CN114743716A

CN114743716A - Silver powder capable of being sintered at low temperature and preparation method and application thereof

Info

Publication number: CN114743716A
Application number: CN202210398658.7A
Authority: CN
Inventors: 潘锋; 李永晟; 刘建; 林海
Original assignee: Peking University Shenzhen Graduate School
Current assignee: Peking University Shenzhen Graduate School
Priority date: 2022-04-15
Filing date: 2022-04-15
Publication date: 2022-07-12

Abstract

The application discloses silver powder capable of being sintered at low temperature and a preparation method and application thereof. The low-temperature sinterable silver powder of the present application contains silver crystallite particles having a primary crystallite size of 10 to 30 nm. According to the silver powder capable of being sintered at low temperature, the silver microcrystal particles with the crystallite dimension of 10-30nm are adopted at one time, so that the sintering temperature of the silver powder capable of being sintered at low temperature can be effectively reduced, and the use requirement of the silver paste at lower sintering temperature is met; further, an electrode having low resistance can be formed after firing.

Description

Silver powder capable of being sintered at low temperature and preparation method and application thereof

Technical Field

The application relates to the technical field of silver powder capable of being sintered at low temperature, in particular to silver powder capable of being sintered at low temperature and a preparation method and application thereof.

Background

Silver paste is produced by mixing silver powder, glass frit, and an organic solvent, and is widely used as an internal electrode of a capacitor, a conductor of a circuit board, a solar cell, or a circuit of a display panel substrate. When silver paste is used, it is usually printed on a substrate to form a predetermined pattern; then, the silver powder is sintered at a high temperature to remove the organic solvent, thereby sintering the silver powder into an integrally formed electrode. Wherein, the temperature of the high-temperature sintering is based on the capability of melting the silver powder into a whole. Therefore, the sintering temperature of silver powder directly affects and determines the sintering temperature after silver paste printing.

In some application environments, high temperature processing of the substrate cannot be performed or is avoided as much as possible; therefore, the silver powder can be sintered at low temperature. The low-temperature sinterable silver powder is a silver powder that can be sintered and melted at a relatively low temperature. The silver paste prepared from the silver powder capable of being sintered at low temperature can be sintered into an integrally-formed electrode at relatively low temperature after being printed.

The melting point of silver is 962 ℃, and the existing silver powder capable of being sintered at low temperature can be sintered at the temperature of 400-500 ℃ by some special structural designs. However, with the development of technology and the wide application of silver paste printed circuit boards, the existing silver powder capable of being sintered at low temperature cannot meet the use requirement.

Therefore, how to develop the silver powder capable of being sintered at low temperature and with lower sintering temperature is a research focus and difficulty in the technical field of silver paste.

Disclosure of Invention

The application aims to provide a novel silver powder capable of being sintered at low temperature, and a preparation method and application thereof.

The following technical scheme is adopted in the application:

one aspect of the present application discloses a low-temperature sinterable silver powder including silver crystallite particles having a primary crystallite size of 10-30 nm.

The silver powder capable of being sintered at low temperature contains silver microcrystal particles with the crystallite dimension of 10-30nm, so that the sintering temperature of the silver powder capable of being sintered at low temperature can be effectively reduced, and the use requirement of the silver paste at lower sintering temperature is met.

In one implementation of the present application, the silver crystallite particles comprise at least 40% of the total weight of the low temperature sinterable silver powder.

It can be understood that the silver powder capable of being sintered at low temperature can reduce the sintering temperature as long as the silver microcrystal particles with the primary microcrystal size of 10-30nm are contained; however, in order to ensure the temperature lowering effect, it is preferable herein to contain silver crystallite particles having a primary crystallite size of 10 to 30nm at least 40%, for example, 50%, 60%, 70%, 80%, 95% or 97% by weight of the total weight of the low temperature sinterable silver powder. In one implementation of the present application, low temperature sintering at 350 ℃ or even lower temperatures can be achieved.

In one implementation of the present application, the silver powder capable of being sintered at a low temperature is the silver crystallite particles agglomerated into secondary particles.

In one implementation of the present application, the secondary particles are solid structures or voids are present inside the secondary particles.

