Glass powder for MLCC, conductive copper paste and preparation method thereof

Abstract

The application discloses a glass powder for MLCC, conductive copper paste and a preparation method thereof. The glass powder formula is 18.0-28.0% SiO2, 25.0-35.0% B2O3, 30.0-45.0% BaO, 0-10% CaO, 0-5% Na2O, 0-8.0% TiO2, 0-6% CuO, 0-5.0% Sb2O3 and 0-5.0% NaF. The basic component of the glass powder does not contain Bi and Zn, the system is SiO2-B2O3-Na2O-BaO, TiO2, CuO, Sb2O3 and NaF are added in the basic glass component, Sb2O3 can reduce the surface tension of the glass, improve the wettability between the glass and copper powder and ceramics, TiO2 and CuO can enhance the acid resistance of the glass and increase the compactness at the interface. NaF can accelerate the glass liquid clarification speed, reduce the high-temperature viscosity of the glass powder, enhance the flowability of the glass powder and improve the interface compactness speed. The average particle size of the glass powder is between 1.8-2.5 microns, and the thermal expansion coefficient of the glass is between 6.5-9.5 ppm / ℃. The glass powder has obvious sintering effect on the copper paste, after the copper paste is applied to the MLCC ceramic substrate and sintered, the copper paste and the ceramic substrate have firm physical and chemical bonding, the MLCC has excellent electrical performance, adhesion and good resistance to electroplating solution.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electronic components, and particularly relates to a glass powder for MLCC, a conductive copper paste and a preparation method thereof. BACKGROUND

[0002] In recent years, with the rapid development of the electronic information industry, electronic components develop towards high reliability, miniaturization, integration and low cost, and the performance requirements for materials are also increasing year by year.

[0003] Compared with noble metal paste, the conductive copper paste is low in price, and has close conductivity, ductility and solderability of paste to noble metal paste, and is widely used in electronic industries such as MLCC and LTCC. However, the copper paste still has problems such as poor adhesion, easy electrode peeling and poor resistance to plating liquid corrosion. As a key component of the copper paste, the glass powder plays an important role in the adhesion of the copper paste, sintering density and the like. The copper paste glass powder is developing towards lead-free and non-toxic, and US2014 / 0363681A1 discloses a thick layer printed copper conductive paste suitable for an aluminum nitride (AlN) substrate. The glass powder used in the copper paste is 45-65% Bi2O3, 25-45% SiO2 and 1-15% B2O3. When applied to the aluminum nitride substrate, the thermal expansion coefficient is well matched, and excellent adhesion is shown. However, the bismuth salt glass melt is prone to phase separation and poor in acid resistance and plating liquid resistance, which easily affects the long-term reliability of the product. CN116535097A discloses a zinc-boron-silicon glass system basic component and additional components CuO, TiO2 and ZrO2 for a multilayer ceramic capacitor (MLCC), and the mass ratio is 100:(0.5-1.5):(0.5-1.5):(0.5-1.5). The glass powder of the application has a low softening point, which helps the copper paste to sinter at a low temperature, improves the electrode resistance to plating liquid, and has good wetting at high temperature, thereby enhancing the adhesion of the copper paste. However, when the glass powder is co-fired, ZnB2O4 crystals are easily precipitated, the stress at the interface of the substrate is increased, and the wetting of the glass powder is reduced, thereby reducing the reliability of the product.

[0004] Therefore, it is necessary to design a Zn-free, Bi-free and lead-free glass. The glass powder applied in the copper paste should have good resistance to plating liquid, not produce stress-increasing products with the ceramic substrate, have high thermal expansion matching with the ceramic substrate and copper powder, and have obvious sintering effect on the copper paste. In addition, the copper paste components can be optimized to solve the problem of stress caused by large temperature gradient change during sintering and cooling of the copper paste. SUMMARY

[0005] In view of the problems in the background art, the present application provides a glass powder for MLCC, a conductive copper paste and a preparation method thereof, which solves the problems of easy crystallization, phase separation and high-temperature evaporation in the glass powder of the prior art, reduces the stress caused by the crystal growth or transformation of interface products, improves the wettability and thermal expansion matching of the glass powder to copper powder and ceramic substrate, thereby enhancing the plating liquid resistance and conductivity of the copper paste. Meanwhile, the stress problem caused by the excessive cooling gradient of MLCC at the interface of MLCC copper paste is solved by optimizing the copper paste formula.

