Sintered silver paste, preparation method and application thereof

Abstract

This application provides a sintered silver paste, its preparation method, and its application, comprising: silver powder filler, sintering aid, and organic carrier. The silver powder filler has a mass fraction of 50-95%; the sintering aid has a mass fraction of 0.1-10%; and the organic carrier has a mass fraction of 3-35%, comprising at least one of organic solvent, organic resin, dispersant, rheology modifier, defoamer, thickener, or other additives. This application improves the sintering performance of micron-sized silver powder in the sintered silver paste system by adding a sintering aid, thereby reducing the use of nano-sized silver powder in the silver paste system. This solves the problems of easy cracking during sintering of nano-sized silver paste and poor sintering performance of micron-sized silver paste. It also simplifies the preparation process of the sintered silver paste and reduces its preparation cost, which is beneficial for the large-scale production and application of sintered silver paste.

Description

Technical Field

[0001] The present application relates to the technical field of electronic packaging materials, and in particular to a sintered silver paste, a preparation method thereof, and applications thereof. Background Art

[0002] With the rapid development of emerging semiconductor technologies, integrated circuits are moving towards a more miniaturized and highly integrated direction. Correspondingly, semiconductor power devices are required to work for a long time at high power density, high voltage, high operating temperature and high switching speed, which puts forward more stringent requirements on the heat dissipation capacity, reliability and electrical interconnection performance of semiconductor power devices. Under such conditions, wide bandgap (WBG) semiconductor power devices, represented by silicon carbide (SiC) and gallium nitride (GaN), have begun to emerge in large numbers. They have the characteristics of high blocking voltage, low on-state specific resistance and specific thermal resistance, low switching loss, high temperature resistance and radiation resistance, and still have very good conversion characteristics and working ability at an operating temperature of 250°C. However, in order to realize the connection between semiconductor components and substrates or heat sinks, alloy solders or conductive adhesives are often used as interconnection materials, but the reliable operating temperature of most alloy solders and conductive adhesives is far below 200°C. This seriously limits the application of wide bandgap semiconductor power devices. Therefore, it is very necessary to study new lead-free interconnection materials and interconnection technologies for high-power semiconductor devices that can serve under high temperature conditions.

[0003] In recent years, sintered silver paste that can provide excellent electrical conductivity, thermal conductivity and high temperature stability has attracted the attention of many researchers. The thermal conductivity of silver sintered solder paste is much higher than that of traditional tin-based solder, and the thickness of the sintered silver joint can be controlled at 10-30μm, which can effectively reduce the thermal resistance of the connection layer. Therefore, low-temperature sintered silver paste is considered to be one of the most promising chip bonding materials that can replace traditional tin-based solder. In the early stage, the metal filler in the sintered silver paste only contained micron-sized silver particles, so high pressure of up to 40 MPa was required to help it sinter, and this high pressure may cause mechanical damage to the mold and chip during the sintering process. In recent years, with the development of nanotechnology, nano-sintered silver paste with nano-silver powder as metal filler has attracted widespread attention. Compared with micron silver powder, the advantage of nano silver powder is that it has better sintering performance, but its preparation and separation and purification process is relatively complicated, resulting in its high preparation cost; at the same time, nano silver powder is easy to agglomerate during use, which seriously affects the actual performance of nano silver powder in the application process; in addition, nano silver powder shrinks greatly during the sintering process, which easily causes cracking of the sintered silver layer, thus causing serious reliability problems. Therefore, some researchers introduced an appropriate amount of nano silver powder into the micro silver paste formula to form a micro-nano composite sintered silver paste to improve the comprehensive performance of the sintered silver paste. The introduction of nano silver powder can effectively promote the sintering of micro silver powder, and micro silver powder can effectively inhibit the volume shrinkage of nano silver powder during the sintering process, thereby forming a high-quality sintered silver joint. However, in the micro-nano composite sintered silver paste, the introduction of nano silver powder only promotes the sintering of micro silver powder, but does not change or improve the sintering characteristics of the micro silver powder itself, and has limited effect on improving the sintering performance of the silver paste; at the same time, the introduction of nano silver powder also increases the complexity of the silver paste preparation process. Therefore, how to improve the sintering properties of micron silver powder itself and simplify the preparation process of sintered silver paste are key issues that need to be solved for the commercial application of sintered silver paste. Summary of the invention

