CN115555557A - Preparation method of composite flake silver powder and low-resistance conductive paste containing silver powder - Google Patents

Abstract

The invention discloses a preparation method of composite flake silver powder, which comprises the steps of preparing basic silver powder with the average particle size of 0.3-3 mu m as a raw material, adding the raw material into a protective carrier, autorotation driving and grinding the raw material through a rotating shaft assembly with arms, carrying out cooling treatment, and finally carrying out separation post-treatment to obtain the composite flake silver powder containing flake silver powder and part of the basic silver powder, or the composite flake silver powder containing flake silver powder and a basic silver powder variant, or the composite flake silver powder containing flake silver powder, part of the basic silver powder and the basic silver powder variant. Compared with the traditional planetary ball mill preparation method, the preparation method of the composite flake silver powder has the advantages of high preparation efficiency, small loss, low energy consumption, stable and reliable quality, and is more suitable for batch production, especially batch one-time preparation and molding.

Description

Preparation method of composite flake silver powder and low-resistance conductive paste containing silver powder

Technical Field

The invention relates to a preparation method of flake silver powder and conductive paste containing the flake silver powder, in particular to a preparation method of composite flake silver powder and low-resistance conductive paste containing the composite flake silver powder.

Background

With the rapid development of information technology, new patterns of world development are continuously remodeled. Under the background of a new era, semiconductor devices and electronic information products are developing towards high performance, strong functionalization, environmental protection, miniaturization, thinning and light weight, for example, indexes such as solar cell conversion efficiency, polycrystalline silicon solar cell conversion efficiency, monocrystalline silicon solar cell conversion efficiency, lower limit value of thin-film solar cell conversion efficiency and the like, and higher requirements are also put forward on conductive paste widely applied to the devices or products.

The conductive phase adopted in the conductive paste is a key factor of the conversion efficiency of the solar cell, and the conductive phase required in the common high-performance conductive paste is mainly silver powder. The silver powder has various shapes, and the silver powder used by the conductive silver paste generally has two categories, namely flake silver powder and spherical silver powder, and the performance indexes of the flake silver powder and the spherical silver powder have great difference, so that the performances of the silver paste in various aspects such as thixotropy, viscosity, conductivity, adhesion rate and the like are directly influenced.

At present, the flake silver powder is generally considered to have larger specific surface area and more excellent electrical conductivity compared with the spherical silver powder, because the spherical silver powder is stacked in a way that spheres are in point contact, the stacking system of the flake silver powder is in radial directional stacking, the flake silver powder has quite a lot of stacking in a way that surfaces are stacked layer by layer except point contact, and because the surface contact has a larger flow pipeline than the point contact, phonons and electrons can easily pass through the surface contact, so that the thermal resistance and the electrical resistance are greatly reduced, and the flake silver powder has excellent heat transfer and electrical conductivity characteristics in a specific direction and stable chemical properties.

The powder of the existing flake silver powder is still too thick and has small tap density, so that the filling amount of the flake silver powder in the conductive paste is insufficient, the conductivity and the printing performance of the conductive paste are poor, the conductivity of the sintered conductive paste after sintering and forming is limited, and the conductive paste has the defects of low process forming efficiency, small batch production amount and the like, so that the application value of the flake silver powder in the industrial production of low-temperature curing conductive paste and sintered conductive paste is limited, and the flake silver powder is particularly applied to semiconductors and electronics with high added value.

At present, the flake silver powder and the spherical silver powder are commonly matched and applied to the conductive silver paste, so that on one hand, the oil absorption of the flake silver powder is relatively increased based on the high specific surface area of the flake silver powder, and the thixotropy and viscosity of the finished silver paste are changed; on the other hand, the spherical silver powder is small in particle size and is filled into gaps of the flaky silver powder, so that the conductivity of the finished silver paste is improved; and finally, the preparation of the high-performance conductive silver paste is realized by combining the control design of the silver powder content and the ball-to-chip ratio.

However, the flake silver powder and the spherical silver powder used in the existing conductive silver paste are simply physically mixed during batching, and because the material properties and application requirements of single components and mixed components of the silver powder are still different, and the mixing preparation conditions are relatively complicated, improvement is still needed.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a preparation method of composite flake silver powder, and the invention aims to provide low-resistance conductive paste containing the composite flake silver powder, so that the prepared high-performance silver powder can meet the high requirements of conductive silver paste on conductive phase silver powder, and has the characteristics of simple manufacturing process, high forming efficiency and suitability for industrial batch production.

The technical scheme is as follows: a preparation method of composite flake silver powder comprises the following steps:

s10, preparing base silver powder with the average grain diameter of 0.3-3 mu m as a raw material, and adding the raw material into a protective carrier;

and S20, carrying out autorotation driving grinding on the mixture obtained in the step S10 through the arm-provided rotating shaft assembly, carrying out cooling treatment, and finally carrying out separation post-treatment to obtain the composite flake silver powder containing the flake silver powder and part of the basic silver powder, or the composite flake silver powder containing the flake silver powder and a basic silver powder deformation body, or the composite flake silver powder containing the flake silver powder and part of the basic silver powder and the basic silver powder deformation body.

Furthermore, the grinding rotating speed of the rotating shaft assembly with the arm is set to be 80-300 r/min, and the grinding time is set to be 1-6 h.

Further, the rotation axis of the arm-carrying rotary shaft assembly is set to an angle of not more than 50 ° from the vertical.

Furthermore, the temperature of the cooling medium adopted in the cooling treatment is not more than 10 ℃, and preferably 2-10 ℃.

Further, in step S20, the mixture of step S10 is premixed before being autorotated, driven and ground by the rotating shaft assembly with arms, the premixing rotating speed is 10 to 100r/min, and the premixing time is not more than 1h.

Further, the protective carrier comprises a solvent A and a protective agent, wherein the base silver powder serving as the raw material and the solvent A are mixed according to the mass ratio of 15-25: 4-6, and the base silver powder serving as the raw material and the protective agent are mixed according to the mass ratio of 500: 6-9.

Further, the solvent A is one or a mixture of more than two of absolute ethyl alcohol, acetone and deionized water, and the protective agent is one or a mixture of two of saturated fatty acids and unsaturated fatty acids.

Further, the base silver powder as the raw material includes one or a mixture of at least two of a spherical silver powder, an irregular silver powder, and a silver powder of a flocculent shape.

Further, the average particle size of 0.3 to 3 μm is composed of a single particle size or a mixture of different particle sizes.

Further, the post-separation treatment refers to solid-liquid separation and drying treatment, or solid-liquid separation, drying and screening treatment.

Furthermore, the mass ratio of the flaky silver powder is not less than 10% and less than 100% based on 100% of the mass of the prepared composite flaky silver powder.

A low-resistance conductive paste is prepared from raw materials including an organic carrier and the composite flaky silver powder prepared by any one of the preparation methods, wherein the composite flaky silver powder and the organic carrier are mixed according to the mass ratio of 60-90: 5-70 to prepare a low-temperature curing type low-resistance conductive paste;

or the preparation raw materials comprise an organic carrier and glass powder, and the composite flaky silver powder prepared by any one of the preparation methods, wherein the composite flaky silver powder, the glass powder and the organic carrier are mixed according to the mass ratio of 30-90: 1-20: 5-65 to prepare the sintered low-resistance conductive paste.

Furthermore, the preparation raw materials also comprise additives, and the mass of the additives accounts for 0.1-10% of the total mass of the preparation raw materials as 100%.

Further, the organic carrier comprises a solvent B and organic resin, wherein the organic resin accounts for 6-30% of the total mass of the organic carrier by 100%;

the solvent B is one or the mixture of more than two of terpineol, tributyl citrate, diethylene glycol butyl ether acetate, diethylene glycol dibutyl ether, diethylene glycol butyl ether, DBE, alcohol ester twelve, 2, 4-trimethyl-1, 3-pentanediol diisobutyrate, triethylene glycol, tripropylene glycol methyl ether, hexanediol monobutyl ether, butyl carbitol acetate, gamma-butyrolactone, N' -dimethyl amine acetate and alpha-terpineol, dimethyl adipate, dimethyl glutarate, ethylene glycol phenyl ether and 3-hydroxy-1, 3, 5-pentanedioic acid;

one of the raw materials of the low-temperature curing type low-resistance conductive paste is organic resin which is one or more than two of polyvinyl chloride, polyurethane, phenolic resin, epoxy resin, acrylic resin, organic silicon resin, unsaturated polyester, ethyl cellulose and PVB;

one of the raw materials of the sintered low-resistance conductive paste is one or more of cellulose, ethylene, polyacrylic acid, polypropylene ester, polyethylene oxide, polypropylene oxide, polyethylene glycol, phenolic resin, acrylic resin, polyvinyl butyral resin, rosin resin and derivatives thereof.

