JP4513388B2 - Manufacturing method of multilayer ceramic electronic component - Google Patents

Description

  The present invention relates to a method for manufacturing a multilayer 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.

  First, a ceramic sheet is prepared by mixing a solvent, a binder, a plasticizer, and the like with inorganic powder mainly composed of barium titanate.

  Next, a metal paste is printed on the ceramic sheet in a desired internal electrode shape.

  The metal paste is a mixture of Ni powder, the same inorganic powder as the inorganic powder constituting the ceramic sheet, and an organic substance such as a binder and a solvent.

  Next, the ceramic sheets on which the metal paste is printed are laminated to produce a laminated body and fired.

  Thereafter, external electrodes are formed to obtain a multilayer ceramic capacitor.

For example, Patent Document 1 is known as prior art document information related to the invention of this application.
JP-A-9-69467

  By adding the same inorganic powder as the ceramic sheet to the internal electrode, the adhesion between them can be improved.

  However, the barium titanate added to the metal paste in the conventional method is the same as the barium titanate used for the ceramic sheet.

  Therefore, since the barium titanate in the metal paste and the barium titanate in the ceramic sheet are sintered at the same time, there is a problem that defects are likely to occur in the internal electrode due to the reaction between both of them and grain growth. It was.

  Accordingly, an object of the present invention is to provide a multilayer ceramic electronic component that suppresses defects in internal electrodes and has electrical characteristics such as a desired capacitance value.

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

  The present invention provides a ceramic sheet mainly composed of a first barium titanate, and a second barium titanate in which the ratio c / a of the c-axis to a-axis of the crystal lattice constant is larger than that of the first barium titanate. The internal electrode paste contained is alternately laminated to produce a laminate, and the barium titanate in the metal paste has a higher sintering temperature than the barium titanate in the ceramic sheet. Therefore, the occurrence of defects in the internal electrode can be suppressed.

In the method for producing a multilayer ceramic electronic component according to the present invention, the value of c / a of the crystal lattice constant of barium titanate added to the metal paste serving as the internal electrode is the main component in the ceramic sheet serving as the dielectric layer. A barium titanate having a c / a value larger than that of barium titanate is used , and the barium titanate added to the metal paste is 15 parts by weight to 25 parts by weight when the metal powder weight is 100 parts by weight. since had, it is possible to control the sintering of the barium titanate during firing, to suppress the defects of the internal electrodes, to provide a laminated ceramic electronic component having the desired electrical characteristics.

Hereinafter, the present invention will be described with reference to an embodiment using a multilayer ceramic capacitor as an example.

  FIG. 1 is a partially cutaway perspective view of a multilayer ceramic capacitor. Dielectric layers 10 and internal electrodes 11 are alternately stacked to form a multilayer body, and the internal electrode 11 has an end facing the multilayer body. They are laminated so as to be alternately exposed on both end faces, and are alternately connected to a pair of external electrodes 12 formed on both end faces of the laminate.

First, as the main component, the first barium titanate having three kinds of c / a shown in (Table 1), a rare earth element compound such as Dy ₂ O ₃ as an auxiliary component, MgO, MnO _2, etc. Add and mix, calcine and pulverize to produce ceramic powder. Here, c / a represents the ratio of the crystal lattice constant of the c-axis to the a-axis in the barium titanate crystal lattice.

  Thereafter, this ceramic powder is mixed with polyvinyl butyral resin as an organic binder, n-butyl acetate as a solvent, phthalate ester as a plasticizer, and the like to obtain a ceramic slurry. And the ceramic sheet used as the dielectric material layer 10 by baking is produced using a doctor blade method etc.

On the other hand, the second barium titanate having three kinds of c / a values shown in (Table 1) is changed to 15, 25, 30 parts by weight with respect to 100 parts by weight of Ni powder, and a predetermined amount of Dy _{2 is obtained.} A rare earth compound such as O ₃ , polyvinyl butyral resin as an organic binder, n-butyl acetate as a solvent, and a phthalate ester as a plasticizer are mixed, and a metal paste that becomes the internal electrode 11 is prepared by firing.

  Here, the first barium titanate added to the ceramic sheet and the second barium titanate added to the metal paste will be described.

  The value of c / a, which is the ratio of the lengths of the a-axis and c-axis of the barium titanate crystal lattice, takes a value between 1 and 1.01, but this value is less than that of the first barium titanate. The larger the barium titanate, the larger the difference between the two is more preferable because the reaction between the two is less likely to occur in the firing step and can contribute to the suppression of internal structural defects.

  Note that barium titanate having a c / a value exceeding 1.01 cannot be used as a dielectric layer of a multilayer ceramic capacitor or the like because of a different crystal structure.

  In the present embodiment, as shown in Table 1, barium titanate having a c / a value of 1.006 to 1.008 was used as the first and second barium titanates.

  The average particle diameter of the first barium titanate and the second barium titanate is 0.4 μm. However, it is important that the particle diameter of the second barium titanate is not larger than the thickness of the internal electrode 11 in order to prevent defects in the internal electrode.

  Further, the first barium titanate and the second barium titanate are produced by a solid phase method. This is because barium titanate having a large c / a can be easily obtained by this method.

