Method for producing conductive paste, conductive paste, and method for producing multilayer ceramic capacitor

Abstract

Provided are: a method for producing a conductive paste which is capable of improving dry film strength of a thinned external electrode; a conductive paste; and a method for producing a multilayer ceramic capacitor, with which it is possible to improve dry film strength of a thinned external electrode by using the conductive paste.　The method for producing a conductive paste according to the present invention is for the production of a conductive paste for forming an external electrode in a multilayer ceramic capacitor. The production method comprises: a step for mixing a copper powder, a glass powder, an acrylic resin that has a weight average molecular weight of 700,000 or less and a polydispersity (Mw / Mn) of 3.5 or more, and a solvent; and a step for applying a physical load to the mixture, whereby the weight average molecular weight of the acrylic resin is 100,000 to 300,000 inclusive and the polydispersity (Mw / Mn) of the acrylic resin is 2.0 to 4.0 inclusive. In the method for producing a multilayer ceramic capacitor according to the present invention, an external electrode is formed using a conductive paste that is produced by the method for producing a conductive paste according to the present invention.

Description

Method for manufacturing conductive paste, conductive paste, and method for manufacturing multilayer ceramic capacitors

[0001] The present invention relates to a method for manufacturing a conductive paste, a conductive paste, and a method for manufacturing a multilayer ceramic capacitor.

[0002] Multilayer ceramic capacitors are expected to see a significant increase in demand in the communications and automotive sectors, requiring diverse performance characteristics such as miniaturization, high capacitance, high reliability, and multi-terminal capabilities. To reduce the external dimensions of chip-type ceramic electronic components, one effective method is to thin the external electrodes formed on the outer surface of the component body. To obtain highly dense external electrodes with few defects and voids while maintaining thinness, it is necessary to finely atomize the copper powder and glass powder contained in the conductive paste by baking.

[0003] Patent Document 1 describes that by using fine powders with a glass powder particle size of 0.8 μm or less and copper powder with a particle size of 1.0 μm or less, a dense external electrode can be formed after firing.

[0004] Japanese Patent Publication No. 2018-181672

[0005] On the other hand, if the inorganic powder particles contained in the conductive paste are 1.0 μm or smaller, the film strength of the dried coating decreases. Furthermore, as the thickness of the external electrodes decreases, the dried film may not withstand the impact between chips during the transport process after drying, particularly at the corners of chip-type ceramic electronic components, resulting in chipping or peeling of the dried film. Therefore, improvement in the strength of the dried film is desired.

[0006] Therefore, the main object of this invention is to provide a method for manufacturing a conductive paste and a conductive paste that can improve the dry film strength of a thin-film external electrode. Furthermore, it is also to provide a method for manufacturing a multilayer ceramic capacitor using the conductive paste.

[0007] The present invention relates to a method for manufacturing a conductive paste for forming external electrodes in a multilayer ceramic capacitor, comprising the steps of: mixing copper powder, glass powder, an acrylic resin having a weight-average molecular weight of 700,000 or less and a polydispersity (Mw / Mn) of 3.5 or more, and a solvent; and applying a physical load to the mixture to make the weight-average molecular weight of the acrylic resin 100,000 to 300,000 and the polydispersity (Mw / Mn) 2.0 to 4.0. Furthermore, the present invention relates to a conductive paste containing copper powder, glass powder, an acrylic resin, and a solvent, wherein the acrylic resin has a weight-average molecular weight of 100,000 to 300,000 and a polydispersity (Mw / Mn) of 2.0 to 4.0. Furthermore, the method for manufacturing a multilayer ceramic capacitor according to this invention comprises the steps of: preparing a laminate; applying a conductive paste manufactured by the conductive paste manufacturing method according to this invention to the outer surface of the laminate; and forming external electrodes by baking the applied conductive paste.