In one implementation of the present application, voids are present inside the secondary particles, and the voids are at least one of spherical cavities, crevice cavities, and irregular geometric cavities.

Preferably, the volume of the voids is not less than 1% of the volume of the secondary particles.

The key point of the application lies in that the silver microcrystal particles with the primary microcrystal size of 10-30nm have lower sintering temperature through research, so that a novel silver powder capable of being sintered at low temperature is creatively developed; as for the shape, size, etc. of the secondary particles of the silver powder, the existing silver powder can be referred to. However, further studies of the present application have found that, in the case where the secondary particles of the silver powder contain voids, it is further advantageous to lower the sintering temperature; this effect is more pronounced especially in the case where the volume of the voids is not less than 1% of the volume of the secondary particles. And, as the void volume increases, the effect of facilitating low temperature sintering becomes more pronounced. For example, in one implementation of the present application, the voids may be 25%, 30%, 40% by volume of the secondary particle.

In one implementation of the application, the secondary particles are of spherical, spheroidal, platelet or rod-like structure.

In one embodiment of the application, the secondary particles are spherical or spheroidal in structure and have a particle size of 0.3 to 4 μm.

It should be noted that the particle size of the secondary particles is not too small, which is not favorable for printing after silver paste is made from silver powder, and may cause problems such as hole blocking.

The application discloses another side discloses but silver thick liquid of low temperature sintering silver powder of this application.

The silver paste is characterized in that the silver paste can be sintered at low temperature; as for other components in the silver paste, for example, the glass frit, the solvent, etc. can refer to the existing conductive silver paste or the solar cell silver paste, and are not limited in detail herein.

It should be further noted that the silver paste of the present application can be printed with the silver powder capable of being sintered at a low temperature, and then the silver powder can be sintered into an integrally formed structure at a low sintering temperature. For example, in one implementation of the present application, a low temperature sintering of 350 ℃ may be achieved.

The application of this application one side again discloses the application of the silver thick liquid of this application in laminated capacitor's internal electrode, LTCC, solar cell, 5G wave filter, plasma display panel, touch panel, PET are the membrane switch of substrate, flexible circuit board, piezo-resistor and thermistor, piezoceramics or carbon film potentiometre.

The application further discloses a preparation method of the silver powder capable of being sintered at the low temperature, which comprises the following steps:

controlling the solution of silver ions or silver ion complexes at the reaction temperature;

stirring the solution of silver ions or silver ion complexes in an inert gas environment, adding a reducing agent into the solution for reduction reaction, and keeping the temperature change in the whole reaction process to be less than 5 ℃;

after the reduction reaction is finished, adding a surface coating solution into the reaction system for surface coating to obtain a solution containing silver particles;

and washing the obtained solution containing the silver particles by pure water, drying after washing to obtain dry powder, and crushing the dry powder to obtain the low-temperature sintering silver powder.

In one implementation of the application, the reducing agent is a solution of a substance containing an aldehyde group or a hydroxyl group.

In one embodiment of the application, the substance containing an aldehyde group or a hydroxyl group is at least one of formaldehyde, acetaldehyde, ascorbic acid, ethylene glycol and glycerol.

In one embodiment of the application, the reducing agent is an aqueous or alcoholic solution of a substance containing an aldehyde group or a hydroxyl group.

In one embodiment of the application, the concentration of the aldehyde or hydroxyl group-containing substance in the solution is 10 to 30%, preferably 15 to 20%.

In one implementation of the application, the source of silver ions is silver nitrate or silver sulfate.

In one implementation of the application, the silver ion complex is a complex of silver ions with at least one of ammonia, ammonium salts, sulfites, sulfates, amines, and transition metal ions.

In one embodiment of the application, the concentration of silver ions in the solution of silver ions or silver ion complexes is 0.1 to 10mol/L, preferably 0.1 to 5mol/L, more preferably 0.5 to 2 mol/L.

It should be noted that, too high concentration of silver ions may cause explosive nucleation of silver particles, resulting in serious particle agglomeration; too low silver ion concentration results in low economy and is not suitable for industrial production.

In one embodiment of the application, the reducing agent is added in an amount of 1 to 10 equivalent times, preferably 3 to 8 equivalent times, more preferably 5 to 7 equivalent times the silver ion content.