  The sintering start temperature of barium titanate having the value of c / a shown in Table 1 was measured using thermal analysis. As a result, a sample having a c / a value of 1.006 was 1050 ° C., and c The / a value of 1.007 was 1150 ° C., and the c / a of 1.008 was 1200 ° C.

  The weight of the second barium titanate in the metal paste is 25 parts by weight or less (excluding 0), preferably 10 to 25 parts by weight when the weight of the metal powder is 100 parts by weight. The adhesiveness between the dielectric layer 10 and the internal electrode 11 can be improved while suppressing the occurrence of electrode defects. However, when the amount exceeds 25 parts by weight, the defect of the internal electrode 11 due to the barium titanate becomes remarkable, which is not preferable.

  Next, the above metal paste is screen-printed on the ceramic sheet in a desired internal electrode shape.

  Next, a desired number of ceramic sheets printed with a metal paste are laminated on a laminate of only a plurality of ceramic sheets, and a plurality of ceramic sheets alone are further laminated to obtain a laminate.

Next, after cutting the laminate into a desired shape, it is placed in a zirconia sheath with zirconia powder and heated to 350 ° C. in nitrogen to burn the organic binder, and then the maximum temperature in N ₂ + H ₂ Firing is performed at 1250 ° C. for 2 hours to obtain a sintered body.

  This firing process will be described.

  First, the sintering of Ni in the metal paste starts at 500 to 600 ° C., but the Ni metal powder reacts with the added barium titanate, and the sintering proceeds excessively, and Ni becomes granular due to surface tension. This prevents the continuity of the internal electrodes from being impaired.

  Subsequently, the sintering of the ceramic sheet starts from about 1100 ° C. However, when the c / a of barium titanate in the metal paste is 1.007, sintering does not start unless the temperature is about 1150 ° C. or higher.

  That is, barium titanate in the metal paste is sintered after sintering of the ceramic sheet is almost completed.

  As a result, the metal paste and barium titanate in the ceramic sheet react with each other, and the generation of defects in the internal electrode 11 induced by grain growth can be suppressed.

  Next, a copper paste for firing at 900 ° C. in a nitrogen atmosphere is applied as the external electrode 12 to the exposed end face of the internal electrode 11 of the obtained sintered body and baked to obtain a multilayer ceramic capacitor as shown in FIG.

  With respect to these sample numbers 1 to 5, the cross sections of 100 samples were observed, and the number of samples in which delamination was generated is shown in (Table 1) as the number of delamination generation.

  As shown in Table 1, the multilayer ceramic capacitors of sample numbers 2 to 4 do not generate delamination, which is a defect of the internal electrode 11, and as a result, a desired capacitance is obtained.

  In the present embodiment, barium titanate having a larger c / a (ratio between the lengths of the a-axis and the c-axis of the barium titanate crystal lattice) than barium titanate in the ceramic sheet is added to the metal paste. The c / a of barium titanate that undergoes a phase transition accompanying a temperature change varies in the range of 1 to 1.01, and the sintering temperature increases as c / a increases. More preferably, barium titanate added to the internal electrode 11 is one having a sintering temperature higher by 50 ° C. or more than barium titanate added to the ceramic sheet.

  As a result, abnormal grain growth due to the reaction between the metal paste and barium titanate added to the ceramic sheet can be suppressed, and the occurrence of defects in the internal electrode 11 can be prevented.

  In the embodiment of the present invention, barium titanate having a different c / a value was used to suppress oversintering of the metal paste serving as the internal electrode, thereby suppressing the occurrence of internal structural defects. The same effect as described above can be obtained by shifting the sintering start temperature of barium titanate in the metal paste using barium titanate having a different crystal grain size instead of using the value.

In the method for manufacturing a multilayer ceramic electronic component according to the present invention, the value of c / a of the crystal lattice of barium titanate added to the metal paste serving as the internal electrode is set to titanium which is the main component in the ceramic sheet serving as the dielectric layer. A barium titanate having a value larger than the c / a value of barium oxide was used , and the barium titanate added to the metal paste was 15 to 25 parts by weight when the metal powder weight was 100 parts by weight. Therefore, it is possible to control the sintering of barium titanate during firing, to suppress the defects of the internal electrodes, and to provide a multilayer ceramic electronic component having desired electrical characteristics. It is useful for the manufacturing method of multilayer ceramic electronic parts.

1 is a partially cutaway perspective view of a multilayer ceramic capacitor according to a first embodiment of the present invention.

Explanation of symbols

10 Dielectric layer 11 Internal electrode 12 External electrode

Claims (2)

A first step of producing a laminate by alternately laminating a ceramic sheet mainly composed of a first barium titanate, a metal powder, and a metal paste containing a second barium titanate; A second step of firing, and the c-axis of the second barium titanate crystal lattice from the value of the ratio of the c-axis to the a-axis (c / a) of the first barium titanate crystal lattice; Ri Nedea large value of the ratio of a-axis (c / a), a second barium titanate, laminated ceramics used as a 15 weight parts to 25 parts by weight when the metal powder by weight and 100 parts by weight Manufacturing method of electronic components. The method for producing a multilayer ceramic electronic component according to claim 1, wherein the second barium titanate is produced by a solid phase method.

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