[0004] Based on this, the present invention aims at the difficulties existing in the prior art and provides a sintered silver paste and a preparation method thereof and an application thereof, which can reduce the usage of nano silver powder in the silver paste system, simplify the preparation process of the sintered silver paste and reduce the cost of the silver paste, and facilitate the large-scale production and application of the silver paste. To achieve the above-mentioned purpose, the technical solution adopted in this application is as follows:

[0005] One of the purposes of the present application is to provide a sintered silver paste, comprising: a silver powder filler, a sintering aid and an organic carrier, wherein the mass fraction of the silver powder filler is 50-95%; the mass fraction of the sintering aid is 0.1-10%; the mass fraction of the organic carrier is 3-35%, and it includes at least one of an organic solvent, an organic resin, a dispersant, a rheological agent, a defoaming agent, a thickener or other additives.

[0006] In some of the embodiments, the silver powder filler can be a single-component silver powder or a multi-component silver-containing metal powder, wherein the remaining components of the silver-containing metal powder include but are not limited to at least one of metal components such as copper, gold, palladium, platinum, tin, bismuth, indium, nickel or aluminum.

[0007] In some of the embodiments, the silver powder filler contains more than 1% silver, preferably, the silver powder filler contains more than 20% silver, and more preferably, the silver content is 100%.

[0008] In some embodiments, the silver powder filler is a pure micron silver powder system or a micro-nano composite silver powder system, wherein the size of the micron silver powder in the silver powder system is 1-50 microns, and the size of the nano silver powder in the silver powder system is 1-1000 nanometers.

[0009] In some of the embodiments, the microstructure of the silver powder filler includes but is not limited to spherical, quasi-spherical, rod-shaped, linear, flake-shaped, hollow, core-shell, flower-shaped and other structures. Preferably, the microstructure of the silver powder filler is spherical or flake-shaped.

[0010] In some of the embodiments, the surface of the silver powder filler is coated with a surface ligand, and the surface ligand is an organic compound, and the organic compound includes but is not limited to an organic acid, an organic amine, and a polymer.

[0011] In some embodiments, the thermal decomposition temperature of the surface ligand is ≤250°C.

[0012] In some of the embodiments, the mass fraction of the silver powder filler is preferably 75-95%.

[0013] In some embodiments, the sintering aid includes an organic acid and an organic anhydride; the organic acid includes but is not limited to propionic acid, butyric acid or glutaric acid; the organic anhydride includes but is not limited to b-crotonic anhydride, butyric anhydride, isatoic anhydride, propionic anhydride, isobutyric anhydride, difluoroacetic anhydride, methanesulfonic anhydride, 1,2,4-benzene trimellitic anhydride, bromomaleic anhydride, itaconic anhydride, 2,3-dimethylmaleic anhydride, 2-methylsuccinic anhydride, trifluoroacetic anhydride, pentafluoropropionic anhydride, acrylic anhydride, (-)-O-acetyl-L-malic anhydride, cis-aconitic anhydride, acetic propionic anhydride; the sintering aid is at least one of an organic acid and an organic anhydride.

[0014] In some embodiments, the mass fraction of the sintering aid is preferably 0.1-5%.

[0015] In some embodiments, the mass fraction of the organic carrier is preferably 3-10%.

[0016] In some embodiments, the organic carrier includes at least one of an organic solvent, an organic resin, a dispersant, a rheological agent, a defoaming agent, a thickener or other additives.

[0017] In some embodiments, the organic solvent includes but is not limited to at least one of butyl carbitol, butyl carbitol acetate, tripropylene glycol, dipropylene glycol butyl ether, dipropylene glycol methyl ether, triethylene glycol butyl ether, triethylene glycol methyl ether, propylene glycol butyl ether, diethylene glycol, ethylene glycol, polyethylene glycol, terpineol and the like;

[0018] The organic resin includes but is not limited to at least one of epoxy resin, phenoxy resin, acrylic resin, silicone resin or polyimide resin.

