Tin-doped copper-silver paste compounded with organic carrier and preparation method thereof

Abstract

The application relates to the technical field of metal paste, and discloses a tin-doped copper-silver paste with a compounded organic carrier and a preparation method thereof, which comprises the following raw materials in percentage by mass: silver-tin-copper mixed metal powder 60-80 parts, bismuth-boron-zinc mixed glass powder 5-10 parts and organic carrier 20-30 parts; the silver-tin-copper mixed metal powder comprises the following raw materials in percentage by mass: silver powder 80-90%, tin powder 0-10% and copper powder 0-10%; and the average particle size of the silver-tin-copper mixed metal powder is 1-5 mu m. In the application, spherical silver powder is used as a solid-phase main raw material, tin powder and copper powder are used to replace part of the silver powder, when the silver paste is sintered, silver and tin form upper and lower layer structures and silver-tin compounds between the two layers. When the sintering is finished, the metal silver layer is solidified by cooling, the upper surface is an air surface, the air surface can release the stress generated by thermal expansion and cold contraction, and does not cause tearing of the glass, so that the vacuum glass welding effect is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal paste, in particular to a tin-doped copper-silver paste with a compounded organic carrier and a preparation method thereof. BACKGROUND

[0002] Vacuum glass is widely used in the fields of building, automobile, green energy saving, etc. due to its excellent performance such as heat insulation, sound insulation, energy saving, fog and dew prevention, and green environmental protection. With the development of economy and the change of human environmental concept, people's demand for low carbon emission is increasingly strict, and vacuum glass has a major development opportunity. However, there are also some problems, for example, the undamaged glass sheet will fall off when damaged, which will pose a threat to personal safety. The glass sheet is tempered, which greatly improves the strength of the glass and reduces the threat to personal safety.

[0003] The traditional vacuum glass sealing material is low-melting-point glass frit or paste-alloy sealing material. However, the glass frit sealing needs to be carried out at a high temperature (such as above 450℃), and long-time high-temperature sealing can easily damage the tempered glass. Therefore, paste-alloy sealing material is generally used to seal the vacuum glass. Among the many pastes, silver powder is a plastic material with good affinity with glass frit, which can be used to relieve stress and reduce brittle fracture caused by mismatch of thermal expansion coefficients. Therefore, silver paste can be used as a vacuum glass sealing material.

[0004] After the silver paste is sintered on the glass, tin will form a silver-tin alloy compound during soldering, so that the metal silver layer is firmly welded with the solder strip, achieving sealing effect. However, since the melting point of tin is much lower than that of silver, at the welding temperature, tin can only react with the silver on the surface of the metal silver layer, and the internal silver does not melt, resulting in a mixed layer of silver, tin and silver-tin alloy in the metal silver layer, which cannot achieve uniformity and integrity. Moreover, since the expansion coefficients and hardness of the three are inconsistent, the metal silver layer will tear after sealing, causing air leakage and poor air tightness, which leads to the failure of the normal use of the vacuum glass.

[0005] Therefore, it is of great significance to develop a new type of vacuum glass sealing metal silver paste with good uniformity and integrity, which meets the current environmental development trend and market demand, and has good application prospect. SUMMARY

[0006] The present application aims to provide a tin-doped copper-silver paste with a compounded organic carrier and a preparation method thereof, to solve the technical problem that the existing metal silver paste layer will tear after vacuum glass sealing, causing air leakage, poor air tightness, and failure of the normal use of the vacuum glass.

[0007] To achieve the above object, the application adopts the following technical scheme: a tin-doped copper-silver paste with a compounded organic carrier, comprising the following raw materials in mass fraction: silver-tin-copper mixed metal powder 60-80 parts, bismuth-boron-zinc mixed glass powder 5-10 parts, and organic carrier 20-30 parts; the silver-tin-copper mixed metal powder comprises the following raw materials in mass percentage: silver powder 80-90%, tin powder 0-10%, and copper powder 0-10%; the average particle size of the silver-tin-copper mixed metal powder is 1-5 µm.

[0008] The principle of the present scheme is as follows:

[0009] The present scheme improves the soldering stability of the silver paste and effectively reduces the erosion of the silver paste on the glass substrate by reasonably combining the proportions of metal powder, glass powder, and organic carrier. The metallic silver powder is a plastic material with good affinity to glass frit, which plays a role in buffering stress and reducing brittle fracture caused by mismatch of thermal expansion coefficient. The brittle glass frit is combined with the soft and plastic silver, and finally a high-density silver layer sintering structure with good performance can be obtained. The glass powder plays a role in adjusting the expansion coefficient of the silver paste, promoting the sintering of silver powder and the densification of the silver layer, and improving the bonding force between the silver layer and the glass substrate during the preparation of the silver paste. The expansion coefficients of the silver paste, solder, and glass substrate tend to be consistent, which improves the uniformity and integrity of the three in the soldering process, effectively avoids the tearing and air leakage of the silver paste during soldering / sintering, and reduces the soldering effect of the silver paste. The organic carrier plays a role in adjusting the viscosity of the silver paste and dispersing the adhesive phase and functional phase during the preparation of the silver paste. The paste has moderate viscosity, no powder agglomeration and precipitation, and certain fluidity, which ensures that the paste maintains good morphology after screen printing. By adjusting the type and amount of the organic carrier, the hierarchical nature of the organic carrier is achieved, which has a phased volatilization to avoid concentrated volatilization in a temperature range and cause voids and cracks in the silver paste layer.