The reaction time is directly affected by the amount of the reducing agent, and if the amount of the reducing agent is too small, the reaction time becomes too long, and if the amount of the reducing agent is too high, the reaction heat is instantaneously released, which is not favorable for temperature control.

In one embodiment of the application, the reaction temperature is 5 to 55 ℃, preferably 35 to 50 ℃, more preferably 40 to 45 ℃.

It should be noted that the reaction temperature is mainly used to control the progress of the reduction reaction and the size of primary crystallites; the reaction temperature is too low, so that the nucleation rate is too low, primary microcrystal particles grow up easily, the primary silver microcrystal particles meeting the requirements cannot be prepared, and the method is not suitable for printing fine patterns; if the reaction temperature is too high, the primary microcrystal particles are too small and the particle size distribution is not uniform, which is not beneficial to the preparation of silver paste.

In order to control the reaction temperature, the temperature of the reducing solution may be lowered, the rate of addition of the reducing solution may be controlled, the rate of addition of cold water may be controlled, or the temperature rise due to the reaction heat may be suppressed by means of external circulating water cooling or the like.

In one embodiment of the application, the reducing agent is added to the solution of silver ions or silver ion complexes at a temperature of 3 to 15 ℃ lower than the temperature of the solution of silver ions or silver ion complexes, preferably 5 to 10 ℃ lower than the temperature of the solution of silver ions or silver ion complexes.

In one implementation of the application, the surface coating solution is an ethanol solution containing 25-30% oleic acid.

In one embodiment, the method further comprises adding a dispersant to the solution of silver ions or silver ion complexes, or adding the dispersant while stirring the reducing agent, in order to prevent agglomeration of silver particles.

In one implementation of the application, the dispersant is at least one of gum arabic, gelatin, PVP, polyethylene glycol, polyacrylic acid, polycarboxylate, poly (meth) acrylic acid derivative, maleic anhydride copolymer, polyphosphate, sodium pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate.

In one implementation of the application, the dispersant is PVP.

Preferably, the molecular weight of PVP is between 3000-100000, preferably 3000-10000, more preferably 5000-8000.

The beneficial effect of this application lies in:

according to the silver powder capable of being sintered at low temperature, the silver microcrystal particles with the crystallite dimension of 10-30nm are adopted at one time, so that the sintering temperature of the silver powder capable of being sintered at low temperature can be effectively reduced, and the use requirement of the silver paste at lower sintering temperature is met; further, an electrode having low resistance can be formed after firing.

Drawings

FIG. 1 is an SEM image of a silver powder prepared in examples of the present application;

FIG. 2 is an SEM image of a sintered silver paste in an embodiment of the present application;

FIG. 3 is a graph of the sheet resistance measured after different sintering temperatures in the examples of the present application;

FIG. 4 is a sectional view of a silver powder cut by a focused ion beam in the example of the present application;

FIG. 5 is an SEM image of another silver powder in an example of the present application;

FIG. 6 is an SEM image of a silver paste prepared from another silver powder in an example of the present application after sintering;

FIG. 7 is an SEM photograph of a silver powder as a comparative example in examples of the present application;

FIG. 8 is an SEM image of sintered silver paste prepared from silver powder as a comparative example in the examples of the present application;

FIG. 9 is an SEM image of another silver powder as a comparative example in examples of the present application;

FIG. 10 is an SEM image of a silver paste prepared from another silver powder as a comparative example after sintering in the examples of the present application;

FIG. 11 is an SEM image of silver powder prepared using acetaldehyde as a reducing agent in examples of the present application;

FIG. 12 is an SEM photograph of a silver powder prepared at a reaction temperature of 45 ℃ in examples of the present application;

FIG. 13 is an SEM image of a silver powder prepared at a reaction temperature of 50 ℃ in examples of the present application;

FIG. 14 is an SEM image of silver powder prepared by using PVP with a molecular weight of 8000 as a dispersant in the example of the present application;

FIG. 15 is an SEM photograph of a silver powder having a hollow rod-like structure prepared in examples of the present application;

fig. 16 is an SEM image of the hollow petal-shaped silver powder prepared in the examples of the present application;

FIG. 17 is an SEM image of solid spheroidal silver powder prepared in the examples of the present application;

FIG. 18 is an SEM image of a center slitted silver powder prepared in an example of the present application;

fig. 19 is an SEM image of the hollow lantern-shaped silver powder prepared in the examples of the present application.