[0019] The second purpose of the present application is to provide a method for preparing a sintered silver paste, comprising the following steps: uniformly mixing a silver powder filler, a sintering aid and an organic carrier with a mass fraction of 50-95%: 0.1-10%: 3-35% to obtain the sintered silver paste.

[0020] The third purpose of the present application is to provide an application of the sintered silver paste in the field of electronic packaging.

[0021] This application adopts the above technical solution, and its beneficial effects are as follows:

[0022] The sintered silver paste and preparation method provided by the present application include: silver powder filler, sintering aid and organic carrier, wherein the mass fraction of the silver powder filler is 50-95%; the mass fraction of the sintering aid is 0.1-10%; the mass fraction of the organic carrier is 3-35%, which includes at least one of organic solvent, organic resin, dispersant, rheological agent, defoamer, thickener or other additives. The present application effectively improves the sintering performance of micron silver powder in the silver paste by introducing a suitable silver powder sintering aid into the sintered silver paste, thereby reducing the use of nano silver powder in the silver paste system, solving the problem of easy cracking of nano silver paste during sintering and poor sintering performance of micro silver paste, and also simplifies the preparation process of the sintered silver paste and reduces the preparation cost of the sintered silver paste, which is conducive to the large-scale production and application of the sintered silver paste. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 This is an optical photograph of the silver paste provided in Example 1 of the present application.

[0025] Figure 2 This is an electron microscope image of the cross section of the sintered silver joint provided in Example 2 of the present application.

[0026] Figure 3 Schematic diagram of the sandwich-shaped packaging structure provided for Examples 1-7 of the present application. DETAILED DESCRIPTION

[0027] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0028] In the description of the present application, it should be understood that the terms "upper", "lower", "horizontal", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0029] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0030] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0031] The present application provides a sintered silver paste, comprising: a silver powder filler, a sintering aid and an organic carrier, wherein the mass fraction of the silver powder filler is 50-95%; the mass fraction of the sintering aid is 0.1-10%; the mass fraction of the organic carrier is 3-35%, and it includes at least one of an organic solvent, an organic resin, a dispersant, a rheological agent, a defoamer, a thickener or other additives. The specific components of each species component are described in detail below.

[0032] In this embodiment, the silver powder filler can be a single-component silver powder or a multi-component silver-containing metal powder, wherein the remaining components of the silver-containing metal powder include but are not limited to at least one of the metal components such as copper, gold, palladium, platinum, tin, bismuth, indium, nickel, and aluminum.

[0033] In this embodiment, the silver content of the silver powder filler is greater than 1%, preferably, the silver content of the silver powder filler is greater than 20%, and more preferably, the silver content is 100%, so that the silver powder filler exhibits better anti-oxidation performance and sintering performance.

[0034] In this embodiment, the silver powder filler is a pure micron silver powder system or a micro-nano composite silver powder system, wherein the size of the micron silver powder in the silver powder system is 1-50 microns, and the size of the nano silver powder in the silver powder system is 1-1000 nanometers.

[0035] In this embodiment, the microstructure of the silver powder filler includes but is not limited to spherical, quasi-spherical, rod-shaped, linear, flake-shaped, hollow, core-shell, flower-shaped and other structures. Preferably, the microstructure of the silver powder filler is spherical or flake-shaped, which is conducive to the dense stacking and sintering of the silver powder.

[0036] In this embodiment, the surface of the silver powder filler is coated with a surface ligand, and the surface ligand is an organic compound, which includes but is not limited to organic acids, organic amines, polymers, etc., such as polyvinyl pyrrole, polyvinyl alcohol, oleic acid, oleylamine, etc.

[0037] In this embodiment, the thermal decomposition temperature of the surface ligand is ≤250° C., which is beneficial to the low-temperature sintering of the silver powder.