[0010] The present scheme has the following advantages:

[0011] 1. Compared with the existing silver paste used for sealing vacuum glass, which is prone to tearing of the metallic silver paste layer and causes the vacuum glass to not work properly, the present application uses spherical silver powder as the solid-phase main raw material, and tin powder and copper powder instead of part of the silver powder. During sintering of the silver paste, silver and tin form an upper and lower layer structure and a silver-tin alloy compound between the two layers. When sintering is completed, the metallic silver layer is solidified by cooling, and the upper surface is an air surface that can release the stress caused by thermal expansion and contraction without causing tearing of the glass. In addition, because the density of tin is lower than that of silver, tin will be distributed in the upper layer after sintering. During sealing, the tin powder and tin solder stick together and melt and solidify. This not only eliminates the tearing caused by thermal expansion and contraction, but also improves the soldering wettability between the silver paste coating and the tin solder, while also reducing costs and not requiring excessively high sintering temperatures. The present application has great advantages in improving production efficiency and reducing costs.

[0012] 2、The application uses spherical silver powder as the main solid-phase raw material, tin powder, copper powder and bismuth-boron-zinc mixed glass powder as the auxiliary, so that the prepared tin-doped copper-silver paste has good uniformity and integrity, and is a metal tin-doped copper-silver paste with low cost, no tearing, little erosion to the substrate glass and high bonding force.

[0013] 3、The application uses multiple glass powders with similar expansion coefficients to the substrate tempered glass, so that the silver paste coating has high bonding force with the substrate tempered glass, little erosion to the substrate glass, is not easy to fall off or tear, has no bubbles and has better durability. In addition, the inventors compare and select the organic carriers to effectively reduce the residual organic matter in the silver layer and improve the internal density of the paste, thereby effectively improving the sealing strength.

[0014] Preferably, as an improvement, the mass percentage of silver powder in the silver paste is ≥60%. The inventors have found through long-term experiments that when the mass percentage of silver powder in the silver paste is less than 60%, the silver paste layer will appear tearing, falling off and welding failure after sintering, or gas leakage after welding, resulting in poor welding effect and failing to meet the requirements of vacuum glass welding and sealing. The inventors analyze that when the silver content is too low, the glass powder content or the organic carrier content is too high. Too much glass powder content leads to too much residual glass powder content on the surface of the silver paste layer, so that the silver paste layer surface cannot be infiltrated by the solder, resulting in too large contact angle and unable to be welded. Too much organic carrier content changes the viscosity of the silver paste and the leveling property, and the silver paste layer after screen printing appears hollow, falling off and tearing, etc., which cannot meet the welding requirements.

[0015] Preferably, as an improvement, the bismuth-boron-zinc mixed glass powder is one or more of bismuthate glass powder, sodium-calcium-silicon glass powder and boron-silicate-zinc glass powder; the bismuthate glass powder has an average particle size of 1-5 µm and an expansion coefficient of 80-110×10 -7 / ℃, which comprises the following mass fractions of components: 75-80% Bi2O3, 15-20% ZnO and 1-5% B2O3; the sodium-calcium-silicon glass powder has an average particle size of 1-5 µm and an expansion coefficient of 80-100×10 -7 / ℃, which comprises the following mass fractions of components: 12-15% NaO, 7-15% Ca2O and 70-80% SiO2; and the boron-silicate-zinc glass powder has an average particle size of 1-5 µm and an expansion coefficient of 100-160×10 -7 / ℃, which comprises the following mass fractions of components: 40-60% B2O3, 20-35% ZnO and 15-25% Na2SiO3.

[0016] The scheme can make the expansion coefficient of the mixed glass powder more close to the base glass by using bismuth boron zinc mixed glass powder, wherein the bismuth salt glass powder has the advantages of low melting point and non-toxic compared with lead glass powder; the use of bismuth salt glass powder alone, the use of two kinds of bismuth salt mixed glass powder, the use of bismuth salt glass powder and sodium calcium silicon glass powder, or the use of three kinds of glass powder, etc., can make the expansion coefficient of the mixed glass powder more close to the base glass, which is beneficial to improve the bonding strength of the paste and the base glass and reduce the erosion of the silver paste coating to the base glass.

[0017] Preferably, as an improvement, the organic carrier includes the following raw materials in mass percentage: organic solvent 55-65%, dispersant 10-20%, thickening agent 3-9%, thixotropic agent 0.5-2%, surfactant 1-2%, stabilizer 5-15%, and defoaming agent 5-15%.