[0008] In the conductive paste and method for manufacturing the same according to this invention, in the dispersion step of paste formation, the molecular weight distribution of the resin in the conductive paste is narrowed while setting the weight-average molecular weight to 100,000 to 300,000 so as not to decrease the dry film strength, and the polydispersity (Mw / Mn) to 2.0 to 4.0, thereby obtaining a conductive paste and method for manufacturing the same that can form external electrodes with improved dry film strength even when thinned. Furthermore, in the method for manufacturing a multilayer ceramic capacitor according to this invention, since external electrodes with improved dry film strength can be formed even when thinned, a highly reliable multilayer ceramic capacitor can be obtained.

[0009] According to the present invention, a method for manufacturing a conductive paste that can improve the dry film strength of a thin-film external electrode, and a conductive paste can be obtained. Furthermore, a method for manufacturing a multilayer ceramic capacitor using the conductive paste can be provided.

[0010] The above-mentioned objectives, other objectives, features, and advantages of this invention will become even clearer from the following description of embodiments for carrying out the invention, with reference to the drawings.

[0011] This is an external perspective view of a multilayer ceramic capacitor, which is an example of a ceramic electronic component according to the present invention. This is a cross-sectional view taken along line II-II shown in Figure 1.

[0012] An embodiment of a conductive paste according to the present invention and a multilayer ceramic capacitor in which external electrodes are formed using the conductive paste will be described along with its manufacturing method.

[0013] 1. Conductive Paste The conductive paste according to the present invention comprises conductive metal powder, glass powder, acrylic resin, and solvent.

[0014] The conductive metal powder is copper powder.

[0015] 50% weight cumulative particle size (D) of copper powder by laser diffraction scattering particle size distribution measurement method 50 The particle size (D) is preferably 1.0 μm or less, and more preferably 0.80 μm or less. Furthermore, the 50% weight cumulative particle size (D) of the copper powder measured by laser diffraction scattering particle size distribution analysis is also determined. 50 It is more preferable that the particle size is 0.50 μm or less. There is no lower limit, but it may be 0.05 μm or more, 0.10 μm or more, or 0.20 μm or more.

[0016] The glass powder is preferably made of B-Si glass. In this case, the B-Si glass may contain Ba (barium) or Sr (strontium) as additive elements.

[0017] The BET specific surface area of ​​glass powder is 8.2 m². 2 It is preferable that the amount is 1 / g or more. Furthermore, the BET specific surface area of ​​the glass powder is 9.8 m². 2 A value of 150 m is preferable, and there is no upper limit, but for example, 150 m 2 It may be less than / g, and 100m 2It may be less than or equal to / g. By setting the BET specific surface area within this range, the external electrodes formed by this conductive paste can be densely packed into a thin film. The BET specific surface area is measured by the BET method.

[0018] 50% weight cumulative particle size (D) of glass powder by laser diffraction scattering particle size distribution measurement method 50 The particle size (D) is preferably 1.0 μm or less. Furthermore, the 50% weight cumulative particle size (D) of the glass powder measured by laser diffraction scattering particle size distribution analysis is also specified. 50 It is more preferable that the particle size is 0.80 μm or less. There is no lower limit, but for example, it may be 0.05 μm or more, or 0.10 μm or more.

[0019] The acrylic resin contained in the conductive paste according to the present invention has a weight-average molecular weight of 100,000 to 300,000. Furthermore, the weight-average molecular weight of the acrylic resin is more preferably 200,000 to 300,000. In addition, the polydispersity (Mw / Mn) of the acrylic resin is 2.0 to 4.0. By setting the weight-average molecular weight of the acrylic resin to 100,000 or more, the entanglement of the resin in the conductive paste can be increased, and the film strength can be improved. Note that, due to shear during paste formation, if the weight-average molecular weight of the acrylic resin contained in this conductive paste exceeds 300,000, stringiness becomes stronger, leading to abnormal film shape (horn shape).