[0038] In this embodiment, the mass fraction of the silver powder filler is preferably 75-95%, and a high solid content is conducive to forming a dense sintered body.

[0039] In this embodiment, the sintering aid includes an organic acid and an organic anhydride; the organic acid includes but is not limited to propionic acid, butyric acid or glutaric acid; the organic anhydride includes but is not limited to b-crotonic anhydride, butyric anhydride, isatoic anhydride, propionic anhydride, isobutyric anhydride, difluoroacetic anhydride, methanesulfonic anhydride, 1,2,4-benzene trimellitic anhydride, bromomaleic anhydride, itaconic anhydride, 2,3-dimethylmaleic anhydride, 2-methylsuccinic anhydride, trifluoroacetic anhydride, pentafluoropropionic anhydride, acrylic anhydride, (-)-O-acetyl-L-malic anhydride, cis-aconitic anhydride, acetic propionic anhydride; the sintering aid is at least one of an organic acid and an organic anhydride.

[0040] In this embodiment, the mass fraction of the sintering aid is preferably 0.1-5%, which is beneficial to the low-temperature sintering performance of the silver powder.

[0041] It can be understood that the present application introduces organic acid or organic anhydride as a sintering aid, which can effectively activate the surface of the micron silver powder during the sintering process, thereby improving the sintering characteristics of the micron silver powder, making it exhibit sintering performance similar to that of nano silver powder, reducing the amount of nano silver powder used in the silver paste system, simplifying the silver paste preparation process and reducing the preparation cost of the silver paste.

[0042] In this embodiment, the mass fraction of the organic carrier is preferably 3-10% to obtain good rheological properties.

[0043] In this embodiment, the organic carrier includes at least one of an organic solvent, an organic resin, a dispersant, a rheological agent, a defoaming agent, a thickener or other auxiliary agents.

[0044] In this embodiment, the organic solvent includes but is not limited to at least one of butyl carbitol, butyl carbitol acetate, tripropylene glycol, dipropylene glycol butyl ether, dipropylene glycol methyl ether, triethylene glycol butyl ether, triethylene glycol methyl ether, propylene glycol butyl ether, diethylene glycol, ethylene glycol, polyethylene glycol, terpineol and the like;

[0045] The organic resin includes but is not limited to at least one of epoxy resin, phenoxy resin, acrylic resin, silicone resin or polyimide resin.

[0046] The sintered silver paste provided in the above-mentioned embodiments of the present application adds a sintering aid to the sintered silver paste, thereby improving the sintering performance of the micron silver powder in the silver paste system, thereby reducing the use of nano silver powder in the silver paste system, solving the problems of easy cracking of nano silver paste during sintering and poor sintering performance of micron silver paste, and also simplifies the preparation process of the sintered silver paste and reduces the preparation cost of the silver paste, which is conducive to the large-scale production and application of the silver paste.

[0047] The present application also provides a method for preparing a sintered silver paste, comprising the following steps: uniformly mixing a silver powder filler, a sintering aid and an organic carrier with mass fractions of 50-95%: 0.1-10%: 3-35% to obtain the sintered silver paste.

[0048] The preparation method of the sintered silver paste provided in the above embodiment of the present application adds a sintering aid to the sintered silver paste, improves the sintering performance of the micron silver powder in the silver paste system, thereby reducing the use of nano silver powder in the silver paste system, solving the problem of easy cracking of nano silver paste during sintering and poor sintering performance of micron silver paste, and also simplifies the preparation process of the sintered silver paste and reduces the preparation cost of the silver paste, which is conducive to the large-scale production and application of the silver paste. The sintered silver paste obtained by the preparation method provided by the present invention has good performance, and can form a high-strength sintered silver solder joint with high reliability after sintering; the sintering process of the present invention is conducive to improving the production efficiency of the equipment and reducing the investment cost and energy consumption cost of the process equipment.

[0049] The sintered silver paste provided in the above embodiments of the present application can be applied to the field of electronic device packaging.