[0018] Preferably, as an improvement, the organic solvent is one or more of terpineol, sodium stearate, ethyl cellulose, dibutoxyethane, polyamide wax, sodium octadecyl sulfate, soybean lecithin, 1,2-propanediol, polyisobutylene, dibutyltin dilaurate, diethylene glycol ethyl ether, tributyl phosphate, ethyl acetate, butyl acetate, trihydroxy polypropylene oxide ether, sorbitan trioleate, dibutyl phthalate, tributyl citrate, polyethylene glycol, oleic acid, and xylene.

[0019] Preferably, as an improvement, the dispersant is one or more of ethyl acetate, dibutyl phthalate, and butyl acetate.

[0020] Preferably, as an improvement, the thickening agent is one or more of ethyl cellulose, tributyl phosphate, hydrogenated castor oil, polyisobutylene, and nitrocellulose.

[0021] Preferably, as an improvement, the thixotropic agent is one or more of hydrogenated castor oil, organic bentonite, dibutoxyethane, polyamide wax, and tributyl phosphate.

[0022] Preferably, as an improvement, the surfactant is one or more of soybean lecithin, stearate, sodium octadecyl sulfate, sorbitan trioleate, oleic acid, and xylene.

[0023] Preferably, as an improvement, the stabilizer is one or more of 1,2-propanediol and dibutyltin dilaurate.

[0024] Preferably, as an improvement, the defoaming agent is one or more of trihydroxy polypropylene oxide ether and polyethylene glycol.

[0025] The scheme also provides a preparation method of tin-doped copper silver paste with a compounded organic carrier, characterized by comprising the following steps:

[0026] Step (1), preparation of the organic carrier: various organic carriers are weighed according to the corresponding mass ratio and placed in a beaker, then water bath heating and magnetic stirring are carried out until all the organic carriers are dissolved;

[0027] Step (2), preparation of the sealing slurry: silver powder, tin powder, copper powder, bismuth-boron-zinc mixed glass powder are weighed according to the proportion, and are fully mixed with the organic carrier prepared in step (1) in a three-dimensional mixer to obtain a uniform slurry;

[0028] Step (3), preparation of the sealing slurry: the above slurry is mixed and ground in a three-roll grinder to prepare a sample with a fineness of ≤5 µm and a viscosity of 3000-5000 mPa·s.

[0029] Preferably, as an improvement, in step (1), the constant temperature is 60-80℃, and the magnetic stirring time is 30-60 min.

[0030] Preferably, as an improvement, in step (2), the mixing time is 60-120 min, and the rotation speed is 30-50 r / min.

[0031] Preferably, as an improvement, in step (3), the grinding time is 60-120 min.

[0032] The application provides the application of the above-mentioned tin-doped copper-silver paste in vacuum glass sealing.

[0033] Compared with the prior art, the application has the following beneficial effects:

[0034] 1. The application uses mixed bismuthate glass powder and mixed metal powder to improve the bonding force between the silver layer and the glass substrate and the soldering wettability between the tin solder.

[0035] 2. The application effectively reduces the residual organic matter in the silver layer and improves the internal density by comparing and selecting the complex of the organic carrier, thereby improving the sealing strength.

[0036] 3. Compared with the traditional silver paste paint, the glass powder in the silver paste in the application has a more similar expansion coefficient with the base glass, so it is firm, stable, not easy to fall off, and has better durability.

[0037] 4. The application uses tin powder and copper powder instead of part of the silver powder, and the tin powder and the tin solder tape are bonded together and melted and solidified during sealing, which not only eliminates the tearing caused by thermal expansion and cold contraction, but also improves the soldering wettability between the silver paste coating and the tin solder, reduces the cost, and ensures the uniformity and integrity of the silver layer.

[0038] 5. The tin-copper-silver paste obtained by this method, after drying at 230℃ and sintering at 690℃, will not exhibit delamination, bubbles, or cracking in the metallic silver layer, and can form a regular and flat metallic silver layer on the glass surface. Furthermore, due to the good fluidity of the spherical silver powder, it ensures that the silver powder can penetrate through the screen and adhere to the glass during screen printing, ensuring the uniformity of screen printing, thereby effectively improving the bonding force between the metallic silver layer and the glass substrate, and further enhancing the weldability of vacuum glass.

[0039] 6. The production method in this scheme has a short cycle, simple operation, and flexible process. It does not require a strict and demanding processing environment, has low cost, and does not require excessively high sintering temperature. It has great advantages in improving production efficiency and reducing costs. Attached Figure Description

[0040] Figure 1 This is an erosion diagram of the glass matrix after the slurry is sintered according to Example 1 of the present invention.

[0041] Figure 2 This is an image showing the erosion of the glass matrix after sintering of the slurry in Comparative Example 1 of the present invention.

[0042] Figure 3 This is an image showing the erosion of the glass matrix after sintering of the slurry in Comparative Example 2 of the present invention.

[0043] Figure 4 This is an image showing the erosion of the glass matrix after sintering of the slurry in Comparative Example 4 of the present invention. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to embodiments, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following embodiments and experimental examples are conventional means well known to those skilled in the art, and the materials, reagents, etc. used are all commercially available. Unless otherwise specified, the technical means used in the following embodiments are conventional means well known to those skilled in the art.

