to avoid the phenomena of metal powder falling and adhesive of a patch tape, metal coating peeling, severe cracking and peeling after the substrate is not broken, and the metal of the lower layer is not exposed when the substrate is not broken.
3) The galvanic effect and silver electron migration phenomena are less, the silver plating time can be controlled, the requirement on the thickness of a plating layer is met, the plating layer thickness is reduced as much as possible within the weldability range, and the phenomena are greatly improved.
4) The invention improves the phenomena of instability and bonding force peeling of the traditional plating solution, reduces the preplating step in the traditional procedure and is suitable for industrial production.
The fast silver plating solution provided by the invention has good stability and fast plating speed which can reach 0.2 micron within 2 minutes, and the silver plating solution has white appearance, bright color and good weldability, and can meet the requirement of silver plating thickness of most products in chemical silver process.
Detailed Description
The invention provides an electroless silver plating solution, which comprises the following raw materials in concentration: 1.0-2.0 g/L of silver ions, 5-30 g/L of copper ion complexing agent, 0.5-1.8 g/L of bis-thiazole compound, 0.5-1.5 g/L of nitrogen-containing heteroandole compound, 0.05-0.075 g/L of benzotriazole, 40-60 ml/L of methane sulfonic acid and 0.5-1.3 g/L of poly-tetramethylbenzimide.
Preferably, the electroless silver plating solution comprises the following raw materials in concentration: 1.2-1.8 g/L of silver ions, 5-20 g/L of copper ion complexing agent, 0.5-1.5 g/L of bis-thiazole compound, 0.5-1.5 g/L of nitrogen-containing heteroandole compound, 0.05-0.075 g/L of benzotriazole, 45-55 ml/L of methane sulfonic acid and 0.5-1.0 g/L of poly-tetramethylbenzimide.
In the electroless silver plating solution, the bis-thiazole compound may be selected from pyrrolo [2, 3-d: 5,4-d ' ] bis thiazole, 2' -diamino-4, 4' -bis thiazole and derivatives thereof, at least one of phenylphosphonic acid bis thiazole; preferably, the bis-thiazole compound is selected from the group consisting of pyrrolo [2, 3-d: 5,4-d' ] bisthiazole.
Wherein, in the chemical silver plating solution, the azaindole-containing compound can be at least one selected from dibenzopyrrolo [1,2-a ] [1,8] naphthyridine, 2 amino- (4-azaindolyl) -4-methylthiazoline and 3- (1-arylsulfonyl alkyl) -7-azaindole compounds; preferably, the azaindole-containing compound is selected from dibenzopyrrolo [1,2-a ] [1,8] naphthyridine.
In the chemical silver plating solution, the silver ions are introduced in the form of a silver compound, and the silver compound can be silver oxide and/or silver nitrate. If the concentration of the silver ions is too low, the deposition speed is too low, the production influence is large, and the suitable concentration optimization brings the best economic benefit for production.
In the electroless silver plating solution, the copper ion complexing agent is at least one selected from the group consisting of EDTA (ethylenediaminetetraacetic acid) and salts thereof, DTPA (diethyltriaminepentaacetic acid) and salts thereof, NTA (nitrilotriacetic acid) and salts thereof, and IDS (iminodisuccinic acid sodium salt). Preferably, the copper ion complexing agent is selected from EDTA-2 Na.
Wherein, in the chemical silver plating solution, the pH value of the chemical silver plating solution is between 0.5 and 1, for example, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0.
Wherein the chemical silver plating solution also contains an emulsifier OP-10, and the concentration of the emulsifier OP-10 is 2-10 ml/L.
The copper ion complexing agent is intended to reduce the copper ion concentration, thereby making the reduction-rate of silver constantly stable. The dibenzopyrrolo [1,2-a ] [1,8] naphthyridine azanaphthalene-containing compound is used as an auxiliary coordination agent of silver and has the effect of enabling a silver layer to be compact. Pyrrolo [2, 3-d: 5,4-d' ] bis-thiazole and compounds containing bis-thiazole are favorable for being adsorbed on the surface of copper to form an organic framework, thereby obtaining better binding force. Methane sulfonic acid and lithium acetate have the function of transferring protons, so that silver ions can be transported quickly, and the process time is shortened. The polybenzoylbenzimide is mainly used for preventing metal deposition and is used for forming an organic framework to improve the binding force.
