CN115558912A - Environment-friendly chemical reduction gold liquid and process thereof - Google Patents

Environment-friendly chemical reduction gold liquid and process thereof Download PDF

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Publication number
CN115558912A
CN115558912A CN202211395848.XA CN202211395848A CN115558912A CN 115558912 A CN115558912 A CN 115558912A CN 202211395848 A CN202211395848 A CN 202211395848A CN 115558912 A CN115558912 A CN 115558912A
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gold
nickel
chemical reduction
gold liquid
concentration
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姚玉
姚吉豪
王江锋
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Shenzhen Chuangzhi Xinlian Technology Co ltd
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Shenzhen Chuangzhi Xinlian Technology Co ltd
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    • CCHEMISTRY; METALLURGY
    • C23COATING 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
    • C23CCOATING 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
    • C23C18/00Chemical 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
    • C23C18/16Chemical 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
    • C23C18/31Coating with metals
    • C23C18/42Coating with noble metals
    • C23C18/44Coating with noble metals using reducing agents
    • CCHEMISTRY; METALLURGY
    • C23COATING 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
    • C23CCOATING 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
    • C23C18/00Chemical 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
    • C23C18/16Chemical 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
    • C23C18/1601Process or apparatus
    • C23C18/1603Process or apparatus coating on selected surface areas
    • C23C18/1605Process or apparatus coating on selected surface areas by masking
    • CCHEMISTRY; METALLURGY
    • C23COATING 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
    • C23CCOATING 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
    • C23C18/00Chemical 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
    • C23C18/16Chemical 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
    • C23C18/1601Process or apparatus
    • C23C18/1633Process of electroless plating
    • C23C18/1646Characteristics of the product obtained
    • C23C18/165Multilayered product
    • C23C18/1651Two or more layers only obtained by electroless plating
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05KPRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00Apparatus or processes for manufacturing printed circuits
    • H05K3/10Apparatus 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
    • H05K3/18Apparatus 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
    • H05K3/181Apparatus 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
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00Technologies related to metal processing
    • Y02P10/20Recycling

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  • Engineering & Computer Science (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Chemically Coating (AREA)

Abstract

The invention relates to the technical field of semiconductor manufacturing, in particular to an environment-friendly chemical reduction gold liquid and a process thereof, wherein the environment-friendly chemical reduction gold liquid comprises a gold source of aurous thiocyanate and a composite reducing agent of ammonium thiocyanate and an auxiliary reducing agent; the concentration of the aurous thiocyanate salt in the chemical reduction gold liquid is 1.5g/L-2.5g/L; the concentration of ammonium thiocyanate in the chemical reduction gold liquid is 10g/L-20g/L; and a complexing agent, a pH buffer and an adjuvant. The chemical reduction gold liquid is adopted to ensure that the coating has better brightness and uniformity and better microcosmic appearance, and also solves the problem that the gold-changing liquid is excessively corroded to generate serious nickel corrosion, thus influencing the phenomenon that parts fall off or the interface of soldering tin and a welding pad is cracked after welding, and ensuring that the gold layer and the nickel layer have better bonding capability.

Description

Environment-friendly chemical reduction gold liquid and process thereof
Technical Field
The invention relates to the technical field of semiconductor manufacturing, in particular to an environment-friendly chemical reduction gold liquid and a process thereof.
Background
The gold plating layer has excellent corrosion resistance, wear resistance, ductility, and plasticity. With the development of science and technology, the performances of high conductivity, good welding performance, low contact resistance, hot-press bonding and the like are further developed and utilized. Making it an essential metal plating for electronic devices, integrated circuits, printed circuit boards, relays, connectors, lead frames, waveguides, etc. In addition, gold plating is also applied to many aerospace airspace and military supplies.
