WO2017012177A1

WO2017012177A1 - Precious metal-silicon composite powder prepared by means of galvani reaction, and application thereof

Info

Publication number: WO2017012177A1
Application number: PCT/CN2015/088510
Authority: WO
Inventors: 吕铁铮; 赵丽丽
Original assignee: 吕铁铮; 赵丽丽
Priority date: 2015-07-17
Filing date: 2015-08-31
Publication date: 2017-01-26
Also published as: CN104972112B; CN104972112A

Abstract

Precious metal-silicon composite powder prepared by means of a Galvani reaction, and an application thereof. By means of match between electron gain or loss in a Si-Si bond and chemical potentials for atomic reduction of Au³⁺/Au, Ag⁺/Ag, Cu²⁺/Cu, and the like, galvanic displacement reaction is carried out on superfine silicon powder and a solution containing precious metal ions in an HF environment. The superfine silicon powder is used as a reducing agent and a reaction carrier as well, and precious metal Au, Ag, Cu, and the like are gradually deposited on the surface of the superfine silicon powder after being displaced from the solution, so as to form a precious metal-silicon (shell-core) micro-nanostructure particle. Due to the fact that the surface of the shell-core micro-nanostructure particle is provided with a precious metal layer, the particle has the characteristics of precious metal, such as high conductivity. However, the use amount of the precious metal is greatly reduced, and therefore the cost can be greatly reduced.

Description

Precious metal-silicon composite powder prepared by galvanic reaction and application thereof

Technical field

The present invention relates to a noble metal-silicon composite powder, and more particularly to a noble metal-silicon composite powder prepared by using a galvanic reaction and its conductive application.

Background technique

Precious metals such as gold, silver, copper and their powders are commonly used metal materials. Precious metal powders have been used as raw materials for conductive pastes due to their excellent electrical conductivity, chemical catalytic activity and the like, and precious metals also play an important role in the field of catalysts.

As countries pay more and more attention to environmental protection, new energy vehicles, especially electric vehicles, have entered the blowout period. As a key supporting power battery and fuel cell, more and more attention has been paid, especially for precious metal catalyst platinum for fuel cells. The demand for palladium powder materials will also increase rapidly.

Gold powder is chemically stable and has good electrical conductivity, but it is expensive, and its use is limited to thick-film integrated circuits. Silver-based conductive materials are widely used in various industries. For example, the demand for precious metal silver in the semiconductor and electronics industries is as follows. With the rapid development of the electronics industry, China's demand for silver powder is growing. At present, the use of silver conductive paste for electronic components in China is roughly as follows: the use of discrete components of silver electronic paste is 240-300 tons / year, the use of silver powder is 180-240 tons / year; the internal electrodes and ends of chip components Electro-board silver conductive paste dosage 60-96 tons / year, silver powder dosage 36-72 tons / year; silver conductive adhesive 36-60 tons / year, silver powder dosage 24-36 tons / year; silver polymer conductive charge 240- 300 tons / year, need silver powder 180-240 tons / year; automotive defrosting line silver 36-60 tons / year, need silver powder 24-36 tons / year; and electrical alloy silver dosage 120-180 tons / year. In terms of the above traditional silver powder, the total amount of silver powder used per year is 600-840 tons. However, China's ultra-fine silver powder preparation technology started late, and the overall level is not high. So far, there is still a shortage of ultra-fine silver powder production enterprises. Compared with foreign manufacturers, the domestically produced silver powder varieties are not comprehensive enough, and the performance is also different from that of foreign countries. The dynamic preparation technology is also far behind. The price of copper powder is relatively cheap and the use is more extensive, but the copper powder has the problem of being easily oxidized.

Due to the early development and rapid development of foreign electronic slurry, the product range is complete, the industry scale is large, the research and development intensity is large, the product renewal cycle is short, the production and quality control methods are complete, and the market share is high. In recent years, some high-performance, high-reliability conductive silver adhesives have emerged in foreign countries. For example, in order to greatly reduce the production cost of electronic paste, a base metal such as nickel or aluminum is used as a base powder, which is mixed with silver powder. The mixed powder or composite alloy powder is used to prepare the slurry; the pure silver paste, the Ag-Pd slurry and even the base metal slurry can meet the requirements for the use of the RC components for the production of chip components.

