Copper paste and preparation method and application thereof
阅读说明：本技术 一种铜浆及其制备方法与应用 (Copper paste and preparation method and application thereof ) 是由 欧阳铭 谢子城 谢鸿察 陈樱琳 廖明雅 吴海斌 罗文忠 宋永生 于 2021-08-17 设计创作，主要内容包括：本发明公开了一种铜浆及其制备方法与应用。本发明铜浆包括以下重量百分含量的组分：铜粉75-85％,玻璃粉0.5-2％,甘油磷酸酯0.5-2.0％,有机溶剂和有机树脂共占11-22.5％,其中,有机树脂质量为有机溶剂和有机树脂总质量的11-15％。将本发明铜浆以丝网印刷的方式涂布在芯片两端以形成端电极,即便芯片尺寸为0.8mm*0.8mm、0.5mm*0.5mm、0.38mm*0.38mm,甚至更小规格,所得MLCC表面平整,且平整度优于传统铜浆通过浸封工艺制得的MLCC。(The invention discloses copper paste and a preparation method and application thereof. The copper paste comprises the following components in percentage by weight: 75-85% of copper powder, 0.5-2% of glass powder, 0.5-2.0% of glycerophosphate, and 11-22.5% of organic solvent and organic resin, wherein the mass of the organic resin is 11-15% of the total mass of the organic solvent and the organic resin. The copper paste is coated on two ends of a chip in a screen printing mode to form end electrodes, even if the size of the chip is 0.8mm x 0.8mm, 0.5mm x 0.5mm, 0.38mm x 0.38mm or smaller, the obtained MLCC has a flat surface, and the flatness of the MLCC is superior to that of the MLCC prepared by the traditional copper paste through a dip sealing process.)
1. The copper paste is characterized by comprising the following components in percentage by weight: 75-85% of copper powder, 0.5-2% of glass powder, 0.5-2.0% of glycerophosphate, and 11-22.5% of organic solvent and organic resin, wherein the mass of the organic resin is 11-15% of the total mass of the organic solvent and the organic resin.
2. The copper paste according to claim 1, wherein the copper powder is at least one of spherical copper powder and flake copper powder, and has a specific surface area of 1.0 to 5.0m2The grain size D50 is less than or equal to 5 mu m.
3. The copper paste according to claim 1, wherein the glass powder comprises the following components in percentage by weight: b is2O3 32-35％，SiO2 21-28％，ZnO 20-22％，Al2O3 16-18％，Ag2O0.5-1.5％，ZrO21-2% of NbO 1-2%; the D50 of the glass powder is less than or equal to 8 mu m.
4. The copper paste according to claim 1, wherein the organic solvent comprises at least one of isooctanol and hydrogenated terpineol, and the total mass fraction of isooctanol and hydrogenated terpineol in the organic solvent is 20-100%.
5. The copper paste according to claim 4, wherein the organic solvent further contains mineral spirits.
6. The copper paste according to claim 1, wherein the organic resin comprises ethyl cellulose and hydrogenated rosin; preferably, the mass ratio of the ethyl cellulose to the hydrogenated rosin is ethyl cellulose: hydrogenated rosin is 1:5 to 1: 15.
7. The copper paste according to any one of claims 1 to 6, wherein the copper paste has an average fineness of 6.0 μm or less, a viscosity of 30 to 50 Pa-S/25 ℃, and an inorganic solid content of 75.5 to 87%.
8. The method for preparing copper paste according to any one of claims 1 to 7, wherein the organic solvent comprises a first organic solvent and a second organic solvent, and the mass ratio of the glycerophosphate to the second organic solvent is glycerophosphate: a second organic solvent ═ 1:3 to 1:5, the preparation method comprising the steps of:
mixing and dissolving a first organic solvent and an organic resin to form an organic carrier;
mixing and dispersing copper powder, glycerophosphate and a second organic solvent, and then mixing and dispersing the mixture with an organic carrier and glass powder to obtain copper paste; preferably, the second organic solvent is at least one of isooctanol, hydrogenated terpineol and mineral spirit; preferably, the fineness of 90% position of the mixed and dispersed copper powder, glycerophosphate and second organic solvent is less than or equal to 5 μm.
