Organic silver paste and preparation method and application thereof

Abstract

The invention discloses organic silver paste and a preparation method and application thereof, and relates to the technical field of electronic paste. The organic silver paste comprises the following components in parts by weight: 6-45 parts of inorganic silver powder; 5-30 parts of organic silver; 5-20 parts of glass powder; 10-30 parts of an organic carrier; 8-32 parts of organic acid; 1-5 parts of an additive; the organic carrier comprises an organic adhesive and a solvent, and the mass ratio of the organic adhesive to the organic silver to the organic acid is 1: (1-4): (1-6); the mass percent of groups capable of forming hydrogen bonds in the organic adhesive is 5-10%; the inorganic silver powder comprises inorganic silver powder A and inorganic silver powder B, and the mass ratio of the inorganic silver powder A to the inorganic silver powder B to the organic silver is 1: (0.5-4): (0.5-4). The organic silver paste disclosed by the invention has excellent conductivity and printing property.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic pastes, and in particular to an organic silver paste, a preparation method thereof, and an application thereof. Background Art

[0002] Conductive silver pastes are widely used in the preparation of electronic components, conductive layers of circuits, and conductive structures, such as printed circuit boards, thin-film solar cells, touch screens, chip resistors, etc. Generally, they are required to have good conductivity, strong adhesion, and hydrodynamic characteristics suitable for printing. The conductive silver paste for chip resistors is generally formed by using silver powder as the conductive main body, glass powder as the bonding phase, and mixing with an organic carrier. However, the conductivity and printability of such a made silver paste often cannot meet the application requirements of different specifications of chip resistors simultaneously.

[0003] Currently, most manufacturers will distinguish between conductive silver pastes for chip resistors above the 0402 specification and those below the 0402 specification during application. For chip resistors with a specification of 0402 and below, on the one hand, the change window of the rheological curve of the paste is relatively narrow, making it difficult to ensure printability. On the other hand, in order to ensure good adhesion, a relatively large proportion of glass powder is added, resulting in more longitudinal holes and poor denseness. Therefore, there is an urgent need to develop a conductive silver paste suitable for chip resistors with a specification of 0402 and below. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide an organic silver paste, a preparation method thereof, and an application thereof. The present invention makes the organic silver paste have excellent conductivity and printability by compounding organic silver, inorganic silver powder, organic carrier, glass powder, organic acid, and additives.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides an organic silver paste, comprising the following components in parts by weight:

[0007] Inorganic silver powder 6 - 45 parts; organic silver 5 - 30 parts; glass powder 5 - 20 parts; organic carrier 10 - 30 parts; organic acid 8 - 32 parts; additive 1 - 5 parts;

[0008] The organic carrier includes an organic binder and a solvent, and the mass ratio of the organic binder, organic silver, and organic acid is 1:(1 - 4):(1 - 6); the mass percentage of the hydrogen bond-forming groups in the organic binder is 5 - 10%;

[0009] The inorganic silver powder includes inorganic silver powder A and inorganic silver powder B, and the mass ratio of inorganic silver powder A, inorganic silver powder B, and organic silver is 1:(0.5 - 4):(0.5 - 4).

[0010] Preferably, the mass ratio of the organic binder, organic silver, and organic acid is 1:(1.6 - 3.5):(1.6 - 5).

[0011] More preferably, the mass ratio of the organic binder, organic silver, and organic acid is 1:(2 - 3):(2 - 3.5).

[0012] In the present invention, while the organic binder binds the conductive particles and regulates the rheology of the paste, a gelation network will spontaneously form between the organic binder, organic acid, and organic silver due to hydrogen bonding, forming a bridging effect between the organic component and the inorganic component. This can effectively prevent the agglomeration of inorganic silver powder and reduce the interfacial resistance. When the amount of organic acid and organic silver is too small, the agglomeration of inorganic silver powder leads to poor dispersibility and conductivity. When the amount of organic acid and organic silver is too large, the viscosity and thixotropy are too large, which is not suitable for printing. Therefore, by controlling the mass ratio of the organic binder, organic acid, and organic silver within the above range in the present invention, the inorganic silver powder is not likely to agglomerate, and the dispersibility of the organic silver paste is improved, which is conducive to improving the conductivity of the silver paste and ensuring the printability of the silver paste at the same time.