Precious metal powder is one of the key raw materials for electronic paste. Among them, gold powder, silver powder and the like are mainly used as conductive fillers of electronic paste. The morphology, particle size, particle size distribution, bulk density, etc. of the powder all have a significant effect on the performance of the electronic paste, thus affecting the performance of the final product. Therefore, the preparation of excellent gold powder and silver powder is an excellent performance of the electronic pulp. Prerequisites for materials.

The precious metal powder can be divided into nano powder (average particle diameter less than 0.1 μm), submicron powder (average particle diameter in the range of 0.1 to 10 μm), fine powder (average particle diameter larger than 10 μm), and gold powder used in the conductive paste. Silver powder is mainly composed of submicron powder. Because of its small particle size and size effect, its melting point is much lower than the melting point of elemental silver, and it has good performance of low temperature sintering after being made into conductive paste. In addition, when the flake silver powder is used as the conductive phase in the slurry, since the conductive network structure capable of forming surface contact or line contact, the conductive property is much better than the point contact formed between the spherical silver powder, so the flake silver powder can also be used. The conductive phase of the conductive paste.

The key to the preparation of conductive pastes is the preparation of ultrafine conductive precious metal powders.

At present, precious metal powders such as silver powder and gold powder can be prepared by chemical methods and physical methods. Chemical methods mainly include liquid-liquid interface reaction method, microwave method, hydrothermal reduction method, chemical deposition method, microwave heating method, ultraviolet photochemical method, acoustic electrochemical method, solvothermal method, chemical reduction method, radiation method, ultrasonic diffusion method, Photochemical method, spray pyrolysis method, electrolysis method, and the like. However, most of these methods have more or less preparation conditions. The defects such as engraving, high requirements on production equipment, and complicated preparation processes make it difficult to apply to industrial mass production. Commonly used physical methods include mechanical ball milling, atomization, and the like.

In the chemical method, the chemical reduction method is more commonly used, because of its simple equipment, easy control of parameters, convenient operation, low energy consumption, low cost, simple process, and suitable for large-scale production and wide application. This method is the application of the principle of redox reaction by reducing silver ions to silver by a reducing agent under liquid, solid or gas phase conditions. Among them, the liquid phase chemical reduction method is more widely used, and the liquid phase chemical reduction method for preparing the ultrafine precious metal powder refers to the reduction of the powder from the oxidizing salt solution under the appropriate process conditions by using a reducing agent.

The oxidizing solution mainly used for producing gold powder is chloroauric acid or chloroauric acid salt, and the oxidizing solution of silver powder is AgNO3 or AgF solution. Common reducing agents are ascorbic acid, hydrazine hydrate, hydrogen peroxide, oxygen, sodium methanesulfonate, and ammonium formate. Ascorbic acid is moderately used and its reaction rate is easy to control. It is widely used in the preparation of ultrafine silver powder for conductive paste. It can be controlled by different conditions such as reaction temperature and dispersant. Ultrafine silver powder of particle size.

After the precious metal powder is prepared, it is mixed with a solvent, a curing agent, a coupling agent, an antifoaming agent and the like according to a certain ratio, and is ground to obtain a certain viscosity, and then can be used as a conductive paste. For example, after the silver powder is prepared, it can be mixed with an epoxy resin, a silane coupling agent, or the like to form a conductive silver paste.

With the rapid development of the fine electronics manufacturing industry, the light weight, miniaturization and high performance of precious metal conductive pastes have become a trend, and higher requirements have been placed on noble metal conductive pastes, mainly to find low density and low price. High-performance conductive materials to partially or completely replace gold, silver and other precious metals have become a hot research topic at home and abroad, by using low-cost materials and precious metals to reduce the amount of precious metals, thereby reducing the cost of conductive paste, so precious metals and other inorganic Or a composite conductive material of organic particles, such as silver-coated metal particles, conductive fillers of inorganic or organic particles, can satisfy this requirement, especially silver The inorganic or organic particles of the package have low density and good electrical properties, and have received extensive attention.