[0006] To achieve the above-mentioned object, the technical scheme adopted by the present application is as follows:

[0007] In the first aspect, the present application provides a Zn-free, Bi-free and lead-free glass powder: 18.0-28.0% SiO2, 25.0-35.0% B2O3, 30.0-45.0% BaO, 0-10% CaO, 0-5% Na2O, 0-8.0% TiO2, 0-6% CuO, 0-5.0% Sb2O3, and 0-5.0% NaF. The glass-forming body SiO2 and B2O3 serve as the skeleton of the glass powder. The addition of excess alkali (Na2O) and alkaline earth metal (CaO, BaO) reduces the glass melting temperature and high-temperature viscosity, and promotes the formation of a more compact structure [BO4] of B. - TiO2, CuO and Sb2O3 can reduce the surface tension of the glass, enhance the acid resistance of the glass, and increase the density at the interface. NaF acts as a glass liquid clarifier, which can accelerate the glass liquid clarification speed and reduce the high-temperature viscosity of the glass powder.

[0008] As a preferred scheme of the first aspect of the present application, the composition of the glass is preferably 24.0-26.0% SiO2, 25.0-29.0% B2O3, 30.0-40.0% BaO, 2-7% CaO, 0-5% Na2O, 0-4.0% TiO2, 0-5% CuO, 0-5.0% Sb2O3, and 0-5.0% NaF. Among them, (Sb2O3+NaF)≥2.0%, and (Na2O+CaO+BaO)≥40%. The glass in this element range has good glass-forming properties, good sintering activity, good acid resistance, and good adhesion to the substrate.

[0009] In the second aspect, the present application provides a conductive paste for MLCC, which is prepared by mixing 65.0-80.0% copper powder, 7.0-15.0% glass powder, 15.0-23.0% organic carrier, and 0-5.0% inorganic powder additive, calculated by mass percentage. The inorganic powder additive is selected from a powder with extremely small or negative expansion coefficient, such as a lithium feldspar powder, to solve the stress problem caused by the excessive cooling gradient of MLCC at the interface of MLCC copper paste.

[0010] As a preferred scheme of the second aspect of the present application, the solid content (glass powder + copper powder) of the slurry is ≥80%, so as to increase the dry film density of the slurry and increase the edge thickness of the end electrode of the MLCC.

[0011] As a preferred scheme of the second aspect of the present application, the organic carrier comprises 70-80% of solvent and 20-30% of resin in terms of mass percentage. The preferred solvent comprises two of diethylene glycol butyl ether acetate, dipropylene glycol butyl ether and terpineol; the resin is preferably acrylic resin, and the molecular weight is 25W-50W.

[0012] In a third aspect, the present application further discloses a preparation method of the conductive copper paste, comprising the following steps:

[0013] S1, weigh the solvent and the resin, and dissolve the resin in the solvent uniformly at 80-90°C, and fully stir to form a uniform organic carrier.

[0014] S2, weigh the glass powder, the copper powder, the organic carrier prepared in step S21 and the inorganic powder additive according to the proportion, and stir sequentially using a high-speed homogenizer to form a uniform slurry. Then, the slurry is fully ground using a three-roll mill to finally prepare the copper conductive paste meeting the performance requirements.

[0015] Further, in the step S2, the preparation of the glass powder comprises the following steps:

[0016] S21, put the glass raw material into a platinum crucible after fully mixing and grinding, and melt at 1200°C for 60 min. Then, pour the molten glass liquid into deionized water for quenching, so as to break the glass into particles.

[0017] S22, coarsely grind and finely ball mill the glass powder prepared in step S21 by using a ball milling process, so that the particle size D50 of the ball-milled glass powder is reduced to 2-3μm.