[0013] Moreover, by limiting the content of hydrogen-bond-forming groups in the organic binder in the present invention, it is beneficial to further ensure the hydrogen bonding between the organic binder, organic acid, and organic silver, thereby ensuring the dispersibility of the silver paste and the interfacial resistance after printing. If the amount of hydrogen-bond-forming groups is too small, the hydrogen bonding between the organic binder, organic acid, and organic silver is weak, which is not sufficient to ensure the dispersibility. If the amount of hydrogen-bond-forming groups is too large, the viscosity and thixotropy of the paste are too high, which is not conducive to printing.

[0014] The present invention also facilitates the improvement of the conductivity and printability of the organic silver paste through the combination of inorganic silver powder A, inorganic silver powder B, and organic silver. Specifically, organic silver and inorganic silver powder B can improve the contact between the organic carrier and inorganic silver powder A, enhancing the conductivity. The voids between inorganic silver powder A need to be filled by inorganic silver powder B, thereby reducing the longitudinal holes generated in the sintering step.

[0015] Preferably, the hydrogen-bond-forming groups include any one or more of hydroxyl, amino, carbonyl, and carboxyl.

[0016] Preferably, the mass percentage of the hydrogen-bond-forming groups in the organic binder is any one or two range values among 5%, 6%, 7%, 8%, 9%, and 10%.

[0017] Preferably, the additive is at least one of zirconia, copper oxide, nickel oxide, and zinc oxide, and the particle size of the additive is 1 - 10 μm.

[0018] More preferably, the additive includes zirconia, nickel oxide, and zinc oxide, and the mass ratio of zirconia, nickel oxide, and zinc oxide is 1:1:(0.5 - 2).

[0019] More preferably, the mass ratio of zirconia, nickel oxide, and zinc oxide is any one or the range value of two of 1:1:0.5, 1:1:1, 1:1:1.5, and 1:1:2.

[0020] Preferably, the particle size range of the inorganic silver powder A is 0.5 - 3 μm, and the particle size range of the inorganic silver powder B is 200 - 500 nm.

[0021] Preferably, the mass ratio of the inorganic silver powder A, the inorganic silver powder B, and the organic silver is 1:(1 - 3.5):(1 - 3.5).

[0022] More preferably, the mass ratio of the inorganic silver powder A, the inorganic silver powder B, and the organic silver is 1:(1.5 - 3):(1.5 - 3).

[0023] Further preferably, the mass ratio of the inorganic silver powder A, the inorganic silver powder B, and the organic silver is 1:(1.5 - 2.5):(1.5 - 2.5).

[0024] Preferably, the organic silver is at least one of silver saturated fatty acid, silver citrate, silver oxalate, and silver benzoate, and the silver saturated fatty acid can be silver acetate, silver isooctanoate, silver decanoate, and silver neodecanoate.

[0025] Preferably, the particle size of the organic silver is 1 - 10 μm, and more preferably 3 - 5 μm.

[0026] Preferably, the organic acid is at least one of saturated fatty acid, citrate, oxalate, and benzoate, and the saturated fatty acid can be acetic acid, isooctanoic acid, decanoic acid, and neodecanoic acid.

[0027] Further preferably, the organic acid and the organic silver have the same organic acid radical.

[0028] Preferably, the organic binder is at least one of ethyl cellulose, polymerized rosin, epoxy resin, polyurethane resin, and acrylic resin.

[0029] Preferably, the solvent includes at least one of terpineol, butyl carbitol, butyl carbitol acetate, octanol, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, and propylene glycol monobutyl ether.

[0030] Preferably, the glass powder is at least one of Bi-Zn-B-Si system, Bi-Ti-B-Si system, Si-Ca-Al-Zr system, and Si-Ca-Al-Bi system, and does not contain lead and cadmium.

[0031] More preferably, the Bi-Zn-B-Si system comprises components in the following mass percentages:

[0032] SiO 2 : 20-30%; BaO: 20-30%; ZnO: 10-20%; Bi 2 O 3 : 10-20%; B 2 O 3 : 8-12%; Na 2 O: 2-6%; K 2 O: 3-8%.

[0033] More preferably, the Bi-Ti-B-Si system comprises components in the following mass percentages:

[0034] SiO 2 : 30-40%; BaO: 10-20%; TiO 2 : 10-20%; Bi 2 O 3 : 10-20%; B 2 O 3 : 5-10%; Na 2 O: 1-5%; K 2 O: 1-5%.

