JP2006269875A - Method of manufacturing ceramic electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly dispersed ceramic sheet while holding a compression margin at laminating to manufacture a high density laminate, thus obtaining a laminated ceramic capacitor having a low short-circuit ratio and a high breakdown voltage. <P>SOLUTION: The manufacturing method comprises a first step of dispersing an inorganic powder, a plasticizer, and an organic solvent to prepare a first slurry; a second step of dispersing an organic binder in the first slurry to prepare a second slurry; a third step of forming a ceramic sheet 11 from the second slurry; a fourth step of laminating the ceramic sheets 11 and inner electrodes alternately to make a laminate; and a fifth step of baking the laminate. In the second step, the organic binder is added and molten, and then water is added 1.5 wt.% or less (0 wt.% excluded) to the inorganic powder 100 wt.%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a ceramic electronic component such as a multilayer ceramic capacitor.

  A conventional method for manufacturing a multilayer ceramic electronic component will be described by taking a multilayer ceramic capacitor as an example.

  FIG. 4 is a partially cutaway perspective view of a general multilayer ceramic capacitor 41, in which dielectric layers 42 and internal electrodes 43 are alternately stacked to form a multilayer body, and the end surface of the internal electrode 43 has a multilayer body. Are stacked so as to be alternately exposed at both opposite end faces, and are alternately connected to a pair of external electrodes 44 formed on both end faces of the laminate.

  A conventional method for manufacturing a multilayer ceramic capacitor will be described below.

  First, an organic binder, a plasticizer, an organic solvent, etc. are added to the inorganic powder which has barium titanate as a main component, and a slurry is produced.

  Next, a ceramic sheet that becomes the dielectric layer 42 after firing is produced by the doctor blade method using this slurry.

  Next, a metal paste containing Ni as a main component is printed on the ceramic sheet to form a conductor layer that becomes the internal electrode 43 after firing.

  Thereafter, a predetermined number of the ceramic sheets with the conductor layer are laminated, and after firing, the external electrode 44 is formed to obtain the multilayer ceramic capacitor shown in FIG.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP 2001-213669 A

  However, in the above conventional method, when the ceramic sheet is a thin-film ceramic sheet that is extremely thin, in order to prevent the generation of defects when forming the ceramic sheet and improving the handling of the ceramic sheet during lamination, The dispersion of powder and organic binder should be strengthened.

  However, simply strengthening the dispersion reduces the compression margin of the ceramic sheet during lamination, which may lead to defects in the laminate.

  Further, in such dispersion, dispersion proceeds while some particles remain aggregated, and the aggregate remains in the slurry. When the ceramic sheet is formed, the aggregates in the laminate cause defects in the laminate. Therefore, there is a problem that the short-circuit rate is high and the breakdown voltage characteristics are liable to be lowered. Therefore, an object of the present invention is to provide a ceramic electronic component having a low short-circuit rate and improved breakdown voltage characteristics.

  In order to achieve this object, the present invention has the following configuration.

  The invention according to claim 1 of the present invention includes a first step in which at least an inorganic powder, a plasticizer, and an organic solvent are dispersed to produce a first slurry, and an organic binder is dispersed in the first slurry. A second step of producing a second slurry, a third step of producing a ceramic sheet from the second slurry, and a fourth step of producing a laminate by alternately laminating the ceramic sheet and internal electrodes. And a fifth step of firing the laminate, and after adding and dissolving an organic binder in the second step, 1.5 wt% or less (excluding 0 wt%) with respect to 100 wt% of the inorganic powder ) Is a method for producing ceramic electronic parts, and by forming a weak cohesive state in the slurry and ceramic sheet, a dense laminate can be obtained after lamination, resulting in a low short-circuit rate and failure. It is possible to obtain a ceramic electronic component pressure characteristics are improved.

  In addition, by controlling the average particle diameter (D50) and specific surface area of the inorganic powder before and after dispersion, a denser laminate can be obtained by realizing an optimal aggregation state of the inorganic powder. A ceramic electronic component having low breakdown voltage characteristics and improved characteristics can be obtained.

  Here, (D50) is the particle size corresponding to 50% of the total particle size distribution curve when the cumulative particle size distribution curve is prepared, and is used as the average particle size of the powder having a certain particle size distribution. There are many cases.