[0050] Embodiment 1:

[0051] (1) Preparation method:

[0052] 0.01 g of acetic propionic anhydride was dissolved in 0.14 g of a mixed solution prepared by terpineol and ethylene glycol in a mass ratio of 1:1, and the mixture was fully mixed to obtain an organic carrier mixed solution;

[0053] Weigh 0.85 g of flaky silver powder and mix it with the organic carrier mixed solution in a high-speed mixer. The size of the silver powder is 1-5 μm and the thickness is 100-300 nm.

[0054] The optical photograph of the silver paste prepared in this example is as follows Figure 1 As shown, it can be seen that the silver paste obtained by this method has better dispersibility, good rheological properties, and no agglomeration phenomenon.

[0055] (2) Shear strength performance evaluation method:

[0056] Sample preparation: Sandwich-like packaging structures such as Figure 3 As shown, the silver paste prepared in this embodiment is evenly coated on a 5.8mm*5.8mm gold-plated DBC lower substrate, and then a 3.0mm*3.0mm gold-plated DBC upper substrate is stacked on the surface coated with the silver paste, and a pressure of 0.2N is applied to make the upper and lower DBC substrates fully contact with the silver paste layer coated in the middle, and hot-pressed and sintered at 250°C and a pressure of 10MPa for 10min to obtain a sandwich packaging structure of sintered DBC / silver sintered layer / DBC.

[0057] Performance test: Dage-4000 was used to test the shear strength. Five sintered samples were tested in parallel, and the average shear strength was 55.4 MPa.

[0058] Embodiment 2:

[0059] (1) Preparation method:

[0060] 0.01 g of acrylic anhydride was dissolved in a mixed solution of 0.14 g of pineol and butyl carbitol prepared in a mass ratio of 1:1, and the mixture was thoroughly mixed to obtain an organic carrier mixed solution;

[0061] Weigh 0.85 g of flaky silver powder and mix it with the organic carrier mixed solution in a high-speed mixer. The size of the silver powder is 1-5 μm and the thickness is 100-300 nm.

[0062] The silver paste obtained by this method has good dispersibility, good rheological properties, and no agglomeration phenomenon.

[0063] (2) Shear strength performance evaluation method:

[0064] Sample preparation: Sandwich-shaped packaging structure such as Figure 3As shown, the silver paste prepared in this embodiment is evenly coated on a 5.8mm*5.8mm gold-plated DBC lower substrate, and then a 3.0mm*3.0mm gold-plated DBC upper substrate is stacked on the surface coated with the silver paste, and a pressure of 0.2N is applied to make the upper and lower DBC substrates fully contact with the silver paste layer coated in the middle, and hot-pressed and sintered at 250°C and a pressure of 10MPa for 10min to obtain a sandwich packaging structure of sintered DBC / silver sintered layer / DBC.

[0065] Performance test: Dage-4000 was used to test the shear strength of 5 sintered samples in parallel. The average shear strength was 48.6 MPa. Figure 2 As shown, its cross section shows good ductile fracture.

[0066] Embodiment 3:

[0067] (1) Preparation method:

[0068] Dissolve 0.005 g of acetic propionic anhydride in a mixed solution prepared by 0.145 g of terpineol and diethylene glycol in a mass ratio of 1:1, and mix thoroughly to obtain an organic carrier mixed solution;

[0069] Weigh 0.85 g of flaky silver powder and mix it with the organic carrier mixed solution in a high-speed mixer. The size of the silver powder is 1-5 μm and the thickness is 100-300 nm.

[0070] The silver paste obtained by this method has good dispersibility, good rheological properties, and no agglomeration phenomenon.

[0071] (2) Shear strength performance evaluation method:

[0072] Sample preparation: Sandwich-shaped packaging structure such as Figure 3 As shown, the silver paste prepared in this embodiment is evenly coated on a 5.8mm*5.8mm gold-plated DBC lower substrate, and then a 3.0mm*3.0mm gold-plated DBC upper substrate is stacked on the surface coated with the silver paste, and a pressure of 0.2N is applied to make the upper and lower DBC substrates fully contact with the silver paste layer coated in the middle, and hot-pressed and sintered at 250°C and a pressure of 10MPa for 10min to obtain a sandwich packaging structure of sintered DBC / silver sintered layer / DBC.