Has the advantages that: the invention has the advantages that: compared with the traditional planetary ball mill preparation method, the preparation method of the composite flake silver powder has the advantages of high preparation efficiency, small loss, low energy consumption, stable and reliable quality, and is more suitable for mass production, especially for mass one-step preparation and forming, and the components of the composite flake silver powder enable the conductive paste to be applied to the conductive paste to have good printability, low resistivity, high mass production efficiency and effectively reduce the production and manufacturing cost.

Drawings

FIG. 1 is a scanning electron micrograph of a silver powder C3 as a base in example 3.

Detailed Description

The invention is further elucidated with reference to the drawings and the embodiments.

Method for preparing first part composite flake silver powder

A method for preparing composite flaky silver powder comprises the steps of premixing a mixture of basic silver powder and a protective carrier serving as raw materials, grinding the mixture through autorotation driving of a rotation shaft assembly with an arm, cooling the mixture, and finally separating and processing the mixture to obtain the composite flaky silver powder containing flaky silver powder and partial basic silver powder, or the composite flaky silver powder containing flaky silver powder and a deformation body of the basic silver powder, or the composite flaky silver powder containing flaky silver powder, partial basic silver powder and a deformation body of the basic silver powder.

The base silver powder as the raw material includes one or a mixture of at least two of spherical silver powder, irregular silver powder, and flocculent silver powder. "spherical silver powder" means silver powder including regular spherical and irregular spheroidal structures, and also includes silver powder having a porous spherical or spheroidal structure, and also includes silver powder having a dendritic spheroidal structure; "irregular silver powder" means silver powder having a structure like a block, a polyhedron, or the like; the "silver powder of a flocculent shape" means a silver powder of a chain-like structure in which particles are arranged and bonded to each other. In actual production, the single-form base silver powder can be prepared by mechanical pulverization or chemical synthesis.

The average particle size of the base silver powder as a raw material is 0.3 to 3 μm, and may be composed of a single particle size, or may be composed of a mixture of at least two types of single particle sizes, such as a mixture, which may be obtained by simple physical mixing, or may be a value in which the base silver powder is formed during the production process and the average particle size is determined by analysis.

The protective carrier comprises a solvent A and a protective agent, wherein the base silver powder serving as a raw material is mixed with the solvent A according to the mass ratio of 15-25: 4-6, and the base silver powder serving as a raw material is mixed with the protective agent according to the mass ratio of 500: 6-9. The solvent A includes absolute ethyl alcohol, acetone, deionized water and the like, and can be one or a mixture of more than two of the solvents. The variety of the protective agent comprises saturated fatty acids and unsaturated fatty acids, and can be one or two of the saturated fatty acids and the unsaturated fatty acids, specifically, the variety of the saturated fatty acids comprises caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid and the like, the variety of the unsaturated fatty acids comprises monounsaturated fatty acids or polyunsaturated fatty acids, wherein the variety of the monounsaturated fatty acids comprises oleic acid, trans-oleic acid, erucic acid and the like, the variety of the polyunsaturated fatty acids comprises linoleic acid, linolenic acid, arachidonic acid and the like, the protective agent can be one or at least two of the lower varieties of the saturated fatty acids, can also be one or at least two of the lower varieties of the unsaturated fatty acids, and can also be a mixture of at least one of the lower varieties of the saturated fatty acids and at least one of the lower varieties of the unsaturated fatty acids.

The mixture can be premixed and then is subjected to autorotation driving grinding through the rotating shaft assembly with the arm.

The premixing rotating speed is 10-100 r/min, the premixing time is not more than 1h, and 30-80 r/min and not more than 0.5h are the best. The premixing is an optional step in the preparation process, the composite flake silver powder can be prepared whether the mixture is premixed or not, and compared with the composite flake silver powder prepared without premixing, the composite flake silver powder prepared by premixing has better product uniformity and more balanced and stable product performance. The premixing can be an independent stirring and mixing process, or can be low-speed transient stirring and mixing by adopting subsequent grinding equipment driven by the autorotation of the rotating shaft assembly with the arm, or can be combined with the low-speed transient stirring and mixing process, and the premixing effect is limited by not forming a grinding effect, namely, the initial form and structure of the base silver powder are not damaged.

The rotation axis component with the arm extends into the inner cavity of the grinding tank, the rotation axis of the rotation axis component is coincident with or parallel to or forms a certain included angle with the axis position of the grinding tank, and the rotation axis component can drive materials to move in the inner cavity of the grinding tank in a self-rotation mode. When the included angle is formed, the rotating axis of the rotating shaft component with the arm is set to be not more than 50 degrees with the vertical direction. The rotation shaft assembly with the arm can also move in the inner cavity of the grinding tank according to a set track, such as circular motion, spiral motion and the like. The grinding rotating speed of the rotating shaft assembly with the arm is set to be 80-300 r/min, and the grinding time is set to be 1-6 h.

The temperature of the cooling medium adopted in the cooling and temperature reduction treatment is not more than 10 ℃, and is preferably 2-10 ℃, and the cooling medium comprises one or the mixture of at least two of cooling water, cooling air and cooling oil. The post-separation treatment refers to solid-liquid separation and drying treatment, and can also comprise post-treatment such as screening and the like after the drying treatment.

A part of the base silver powder contained in the produced composite silver flake, which is a part of the base silver powder as a raw material, is an original component having an original form and structure that is retained in the case where the base silver powder as a raw material is insufficiently ground.

The following examples, based on the above parameters, were selected.

Example 101

The preparation method of the composite flake silver powder specifically comprises the following steps:

step S10, preparing spherical silver powder C1 having an average particle diameter of 0.5 μm and a specific surface area of 0.10g/m as a raw material ² 。

And S20, selecting a vertical grinder which is provided with a grinding tank and an arm-provided rotating shaft assembly, wherein the arm-provided rotating shaft assembly extends into an inner cavity of the grinding tank, the rotating shaft of the arm-provided rotating shaft assembly is in the vertical direction and is coincided with the central axis of the grinding tank, cooling treatment is carried out on the outer wall of the inner cavity of the grinding tank of the vertical grinder by starting cooling water circulation, and the temperature of the cooling water is set to be 10 ℃.

Weighing 80g of stearic acid, and adding 1000g of absolute ethyl alcohol to prepare a protective carrier E1; weighing 5kg of spherical silver powder C1, adding the spherical silver powder C1 into an inner cavity of a grinding tank of a vertical grinding machine, adding a protective carrier E1 and grinding balls, and stirring and premixing the arm-mounted rotating shaft assembly for 5min at a rotating speed of 80 r/min.

And step S30, starting a grinding procedure, grinding the arm-provided rotating shaft assembly of the vertical grinding machine for 1h at the rotating speed of 100r/min, closing the vertical grinding machine after grinding is finished, pouring out the materials in the inner cavity of the grinding tank, and performing solid-liquid separation and drying to obtain the composite flake silver powder F1 consisting of the flake silver powder and the spherical silver powder, wherein the spherical silver powder in the product is part of the spherical silver powder C1 serving as the raw material and is an original component with an initial form and a structure reserved under the condition that the grinding of the spherical silver powder C1 serving as the raw material is insufficient.

Example 102

A preparation method of composite flake silver powder specifically comprises the following steps:

step S10, preparing a silver powder C2 of flocculent form having an average particle diameter of 1 μm and a specific surface area of 0.50g/m as a raw material ² 。

Step S20, the vertical mill of embodiment 101 is selected, and the cooling water and the cooling air are circulated to cool the outer wall of the inner cavity of the grinding tank of the vertical mill, where the temperature of the cooling medium is set to 10 ℃.

Weighing 70g of decanoic acid, and adding 1000g of absolute ethyl alcohol to prepare a protective carrier E2; 5kg of flocculent silver powder C2 is weighed and added into an inner cavity of a grinding tank of a vertical grinding machine, a protective carrier E2 and grinding balls are added, and a rotating shaft assembly with an arm is stirred and premixed for 30min at the rotating speed of 50 r/min.

And step S30, starting a grinding procedure, grinding the arm-mounted rotating shaft assembly of the vertical grinding machine for 1 hour at the rotating speed of 120r/min, closing the vertical grinding machine after grinding is finished, pouring out the materials in the inner cavity of the grinding tank, and performing solid-liquid separation and drying to obtain the composite flake silver powder F2 consisting of the flake silver powder and the flocculent silver powder, wherein the flocculent silver powder in the product is a part of the flocculent silver powder C2 serving as the raw material and is an original component with an initial form and a structure reserved under the condition that the flocculent silver powder C2 serving as the raw material is not fully ground.