The principle of the plating solution of the invention is as follows: cu +2Ag+＝2Ag+Cu2+The most basic chemical principle of the electroless plating solution in the reaction is a displacement reaction essentially, but in the actual production process of chemical silver, the inventor considers the Javanni effect, silver electron migration phenomenon, ion pollution degree, plating layer thickness and various industrial indexes of plating solution stability and weldability, and adds methane sulfonic acid and lithium acetate to provide an acidic environment with strong acid pH value of 0.5-1 and improve reaction rate so as to overcome the corrosion problem of alkaline environment to equipment, the additive mainly aims to form a plating layer framework to be beneficial to improving the bonding force of the plating layer, and the additive mainly comprises dibenzopyrrolo [1,2-a ]][1,8]Naphthyridine with pyrrolo [2, 3-d: 5,4-d']Bis-thiazoles and poly-pyromellitic dibenzimides, the surfactant poly-pyromellitic dibenzimides first preferentially adsorb on copper surfaces, hindering metal deposition, andpyrrolo [2, 3-d: 5,4-d']Bithiazoles form a competitive adsorption, since the surfactant is an adsorption-desorption process, once the copper ions are exposed, pyrrolo [2, 3-d: 5,4-d']The bithiazole is adsorbed on the copper surface to form an organic framework, the methane sulfonic acid is used as a negative ion to transfer protons, and the silver is deposited in the lattice, namely dibenzo-pyrrolo [1,2-a ]][1,8]The naphthyridine adsorbs to the silver and forms a chemical bond with the silver, rendering the silver fine, at which time the surfactant polybenzoylbenzimide re-reacts with dibenzopyrrolo [1,2-a ] benzene][1,8]The naphthyridine competitively adsorbs, so that the silver and the pyromellitic dianhydride coordinate, have an important impedance effect on electrochemical migration corrosion, and have better corrosion resistance under the condition of meeting the process conditions.
The invention also provides a silver plating method, which comprises the step of carrying out chemical silver plating on the printed circuit board in the chemical silver plating solution.
The silver plating method specifically comprises the following steps: pre-microetching, alkaline degreasing, post-microetching and chemical silvering treatment. Preferably, the treated printed wiring board is washed with water, for example, deionized water, three times after the completion of the steps.
Wherein, the treatment processes of pre-microetching, alkaline degreasing and post-microetching are conventional operations in the field; preferably, the operation of pre-microetching comprises: and soaking the printed circuit board in a solution containing hydrogen peroxide and sulfuric acid for 80-100 seconds. Preferably, the operation of alkaline degreasing comprises: and immersing the printed circuit board subjected to the pre-microetching treatment in a sodium hydroxide solution for 80-100 seconds. Preferably, the operation of post-microetching comprises: and (3) immersing the printed circuit board subjected to alkaline degreasing treatment in a sulfuric acid solution for 80-100 seconds.
Preferably, the electroless silver plating process comprises: and (3) immersing the printed circuit board subjected to the micro-etching treatment into the chemical silver plating solution at normal temperature (for example, 20-30 ℃), and soaking. For example, the soaking time is adjusted according to the required coating thickness, such as soaking for 2 minutes (the coating thickness can reach 0.2 micron within 2 minutes), 3 minutes and 4 minutes.
The rapid silver plating solution provided by the invention has good stability and high plating speed which can reach 0.2 micron within 2 minutes, and the plating layer of the rapid silver plating solution provided by the invention has white appearance, bright color and good weldability, and can meet the requirement of silver plating thickness of most products in chemical silver process.
The technical solution of the present invention will be further described in detail with reference to specific embodiments. The following examples are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of the invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.
Unless otherwise indicated, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.
The silver metal surface layer obtained on the printed circuit board is obtained by the following method (microetching and alkaline degreasing in the process are produced by the Olski company in Yiyang city):
carrying out pre-microetching (the pre-microetching solution comprises hydrogen peroxide and sulfuric acid solution for 90 seconds), washing with deionized water for three times, alkaline degreasing (sodium hydroxide solution for 90 seconds), washing with deionized water for three times, carrying out post-microetching (sulfuric acid solution for 90 seconds), washing with deionized water for three times, plating bath silver plating (2 minutes), washing with deionized water for three times, drying, sealing and storing.