Electroless nickel gold is one of the important ways of surface treatment of printed circuit boards, and is mainly used for high-end boards such as mobile phone boards, automobile machines, communication boards and the like. Generally, electroless nickel-gold is divided into two steps, firstly, a layer of nickel is plated on the surfaces of a mounting part, a terminal and the like of a substrate of a printed circuit board, but the nickel layer is easy to oxidize and can influence the weldability and the welding strength; therefore, a gold layer is required to be plated on the surface of the nickel layer, and the gold layer is generally plated with thin gold (1-3 u') in consideration of cost and functionality. In the formed nickel layer and gold layer composite layer, the nickel layer has an important barrier function on the printed circuit board, and prevents atom migration between the copper layer and the gold layer; meanwhile, the gold layer protects the nickel layer from being oxidized, and has the functions of good welding wettability, aluminum wire bonding capability, conductivity and the like; therefore, after the nickel is plated on the printed circuit board, a layer of gold is plated, and the weldability and the welding strength of the printed circuit board can be effectively improved.
In the electroless gold plating process on the nickel layer, the nickel is excessively corroded by the replacement gold solution, resulting in severe nickel corrosion, commonly referred to as Black Pad (Black Pad), which affects the peeling of the parts after soldering or the cracking of the solder and bonding Pad interface. Therefore, how to prepare the electroless gold plating solution with the performance of preventing the nickel layer from being excessively corroded and good wettability becomes a hot spot for developing the electroless nickel-gold plating solution at present.
Disclosure of Invention
The invention aims to provide the environment-friendly chemical reduction gold liquid which is simple in process and can greatly improve the reliability of welding spots.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: an environment-friendly chemical reduction gold liquid comprises a gold source of aurous thiocyanate salt, and a composite reducing agent of ammonium thiocyanate and an auxiliary reducing agent;
the concentration of the aurous thiocyanate salt in the chemical reduction gold liquid is 1.5g/L-2.5g/L;
the concentration of the ammonium thiocyanate in the chemical reduction gold liquid is 10g/L-20g/L;
and a complexing agent, a pH buffer and an adjuvant.
Furthermore, the auxiliary reducing agent is at least one of formaldehyde, dimethylamine borane, sodium hypophosphite, hydrazine and hydroboron, and the total concentration of the auxiliary reducing agent in the chemical nickel plating solution is 15g/L-40g/L.
Furthermore, the auxiliary reducing agent also comprises at least one of sodium hypophosphite, sodium hypophosphite and potassium dihydrogen phosphate, and the concentration of the auxiliary reducing agent in the chemical reduction gold liquid is 1g/L-5g/L.
Further, the auxiliary agents are polyethylene glycol and polyacrylamide, the concentration of the polyethylene glycol in the chemical reduction gold liquid is 1.5g/L-2g/L, and the concentration of the polyacrylamide in the chemical reduction gold liquid is 0.8g/L-1.5g/L.
Furthermore, one of composite complexing agent aminotrimethylene phosphonic acid, ethylene diamine tetramethylene phosphoric acid and ethylenediamine is adopted, and the concentration of the composite complexing agent in the chemical reduced gold liquid is 10g/L-30g/L.
Further, the pH buffering agent is at least one of ammonia water, disodium hydrogen phosphate, potassium dihydrogen phosphate, boric acid, borax, sodium carbonate and aminoacetic acid, and is used for adjusting the pH value of the chemical reduction gold solution to enable the pH value to be between 1.5 and 3.5.
The process for gold plating by adopting the chemical reduction gold solution comprises the following steps:
the method comprises the following steps: firstly, a circuit is manufactured on a substrate, a metal layer is deposited on the ceramic substrate, and the substrate with the connected circuit is obtained through etching;
step two: forming a mask on the substrate by using photoresist to obtain a substrate to be plated;
step three: plating a palladium layer on the substrate to be plated to obtain a palladium-plated substrate;
step four: carrying out nickel plating on the palladium-plated substrate to obtain a nickel-plated substrate;
step five: carrying out micro-corrosion on the nickel-plated substrate by using an acid solution to form a microporous nickel-plated substrate with a certain pore space;
step six: carrying out gold plating on the microporous nickel-plated substrate by adopting the chemical reduction gold solution to obtain a semi-finished product;
step seven: and removing the covered photoresist and the redundant plating layer to obtain a finished product.