[0020] The weight-average molecular weight of the acrylic resin is measured by gel permeation chromatography (GPC). Specifically, the measurement can be performed by dissolving the sample in tetrahydrofuran and comparing the time it takes to pass through the cell with the time taken for resins with known molecular weights. Monodisperse polystyrene is used as the standard sample.

[0021] The resin content ratio of the acrylic resin in this conductive paste is preferably 5 vol% to 15 vol%.

[0022] Furthermore, the PVC content is preferably between 50% and 70%. Here, PVC (Pigment Volume Concentration) refers to the pigment volume concentration, which is the volume ratio of pigment to the solid components in the ink. Specifically, ink (paste) contains pigment (metal powder or glass in paste), binder, and solvent. When considering the state after the solvent has been removed (dry film), the volume ratio of pigment / (pigment + binder) is called PVC. In other words, it represents the proportion of inorganic components in the volume of the dry film.

[0023] The volume of glass powder relative to the conductive metal powder is preferably 10% to 25%.

[0024] It is preferable to use an alcohol-based solvent such as terpineol as the solvent.

[0025] Generally, it is known that increasing the weight-average molecular weight of an acrylic resin also increases the polydispersity, which indicates the molecular weight distribution. When an acrylic resin with a large molecular weight distribution is used in a conductive paste, the resin distribution within the dried film may become non-uniform, leading to a decrease in the strength of the dried film. According to the conductive paste of the present invention, by setting the weight-average molecular weight to 100,000 to 300,000, and the polydispersity (Mw / Mn) to 2.0 to 4.0, it is possible to form an external electrode with improved dried film strength even when thinned.

[0026] 2. Multilayer Ceramic Capacitors Next, a multilayer ceramic capacitor will be described as an example of a ceramic electronic component having external electrodes formed using the conductive paste according to the present invention. Figure 1 is an external perspective view of a multilayer ceramic capacitor, which is an example of a ceramic electronic component according to the present invention. Figure 2 is a cross-sectional view taken along line II-II shown in Figure 1.

[0027] As shown in Figure 1, the multilayer ceramic capacitor 10 includes a rectangular parallelepiped-shaped laminate 12.

[0028] The laminate 12 has a plurality of stacked dielectric layers 14 and a plurality of internal electrode layers 16. Furthermore, the laminate 12 has a first main surface 12a and a second main surface 12b opposite to the height direction x, a first side surface 12c and a second side surface 12d opposite to the width direction y which is perpendicular to the height direction x, and a first end surface 12e and a second end surface 12f opposite to the length direction z which is perpendicular to the height direction x and the width direction y. The corners and edges of this laminate 12 are rounded. A corner is the part where three adjacent surfaces of the laminate intersect, and an edge is the part where two adjacent surfaces of the laminate intersect.

[0029] The laminate 12 includes an outer layer 14a composed of multiple dielectric layers 14 and an inner layer 14b composed of one or more dielectric layers 14 and multiple internal electrode layers 16 arranged on them. The outer layer 14a is located on the first main surface 12a side and the second main surface 12b side of the laminate 12, and is an aggregate of multiple dielectric layers 14 located between the first main surface 12a and the internal electrode layer 16 closest to the first main surface 12a, and multiple dielectric layers 14 located between the second main surface 12b and the internal electrode layer 16 closest to the second main surface 12b. The region sandwiched between the two outer layer portions 14a is the inner layer portion 14b.

[0030] The dielectric layer 14 can be formed from, for example, a dielectric material. Such dielectric materials include, for example, dielectric ceramics containing components such as BaTiO3 (barium titanate), CaTiO3 (calcium titanate), SrTiO3 (strontium titanate), or CaZrO3 (calcium zirconate). When the above dielectric material is the main component, depending on the desired properties of the laminate 12, a mixture containing less of a secondary component than the main component, such as a Mn (manganese) compound, Fe (iron) compound, Cr (chromium) compound, Co (cobalt) compound, or Ni (nickel) compound, may be used.