However, in the process of preparing the precious metal coated particle composite material, the coated particles are mostly inorganic oxides, such as nano-scale, micro-scale SiO ₂ , Al ₂ O _{3 ,} etc., and the inorganic oxide itself is an insulating material. Therefore, the combination with the precious metal itself greatly reduces the electrical conductivity of the composite conductive material.

In addition, in the process of coating the above materials with precious metals, the principle of silver mirror reaction is mainly used. Although it is also a redox process, the process is complicated, including several steps of roughening, sensitization, and silver mirror reaction.

Furthermore, in the silver mirror reaction, the silver salt solution is first converted into a silver ammonia solution of a specific pH value, and the material to be coated is mixed with a reducing agent to form a reducing solution, and finally the silver ammonia solution is gradually added to the solution. In the reducing solution, a silver mirror reaction occurs, and the entire reaction takes a long time, and the parameters such as temperature and pH during the reaction are more demanding. These complex steps and higher process requirements also add to the cost of preparing the silver coated composite. Most importantly, the redox silver mirror reaction is limited by the different chemical potentials of the reducing agent. For different precious metals, the reducing agent can be selected to be limited.

Summary of the invention

The technical problem to be solved by the present invention is to overcome the above-mentioned drawbacks existing in the prior art, and provide a noble metal-silicon composite powder prepared by a galvanic reaction and a conductive application thereof, the noble metal-silicon composite powder having good electrical conductivity of a noble metal However, the amount of precious metals is greatly reduced.

The technical solution adopted by the present invention to solve the technical problem thereof is: a noble metal-silicon composite powder prepared by a galvanic reaction, which is prepared according to the following method:

(1) preparing a hydrofluoric acid solution having a concentration of 1-5 mol/L;

(2) adding the hydrofluoric acid solution prepared in the step (1) to the container containing the ultrafine silicon fine powder, and continuously stirring;

(3) preparing a solution containing precious metal ions at a concentration of 0.001-10 mol/L;

(4) adding the noble metal ion-containing solution in the step (3) to the hydrofluoric acid solution containing the ultrafine silicon micropowder prepared in the step (2); the galvanic reaction occurs, and the reaction time is 5-120 min. The surface of the ultrafine silicon micropowder is replaced by noble metal ions to form particles coated with a noble metal film on the surface of the ultrafine silicon micropowder; the weight ratio of precious metal ions participating in the reaction to the silicon is in the range of (10-1): (1-10);

The ultrafine silicon micropowder itself serves as both a reducing agent and a reaction carrier;

(5) After the reaction of the step (4), the ultrafine silicon fine powder coated with the noble metal film is separated from the reaction system by centrifugal separation or filtration, washed, and dried to obtain a noble metal-silicon composite powder.

Further, the noble metal is gold, silver or copper.

Further, in the step (2), the ultrafine silicon micropowder is silicon scrap produced during the processing of the band saw, edging, polishing, multi-wire cutting machine in the process of processing the photovoltaic crystal silicon or the semiconductor silicon, or the ultrafine metal silicon The silicon waste or ultrafine metal silicon powder has a particle diameter of 0.5 to 5 μm.

Further, in the step (3), the noble metal ion-containing solution is obtained by reacting an oxide or a noble metal salt of a noble metal with an acid, and dissolving with water; according to different precious metal elements, the solution contains Au ⁴⁺ and Ag, respectively. ⁺ or Cu ²⁺ ; the acid is preferably a medium strength acid or a strong acid.

Further, in the step (3), the noble metal ion-containing solution is a chloroauric acid solution, a chloroaurate solution, a silver nitrate solution, a silver fluoride solution, a copper chloride solution, a copper nitrate solution or a copper sulfate solution.

Further, in the step (5), the percentage of the noble metal in the noble metal-silicon composite powder is 30 to 99% by weight.

The ultrafine silicon micropowder has the following characteristics: 1 has a specific doping property, and the mother silicon needs specific conductivity, so special doping is performed, and doping can provide electrons required for redox reaction; 2 high chemical purity Because it is derived from the mother semiconductor silicon or photovoltaic silicon, it has high purity; the ultrafine metal silicon powder has a purity greater than 99%, and the impurities also have certain doping characteristics, and thus can also be in the present invention. use.

The present invention also includes the use of the noble metal-silicon composite powder prepared by the galvanic reaction in the preparation of a conductive material comprising a conductive paste, a conductive ink, and a conductive paste.