Example 103

A preparation method of composite flake silver powder specifically comprises the following steps:

step S10, preparing an irregular silver powder having an average particle diameter of 2 μm and a spherical silver powder as a raw material to constitute a base silver powder C3 (shown in FIG. 1) having a specific surface area of 0.25g/m in a certain ratio ² 。

Step S20, an inclined grinder is selected, which is different from the vertical grinder of embodiment 1 in that: the grinding tank and the rotary shaft assembly with the arm are integrally inclined, and the inclined rotary shaft forms an included angle of 30 degrees with the vertical direction. And starting cooling water and cooling air double circulation to cool the outer wall of the inner cavity of the grinding tank of the inclined grinding machine, wherein the temperature of a cooling medium is set to be 8 ℃.

Weighing 40g of stearic acid and 20g of decanoic acid, and adding 1000g of deionized water to prepare a protective carrier E3; weighing 5kg of basic silver powder C3, adding the basic silver powder C3 into an inner cavity of a grinding tank of an inclined grinding machine, adding a protective carrier E3 and grinding balls, and stirring and premixing the rotation shaft assembly with the arm at the rotation speed of 30r/min for 1h.

And S30, starting a grinding procedure, grinding the rotation shaft assembly with the arm of the inclined grinding machine for 2 hours at the rotation speed of 250r/min, closing the inclined grinding machine after grinding is finished, pouring out the materials in the inner cavity of the grinding tank, and performing solid-liquid separation, drying and screening to obtain the composite flake silver powder F3 consisting of the flake silver powder and the irregular silver powder, wherein the irregular silver powder in the product is a part of the irregular silver powder in the basic silver powder C3 serving as the raw material and is an original component with an initial form and a structure reserved under the condition that the grinding of the irregular silver powder in the basic silver powder C3 serving as the raw material is insufficient.

Example 104

A preparation method of composite flake silver powder specifically comprises the following steps:

step S10, spherical silver powder C4 having an average particle diameter of 3 μm and a specific surface area of 0.37g/m was prepared as a raw material ² 。

Step S20, selecting the inclined grinding mill of embodiment 103, starting cooling water and cooling air dual cycle to cool the outer wall of the inner cavity of the grinding tank of the inclined grinding mill, and setting the temperature of the cooling medium to 8 ℃.

Weighing 85g of stearic acid, and adding 1000g of deionized water to prepare a protective carrier E4; weighing 5kg of spherical silver powder C4, adding the spherical silver powder C4 into an inner cavity of a grinding tank of an inclined grinding machine, adding a protective carrier E4 and grinding balls, and stirring and premixing the arm-mounted rotating shaft assembly for 30min at a rotating speed of 50 r/min.

And S30, starting a grinding procedure, grinding the rotation shaft assembly with the arm of the inclined grinding machine for 1h at the rotation speed of 150r/min, closing the inclined grinding machine after grinding is finished, pouring out the materials in the inner cavity of the grinding tank, and performing solid-liquid separation, drying and screening to obtain the composite flake silver powder F4 consisting of the flake silver powder and the spherical silver powder, wherein the spherical silver powder in the product is part of the spherical silver powder C4 serving as the raw material and is an original component with an initial shape and a structure reserved under the condition that the grinding of the spherical silver powder C4 serving as the raw material is insufficient.

Example 105

A preparation method of composite flake silver powder specifically comprises the following steps:

step S10, spherical silver powder C5 having an average particle diameter of 1.5 μm and a specific surface area of 0.40g/m was prepared as a raw material ² 。

Step S20, the vertical grinding machine of embodiment 101 is selected, and cooling water circulation is started to cool the outer wall of the grinding tank inner cavity of the vertical grinding machine, where the temperature of the cooling water is set to 5 ℃.

Weighing 90g of stearic acid, and adding 1000g of absolute ethyl alcohol to prepare a protective carrier E5; weighing 5kg of spherical silver powder C5, adding the spherical silver powder C5 into an inner cavity of a grinding tank of a vertical grinding machine, adding a protective carrier E5 and grinding balls, and stirring and premixing the rotating shaft assembly with the arm at the rotating speed of 30r/min for 1h.

And step S30, starting a grinding procedure, grinding the arm-mounted rotating shaft assembly of the vertical grinding machine for 2.5 hours at the rotating speed of 150r/min, closing the vertical grinding machine after grinding is finished, pouring out the materials in the inner cavity of the grinding tank, and performing solid-liquid separation and drying to obtain the composite flake silver powder F5 consisting of the flake silver powder, the spherical silver powder and a spherical silver powder deformation body (such as a cake), wherein the spherical silver powder in the product is part of the spherical silver powder C5 serving as a raw material and is an original component with an initial form and a structure reserved under the condition that the grinding of the spherical silver powder C5 serving as the raw material is insufficient.

Example 106

A preparation method of composite flake silver powder specifically comprises the following steps:

step S10, preparing spherical silver powder C6 having an average particle diameter of 1.5 μm and a specific surface area of 0.40g/m as a raw material ² 。

Step S20, the vertical grinding machine of embodiment 101 is selected, and cooling oil circulation is started to cool the outer wall of the inner cavity of the grinding tank of the vertical grinding machine, where the temperature of the cooling oil is set to 5 ℃.

Weighing 70g of stearic acid, and adding 1000g of absolute ethyl alcohol to prepare a protective carrier E6; weighing 5kg of spherical silver powder C6, adding the spherical silver powder C6 into an inner cavity of a grinding tank of a vertical grinding machine, adding a protective carrier E6 and grinding balls, and stirring and premixing a rotating shaft assembly with an arm at the rotating speed of 30r/min for 1h.

And step S30, starting a grinding procedure, grinding the arm-mounted rotating shaft assembly of the vertical grinding machine for 3 hours at the rotating speed of 150r/min, closing the vertical grinding machine after grinding is finished, pouring out the materials in the inner cavity of the grinding tank, and performing solid-liquid separation and drying to obtain the composite flaky silver powder F6 consisting of the flaky silver powder, the spherical silver powder and a spherical silver powder deformation body (such as a cake), wherein the spherical silver powder in the product is part of the spherical silver powder C6 serving as a raw material and is an original component with an initial form and a structure reserved under the condition that the grinding of the spherical silver powder C6 serving as the raw material is insufficient.

Example 107

The preparation method of the composite flake silver powder specifically comprises the following steps:

step S10, preparing spherical silver powder C7 having an average particle diameter of 1.5 μm and a specific surface area of 0.40g/m as a raw material ² 。

Step S20, selecting the vertical mill of embodiment 101, starting cooling water circulation to cool the outer wall of the grinding tank cavity of the vertical mill, and setting the temperature of the cooling water to 10 ℃.

Weighing 80g of stearic acid, and adding 1000g of absolute ethyl alcohol to prepare a protective carrier E7; weighing 5kg of spherical silver powder C7, adding the spherical silver powder C7 into an inner cavity of a grinding tank of a vertical grinding machine, adding a protective carrier E7 and grinding balls, and stirring and premixing a rotating shaft assembly with an arm at the rotating speed of 30r/min for 1h.

And step S30, starting a grinding procedure, grinding the arm-equipped rotating shaft assembly of the vertical grinding machine for 4 hours at the rotating speed of 150r/min, closing the vertical grinding machine after grinding is finished, pouring out the materials in the inner cavity of the grinding tank, carrying out solid-liquid separation and drying to obtain the composite flaky silver powder F7 consisting of the flaky silver powder, the spherical silver powder and spherical silver powder deformation bodies (such as cakes and irregular structures), wherein the spherical silver powder in the product is part of the spherical silver powder C7 serving as the raw material and is an original component with an initial shape and structure reserved under the condition that the grinding of the spherical silver powder C7 serving as the raw material is insufficient.

Example 108

A preparation method of composite flake silver powder specifically comprises the following steps:

step S10, spherical silver powder C8 having an average particle diameter of 1.5 μm and a specific surface area of 0.40g/m was prepared as a raw material ² 。

Step S20, the vertical grinding machine of embodiment 101 is selected, and cooling water circulation is started to cool the outer wall of the grinding tank inner cavity of the vertical grinding machine, where the temperature of the cooling water is set to 10 ℃.

Weighing 85g of stearic acid, and adding 1000g of absolute ethyl alcohol to prepare a protective carrier E8; weighing 5kg of spherical silver powder C8, adding the spherical silver powder C8 into an inner cavity of a grinding tank of a vertical grinding machine, adding a protective carrier E8 and grinding balls, and stirring and premixing the rotary shaft assembly with the arm at the rotating speed of 50r/min for 30min.