[0045] Example 1

[0046] This embodiment is basically as follows: Figure 1 The following describes a tin-doped copper-silver paste with an organic carrier, comprising the following raw materials by mass percentage: 60-80 parts of a silver-tin-copper mixed metal powder, 5-10 parts of a bismuth-boron-zinc mixed glass powder, and 20-30 parts of an organic carrier; the silver-tin-copper mixed metal powder comprises the following raw materials by mass percentage: 80-90% silver powder, 0-10% tin powder, and 0-10% copper powder; and the mass percentage of silver powder in the silver paste is ≥60%; in this embodiment, the specific raw materials of the silver paste are as follows: 65 parts silver powder, 5 parts tin powder, 5.5 parts bismuth-boron-zinc mixed glass powder, and 24.5 parts organic carrier. The average particle size of the silver-tin mixed metal powder is 1-5 µm, specifically 2 µm in this embodiment.

[0047] The bismuth boron zinc mixed glass powder is specifically one or more of bismuthate glass powder, sodium calcium silicon glass powder, and zinc borosilicate glass powder, and in the embodiment, is specifically two kinds of bismuthate mixed glass powder (bismuthate mixed glass powder 1 and bismuthate mixed glass powder 2) mixed according to a mass ratio of 1:1.

[0048] The components and mass percentages of the bismuthate mixed glass powder 1 are as follows: Na2O 1.4%, SiO2 1.5%, Al2O3 0.5%, ZnO 13.5%, ZrO2 0.4%, Bi2O3 80%, and BaO 2.7%, the average particle size is 2 µm, and the expansion coefficient is 90×10 -7 / ℃; the components and mass percentages of the bismuthate mixed glass powder 2 are as follows: SiO2 2.6%, Al2O3 2.8%, ZnO 17%, ZrO2 0.6%, Bi2O3 77%, the average particle size is 2 µm, and the expansion coefficient is 80×10 -7 / ℃.

[0049] The organic carrier includes raw materials with the following mass percentages: organic solvent 55-65%, dispersant 10-20%, thickening agent 3-9%, thixotropic agent 0.5-2%, surfactant 1-2%, stabilizer 5-15%, and defoaming agent 5-15%.

[0050] The organic solvent is one or more of terpineol, sodium stearate, ethyl cellulose, dibutoxyethane, polyamide wax, sodium octadecyl sulfate, soybean lecithin, 1,2-propanediol, polyisobutylene, dibutyltin dilaurate, diethylene glycol ethyl ether, tributyl phosphate, ethyl acetate, butyl acetate, trihydroxy polypropylene oxide ether, sorbitan trioleate, dibutyl phthalate, tributyl citrate, polyethylene glycol, oleic acid, and xylene; the dispersant is one or more of ethyl acetate, dibutyl phthalate, and butyl acetate; the thickening agent is one or more of ethyl cellulose, tributyl phosphate, hydrogenated castor oil, polyisobutylene, and nitrocellulose; the thixotropic agent is one or more of hydrogenated castor oil, organic bentonite, dibutoxyethane, polyamide wax, and tributyl phosphate; the surfactant is one or more of soybean lecithin, stearate, sodium octadecyl sulfate, sorbitan trioleate, oleic acid, and xylene; the stabilizer is one or more of 1,2-propanediol and dibutyltin dilaurate; and the defoaming agent is one or more of trihydroxy polypropylene oxide ether and polyethylene glycol.

[0051] Specifically, the composition and mass percentages of the organic carrier in the embodiment are as follows: terpineol 61%, ethyl cellulose 5.7%, ethyl acetate 13.5%, 1,2-propanediol 10%, trihydroxy polypropylene oxide ether 7%, hydrogenated castor oil 1.5%, and soybean lecithin 1.3%.

[0052] The present application also provides a preparation method of the tin-doped copper-silver paste compounded with the organic carrier, which specifically comprises the following steps:

[0053] Step (1), preparation of the organic carrier: various organic carriers are weighed according to the corresponding mass ratio and placed in a beaker, then heated to 60-80°C in a water bath, and magnetically stirred for 30-60 min. In this embodiment, the water bath is heated to 70°C, and the magnetic stirring is performed for 30 min, until all the organic carriers are dissolved.

[0054] Step (2), preparation of the sealing paste: silver powder, tin powder, copper powder and mixed glass powder are weighed according to the proportion, and then fully mixed with the organic carrier prepared in step (1) in a three-dimensional mixer for 60-120 min at a speed of 30-50 r / min. In this embodiment, the mixing is performed for 75 min at a speed of 50 r / min, and a uniform paste is obtained.

[0055] Step (3), preparation of the sealing paste: the above paste is mixed and ground in a three-roll grinder for 60-120 min. In this embodiment, the grinding is performed for 100 min, and a sample with a fineness of ≤5 µm and a viscosity of 3000-5000 mPa·s is prepared.

[0056] The prepared sealing paste is printed on a glass substrate by silk screen printing, with a thickness of 15 µm±1 µm. After drying at 230°C for 30 min and high-temperature sintering at 690°C for 10 min, the silver film is welded on the surface of the sintered silver film, and the welding performance of the paste is tested.