A conductive paste comprising a noble metal-silicon composite powder prepared by the galvanic reaction of the present invention.

A conductive ink for printing electrons, comprising a noble metal-silicon composite powder prepared by the galvanic reaction of the present invention.

Compared with the prior art, the present invention has the following advantages:

(1) The noble metal-silicon composite powder of the present invention has excellent electrical conductivity of a precious metal, and the amount of the precious metal is greatly reduced, thereby greatly reducing the cost;

(2) The preparation process is simple, the operation is easy, and the industrial production is easy.

BRIEF DESCRIPTION OF THE DRAWINGS:

1 is a scanning electron micrograph of a silver-silicon composite powder product of Example 1 of the present invention;

2 is an EDX diagram of elemental analysis of a silver-silicon composite powder product according to Embodiment 1 of the present invention;

3 is a transmission electron micrograph of a gold-silicon composite powder product according to Embodiment 3 of the present invention;

Figure 4 is a transmission electron micrograph of a copper-silicon composite powder of Example 5 of the present invention.

detailed description

The invention is further illustrated by the following examples.

Example 1

The galvanic reaction of the present embodiment was used to prepare a silver-silicon composite powder, which was prepared by the following method:

(1) preparing a hydrofluoric acid solution having a concentration of 5 mol/L, and stirring the hydrofluoric acid solution;

(2) adding the hydrofluoric acid solution prepared in the step (1) to a vessel containing 0.7 mol of ultrafine silicon micropowder, and continuously stirring to remove the oxide layer on the surface of the ultrafine silicon micropowder; since the surface of the silicon powder is oxidized Therefore, the surface SiO ₂ will be corroded by hydrofluoric acid, and a large amount of irritating bubbles are generated in the solution, and the specific reaction is as follows: SiO ₂ +6HF→H ₂ SiF ₆ +2H ₂ O;

After EDX element test, the ultrafine silicon micropowder has an oxygen content of 16%, and the corresponding SiO2 content is 30%, which is corroded by hydrofluoric acid. Therefore, only 70% of the silicon is retained to participate in the subsequent galvanic reaction, weighing about 14g. , equivalent to 0.5mol;

(3) arranging a solution containing 33.5 g of silver fluoride, which is converted into a silver content of about 28 g, which is 0.264 mol; and the silver fluoride solution is prepared by reacting silver oxide with hydrofluoric acid and adding water;

(4) The silver fluoride solution in the step (3) is gradually added to the hydrofluoric acid solution containing the ultrafine silicon micropowder prepared in the step (2); the galvanic reaction occurs, and the galvanic reaction formula is as follows:

4Ag ⁺ +Si+6HF→4Ag+H ₂ SiF ₆ +4H ⁺ ;

The reaction time is 30 min, the surface of the ultrafine silicon micropowder is replaced by silver ions, and a silver film is formed to coat the surface of the ultrafine silicon micropowder; at the same time, the color of the solution changes from the initial black to the earthy yellow; the khaki is the color of the micron-sized silver film;

(5) The ultrafine silicon fine powder coated with the silver film on the surface after the reaction in the step (4) is centrifugally separated from the reaction system, repeatedly washed, and dried to obtain a silver-silicon composite powder.

The scanning electron microscope morphology distribution of the silver-silicon composite powder product of the present embodiment is shown in FIG. 1; the weight of the silver-silicon composite powder is 35 g, and the reaction yield is >80%, and the element content of the silver-silicon composite powder. As shown in the elemental EDX diagram of Fig. 2, the silver-silicon composite powder has a silver: silicon germanium 2:1, the percentage of silver as a composite powder is 66.7%, and silicon accounts for 33.3%.

The ultrafine silicon micropowder is used as a reaction reducing agent, and the ultrafine silicon micropowder is derived from the silicon scrap generated during the processing of the band saw, the edging, the polishing, the multi-wire cutting machine in the process of processing the photovoltaic crystal silicon or the semiconductor silicon, and the average particle of the silicon waste. The diameter is 0.5 micrometer; the ultrafine silicon micropowder has the following characteristics: 1 has a specific doping property, and the mother silicon needs specific conductivity, so a specific doping is performed, and the doping can provide electrons required for the redox reaction; 2 High chemical purity, because of its semiconductor silicon or photovoltaic silicon from the mother, it has a high purity.