Detailed Description

In order to meet the requirements of gradually refining printing and low-temperature rapid sintering of printed circuits such as internal electrodes of laminated capacitors, solar cells, 5G filters, plasma display panels and touch panels, micron-sized low-temperature sinterable silver powder is developed, and the low-temperature sinterable silver powder contains silver microcrystal particles with a crystallite dimension of 10-30 nm. In an implementation mode of the application, the content of silver microcrystal particles with the primary microcrystal size of 10-30nm is adjusted, so that the silver powder capable of being sintered at the low temperature can be controlled to start sintering at the temperature of 300-450 ℃, the sintering can be completed under the condition of low-temperature quick sintering of an infrared sintering furnace, and the requirements of metalized precision printing wiring of electronic components such as internal electrodes of a laminated capacitor, anode grid lines of a solar cell, a 5G filter, a plasma display panel and a touch panel are met.

The present application is described in further detail below with reference to specific embodiments and the attached drawings. The following examples are merely illustrative of the present application and should not be construed as limiting the present application.

Example 1

879g of silver nitrate is dissolved in 2455g of distilled water, 844g of 30 mass percent ammonia water solution is added after the dissolution, 20g of PVP k30 is added, the mixture is stirred uniformly to obtain a silver complex solution, the prepared solution is poured into a double-layer glass beaker, and 35 ℃ water is introduced into an interlayer of the beaker for heat preservation.

Under the conditions of stirring at 2000r/min and introducing argon gas for 1L/min, formaldehyde water solution with the mass fraction of 25% is adopted as reducing liquid, the reducing liquid with the silver ion content of 7 times equivalent is added into the solution at the speed of 1 equivalent/min, and the temperature change in the process is kept to be less than 5 ℃.

After the addition, the mixture was stirred for 10min, and then 20g of an ethanol solution containing 30% oleic acid was added to carry out surface coating, thereby obtaining a solution containing silver particles.

The above slurry was washed with pure water until the conductivity of the solution after precipitation was more than 0.2ms, centrifuged, and then put into an oven to be dried at 50 ℃ for 24 hours to obtain a dried powder, which was then pulverized to obtain the low-temperature sinterable silver powder of this example.

The SEM photograph of the silver powder of this example is shown in FIG. 1. The results of FIG. 1 show that silver powder having a uniform size distribution was obtained in the present example.

The prepared silver powder was dispersed using ethanol, and the D50 of the silver powder was measured using a laser particle sizer, and the D50 was found to be 2.88 μm.

The silver powder prepared in this example was analyzed for the primary crystallite size by XRD, and as a result, it was revealed that the silver crystallites had an average size of 17nm and a primary crystallite content of not less than 40% in a size of 10 to 20 nm.

The silver powder, the organic phase and the glass powder of the present example were mixed in a ratio of 8.8:10.2, mixing and dispersing to prepare silver paste, printing the silver paste on a silicon chip, and putting the silicon chip into an infrared sintering furnace for low-temperature fast sintering at the peak value of 350 ℃. Wherein, the formula of the organic phase is as follows: 5 parts of ethyl cellulose, 5 parts of hydrogenated castor oil, 20 parts of alcohol ester twelve and 70 parts of diethylene glycol butyl ether acetate. Glass powder: mixing PbO and SiO₂、TeO₂、WO₃、Al₂O₃、B₂O₃Mixing the materials according to the mass ratio of 50:5:30:2:2:11, putting the mixture into a muffle furnace, preserving the temperature at 1100 ℃ for 1h, pouring the mixture into water to obtain glass fragments, adding alcohol, and grinding the glass fragments into powder with the size of 3 mu m, namely the glass powder in the embodiment.

The sintering condition was observed by SEM, and the results are shown in fig. 2; the results in FIG. 2 show that the silver paste prepared from the silver powder of this example can be sintered at 350 ℃.