[0057] Example 2

[0058] This embodiment is basically the same as Example 1, except that the tin-doped copper-silver paste compounded with the organic carrier comprises the following raw materials by mass fraction: silver powder 65 parts, tin powder 5 parts, bismuth-boron-zinc mixed glass powder 2.75 parts (specifically, bismuthate glass powder and sodium calcium silicon glass powder are mixed in a mass ratio of 1:1), sodium calcium silicon glass powder 2.75 parts, and organic carrier 24.5 parts.

[0059] The bismuthate glass powder comprises the following raw materials by mass percentage: Na2O 1.4%, SiO2 1.5%, Al2O3 0.5%, ZnO 13.5%, ZrO2 0.4%, Bi2O3 80%, and BaO 2.7%, with an average particle size of 2 µm and an expansion coefficient of 90×10 -7 / ℃; the sodium calcium silicon glass powder comprises the following raw materials by mass percentage: NaO 12.2%, MgO 3.3%, SiO2 75.5%, Al2O3 0.3%, and CaO 8.7%, with an average particle size of 2 µm and an expansion coefficient of 90×10-7 / ℃.

[0060] Example 3

[0061] This example is basically the same as Example 1, except that the tin-doped copper-silver paste compounded with the organic carrier comprises the following mass fraction of raw materials: silver powder 65 parts, tin powder 5 parts, bismuth-boron-zinc mixed glass powder 6 parts (specifically, bismuthate glass powder, sodium calcium silicon glass powder, and borosilicate zinc glass powder mixed in a mass ratio of 1:1:1), and organic carrier 24 parts.

[0062] The components and mass percentages of the bismuthate glass powder are as follows: Na2O 1.4%, SiO2 1.5%, Al2O3 0.5%, ZnO 13.5%, ZrO2 0.4%, Bi2O3 80%, and BaO 2.7%, with an average particle size of 2 µm and an expansion coefficient of 90×10 -7 / ℃. -7 The components and mass percentages of the borosilicate zinc glass powder are as follows: B2O3 50%, ZnO 30%, and Na2SiO3 20%, with an average particle size of 2 µm and an expansion coefficient of 110×10 -7 / ℃.

[0063] Example 4

[0064] This example is basically the same as Example 1, except that the tin-doped copper-silver paste compounded with the organic carrier comprises the following mass fraction of raw materials: silver powder 65 parts, copper powder 5 parts, silver-tin mixed metal powder with an average particle size of 1 µm, bismuth-boron-zinc mixed glass powder 5.5 parts, and organic carrier 24.5 parts.

[0065] Example 5

[0066] This example is basically the same as Example 1, except that the tin-doped copper-silver paste compounded with the organic carrier comprises the following mass fraction of raw materials: silver powder 66 parts, tin powder 5.0 parts, silver-tin mixed metal powder with an average particle size of 1 µm, bismuth-boron-zinc mixed glass powder 5.5 parts, and organic carrier 23.42 parts.

[0067] Example 6

[0068] This example is basically the same as Example 1, except that the tin-doped copper-silver paste compounded with the organic carrier comprises the following mass fraction of raw materials: silver powder 65 parts, tin powder 5 parts, bismuth-boron-zinc mixed glass powder 6 parts (specifically, bismuthate glass powder), and organic carrier 24 parts.

[0069] The components and mass percentage of the bismuthate glass powder are: Na2O 1.4%, SiO2 1.5%, Al2O3 0.5%, ZnO 13.5%, ZrO2 0.4%, Bi2O3 80%, and BaO 2.7%, the average particle size is 2 µm, and the expansion coefficient is 90×10 -7 / ℃.

[0070] In the present comparative example, a single bismuthate glass powder is used, and the proportion of the organic carrier is increased by 5 parts compared with example 1. The viscosity and leveling property of the silver paste are adjusted. After drying at 230℃ and sintering at 690℃, the silver paste layer is relatively stable, and the welding effect is good.

[0071] Comparative example 1

[0072] The present comparative example is basically the same as example 1, except that the tin-doped copper silver paste compounded with the organic carrier includes the following mass fractions of raw materials: silver powder 55 parts, tin powder 10 parts, bismuth-boron-zinc mixed glass powder 10.5 parts, and organic carrier 24.5 parts.

[0073] In the present comparative example, the proportion of silver powder in the silver paste raw materials is less than 60%, and the amount of tin powder and glass powder is too much. The tin and silver form a tin-silver alloy compound, which leads to too little silver powder and too much glass powder on the surface of the silver paste layer, so that the silver paste layer cannot be fully infiltrated with the solder, and the welding fails.

[0074] Comparative example 2

[0075] The present comparative example is basically the same as example 1, except that the tin-doped copper silver paste compounded with the organic carrier includes the following mass fractions of raw materials: silver powder 55 parts, tin powder 5 parts, bismuth-boron-zinc mixed glass powder 15.5 parts, and organic carrier 24.5 parts.

[0076] In the present comparative example, the proportion of silver powder in the silver paste raw materials is less than 60%, and the amount of glass powder is too much, which leads to too much glass powder on the surface of the prepared silver paste layer, so that the silver paste layer cannot be fully infiltrated with the solder, and the welding fails.