[0035] More preferably, the Si-Ca-Al-Zr system comprises components in the following mass percentages:

[0036] SiO 2 : 35-42%; Al 2 O 3 : 30-35%; CaO: 8-12%; ZrO 2 : 1-5%; B 2 O 3 : 2-8%; Na 2 O: 1-3%; K 2 O: 1-5%.

[0037] More preferably, the Si-Ca-Al-Bi system comprises components in the following mass percentages:

[0038] SiO 2 : 48-55%; Al 2 O 3 : 15-25%; CaO: 8-12%; Bi 2 O 3 : 5-10%; B 2 O 3 : 1-5%; Na 2 O: 1-2%; K2 O: 1 - 3%.

[0039] Preferably, the viscosity of the organic silver paste at 25°C and a viscometer rotation speed of 10 rpm is 110 - 160 Pa·s, and the thixotropy index at a rotation speed of 10 rpm / 50 rpm is 1.5 - 3.5.

[0040] In a second aspect, the present invention also provides a method for preparing an organic silver paste, comprising the following steps:

[0041] S1. Mix and disperse inorganic silver powder B, organic silver, organic acid, and solvent to obtain mixture one;

[0042] S2. Mix and disperse inorganic silver powder A, glass powder, additive, organic binder, and solvent to obtain mixture two;

[0043] S3. Mix and disperse mixture one and mixture two to obtain the organic silver paste.

[0044] Due to the strong hydrogen bond interaction between inorganic silver powder B and organic silver, directly with the organic

[0045] In the present invention, inorganic silver powder B, organic silver, organic acid, and solvent are first mixed and dispersed evenly, and then mixed and dispersed with inorganic silver powder A, glass powder, additive, organic binder, and solvent, which is beneficial to improving the dispersion effect between components, thereby improving the performance of the organic silver paste.

[0046] In a third aspect, the present invention also provides an application of the organic silver paste on electronic components, comprising the following steps:

[0047] Print the above-mentioned organic silver paste on the electronic component substrate, and a conductive silver layer can be obtained after drying and sintering.

[0048] Preferably, the drying temperature is 100 - 200°C, and the drying time is 5 - 20 minutes.

[0049] Preferably, the sintering temperature for sintering is 750 - 950°C, and the heat preservation time is 10 - 20 minutes.

[0050] Compared with the prior art, the beneficial effects of the present invention are:

[0051] By compounding organic silver, inorganic silver powder, glass powder, organic carrier, organic acid, and additive, the organic silver paste of the present invention has excellent conductivity and printability. Detailed Embodiments

[0052] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments, but the protection scope and implementation manner of the present invention are not limited thereto.

[0053] For the materials, reagents, etc. used in the following examples, unless otherwise specified, they are reagents and materials that can be obtained commercially.

[0054] Example 1

[0055] This example discloses an organic silver paste, which comprises the following components in parts by weight:

[0056] Inorganic silver powder A: 10 parts; inorganic silver powder B: 12.9 parts; organic silver: 10 parts, and the type of the organic silver is silver isooctanoate; organic acid: 17.3 parts, and the type of the organic acid is isooctanoic acid; organic carrier: 30 parts; glass powder: 20 parts; additive: 5 parts; the mass ratio of the organic binder, organic silver and organic acid is 1:3.33:2.31.

[0057] The organic carrier comprises 7.5 parts of organic binder and 22.5 parts of solvent; the organic binder is acrylic resin and the solvent is terpineol.

[0058] The mass ratio of inorganic silver powder A, inorganic silver powder B and organic silver is 1:1.29:1.

[0059] The type of the glass powder is G1, and it comprises the following components in mass percentage: SiO 2 : 25%, BaO: 25%, ZnO: 15%, Bi 2 O 3 : 15%, B 2 O 3 : 10%, Na 2 O: 5%, K 2 O: 5%.

[0060] The additive comprises zirconia, nickel oxide and zinc oxide, and the mass ratio of the three is 1:1:0.5.

[0061] This example also discloses a preparation method of the organic silver paste, which comprises the following steps:

[0062] S1. Mix and disperse inorganic silver powder B, organic silver, organic acid and solvent in a three-roll mill for 1 h to obtain mixture one;

[0063] S2. Mix and disperse inorganic silver powder A, glass powder, additive and organic binder in a three-roll mill for 1 h to obtain mixture two;

[0064] S3. Mix and disperse mixture one and mixture two in a three-roll mill for 1 h to obtain the organic silver paste.