And step S30, starting a grinding procedure, grinding the arm-equipped rotating shaft assembly of the vertical grinding machine for 4 hours at the rotating speed of 200r/min, closing the vertical grinding machine after grinding is finished, pouring out the materials in the inner cavity of the grinding tank, and carrying out solid-liquid separation and drying to obtain the composite flaky silver powder F8 consisting of the flaky silver powder, the spherical silver powder and spherical silver powder deformation bodies (such as cakes and irregular structures), wherein the spherical silver powder in the product is part of the spherical silver powder C8 serving as the raw material and is an original component with an initial shape and structure reserved under the condition that the spherical silver powder C8 serving as the raw material is not sufficiently ground.

Example 109

A preparation method of composite flake silver powder specifically comprises the following steps:

step S10, preparing spherical silver powder C9 having an average particle diameter of 1.5 μm and a specific surface area of 0.53g/m as a raw material ² 。

Step S20, the inclined grinding mill of embodiment 103 is selected, an included angle between the inclined rotation axis and the vertical direction is set to 45 °, cooling water and cooling air are started to perform a dual cycle cooling treatment on the outer wall of the inner cavity of the grinding tank of the inclined grinding mill, and the temperature of the cooling medium is set to 5 ℃.

Weighing 60g of stearic acid, and adding 1000g of deionized water to prepare a protective carrier E9; weighing 5kg of spherical silver powder C9, adding the spherical silver powder C9 into an inner cavity of a grinding tank of an inclined grinding machine, adding a protective carrier E9 and grinding balls, and stirring and premixing the arm-mounted rotating shaft assembly for 0.5min at a rotating speed of 50 r/min.

And step S30, starting a grinding procedure, grinding the rotation shaft assembly with the arm of the inclined grinding machine for 4.5 hours at the rotation speed of 200r/min, closing the inclined grinding machine after grinding is finished, pouring out the materials in the inner cavity of the grinding tank, and carrying out solid-liquid separation, drying and screening to obtain the composite flake silver powder F9 consisting of the flake silver powder, the spherical silver powder and spherical silver powder deformation bodies (such as cakes and irregular structures), wherein the spherical silver powder in the product is part of the spherical silver powder C9 serving as a raw material and is an original component with an initial form and a structure reserved under the condition that the spherical silver powder C9 serving as the raw material is not sufficiently ground.

Example 1010

A preparation method of composite flake silver powder specifically comprises the following steps:

step S10, preparing spherical silver powder C10 having an average particle diameter of 1.5 μm and a specific surface area of 0.60g/m as a raw material ² 。

Step S20, selecting the inclined grinding mill of embodiment 103, setting an included angle between the inclined rotation axis and the vertical direction to be 45 °, starting cooling water circulation to cool the outer wall of the inner cavity of the grinding tank of the inclined grinding mill, and setting the temperature of the cooling water to be 10 ℃.

Weighing 35g of stearic acid and 35g of decanoic acid, and adding 1000g of deionized water to prepare a protective carrier E10; weighing 5kg of spherical silver powder C10, adding the spherical silver powder C10 into an inner cavity of a grinding tank of an inclined grinding machine, adding a protective carrier E10 and grinding balls, and stirring and premixing a rotating shaft assembly with an arm at a rotating speed of 50r/min for 30min.

And step S30, starting a grinding procedure, grinding the armed rotating shaft assembly of the inclined grinding machine for 5 hours at the rotating speed of 200r/min, closing the inclined grinding machine after grinding is finished, pouring out the materials in the inner cavity of the grinding tank, and carrying out solid-liquid separation, drying and screening to obtain the composite flaky silver powder F10 consisting of the flaky silver powder and spherical silver powder deformation bodies (such as cakes and irregular structures).

Comparative example 101

Except for replacing the vertical mill with a planetary ball mill in example 101, the same operation as in example 101 was carried out to obtain a composite silver flake FF1.

Comparative example 102

Except for replacing the vertical mill with a planetary ball mill in example 102, the same operation as in example 102 was carried out to obtain a composite silver flake FF2.

Comparative example 103

The only difference from example 103 is that stearic acid and decanoic acid, which are protective agents in the protective carrier, are removed, and the same operation as in example 103 is performed, but during the trial production: because of lacking the protective agent, the silver powder infiltration degree is not enough, and the reunion is piled up into the piece, appears the phenomenon such as seam, adherence, and the resistance is big, and the rotation axis subassembly of taking the arm can't stir all mixture materials and grind, can only drive the peripheral a small amount of material that is in central point of rotation axis subassembly of taking the arm and move, can't stir at all even.

Comparative example 104

The only difference from example 105 is that the cooling treatment was removed, and the same operation as in example 105 was performed, and the trial results show that: a large amount of heat is generated in the grinding process, so that the particles grow abnormally, and further the phenomena of welding, adherence and the like occur, the particle size distribution, the tap density and the like of the powder are all deteriorated, and the composite flaky silver powder with expected performance cannot be obtained.

The composite plate-like silver powder products prepared in examples 101 to 1010 and comparative examples 101 to 102 were subjected to the test performance shown in table 1 for comparison:

TABLE 1

Examples 101 to 1010 exemplify specific processes of the method for preparing the composite plate-like silver powder, and performance test data of the prepared composite plate-like silver powder product, and exemplify the specific processes, the different compositions, the different morphologies, the types and the ratios of protective carriers, premixing parameters, cooling parameters, and grinding parameters, of the base silver powder used as a raw material.

The test performance data in table 1 was analyzed as follows:

1. the composite flake silver powder prepared in examples 101 to 1010 exhibited excellent physicochemical properties, narrow particle size distribution, sharp and steep single peak, D50 particle size as low as 0.6 μm, and tap density of 4.3 to 6.2g/cm ³ The specific surface area is basically between 0.8 and 1.5m ² The burning loss is 0.1-0.5 percent per gram.

2. In the examples 101 to 103, the basic silver powder as the raw material can be spherical, flocculent, irregular and spherical mixed, and in other examples, the basic silver powder can be irregular, spherical and flocculent mixed, flocculent and irregular mixed, or spherical, flocculent and irregular mixed.

3. The average particle diameter of the base silver powder as the raw material may be 0.3 μm, 0.4 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, etc., and may be any other value between 0.3 and 3 μm, in addition to those exemplified in the examples. The raw silver powder with the average particle size of less than 0.3 mu m is difficult to prepare and high in industrial application cost; the silver powder with the average particle size of more than 3 mu m is a raw material silver powder, the flake silver powder meeting the high-performance application is difficult to process by a single one-step method, the difficulty of production efficiency, quality control and manufacturing cost is undoubtedly increased by adopting multi-step processing treatment, and therefore the basic silver powder with the average particle size of 0.3-3 mu m is preferably selected as the raw material.

4. The premixing parameters, the grinding parameters, the rotating speed and the time are a group of matching parameters, the premixing aims to preliminarily stir and mix the mixture material, the grinding is to form flake silver powder by utilizing high-speed collision, shearing movement and the like between the basic silver powder and the basic silver powder, grinding balls, the wall of a grinding tank and a rotating shaft assembly with an arm, the premixing rotating speed and the time are set to ensure that the grinding effect is not caused, only the effect of physical uniform mixing is achieved, the rotating speed is not too high, and the time is not too long; the premixing step may also be omitted, if necessary, or performed separately. According to the general understanding, the uniform premixing of the materials helps to protect the uniform infiltration of the carrier, which is beneficial to the milling effect, and the milling balls in the preparation method of the composite flake silver powder can be added during milling.

In addition to the examples, the polishing rate may be any other value between 80 to 100r/min, 100 to 120r/min, 120 to 150r/min, 150 to 200r/min, or 200 to 300r/min, and the polishing time may be adjusted to the polishing rate and the desired flaking degree.

5. The specific surface area and tap density of the composite flake silver powder prepared by the method are related to the specific surface area and tap density of the base silver powder as a raw material, and other influence factors such as grinding speed, grinding time and the like are also more. For example, in general, the base silver powder is converted into the plate-like silver powder, and the specific surface area becomes large, and the higher the grinding rate and the longer the grinding time are, the larger the specific surface area is. As can be seen from examples 105 to 1010, when the average particle size of the base silver powder used as the raw material was the same, the higher the milling rate and the longer the milling time, the higher the flaking degree, but when the milling rate was less than the critical value, the flaking effect did not occur even if the milling time was longer, and the higher the milling rate, the higher the requirement for the milling equipment, the higher the cost, and the longer the milling time, the influence on the production efficiency and the energy consumption, and therefore, the milling rate and the milling time are appropriately selected in the present application.