  According to the present invention, an inorganic powder, a plasticizer, and an organic solvent are dispersed to produce a first slurry, and an organic binder is dispersed in the first slurry to produce a second slurry. After adding and dissolving, weakly aggregated state in the ceramic sheet produced using this second slurry by adding water of 1.5 wt% or less (excluding 0 wt%) to 100 wt% of the inorganic powder When a laminated body is produced by alternately laminating the ceramic sheets and the internal electrodes, a dense laminated body can be obtained, so that a ceramic electronic component having a low short-circuit rate and improved breakdown voltage characteristics can be obtained. Can do.

  Hereinafter, the multilayer ceramic electronic component of the present invention will be described with reference to an embodiment of the present invention and FIGS.

  FIG. 1 is a partially enlarged cross-sectional view of a ceramic sheet 11 of the multilayer ceramic capacitor according to the present embodiment, and shows a state in which inorganic powder particles 12 are dispersed in the ceramic sheet 11 in a weakly aggregated state. In FIG. 1, the part other than the inorganic powder particles 12 is a vehicle 13 composed of an organic binder, a plasticizer, an organic solvent, water, and the like.

  FIG. 2 is a cross-sectional view schematically showing a densified state when the ceramic sheet 11 of FIG. 1 is pressed. The pressed ceramic sheet 15 has a vehicle 13 when the inorganic powder particles 12 are pressed. It shows that it is aligned inside and is in a high filling state.

  FIG. 3 shows a state in which the laminated body 14 having a high filling degree is produced by alternately laminating the pressed ceramic sheets 15 and the internal electrodes 43 shown in FIG.

  Below, the manufacturing method of such a laminated body 14 is demonstrated in detail.

First, as an inorganic powder, water is added to and mixed with ceramic raw material powder made of additives such as barium titanate as a main component, rare earth oxide, and MgO, MnO ₂ , V ₂ O ₅ .

  The mixture is then filtered to dehydrate and then dried in a dryer.

  At this time, the inorganic powder is dried so as to prevent aggregation of the inorganic powder as much as possible.

  Thereafter, the dried inorganic powder is put into a high-purity alumina crucible and calcined at a predetermined temperature. The calcination temperature and time are determined, for example, in the range of 800 ° C. to 1000 ° C. for several hours depending on the composition of the ceramic raw material powder.

  Next, after calcination of the inorganic powder after calcination, 60% of an organic solvent made of butyl acetate and 3 wt% of a plasticizer made of benzyl butyl phthalate were mixed with 100 wt% of the pulverized inorganic powder. (1st process). Next, 9% of an organic binder made of polyvinyl butyral resin is mixed with 100% by weight of the pulverized inorganic powder to the first slurry to produce a second slurry by mixing 1.5% by weight or less of water (first slurry). Step 2).

  The method for producing the second slurry will be described in more detail below.

  First, after sufficiently premixing an organic solvent composed of butyl acetate, a plasticizer composed of benzyl butyl phthalate, and a pulverized inorganic powder, there is no aggregate using a medium stirring mill or the like. The value B of the average particle diameter (D50) is in the range of 0.8A ≦ B ≦ 1.0A with respect to the value A of the average particle diameter (D50) before dispersion, and the specific surface area Sb after dispersion is before dispersion. Then, the organic binder made of polyvinyl butyral resin is added and dissolved, and then water at room temperature is added and further stirred with a medium stirring mill.

  Here, when the value of B is less than 0.8 A, the dispersion proceeds too much and the powder in the second slurry becomes excessively pulverized, and the possibility that the specific surface area Sb after the dispersion exceeds 1.5 Sa increases. When the specific surface area Sb after dispersion exceeds 1.5 Sa, fine particles are formed more than necessary, and the fine particles are aggregated, so that the aggregated particles having strong cohesive force can be excessive. As a result, the dispersion state becomes non-uniform and defects are generated during lamination, resulting in a high occurrence of a short-circuit rate after sintering. Therefore, the specific surface area Sb after dispersion must be 1.5 Sa or less, and in order to make the specific surface area Sb after dispersion 1.5 Sa or less, the value of B should be 0.8 A or more. is necessary.

