JP3147667B2 - Manufacturing method of multilayer ceramic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer ceramic capacitor.

[0002]

2. Description of the Related Art Conventionally, a multilayer ceramic capacitor has been obtained as follows.

[0003] First, a green sheet is formed on a film by a doctor blade method or the like, and then an internal electrode is formed by printing a conductive paste on the green sheet. Lamination is performed so that the internal electrodes are alternately exposed on the opposite end faces, pressure bonding is performed from above the film, and then a process of peeling the film is repeated to obtain a laminate, and then the laminate is cut. Thereafter, firing was performed to form external electrodes.

[0004]

In order to reduce the size and increase the capacity of the multilayer ceramic capacitor, it is necessary to increase the thickness of the dielectric as well as the thickness of the dielectric as much as possible. However, in the above configuration, when the dielectric material is thinned (when the thickness after firing is set to about 15 μm or less), pressure bonding by pressure alone locally causes poor adhesion and causes internal structural defects such as delamination. There was a problem that.
Also, when printing the conductive paste on the green sheet,
Since the organic solvent contained in the conductive paste swells into the ceramic sheet, micro pinholes are generated in the sheet, or the conductive material penetrates, causing short-circuit failure and the like, leading to a decrease in reliability. Had problems.

Accordingly, an object of the present invention is to provide a large-capacity multilayer ceramic capacitor free from internal structural defects even if the thickness of the dielectric is reduced.

[0006]

In order to achieve this object, the present invention forms a ceramic sheet composed of at least two layers on a carrier film, and forms a conductive sheet on the ceramic sheet as an internal electrode. When applying the conductive paste and laminating the ceramic sheets so that the internal electrodes and the ceramic sheets are alternately arranged, each time the layers are laminated, they are heated and pressed on the carrier film, and then the carrier film is peeled off to form a laminate. After forming and then firing this laminate, external electrodes are formed.

[0007]

With such a configuration, when applying the conductive paste to the ceramic sheet, even if pinholes are generated by the organic solvent or the conductive material is infiltrated by the swelling of the organic solvent, the ceramic sheet is multilayered. Because of the structure, the lower layer sheet covers this, prevents pinholes from penetrating between the ceramic sheets, and prevents the conductive substance from penetrating, thereby preventing short circuit failure. Further, by performing the heat and pressure bonding on the carrier film, the plasticity of the ceramic sheet is improved, the bonding state is improved, the occurrence of delamination can be prevented, and the high lamination can be further improved.

Thus, a large-capacity multilayer ceramic capacitor having no internal structural defects can be obtained.

[0009]

【Example】

Embodiment 1 Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

First, 100 parts by weight of BaTiO ₃ based powder,
12 parts by weight of polyvinyl butyral resin, 65 parts by weight of n-butyl acetate, 5 parts by weight of dibutyl phthalate were mixed,
Dielectric slurry 1 was prepared. Next, as shown in FIG. 2, a 38 μm-thick polyester film, the surface of which is coated with a silicone-based release agent, was used as a carrier film 2. The thickness after firing is 5
A ceramic sheet 3 was formed so as to have a thickness of 0 μm, and this was taken up as a first sheet.