[0018] As a preferred scheme of the third aspect of the present application, the carrier A and the carrier B prepared in step S1 are both filtered through a 200-400 mesh filter screen, the slurry prepared in step S2 is filtered through a 200-300 mesh filter screen, the coarsely ground glass powder is filtered through a 100-200 mesh screen, and the finely ground and dried glass powder is filtered through a 200-400 mesh screen.

[0019] As described above, the copper conductive paste is attached to the end surface of the MLCC with a size of 0402 or above, and then dried and sintered in sequence to obtain a copper electrode. The drying temperature is 120-130°C, and the time is 10-20 min; the sintering process is as follows: first, heat to 500°C at a heating rate of 20-50°C / min under a wet nitrogen atmosphere, and then heat to 650-750°C at a heating rate of 30-50°C / min under a dry nitrogen atmosphere, and keep for 10 min.

[0020] The application as described above, the copper terminal electrode is composed of copper film and substrate, the end surface is free of bulge, free of cracking, free of glass overflow, the average square resistance of the copper film is 4.5-15.3 mΩ / square, and the tension of the terminal electrode is 10-15 LB.

[0021] Invention principle: the glass powder added in the conductive paste for LTCC can help to reduce the wetting angle of copper powder and MLCC substrate, improve the acid resistance after sintering of the paste, and control the thermal expansion coefficient of the copper paste. At the same time, the liquefaction temperature of the copper powder can be effectively reduced, the densification process of the paste in the sintering process is promoted, the sintering time is reduced, and the energy consumption is reduced. First, Sb2O3 in the glass powder can reduce the surface tension of the glass, increase the acid resistance of the glass, and increase the density at the interface. NaF and Si form Si-O-Na non-bridge oxygen connection and SiF, which can reduce the viscosity of the glass powder while clarifying the glass liquid, and can accelerate the clarification speed of the glass liquid and reduce the high-temperature viscosity of the glass powder. Secondly, the glass powder is free of Bi, Zn, Pb and other components that are easy to crystallize, phase separate and volatile at high temperature. The addition of TiO2 and CuO can improve the wettability of the glass powder to copper powder and ceramic substrate and the thermal expansion matching, form a Cu-glass powder-Cu-nickel and Cu-glass-substrate connection interface, thereby enhancing the resistance of the copper paste to the electroplating solution and the conductivity of the copper paste, and improving the terminal tension of the MLCC.

[0022] The inorganic powder additive can inhibit the shrinkage of copper powder during sintering, and can effectively avoid the warping and cracking of the MLCC substrate caused by different shrinkage starting temperatures during the sintering process of the copper paste and the MLCC substrate. The specific principle is that the micro essence of the shrinkage of copper powder during sintering is that the centers of two particles approach and fuse into a large particle, and the inorganic powder blocks the contact between the two particles, and the grain growth process is slowed down. In addition, the inorganic powder additive can soften to form a liquid phase, wet the copper powder and the MLCC substrate, so that the copper film and the LTCC substrate after sintering have good bonding force.

[0023] The copper paste prepared in the application can be sintered with the MLCC substrate to form a dense terminal electrode and has strong bonding force with the MLCC substrate. The MLCC device prepared by the application has the advantages of high sintering densification degree and high electroplating qualification rate. After sintering, the internal stress distribution of the chip device is uniform and moderate, the square resistance is small, the solder resistance is strong, and the reliability test qualification rate of heating aging, accelerated life and the like is high.

[0024] Compared with the prior art, the gain effect of the application includes:

[0025] The glass powder prepared by the application is non-toxic, environmentally friendly, and has excellent chemical stability and thermal stability, high matching degree of the thermal expansion coefficient of the glass, good wettability between the glass and the copper powder, and obvious sintering effect of the glass powder. The conductive copper paste formed by mixing the glass powder, the copper powder, the organic carrier and the inorganic powder has good comprehensive performance, high sintering densification degree, low porosity and good conductivity. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 (a)-(i) are SEM images of the end faces of Examples 1-6 and Comparative Examples 1-3 of the application.