9. A method for preparing a terminal electrode of a chip type multilayer ceramic capacitor is characterized by comprising the following steps: the copper paste of any one of claims 1 to 7 is coated on both ends of a chip by means of screen printing, and is dried and sintered to form a terminal electrode.
10. The method of claim 9, wherein the length and width of the chip are respectively 0.8mm or less.
Technical Field
The invention relates to the field of copper paste and chip multilayer ceramic capacitors, in particular to copper paste and a preparation method and application thereof.
Background
As shown in fig. 1, a chip type multilayer ceramic capacitor (MLCC), which is mainly composed of three parts of an internal electrode, a ceramic layer and a terminal electrode, is manufactured by stacking ceramic dielectric materials with the internal electrode in a staggered manner, then sintering at a high temperature to form a chip, and then sealing the terminal electrode at both ends of the chip, is similar to a monolithic structure, so the MLCC is also commonly referred to as a "monolithic capacitor". At present, the end electrodes are prepared by adopting copper end electrode slurry on the civil MLCC, the slurry is coated on two ends of a chip through a dip-seal process, however, along with the increasing demand on miniaturization of the MLCC in the market, the copper end electrode slurry is coated on the end heads of products with the sizes of 0.8mm x 0.8mm, 0.5mm x 0.5mm, 0.38mm x 0.38mm and even smaller specifications by using the dip-seal process, the problem of end head unevenness can occur, and the serious problem of end head unevenness can cause various fatal defects of MLCC products.
Therefore, in order to meet the market demand, it becomes very important to research and invent a copper end electrode slurry coating technology capable of effectively avoiding the problem of unevenness of the end of a product.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide copper paste and a preparation method and application thereof, wherein the copper paste is coated on two ends of a chip in a screen printing mode, and even if the size of the chip is 0.8mm by 0.8mm, 0.5mm by 0.5mm, 0.38mm by 0.38mm or even smaller, the obtained MLCC has a flat surface and good performance.
In order to achieve the above object, in a first aspect of the present invention, there is provided a copper paste, which comprises the following components in percentage by weight: 75-85% of copper powder, 0.5-2% of glass powder, 0.5-2.0% of glycerophosphate, and 11-22.5% of organic solvent and organic resin, wherein the mass of the organic resin is 11-15% of the total mass of the organic solvent and the organic resin.
The existing copper end electrode slurry is suitable for a dip-sealing process but not suitable for a screen printing process. Through a great deal of research, the inventors obtain the copper paste with the specific formula, the copper paste is suitable for a screen printing process, the copper paste is coated on two ends of a chip in a screen printing mode, and even if the chip size is 0.8mm by 0.8mm, 0.5mm by 0.5mm, 0.38mm by 0.38mm or even smaller, the obtained MLCC has a flat surface and good performance.
Preferably, the copper powder is at least one of spherical copper powder and flake copper powder, and the specific surface area is 1.0-5.0m2The grain size D50 is less than or equal to 5 mu m. Copper powder is the main component of the copper end electrode slurry, the content of the copper powder in the slurry is directly related to the conductivity and the rheological property of the slurry, so the copper powder with proper morphology and good dispersibility is selected according to the requirement in design, and the specific surface can be selected to be 1.0-5.0m2Spherical or flaky copper powder with/g and the particle size D50 being less than or equal to 5 mu m or the mixture of the spherical and flaky copper powder and the spherical or flaky copper powder.
Preferably, the glass powder comprises the following components in percentage by weight: b is2O3 32-35％，SiO2 21-28％，ZnO 20-22％，Al2O3 16-18％，Ag2O 0.5-1.5％，ZrO21-2% of NbO 1-2%; the D50 of the glass powder is less than or equal to 8 mu m. The glass powder is a key component of the copper-end electrode slurry, and the components and the component proportion of the glass powder are directly related to the adhesion and acid resistance of the sintered slurry and the MLCC end. The glass powder with the specific formula can be selected in order to ensure that the terminal electrode has good acid resistance and good adhesion with the MLCC terminal.