Further, the nickel plating is carried out by adopting a nickel plating solution which comprises 20-40g/L of nickel sulfate, 20-30g/L of sodium hypophosphite, 8-10g/L of trisodium citrate and 0.1-1g/L of additive.
Further, the method also comprises a pretreatment step, wherein the pretreatment step comprises the following steps: degreasing, polishing, acid washing, water washing, drying, ion beam cleaning and preheating.
Further, the additive is a compound of organic sodium salt and polyethylene glycol, and the concentration ratio of the organic sodium salt to the polyethylene glycol is 1:2-1:4.
compared with the prior art, the invention has the advantages and positive effects that:
according to the environment-friendly chemical reduction gold liquid provided by the invention, the aurous thiocyanate is used as a gold source, the ammonium thiocyanate and the auxiliary reducing agent are matched to be used as a composite reducing agent, the gold plating efficiency is further improved, and the free cyanogen released by side reactions such as oxidation-reduction decomposition and the like in the treatment process can be reduced by the aid of the mixed liquid of the aurous thiocyanate and the ammonium thiocyanate, so that the aurous thiocyanate does not have toxicity of a conventional cyanogen-containing formula.
The chemical reduction gold liquid is adopted to ensure that the plating layer has better brightness and uniformity and better microcosmic appearance, and also solves the problem that the phenomenon that parts fall off or the interface of soldering tin and a welding pad is cracked after welding because the gold changing liquid is excessively corroded to generate serious nickel corrosion is also solved. The gold layer and the nickel layer have better bonding capability.
The environment-friendly chemical reduction gold liquid provided by the invention can effectively improve the reliability of welding spots, and solves the problem that the quality and reliability of products cannot meet the requirement of high weldability, so that the environment-friendly chemical reduction gold liquid has a longer service life, and the gold surface can keep excellent welding performance for a long time.
Detailed Description
For a better understanding of the present invention, the present invention is further described below in conjunction with specific embodiments.
In the formed nickel layer and gold layer composite layer, the nickel layer has an important barrier function on the printed circuit board, and prevents atom migration between the copper layer and the gold layer; meanwhile, the gold layer protects the nickel layer from being oxidized, and has the functions of good welding wettability, aluminum wire bonding capability, conductivity and the like; therefore, after the nickel is plated on the printed circuit board, a layer of gold is plated, and the weldability and the welding strength of the printed circuit board can be effectively improved.
In the electroless gold plating process on the nickel layer, the nickel is excessively corroded by the replacing gold liquid, so that severe nickel corrosion is caused, which is commonly called Black Pad (Black Pad) in the industry, and thus the part is separated after welding or the interface between the soldering tin and the soldering Pad is cracked. Therefore, how to prepare an electroless gold plating solution with the performance of preventing the nickel layer from being excessively corroded and good wettability becomes a hot spot for the research and development of the electroless nickel-gold plating solution at present.
Therefore, the environment-friendly chemical reduction gold liquid is simple in process and low in component toxicity, and can solve the problem that the phenomenon that parts fall off after welding or the interface between soldering tin and a welding pad is broken due to excessive corrosion of the gold-replacing liquid medicine.
According to one aspect of the present invention, there is provided an environmentally friendly chemical gold reduction solution, comprising a gold source of aurous thiocyanate, an auxiliary reducing agent and ammonium thiocyanate, wherein the auxiliary reducing agent is a complex reducing agent;
the concentration of the aurous thiocyanate salt in the chemical reduction gold solution is 1.5g/L-2.5g/L;
the concentration of ammonium thiocyanate in the chemical reduction gold liquid is 10g/L-20g/L;
and a complex complexing agent, a pH buffer and an adjuvant.
According to the environment-friendly chemical reduction gold liquid provided by the invention, the aurous thiocyanate is used as a gold source, the ammonium thiocyanate and the auxiliary reducing agent are matched to be used as a composite reducing agent, the gold plating efficiency is further improved, and the free cyanogen released by side reactions such as oxidation-reduction decomposition and the like in the treatment process can be reduced by the aid of the mixed liquid of the aurous thiocyanate and the ammonium thiocyanate, so that the aurous thiocyanate does not have toxicity of a conventional cyanogen-containing formula.