As shown in FIG. 1, a two-layer structure is formed on the carrier film 2 by a doctor blade method and the thickness after firing is 13 μm (the thickness of each of the upper and lower layers is 6.5 μm). Then, the ceramic sheet 4 was formed and wound up in a roll shape. Next, this 2
A palladium paste as a paste for the internal electrode 5 is printed and applied in a predetermined print pattern on the ceramic sheet 4 having a layer structure by a screen printing method as shown in FIG. 3, and then wound in a roll while drying at 80 ° C. Take second
Sheet. Thereafter, the first sheet and the second sheet were cut into a predetermined size according to the size of a metal pallet 6 described later. Next, as shown in FIG. 4, a polyester film 7 with an adhesive containing a foaming agent is attached on a metal pallet 6 with the surface with the adhesive facing up, and a lower ineffective layer is formed thereon. The first sheet is placed so as to face the polyester film 7 side, and the temperature is set to 85 ° C. and the pressure is set to 45 ° from the top of the carrier film 2 of the first sheet.
After thermocompression bonding at kg / cm ² , the carrier film 2 was peeled off and thermally transferred. Next, another one of the first sheets was thermally transferred by the procedure described above. Here, metal pallet 6
The reason why the adhesive-containing polyester film 7 containing a foaming agent is adhered is to prevent the lower ineffective layer ceramic sheet 3 from being displaced from the metal pallet 6 and to facilitate peeling of the laminate. . Next, as shown in FIG. 4, FIG. 5, and FIG. 6, the second sheet is placed on the ceramic sheet 3 for the lower ineffective layer so that the carrier film 2 side faces upward, and At a temperature of 85 ° C. and a pressure of 45 kg / cm ² using a pressure head 8,
After thermocompression bonding, the carrier film 2 was peeled off and thermally transferred. Next, the second sheet was subjected to a laminating operation by thermal transfer such as laminating, thermocompression bonding, and peeling of the carrier film 2 under the above conditions until the effective layer became 50 layers. At this time, while shifting the electrode pattern so that the palladium paste that becomes the internal electrode 5 alternately reaches different edges, the second
Were laminated by thermal transfer. On the heat-transferred ceramic sheet 4 located on the uppermost part of the pressure-bonded body thus obtained, the ceramic sheet 3 formed on the release agent-treated surface of the 38 μm polyester film 2 and having a fired thickness of 50 μm was formed. The sheets 3 and 4 were arranged so as to face each other. Next, after the carrier film 2 is heat-pressed at the same temperature and the same pressure as above, the carrier film 2 is peeled off, thermally transferred, and another lower first sheet is thermally transferred in the same manner. The upper invalid layer having the same two-layer structure as the invalid layer is formed,
The laminated body as shown in was obtained. Next, the laminate is brought to room temperature,
After the main press at 500 kg / cm ² , the laminate is separated from the polyester film 7 by cutting into a predetermined size and heating and foaming the adhesive of the polyester film 7 with an adhesive containing a foaming agent. Then, it was taken out of the metal pallet 6 and divided into individual pieces. Next, the laminated body divided into individual pieces was held at 350 ° C. for 6 hours to be binder-out, and then fired at 1300 ° C. for 2 hours. Next, after chamfering the end face of the multilayer body, an Ag paste was applied and baked as the external electrode 9 in FIG. 8 to obtain a multilayer ceramic capacitor as shown in FIG.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.

When forming the second sheet formed in Example 1, as shown in FIG. 9, a dielectric slurry 1 is applied on a carrier film 2 by a doctor blade method and dried in a drying zone 10. Thus, a first layer was formed, and then a second layer was applied on the first layer and dried in the drying zone 10 to obtain a ceramic sheet 4 having a two-layer structure. The thickness of the ceramic sheet 4 after firing was 13 μm (each layer was 6.5 μm) as in Example 1. A second sheet is formed by applying a palladium paste to be the internal electrode 5 on the ceramic sheet 4.
In the same manner as in Example 1, a multilayer ceramic capacitor shown in FIG. 8 was obtained.

Comparative Example For comparison with Examples 1 and 2, a monolithic ceramic sheet having a thickness of 13 μm after firing was used as an effective layer, and a multilayer ceramic capacitor was formed in the same manner as in the prior art. .

With respect to the multilayer ceramic capacitors produced in Examples 1 and 2 and Comparative Example, the initial short-circuit rate and the state of deterioration in insulation resistance after a moisture resistance load test for 1000 hours (85 ° C., 85% RH) were examined. At this time, the initial short,
In both cases of the moisture resistance load test, 1.0 * 10 ⁸ or less was judged as a deteriorated product, and the results are shown in Table 1.

