阅读说明：本技术 一种mlcc用高烧结致密性铜浆及其制备方法 (High-sintering compactness copper slurry for MLCC and preparation method thereof ) 是由 高珺 李岩 陈将俊 刘春静 刘啸 吴博 齐亚军 纪煊 于 2021-08-27 设计创作，主要内容包括：本发明提供一种MLCC用高烧结致密性铜浆及其制备方法。所述铜浆配方中各组分按质量百分比为：第一铜粉40-60％；第二铜粉10-30％；第一玻璃粉3-5％；第二玻璃粉0.5-2.5％；有机载体20-25％；以及,助剂0.5-3％；其中,所述第一铜粉与所述第二铜粉为球状铜粉,且所述第一铜粉的平均粒径大于所述第二铜粉的平均粒径；所述第一玻璃粉的玻璃体系不同于所述第二玻璃粉的玻璃体系。本发明还公开了上述铜浆的制备方法,此铜浆通过选用合适的铜粉类型、有机载体体系、助剂种类,以及选用两种体系的玻璃粉进行复配,显著提高了烧结后端电极的致密性,可有效改善电镀时镍渗透不良,提高MLCC产品的可靠性,同时工艺上可降低铜浆的烧结温度,节约能源。(The invention provides high-sintering compactness copper slurry for MLCC and a preparation method thereof. The copper paste formula comprises the following components in percentage by mass: 40-60% of first copper powder; 10-30% of second copper powder; 3-5% of first glass powder; 0.5 to 2.5 percent of second glass powder; 20-25% of organic carrier; and, 0.5-3% of an auxiliary agent; the first copper powder and the second copper powder are spherical copper powders, and the average particle size of the first copper powder is larger than that of the second copper powder; the glass system of the first glass frit is different from the glass system of the second glass frit. The invention also discloses a preparation method of the copper paste, the copper paste obviously improves the compactness of a sintering rear end electrode by selecting a proper copper powder type, an organic carrier system and an auxiliary agent type and selecting two systems of glass powder for compounding, can effectively improve poor nickel penetration during electroplating, improves the reliability of an MLCC product, can reduce the sintering temperature of the copper paste on the process and saves energy.)

1. The high-sintering compactness copper slurry for the MLCC is characterized in that the copper slurry formula comprises the following components in percentage by mass:

40-60% of first copper powder;

10-30% of second copper powder;

3-5% of first glass powder;

0.5 to 2.5 percent of second glass powder;

20-25% of organic carrier; and the number of the first and second groups,

0.5 to 3 percent of auxiliary agent;

the first copper powder and the second copper powder are spherical copper powders, and the average particle size of the first copper powder is larger than that of the second copper powder; the glass system of the first glass frit is different from the glass system of the second glass frit.

2. The high-sintering-density copper paste for MLCC according to claim 1, wherein the first copper powder has an average particle size of 1.1-4 μm and a tap density of 3.5g/cm or more³Specific surface area of 0.8-2.2cm²(ii)/g; the average particle diameter of the second copper powder is 0.1-0.3 μm, and the tap density is 1.8-2.5g/cm³The specific surface area is more than or equal to 3.0cm²/g。

3. The highly sintered compact copper paste for MLCC according to claim 1, wherein the first glass frit is Bi-based glass composed of Bi₂O₃、B₂O₃、SiO₂、MgO、CaO、CuO、ZrO₂At least four components with an average particle size of 0.8-2 μm and a softening point of 450-550 ℃; the second glass powder is Zn glass composed of ZnO, BaO and B₂O₃、Al₂O₃、TiO₂、NiO、Li₂O、Na₂O、MnO₂Has an average particle diameter of 0.8 to 2 μm and a softening point of 550-650 ℃.

4. The high-sintering compactness copper paste for MLCC according to claim 1, wherein the organic carrier comprises resin and organic solvent, wherein the resin accounts for 15-40% of the mass of the organic carrier; the organic solvent accounts for 60-85% of the mass of the vehicle.

5. The high sintering density copper paste for MLCC according to claim 4, wherein the resin is at least one of ethyl cellulose, cellulose acetate butyrate and acrylic resin.