Printing the silver paste on an alumina ceramic substrate into a 10mm by 10mm square pattern, rapidly sintering at peak temperatures of 500 ℃, 600 ℃ and 700 ℃, and testing the square resistance of the aluminum paste by a four-probe test method after sintering is finished, wherein the test result is shown in fig. 3. The results in fig. 3 show that under the conditions of rapid sintering in an infrared mesh belt sintering furnace, the sheet resistance of the silver paste decreases with the increase of the sintering temperature, and the sheet resistance of the 500 ℃ rapid sintering and the 700 ℃ rapid sintering are still in the same order of magnitude.

The silver powder prepared in this example was cut with a focused ion beam and observed in cross section, and the results are shown in FIG. 4. The results of FIG. 4 show that the silver powder prepared in this example has a hollow spheroidal structure in the secondary particles, and the hollow volume thereof is not less than 1% of the volume of the secondary particles.

Example 2

655g of silver nitrate is dissolved in 1955g of distilled water, 345g of 45 mass percent ammonia water solution is added after the dissolution, 10g of gelatin is added, the mixture is stirred evenly to obtain silver complex solution, the prepared solution is poured into a double-layer glass beaker, and water with the temperature of 40 ℃ is introduced into the interlayer of the beaker for heat preservation.

Under the conditions of stirring at 3000r/min and introducing argon gas for 1.3L/min, formaldehyde water solution with the mass fraction of 20% is adopted as reducing liquid, the reducing liquid with the silver ion content of 5 times the equivalent weight is added into the solution at the speed of 1 equivalent/min, and the temperature change in the process is kept to be less than 10 ℃.

After the addition, the mixture was stirred for 10min, and then 10g of an ethanol solution containing 25% oleic acid was added to carry out surface coating, to obtain a solution containing silver particles.

The above slurry was washed with pure water until the conductivity of the solution after precipitation was more than 0.2ms, centrifuged, and then put into an oven to be dried at 50 ℃ for 24 hours to obtain a dried powder, which was then pulverized to obtain the silver powder of this example.

The SEM photograph of the silver powder of this example is shown in FIG. 5. The results of FIG. 5 show that silver powder having a uniform size distribution was obtained by the present example preparation.

The prepared silver powder was dispersed using ethanol, and the D50 of the silver powder was measured using a laser particle sizer, and the D50 was 1.94 μm.

The primary crystallite size of the silver powder was analyzed by XRD, and it was revealed that the silver powder prepared in this example had an average size of silver crystallites of 22nm, wherein the primary crystallite content of 10 to 30nm in size was not less than 50%.

According to the formula of the embodiment 1, silver paste is prepared from the silver powder, the silver paste is printed on a silicon chip, and the silicon chip is placed into an infrared sintering furnace to be quickly sintered at the low temperature of 350 ℃ at the peak value. The sintering condition was observed by SEM, and the results are shown in fig. 6; the results in FIG. 6 show that the silver paste prepared from the silver powder of this example can be sintered at 350 ℃.

Comparative example 1

Comparative example 1 was a commercially available Japanese imported silver powder, DOWA-4A 8F.

The silver powder of this example was observed by SEM, and the results are shown in FIG. 7. The results in fig. 7 show that the silver powder product purchased has agglomeration phenomenon, which is not beneficial to silver paste preparation and use.

The silver powder of this example was made into silver paste according to the formulation of example 1, printed on a silicon wafer, and put into an infrared sintering furnace for low-temperature fast firing at a peak of 500 ℃. The sintering condition was observed by SEM, and the result is shown in fig. 8; the results in FIG. 8 show that the silver paste prepared from the silver powder of this example still failed to sinter at 500 ℃.

Comparative example 2

Comparative example 2 is ship heavy industry Huanggang noble metal Co., Ltd, S334, which is commercially available silver powder in China.

The silver powder of this example was observed by SEM, and the results are shown in FIG. 9. The results of fig. 9 show that the purchased silver powder product has a uniform particle size and distribution.

According to the formula of the embodiment 1, silver paste is prepared from the silver powder, the silver paste is printed on a silicon chip, and the silicon chip is placed into an infrared sintering furnace to be quickly sintered at the low temperature of 500 ℃ at the peak value. The sintering condition was observed by SEM, and the result is shown in fig. 10; the results in FIG. 10 show that the silver paste prepared from the silver powder of this example still failed to sinter at 500 ℃.

