JP2756745B2 - 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 (multilayer ceramic capacitor) capable of preventing separation between an internal electrode layer and a ceramic layer.

[0002]

2. Description of the Related Art When a multilayer ceramic capacitor is manufactured, a plurality of ceramic green sheets (green sheets) having internal electrode layers (capacitor electrode layers) and a cover having no internal electrode layers disposed above and below these sheets are provided. A laminate of the ceramic green sheet for preparation and a trim having no internal electrode layer, that is, a ceramic raw sheet for preparation, disposed between a plurality of sets of the ceramic green sheet having internal electrode layers as necessary.

[0003]

Incidentally, delamination (peeling) may occur between the internal electrode layer and the cover layer or the trim layer. This delamination is considered to be caused by the non-uniformity of the thermal conductivity and the non-uniformity of the pressure bonding of the laminate. That is, since the internal electrode layer has a higher thermal conductivity than the ceramic layer, sintering and shrinkage of a relatively thin region sandwiched between the internal electrode layers starts earlier than a relatively thick cover layer or trim layer. Although the internal electrode layer and the ceramic adhere well, the ceramic does not adhere well to the internal electrode layer in the cover layer or trim layer where sintering is delayed, and delamination occurs. Also, since the ceramic layers between the internal electrode layers in the center of the laminate are relatively thin, the thickness of the internal electrode layers cannot be ignored, and the internal electrode layers are strongly penetrated into the ceramic layers during crimping. Although good adhesion can be obtained, adhesion to the relatively thick cover layer or trim layer does not occur because strong penetration of the internal electrode layer does not occur, resulting in delamination.

It is an object of the present invention to provide a method for manufacturing a multilayer ceramic capacitor in which the internal electrode layer is less likely to peel (delamination).

[0005]

In order to achieve the above-mentioned object, the present invention provides a first ceramic green sheet comprising a first ceramic powder having a first particle size and a plurality of sheets each having an internal electrode layer provided thereon. A cover made of one or more of a stacked capacitance acquisition portion and a second ceramic green sheet made of a second ceramic powder having a second particle size smaller than the first particle size and not having the internal electrode layer. The present invention relates to a method for manufacturing a multilayer ceramic capacitor, which comprises forming a laminate having a portion and / or a trim portion and firing the laminate.

[0006]

In general, as the particle size of the ceramic powder becomes smaller, the reactivity increases and the temperature at which sintering starts is lowered. In the present invention, since the particle size of the ceramic powder of one or both of the cover portion and the trim portion is smaller than the particle size of the ceramic powder of the first ceramic green sheet provided with the internal electrode layer, An effect of hastening the start of sintering of the trim portion occurs, and uniform sintering start is achieved in all regions of the laminate, and delamination of the internal electrodes can be prevented.

[0007]

Next, a method of manufacturing a multilayer ceramic capacitor according to an embodiment of the present invention will be described. First, in order to obtain a capacitor for X7R standard, the average particle size is 1.0 μm.
Two kinds of (BaTiO ₃ + Nb ₂ O ₅ + Co ₂ O ₃ ) + SrO barium titanate-based ceramic powder of (first particle size) and 0.5 μm (second particle size) were prepared. Next, an organic binder is added to the ceramic powders of 1.0 μm and 0.5 μm to form respective slurries, and a long ceramic raw sheet (porcelain raw sheet) of about 23 μm in thickness, that is, green by a doctor blade method. A plurality of first and second green sheets were respectively obtained by forming sheets and cutting them into predetermined dimensions.

Next, palladium (P) is applied to a plurality of first green sheets based on ceramic powder having a particle size of 1.0 μm.
A conductive paste composed of d), an organic binder, and a solvent was applied to form a predetermined pattern of internal electrode layers for 50 laminated capacitors.