Preferably, the glass powder does not contain harmful components such as lead, cadmium and the like, and is safe and environment-friendly.
Preferably, the organic solvent contains at least one of isooctanol and hydrogenated terpineol, and the total mass fraction of isooctanol and hydrogenated terpineol in the organic solvent is 20-100%. The organic solvent is required to satisfy the following conditions: 1) dissolving the resin to fully disperse the copper powder in the polymer; 2) adjusting the viscosity of the copper end electrode slurry and the stability of the viscosity; 3) the drying speed is determined so that the paste is not quick dried in the printing process. In view of this, the above-mentioned high boiling point solvent comprising isooctanol and/or hydrogenated terpineol is selected.
Preferably, the organic solvent further contains mineral spirits. The organic solvent may consist of at least one of isooctanol and hydrogenated terpineol alone, or may contain other organic solvent components such as mineral spirits.
Preferably, the organic resin includes ethyl cellulose and hydrogenated rosin. Organic resin and organic solvent form an organic carrier of copper paste, the organic resin and the organic solvent are required to be mixed and stirred for 1-2 hours at 70-90 ℃ to form uniform and transparent fluid with certain viscosity, the copper paste forms a printing material with certain viscosity by means of the fluid before screen printing, and after the screen printing is finished, stable combination is formed between particles and a base material in the copper end electrode paste through drying and sintering processes. In view of this, the organic resin may be selected to include ethyl cellulose and hydrogenated rosin, and further preferably, the mass ratio of the ethyl cellulose to the hydrogenated rosin is ethyl cellulose: the hydrogenated rosin is 1:5 to 1: 15.
Preferably, the average fineness of the copper paste is less than or equal to 6.0 mu m, the viscosity is 30-50 Pa.S/25 ℃, and the inorganic solid content is 75.5-87%.
In a second aspect, the present invention provides a method for preparing the above copper paste, wherein the organic solvent is composed of a first organic solvent and a second organic solvent, and the mass ratio of the glycerophosphate to the second organic solvent is glycerophosphate: a second organic solvent ═ 1:3 to 1:5, the preparation method comprising the steps of:
mixing and dissolving a first organic solvent and an organic resin to form an organic carrier;
and mixing and dispersing copper powder, glycerophosphate and a second organic solvent, and then mixing and dispersing with an organic carrier and glass powder to obtain the copper paste.
Preferably, the second organic solvent is at least one of isooctanol, hydrogenated terpineol, mineral spirits.
Preferably, the fineness of 90% position of the mixed and dispersed copper powder, glycerophosphate and second organic solvent is less than or equal to 5 μm. Namely, the fineness of 90 percent of the copper powder, the glycerophosphate and the second organic solvent before being mixed with the organic carrier and the glass powder is less than or equal to 5 mu m.
Preferably, the first organic solvent comprises at least one of isooctanol, hydrogenated terpineol. The first organic solvent may consist of at least one of isooctanol, hydrogenated terpineol alone, or may contain other organic solvent components such as mineral spirits.
In a third aspect, the present invention also provides a method for preparing a terminal electrode of a chip multilayer ceramic capacitor, comprising the steps of: and coating the copper paste on two ends of the chip in a screen printing mode, and drying and sintering to form the terminal electrode. The copper paste is coated on two ends of the chip by adopting a screen printing mode, and the surface flatness of the prepared MLCC is superior to that of the MLCC prepared by the traditional paste through screen printing and dip sealing processes.
Preferably, the length and width of the chip are respectively below 0.8 mm. The length and width here are the length and width of the chip surface coated with the copper paste.
Compared with the prior art, the invention has the beneficial effects that:
(1) the copper paste is coated on two ends of a chip in a screen printing mode to form end electrodes, even if the sizes of the chip are 0.8mm x 0.8mm, 0.5mm x 0.5mm, 0.38mm x 0.38mm and even smaller, the obtained MLCC has flat surfaces, such as the MLCC formed by the chip screen printing of 0.8mm x 0.8mm, 0.5mm x 0.5mm and 0.38mm x 0.38mm specifications, the arithmetic mean deviation Ra of the screen printing surface profile is below 0.25 mu m, and the flatness is superior to the MLCC prepared by the traditional copper paste through a dip-sealing process.