[0031] The laminate 12 has multiple internal electrode layers 16, for example, multiple substantially rectangular first internal electrode layers 16a and multiple second internal electrode layers 16b. The multiple first internal electrode layers 16a and the multiple second internal electrode layers 16b are embedded so as to be alternately arranged at equal intervals along the height direction x of the laminate 12.

[0032] The first internal electrode layer 16a faces the second internal electrode layer 16b via a dielectric layer 14, and its end is drawn out and exposed at the first end face 12e. The second internal electrode layer 16b faces the first internal electrode layer 16a via a dielectric layer 14, and its end is drawn out and exposed at the second end face 12f.

[0033] The internal electrode layer 16 contains a suitable conductive material, such as metals like Ni (nickel), Cu (copper), Ag (silver), Pd (palladium), and Au (gold), or alloys containing at least one of these metals, such as an Ag-Pd alloy. The resin component used in the conductive paste for the internal electrode to form the internal electrode layer 16 is preferably ethyl cellulose or acrylic resin.

[0034] External electrodes 20 are arranged on the first end face 12e and the second end face 12f of the laminate 12. The external electrodes 20 have a first external electrode 20a and a second external electrode 20b.

[0035] The first external electrode 20a is positioned on the surface of the first end face 12e of the laminate 12 and is formed to extend from the first end face 12e and cover a portion of each of the first main surface 12a, the second main surface 12b, the first side surface 12c, and the second side surface 12d. In this case, the first external electrode 20a is electrically connected to the first internal electrode layer 16a. The second external electrode 20b is positioned on the surface of the second end face 12f of the laminate 12 and is formed to extend from the second end face 12f and cover a portion of each of the first main surface 12a, the second main surface 12b, the first side surface 12c, and the second side surface 12d. In this case, the second external electrode 20b is electrically connected to the second internal electrode layer 16b.

[0036] In the multilayer body 12, a capacitance is formed by the first internal electrode layer 16a and the second internal electrode layer 16b opposing each other with the dielectric layer 14 interposed therebetween. Therefore, a capacitance can be obtained between the first external electrode 20a connected to the first internal electrode layer 16a and the second external electrode 20b connected to the second internal electrode layer 16b, and the characteristics of a capacitor are exhibited.

[0037] The first external electrode 20a and the second external electrode 20b each include a base electrode layer 22 containing a conductive metal and a glass component, and a plating layer 24 disposed so as to cover the base electrode layer 22.

[0038] The base electrode layer 22 includes a first base electrode layer 22a and a second base electrode layer 22b.

[0039] The first base electrode layer 22a is disposed on the surface of the first end face 12e of the multilayer body 12, and is formed to extend from the first end face 12e and cover a part of each of the first main surface 12a, the second main surface 12b, the first side surface 12c, and the second side surface 12d. The second base electrode layer 22b is disposed on the surface of the second end face 12f of the multilayer body 12, and is formed to extend from the second end face 12f and cover a part of each of the first main surface 12a, the second main surface 12b, the first side surface 12c, and the second side surface 12d.

[0040] The base electrode layer 22 contains a conductive metal and a glass component. The conductive metal of the base electrode layer 22 contains, for example, copper. Further, the glass component of the base electrode layer 22 is preferably made of B-Si-based glass. In this case, the B-Si-based glass may contain Ba (barium) or Sr (strontium) as an additive element. The base electrode layer 22 may be a plurality of layers. The base electrode layer 22 is obtained by applying a conductive paste containing glass and a metal onto the multilayer body 12 and baking the paste, and may be fired simultaneously with the dielectric layer 14 and the internal electrode layers 16, or may be baked after firing the dielectric layer 14 and the internal electrode layers 16.

[0041] The plating layer 24 includes a first plating layer 24a and a second plating layer 24b.