  Further, when the particle diameter exceeds 1.0 A, the dispersion becomes inadequate, resulting in large particles due to insufficient dispersion, which also causes defects during lamination, and the occurrence of a short ratio after sintering is high. This is not preferable.

  The specific surface area value was measured by a commonly used BET method.

  The average particle size (D50) was measured using a laser diffraction type particle size distribution meter.

  It is important to add water after dissolving the organic binder.

  If water is added in a state where no organic binder is contained, water is bound to the inorganic powder first, so that a sufficient dispersed state of the inorganic powder cannot be obtained.

  The second slurry thus produced has a different fluidity from the conventional slurry and has a weak flocculation structure. In the first step of dispersing the solvent and the inorganic powder, a better dispersion state may be obtained by adding a dispersant.

  Furthermore, when the surface of the particles of the inorganic powder pulverized after calcination with alcohol is first coated and then mixed with an organic solvent and a plasticizer, aggregation of the pulverized inorganic powder can be further suppressed. .

  Here, if the amount of water exceeds 1.5%, the second slurry is gelled. If water is not added, a weak aggregation (flocculation) structure cannot be formed, and the effects of the present invention cannot be obtained. On the other hand, when water is added in the first step of dispersing the inorganic powder and the organic solvent, although the compressibility of the ceramic sheet 11 obtained by forming the second slurry is increased, the inorganic powder is sufficiently dispersed. The state cannot be obtained, and internal pores and vacancies are increased after firing. In this case as well, a sufficiently dense laminate cannot be obtained, and a sufficient effect on the short-circuit rate and breakdown voltage characteristics cannot be obtained.

  Thereafter, the second slurry is formed into a ceramic sheet 11 to be the dielectric layer 42 by a doctor blade method and dried (third step). In this drying, it is desirable to create a profile that gradually dries so that water in the ceramic sheet does not suddenly evaporate. The ceramic sheet 11 produced in this way has a weak aggregate structure as shown in FIG. 1 and can take a sufficiently dense structure as shown in FIG. 2 when pressed thereafter. Sheet 15 is obtained.

  Here, multilayer ceramic capacitors were respectively produced using the ceramic sheet according to the present embodiment and the ceramic sheet obtained by the conventional method, and the short-circuit occurrence rate and the breakdown voltage were compared.

  As a comparative example using the conventional method (Comparative Example 1), a ceramic slurry was prepared in the same manner as in the present embodiment except that water was not included in the slurry, and a ceramic sheet was similarly formed by the doctor blade method.

  Furthermore, as another comparative example (Comparative Example 2), this embodiment is performed except that water is not added to the second slurry in the second step and water is added to the first slurry in the first step. A ceramic slurry was prepared in the same manner as in Example 1, and a ceramic sheet was similarly formed by the doctor blade method. Next, the internal electrode paste made of Ni powder having an average particle size of about 0.2 μm on the three ceramic sheets of the ceramic sheet according to the present embodiment, the ceramic sheet of Comparative Example 1, and the ceramic sheet of Comparative Example 2. Then, a desired pattern of the internal electrode 43 is formed by screen printing.

  Next, using the ceramic sheet 11 according to the present embodiment in which the pattern of the internal electrode 43 is formed, a plurality of layers are overlapped so that the pattern of the internal electrode 43 is opposed via the ceramic sheet 11, and then heated and pressurized to be integrated. Then, it is cut into a predetermined size to produce an unsintered laminate 14 (fourth step). Similarly, an unsintered laminated body is similarly produced about the ceramic sheet with the internal electrode 43 produced in Comparative Example 1 and Comparative Example 2. When these three types of unsintered laminates are fired, the dielectric layers have a thickness of 2.5 μm and the number of dielectric layers is 250 layers.

  Then, the three kinds of unsintered laminates are put into a zirconia firing container (fired sheath) laid with zirconia powder, heated to 350 ° C. in nitrogen, and the organic binder is burned to degrease.

Thereafter, the sintered body is obtained by firing at 1250 ° C. for 2 hours in a mixed gas of N ₂ + H ₂ (fifth step). The firing temperature is appropriately selected between 1100-1300 ° C. depending on the composition of the dielectric layer.