Application: The silver-silicon composite powder product of the present embodiment is applied to a conductive paste. According to the conventional process of the conductive paste, the silver-silicon composite powder is used to replace the silver powder, and other components such as a binder, a solvent, etc. are unchanged, and the specific ratio is a silver-silicon composite powder: an epoxy resin E-51: a curing agent: a solvent : Coupling agent = 55:20:1:23:1; After mixing the above materials, the mixture was uniformly stirred, ground, and finally a conductive paste was formed. The conductive paste prepared above is coated with a certain pattern of conductive paste on a glass substrate by a screen printing device, cured at 60 ° C, and finally measured for electrical conductivity, and its resistivity reaches 1.80 × 10 ^-7 Ω. m has reached the requirement of conductive paste; the resistivity before replacement is 6.10×10 ^-8 Ω·m.

Taking the conductive paste used in the production process of the photovoltaic cell as an example, in the process of metallization and sintering of the cell, the average wet weight of the silver paste used in the cell sheet is about 0.18 g/piece, wherein the solid silver powder content is about 0.1 g; After replacing the pure solid silver powder with the silicon composite powder, the amount of silver used is reduced by 30-40%, which is about 0.03 g. According to the international market price of silver of 3.6 yuan / g, each cell can save silver cost of 0.1 yuan; the power output of each cell is about 4.4 watts, the photovoltaic power generation cost is reduced by 0.02 yuan / watt.

Example 2

The difference between this embodiment and the embodiment 1 is only that: in the step (1), a hydrofluoric acid solution having a concentration of 1 mol/L is prepared; in the step (2), the ultrafine silicon micropowder is derived from the process of processing the photovoltaic crystal silicon or the semiconductor silicon. Saw, edging, polishing, silicon scrap produced during multi-wire cutting process, the average particle size of silicon waste is 5 microns; in step (3), 2L solution containing 0.001mol/L silver nitrate is prepared; silver nitrate solution The reaction is carried out by reacting silver oxide with nitric acid and adding water; in step (4), the galvanic reaction time is 60 min; in step (5), the powder is separated by filtration, the elemental analysis of the silver-silicon composite powder, and the silver in the silver-silicon composite powder. : Silicon germanium 3:7, silver accounts for 30% of the composite powder, and silicon accounts for 70%.

The rest are the same as in the first embodiment.

Application: The above silver-silicon composite powder is applied to a conductive ink for printing electrons. The silver powder is replaced with the silver-silicon composite powder in accordance with a conventional process of conductive ink. The conductive oil prepared above is coated with a screen printing device, and a certain pattern of conductive paste is coated on the glass substrate, solidified and dried, and finally the electrical conductivity is measured, and the resistivity thereof reaches 8.80×10 ^-5 Ω·m. The requirement of conductive ink is reached; the resistivity before replacement is 2.70×10 ^-6 Ω·m.

Example 3

The method for preparing a gold-silicon composite powder by the galvanic reaction of the present embodiment, and the application of the gold-silicon composite powder prepared by the process, comprises the following steps:

(1) preparing a hydrofluoric acid solution having a concentration of 3 mol/L, and stirring the hydrofluoric acid solution;

(2) slowly adding the hydrofluoric acid solution prepared in the step (1) to a container containing 40 g of ultrafine silicon micropowder, and continuously stirring to remove the oxide layer on the surface of the ultrafine silicon micropowder; Oxidation, so the surface of SiO ₂ will be corroded by hydrofluoric acid, a large amount of irritating bubbles are generated in the solution, the specific reaction is as follows: SiO ₂ +6HF → H ₂ SiF ₆ + 2H ₂ O;

(3) arranging a solution containing about 24 grams of chloroauric acid, which is converted into a gold content of about 14 grams, which is 0.071 mol;

(4) The chloroauric acid solution in the step (3) is gradually added to the hydrofluoric acid solution containing the ultrafine silicon micropowder prepared in the step (2); the galvanic reaction occurs, and the galvanic reaction formula is as follows:

2Au ³⁺ +Si+8HF→2Au+H ₂ SiF ₆ +6H ⁺ ;

The reaction time was 120 min, and the surface of the ultrafine silicon micropowder was replaced by gold ions to form a gold film coated on the surface of the ultrafine silicon micropowder; at the same time, the color of the solution changed from the initial black to the tan. Sepia is the color of the nano-scale gold film.