6. The high-sintering-density copper paste for MLCCs according to claim 4, wherein the organic solvent is at least one of acetone, turpentine, terpineol, dihydroterpineol, ethylene glycol butyl ether, diethylene glycol butyl ether acetate, tributyl citrate, and dibutyl phthalate.

7. The high-sintering compactness copper paste for MLCC according to claim 1, wherein the auxiliary agent is at least one of oleic acid, linoleic acid, stearic acid, span 85, alkyl polyoxyethylene ether phosphate ester coupling agent and titanate coupling agent.

8. A method for preparing the high-sintering compactness copper slurry for MLCC according to any of claims 1 to 7, which comprises the following steps:

s1, preparing an organic carrier: adding an organic solvent weighed according to a ratio into a reaction kettle with a water bath function, setting the water bath temperature to be 75-85 ℃, stirring and preheating for 0.2-0.8h by using a planetary stirrer at a rotating speed of 50-100rpm, adding resin weighed according to the ratio into the reaction kettle, setting the rotating speed of the stirrer to be 500-800rpm, keeping the temperature for 3-8h, and discharging for later use after the resin is completely dissolved;

s2, preparing glass powder: weighing glass powder raw materials in a mortar according to a ratio, uniformly mixing and grinding the raw materials, adding the mixture into an alumina crucible, placing the alumina crucible in a high-temperature furnace, heating the furnace to 1000 ℃ and 1400 ℃, preserving heat for 1-3 hours to uniformly melt the mixture, pouring glass liquid into a sheet rolling machine with a water-cooled steel roller, cold-rolling the glass liquid into glass broken slag, and performing ball-milling and drying to obtain glass powder for later use;

s3, weighing and proportioning: sequentially adding an organic carrier, an auxiliary agent, glass powder and copper powder into a batching barrel according to the raw material ratio in the formula;

s4, mixing: uniformly stirring the raw materials by using a stirrer until no obvious lumps exist;

s5, grinding by a three-roller machine: rolling the uniformly mixed slurry for 5-10 times by a hydraulic three-roller machine until the fineness reaches below 10 mu m;

s6, filtering: and filtering the ground slurry through 300-mesh filter cloth to obtain a slurry finished product after filtering.

Technical Field

The invention relates to the technical field of terminal electrode slurry for MLCC (multilayer ceramic capacitor), in particular to high-sintering compactness copper slurry for MLCC and a preparation method thereof.

Background

The chip multilayer ceramic capacitor (MLCC) is an important large class of passive electronic components, has wide application in various industries such as consumer electronics, automobiles, medical treatment, aerospace, war industry and the like, and is called industrial rice. With the development of industries such as electronic information, internet of things, electric vehicles and the like, the use amount of the MLCC is increased year by year, and the market prospect is very wide.

The MLCC product structurally comprises a dielectric ceramic body, an internal electrode and an external electrode, and before the 90's of the last century, the internal electrode and the external electrode are made of precious metal materials such as silver, palladium and the like, so that the price is very high. With the increasing urgency of product cost reduction and the breakthrough of co-firing technology in protective or reducing atmosphere, from the middle and late 90 s, base metals such as nickel and copper gradually replace precious metals as internal and external electrode materials, and enter into commercial production, thereby greatly reducing production cost.

At present, in the civil MLCC product, although most manufacturers use copper as an external electrode material, a plurality of problems still exist in the use process of copper paste: copper powder is easily oxidized in air, the sintering activity of the copper powder is not as high as that of silver powder, poor sintering is easy to occur, particularly, the compactness is poor after sintering, and nickel in electroplating solution is easy to permeate into a copper electrode or even the inside of a porcelain body during electroplating, so that the yield and the performance of products are influenced. Therefore, there is a need to develop a new copper paste to solve the disadvantages of the prior art.

Disclosure of Invention

According to the technical problems of easy oxidation of copper powder, poor sintering activity of the copper powder, poor compactness after sintering and the like of the existing copper slurry, the high-sintering compactness copper slurry for the MLCC and the preparation method thereof are provided. The invention mainly aims at the improvement of the MLCC copper end electrode, adjusts the formula of the slurry, utilizes copper powder with different grain diameters to mix with glass powder of different systems, and then prepares the copper slurry by matching with an organic carrier and an auxiliary agent, so that the sintered slurry has higher sintering compactness, thereby achieving the purposes of end attachment of the copper slurry on the MLCC product and high electrode compactness after sintering, having excellent nickel penetration resistance, and being capable of being applied under the process condition of low sintering temperature (680-plus-700 ℃) and saving energy sources compared with the existing copper slurry products in the market.