6. Comparative examples 101 to 102 are obtained by respectively replacing the neutral grinding mills in examples 101 to 102 with a conventional planetary ball mill and performing processing under the same conditions, and from comparison of two test performances, the particle size distribution, particle size, tap density, specific surface area and the like are equivalent, but the flaking degree is significantly different, the mass ratio of the flaked silver powder in the prepared composite flaked silver powder is 10% in example 101, 3% in corresponding comparative example 101, 12% in example 102 and 5% in corresponding comparative example 102, and the grinding efficiency of the vertical grinding mill is far better than that of the planetary ball mill under the requirement of the same flaking degree, and the energy consumption is increased along with the long-time grinding of the planetary ball mill, and the formed flaked silver powder has larger particles, smaller tap density and larger specific surface area than those of the vertical grinding mill, so that the printability of the conductive paste is blocked, the conductive paste is difficult to densify and accumulate, the performance improvement space of the conductive paste is even deteriorated, and the design and processing difficulty is large, and the cost is high.

7. As can be seen from the comparison between example 103 and comparative example 103, in the preparation method of the composite flake silver powder, the solvent and the protective agent are used for wetting and coating modification during the wet grinding process, so as to improve the dispersibility. The main reason is that in order to meet the performance design requirement of the composite flake silver powder, the average particle size of the basic silver powder as the raw material is selected within a certain smaller range, the particle size is small, the specific surface area is large, and the particles can be accumulated, overlapped, agglomerated and flaky during the preparation process of the composite flake silver powder, so that the welding phenomenon occurs, and the particle size of the flake silver powder exceeds the expected use value. In the preparation process of comparative example 103, since no protective agent was used, the silver powder having a small particle size was not effectively infiltrated and dispersed, agglomerated and piled up, and could not be ground with stirring, and thus it was difficult to put into use.

In other exemplary embodiments, the grinding speed, the premixing parameters, the cooling temperature, the included angle between the rotation axis and the vertical direction and the like are also adjusted, and the results show that the composite flake silver powder wet grinding process needs to use the protective agent.

8. As can be seen from the comparison between the example 105 and the comparative example 104, in the preparation method of the composite flake silver powder, the wet grinding is adopted, and the cooling treatment is matched, so that the heat generated in the high-speed collision process of the material is prevented from being transferred to the material, the self-growth of the particle size is avoided, the particle size exceeds the expected size, the uneven distribution and the abnormal large particles are formed, and the conductivity of the final silver conductive layer is influenced. From the trial production process of comparative example 104, it was found that in the case where the cooling treatment was not employed, similarly to the case where the protecting agent was not added in comparative example 103, the result of non-grindability occurred.

Except for the example of the comparative example 104, the adjustment of the grinding speed, the grinding time, the premixing parameters and the like based on the preparation parameters of the comparative example 104 also fails to successfully grind, and the result shows that the wet grinding process of the composite flake silver powder needs to be synchronously cooled.

Second part of low-resistance conductive paste

The composite flake silver powder prepared by the preparation method is usually used in conductive paste as a conductive phase and mixed with one or at least two of glass powder, resin, solvent, various additives and the like to prepare the conductive paste.

When the low-temperature curing type low-resistance conductive paste is prepared, the preparation raw materials comprise an organic carrier and the composite flaky silver powder prepared by the preparation method of the composite flaky silver powder, the composite flaky silver powder and the organic carrier are mixed according to the mass ratio of 60-90: 5-70, and the paste can also comprise an additive, wherein the additive accounts for 0.1-10% of the total mass of the preparation raw materials. The preparation process comprises the steps of weighing the raw materials according to the proportion, and then mixing, infiltrating, dispersing and grinding the raw materials to obtain the composite material.

When the sintered low-resistance conductive paste is prepared, the preparation raw materials comprise an organic carrier, glass powder and the composite flaky silver powder prepared by the preparation method of the composite flaky silver powder, the glass powder and the organic carrier are mixed according to the mass ratio of 30-90: 1-20: 5-65, and the sintered low-resistance conductive paste can also comprise an additive, wherein the additive accounts for 0.1-10% of the total mass of the preparation raw materials. The preparation process comprises the steps of weighing the raw materials according to the proportion, and then mixing, infiltrating, dispersing and grinding the raw materials to obtain the composite material.

The organic vehicle comprises a solvent B and organic resin, wherein the organic resin accounts for 6-30% of the total mass of the organic vehicle as 100%. The solvent B is one or the mixture of more than two of terpineol, tributyl citrate, diethylene glycol butyl ether acetate, diethylene glycol dibutyl ether, diethylene glycol butyl ether, DBE, alcohol ester twelve, 2, 4-trimethyl-1, 3-pentanediol diisobutyrate, triethylene glycol, tripropylene glycol methyl ether, hexanediol monobutyl ether, butyl carbitol acetate, gamma-butyrolactone, N' -dimethylacetic acid amine and alpha-terpineol, dimethyl adipate, dimethyl glutarate, ethylene glycol phenyl ether and 3-hydroxy-1, 3, 5-pentanedioic acid.

The low-temperature curing type low-resistance conductive paste adopts one or more than two of organic resin such as polyvinyl chloride, polyurethane, phenolic resin, epoxy resin, acrylic resin, organic silicon resin, unsaturated polyester, ethyl cellulose and PVB, and the additive is one or at least two of functional additives such as a thixotropic agent, a curing agent, a dispersing agent and the like.

The organic resin adopted by the sintering type low-resistance conductive paste is one or more than two of cellulose, ethylene, polyacrylic acid, polypropylene ester, polyethylene oxide, polypropylene oxide, polyethylene glycol, phenolic resin, acrylic resin, polyvinyl butyral resin, rosin resin and derivatives thereof, and the additive is one or more than two of thixotropic agent, curing agent, dispersing agent, sintering aid and other functional aids.

The glass frit may be a Si-Mg-Bi system or a Bi-Si-B system.

The prepared low-temperature curing type low-resistance conductive slurry is applied to HJT batteries, 5G communication electronics, medical appliances and the like; the prepared sintered low-resistance conductive paste is applied to monocrystalline silicon solar cells, polycrystalline silicon solar cells, electronic components and the like.

The following examples, based on the above parameters, were selected.

Example 201

A low-temperature curing type low-resistance conductive paste is prepared by using an organic carrier and the composite flaky silver powder F7 prepared in example 107 as raw materials, and fully mixing, infiltrating, dispersing and grinding 60 parts by weight of the composite flaky silver powder F7, 16 parts by weight of gamma-butyrolactone, 16 parts by weight of butyl carbitol and 8 parts by weight of epoxy resin to prepare the low-temperature curing type low-resistance conductive paste G1.

Example 202

A low-temperature curing type low-resistance conductive paste is prepared by using an organic carrier and the composite flake silver powder F4 prepared in example 104 as raw materials, and fully mixing, infiltrating, dispersing and grinding 80 parts by weight of the composite flake silver powder F4, 7 parts by weight of diethylene glycol butyl ether acetate and 3 parts by weight of organic silicon to prepare the low-temperature curing type low-resistance conductive paste G2.

Example 203

A low-temperature curing type low-resistance conductive paste is prepared by using a raw material comprising an organic carrier and the composite flake silver powder F10 prepared in example 1010, and fully mixing, infiltrating, dispersing and grinding 50 parts by weight of the composite flake silver powder F10, 25 parts by weight of tributyl citrate and 5 parts by weight of polyvinyl chloride resin to obtain a low-temperature curing type low-resistance conductive paste G3.

Example 204

A low-temperature curing type low-resistance conductive paste is prepared by fully mixing, infiltrating, dispersing and grinding 30 parts by weight of composite flake silver powder F10, 35 parts by weight of terpineol, 10 parts by weight of phenolic resin, 5 parts by weight of thixotropic agent and 5 parts by weight of dispersing agent to obtain a low-temperature curing type low-resistance conductive paste G4.

Example 205

A low-temperature curing type low-resistance conductive paste is prepared by using 40 parts by weight of composite flake silver powder F6, 33 parts by weight of diethylene glycol butyl ether, 2 parts by weight of phenolic resin, 3 parts by weight of epoxy resin and 2 parts by weight of thixotropic agent, and fully mixing, infiltrating, dispersing and grinding the components to obtain the low-temperature curing type low-resistance conductive paste G5.