(5) The ultrafine silicon fine powder coated with the gold film on the surface after the reaction in the step (4) is centrifugally separated from the reaction system, washed, dried, and ready. According to EDX elemental analysis, gold accounts for 35% of the composite powder and silicon accounts for 65%. The transmission electron micrograph of the gold-silicon composite powder is shown in Fig. 3.

The above ultrafine silicon micropowder is used as a reaction reducing agent, and the ultrafine silicon micropowder is derived from photovoltaic crystal silicon or semiconductor silicon plus In the process of band sawing, edging, polishing, and silicon scrap produced during the processing of multi-wire cutting machine, the particle size of silicon waste is 3 micrometers; the ultrafine silicon micropowder has the following characteristics: 1 has specific doping properties, and its parent body Since silicon requires a certain conductivity, it is specifically doped, and the doping can provide the electrons required for the redox reaction. 2 The chemical purity is high, and since it is derived from the mother semiconductor or photovoltaic silicon, it has high purity. .

Application: The above gold-silicon composite powder is applied to a conductive paste. According to the conventional process of conductive near-gel, the gold-silicon composite powder is used to replace the gold powder, and other components such as a binder, a solvent, etc. are unchanged, and the specific ratio is gold-silicon composite powder: epoxy resin E-51: curing agent: solvent : Antifoaming agent = 55:20:1:23:1; After mixing the above materials, the mixture is uniformly stirred, ground, and finally a conductive paste is formed. The above conductive adhesive is screen-printed, and a certain pattern of conductive adhesive is coated on the glass substrate, cured and dried at 60 ° C, and finally its conductivity is measured, and its resistivity is 5.80×10 ^-6 Ω·m. The requirement of conductive adhesive is reached; the resistivity before replacement is 1.45×10 ^-8 Ω·m.

Example 4

The difference between this embodiment and the third embodiment is only that: in the step (1), a hydrofluoric acid solution having a concentration of 4 mol/L is prepared; in the step (2), the ultrafine silicon micropowder is derived from the ultrafine metal silicon powder and the silicon powder. The diameter is 1 micrometer, 2g; in step (3), a solution containing about 50 grams of sodium chloroaurate is disposed, and the gold content is converted into about 24 grams, which is 0.122 mol; in step (4), the galvanic reaction time is It is 100 min; in step (5), the gold-silicon composite powder is analyzed by EDX element, and the percentage of gold as a composite powder is 99%, and silicon accounts for 1%.

The ultrafine metal silicon powder has a purity of more than 99%, and the impurities also have certain doping characteristics, and are used in the present embodiment.

The rest is the same as in the third embodiment.

Application: The above gold-silicon composite powder is applied to a conductive paste. According to the conventional process of conductive near-gel, the gold-silicon composite powder is used to replace the gold powder, and other components such as a binder, a solvent, etc. are unchanged, and the specific ratio is gold-silicon composite powder: epoxy resin E-51: curing agent: solvent : Antifoaming agent = 55:20:1:23:1; After mixing the above materials, the mixture is uniformly stirred, ground, and finally a conductive paste is formed. The above conductive adhesive is applied by screen printing equipment, and a certain pattern of conductive adhesive is coated on the glass substrate, cured and dried at 80 ° C, and finally its conductivity is measured, and its resistivity is 3.68×10 ^-8 Ω·m. Reach the resistivity of pure conductive gold powder.