[0042] The first plating layer 24a is arranged to cover the first base electrode layer 22a. Specifically, it is preferable that the first plating layer 24a is placed on the first end face 12e of the surface of the first base electrode layer 22a and extends to the first main surface 12a, the second main surface 12b, the first side surface 12c, and the second side surface 12d of the surface of the first base electrode layer 22a. The second plating layer 24b is arranged to cover the second base electrode layer 22b. Specifically, it is preferable that the second plating layer 24b is placed on the second end face 12f of the surface of the second base electrode layer 22b and extends to the first main surface 12a, the second main surface 12b, the first side surface 12c, and the second side surface 12d of the surface of the second base electrode layer 22b.

[0043] The plating layer 24 includes, for example, at least one selected from Cu (copper), Ni (nickel), Sn (tin), Ag (silver), Pd (palladium), Ag-Pd alloy, Au (gold), etc. The plating layer 24 may be formed by multiple layers. In this case, the plating layer 24 preferably has a two-layer structure consisting of a Ni plating layer and a Sn plating layer. The Ni plating layer is provided so as to cover the surface of the under electrode layer 22, thereby providing solder barrier performance. Furthermore, by providing the Sn plating layer on the surface of the Ni plating layer, the wettability of the solder used for mounting the multilayer ceramic capacitor 10 is improved, making mounting easier.

[0044] With the multilayer ceramic capacitor 10 having the above configuration, the base electrode layer 22 is formed by the conductive paste according to the present invention, so even if the thinning is reduced, a highly reliable multilayer ceramic capacitor 10 with improved strength of the external electrodes can be obtained.

[0045] 3. Manufacturing Method of Multilayer Ceramic Capacitors Next, the manufacturing method of the multilayer ceramic capacitor 10 described above will be explained.

[0046] (Preparation of ceramic green sheets) First, a dielectric ceramic containing components such as BaTiO3 (barium titanate), CaTiO3 (calcium titanate), SrTiO3 (strontium titanate), or CaZrO3 (calcium zirconate) is prepared as a dielectric material. A dielectric powder obtained from this dielectric material is mixed with an organic binder, an organic solvent, a plasticizer, and a dispersant in predetermined proportions to produce a ceramic slurry. This ceramic slurry is then molded onto a resin film into an inner or outer layer ceramic green sheet.

[0047] Next, a conductive paste for forming internal electrodes is prepared, and the conductive paste for forming internal electrodes is applied to the ceramic green sheet in a predetermined pattern, for example, by screen printing or gravure printing, thereby preparing an inner layer ceramic green sheet with a conductive pattern for forming internal electrodes and an outer layer ceramic green sheet without a conductive pattern for forming internal electrodes.

[0048] Furthermore, the ceramic slurry and the conductive paste for forming internal electrodes may contain, for example, known organic binders and solvents. The conductive paste for forming internal electrodes may, for example, be a mixture of metal powder, an organic binder, and an organic solvent.

[0049] Next, multiple ceramic green sheets for the inner layer are stacked so that the ends of the conductive paste film are drawn in alternating directions. Furthermore, layers of ceramic green sheets for the outer layer are stacked above and below the stacked ceramic green sheets for the inner layer. In other words, multiple layers of ceramic green sheets for the outer layer, made of the same material as the ceramic green sheets for the inner layer, are stacked and pressed together to form a laminated block. This laminated block is then cut into predetermined product sizes to obtain an unfired laminated body 12.

[0050] Next, the separated, unfired laminated body 12 is fired to become a sintered laminated body 12.

[0051] The inner and outer ceramic green sheets and the conductive paste film are fired simultaneously, with the inner ceramic green sheet becoming the inner layer portion 14b, the outer ceramic green sheet becoming the outer layer portion 14a, and the conductive paste film becoming the internal electrode layer 16.

[0052] (Preparation of conductive paste) Next, a conductive paste is prepared to form the base electrode layer for the external electrode.