(2) In the copper paste, the surface of the copper powder is treated by the glycerophosphate, so that the copper paste has oxidation resistance and good rheological property.
(3) The copper paste has wide prospect, is approved by the existing customers, and is also a potential customer by other domestic manufacturers for producing the microminiature MLCC.
Drawings
Fig. 1 is a schematic structural diagram of an MLCC.
Detailed Description
To better illustrate the objects, aspects and advantages of the present invention, the present invention will be further described with reference to specific examples. It will be understood by those skilled in the art that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In the examples, the experimental methods used were all conventional methods unless otherwise specified, and the materials, reagents and the like used were commercially available without otherwise specified.
The copper paste is prepared by the preparation method comprising the following steps:
(1) mixing organic resin and an organic solvent, and fully stirring and dissolving at 70-90 ℃ for 1-2h to obtain an organic carrier, wherein the mass content of the organic resin in the organic carrier is 16-22%, and the mass content of the organic solvent is 78-84%;
(2) and (2) fully mixing the organic carrier obtained in the step (1) with copper powder, glass powder and glycerophosphate, and grinding for 6-8 times by using a three-roll grinder to obtain copper slurry. The average fineness of the obtained copper slurry is less than or equal to 6.0 mu m, the viscosity is 30-50 Pa.S/25 ℃, and the inorganic solid content is 75.5-87%.
Example 1
The embodiment provides a copper paste, which is prepared by the following steps:
1. mixing the materials according to the formula shown in the table 1, and stirring and dissolving the materials in a water bath at the temperature of 80 ℃ for 1.5 hours to obtain an organic carrier;
TABLE 1 organic vehicle formulation
Name of Material
Producing area
Mass percent
Isooctyl alcohol
An inlet
53％
Mineral oil extract
An inlet
30.5％
Hydrogenated rosin
An inlet
1.5％
Ethyl cellulose
An inlet
15％
2. According to the formula shown in table 2, before being added into an organic carrier, copper powder is homogenized, wetted and dispersed in a mixed solution of glycerophosphate and isooctanol (wherein the weight ratio of the glycerophosphate to the isooctanol is 1:5) until the fineness of 90% is less than or equal to 5 microns to form a rheology modified coating, and then the rheology modified coating is mixed with the organic carrier and glass powder, then the mixture is reinforced and dispersed by a homogenizer and is ground for 6-8 times by a three-roll mill to obtain copper slurry, wherein D50 of the glass powder is less than or equal to 8 microns, and the composition is shown in table 3; the copper powder is ZC-1000S spherical copper powder produced by Zeuzu New Material science and technology Limited, Hunan Tan City, and the specific surface area is 1.0-5.0m2The grain size D50 is less than or equal to 5 mu m.
TABLE 2 copper paste formulation
Name of Material
Producing area
Mass percent
Organic vehicle
Self-made
13％
Glass powder
Self-made
1.0％
Copper powder
Self-made
80％
Glycerol phosphate ester
An inlet
1.0％
Isooctyl alcohol
An inlet
5.0％
TABLE 3 glass powder formulation
Name of Material
Mass percent
B2O3
33.5％
SiO2
24.5％
ZnO
21％
Al2O3
17％
Ag2O
1.0％
ZrO2
1.5％
NbO
1.5％
The copper powder obtained in the embodiment is printed at two ends of a chip (0603 specification) by adopting a screen printing mode, and is dried and sintered to form end electrodes, so that the MLCC is obtained. The copper paste of this example and the resulting MLCC properties are shown in Table 4.