Next, a plurality of first green sheets having an internal electrode layer and a particle size of 0.5 μm having no internal electrode layer
A second green sheet made of a ceramic powder is laminated by a known method and thermocompressed under the conditions of a pressure of 350 kg / cm ² and 70 ° C., and then a predetermined size (1.83 mm × 0.92 m) is obtained.
m) By cutting, the laminate having the structure shown in FIG.
0 were obtained. This laminate 1 has electrode layers E1, E2, E3, E4 composed of a first green sheet based on a ceramic powder having a particle diameter of 1.0 μm and having an internal electrode layer 2; Cover layers C1, C2 consisting of a second green sheet based on 0.5 .mu.m ceramic powder
, C3, C4, C5 and a trim layer T1. After the thermocompression bonding, the green sheets are integrated, but are separately shown in FIG. 1 for convenience of explanation.

In FIG. 1, a plurality of internal electrode layers 2 are alternately led out in opposite directions. Three cover layers C1 to C3 are arranged on the uppermost internal electrode layer 2, and two cover layers C4 and C5 are arranged below the lowermost electrode layer E4. A trim layer T1 is arranged between the layers E2 and E3. The trim layer T1 is composed of a first capacitance acquisition section composed of two upper electrode layers E1 and E2 with an internal electrode layer 2 and a second capacitance acquisition section composed of two lower electrode layers E3 and E4. And functions as a buffer layer interposed between them.

Next, the laminate 1 is placed in a furnace and heated at a rate of 40 ° C./hr from room temperature to 1100 ° C. in the air atmosphere, and 160 ° C./hr from 1100 ° C. to 1300 ° C.
And heated at 1300 ° C. for 1 hour to obtain a sintered body. Next, as shown in FIG. 2, a pair of external electrode layers 4 and 5 were provided on the sintered body 3 to complete a multilayer ceramic capacitor.

Next, the internal electrode layer 2 in the sintered body 3
When delamination (peeling) of the ceramic layer 3a into the ceramic layer 3a was examined, no delamination occurred in all of the 50 capacitors. For comparison, the cover layer C1
C5, the sintered body was made in the same manner as in the embodiment except that the particle size of the ceramic powder of the trim layer T1 was 1.0 μm, which is the same as that of the electrode layers E1 to E4, and the delamination of the internal electrode layer was reduced. Inspection revealed that 32 capacitors were generated for every 50 capacitors.

The cover layers C1 to C5 and the trim layer T1
In order to investigate in detail the relationship between the change in the particle size of the ceramic powder and the delamination, the cover layer C was prepared by setting the particle size of the ceramic powder in the electrode layers E1 to E4 to 1.0 μm.
1 to C5 and the particle size of the ceramic powder of the trim layer T1 are 0.4, 0.6, 0.7, 0.8, 0.9 and 1.2 .mu.m.
A sintered body was prepared in the same manner as in the above embodiment except that the internal electrode layer was delaminated, and two, zero, zero, zero, five, and forty-five were obtained. Met.
As is clear from this, the particle size of the ceramic powder of the cover layers C1 to C5 and the trim layer T1 is 0.5 to 0.8 .mu.m.
In other words, it is desirable that the content be 50% to 80% with respect to the particle size of the ceramic powder of the electrode layers E1 to E4.
Similar results were obtained when the rate of temperature increase from 1100 ° C to 1300 ° C during firing was 320 ° C / hr or 80 ° C / hr. However, the lower the heating rate, the lower the occurrence of delamination.

[0014]

[Modifications] The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible. (1) The composition and / or particle size of the ceramic powder can be variously changed. (2) The trim layer T1 can be omitted. (3) The number of electrode layers can be further increased. (4) The firing temperature of the laminate can be changed, for example, in the range of 900 ° C. to 1400 ° C. according to a change in composition or the like. (5) Silver, silver-palladium, nickel or the like can be used as an electrode material of the internal electrode layer. (6) The thickness of the ceramic green sheet can be variously changed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a laminate according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a completed multilayer ceramic capacitor.

[Explanation of symbols]

 2 Internal electrodes E1 to E4 Electrode layers C1 to C5 Cover layer T1 Trim layer

Claims (1)

(57) [Claims] 1. A capacity acquisition section in which a plurality of first ceramic green sheets made of a first ceramic powder having a first particle size and provided with internal electrode layers are stacked, and no internal electrode layer is provided. A second particle having a second particle size smaller than the first particle size;
Forming a laminate having at least one cover portion and / or trim portion of a second ceramic green sheet made of a ceramic powder, and firing the laminate. .