Example 5

The method for preparing a copper-silicon composite powder by the galvanic reaction of the present embodiment, and the application of the copper-silicon composite powder prepared by the process, comprising the following steps:

(1) preparing a hydrofluoric acid solution having a concentration of 2 mol/L, and stirring the hydrofluoric acid solution;

(2) slowly adding the hydrofluoric acid solution prepared in the step (1) to a vessel containing 3 mol of ultrafine silicon micropowder, and continuously stirring to remove the oxide layer on the surface of the ultrafine silicon micropowder; since the surface of the silicon powder is oxidized , so the surface of SiO ₂ will be corroded by hydrofluoric acid, a large amount of irritating bubbles are generated in the solution, the specific reaction is as follows: SiO ₂ +6HF → H ₂ SiF ₆ + 2H ₂ O;

(3) 1mL solution of 10mol / L CuCl ₂ is prepared, and the copper content is 640g, which is 10mol;

(4) The CuCl ₂ solution in the step (3) is gradually added to the hydrofluoric acid solution containing the ultrafine silicon micropowder prepared in the step (2); the galvanic reaction occurs, and the galvanic reaction formula is as follows:

2Cu ²⁺ +Si+6HF→2Cu+H ₂ SiF ₆ +4H ⁺ ;

The reaction time was 5 min, and the surface of the ultrafine silicon micropowder was replaced by copper ions to form a copper film coated on the surface of the ultrafine silicon micropowder, and the surface color was bright black.

(5) The ultrafine silicon fine powder coated with the noble metal film on the surface after the reaction in the step (4) is separated from the reaction system by filtration, repeatedly washed, and dried to obtain a copper-silicon composite powder. According to EDX elemental analysis, copper accounts for 40% of the composite powder and silicon accounts for 60%. The transmission electron micrograph of the copper-silicon composite powder is shown in Fig. 4.

The above ultrafine silicon micropowder is used as a reaction reducing agent, and the ultrafine silicon micropowder is a metal silicon powder, and the particle size of the silicon powder is 4. Micron.

Application: The above copper-silicon composite powder is applied to a conductive paste. According to the conventional process of conductive near glue, the copper powder is replaced by the copper-silicon composite powder, and other components such as a binder, a solvent, etc. are unchanged, and the specific ratio is copper-silicon composite powder: epoxy resin E-51: curing agent: Solvent: Coupling agent = 55:20:1:23:1; the above materials were mixed, stirred uniformly, and finally formed into a conductive paste. The above conductive adhesive is screen-printed, and a certain pattern of conductive adhesive is coated on the glass substrate, cured and dried at 75 ° C, and finally its conductivity is measured, and its resistivity is 3.60×10 ^-7 Ω·m. The requirement of conductive adhesive is reached; the resistivity before replacement is 1.85×10 ^-7 Ω·m.

Example 6

The difference between this embodiment and the embodiment 5 is only that: in the step (1), a hydrofluoric acid solution having a concentration of 5 mol/L is prepared; in the step (2), the particle size of the ultrafine silicon micropowder is 2 μm; and the step (3) In the process, 1.5L of a solution containing 2 mol/L Cu(NO ₃ ) ₂ is prepared, and the copper content is 192 g, which is 3 mol; in step (4), the galvanic reaction time is 10 min; in the step (5), copper-silicon The composite powder was analyzed by EDX element, and the percentage of copper in the composite powder was 55%, and the silicon accounted for 45%.

The rest is the same as in Example 5.

Application: The above copper-silicon composite powder is applied to a conductive paste. According to the conventional process of conductive near glue, the copper powder is replaced by the copper-silicon composite powder, and other components such as a binder, a solvent, etc. are unchanged, and the specific ratio is copper-silicon composite powder: epoxy resin E-51: curing agent: Solvent: Coupling agent = 55:20:1:23:1; the above materials were mixed, stirred uniformly, and finally formed into a conductive paste. The above conductive adhesive is applied by screen printing equipment, and a certain pattern of conductive adhesive is coated on the glass substrate, solidified and dried at 60 ° C, and finally its conductivity is measured, and its resistivity is 3.20×10 ^-7 Ω·m. The requirement of conductive adhesive is reached; the resistivity before replacement is 1.85×10 ^-7 Ω·m.

Example 7

The difference between this embodiment and the embodiment 5 is only that: in the step (1), a hydrofluoric acid solution having a concentration of 2.5 mol/L is prepared; in the step (2), the particle size of the ultrafine silicon micropowder is 2 micrometers; In the process, 2L of a solution containing 5 mol/L CuSO ₄ is prepared, and the copper content is 640 g, which is 10 mol; in step (4), the galvanic reaction time is 80 min; in the step (5), the copper-silicon composite powder is passed through EDX. Elemental analysis, copper accounted for 85% of the composite powder and silicon accounted for 15%.