[0027] Figure 2 (a)-(f) are SEM images of the cross sections of Examples 1-4 and Comparative Examples 2-3 of the application. DETAILED DESCRIPTION

[0028] In order to more clearly illustrate the purpose, technical scheme and advantages of the application, the application will be further described below in combination with specific examples. The described examples are only a part of the examples of the application, rather than all the examples. Based on the examples in the application, other examples obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0029] The application will be described below in combination with specific examples.

[0030] Example 1

[0031] The slurry described in this example contains 75% copper powder, 8% glass powder, 16% organic carrier and 1% micron-sized lepidolite powder by mass percentage.

[0032] The organic carrier described in this example contains carrier A and carrier B. Carrier A contains the following components by weight percentage: 50% terpineol, 10% diethylene glycol butyl ether acetate and 30% acrylic resin. Carrier B contains 40% diethylene glycol butyl ether acetate and 20% acrylic resin. The mass ratio of carrier A to carrier B is 3:2.

[0033] The copper powder described in this example contains D50=5μm spherical copper powder and D50=1.5μm hexagonal copper powder, and the mass ratio of the two is 1:2.

[0034] The glass powder described in this example contains the following components by weight percentage: 26.0% SiO2, 25.0% B2O3, 30.0% BaO, 7.0% CaO, 5.0% Na2O, 2.0% TiO2, 2.0% CuO, 1.0% Sb2O3 and 2.0% NaF.

[0035] The preparation method of the end electrode copper paste comprises the following steps:

[0036] S1, the solvent and the resin are weighed, and the resin is uniformly dissolved in the solvent at 80-90°C. The uniform organic carrier is formed by sufficient stirring.

[0037] S2, the organic carrier A prepared in step S1, the carrier B, the glass powder, the copper powder A and the copper powder B are weighed and stirred uniformly to form a slurry. Then the slurry is sufficiently ground by a three-roll mill to finally prepare a copper paste slurry meeting the performance requirements.

[0038] The preparation method of the glass comprises the following steps:

[0039] S1, the glass raw materials are weighed, mixed and ground, and then put into a platinum crucible. The melting is carried out at 1300°C for 1.5h.

[0040] S2, the molten glass liquid is poured into deionized water for quenching, and a ball mill is used for crushing to reduce the particle size D50 of the particles to 2μm, so as to obtain the glass powder.

[0041] The use and test method of the copper paste

[0042] The prepared copper paste is formed on the MLCC end substrate by dip coating to form a 50-60μm thick paste. The drying temperature is 120-130°C, and the time is 10-20min; then in a wet nitrogen atmosphere, the temperature is raised to 500°C at a rate of 20-50°C / min, and then kept for 10min, and then in a dry nitrogen atmosphere, the temperature is raised to 650-750°C at a rate of 30-50°C / min, and then kept for 10min.

[0043] The acid and alkali resistance test conditions of the glass powder are 55°C, the soaking time is 60min, the pH of the acid solution is 2, the pH of the alkali solution is 10, and the mass change before and after soaking in the acid and alkali solutions is compared after cleaning and drying.

[0044] The viscosity testing instrument, rotor model and test conditions of the copper paste are: Brookfield@Spindle No.SC-14 / 6R at 25°C, and the viscosity change at 10rpm is detected.

[0045] The electrical properties of the copper film are measured by a four-probe resistance meter. In the present application, the square resistance represents the resistance between the opposite two sides of a square thin film conductive material.

[0046] The film thickness and the edge film thickness are tested by the DPA analysis method under the condition of SEM@500 times.

[0047] The bonding strength between the end electrode and the ceramic substrate is represented by the tensile force. First, the end paste is sealed on the 0805 MLCC, and sintered according to the copper end paste sintering process. After the end electrode is sintered, the copper film is tinned and nickel-plated, and then a tin wire is welded for tensile force testing.