Example 206

A low-temperature curing type low-resistance conductive paste is prepared by using raw materials including an organic carrier, an additive and the composite flaky silver powder F5 prepared in example 105, and fully mixing, infiltrating, dispersing and grinding 60 parts by weight of the composite flaky silver powder F5, 8 parts by weight of gamma-butyrolactone, 1 part by weight of ethyl cellulose, 0.2 part by weight of a curing agent and 0.8 part by weight of a dispersing agent to prepare the low-temperature curing type low-resistance conductive paste G6.

Example 207

A low-temperature curing type low-resistance conductive paste is prepared by using raw materials including an organic carrier, an additive and the composite flaky silver powder F7 prepared in example 107, and fully mixing, infiltrating, dispersing and grinding 60 parts by weight of the composite flaky silver powder F7, 7.8 parts by weight of gamma-butyrolactone, 1 part by weight of ethyl cellulose, 0.2 part by weight of a curing agent and 1 part by weight of a dispersing agent to prepare the low-temperature curing type low-resistance conductive paste G7.

Example 208

A low-temperature curing type low-resistance conductive paste is prepared by using raw materials including an organic carrier, an additive and the composite flaky silver powder F10 prepared in example 1010, and fully mixing, infiltrating, dispersing and grinding 60 parts by weight of the composite flaky silver powder F10, 7.6 parts by weight of gamma-butyrolactone, 1 part by weight of ethyl cellulose, 0.2 part by weight of a curing agent and 1.2 parts by weight of a dispersing agent to prepare the low-temperature curing type low-resistance conductive paste G8.

Example 209

A low-temperature curing type low-resistance conductive paste is prepared by using raw materials including an organic carrier, an additive and the composite flaky silver powder F5 prepared in example 105, and fully mixing, infiltrating, dispersing and grinding 80 parts by weight of the composite flaky silver powder F5, 8 parts by weight of gamma-butyrolactone, 1 part by weight of ethyl cellulose, 0.2 part by weight of a curing agent and 0.8 part by weight of a dispersing agent to prepare the low-temperature curing type low-resistance conductive paste G9.

Example 2010

A low-temperature curing type low-resistance conductive paste is prepared by using raw materials including an organic carrier, an additive and the composite flaky silver powder F7 prepared in example 107, and mixing, infiltrating, dispersing and grinding 80 parts by weight of the composite flaky silver powder F7, 7.8 parts by weight of gamma-butyrolactone, 1 part by weight of ethyl cellulose, 0.2 part by weight of a curing agent and 1 part by weight of a dispersing agent to obtain the low-temperature curing type low-resistance conductive paste G10.

Example 2011

A low-temperature curing type low-resistance conductive paste is prepared by using raw materials including an organic carrier, an additive and the composite flaky silver powder F10 prepared in example 1010, and fully mixing, infiltrating, dispersing and grinding 80 parts by weight of the composite flaky silver powder F10, 7.6 parts by weight of gamma-butyrolactone, 1 part by weight of ethyl cellulose, 0.2 part by weight of a curing agent and 1.2 parts by weight of a dispersing agent to prepare the low-temperature curing type low-resistance conductive paste G11.

Comparative example 206-1

The only difference from example 206 is that the same operation as in example 206 was carried out to produce a conductive paste GG1, in which 18 parts by weight of the plate-like silver powder and 72 parts by weight of the spherical silver powder were used instead of the commercially available plate-like silver powder having a similar morphology and equivalent properties, namely, the composite plate-like silver powder F5 was replaced with the plate-like silver powder F5.

The mass ratio of the plate-like silver powder in the slurry of the comparative example 206-1 was 18% as in the slurry of example 206.

Comparative example 207-1

The only difference from example 207 was that the same operation as in example 207 was carried out to produce electroconductive paste GG2 by replacing the commercially available silver flake powder with composite silver flake powder F7 having a similar morphology and equivalent properties, i.e., replacing the composite silver flake powder F7 with 30 parts by weight of silver flake powder and 60 parts by weight of spherical silver powder.

The mass ratio of the plate-like silver powder in the slurry raw material of comparative example 207-1 was 30% as in the slurry raw material of example 207.

Comparative example 208-1

The difference from example 208 was only in that the same operation as in example 208 was carried out to obtain a conductive paste GG3 by replacing the commercially available silver flake having a similar morphology and equivalent property with the composite silver flake F10, i.e., 48 parts by weight of the silver flake and 42 parts by weight of the spherical silver powder in place of the composite silver flake F10.

The mass ratio of the plate-like silver powder in the slurry raw material of the comparative example 208-1 was 48% as the same as that in the slurry raw material of example 208.

Comparative example 209-1

The difference from example 209 was only in that the composite silver flake F5 was used in place of a commercially available silver flake having a similar morphology and equivalent property, namely, 24 parts by weight of the silver flake and 66 parts by weight of the spherical silver powder were used in place of the composite silver flake F5, and the same operation as in example 209 was carried out to produce an electroconductive paste GG4.

The mass ratio of the plate-like silver powder in the slurry of the comparative example 209-1 was 24% as in the slurry of example 209.

Comparative example 2010-1

The only difference from example 2010 was that the same operation as in example 2010 was carried out to produce a conductive paste GG5 by replacing the commercially available silver flake having a similar morphology and equivalent property with the composite silver flake F7, i.e., replacing the composite silver flake F7 with 40 parts by weight of the silver flake and 50 parts by weight of the silver sphere, respectively.

The mass ratio of the plate-like silver powder in the slurry of the comparative example 2010-1 was 40% as in the slurry of the example 2010.

Comparative example 2011-1

The difference from example 2011 is that the same operation as that of example 2011 is carried out to obtain a conductive paste GG6, wherein the commercially available silver flake with similar morphology and equivalent properties is replaced with the composite silver flake F10, namely 64 parts by weight of the silver flake and 26 parts by weight of the silver sphere are used for replacing the composite silver flake F10.

The mass ratio of the plate-like silver powder in the slurry raw material of the comparative example 2011-1 is 64% as in the slurry raw material of the example 2011.

All the conductive paste products prepared in the examples and the comparative examples are cured at the temperature of 200 ℃ for 30min to form a silver conductive layer for resistivity test; the conductive paste products prepared in the examples 206 to 2011 and the comparative examples 206-1 to 2011-1 were subjected to printability test by using a 430/13 to 26 μm screen without mesh knots. The test performance is listed in table 2 for comparison:

TABLE 2

The test performance data analysis of table 2 is as follows:

1. as can be seen from comparison of examples 201 to 2011 and comparative examples 206-1 to 2011-1, the resistivity of the silver conductive layer is closely related to the content, shape, size and curing process conditions of the silver powder serving as the conductive phase, and particularly, the composite flake silver powder prepared by the preparation method of the composite flake silver powder has the most significant influence on the content and curing process conditions of the flake silver powder. A large number of tests and analyses prove that the composite flake silver powder has small flake diameter, uniform distribution and excellent dispersibility, can form better connection when being applied to slurry compared with the conventional flake silver powder, establishes a conductive network and reduces volume resistivity.

2. As can be seen from comparison between examples 206 to 2011 and comparative examples 206-1 to 2011-1, the composite flake silver powder can effectively reduce the resistivity of the silver conductive layer, and a large number of experiments prove that the composite flake silver powder has the following advantages compared with the conventional flake silver powder: the stacking densification degree is higher, the filling amount of the silver powder applied to the conductive paste is sufficient, and the maximum adding amount can be increased to more than 30%; the resistivity is lower by 2 to 5 multiplied by 10 under the same adding amount ^-7 Omega cm, namely, the conductivity is better; the silver powder consumption can be reduced by more than 20% under the same resistivity.

3. According to six corresponding comparisons of the embodiments 206-2011 and the comparative examples 206-1-2011-1, the composite flaky silver powder prepared by the preparation method of the composite flaky silver powder has smaller change range of the printing line width and the printing line height along with the increase of the proportion of the flaky silver powder when being applied to low-temperature curing conductive paste compared with the conventional spherical mixed powder, and the fact that the integral printing performance of the composite flaky silver powder is excellent and stable is proved. Under the same proportion, the resistivity of the composite flake silver powder applied by the low-temperature curing conductive paste is 0.2-0.5 multiplied by 10 less than that of the corresponding conventional flake mixed powder ^-6 Omega cm, when low resistance is pursued, the addition amount of the composite flake silver powder can be increased under the condition that the printability is hardly influenced, and the low-resistance silver paste is prepared, while the conventional spherical mixed powder has large adverse influence on the printability and has limited addition amount, so that the reduction range of the resistivity is limited, and the performance requirements of the low-resistance silver paste and a silver conductive layer are difficult to meet. When the resistivity is the same, the proportion of the composite flake silver powder is obviously less than that of the conventional flake mixed powder, the grinding time of the corresponding basic silver powder can be greatly shortened, and the energy consumption can be reduced.