Wherein the silver plating solution adopts the silver plating solution provided in the embodiment.
Example 1
The chemical silver plating solution comprises: 1.2g/L of silver oxide; copper ion complexing agent EDTA-2Na5 g/L; pyrrolo [2, 3-d: 0.5g/L of 5,4-d' ] bisthiazole; 0.05g/L of benzotriazole; 0.5g/L of polybenzoylbenzimide; 1.2g/L of dibenzopyrrolo [1,2-a ] [1,8] naphthyridine; methane sulfonic acid 50 ml/L.
The silver layer obtained under the parameters is flat and bright in appearance, no excessive plating is carried out on the circuit, the circuit is not blackened, the plating thickness is 0.2 micrometer (2min plating thickness), the bath solution stability reaches 6MTO, the bonding force of the plating tested by a tape method reaches grade 5(5 represents excellent, 4 represents excellent, 3 represents poor, 2 represents poor, 1 represents very poor), the metal plating layer does not peel off, the substrate is not broken and can not have serious cracking and peeling after being bent, the substrate is not broken, the metal at the lower layer is not exposed, the solution is clear and transparent, the carbon content of the plating layer is lower than 0.3 percent, the plating layer has good weldability grade 5(5 represents excellent weldability, 4 represents good weldability, 3 represents poor weldability, 2 represents poor weldability, 1 represents very poor weldability) and the silver ion migration phenomenon grade 5(5 represents no migration phenomenon, 4 for mild migration, 3 for moderate migration, 2 for heavy migration, 1 for severe migration).
Example 2
The electroless silver plating solution comprises the following raw materials in concentration: 1.8g/L of silver oxide; copper ion complexing agent EDTA-2Na20 g/L; pyrrolo [2, 3-d: 1.5g/L of 5,4-d' ] bisthiazole; 1.2g/L of dibenzopyrrolo [1,2-a ] [1,8] naphthyridine; 0.075g/L of benzotriazole; 50ml/L of methane sulfonic acid; 1.0g/L of polybenzoylbenzimide.
Example 3
The electroless silver plating solution comprises the following raw materials in concentration: 1.8g/L of silver oxide; copper ion complexing agent EDTA-2Na15 g/L; pyrrolo [2, 3-d: 1.2g/L of 5,4-d' ] bisthiazole; 1.5g/L of dibenzopyrrolo [1,2-a ] [1,8] naphthyridine; 0.06g/L of benzotriazole; 55ml/L of methane sulfonic acid; 0.75g/L of polybenzoylbenzimide.
Example 4
The electroless silver plating solution comprises the following raw materials in concentration: 1.0g/L silver nitrate; copper ion complexing agent DTPA10 g/L; 1.0g/L of 2, 2 '-diamino-4, 4' -bithiazole; 2 amino- (4-azaindolyl) -4-methylthiazoline 1.0 g/L; 0.07g/L of benzotriazole; 40ml/L of methane sulfonic acid; 1.2g/L of polybenzoylbenzimide.
Example 5
The electroless silver plating solution comprises the following raw materials in concentration: 1.5g/L of silver oxide; copper ion complexing agent EDTA-2Na25 g/L; 0.8g/L of 2, 2 '-diamino-4, 4' -bithiazole; 0.5g/L of dibenzopyrrolo [1,2-a ] [1,8] naphthyridine; 0.065g/L of benzotriazole; 45ml/L of methane sulfonic acid; 1.3g/L of polybenzoylbenzimide.
Example 6
The electroless silver plating solution comprises the following raw materials in concentration: 2.0g/L silver nitrate; copper ion complexing agent IDS30 g/L; 1.8g/L of 2, 2 '-diamino-4, 4' -bithiazole; 0.5g/L of dibenzopyrrolo [1,2-a ] [1,8] naphthyridine; 0.07g/L of benzotriazole; methane sulfonic acid 60 ml/L; 1.1g/L of polybenzoylbenzimide.