[0048] The acid and alkali resistance results, hemispherical temperature and transition temperature of the glass powder in this embodiment are shown in Table 1. The weight loss rate of the glass powder in Example 1 is less than 0.2% under acid and alkali resistance. The viscosity change of the copper paste in Example 1 stored for one month is shown in Table 2, and the change rate is less than 5%. The bonding layer with the MLCC end surface is Figure 1 , the porosity of the interface is less than 5%, the edge thickness is 5 μm, the resistance is 5 mΩ / square, and the tensile force of the end is 12 LB.

[0049] Example 2

[0050] The glass formula and the glass proportion in the paste of this embodiment are different from those of Example 1, and the other paste processing methods, sintering processes and testing methods are completely the same.

[0051] The paste of this embodiment contains 75% copper powder, 8% glass powder, 16% organic carrier and 1% micron-sized lithia powder by mass percentage.

[0052] The glass powder of this embodiment includes the following components by weight percentage: 25.0% SiO2, 25.0% B2O3, 36.0% BaO, 4.0% CaO, 1.0% Na2O, 7.0% TiO2, 0% CuO, 1.0% Sb2O3, 1.0% NaF.

[0053] The acid and alkali resistance results, hemispherical temperature and transition temperature of the glass powder in this embodiment are shown in Table 1. The weight loss rate of the glass powder in Example 2 is less than 0.2% under acid and alkali resistance. The viscosity change of the copper paste in Example 2 stored for one month is shown in Table 2, and the change rate is less than 5%. The bonding layer with the MLCC end surface is Figure 1 , the porosity of the interface is less than 5%, the edge thickness is 4.5 μm, the resistance is 7 mΩ / square, and the tensile force of the end is 10 LB.

[0054] Example 3

[0055] The glass formula and the glass proportion in the paste of this embodiment are different from those of Example 1, and the other paste processing methods, sintering processes and testing methods are completely the same.

[0056] The paste of this embodiment contains 75% copper powder, 8% glass powder, 16% organic carrier and 1% micron-sized lithia powder by mass percentage.

[0057] The glass powder of the embodiment comprises the following components in percentage by weight: 25.0% SiO2, 25.0% B2O3, 38.0% BaO, 2.0% CaO, 3.0% Na2O, 0.0% TiO2, 5.0% CuO, 1.0% Sb2O3, 1.0% NaF.

[0058] The acid and alkali resistance results, the half-ball temperature and the transition temperature of the glass powder in the embodiment are shown in Table 1. The weight loss rate of the glass powder of Example 3 is less than 0.2% in acid and alkali resistance. The viscosity change of the copper paste of Example 3 stored for one month is shown in Table 2. The change rate is less than 2.0%. The bonding layer with the end surface of the MLCC is shown in Figure 1 . The interface porosity is less than 5%. The edge thickness is 4.3 μm. The resistance is 5 mΩ / square. The pulling force of the end is 9 LB.

[0059] Example 4

[0060] The glass formula and the glass proportion in the paste of the embodiment are different from those of Example 1. The other paste processing method, sintering process and test method are completely the same.

[0061] The paste of the embodiment comprises 75% copper powder, 8% glass powder, 16% organic carrier and 1% micron-level eucryptite powder in percentage by mass.

[0062] The glass powder of the embodiment comprises the following components in percentage by weight: 24.0% SiO2, 29.0% B2O3,

[0063] 35.0% BaO, 2.0% CaO, 2.0% Na2O, 3.0% TiO2, 3.0% CuO, 1.0% Sb2O3, 1.0% NaF.

[0064] The acid and alkali resistance results of the glass powder in the embodiment are shown in Table 1. The weight loss rate of the glass powder of Example 4 is less than 0.2% in acid and alkali resistance. The viscosity change of the copper paste of Example 4 stored for one month is shown in Table 2. The change rate is less than 2.0%. The bonding layer with the end surface of the MLCC is shown in Figure 1 . The interface porosity is less than 5%. The edge thickness is 4.5 μm. The resistance is 11 mΩ / square. The pulling force of the end is 9 LB.

[0065] Example 5

[0066] The glass formula and the glass proportion in the paste of the embodiment are different from those of Example 1. The other paste processing method, sintering process and test method are completely the same.