Example 3

In this example, the influence of the silver ion concentration on the reaction and the silver powder was further examined in addition to examples 1 and 2. As a result, it was revealed that the particle size distribution of the silver powder can be adjusted by adjusting the concentration of silver ions, and that for the preparation of a silver powder having a secondary particle size of 0.3 to 4 μm, the concentration of silver ions needs to be controlled to 0.1 to 10mol/L, and preferably 0.1 to 5mol/L or 0.5 to 2mol/L, to prepare a silver powder having a more uniform particle size distribution.

Further to this example, different reducing agents were tested. The results show that the reducing agent can be used as a solution of a substance containing an aldehyde group or a hydroxyl group, such as an aqueous or alcoholic solution of formaldehyde, acetaldehyde, ascorbic acid, ethylene glycol or glycerol. For example, an SEM image of silver powder prepared based on example 1 using an equal amount of acetaldehyde instead of formaldehyde is shown in FIG. 11.

In this example, the reaction temperature was further tested in addition to example 1. The result shows that the silver powder meeting the requirement can be prepared at the reaction temperature of 5-55 ℃; the preferred reaction temperature is 35-50 deg.C, more preferably 40-45 deg.C. SEM photograph of the silver powder prepared at the reaction temperature of 45 ℃ is shown in FIG. 12, and SEM photograph of the silver powder prepared at the reaction temperature of 50 ℃ is shown in FIG. 13.

In this example, further, different dispersants were tested on the basis of example 1. The results show that the dispersant can be gum arabic, gelatin, PVP, polyethylene glycol, polyacrylic acid, polycarboxylate, poly (meth) acrylic acid derivative, maleic anhydride copolymer, polyphosphate, sodium pyrophosphate, sodium tripolyphosphate, or sodium hexametaphosphate; among them, PVP with a molecular weight of 3000-100000 is preferably used, PVP with a molecular weight of 3000-10000 is more preferably used, and PVP with a molecular weight of 5000-8000 is more preferably used. The SEM image of silver powder prepared using PVP with a molecular weight of 8000 is shown in FIG. 14.

In addition, in this example, based on example 1, the secondary particle silver powder having a structure of hollow rod-like silver powder, hollow petal-like silver powder, solid sphere-like silver powder, center slit silver powder, hollow cage-like silver powder, or the like can be prepared by referring to the prior art. The hollow rod-like silver powder prepared in this example is shown in FIG. 15, the hollow petal-like silver powder is shown in FIG. 16, the solid sphere-like silver powder is shown in FIG. 17, the center slit silver powder is shown in FIG. 18, and the hollow cage-like silver powder is shown in FIG. 19.

The silver powder of this example has applications such as:

1. the solid spheroidal silver powder (D50 ═ 1 μm), the hollow spheroidal silver powder (D50 ═ 1 μm), and the organic phase prepared in this example were mixed at a mass ratio of 4:5:1 to prepare a silver paste. The silver paste is printed on the crystalline silicon solar cell, and the unit consumption of the silver paste is reduced by 3% compared with that of the silver paste which completely uses solid silver powder and an organic phase, so that the use amount of silver is reduced, and the cost is reduced. The organic phase was the same as in example 1.

2. The silver paste was prepared by mixing the silver powder in the form of a hollow rod and the silver powder in the form of a solid sphere (D50 ═ 1 μm) at a ratio of 1:1, and then adding the organic phase and the glass frit. The silver paste is printed on a ceramic substrate and sintered at 850 ℃, the shrinkage rate of the silver paste can be freely adjusted within 15-35%, and the metalized application of the LTCC green tape can be met. The organic phase and the glass frit were the same as in example 1.

3. The hollow spherical silver powder (D50 is 1 mu m), the organic phase and the glass powder are mixed according to the proportion of 88:10:2 to prepare silver paste, and the silver paste is prepared into the polycrystalline silicon solar cell through screen printing, so that the requirement of fine printing is met, the open voltage and the current of the cell are improved, and the photoelectric conversion efficiency of the cell is 19.02 percent and is higher than 18.6 percent of that of the commercial silver paste. The organic phase and the glass frit were the same as in example 1.