The technical means adopted by the invention are as follows:

the high-sintering compactness copper slurry for the MLCC is characterized in that the copper slurry formula comprises the following components in percentage by mass:

40-60% of first copper powder;

10-30% of second copper powder;

3-5% of first glass powder;

0.5 to 2.5 percent of second glass powder;

20-25% of organic carrier; and the number of the first and second groups,

0.5 to 3 percent of auxiliary agent;

the first copper powder and the second copper powder are spherical copper powders, and the average particle size of the first copper powder is larger than that of the second copper powder; the glass system of the first glass frit is different from the glass system of the second glass frit.

Furthermore, the average grain diameter of the first copper powder is 1.1-4 μm, and the tap density is more than or equal to 3.5g/cm³Specific surface area of 0.8-2.2cm²(ii)/g; the average particle diameter of the second copper powder is 0.1-0.3 μm, and the tap density is 1.8-2.5g/cm³The specific surface area is more than or equal to 3.0cm²/g。

Further, the first glass frit is Bi-based glass composed of Bi₂O₃、B₂O₃、SiO₂、MgO、CaO、CuO、ZrO₂At least four components with an average particle size of 0.8-2 μm and a softening point of 450-550 ℃; the second glass powder is Zn glass composed of ZnO, BaO and B₂O₃、MgO、Al₂O₃、TiO₂、NiO、Li₂O、Na₂O、MnO₂Has an average particle diameter of 0.8 to 2 μm and a softening point of 550-650 ℃.

Further, the organic carrier comprises resin and an organic solvent, wherein the resin accounts for 15-40% of the mass of the organic carrier; the organic solvent accounts for 60-85% of the mass of the vehicle.

Further, the resin is at least one of ethyl cellulose, cellulose acetate butyrate and acrylic resin.

Further, the organic solvent is at least one of acetone, turpentine, terpineol, dihydroterpineol, ethylene glycol butyl ether, diethylene glycol butyl ether acetate, tributyl citrate and dibutyl phthalate.

Further, the auxiliary agent is at least one of oleic acid, linoleic acid, stearic acid, span 85, alkyl polyoxyethylene ether phosphate coupling agent and titanate coupling agent.

The invention also discloses a preparation method of the high-sintering compactness copper slurry for the MLCC, which is characterized by comprising the following steps of:

s1, preparing an organic carrier: adding organic solvent weighed according to a ratio into a reaction kettle with a water bath function, setting the water bath temperature to be 75-85 ℃, preferably setting the water bath temperature to be 80 ℃, stirring and preheating for 0.2-0.8h, preferably 0.5h, at the rotating speed of 50-100rpm by using a planetary stirrer, adding resin weighed according to the ratio into the reaction kettle, setting the rotating speed of a stirrer to be 500 plus materials 800rpm, keeping the temperature for 3-8h, and discharging for later use after the resin is completely dissolved;

s2, preparing glass powder: weighing glass powder raw materials in a mortar according to a ratio, uniformly mixing and grinding the raw materials, adding the mixture into an alumina crucible, placing the alumina crucible in a high-temperature furnace, heating the furnace to 1000 ℃ and 1400 ℃, preserving heat for 1-3 hours to uniformly melt the mixture, pouring glass liquid into a sheet rolling machine with a water-cooled steel roller, cold-rolling the glass liquid into glass broken slag, and performing ball-milling and drying to obtain glass powder for later use;

s3, weighing and proportioning: sequentially adding an organic carrier, an auxiliary agent, glass powder and copper powder into a batching barrel according to the raw material ratio in the formula;

s4, mixing: uniformly stirring the raw materials by using a stirrer until no obvious lumps exist;

s5, grinding by a three-roller machine: rolling the uniformly mixed slurry for 5-10 times by a hydraulic three-roller machine until the fineness reaches below 10 mu m;

s6, filtering: and filtering the ground slurry through 300-mesh filter cloth to obtain a slurry finished product after filtering.