Comparative example 1
The silver plating solution comprises: 1.2g/L of silver oxide; copper ion complexing agent EDTA-2Na5 g/L; 0.5g/L of pyrrolothiazole; 0.5g/L of dibenzopyrrole; 50ml/L of methane sulfonic acid; 0.05g/L of benzotriazole; 0.5g/L of polybenzoylbenzimide.
The silver layer obtained under the parameters is bluish white in appearance, no excessive plating is generated on the circuit, the circuit is blackened, the plating thickness is 0.14 mu inch (2min plating thickness), the bath solution stability is 5MTO, the plating bonding force tested by a tape method is poor in grade 2(3M tape tests show that no metal plating layer peels off, the substrate is not broken and has severe cracking and peeling after being bent, and the underlying metal is exposed when the substrate is not broken), the solution is clear and transparent, the weldability poor grade after aging is 2, the silver ion migration phenomenon is heavier grade 2, and the carbon content of the plating layer is lower than 3%.
Compared with the comparative example 1, the plating solution of the embodiment 1 has the advantages of excellent stability, bright plating layer, no overflowed plating on the circuit, no blackening of the circuit, excellent binding force, excellent weldability and no silver ion electromigration phenomenon. The compound containing the bithiazole and azaindole compounds has excellent performance of improving the coating, and the binding force of the coating tested by a tape method is better (3M tape test has no phenomenon of peeling off a metal coating, no phenomenon of severe cracking and peeling after bending when a substrate is not broken, and no phenomenon of exposing the metal at the lower layer when the substrate is not broken).
Comparative example 2
The silver plating solution comprises: 1.2g/L of silver oxide; copper ion complexing agent EDTA-2Na5 g/L; 0.5g/L of phenyl phosphonic acid thiazole; 0.5g/L of pyrroloindole; 50ml/L of methane sulfonic acid; 0.05g/L of benzotriazole; 0.5g/L of polybenzoylbenzimide.
The silver layer obtained under the parameters is white in appearance, no excessive plating exists on the circuit, the circuit is black, the plating thickness is 0.16 mu inch (2min plating thickness), the bath solution stability is 5MTO, the tape method is used for testing the plating bonding force level 2(3M tape is used for testing the phenomenon that a metal plating layer peels off, the phenomenon that the metal plating layer does not crack or peel after the substrate is not broken, and the phenomenon that the metal of the lower layer is exposed when the substrate is not broken), the solution is clear and transparent, the weldability level is 3 after aging, the silver ion migration phenomenon is serious level 1, and the carbon content of the plating layer is lower than 3%.
Compared with the comparative example 2, the plating solution of the embodiment 1 has the advantages of excellent stability, bright plating layer, no overflowed plating on the circuit, no blackening of the circuit, excellent binding force, excellent weldability and no silver ion electromigration phenomenon. The compound containing the bithiazole and azaindole compounds has excellent performance of improving the plating layer, the bonding force of the plating layer is good when tested by a tape method (3M tape test has the advantages of slight peeling of a metal plating layer, no serious cracking and peeling after the substrate is not broken, no phenomenon of exposing the metal at the lower layer when the substrate is not broken), the solution is clear and transparent, the weldability is good after aging, and no silver ion migration phenomenon plays a significant role in the stability of the plating solution
Comparative example 3
The silver plating solution comprises: 1.2g/L of silver oxide; copper ion complexing agent EDTA-2Na5 g/L; 0.5g/L of phenyl phosphonic acid bithiazole; 0.5g/L of pyrroloindole; 50ml/L of methane sulfonic acid; 0.05g/L of benzotriazole; 0.5g/L of polybenzoylbenzimide.
The silver layer obtained under the parameters is white in appearance, no excessive plating exists on the circuit, the circuit does not blacken, the plating thickness is 0.18 mu inch (2min plating thickness), the bath solution stability is 5MTO, the general level of the bonding force of the plating tested by a tape method is 3(3M tape tests show that the metal plating is slightly peeled off, the substrate is not broken, no serious crack and peeling occur after bending, and the metal of the lower layer is slightly exposed after the substrate is not broken), the solution is clear and transparent, the weldability is poor at level 3 after aging, the silver ion migration phenomenon is slight at level 4, and the carbon content of the plating is lower than 3%.