TABLE 4 copper paste and MLCC Performance
Example 2
The embodiment provides a copper paste, which is prepared by the following steps:
1. mixing the materials according to the formula shown in the table 5, and stirring and dissolving the materials in a water bath at the temperature of 80 ℃ for 1.5 hours to obtain an organic carrier;
TABLE 5 organic vehicle formulation
2. According to the formula shown in table 6, before adding copper powder into an organic carrier, homogenizing, wetting and dispersing the copper powder in a mixed solution of glycerol phosphate and hydrogenated terpineol (wherein the weight ratio of the glycerol phosphate to the hydrogenated terpineol is 1:4) until the fineness of 90% is less than or equal to 5 microns to form a rheology modified coating, then mixing the rheology modified coating with the organic carrier and glass powder, reinforcing and dispersing the mixture by using a homogenizer, and grinding the mixture for 6 to 8 times by using a three-roll mill to obtain copper slurry, wherein the D50 of the glass powder is less than or equal to 8 microns, and the composition is shown in table 7; the copper powder is ZC-1000S spherical copper powder produced by Zeuzu New Material science and technology Limited, Hunan Tan City, and the specific surface area is 1.0-5.0m2The grain size D50 is less than or equal to 5 mu m.
TABLE 6 copper paste formulation
Name of Material
Producing area
Mass percent
Organic vehicle
Self-made
20.5％
Glass powder
Self-made
2％
Copper powder
Self-made
75％
Glycerol phosphate ester
An inlet
0.5％
Hydrogenated terpineol
An inlet
2.0％
TABLE 7 glass powder formulation
Name of Material
Mass percent
B2O3
35％
SiO2
21％
ZnO
22％
Al2O3
18％
Ag2O
1.5％
ZrO2
1.5％
NbO
1.0％
The copper powder obtained in the embodiment is printed at two ends of a chip (0603 specification) by adopting a screen printing mode, and is dried and sintered to form end electrodes, so that the MLCC is obtained. The copper paste of this example and the resulting MLCC performance are shown in Table 8.
TABLE 8 copper paste and MLCC Performance
Example 3
The embodiment provides a copper paste, which is prepared by the following steps:
1. mixing the materials according to the formula shown in the table 9, and stirring and dissolving the materials in a water bath at the temperature of 80 ℃ for 1.5 hours to obtain an organic carrier;
TABLE 9 organic vehicle formulation
Name of Material
Producing area
Mass percent
Hydrogenated terpineol
An inlet
48％
Mineral oil extract
An inlet
30％
Hydrogenated rosin
An inlet
2％
Ethyl cellulose
An inlet
20％
2. According to the formula shown in table 10, before adding copper powder into an organic carrier, homogenizing, wetting and dispersing in a mixed solution of glycerophosphate and mineral oil essence (wherein the weight ratio of the glycerophosphate to the mineral oil essence is 1:3) according to a weight ratio of 1:3 until the fineness of 90% is less than or equal to 5 microns to form a rheological modified coating, then mixing with the organic carrier and glass powder, performing enhanced dispersion by using a homogenizer, and grinding for 6-8 times by using a three-roll mill to obtain copper slurry, wherein the D50 of the glass powder is less than or equal to 8 microns, and the composition is shown in table 11; the copper powder is ZC-1000S spherical copper powder produced by Zeuzu New Material science and technology Limited, Hunan Tan City, and the specific surface area is 1.0-5.0m2The grain size D50 is less than or equal to 5 mu m.
TABLE 10 copper paste formulations
Name of Material
Producing area
Mass percent
Organic vehicle
Self-made
6.5％
Glass powder
Made in China
0.5％
Copper powder
Self-made
85％
Glycerol phosphate ester
An inlet
2.0％
Mineral oil extract
An inlet
6.0％
TABLE 11 glass powder formulations
Name of Material
Mass percent
B2O3
32％
SiO2
28％
ZnO
20％
Al2O3
16％
Ag2O
1.5％
ZrO2
1.5％
NbO
1.0％
The copper powder obtained in the embodiment is printed at two ends of a chip (0603 specification) by adopting a screen printing mode, and is dried and sintered to form end electrodes, so that the MLCC is obtained. The copper paste of this example and the resulting MLCC performance are shown in Table 12.
TABLE 12 copper paste and MLCC Performance
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.