Compared with the prior art, the invention has the following advantages:

1. the copper powder with two different particle sizes is selected for compounding, so that the characteristics of micron-sized copper powder and submicron-sized copper powder are considered, the first copper powder is micron-sized copper powder, the tap density is high, and the porosity is low after stacking; the second copper powder is added to be submicron copper powder, the particle size is small, the specific surface area is high, the sintering activity of the copper powder is high, and the second copper powder is filled in the pores of the first copper powder, so that the porosity can be further reduced, the density is improved, and the sintering temperature is effectively reduced.

2. The invention selects two different systems of glass powder to be compounded, and aims to ensure that the first glass powder is Bi glass₂O₃、B₂O₃、SiO₂、MgO、CaO、CuO、ZrO₂The average grain diameter of the glass is 0.8-2 mu m, the softening point is 450-550 ℃, the glass is preferentially melted in the sintering process, the wettability to copper powder is good, the glass can react with an oxide layer on the surface of the copper powder to promote the sintering of the copper powder and improve the density; the second glass powder is Zn glass composed of ZnO, BaO and B₂O₃、MgO、Al₂O₃、TiO₂、NiO、Li₂O、Na₂O、MnO₂The average grain diameter of the glass is 0.8-2 mu m, the softening point is 550-650 ℃, the glass has high softening point, is melted in the later section of the sintering process, and is filled in the residual gaps, thereby being beneficial to further improving the compactness.

3. In the auxiliary agents adopted in the invention, the oleic acid and the linoleic acid have good affinity to copper powder, the dispersibility of the small-particle-size copper powder can be improved, and the coating wettability of resin to the copper powder can be improved by the coupling agents.

In conclusion, the copper paste formula of the invention obviously improves the compactness of the sintered rear-end electrode by selecting the proper copper powder type, the proper organic carrier system and the proper auxiliary agent type and selecting the glass powder of the two systems for compounding, can effectively improve poor nickel penetration during electroplating, improves the reliability of MLCC products, can reduce the sintering temperature of the copper paste on the process and saves energy.

For the reasons, the invention can be widely popularized in the field of MLCC terminal electrode slurry.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a scanning electron microscope picture of copper paste after MLCC termination and sintering at 700 ℃ in the prior art.

FIG. 2 is a scanning electron microscope image of the copper paste prepared in example 1 of the present invention after MLCC termination and sintering at 700 ℃.

FIG. 3 is a scanning electron microscope image of the copper paste prepared in example 2 of the present invention after MLCC termination and sintering at 700 ℃.

FIG. 4 is a scanning electron microscope image of the copper paste prepared in example 3 of the present invention after MLCC termination and sintering at 700 ℃.

Detailed Description

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

The invention discloses high-sintering compactness copper slurry for MLCC (multilayer ceramic capacitor), which comprises the following components in percentage by mass: 40-60% of first copper powder; 10-30% of second copper powder; 3-5% of first glass powder; 0.5 to 2.5 percent of second glass powder; 20-25% of organic carrier; and, 0.5-3% of an auxiliary agent; the first copper powder and the second copper powder are spherical copper powders, and the average particle size of the first copper powder is larger than that of the second copper powder; the glass system of the first glass powder is different from that of the second glass powder, and is prepared by the following steps:

s1, preparing an organic carrier: adding an organic solvent weighed according to a ratio into a reaction kettle with a water bath function, setting the water bath temperature to be 80 ℃, stirring and preheating for 0.5h by using a planetary stirrer at a rotating speed of 50-100rpm, adding resin weighed according to the ratio into the reaction kettle, setting the rotating speed of the stirrer to be 500 plus materials at 800rpm, keeping the temperature for 3-8h, and discharging for later use after the resin is completely dissolved;

s2, preparing glass powder: weighing glass powder raw materials in a mortar according to a ratio, uniformly mixing and grinding the raw materials, adding the mixture into an alumina crucible, placing the alumina crucible in a high-temperature furnace, heating the furnace to 1000 ℃ and 1400 ℃, preserving heat for 1-3 hours to uniformly melt the mixture, pouring glass liquid into a sheet rolling machine with a water-cooled steel roller, cold-rolling the glass liquid into glass broken slag, and performing ball-milling and drying to obtain glass powder for later use;

s3, weighing and proportioning: sequentially adding an organic carrier, an auxiliary agent, glass powder and copper powder into a batching barrel according to the raw material ratio in the formula;

s4, mixing: uniformly stirring the raw materials by using a stirrer until no obvious lumps exist;

s5, grinding by a three-roller machine: rolling the uniformly mixed slurry for 5-10 times by a hydraulic three-roller machine until the fineness reaches below 10 mu m;

s6, filtering: and filtering the ground slurry through 300-mesh filter cloth to obtain a slurry finished product after filtering.