[0053] First, conductive metal powder, glass powder, acrylic resin, and a solvent are prepared to manufacture the conductive paste for the base electrode layer.

[0054] For the conductive metal powder, copper powder is prepared.

[0055] The glass powder is preferably made of B-Si glass. In this case, the B-Si glass may contain Ba (barium) or Sr (strontium) as additive elements.

[0056] The acrylic resin prepared has a weight-average molecular weight of 700,000 or less. Furthermore, the polydispersity (Mw / Mn) of the acrylic resin is 3.5 or higher. If the weight-average molecular weight of the acrylic resin exceeds 700,000, it becomes stringy and gel-like, which negatively impacts the workability of the mixing and dispersion process for paste formation.

[0057] It is preferable to use an alcohol-based solvent such as terpineol as the solvent.

[0058] Next, the prepared copper powder, glass powder, acrylic resin, and solvent are blended, mixed, and then dispersed to produce a conductive paste. A planetary mill or similar can be used in this mixing process, and a three-roll mill, bead mill, or similar can be used in the dispersion process. In this dispersion process for paste formation, a physical load, such as shearing, is applied to the acrylic resin so that its weight-average molecular weight is between 100,000 and 300,000, and its polydispersity (Mw / Mn) is between 2.0 and 4.0. If the polydispersity (Mw / Mn) of the acrylic resin contained in the conductive paste is greater than 4.0, the resin distribution in the dried film becomes non-uniform, which leads to a problem of reduced film strength.

[0059] The weight-average molecular weight of the prepared acrylic resin and the weight-average molecular weight of the acrylic resin after the mixing step were measured by gel permeation chromatography (GPC). Specifically, the measurement can be performed by dissolving the sample in tetrahydrofuran and comparing the time it takes to pass through the cell with the time taken for resins with known molecular weights. Monodisperse polystyrene is used as the standard sample.

[0060] In this manner, a conductive paste for the base electrode layer is manufactured.

[0061] The method for manufacturing a conductive paste according to this invention includes the steps of: mixing copper powder, glass powder, an acrylic resin having a weight-average molecular weight of 700,000 or less and a polydispersity (Mw / Mn) of 3.5 or more with a solvent; and in the dispersion step during paste formation, applying a physical load to the mixture to the extent that the molecular weight of the resin in the conductive paste is narrowed while the dry film strength is not reduced, thereby making the weight-average molecular weight of the acrylic resin between 100,000 and 300,000 and the polydispersity (Mw / Mn) between 2.0 and 4.0. As a result, a conductive paste can be obtained that can form an external electrode with improved dry film strength even when thinned.

[0062] (Formation of External Electrodes) Next, external electrodes 20 are formed on both ends of the sintered multilayer body 12 using the respective conductive pastes. First, a conductive paste for a base electrode containing copper as a main component is applied to both ends of the multilayer body 12 by, for example, a dipping method, baked, and the base electrode layer 22 electrically connected to the internal electrode layers 16 is formed.

[0063] Subsequently, the conductive paste according to the present invention is applied to the surface of the base electrode layer 22 and baked, and Ni plating and Sn plating are performed so as to cover the surface of the base electrode layer 22, whereby the plating layer 24 is formed.

[0064] As described above, the desired multilayer ceramic capacitor 10 is manufactured.

[0065] 4. Experimental Example Next, in accordance with the above-described method for manufacturing a multilayer ceramic capacitor, a sample multilayer ceramic capacitor was manufactured. An experiment was conducted to evaluate the dried film strength and abnormal film shape of an external electrode (base electrode layer) formed from a conductive paste manufactured based on the materials shown in Table 1.

[0066] (a) Samples used in the experimental example Specifications of the multilayer ceramic capacitor, which is the sample used in the experimental example, are as follows. - Size (design value) of the multilayer ceramic capacitor: length × width × height = 0.6 mm × 0.3 mm × 0.3 mm - Material of dielectric layers: barium titanate - Structure of external electrodes The conductive paste shown in Table 1 was used as the material for the base electrode layer. No plating layer was formed. The glass powder was B-Si-Ba based glass.