4. Using the commercially available silver flake powder of comparative example 206-1, the amount of the silver flake powder was formulated such that the resistivity of the silver conductive layer was designed to be 3.6X 10 while retaining the amount of the organic vehicle of comparative example 206-1 ^-6 About Ω · cm, the amount of the silver flake should be 70 parts by weight or more. Multiple test practices also prove that the commercial flake silver powder influences the printing property of the slurry due to the reasons of overlarge sheet diameter size and the like, and the addition amount of the silver powder is limited, so that the reduction range of the resistivity is also limited.

The composite flake silver powder prepared by the preparation method of the composite flake silver powder has excellent performance when being applied to low-temperature curing conductive paste, is suitable for large-scale industrial production, remarkably reduces the production and manufacturing cost, can fully meet the technical requirements of low-temperature curing low-resistance conductive paste required in the aspects of HJT batteries, 5G communication electronics, medical instruments and the like, breaks through the application limitation of the flake silver powder in the industrial production of the low-temperature curing conductive paste, and especially develops a new performance optimization channel in high-value semiconductors and electronic applications.

Example 301

A sintered low-resistance conductive paste is prepared by fully mixing, infiltrating, dispersing and grinding 40 parts by weight of composite flake silver powder F8, 5 parts by weight of glass powder, 40 parts by weight of terpineol and 15 parts by weight of PVB to obtain a sintered low-resistance conductive paste H1.

Example 302

A sintered low-resistance conductive paste is prepared by fully mixing, infiltrating, dispersing and grinding 50 parts by weight of composite flake silver powder F10, 5 parts by weight of glass powder, 32 parts by weight of terpineol and 8 parts by weight of methyl cellulose, wherein the raw materials comprise an organic carrier, glass powder and the composite flake silver powder F10 prepared in example 10 to prepare the sintered low-resistance conductive paste H2.

Example 303

A sintered low-resistance conductive paste is prepared by fully mixing, infiltrating, dispersing and grinding 30 parts by weight of composite flake silver powder F5, 10 parts by weight of glass powder, 15 parts by weight of terpineol, 3 parts by weight of PVB and 2 parts by weight of methyl cellulose to obtain a sintered low-resistance conductive paste H3.

Example 304

A sintered low-resistance conductive paste is prepared by fully mixing, infiltrating, dispersing and grinding 30 parts by weight of composite flake silver powder F7, 2 parts by weight of glass powder, 13 parts by weight of terpineol and 3 parts by weight of methyl cellulose, wherein the raw materials comprise an organic carrier, glass powder and the composite flake silver powder F7 prepared in example 7 to prepare the sintered low-resistance conductive paste H4.

Example 305

A sintered low-resistance conductive paste is prepared by fully mixing, infiltrating, dispersing and grinding 15 parts by weight of composite flake silver powder F5, 2 parts by weight of glass powder, 7 parts by weight of terpineol and 1 part by weight of methyl cellulose, wherein the raw materials comprise an organic carrier, glass powder and the composite flake silver powder F5 prepared in example 5.

Example 306

A sintered low-resistance conductive paste is prepared by fully mixing, infiltrating, dispersing and grinding 30 parts by weight of composite flake silver powder F7, 2 parts by weight of glass powder, 7 parts by weight of terpineol and 1 part by weight of methyl cellulose, wherein the raw materials comprise an organic carrier, glass powder and the composite flake silver powder F7 prepared in example 7.

Example 307

A sintered low-resistance conductive paste is prepared by fully mixing, infiltrating, dispersing and grinding 30 parts by weight of composite flake silver powder F10, 2 parts by weight of glass powder, 7 parts by weight of terpineol and 1 part by weight of methyl cellulose, wherein the raw materials comprise an organic carrier, glass powder and the composite flake silver powder F10 prepared in example 10 to prepare the sintered low-resistance conductive paste H7.

Example 308

A sintered low-resistance conductive paste is prepared by fully mixing, infiltrating, dispersing and grinding 60 parts by weight of composite flake silver powder F5, 2 parts by weight of glass powder, 7 parts by weight of terpineol and 1 part by weight of methyl cellulose, wherein the raw materials comprise an organic carrier, glass powder and the composite flake silver powder F5 prepared in example 5.

Example 309

A sintered low-resistance conductive paste is prepared by fully mixing, infiltrating, dispersing and grinding 60 parts by weight of composite flake silver powder F7, 2 parts by weight of glass powder, 7 parts by weight of terpineol and 1 part by weight of methyl cellulose, wherein the raw materials comprise an organic carrier, glass powder and the composite flake silver powder F7 prepared in example 7.

Example 3010

A sintered low-resistance conductive paste is prepared by fully mixing, infiltrating, dispersing and grinding 60 parts by weight of composite flake silver powder F10, 2 parts by weight of glass powder, 7 parts by weight of terpineol and 1 part by weight of methyl cellulose, wherein the raw materials comprise an organic carrier, glass powder and the composite flake silver powder F10 prepared in example 10.

Comparative example 304-1

The same operation as in example 304 was carried out except that the amount of the composite plate-like silver powder F7 used was adjusted to 15 parts by weight, to obtain a conductive paste HH1.

Comparative example 305-1

The only difference from example 305 was that the same operation as in example 305 was carried out to obtain a conductive paste HH2, substituting the commercially available silver flake having the similar morphology and equivalent properties with the composite silver flake F5, namely, using 9 parts by weight of the silver flake and 81 parts by weight of the spherical silver powder instead of the composite silver flake F5.

The mass ratio of the plate-like silver powder in the slurry of the comparative example 305-1 was 9% as the same as that in the slurry of example 305.

Comparative example 306-1

The same operation as in example 306 was carried out except that the composite silver flake F7 was replaced with a commercially available silver flake having a similar morphology and equivalent performance, namely, 15 parts by weight of the silver flake and 75 parts by weight of the spherical silver powder were used in place of the composite silver flake F7, to obtain conductive paste HH3.

The mass ratio of the plate-like silver powder in the slurry of the comparative example 306-1 was 15% as in the slurry of example 306.

Comparative example 307-1

The same operation as in example 307 was carried out except that the composite silver flake F10 was replaced with a commercially available silver flake having a similar morphology and equivalent performance, namely, 24 parts by weight of the silver flake and 66 parts by weight of the spherical silver powder were used in place of the composite silver flake F10, to obtain conductive paste HH4.

The mass ratio of the plate-like silver powder in the slurry raw material of the comparative example 307-1 was the same as that in the slurry raw material of example 307 and was 24%.

Comparative example 308-1

The same operation as in example 308 was carried out except that the composite silver flake F5 was used in place of a commercially available silver flake having a similar morphology and equivalent property, namely, 18 parts by weight of the silver flake and 72 parts by weight of the spherical silver powder were used in place of the composite silver flake F5, to obtain conductive paste HH5.

The mass ratio of the plate-like silver powder in the slurry of the comparative example 308-1 was 18%, which was the same as that in the slurry of the example 308.

Comparative example 309-1

The same operation as in example 309 was carried out except that the composite silver flake F7 was used in place of a commercially available silver flake having a similar morphology and equivalent performance, namely, 30 parts by weight of the silver flake and 60 parts by weight of the spherical silver powder were used in place of the composite silver flake F7, to obtain conductive paste HH6.

The mass ratio of the plate-like silver powder in the slurry raw material in the comparative example 309-1 was 30% as in the slurry raw material in example 309.

Comparative example 3010-1

The same operation as in example 3010 was carried out except that the composite silver flake F10 was used in place of a commercially available silver flake having a similar morphology and equivalent performance, namely, 18 parts by weight of the silver flake and 72 parts by weight of the spherical silver powder were used in place of the composite silver flake F10, to obtain conductive paste HH7.

The mass ratio of the plate-like silver powder in the slurry raw material of the comparative example 3010-1 was 48% as the same mass ratio as that in the slurry raw material of example 3010.

The glass powders in examples 301 to 3010 and comparative examples 304-1 to 3010-1 all used Si-Mg-Bi systems.

Sintering the conductive paste products prepared in all the examples and the comparative examples at 850 ℃, keeping the peak value for more than 5min, and forming a silver conductive layer to perform resistivity test; the conductive paste products prepared in examples 305 to 3010 and comparative examples 305-1 to 3010-1 were each subjected to printability test using an open mesh-free screen of 430/13 to 17 μm. The test performance is compared in table 3:

TABLE 3

The test performance data analysis of table 3 is as follows:

1. as can be seen from the comparison between examples 301 to 3010 and comparative examples 304-1 to 3010-1, the resistivity of the silver conductive layer is closely related to the content, shape, size and sintering process conditions of the silver powder as the conductive phase, and particularly, the composite silver flake prepared by the method for preparing the composite silver flake has the most significant influence on the content and sintering process conditions of the silver flake. A large number of tests and analyses prove that the composite flake silver powder disclosed by the invention is small in flake diameter, uniform in distribution and particularly excellent in dispersibility, and can form better connection when being applied to slurry compared with the conventional flake silver powder, so that a conductive network is established, and the volume resistivity is reduced.