The chemical reduction gold liquid is adopted to ensure that the plating layer has better brightness and uniformity and better microcosmic appearance, and also solves the problem that the phenomenon that parts fall off or the interface of soldering tin and a welding pad is cracked after welding because the gold changing liquid is excessively corroded to generate serious nickel corrosion is also solved. So that the gold layer and the nickel layer have better bonding capability.
The environment-friendly chemical reduction gold liquid provided by the invention can effectively improve the reliability of welding spots, and solves the problem that the quality and reliability of products cannot meet the requirement of high weldability, so that the environment-friendly chemical reduction gold liquid has a longer service life, and the gold surface can keep excellent welding performance for a long time.
Furthermore, the auxiliary reducing agent is at least one of formaldehyde, dimethylamine borane, sodium hypophosphite, hydrazine and hydroboron, and the total concentration of the complexing agent in the chemical nickel plating solution is 15g/L-40g/L.
Furthermore, the auxiliary reducing agent comprises at least one of sodium hypophosphite, sodium hypophosphite and potassium dihydrogen phosphate, and the concentration of the auxiliary reducing agent in the chemical reduction gold liquid is 1g/L-5g/L.
Furthermore, the auxiliary agents are polyethylene glycol and polyacrylamide, the concentration of the polyethylene glycol in the chemical reduced gold liquid is 1.5g/L-2g/L, and the concentration of the polyacrylamide in the chemical reduced gold liquid is 0.8g/L-1.5g/L.
The polyethylene glycol can disperse particles and wet the surfaces of the particles in the gold plating process, so that the particles are in full contact with the base layer, and the byproducts of the reaction can circulate quickly, thereby increasing the reaction chance of the chemically reduced gold solution and the base layer and accelerating the gold plating efficiency.
The polyacrylamide is ionic polyacrylamide, the molecular chain of the polyacrylamide contains a large amount of acylamino, the polyacrylamide has good water solubility and adsorption performance, and can play a certain flocculation role to accelerate the deposition of gold ions.
Furthermore, the concentration of the composite complexing agent in the chemical reduced gold liquid is 10g/L-30g/L.
Further, the pH buffering agent is at least one of ammonia water, disodium hydrogen phosphate, potassium dihydrogen phosphate, boric acid, borax, sodium carbonate and aminoacetic acid, and is used for adjusting the pH value of the chemical reduction gold liquid to be between 1.5 and 3.5.
A process for gold plating by adopting the chemical reduction gold solution comprises the following steps:
the method comprises the following steps: firstly, a circuit is manufactured on a substrate, a metal layer is deposited on a ceramic substrate, and the substrate with a communicated circuit is obtained through etching;
step two: forming a mask on the substrate by using photoresist to obtain a substrate to be plated;
step three: plating a palladium layer on a substrate to be plated to obtain a palladium-plated substrate;
step four: carrying out nickel plating on the palladium plating substrate to obtain a nickel plating substrate;
step five: carrying out micro-corrosion on the nickel-plated substrate by using an acid solution to form a microporous nickel-plated substrate with a certain pore space;
step six: gold plating is carried out on the microporous nickel plating substrate by adopting a chemical reduction gold solution to obtain a semi-finished product;
step seven: and removing the covered photoresist and the redundant plating layer to obtain a finished product.
Further, the nickel plating adopts nickel plating solution comprising 20-40g/L of nickel sulfate, 20-30g/L of sodium hypophosphite, 8-10g/L of trisodium citrate and 0.1-1g/L of additive to carry out nickel plating.
Further, the method also comprises a pretreatment step, wherein the pretreatment step comprises the following steps: degreasing, polishing, acid washing, water washing, drying, ion beam cleaning and preheating.
Further, the additive is a compound of organic sodium salt and polyethylene glycol, and the concentration ratio of the organic sodium salt to the polyethylene glycol is 1:2-1:4.
further, the temperature of gold plating was 50 ℃.