[0067] The paste of the embodiment comprises 75% copper powder, 8% glass powder, 16% organic carrier and 1% micron-level eucryptite powder in percentage by mass.

[0068] The glass powder in this embodiment comprises the following components in weight percentage: 24.0% SiO2, 26.0% B2O3, 40.0% BaO, 2.0% CaO, 1.0% Na2O, 1.0% TiO2, 4.0% CuO, 1.0% Sb2O3, 1.0% NaF.

[0069] The acid and alkali resistance results of the glass powder in this embodiment are shown in Table 1. The weight loss rate of the glass powder in Example 5 is less than 0.2% under acid and alkali resistance. The viscosity change of the copper paste in Example 5 stored for one month is shown in Table 2. The change rate is less than 2.0%. The bonding layer on the end surface of the MLCC is as shown in Figure 1 , the interface porosity is less than 5%, the edge thickness is 5.0 μm, the resistance is 13 mΩ / square, and the tensile force of the end is 8 LB.

[0070] Example 6

[0071] The glass formula and the glass proportion in the paste in this embodiment are different from those in Example 1. The other paste processing method, sintering process, and test method are completely the same.

[0072] The paste in this embodiment comprises 75% copper powder, 8% glass powder, 16% organic carrier, and 1% micron-grade eucryptite powder in mass percentage.

[0073] The glass powder in this embodiment comprises the following components in weight percentage: 25.0% SiO2, 25.0% B2O3, 38.0% BaO, 2.0% CaO, 3.0% Na2O, 0.0% TiO2, 5.0% CuO, 1.0% Sb2O3, 1.0% NaF.

[0074] The acid and alkali resistance results of the glass powder in this embodiment are shown in Table 1. The weight loss rate of the glass powder in Example 4 is less than 0.2% under acid and alkali resistance. The viscosity change of the copper paste in Example 4 stored for one month is shown in Table 2. The change rate is less than 2.0%. The bonding layer on the end surface of the MLCC is as shown in Figure 1 , the interface porosity is less than 5%, the edge thickness is 5.2 μm, the resistance is 9 mΩ / square, and the tensile force of the end is 12 LB.

[0075] Example 7

[0076] The glass formula, paste processing method, sintering process, and test method in this embodiment are completely the same except that the glass proportion in the paste is different from that in Example 1.

[0077] The paste in this embodiment comprises 71% copper powder, 12% glass powder, 16% organic carrier, and 1% micron-grade eucryptite powder in mass percentage.

[0078] The viscosity change of the copper paste in this example stored for one month is shown in Table 2, and the change rate is less than 2.0%. The bonding layer on the end surface of the MLCC is as shown in FIG. 1, the interface porosity is less than 5%, the edge thickness is 5.2 μm, the resistance is 15 mΩ / square, and the tensile force of the end is 14 LB. Figure 1 The viscosity change of the copper paste in this example stored for one month is shown in Table 2, and the change rate is less than 2.0%. The bonding layer on the end surface of the MLCC is as shown in FIG. 1, the interface porosity is less than 5%, the edge thickness is 5.2 μm, the resistance is 15 mΩ / square, and the tensile force of the end is 14 LB.

[0079] Example 8

[0080] In this example, the glass and copper powder content in the paste is different from that in Example 1, and the other glass formula, paste processing method, sintering process and test method are completely the same.

[0081] The paste described in this example contains 68% copper powder, 15% glass powder, 16% organic carrier and 1% micron-sized eucryptite powder by mass percentage.

[0082] The viscosity change of the copper paste in this example stored for one month is shown in Table 2, and the change rate is less than 2.0%. The bonding layer on the end surface of the MLCC is as shown in FIG. 1, the interface porosity is less than 5%, the edge thickness is 5.2 μm, the resistance is 15 mΩ / square, and the tensile force of the end is 14 LB. Figure 1 The viscosity change of the copper paste in this example stored for one month is shown in Table 2, and the change rate is less than 2.0%. The bonding layer on the end surface of the MLCC is as shown in FIG. 1, the interface porosity is less than 5%, the edge thickness is 5.2 μm, the resistance is 15 mΩ / square, and the tensile force of the end is 14 LB.