[0067] In each sample, copper powder, glass powder, acrylic resin, and solvent were blended so as to be 50 wt%, 5 wt%, 5 wt%, and 40 wt%, respectively. D of copper powder as conductive powder contained in the conductive paste for a base electrode layer 50 were prepared with particle sizes of 0.32 μm and 0.54 μm. The BET specific surface area of the glass powder contained in the conductive paste for a base electrode layer is 8.2 m 2 / g or more and 10.2 m 2 / g was prepared.

[0068] The weight-average molecular weights of the individual acrylic resins prepared and the acrylic resins in the conductive paste after mixing, as shown in Table 1, were measured by gel permeation chromatography (GPC). Specifically, the measurement was performed by dissolving the sample in tetrahydrofuran and evaluating the time it took for the sample to pass through the cell, comparing it to the passage time of resins with known molecular weights. Monodisperse polystyrene was used as the standard sample.

[0069] (b) Dry Film Strength Test Mechanical vibration was applied to each sample of Examples 1 to 4 and Comparative Examples 1 to 3, and then the appearance was observed using a metallurgical microscope to check for the presence or absence of chipping or peeling in the dried film. The drying conditions were 100°C for a drying time of 15 minutes. A vibration device (Westec Co., Ltd., model number: MRV-MINI-M) was used to vibrate each sample. The vibration frequency was set to 50 Hz and the vibration was applied for 1 minute in an environment of 25°C. Samples without chipping or peeling were judged as good ("○"), and those with chipping or peeling were judged as defective ("×"). The number of samples for each of Examples 1 to 4 and Comparative Examples 1 to 3 was 100.

[0070] (c) Confirmation test for abnormal film shape Each sample from Examples 1 to 4 and Comparative Examples 1 to 3 was observed using a metallurgical microscope to check for abnormal film shape (horn shape) at the end faces of the dried film. Samples without abnormal film shape were judged as good ("○"), and those with abnormal film shape were judged as defective ("×"). The number of samples for each of Examples 1 to 4 and Comparative Examples 1 to 3 was 100.

[0071] Table 1 shows the copper particle size (D) contained in the conductive metal powder in each sample of Examples 1 to 4 and Comparative Examples 1 to 3. 50Table 1 shows the BET specific surface area of ​​the glass powder, the weight-average molecular weight of the prepared acrylic resin alone, the polydispersity (Mw / Mn) of the acrylic resin alone, the weight-average molecular weight of the acrylic resin in the conductive paste, and the polydispersity (Mw / Mn) of the acrylic resin in the conductive paste. Table 1 also shows the results of the determination of the dry film strength, the determination of abnormal film shape, and the overall evaluation for each sample in Examples 1 to 4 and Comparative Examples 1 to 3.

[0072]

[0073] According to Table 1, in each sample from Example 1 to Example 4, the copper particle size (D 50 The particle size (D) was 1.0 μm or less, the weight-average molecular weight of the acrylic resin in the conductive paste was between 100,000 and 300,000, and the polydispersity (Mw / Mn) was between 2.0 and 4.0. As a result, both the dry film strength determination result and the film shape abnormality determination result were good, and a good overall evaluation result was obtained. Furthermore, in each sample from Example 1 to Example 4, the copper particle size (D) was 50 The surface area is 0.80 μm or less, and the BET specific surface area of ​​the glass powder is 8.2 m². 2 It was confirmed that the overall evaluation was good even when the value was above / g.