[0016]

[Table 1]

As is clear from Table 1, Examples 1 and 2
2 has an initial short-circuit rate,
Excellent in both moisture resistance. This is because the ceramic sheet 4 to which the conductive paste to be the internal electrode 5 is applied has a multi-layer structure, so that the solvent in the conductive paste causes pinholes or the conductive material penetrates due to the swelling of the solvent. This is because it is also possible to block in the ceramic sheet and prevent penetration. The same applies when the thickness of the ceramic sheet 4 between the internal electrodes 5 is reduced.

In the first and second embodiments, the thickness of each layer of the ceramic sheet 4 having the two-layer structure is the same. However, if the same effect as in the present embodiment can be obtained, the first layer may be used. And the thickness of the second layer may be different.

In the first and second embodiments, the ceramic sheet 4 has a two-layer structure, but may have three or more layers.

Further, in Examples 1 and 2, the doctor blade method was used as a method for producing the ceramic sheets 3 and 4, but other methods such as a reverse roll coater method and a die coater method can be used. The same effect is obtained.

Although the internal electrode 5 is also formed using a palladium paste, it is also effective to use another internal electrode, for example, a paste of silver-palladium, nickel, copper or the like.

Further, the same effect can be obtained even if the ceramic sheets 3 and 4 are not barium titanate-based materials but other dielectric materials.

The ineffective layers provided above and below are formed by thermal transfer of the ceramic sheet 3. However, the use of other means does not affect the present invention.

Further, when forming the ceramic sheets 3 and 4, a polyester film whose surface is coated with a release agent was used. This is because the strength of the ceramic sheets 3 and 4 is reduced, and the peeling is not sufficient at the time of the thermal transfer, and as a result, the pressure bonding between the ceramic sheets 3 and 4 is caused. Therefore, it is preferable to use the carrier film 2 having strength, elasticity, and releasability.

The thickness of the carrier film 2 is also 38
The thickness may be other than μm.

[0026]

As described above, according to the present invention, by forming the ceramic sheet used for the effective layer into a multilayer structure, even if pinholes or the infiltration of the conductive substance by the conductive paste occurs, the ceramic sheet can be used. The short circuit can be prevented.
Further, by performing the heat and pressure bonding on the carrier film, the plasticity of the ceramic sheet is improved, the bonding state is improved, the occurrence of delamination can be prevented, and the high lamination can be further improved.

Thus, a large-capacity multilayer ceramic capacitor free from internal structural defects can be obtained.

Further, as shown in the above embodiments, the multilayer ceramic capacitor of the present invention has excellent moisture resistance.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a process for producing a ceramic sheet having a two-layer structure in one embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a single-layer ceramic sheet manufacturing process according to one embodiment of the present invention.

FIG. 3 is a plan view of a second sheet according to the embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a laminating step in one embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a laminating step in one embodiment of the present invention.

FIG. 6 is a cross-sectional view illustrating a laminating step in one embodiment of the present invention.

FIG. 7 is a sectional view of a laminate according to one embodiment of the present invention.

FIG. 8 is a sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention.

FIG. 9 is a cross-sectional view illustrating a step of manufacturing a ceramic sheet having a two-layer structure according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dielectric slurry 2 Carrier film 3 Ceramic sheet 4 Ceramic sheet 5 Internal electrode 6 Metal pallet 7 Polyester film 8 Pressure head 10 Drying zone

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-143410 (JP, A) JP-A-2-208915 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01G 4/00-4/40 H01G 13/00-13/06

Claims (1)

(57) [Claims] 1. A ceramic sheet comprising at least two layers is formed on a carrier film, an internal electrode is formed on the ceramic sheet, and then the ceramic sheets are laminated. Abbreviated from
After the thermocompression bonding at 85 ° C., the step of peeling the carrier film is performed a predetermined number of times.
A method of manufacturing a multilayer ceramic capacitor in which a laminate is formed by repeating attachment and separation of a carrier film, and then fired to form external electrodes.