[0083] Example 9

[0084] In this example, the inorganic additive content in the paste is different from that in Example 1, and the other glass formula, paste processing method, sintering process and test method are completely the same.

[0085] The paste described in this example contains 75% copper powder, 8% glass powder, 15% organic carrier and 3% micron-sized eucryptite powder by mass percentage.

[0086] The viscosity change of the copper paste in this example stored for one month is shown in Table 2, and the change rate is less than 2.0%. The bonding layer on the end surface of the MLCC is as shown in FIG. 1, the interface porosity is less than 5%, the edge thickness is 5.2 μm, the resistance is 15 mΩ / square, and the tensile force of the end is 14 LB. Figure 1 The viscosity change of the copper paste in this example stored for one month is shown in Table 2, and the change rate is less than 2.0%. The bonding layer on the end surface of the MLCC is as shown in FIG. 1, the interface porosity is less than 5%, the edge thickness is 5.2 μm, the resistance is 15 mΩ / square, and the tensile force of the end is 14 LB.

[0087] Comparative Example 1

[0088] In this example, the inorganic additive content in the paste is different from that in Example 1, and the other glass formula, paste processing method, sintering process and test method are completely the same.

[0089] The paste described in this example contains 75% copper powder, 8% glass powder, 17% organic carrier and 0% micron-sized eucryptite powder by mass percentage.

[0090] The viscosity change of the copper paste in this example stored for one month is shown in Table 2, and the change rate is less than 2.0%. The bonding layer on the end surface of the MLCC is as shown in FIG. 1, the interface porosity is less than 5%, the edge thickness is 5.2 μm, the resistance is 15 mΩ / square, and the tensile force of the end is 14 LB. Figure 1, the interface porosity is less than 5%, the edge thickness is 3.0 μm, the resistance is 12 mΩ / square, and the tensile force of the end is 12 LB.

[0091] Comparative Example 2

[0092] The glass formula, slurry processing method, sintering process and test method of the slurry of the present example are the same as those of Example 1, except that the content of glass powder and copper powder in the slurry is different.

[0093] The slurry of the present example contains 78% copper powder, 5% glass powder, 16% organic carrier and 1% micron-sized eucryptite powder by mass percentage.

[0094] The viscosity change of the copper slurry of the present example stored for one month is shown in Table 2, and the change rate is less than 2.0%. The bonding layer on the end surface of the MLCC is as shown in Figure 1 , the interface porosity is 15%, the edge thickness is 3.8 μm, the resistance is 25 mΩ / square, and the tensile force of the end is 6 LB.

[0095] Comparative Example 3

[0096] The glass formula, slurry processing method, sintering process and test method of the slurry of the present example are the same as those of Example 1, except that the slurry formula is different.

[0097] The slurry of the present example contains 60% copper powder, 8% glass powder, 31% organic carrier and 1% micron-sized eucryptite powder by mass percentage.

[0098] The viscosity change of the copper slurry of the present example stored for one month is shown in Table 2, and the change rate is greater than 2.0%. The bonding layer on the end surface of the MLCC is as shown in Figure 1 , the interface porosity is 20%, the edge thickness is 1.8 μm, the resistance is 200 mΩ / square, and the tensile force of the end is 6 LB.

[0099] Comparative Example 4

[0100] The glass formula, slurry processing method, sintering process and test method of the slurry of the present example are the same as those of Example 1, except that the proportion of the slurry carrier is different.

[0101] The slurry of the present example contains 80% copper powder, 13% glass powder, 6% organic carrier and 1% micron-sized eucryptite powder by mass percentage.

[0102] The viscosity change of the copper slurry of the present example stored for one month is shown in Table 2, and the change rate is greater than 25.0%. The viscosity is too large, and the MLCC is pulled out, which cannot be sealed.

[0103] The acid and alkali weight loss rates, glass powder hemisphere point and glass powder transition temperature of the glass formula and glass powder of Examples 1-6 above are shown in Table 1.