[0065] This example also discloses an application of the organic silver paste on electronic components, which comprises the following steps:

[0066] The above-mentioned organic silver paste is printed on the substrate of the electronic component, dried at 150 °C for 10 minutes, then sintered in a mesh belt furnace at a temperature of 850 °C for a holding time of 10 minutes, and then an electronic component is obtained after processes such as printing and sintering, strip arranging and granule folding, electroplating, etc.

[0067] Examples 2 to 17, Comparative Examples 1 to 8

[0068] The differences between the organic silver pastes disclosed in Examples 2 to 17 and Comparative Examples 1 to 8 and Example 1 are only that: there are differences in the types or contents of the components in the organic silver paste, as shown in Tables 1 to 4 specifically:

[0069] Table 1 Types and Contents of Inorganic Components

[0070]

[0071]

[0072]

[0073] The specific types and compositions of the glass powders involved in Table 1 are shown in Table 2 specifically:

[0074] Table 2

[0075] G1 <![CDATA[SiO 2 : 25%, BaO: 25%, ZnO: 15%, Bi 2 O 3 : 15%, B 2 O 3 : 10%, Na 2 O: 5%, K 2 O: 5%]]> G2 <![CDATA[SiO 2 : 35%, BaO: 15%, TiO2: 15%, Bi 2 O 3 : 15%, B 2 O 3 : 10%, Na 2 O: 5%, K 2 O: 5%]]> G3 <![CDATA[SiO 2 : 40%, Al 2 O 3 : 32%, CaO: 10%, ZrO 2 : 5%, B 2 O 3 : 6%, Na 2 O: 3%, K 2 O: 4%]]> G4 <![CDATA[SiO 2 : 50%, Al 2 O 3 : 20%, CaO: 10%, Bi 2 O 3 : 10%, B 2 O 3 : 5%, Na 2 O: 2%, K 2 O: 3%]]>

[0076] Table 3 Types and Contents of Organic Components

[0077]

[0078]

[0079] Table 4

[0080]

[0081]

[0082] Performance Detection

[0083] 1. Resistivity: The above-prepared organic silver paste is coated and sintered to obtain a silver wire, which is tested by an RTS-8 type four-probe instrument. The compliance requirement for the resistivity of the silver wire is: resistivity < 2·10 -8 Ω·m.

[0084] 2. Proportion of the longitudinal hole area: The organic silver paste is coated and sintered, and after sample preparation by an ion milling instrument, it is photographed and calculated under an electron microscope. The compliance requirement: the proportion of the longitudinal hole area < 4%.

[0085] 3. Viscosity: Tested at 25 °C using a Brookfield DV2T viscometer. Passing requirement: Viscosity at 10 rpm is 110 - 160 Pa·s.

[0086] 4. Thixotropy: Tested at 25 °C using a Brookfield DV2T viscometer. Passing requirement: Viscosity ratio of 10 rpm / 50 rpm (i.e., thixotropy index) is 1.5 - 3.5.

[0087] The above performance test results are shown in Table 5.

[0088] Table 5 Performance Test Results

[0089]

[0090]

[0091] As can be seen from Examples 1 - 17 in Table 5, in the present invention, by controlling the mass ratio of the organic binder, organic silver, and organic acid within the range defined by the present invention, the resistivity of the organic silver paste after sintering is small, showing good electrical conductivity. In Comparative Example 1, the ratio of organic silver to organic acid is on the high side, resulting in a relatively high viscosity and thixotropy of the silver paste. In Comparative Example 2, the ratio of organic silver to organic acid is on the low side. In Comparative Example 3, no organic silver, organic acid, and inorganic silver powder B are added, and the resistivity of the silver paste after sintering is high and there are many longitudinal holes.

[0092] Comparing Comparative Examples 4 - 5 with Example 1 respectively, in Comparative Example 4, there are too few hydrogen - bond - forming groups in the organic binder, and the hydrogen - bond interaction between the organic binder, organic acid, and organic silver is weak, which is not sufficient to ensure dispersion, thus affecting the electrical conductivity of the silver paste. In Comparative Example 5, there are too many hydrogen - bond - forming groups in the organic binder, and the viscosity and thixotropy of the slurry are on the high side, which is not conducive to printing. Therefore, by controlling the mass percentage of the hydrogen - bond - forming groups in the organic binder within the range of the present invention, it is beneficial to provide the electrical conductivity and printability of the slurry.