Further, the palladium layer can be formed by electroplating, evaporation, sputtering, chemical plating, chemical deposition, and the like.
Furthermore, in the process of palladium plating, a sputtering mode can be adopted, the sputtering power of the palladium alloy is 15-21kw, the sputtering air pressure is 0.3Pa, the negative bias voltage is 450V, the deposition temperature is 200 ℃, and the deposition time is 10-30min.
Further, when the palladium alloy adopts chemical deposition, the nickel-plated substrate is placed in a chemical palladium plating solution, wherein the chemical palladium plating solution comprises a palladium compound, a hypophosphorous acid compound, a boron hydrogen compound, ammonium chloride, ammonia water, a composite complexing agent and a complexing stabilizer, the palladium compound can be favorably dispersed through the composite complexing agent and the complexing stabilizer, and the effect of preventing precipitation can be achieved. The binding force of nickel and gold can be increased through the target layer, the thickness of the nickel layer is controllable,
further, in the nickel plating process, the temperature of nickel plating is 50-85 ℃, the nickel plating is 3-5min, and the plating thickness can be repeated for a plurality of times according to the requirement, preferably 2-4 times.
Further, the nickel plating in-process, owing to need make the nickel layer form the nickel layer structure that has certain thickness, its nickel layer structure can be microporous structure or toper structure, can effectively increase the area of contact of nickel layer and chemical reduction gold liquid, consequently the nickel plating can adopt multilayer nickel plating many times, and, multilayer nickel crystal also can effectual control electroerosion's degree, makes it still have the nickel layer of accomplishing under the nickel layer structure, also can make the gold layer more even, prevents that the gold layer from having the defect of detail.
Furthermore, after each period of the nickel plating process, the substrate can be removed from the nickel plating solution, and cleaned to form layered nickel crystals, and the nickel plating is continued after observing the surface structure of the layered nickel crystals, or a surface with a microstructure is prepared among multiple layers of nickel crystals through micro polishing, so that the binding force between the nickel layers is increased, the nickel layers are prevented from being stripped, or the nickel plating is continued in the nickel plating solution directly, and the continuous nickel plating is carried out until the nickel plating is finished.
Further, the thickness of the nickel plating layer may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 μm.
Further, the method comprises a pretreatment step, wherein the pretreatment step comprises the following steps: degreasing, polishing, acid washing, water washing, drying, ion beam cleaning and preheating.
Further, the pre-treating step may include: washing the ceramic substrate with water, removing surface floating soil, performing acid washing, removing surface oxides, washing again with acid washing solution to remove acid, performing hydrogen-removing treatment, washing again, drying with 70-85 deg.C hot air, and performing nickel plating.
The oxide film on the surface can be removed through acid cleaning, the surface of the oxide film can have a slight corrosion effect, and the surface of the oxide film is rough, so that the bonding capability of the surface with metal or photoresist is improved, the phenomena of stress concentration and coating or mask separation among different materials are reduced, the hydrogen permeation condition in the acid cleaning process can be treated through hydrogen drive treatment, the stress corrosion phenomenon and the hydrogen embrittlement phenomenon are reduced, the oxide film has good bonding performance, and the problem of poor bonding degree caused by the phenomenon of high internal stress of a metal layer is solved;
further, the hydrogen purging treatment comprises: heating and baking at 180-200 deg.C for 3-4 hr.
Further, in the fifth step, after electroplating the palladium alloy serving as the nickel target material, washing with water for l-2min at room temperature, and then drying at 50-60 ℃ for drying with hot air at 85 ℃ for 3-4min.
The technical solutions of the present invention are described in detail below by using preferred embodiments, and it should be noted that the following specific embodiments are only examples and are not intended to limit the present invention.