[0077] Comparative example 3

[0078] The present comparative example is basically the same as example 1, except that the tin-doped copper silver paste compounded with the organic carrier includes the following mass fractions of raw materials: silver powder 65 parts, tin powder 5 parts, bismuth-boron-zinc mixed glass powder 3 parts (specifically, one kind of bismuthate glass powder), and organic carrier 29.5 parts.

[0079] The components and mass percentage of the bismuthate glass powder are: Na2O 1.4%, SiO2 1.5%, Al2O3 0.5%, ZnO 13.5%, ZrO2 0.4%, Bi2O3 80%, and BaO 2.7%, the average particle size is 2 µm, and the expansion coefficient is 90×10-7 / ℃.

[0080] In the present comparative example, too little glass powder is used, so that the expansion coefficient of the paste is greatly different from the expansion coefficients of the solder and the glass substrate, thereby reducing the uniformity and integrity of the soldering between the silver paste layer and the solder and the glass substrate, resulting in the peeling of the soldering layer. In addition, in the present comparative example, the amount of the organic carrier is increased to 29.5 parts, and the amount of the overall component in the silver paste is relatively high. The relatively high amount of the organic carrier changes the viscosity and leveling property of the silver paste. After drying at 230°C and sintering at 690°C, the silver paste layer peels off or voids are generated, resulting in an unsatisfactory soldering effect.

[0081] Comparative Example 4

[0082] The present comparative example is basically the same as Example 1, except that the tin-doped copper silver paste compounded with the organic carrier comprises the following raw materials by mass fraction: silver powder 58 parts, tin powder 6 parts, copper powder 6 parts, bismuth-boron-zinc mixed glass powder 5.5 parts, and organic carrier 24.5 parts.

[0083] In the present comparative example, the amount of silver powder accounts for less than 60% in the silver paste raw materials, and the amounts of tin powder and copper powder are each 6 parts. Since Sn, Ag and Cu are all easily oxidized elements, the silver paste layer sintered out is oxidized too fast, with too much surface oxide, which cannot be soldered.

[0084] Comparative Example 5

[0085] The present comparative example is basically the same as Example 1, except that the tin-doped copper silver paste compounded with the organic carrier comprises the following raw materials by mass fraction: silver powder 60 parts, tin powder 2 parts, bismuth-boron-zinc mixed glass powder 5.5 parts, and organic carrier 32.5 parts.

[0086] In the present comparative example, the amount of the organic carrier accounts for 32.5%, and the silver paste prepared has low viscosity. The silver paste layer after sintering is prone to voids and tearing, and the soldering effect is not good.

[0087] Comparative Example 6

[0088] The present comparative example is basically the same as Example 1, except that the tin-doped copper silver paste compounded with the organic carrier comprises the following raw materials by mass fraction: silver powder 65%, tin powder 5%, bismuth-boron-zinc mixed glass powder 3% (bismuthate mixed glass powder 1 and bismuthate mixed glass powder 2 combined in a 1:1 ratio), and organic carrier 27%.

[0089] In the present comparative example, too little mixed glass powder results in that the silver paste layer cannot be firmly bonded with the glass substrate, the silver paste layer peels off, and the soldering experiment cannot be performed.

[0090] Example 1: Soldering performance of the tin-doped copper silver paste compounded with the organic carrier in the present scheme

[0091]

Detection Standard

[0092]

Detection Method

[0093] At room temperature, using SnAgCu solder, the silver paste sintered coating prepared in the examples is subjected to welding experiment.

[0094]

Sintering Stability

[0095] Among them, the stability is divided into "poor", "general", "better", and "good", wherein:

[0096] "poor" means "cracking / peeling occurs after 0-2 days";

[0097] "general" means "cracking / peeling occurs after 2-4 days";

[0098] "better" means "cracking / peeling occurs after 6-8 days";

[0099] "good" means "no cracking / peeling occurs after 10 days".

[0100] "whether it falls off" is divided into "yes" and "no" two levels, wherein:

[0101] "yes" means "peeling off within 0-2 days";

[0102] "no" means "no peeling off after 10 days".

[0103]

Welding Effect

[0104] The welding effect is divided into "poor", "general", and "good" three levels, wherein:

[0105] "poor" means "unable to weld";

[0106] "general" means "weldable, but can be scraped off with a small knife";

[0107] "good" means "weldable and cannot be scraped off with a small knife".

[0108] The tin-doped copper silver paste prepared in the examples 1-6 and the comparative examples 1-6 is subjected to welding performance test, and the results are shown in Table 1.

[0109] Table 1 soldering performance results of tin-doped copper paste prepared in Examples 1-6 and Comparative Examples 1-6

[0110]

[0111] The test results show that the inventors of the present application encountered the following technical difficulties in producing the metal paste layer (referred to as silver paste layer in the present application) for vacuum glass: after the silver paste is printed into a silver paste layer, the silver paste layer is prone to bubbles and cracks when soldering with solder to achieve vacuum glass sealing, which causes the soldered silver paste layer to fall off and tear, resulting in a low soldering effect, which in turn affects the performance of the vacuum glass, and even causes the vacuum glass to be unable to be used normally.