[0093] Comparing Comparative Example 6 with Example 1, if no additive is added to the organic silver paste, the adhesion and compactness of the printed organic silver paste are affected, and further affect the surface holes. Therefore, in the present invention, by compounding inorganic silver powder, organic silver, glass powder, organic carrier, organic acid, and additive, the organic silver paste has excellent electrical conductivity and printability.

[0094] Comparing Comparative Examples 7-8 with Example 1 respectively, it can be obtained that the contents of inorganic silver powder B and organic silver have important effects on the conductivity and the number of longitudinal holes of the paste. Therefore, by controlling the mass ratio of inorganic silver powder A, inorganic silver powder B and organic silver within the range of 1:(0.5-4):(0.5-4), the paste of the present invention can simultaneously have excellent conductivity and printability.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. An organic silver paste, characterized in that: The composition comprises the following components in parts by weight: 6-45 parts of inorganic silver powder; 5-30 parts of organic silver; 5-20 parts of glass powder; 10-30 parts of organic carrier; 8-32 parts of organic acid; 1-5 parts of additives; The organic carrier comprises an organic binder and a solvent, wherein the mass ratio of the organic binder, the organic silver and the organic acid is 1:(1-4):(1-6); the mass percentage of the groups capable of forming hydrogen bonds in the organic binder is 5-10%; The inorganic silver powder comprises inorganic silver powder A and inorganic silver powder B, and the mass ratio of the inorganic silver powder A, inorganic silver powder B and organic silver is 1:(0.5-4):(0.5-4).

2. The organic silver paste according to claim 1, characterized in that The group capable of forming a hydrogen bond includes any one or more of a hydroxyl group, an amino group, a carbonyl group, and a carboxyl group.

3. The organic silver paste according to claim 1, characterized in that The additive is at least one of zirconium oxide, copper oxide, nickel oxide and zinc oxide.

4. The organic silver paste according to claim 3, characterized in that: The additives include zirconium oxide, nickel oxide and zinc oxide, and the mass ratio of the zirconium oxide, nickel oxide and zinc oxide is 1:1:(0.5-2).

5. The organic silver paste according to claim 1, characterized in that The particle size range of the inorganic silver powder A is 0.5-3 μm, and the particle size range of the inorganic silver powder B is 200-500 nm.

6. The organic silver paste according to claim 1, characterized in that The mass ratio of the organic binder, organic silver and organic acid is 1:(1.6-3.5):(1.6-5), and / or the mass ratio of the inorganic silver powder A, inorganic silver powder B and organic silver is 1:(1-3.5):(1-3.5).

7. The organic silver paste according to claim 1, characterized in that: At least one of (a) to (d): (a) the organic silver is at least one of saturated fatty acid silver, silver citrate, silver oxalate, and silver benzoate, and the particle size of the organic silver is 1-10 μm; (b) the organic acid is at least one of saturated fatty acids, citric acid, oxalic acid, and benzoic acid; (c) the organic binder is at least one of ethyl cellulose, polymerized rosin, epoxy resin, polyurethane resin, and acrylic resin; (d) The solvent includes at least one of terpineol, butyl carbitol, butyl carbitol acetate, octanol, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, and propylene glycol monobutyl ether.

8. The organic silver paste according to claim 1, characterized in that: The glass powder is at least one of a Bi-Zn-B-Si system, a Bi-Ti-B-Si system, a Si-Ca-Al-Zr system, and a Si-Ca-Al-Bi system.

9. The method for preparing the organic silver paste according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1, mixing and dispersing inorganic silver powder B, organic silver, organic acid, and solvent to obtain a mixture 1; S2, mixing and dispersing inorganic silver powder A, glass powder, additives, organic binder and solvent to obtain mixture 2; S3, mixing and dispersing the mixture 1 and the mixture 2 to obtain an organic silver paste.

10. The use of the organic silver paste according to any one of claims 1 to 8 on electronic components, characterized in that: The following steps are involved: The organic silver paste as claimed in any one of claims 1 to 8 is printed on an electronic component substrate, and a conductive silver layer is obtained after drying and sintering.

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