Example 1

The invention provides high-sintering compactness copper slurry for MLCC, which comprises the following components in percentage by mass: 50% of first copper powder, 22% of second copper powder, 3.2% of first glass powder, 2.5% of second glass powder, 21% of organic carrier and 1.3% of auxiliary agent.

Wherein the first copper powder and the second copper powder are spherical copper powders, the average particle diameter of the first copper powder is 1.5 μm, and the tap density is 3.8g/cm³(ii) a The average particle diameter of the second spherical copper powder is 0.11 μm, and the tap density is 2.1g/cm³Specific surface area 3.5cm²/g。

The first glass powder comprises Bi₂O₃38% of CuO, 20% of B₂O₃12.5% of SiO₂15% of CaO, 8% of CaO, ZrO₂6.5 percent; the second glass powder comprises 30 percent of ZnO, 45 percent of BaO and B₂O₃12% of Al₂O₃3.5%, MgO 2%, TiO₂3% of Li₂O is 4.5%.

The organic carrier is prepared by mixing ethyl cellulose, terpineol and alcohol ester twelve, wherein the proportions of the ethyl cellulose, the terpineol and the alcohol ester twelve are respectively 15%, 30% and twelve 55%.

The assistant is a mixed assistant of 0.8 percent of oleic acid and 0.5 percent of alkyl polyoxyethylene ether phosphate coupling agent.

Mixing the above components, grinding for 10 times with a three-roll mill until the fineness reaches 8 μm, filtering with a 300-mesh filter screen to obtain copper slurry, sealing with MLCC, sintering at 700 deg.C, and testing the density of the end head with a scanning electron microscope (as shown in FIG. 2). Fig. 1 shows a conventional copper paste product on the market, and it can be found that the density of the copper paste in embodiment 1 of the present invention is significantly better than that of the conventional copper paste product, and the Ni penetration phenomenon in the subsequent electroplating process can be effectively reduced.

Example 2

Compared with the example 1, only single copper powder is selected for proportioning, the average particle diameter of the copper powder is 1.5 mu m, and the tap density is 3.8g/cm³(ii) a The types and proportions of the first glass frit, the second glass frit, the organic vehicle and the auxiliary agent are the same as those in example 1.

The copper paste comprises the following components in percentage by mass: 72% of copper powder, 3.2% of first glass powder, 2.5% of second glass powder, 21% of organic carrier and 1.3% of auxiliary agent. Mixing the above components, grinding for 10 times with a three-roller machine until the fineness reaches 8 μm, and filtering with a 300-mesh filter screen to obtain copper slurry.

FIG. 3 is an SEM picture of the density of the copper paste of example 2 after sintering at 700 ℃ on an MLCC, which shows that the density is better than that of FIG. 1, but slightly worse than that of FIG. 2, some holes are left between the crystal grains of copper and are not completely filled, and the density of the copper paste after sintering is worse than that of the paste compounded by micron copper powder and submicron copper powder by using single copper powder.

Example 3

Compared with the example 1, only single Zn-based glass powder is selected for compounding, and the types and the proportions of the first copper powder, the second copper powder, the organic carrier and the auxiliary agent are consistent with those of the example 1.

The components are as follows by mass percent: 50% of first copper powder, 22% of second copper powder, 5.7% of Zn glass powder, 21% of organic carrier and 1.3% of auxiliary agent. Mixing the above components, grinding for 10 times with a three-roller machine until the fineness reaches 8 μm, and filtering with a 300-mesh filter screen to obtain copper slurry.

Fig. 4 is an SEM picture of density observation of the copper paste of example 3 after sintering at 700 ℃ on the MLCC, which shows that the density is better than that of fig. 1, but slightly worse than that of fig. 2, and slight glass blistering appears, which indicates that the addition of Bi-based glass has a sintering-assisting effect on copper powder, and can promote the copper powder to be sintered compactly.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.