[0073] Performance test: Dage-4000 was used to test the shear strength. Five sintered samples were tested in parallel, and the average shear strength was 58.9 MPa.

[0074] Embodiment 4:

[0075] (1) Preparation method:

[0076] 0.02 g of acetic propionic anhydride was dissolved in a mixed solution prepared by 0.13 g of butyl carbitol and diethylene glycol in a mass ratio of 1:1, and the mixture was thoroughly mixed to obtain an organic carrier mixed solution;

[0077] Weigh 0.85 g of flaky silver powder and mix it with the organic carrier mixed solution in a high-speed mixer. The size of the silver powder is 1-5 μm and the thickness is 100-300 nm.

[0078] The silver paste obtained by this method has good dispersibility, good rheological properties, and no agglomeration phenomenon.

[0079] (2) Shear strength performance evaluation method:

[0080] Sample preparation: Sandwich-shaped packaging structure such as Figure 3 As shown, the silver paste prepared in this embodiment is evenly coated on a 5.8mm*5.8mm gold-plated DBC lower substrate, and then a 3.0mm*3.0mm gold-plated DBC upper substrate is stacked on the surface coated with the silver paste, and a pressure of 0.2N is applied to make the upper and lower DBC substrates fully contact with the silver paste layer coated in the middle, and hot-pressed and sintered at 250°C and a pressure of 10MPa for 10min to obtain a sandwich packaging structure of sintered DBC / silver sintered layer / DBC.

[0081] Performance test: Dage-4000 was used to test the shear strength. Five sintered samples were tested in parallel, and the average shear strength was 43.5 MPa.

[0082] Embodiment 5:

[0083] (1) Preparation method:

[0084] 0.03 g of acetic propionic anhydride was dissolved in a mixed solution prepared by 0.12 g of butyl carbitol acetate and diethylene glycol in a mass ratio of 1:1, and the mixture was fully mixed to obtain an organic carrier mixed solution;

[0085] Weigh 0.85 g of flaky silver powder and mix it with the organic carrier mixed solution in a high-speed mixer. The size of the silver powder is 1-5 μm and the thickness is 100-300 nm.

[0086] The silver paste obtained by this method has good dispersibility, good rheological properties, and no agglomeration phenomenon.

[0087] (2) Shear strength performance evaluation method:

[0088] Sample preparation: Sandwich-shaped packaging structure such as Figure 3As shown, the silver paste prepared in this embodiment is evenly coated on a 5.8mm*5.8mm gold-plated DBC lower substrate, and then a 3.0mm*3.0mm gold-plated DBC upper substrate is stacked on the surface coated with the silver paste, and a pressure of 0.2N is applied to make the upper and lower DBC substrates fully contact with the silver paste layer coated in the middle, and hot-pressed and sintered at 250°C and a pressure of 10MPa for 10min to obtain a sandwich packaging structure of sintered DBC / silver sintered layer / DBC.

[0089] Performance test: Dage-4000 was used to test the shear strength. Five sintered samples were tested in parallel, and the average shear strength was 43.5 MPa.

[0090] Embodiment 6:

[0091] (1) Preparation method:

[0092] 0.005 g of acetic propionic anhydride was dissolved in a mixed solution of 0.145 g of terpineol and ethylene glycol in a mass ratio of 1:1, and the mixture was thoroughly mixed to obtain an organic carrier mixed solution;

[0093] Weigh 0.30 g of spherical nano silver powder with a size of 100 nanometers and 0.55 g of flaky silver powder and mix them with the organic carrier mixed solution in a high-speed mixer. The flaky silver powder has a size of 1-5 μm and a thickness of 100-300 nm.

[0094] The silver paste obtained by this method has good dispersibility, good rheological properties, and no agglomeration phenomenon.