[0112] The inventors explored the causes of the above phenomena and tried various means to solve the above problems, and finally found that the causes of the unsatisfactory soldering performance of the silver paste layer are as follows: the ratio of each raw material in the silver paste, and the expansion coefficient of the silver paste. The main performance is that the leveling property and viscosity of the silver paste need to be adjusted to an appropriate level, and the expansion coefficient of the silver paste needs to be adjusted so that the expansion coefficients of the silver paste, the content, and the glass substrate tend to be consistent, thereby improving the uniformity and integrity of the three in the soldering process. In addition, the cost of silver powder is relatively high, and adjusting the amount of various metal powders in the mixed metal powder in the paste can make the silver paste have higher performance while reducing the cost of raw materials.

[0113] Referring to Table 1 and the examples and comparative examples, in terms of the ratio of each raw material in the silver paste, when a lower content of silver powder is used (less than 60% of the silver paste raw material), even if the amount of other metal powder is increased (such as the amount of tin powder is increased to 10 parts in Comparative Example 1, and the amount of tin powder and copper powder is increased to 6 parts each in Comparative Example 4), and the amount of glass powder is increased (such as the amount of glass powder is increased to 15.5 parts in Comparative Example 2), it will cause the silver paste layer to have bubbles and cracks during soldering / sintering, thereby causing the silver paste layer to fall off, resulting in poor soldering effect and affecting the soldering performance of the silver paste. It is fully demonstrated that the silver powder in the silver paste can be partially replaced by tin powder and copper powder, but when the content of silver powder is less than 60% of the silver paste raw material, too little silver powder makes the surface of the silver paste unable to be wetted by the solder, thereby the contact angle is too large and the silver paste cannot be soldered. When too low an amount of glass powder is used (such as the amount of glass powder is as low as 3 parts in Comparative Example 3), the expansion coefficient of the paste is greatly different from the expansion coefficients of the solder and the glass substrate, thereby reducing the uniformity and integrity of the soldering between the silver paste layer and the solder and the glass substrate, resulting in the soldering layer falling off. And using too much organic carrier (such as the relatively large amount of organic carrier in Comparative Example 3, and 32.5% of the organic carrier in Comparative Example 5), the leveling property of the paste changes, and the silver paste layer after screen printing has phenomena such as cavitation, falling off, and tearing, which cannot meet the requirements of soldering.

[0114] Regarding the adjustment of the expansion coefficient of silver paste, the use of a single type of glass powder (as in Example 6), or a combination of two or three types of glass powder (as in Examples 1-5), can improve the welding stability of the silver paste. However, when too little glass powder is used (as in Comparative Example 3, the amount of glass powder is as low as 3 parts), the expansion coefficient of the paste differs greatly from that of the solder and the glass substrate, thereby reducing the uniformity and integrity of the welding between the silver paste layer and the solder and the glass substrate, leading to the detachment of the weld layer.

[0115] The above results indicate that, by adjusting the ratio of silver, tin, and copper metal powders and using mixed glass powder, Examples 1-6 of the present invention achieve a coefficient of thermal expansion closer to that of the substrate glass, resulting in less erosion of the substrate glass, stronger and more stable bonding, less detachment, no tearing, and better durability. Furthermore, by replacing some silver powder with tin and copper powder, tearing caused by thermal expansion and contraction is eliminated, and the welding wettability between the silver paste coating and the tin solder is improved. The production process is simple, and costs are reduced without requiring excessively high sintering temperatures. Specifically, the silver paste layers prepared in Examples 1-6 exhibit high bonding strength with the glass substrate and show no tearing; in contrast, the silver paste layers prepared in Comparative Examples 1-6 show low welding strength when bonded to the glass substrate, and all exhibit detachment, cracking, tearing, and bubbles, resulting in poor welding performance and affecting the normal use of the vacuum glass.

[0116] In addition, such as Figures 1 to 4 As shown, the silver paste obtained in Example 1 ( Figure 1 The sintered silver paste exhibits less erosion of the glass substrate and lacks microcracks within the glass matrix, demonstrating excellent performance; while the silver pastes obtained in Comparative Examples 1-2 and 4 (as shown in Figures 1-4) show less erosion. Figures 2 to 4 As shown, the sintering process caused severe erosion of the glass substrate, especially in comparative examples 2 and 4 (as shown). Figures 3 to 4 As shown, sintering causes severe erosion of the glass substrate and numerous cracks within the glass matrix, significantly reducing its performance and service life.