  Next, a copper paste for firing in a nitrogen atmosphere is applied to the end face where the internal electrodes 43 of the three types of sintered bodies are exposed, and the external electrode 44 is formed by baking with a mesh-type continuous belt furnace. 44 is subjected to Ni plating and Sn plating to obtain a multilayer ceramic capacitor sample as shown in FIG.

The resistance value of each of the three types of multilayer ceramic capacitor samples of this embodiment and Comparative Examples 1 and 2 is measured using an insulation resistance meter, and the number of samples having a resistance value of 10 ⁶ Ω or less is expressed as a percentage. It was expressed as a short rate.

Similarly, a boost breakdown test was conducted on each of the above three types of multilayer ceramic capacitor samples, and the average value of voltages at the time of breakdown is shown in (Table 1). Furthermore, several dozen ceramic sheets 11 according to the present embodiment were overlapped and pressed and integrated with a pressure of 500 kg / cm ² , punched into a disk shape, and the density was measured. Further, the density of the ceramic sheet of the comparative example was measured in the same manner as described above. The density measurement results are also shown in (Table 1).

  As is clear from Table 1, the sample produced in the present embodiment has the highest ceramic sheet density, and therefore the short-circuit rate is very small, and the breakdown voltage value is also high.

  In contrast, the sample of Comparative Example 1 in which water was not added to the second slurry and the comparative example in which water was added to the slurry, but water was added in the first step instead of the second step. In No. 2, the density of the ceramic sheet is low, the short-circuit rate is large, and the breakdown voltage value is also low.

  That is, according to the method according to the present embodiment, the inorganic powder and the organic substance are dispersed, and then water is added to further disperse to produce a slurry. The ceramic sheet 11 formed from this slurry has an agglomerated loose microstructure. This is a state (flocculate), and this loose aggregated state changes to a dense packing state by pressurization in lamination, so that a high-density laminated body is obtained, and as a result, a multilayer ceramic with a low short-circuit rate and high breakdown voltage A capacitor is obtained.

  In the method for manufacturing a ceramic electronic component according to the present invention, an inorganic powder, a plasticizer, and an organic solvent are dispersed to produce a first slurry, and an organic binder is dispersed into the first slurry to produce a second slurry. The ceramic prepared using the second slurry by adding and dissolving an organic binder and then adding water of 1.5 wt% or less (excluding 0 wt%) to 100 wt% of the inorganic powder. When a weakly aggregated state is formed in the sheet and a laminate is produced by alternately laminating this ceramic sheet and internal electrodes, a dense laminate is obtained, so the short-circuit rate is low and the breakdown voltage characteristics are improved. Ceramic electronic components can be obtained.

Sectional drawing which shows typically the state of the ceramic sheet before pressurization in one embodiment of this invention Sectional drawing which shows the state of the ceramic sheet after the pressurization typically Sectional view schematically showing the structure of the green laminate Partial cutaway perspective view of a conventional multilayer ceramic capacitor

Explanation of symbols

11, 21 Ceramic sheet 12 Inorganic powder particles 13 Vehicle 14 Laminate 15 Pressurized ceramic sheet 41 Multilayer ceramic capacitor 42 Dielectric layer 43 Internal electrode 44 External electrode

Claims (2)

A first step of producing a first slurry by dispersing at least an inorganic powder, a plasticizer, and an organic solvent; and a second step of producing a second slurry by dispersing an organic binder in the first slurry. , A third step of producing a ceramic sheet from the second slurry, a fourth step of alternately laminating the ceramic sheet and internal electrodes to produce a laminate, and a fifth step of firing the laminate. And, after adding and dissolving the organic binder in the second step, 1.5 wt% or less (excluding 0 wt%) of water is added to 100 wt% of the inorganic powder. . The average particle diameter (D50) of the inorganic powder before producing the first slurry is A, the specific surface area value is Sa, and the average particle diameter (D50) of the inorganic powder in the first slurry is B, the specific surface area. The inorganic powder satisfying A and B and Sa and Sb satisfying 0.8A ≦ B ≦ 1.0A and Sb ≦ 1.5Sa, when Sb is Sb, is used in preparing the first slurry. Of manufacturing ceramic electronic parts.

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