The foregoing is a more detailed description of the present application in connection with specific embodiments thereof, and it is not intended that the present application be limited to the specific embodiments thereof. For those skilled in the art to which the present application pertains, several simple deductions or substitutions may be made without departing from the concept of the present application, and all should be considered as belonging to the protection scope of the present application.

Claims

1. A silver powder capable of being sintered at low temperature is characterized in that: comprising silver crystallite particles with a primary crystallite size of 10-30 nm.

2. The low-temperature sinterable silver powder according to claim 1, characterized in that: the silver crystallite particles account for at least 40% of the total weight of the low-temperature sinterable silver powder.

3. The low-temperature sinterable silver powder according to claim 1 or 2, characterized in that: the silver powder capable of being sintered at low temperature is formed by agglomerating silver microcrystal particles into secondary particles.

4. The low-temperature sinterable silver powder according to claim 3, characterized in that: the secondary particles are solid structures or voids are present inside the secondary particles.

5. The low-temperature sinterable silver powder according to claim 3, characterized in that: voids are present inside the secondary particles, and the voids are at least one of spherical cavities, crevice cavities, and irregular-geometry cavities;

6. The low-temperature sinterable silver powder according to claim 3, characterized in that: the secondary particles are in a spherical, spheroidal, lamellar or rod-like structure.

7. The low-temperature sinterable silver powder according to claim 3, characterized in that: the secondary particles are spherical or spheroidal structures, and the particle size of the secondary particles is 0.3-4 mu m.

8. A silver paste using the low temperature sinterable silver powder of any one of claims 1 to 7.

9. Use of the silver paste according to claim 8 in internal electrodes of laminated capacitors, LTCC, solar cells, 5G filters, plasma display panels, touch panels, PET based thin film switches, flexible circuit boards, piezoresistors and thermistors, piezoceramic or carbon film potentiometers.

10. The method for producing a low-temperature sinterable silver powder according to any one of claims 1 to 7, characterized in that: comprises the following steps of (a) carrying out,

washing the obtained solution containing the silver particles by pure water, drying after washing to obtain dry powder, and crushing the dry powder to obtain the low-temperature sinterable silver powder;

preferably, the reducing agent is a solution of a substance containing an aldehyde group or a hydroxyl group;

preferably, the substance containing aldehyde group or hydroxyl group is at least one of formaldehyde, acetaldehyde, ascorbic acid, ethylene glycol and glycerol;

preferably, the reducing agent is an aqueous solution or an alcoholic solution of a substance containing an aldehyde group or a hydroxyl group;

preferably, in the solution of the substance containing aldehyde or hydroxyl, the concentration of the substance containing aldehyde or hydroxyl is 10-30%, preferably 15-20%;

preferably, the silver ion source is silver nitrate or silver sulfate;

preferably, the silver ion complex is a complex of silver ions and at least one of ammonia, ammonium salts, sulfites, sulfates, amines and transition metal ions;

preferably, the concentration of the silver ions in the solution of the silver ions or the silver ion complexes is 0.1 to 10mol/L, preferably 0.1 to 5mol/L, and more preferably 0.5 to 2 mol/L;

preferably, the addition amount of the reducing agent is 1 to 10 times equivalent of the silver ion content, preferably 3 to 8 times, and more preferably 5 to 7 times;

preferably, the reaction temperature is 5-55 ℃, preferably 35-50 ℃, and more preferably 40-45 ℃;

preferably, before the reducing agent is added into the solution of the silver ions or the silver ion complexes, the temperature of the reducing agent is controlled to be 3-15 ℃ lower than the temperature of the solution of the silver ions or the silver ion complexes, and preferably 5-10 ℃ lower than the temperature of the solution of the silver ions or the silver ion complexes;

preferably, the surface coating solution is an ethanol solution containing 25-30% of oleic acid;

preferably, in order to prevent agglomeration of silver particles, a dispersing agent is added into a solution of silver ions or silver ion complexes, or the dispersing agent is added while the reducing agent is added under stirring;

preferably, the dispersant is at least one of gum arabic, gelatin, PVP, polyethylene glycol, polyacrylic acid, polycarboxylate, poly (meth) acrylic acid derivative, maleic anhydride copolymer, polyphosphate, sodium pyrophosphate, sodium tripolyphosphate, and sodium hexametaphosphate;

preferably, the dispersant is PVP;