Comprises the steps of pretreatment and nickel plating, wherein the pretreatment comprises the following steps: washing the ceramic substrate with water, removing surface floating soil, performing acid washing, removing surface oxides, washing again with a pickling solution to remove acid, performing hydrogen-removing treatment, washing again, drying with hot air at 70-85 ℃, and performing a nickel plating process;
the process for chemically reducing gold plating by using the gold liquid comprises the following steps:
the method comprises the following steps: firstly, a circuit is manufactured on a substrate, a metal layer is deposited on the ceramic substrate, and the substrate with a communication circuit is obtained through etching;
step two: forming a mask on the substrate by adopting photoresist to obtain a substrate to be plated;
step three: plating a palladium layer on the substrate to be plated to obtain a palladium-plated substrate;
step four: carrying out nickel plating on the palladium-plated substrate to obtain a nickel-plated substrate;
step five: carrying out micro-corrosion on the nickel-plated substrate by using an acid solution to form a microporous nickel-plated substrate with a certain pore space;
step six: gold plating is carried out on the microporous nickel plating substrate by adopting a chemical reduction gold solution to obtain a semi-finished product;
step seven: and removing the covered photoresist and the redundant plating layer to obtain a finished product.
Example 1:
gold is plated by adopting the method, and the adopted chemical reduction gold solution comprises the steps of taking aurous thiocyanate salt as a gold source and taking the ammonium thiocyanate and an auxiliary reducing agent to be matched as a composite reducing agent;
the concentration of the aurous thiocyanate salt in the chemical reduction gold solution is 1.5g/L;
the concentration of ammonium thiocyanate in the chemical reduction gold liquid is 10g/L;
the auxiliary reducing agent is formaldehyde, and the total concentration in the chemical nickel plating solution is 15g/L.
The auxiliary reducing agent comprises sodium hypophosphite which accounts for 1g/L-5g/L of the concentration in the chemical reduction gold liquid.
The auxiliary agents are polyethylene glycol and polyacrylamide, the concentration of the polyethylene glycol in the chemical reduced gold liquid is 1.5g/L, and the concentration of the polyacrylamide in the chemical reduced gold liquid is 0.8g/L.
The concentration of the composite complexing agent amino trimethylene phosphonic acid in the chemical reduction gold liquid is 10g/L.
The pH value of the chemical reduction gold liquid is adjusted to be 3.5.
Example 2:
gold is plated by adopting the method, and the adopted chemical reduction gold solution comprises the steps of taking aurous thiocyanate salt as a gold source and taking the ammonium thiocyanate and an auxiliary reducing agent to be matched as a composite reducing agent;
the concentration of the aurous thiocyanate salt in the chemical reduction gold solution is 2g/L;
the concentration of ammonium thiocyanate in the chemical reduction gold solution is 15g/L;
the auxiliary reducing agent is dimethylamine borane, and the total concentration in the chemical nickel plating solution is 20g/L.
The auxiliary reducing agent comprises sodium hypophosphite which accounts for 2g/L of the concentration of the chemical reduction gold liquid.
The auxiliary agents are polyethylene glycol and polyacrylamide, the concentration of the polyethylene glycol in the chemical reduced gold liquid is 1.7g/L, and the concentration of the polyacrylamide in the chemical reduced gold liquid is 1g/L.
The composite complexing agent is ethylenediamine tetramethylene phosphoric acid, and the concentration of the composite complexing agent in the chemical reduction gold liquid is 20g/L.
The pH value of the chemical reduction gold liquid is adjusted to be 2.
Example 3:
gold is plated by adopting the method, and the adopted chemical reduction gold solution comprises the steps of taking aurous thiocyanate salt as a gold source and taking the ammonium thiocyanate and an auxiliary reducing agent to be matched as a composite reducing agent;
the concentration of the aurous thiocyanate salt in the chemical reduction gold liquid is 2.5g/L;
the concentration of ammonium thiocyanate in the chemical reduction gold liquid is 20g/L;
the auxiliary reducing agent is sodium hypophosphite, and the total concentration of the auxiliary reducing agent in the chemical nickel plating solution is 30g/L.
The auxiliary reducing agent comprises potassium dihydrogen phosphate 4g/L.