[0104] The viscosity of the slurries of Examples 1 to 8, Comparative Examples 1 to 4 at 1 day, 15 days, 30 days, the thickness of the copper film after sintering, the thickness of the copper film around the edges of the MLCC, the resistivity of the end surface, the end pull, and the porosity of the interface are shown in Table 2.

[0105] Table 1

[0106]

[0107] Table 2

[0108]

[0109]

Claims

1. A copper paste containing glass powder, characterized in that, It is prepared by mixing 65.0~70% copper powder, 7~15% glass powder, 15.0~23.0% organic carrier, and 1~5% inorganic powder additive by mass percentage; wherein, the organic carrier includes carrier A and carrier B; and the inorganic powder additive is nepheline powder. The glass powder is a Zn-free, Bi-free, and lead-free glass powder, and by mass percentage, it comprises the following components: 24.0~26.0% SiO2, 25.0~29.0% B2O3, 30.0~40.0% BaO, 2~7% CaO, 1~5% Na2O, 1.0~4.0% TiO2, 2~5% CuO, 1~5.0% Sb2O3, and 1.0~5.0% NaF.

2. The copper paste containing glass powder according to claim 1, characterized in that, The glass powder has a transition temperature of 520~650℃ and a hemispherical temperature of 650~800℃; the glass powder has a particle size of 1.5~2.5 micrometers and a coefficient of thermal expansion of 6.5~9.5 ppm / ℃.

3. A copper paste containing glass powder according to claim 1 or 2, characterized in that, The preparation of the glass powder includes the following steps: S1. Weigh the glass raw material, put it into a mortar and mix for 10-15 minutes, then put it into a platinum crucible and melt it at 1250-1350℃ for 40-90 minutes. Then pour the molten glass into a double roller mill for cold quenching to make the molten glass into glass sheets. S2. Use a planetary ball mill to coarsely grind the glass sheet prepared in step S1 for 40-60 minutes, then sieve it, and then finely grind it for 70-120 minutes, dry it, and sieve it to obtain glass powder for copper paste. During the fine grinding process, add water or alcohol as the ball milling medium, and the mass ratio of water to glass powder is 1:1.

5.

4. The copper paste containing glass powder according to claim 1, characterized in that: The copper powder is a mixture of polygonal copper powder A and spherical copper powder B, wherein the average particle size of the spherical powder is 4-6 micrometers, the average particle size of the polygonal powder is 1.2-1.8 micrometers, and the weight ratio of polygonal powder to spherical powder is 1:1-3.

5. The copper paste containing glass powder according to claim 1, characterized in that, The organic carrier comprises a solvent and a resin; the solvent comprises one or more of diethylene glycol butyl ether acetate, diethylene glycol butyl ether, dipropylene glycol butyl ether, and terpineol; the resin comprises one or two of ethyl cellulose and acrylic resin.

6. A method for preparing copper paste containing glass powder as described in claim 5, comprising the following steps: S21. Weigh the solvent and resin, and dissolve the resin evenly in the solvent at 80~90℃. Stir thoroughly to form a uniform organic carrier. S22. The organic carrier, glass powder and copper powder prepared in step S21 are weighed and stirred in proportion to form a uniform slurry. The slurry is then fully ground using a three-roll mill to finally prepare a copper slurry that meets the performance requirements.

7. The application of a copper paste containing glass powder according to any one of claims 1 to 5, characterized in that, The slurry is attached to the end face of the MLCC and then dried and sintered to obtain the end electrode. The drying temperature is 120~130℃ and the time is 10~20min. The sintering process is as follows: first, under a wet nitrogen atmosphere, the temperature is raised to 500℃ at a heating rate of 20~50℃ / min and held for 10min. Then, under a dry nitrogen atmosphere, the temperature is raised to 650~750℃ at a heating rate of 30~50℃ / min and held for 10min.

8. The application according to claim 7, characterized in that, The copper end electrode consists of a copper film and a substrate. The end face is free of bulges, cracks, and glass overflow. The average sheet resistance of the copper film is 4.5~15.3mΩ / square.

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