The rest is the same as in Example 5.

Application: The above copper-silicon composite powder is applied to a conductive paste. According to the conventional process of conductive near glue, the copper powder is replaced by the copper-silicon composite powder, and other components such as a binder, a solvent, etc. are unchanged, and the specific ratio is copper-silicon composite powder: epoxy resin E-51: curing agent: Solvent: Coupling agent = 55:20:1:23:1; the above materials were mixed, stirred uniformly, and finally formed into a conductive paste. The above conductive adhesive is applied by screen printing equipment, and a certain pattern of conductive adhesive is coated on the glass substrate, solidified and dried at 55 ° C, and finally its conductivity is measured, and its resistivity is 2.15×10 ^-7 Ω·m. The requirement of conductive adhesive is reached; the resistivity before replacement is 1.85×10 ^-7 Ω·m.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention. Any modification, modification, and equivalent structural transformation of the above embodiments in accordance with the technical spirit of the present invention are still the technical solutions of the present invention. The scope of protection.

Claims

A noble metal-silicon composite powder prepared by a galvanic reaction, which is produced by the following method:

(1) preparing a hydrofluoric acid solution having a concentration of 1-5 mol/L;

(2) adding the hydrofluoric acid solution prepared in the step (1) to the container containing the ultrafine silicon fine powder, and continuously stirring;

(3) preparing a solution containing precious metal ions at a concentration of 0.001-10 mol/L;

(4) adding the noble metal ion-containing solution in the step (3) to the hydrofluoric acid solution containing the ultrafine silicon micropowder prepared in the step (2); the galvanic reaction occurs, and the reaction time is 5-120 min. The surface of the ultrafine silicon micropowder is replaced by noble metal ions to form particles coated with a noble metal film on the surface of the ultrafine silicon micropowder; the weight ratio of precious metal ions participating in the reaction to the silicon is in the range of (10-1): (1-10);

(5) The ultrafine silicon fine powder coated with the noble metal film after the end of the reaction in the step (4) is centrifugally separated or filtered from the reaction system, washed, and dried to obtain a noble metal-silicon composite powder.
The noble metal-silicon composite powder prepared by the galvanic reaction according to claim 1, wherein the noble metal is gold, silver or copper.
The noble metal-silicon composite powder prepared by the galvanic reaction according to claim 1 or 2, wherein in the step (2), the ultrafine silicon micropowder is a band saw for processing a photovoltaic crystal silicon or a semiconductor silicon. The silicon scrap generated during the processing of the edge grinding, polishing, and multi-wire cutting machine, or the ultrafine metal silicon powder; the silicon scrap or the ultrafine metal silicon powder has a particle diameter of 0.5 to 5 μm.
The noble metal-silicon composite powder prepared by the galvanic reaction according to claim 1 or 2 or 3, wherein in the step (3), the noble metal ion-containing solution is an oxide or noble metal salt of a noble metal. The medium and strong acid are reacted and dissolved by adding water; according to different precious metal elements, the solution contains Au 4+ , Ag + or Cu 2+ , respectively .
The noble metal-silicon composite powder prepared by the galvanic reaction according to any one of claims 1 to 4, wherein in the step (3), the noble metal ion-containing solution is a chloroauric acid solution or a chloroauric acid salt. Solution, silver nitrate solution, silver fluoride solution, copper chloride solution, copper nitrate solution or copper sulfate solution.
The noble metal-silicon composite powder prepared by the galvanic reaction according to any one of claims 1 to 5, wherein, in the step (5), the precious metal-silicon composite powder accounts for 30-99 wt% of the precious metal. %.
Use of the noble metal-silicon composite powder according to any one of claims 1 to 6 for preparing a conductive material.
A conductive paste characterized in that the conductive paste contains the noble metal-silicon composite powder according to any one of claims 1 to 6.
A conductive ink for printing electrons, characterized in that the conductive ink contains the noble metal-silicon composite powder according to any one of claims 1 to 6.
A conductive paste, characterized in that the conductive paste contains the noble metal-silicon composite powder according to any one of claims 1 to 6.