The auxiliary agents are polyethylene glycol and polyacrylamide, the concentration of the polyethylene glycol in the chemical reduction gold liquid is 2g/L, and the concentration of the polyacrylamide in the chemical reduction gold liquid is 1.5g/L.
The composite complexing agent is one of ethylenediamine, and the concentration of the composite complexing agent in the chemical reduced gold liquid is 25g/L.
The pH value of the chemical reduction gold liquid is adjusted to be 2.
Example 4:
the gold plating is carried out by adopting the method, and the adopted chemical reduction gold solution comprises the steps of taking aurous thiocyanate as a gold source and taking the ammonium thiocyanate and an auxiliary reducing agent to be matched as a composite reducing agent;
the concentration of the aurous thiocyanate salt in the chemical reduction gold solution is 2g/L;
the concentration of ammonium thiocyanate in the chemical reduction gold liquid is 15g/L;
the auxiliary reducing agent is boron hydride, and the total concentration of the boron hydride in the electroless nickel plating solution is 40g/L.
The auxiliary reducing agent comprises 5g/L potassium dihydrogen phosphate.
The auxiliary agents are polyethylene glycol and polyacrylamide, the concentration of the polyethylene glycol in the chemical reduced gold liquid is 2g/L, and the concentration of the polyacrylamide in the chemical reduced gold liquid is 1.5g/L.
The composite complexing agent is ethylenediamine, and the concentration of the composite complexing agent in the chemical reduction gold liquid is 30g/L.
The pH value of the chemical reduction gold liquid is adjusted to be 1.5.
Experimental groups:
the influence of the conventional welding performance is mainly influenced by the damage of the metal surface, so the salt spray test and the damage test are adopted to represent the effect of the product in the nickel plating process provided by the invention.
(1) Salt spray resistance test: the finished products of examples 1 to 4 were used as test groups and subjected to a salt spray resistance test, and test groups A to D were placed in a salt spray resistance test chamber, respectively, and the time at which corrosion occurred on the surfaces was measured, and the results are shown in Table 1.
Table 1: results of salt spray resistance test
Experimental group A Experimental group B Experimental group C Experimental group D
Time of etching 89 hours 94 hours 98 hours 95 hours
As can be seen from the table 1, the chemical reduction gold liquid enables the plating layer to have better brightness and uniformity and better micro-morphology, and also solves the problems that the gold changing liquid is excessively corroded to generate serious nickel corrosion, so that the phenomenon that parts fall off or the interface of soldering tin and a welding pad is cracked after welding is influenced. The gold layer and the nickel layer have better bonding capability.
The environment-friendly chemical reduction gold liquid provided by the invention can effectively improve the reliability of welding spots, and solves the problem that the quality and reliability of products cannot meet the requirement of high weldability, so that the environment-friendly chemical reduction gold liquid has a longer service life, and the gold surface can keep excellent welding performance for a long time.
The embodiments of the present invention have been described in detail, but the description is only for the preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made within the scope of the present invention should be covered by the present patent.

Claims (10)

1. An environment-friendly chemical reduction gold liquid is characterized in that: comprises the steps of taking aurous thiocyanate as a gold source and taking ammonium thiocyanate and an auxiliary reducing agent as a composite reducing agent in a matching way;
the concentration of the aurous thiocyanate salt in the chemical reduction gold liquid is 1.5g/L-2.5g/L;
the concentration of the ammonium thiocyanate in the chemical reduction gold solution is 10-20 g/L;
and a complex complexing agent, a pH buffer and an adjuvant.
2. The environment-friendly chemical reduced gold liquid according to claim 1, wherein: the auxiliary reducing agent is at least one of formaldehyde, dimethylamine borane, sodium hypophosphite, hydrazine and hydroboron, and the total concentration of the auxiliary reducing agent in the chemical nickel plating solution is 15g/L-40g/L.
3. The environment-friendly chemical reduced gold liquid according to claim 1, wherein: the auxiliary reducing agent also comprises at least one of sodium hypophosphite, sodium hypophosphite and potassium dihydrogen phosphate, and the concentration of the auxiliary reducing agent in the chemical reduction gold liquid is 1g/L-5g/L.