[0095] (2) Shear strength performance evaluation method:

[0096] Sample preparation: Sandwich-shaped packaging structure such as Figure 3 As shown, the silver paste prepared in this embodiment is evenly coated on a 5.8mm*5.8mm gold-plated DBC lower substrate, and then a 3.0mm*3.0mm gold-plated DBC upper substrate is stacked on the surface coated with the silver paste, and a pressure of 0.2N is applied to make the upper and lower DBC substrates fully contact with the silver paste layer coated in the middle, and pressureless sintering is performed at 250°C for 90min to obtain a sandwich packaging structure of sintered DBC / silver sintering layer / DBC.

[0097] Performance test: Dage-4000 was used to test the shear strength. Five sintered samples were tested in parallel, and the average shear strength was 63.2 MPa.

[0098] Embodiment 7:

[0099] (1) Preparation method:

[0100] Dissolve 0.005 g of acetic propionic anhydride and 0.05 g of bisphenol A epoxy resin curing system in 0.095 g of diethylene glycol butyl ether acetate, mix well, and obtain an organic carrier mixed solution;

[0101] Weigh 0.85 g of flaky silver powder and mix it with the organic carrier mixed solution in a high-speed mixer. The size of the flaky silver powder is 1-5 μm and the thickness is 100-300 nm.

[0102] The silver paste obtained by this method has good dispersibility, good rheological properties, and no agglomeration phenomenon.

[0103] (2) Shear strength performance evaluation method:

[0104] Sample preparation: Sandwich-shaped packaging structure such as Figure 3 As shown, the silver paste prepared in this embodiment is evenly coated on a 5.8mm*5.8mm gold-plated DBC lower substrate, and then a 3.0mm*3.0mm gold-plated DBC upper substrate is stacked on the surface coated with the silver paste, and a pressure of 0.2N is applied to make the upper and lower DBC substrates fully contact with the silver paste layer coated in the middle, and pressureless sintering is performed at 250°C for 90min to obtain a sandwich packaging structure of sintered DBC / silver sintering layer / DBC.

[0105] Performance test: Dage-4000 was used to test the shear strength. Five sintered samples were tested in parallel, and the average shear strength was 32.6 MPa.

[0106] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0107] The above are only preferred embodiments of the present application, and only specifically describe the technical principles of the present application. These descriptions are only for explaining the principles of the present application and cannot be interpreted as limiting the scope of protection of the present application in any way. Based on the explanation here, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application, and other specific implementation methods of the present application that can be associated with the technicians in this field without creative work, should be included in the scope of protection of the present application.

Claims

1. A sintered silver paste, characterized in that: include: Silver powder filler, sintering aid and organic carrier, the mass fraction of the silver powder filler is 85%; the mass fraction of the sintering aid is 1%; the mass fraction of the organic carrier is 14%; The silver powder filler is flaky silver powder with a size of 1-5 μm and a thickness of 100-300 nm; The sintering aid is acetic propionic anhydride; The organic carrier is prepared by mixing terpineol and ethylene glycol in a mass ratio of 1:1; Or, the sintered silver paste comprises: a silver powder filler, a sintering aid and an organic carrier, wherein the mass fraction of the silver powder filler is 85%; the mass fraction of the sintering aid is 0.5%; and the mass fraction of the organic carrier is 14.5%; The silver powder filler is flaky silver powder with a size of 1-5 μm and a thickness of 100-300 nm; The sintering aid is acetic propionic anhydride; The organic carrier is prepared by mixing terpineol and diethylene glycol in a mass ratio of 1:

1.

2. The sintered silver paste according to claim 1, characterized in that: The surface of the silver powder filler is coated with a surface ligand, and the surface ligand is an organic compound, which includes an organic acid, an organic amine, and a polymer.

3. The sintered silver paste according to claim 2, characterized in that: The thermal decomposition temperature of the surface ligand is ≤250°C.

4. A method for preparing a sintered silver paste as claimed in any one of claims 1 to 3, characterized in that: The method comprises the following steps: uniformly mixing silver powder filler, sintering aid and organic carrier to obtain the sintered silver paste.

5. Use of the sintered silver paste according to any one of claims 1 to 4 in the field of electronic packaging.

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