2. As can be seen from the comparison between examples 305 to 3010 and comparative examples 305-1 to 3010, the composite plate-like silver powder of the present application can effectively reduce the resistivity of the silver conductive layer, and a large number of experiments prove that the composite plate-like silver powder of the present application is more excellent than the conventional plate-like silver powder in terms of: the stacking densification degree is higher, the filling amount of the silver powder applied to the conductive paste is sufficient, and the maximum adding amount can be increased to more than 30%; the resistivity is lower by 2 to 5 multiplied by 10 under the same adding amount ^-7 Omega cm, namely, the conductivity is better; the silver powder consumption can be reduced by more than 20% under the same resistivity.

3. As can be seen from the six corresponding comparisons of the examples 305 to 3010 and the comparative examples 305-1 to 3010, the composite flake silver powder prepared by the method for preparing the composite flake silver powder has smaller variation range of the printing line width and the printing line height along with the increase of the proportion of the flake silver powder when being applied to the sintered conductive paste, and the fact that the overall printing performance of the composite flake silver powder is excellent and more stable is confirmed. At the same proportional content, the applicationThe sintered conductive slurry applied to the composite flake silver powder has resistivity which is 0.2 to 0.5 multiplied by 10 less than that applied to the corresponding conventional spherical flake mixed powder ^-6 Omega cm, when low resistance is pursued, the adding amount of the composite flake silver powder can be increased under the condition of hardly influencing the printing property, and the low-resistance silver paste is prepared, while the adding amount of the conventional spherical flake mixed powder is limited due to the large adverse influence on the printing property, so that the reduction range of the resistivity is limited, and the performance requirements of the low-resistance silver paste and the silver conducting layer are difficult to meet. When the resistivity is the same, the proportion of the composite flake silver powder is obviously less than that of the conventional spherical flake mixed powder, the grinding time of the corresponding basic silver powder can be greatly shortened, and the energy consumption can be reduced.

4. Using the commercially available plate-like silver powder of comparative example 305-1, the amount of the organic vehicle of comparative example 305-1 was reserved, and the amount of the plate-like silver powder was formulated such that when the resistivity of the silver conductive layer was designed to be 2.1X 10 ^-6 About Ω · cm, the amount of the silver flake should be 70 parts by weight or more. Multiple test practices also prove that the commercial flake silver powder influences the printing property of the slurry due to the reasons of overlarge flake diameter size, wide particle size distribution and the like, and the addition amount of the silver powder is limited, so that the adjustment range of the reduction of the resistivity is also limited.

The composite flake silver powder prepared by the preparation method of the composite flake silver powder has excellent performance when being applied to the sintered conductive paste, is suitable for large-scale industrial production, remarkably reduces the production and manufacturing cost, can fully meet the technical requirements of the sintered low-resistance conductive paste required in the aspects of monocrystalline silicon solar cells, polycrystalline silicon solar cells, electronic components and the like, breaks through the application limit of the flake silver powder in the industrial production of the sintered conductive paste, and especially opens up a new performance optimization channel in the application of high-added-value semiconductors and electronics.

Claims (14)

1. The preparation method of the composite flake silver powder is characterized by comprising the following steps of:

s10, preparing base silver powder with the average grain diameter of 0.3-3 mu m as a raw material, and adding the raw material into a protective carrier;

and S20, carrying out autorotation driving grinding on the mixture obtained in the step S10 through the arm-provided rotating shaft assembly, carrying out cooling treatment, and finally carrying out separation post-treatment to obtain the composite flake silver powder containing the flake silver powder and part of the basic silver powder, or the composite flake silver powder containing the flake silver powder and a basic silver powder deformation body, or the composite flake silver powder containing the flake silver powder and part of the basic silver powder and the basic silver powder deformation body.

2. The method for producing a composite plate-like silver powder according to claim 1, characterized in that: the grinding rotating speed of the rotating shaft assembly with the arm is set to be 80-300 r/min, and the grinding time is set to be 1-6 h.

3. The method for producing a composite plate-like silver powder according to claim 1, characterized in that: the axis of rotation of the armed rotary shaft assembly is set at an angle of no more than 50 ° to the vertical.

4. The method for producing a composite plate-like silver powder according to claim 1, characterized in that: the temperature of the cooling medium adopted in the cooling treatment is not more than 10 ℃.

5. The method for producing a composite plate-like silver powder according to claim 1, characterized in that: in the step S20, the mixture obtained in the step S10 is premixed before autorotation driving grinding through the rotating shaft assembly with the arm, the premixing rotating speed is 10-100 r/min, and the premixing time is not more than 1h.

6. The method for producing a composite plate-like silver powder according to claim 1, characterized in that: the protective carrier comprises a solvent A and a protective agent, wherein the base silver powder serving as a raw material is mixed with the solvent A according to the mass ratio of 15-25: 4-6, and the base silver powder serving as a raw material is mixed with the protective agent according to the mass ratio of 500: 6-9.

7. The method for producing a composite plate-like silver powder according to claim 6, characterized in that: the solvent A is one or more of absolute ethyl alcohol, acetone and deionized water, and the protective agent is one or more of saturated fatty acids and unsaturated fatty acids.

8. The method for producing a composite plate-like silver powder according to claim 1, characterized in that: the base silver powder as the raw material includes one or a mixture of at least two of a spherical silver powder, an irregular silver powder, and a silver powder of a flocculent shape.

9. The method for producing a composite plate-like silver powder according to claim 1, characterized in that: the average grain diameter is 0.3-3 μm and is formed by single grain diameter or mixed grain diameter.

10. The method for producing a composite plate-like silver powder according to claim 1, characterized in that: the post-separation treatment refers to solid-liquid separation and drying treatment, or solid-liquid separation, drying and screening treatment.

11. The method for producing a composite plate-like silver powder according to any one of claims 1 to 10, characterized in that: the mass of the flake silver powder is not less than 10% and less than 100% based on 100% of the mass of the prepared composite flake silver powder.

12. A low-resistance conductive paste characterized in that: the preparation raw materials comprise an organic carrier and the composite flake silver powder prepared by the preparation method of any one of claims 1 to 11, and the composite flake silver powder and the organic carrier are mixed according to the mass ratio of 60-90: 5-70 to prepare the low-temperature curing type low-resistance conductive paste;

or, the preparation raw materials comprise an organic carrier, glass powder and the composite flake silver powder prepared by the preparation method of any one of claims 1 to 10, and the composite flake silver powder, the glass powder and the organic carrier are mixed according to the mass ratio of 30-90: 1-20: 5-65 to prepare the sintered low-resistance conductive paste.

13. The low-resistance conductive paste according to claim 12, wherein: the preparation raw materials also comprise additives, and the mass percentage of the additives is 0.1-10% by taking the total mass of the preparation raw materials as 100%.

14. The low-resistance conductive paste according to claim 12 or 13, wherein: the organic carrier comprises a solvent B and organic resin, wherein the organic resin accounts for 6-30% of the total mass of the organic carrier by 100%;

the solvent B is one or the mixture of more than two of terpineol, tributyl citrate, diethylene glycol butyl ether acetate, diethylene glycol dibutyl ether, diethylene glycol butyl ether, DBE, alcohol ester twelve, 2, 4-trimethyl-1, 3-pentanediol diisobutyrate, triethylene glycol, tripropylene glycol methyl ether, hexanediol monobutyl ether, butyl carbitol acetate, gamma-butyrolactone, N' -dimethyl amine acetate and alpha-terpineol, dimethyl adipate, dimethyl glutarate, ethylene glycol phenyl ether and 3-hydroxy-1, 3, 5-pentanedioic acid;

one of the raw materials of the low-temperature curing type low-resistance conductive paste is organic resin which is one or more than two of polyvinyl chloride, polyurethane, phenolic resin, epoxy resin, acrylic resin, organic silicon resin, unsaturated polyester, ethyl cellulose and PVB;

one of the raw materials of the sintered low-resistance conductive paste is one or more of cellulose, ethylene, polyacrylic acid, polypropylene ester, polyethylene oxide, polypropylene oxide, polyethylene glycol, phenolic resin, acrylic resin, polyvinyl butyral resin, rosin resin and derivatives thereof.

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