[0117] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A tin-doped copper-silver paste with an organic carrier, characterized in that: The raw materials include the following parts by weight: 60-80 parts of silver-tin-copper mixed metal powder, 5-10 parts of bismuth-boron-zinc mixed glass powder, and 20-30 parts of organic carrier; the silver paste contains ≥60% silver powder by weight; the silver-tin-copper mixed metal powder includes the following raw materials by weight: 80-90% silver powder, 0-10% tin powder, and 0-10% copper powder; the average particle size of the silver-tin-copper mixed metal powder is 1-5 µm. The preparation method of tin-doped copper-silver paste with organic carrier includes the following steps: Step (1), Preparation of organic carriers: Weigh various organic carriers according to their corresponding mass ratios and place them in a beaker. Then, heat them in a water bath and stir them magnetically until all organic carriers are completely dissolved. Step (2), preparation of sealing slurry: weigh silver powder, tin powder, copper powder, and bismuth boron zinc mixed glass powder according to the proportion, and mix them thoroughly with the organic carrier prepared in step (1) in a three-dimensional mixer to obtain a uniform slurry; Step (3), preparation of sealing slurry: The above slurry is mixed and ground in a three-roll mill to prepare a sample with a fineness ≤5µm and a viscosity of 3000~5000 mPa·s.

2. The tin-doped copper-silver paste with an organic carrier according to claim 1, characterized in that: The bismuth-boron-zinc mixed glass powder is one or more of bismuthate glass powder, soda-lime-silica glass powder, and zinc borosilicate glass powder; the bismuthate glass powder has an average particle size of 1–5 µm and a coefficient of thermal expansion of 80–110 × 10⁻⁶. -7 / ℃, comprising the following components by mass fraction: 75–80% Bi₂O₃, 15–20% ZnO, and 1–5% B₂O₃; the sodium-calcium-silica glass powder has an average particle size of 1–5 µm and a coefficient of thermal expansion of 80–100 × 10⁻⁶. -7 The zinc borosilicate glass powder, at a temperature of / ℃, comprises the following components by mass fraction: 12–15% NaO, 7–15% Ca2O, and 70–80% SiO2; the average particle size of the zinc borosilicate glass powder is 1–5 µm, and the coefficient of thermal expansion is 100–160 × 10⁻⁶. -7 / ℃, which includes the following components by mass fraction: 40~60% B2O3, 20~35% ZnO, 15~25% Na2SiO3.

3. The tin-doped copper-silver paste with an organic carrier according to claim 1, characterized in that: The organic carrier comprises the following raw materials in the following mass percentages: 55-65% organic solvent, 10-20% dispersant, 3-9% thickener, 0.5-2% thixotropic agent, 1-2% surfactant, 5-15% stabilizer, and 5-15% defoamer.

4. The tin-doped copper-silver paste with an organic carrier according to claim 3, characterized in that: The organic solvent is one or more of the following: terpineol, sodium stearate, ethyl cellulose, dibutoxyethane, polyamide wax, sodium octadecyl sulfate, soybean lecithin, 1,2-propanediol, polyisobutylene, dibutyltin dilaurate, diethylene glycol ethyl ether, tributyl phosphate, ethyl acetate, butyl acetate, trihydroxypolyoxypropylene ether, sorbitan trioleate, dibutyl phthalate, tributyl citrate, polyethylene glycol, oleic acid, and xylene.

5. The tin-doped copper-silver paste with an organic carrier according to claim 3, characterized in that: The dispersant is one or more of ethyl acetate, dibutyl phthalate, and butyl acetate.

6. The tin-doped copper-silver paste with an organic carrier according to claim 3, characterized in that: The thickener is one or more of ethyl cellulose, tributyl phosphate, hydrogenated castor oil, polyisobutylene, and nitrocellulose; the thixotropic agent is one or more of hydrogenated castor oil, organobentonite, dibutoxyethane, polyamide wax, and tributyl phosphate.

7. The tin-doped copper-silver paste with an organic carrier according to claim 6, characterized in that: The surfactant is one or more of soybean lecithin, stearate, sodium octadecyl sulfate, sorbitan trioleate, oleic acid, and xylene; the stabilizer is one or more of 1,2-propanediol and dibutyltin dilaurate; and the defoamer is one or more of trihydroxypolypropylene ether and polyethylene glycol.

8. A method for preparing a tin-doped copper-silver paste with an organic carrier according to any one of claims 1 to 7, characterized in that: Includes the following steps: Step (1), Preparation of organic carriers: Weigh various organic carriers according to their corresponding mass ratios and place them in a beaker. Then, heat them in a water bath and stir them magnetically until all organic carriers are completely dissolved. Step (2), preparation of sealing slurry: weigh silver powder, tin powder, copper powder, and bismuth boron zinc mixed glass powder according to the proportion, and mix them thoroughly with the organic carrier prepared in step (1) in a three-dimensional mixer to obtain a uniform slurry; Step (3), preparation of sealing slurry: The above slurry is mixed and ground in a three-roll mill to prepare a sample with a fineness ≤5µm and a viscosity of 3000~5000 mPa·s.

9. A method for preparing a tin-doped copper-silver paste with an organic carrier according to claim 8, characterized in that: In step (1), the constant temperature of the water bath heating is 60-80℃, and the magnetic stirring time is 30-60 min; in step (2), the mixing time is 60-120 min, and the rotation speed is 30-50 r / min; in step (3), the grinding time is 60-120 min.

10. The application of the tin-doped copper-silver paste with organic carrier prepared by the method according to any one of claims 8 to 9 in vacuum glass sealing.

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