4. The environment-friendly chemical reduced gold liquid according to claim 1, wherein: the auxiliary agent is polyethylene glycol and polyacrylamide, the concentration of the polyethylene glycol in the chemical reduced gold liquid is 1.5g/L-2g/L, and the concentration of the polyacrylamide in the chemical reduced gold liquid is 0.8g/L-1.5g/L.
5. The environment-friendly chemical reduced gold liquid according to claim 1, wherein: one of composite complexing agent aminotrimethylene phosphonic acid, ethylene diamine tetramethylene phosphoric acid and ethylenediamine, wherein the concentration of the composite complexing agent in the chemical reduced gold liquid is 10g/L-30g/L.
6. The environment-friendly chemical reduced gold liquid according to claim 1, characterized in that: the pH buffering agent is at least one of ammonia water, disodium hydrogen phosphate, potassium dihydrogen phosphate, boric acid, borax, sodium carbonate and aminoacetic acid, and is used for adjusting the pH value of the chemical reduction gold liquid to be 1.5-3.5.
7. A process for gold plating using the chemically reduced gold plating solution of any one of claims 1 to 6, wherein: the method comprises the following steps:
the method comprises the following steps: firstly, a circuit is manufactured on a substrate, a metal layer is deposited on the ceramic substrate, and the substrate with the connected circuit is obtained through etching;
step two: forming a mask on the substrate by using photoresist to obtain a substrate to be plated;
step three: plating a palladium layer on the substrate to be plated to obtain a palladium-plated substrate;
step four: carrying out nickel plating on the palladium-plated substrate to obtain a nickel-plated substrate;
step five: carrying out micro-corrosion on the nickel-plated substrate by using an acid solution to form a microporous nickel-plated substrate with a certain pore space;
step six: carrying out gold plating on the microporous nickel-plated substrate by adopting the chemical reduction gold solution to obtain a semi-finished product;
step seven: and removing the covered photoresist and the redundant plating layer to obtain a finished product.
8. The environment-friendly chemical reduced gold liquid according to claim 1, wherein: the nickel plating adopts nickel plating solution comprising 20-40g/L of nickel sulfate, 20-30g/L of sodium hypophosphite, 8-10g/L of trisodium citrate and 0.1-1g/L of additive to carry out nickel plating.
9. The environment-friendly chemical reduced gold liquid according to claim 1, characterized in that: further comprising a pre-processing step, the pre-processing step comprising: degreasing, polishing, acid washing, water washing, drying, ion beam cleaning and preheating.
10. The environment-friendly chemical reduced gold liquid according to claim 8, characterized in that: the additive is a compound of organic sodium salt and polyethylene glycol, and the concentration ratio of the organic sodium salt to the polyethylene glycol is 1:2-1:4.
CN202211395848.XA 2022-11-08 2022-11-08 Environment-friendly chemical reduction gold liquid and process thereof Pending CN115558912A (en)

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Citations (3)

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Publication number Priority date Publication date Assignee Title
JPH09171714A (en) * 1995-12-21 1997-06-30 Nippon Chem Ind Co Ltd Conductive powder
JP2017025399A (en) * 2015-07-28 2017-02-02 上村工業株式会社 Non-cyanide electroless gold plating bath, and electroless gold plating method
CN113151814A (en) * 2021-02-05 2021-07-23 深圳市联合蓝海黄金材料科技股份有限公司 Composition for cyanide-free electroless gold plating solution and application thereof, and cyanide-free electroless gold plating solution and application thereof

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09171714A (en) * 1995-12-21 1997-06-30 Nippon Chem Ind Co Ltd Conductive powder
JP2017025399A (en) * 2015-07-28 2017-02-02 上村工業株式会社 Non-cyanide electroless gold plating bath, and electroless gold plating method
CN113151814A (en) * 2021-02-05 2021-07-23 深圳市联合蓝海黄金材料科技股份有限公司 Composition for cyanide-free electroless gold plating solution and application thereof, and cyanide-free electroless gold plating solution and application thereof

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