Compared with the comparative example 3, the plating solution of the embodiment 1 has the advantages of excellent stability, bright plating layer, no overflowed plating on the circuit, no blackening of the circuit, excellent binding force, excellent weldability and no silver ion electromigration phenomenon. The compound containing the bithiazole and azaindole compounds has excellent performance of improving the coating, the binding force of the coating tested by a tape method is good (3M tape test has the advantages of slight peeling of a metal coating, no serious cracking and peeling after bending when a substrate is not broken, and no phenomenon of exposing metal at the lower layer when the substrate is not broken), the solution is clear and transparent, the weldability is good after aging, and no silver ion migration phenomenon plays a significant role in the stability of the plating solution.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (11)
1. The chemical silver plating solution is characterized by comprising the following raw materials in concentration: 1.0-2.0 g/L of silver ions, 5-30 g/L of copper ion complexing agent, 0.5-1.8 g/L of bis-thiazole compound, 0.5-1.5 g/L of nitrogen-containing heteroandole compound, 0.05-0.075 g/L of benzotriazole, 40-60 ml/L of methane sulfonic acid and 0.5-1.3 g/L of poly-tetramethylbenzimide;
the bis-thiazole compound is selected from pyrrolo [2, 3-d: 5,4-d ' ] bis thiazole, 2' -diamino-4, 4' -bis thiazole and derivatives thereof, at least one of phenylphosphonic acid bis thiazole;
the azaindole-containing compound is at least one selected from dibenzopyrrolo [1,2-a ] [1,8] naphthyridine, 2 amino- (4-azaindolyl) -4-methylthiazoline and 3- (1-arylsulfonyl alkyl) -7-azaindole compounds.
2. The electroless silver plating solution according to claim 1, wherein the electroless silver plating solution comprises the following raw materials in concentration: 1.2-1.8 g/L of silver ions, 5-20 g/L of copper ion complexing agent, 0.5-1.5 g/L of bis-thiazole compound, 0.5-1.5 g/L of nitrogen-containing heteroandole compound, 0.05-0.075 g/L of benzotriazole, 45-55 ml/L of methane sulfonic acid and 0.5-1.0 g/L of poly-tetramethylbenzimide.
3. The electroless silver plating solution according to claim 1 or 2, wherein the bis-thiazole compound is selected from the group consisting of pyrrolo [2, 3-d: 5,4-d' ] bisthiazole.
4. The electroless silver plating solution of claim 1 or 2, wherein the azaindole-containing compound is selected from dibenzopyrrolo [1,2-a ] [1,8] naphthyridine.
5. The electroless silver plating solution according to claim 1 or 2, wherein the silver ions are introduced in the form of a silver compound, the silver compound being silver oxide and/or silver nitrate.
6. The electroless silver plating solution according to claim 1 or 2, wherein the copper ion complexing agent is selected from at least one of EDTA (ethylene diamine tetraacetic acid) and salts thereof, DTPA (diethyltriaminepentaacetic acid) and salts thereof, NTA (nitrilotriacetic acid) and salts thereof, and IDS (iminodisuccinic acid sodium salt).
7. The electroless silver plating solution according to claim 1 or 2, wherein the pH of the electroless silver plating solution is between 0.5 and 1.
8. The electroless silver plating solution according to claim 1 or 2, further comprising an emulsifier OP-10, wherein the concentration of the emulsifier OP-10 is 2 to 10 ml/L.
9. A silver plating method comprising subjecting a printed wiring board to electroless silver plating in the electroless silver plating solution according to any one of claims 1 to 8.
10. A method of silver plating according to claim 9, characterized in that it comprises in particular the steps of: pre-microetching, alkaline degreasing, post-microetching and chemical silvering treatment.
11. The silver plating method according to claim 9, wherein the electroless silver plating process comprises:
and (3) immersing the printed circuit board subjected to the micro-etching treatment into the chemical silver plating solution at normal temperature, and soaking.
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| CN115595567B (en) * | 2022-08-30 | 2023-09-22 | 胜宏科技（惠州）股份有限公司 | Anti-discoloration chemical silver plating solution |
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| CN102605360B (en) * | 2011-10-12 | 2014-11-12 | 常州大学 | Chemical silvering solution based on imidazolium ionic liquid and silvering method |
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