[0074] On the other hand, in the sample of Comparative Example 1, the weight-average molecular weight of the acrylic resin in the conductive paste was less than 100,000, so the dry film strength was judged to be poor. At this time, it is thought that the polydispersity (Mw / Mn) of the prepared acrylic resin alone being less than 3.5 also had an effect. In Comparative Example 2, the weight-average molecular weight of the acrylic resin in the conductive paste was greater than 300,000 and the polydispersity (Mw / Mn) was less than 2.0, so the film shape abnormality was judged to be poor. At this time, it is thought that the weight-average molecular weight of the prepared acrylic resin alone being greater than 700,000 and the polydispersity (Mw / Mn) being less than 3.5 also had an effect. In Comparative Example 3, the polydispersity (Mw / Mn) of the acrylic resin in the conductive paste was greater than 4.0, so the dry film strength was judged to be poor.

[0075] From the above results, in each sample from Example 1 to Example 4, the copper particle size (D50 It was confirmed that a substrate electrode layer with good results in both dry film strength and film shape abnormality can be obtained when the ) is 1.0 μm or less, the weight-average molecular weight of the acrylic resin in the conductive paste is 100,000 to 300,000, and the polydispersity (Mw / Mn) is 2.0 to 4.0. Furthermore, it was confirmed that the conductive paste of the present invention can be obtained when the weight-average molecular weight of the prepared acrylic resin alone is 700,000 or less, and its polydispersity (Mw / Mn) is 3.5 or higher.

[0076] As described above, embodiments of the present invention are disclosed in the above description, but the present invention is not limited thereto. That is, without departing from the scope of the technical idea and objectives of the present invention, various modifications can be made to the embodiments described above in terms of mechanism, shape, material, quantity, position or arrangement, etc., and these are included in the present invention.

[0077] 10 Multilayer ceramic capacitor 12 Laminate 12a First main surface 12b Second main surface 12c First side surface 12d Second side surface 12e First end surface 12f Second end surface 14 Dielectric layer 14a Outer layer 14b Inner layer 16 Internal electrode layer 16a First internal electrode layer 16b Second internal electrode layer 20 External electrode 20a First external electrode 20b Second external electrode 22 Underlay electrode layer 22a First underlay electrode layer 22b Second underlay electrode layer 24 Plating layer 24a First plating layer 24b Second plating layer x Height direction y Width direction z Length direction

Claims

1. A method for manufacturing a conductive paste for forming external electrodes in a multilayer ceramic capacitor, comprising: a step of mixing copper powder, glass powder, an acrylic resin having a weight-average molecular weight of 700,000 or less and a polydispersity (Mw / Mn) of 3.5 or more, and a solvent; and a step of applying a physical load to the mixture to make the weight-average molecular weight of the acrylic resin 100,000 or more and 300,000 or less and a polydispersity (Mw / Mn) of 2.0 or more and 4.0 or less.

2. The method for producing a conductive paste according to claim 1, wherein the 50% weight cumulative particle size of the copper powder measured by laser diffraction scattering particle size distribution analysis is 0.80 μm or less.

3. The BET specific surface area of ​​the glass powder is 8.2 m². 2 A method for producing a conductive paste according to claim 1 or claim 2, wherein the amount is 1g or more.

4. A conductive paste containing copper powder, glass powder, an acrylic resin, and a solvent, wherein the acrylic resin has a weight-average molecular weight of 100,000 or more and 300,000 or less and a polydispersity (Mw / Mn) of 2.0 or more and 4.0 or less.

5. The conductive paste according to claim 4, wherein the 50% weight cumulative particle size of the copper powder measured by laser diffraction scattering particle size distribution analysis is 0.80 μm or less.

6. The BET specific surface area of ​​the glass powder is 8.2 m². 2 A conductive paste according to claim 4 or claim 5, wherein the amount is 1 / g or more.

7. A method for manufacturing a multilayer ceramic capacitor, comprising: a step of preparing a laminate; a step of applying a conductive paste manufactured by the conductive paste manufacturing method described in any one of claims 1 to 3 to the outer surface of the laminate; and a step of forming an external electrode by baking the applied conductive paste.

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