JP4752691B2 - Ceramic green sheet, multilayer ceramic electronic component using the same, and manufacturing method thereof - Google Patents

Description

  The present invention relates to a ceramic green sheet, a multilayer ceramic electronic component using the same, and a method for manufacturing the same.

  Conventionally, multilayer ceramic electronic components have been developed as electronic components for realizing high-density mounting as multilayer inductors, LC filters, or noise filters based on multilayer ceramic capacitor technology. A multilayer ceramic capacitor, which is a representative example of this multilayer ceramic electronic component, is manufactured as follows.

First, a dielectric composition mainly composed of BaTiO ₃ , an organic binder, a plasticizer, and the like are added to a dispersion medium such as water or an organic solvent, and then mixed to prepare a dielectric slurry, and then a doctor blade method. A dielectric ceramic green sheet (hereinafter simply referred to as a ceramic green sheet) having a predetermined thickness is obtained by sheet molding. Next, after an electrode pattern is formed on the ceramic green sheet using an electrode paste by a screen printing method or the like, the printed electrodes are alternately exposed on both end faces of the individual pieces when separated into individual pieces. Then, a plurality of stacked layers are obtained by aligning them so that they can be connected to external electrodes. By separating the obtained laminate into individual pieces, firing at a firing temperature of about 1300 ° C., and then forming a pair of external electrodes so as to connect to the electrodes exposed at both ends of the separated fired body. Have been made.

In addition, when thinning the ceramic green sheet to obtain a high-capacity multilayer ceramic capacitor, in addition to the method of directly printing the electrode pattern on the ceramic green sheet, it is disclosed in, for example, Patent Document 1 and Patent Document 2 As described above, a method of transferring an electrode pattern by forming an electrode pattern on a support such as a PET film and then pressing it onto a ceramic green sheet has been proposed.
JP-A-63-31104 JP-A-63-32909

  However, when printing directly on the ceramic green sheet as in the former conventional method, if the ceramic green sheet is thinned in order to obtain a high capacity, the erosion of the ceramic green sheet by the electrode paste that occurs at the time of electrode pattern printing will occur. Adverse effects become prominent, and there is a problem that the short circuit rate is increased and the dielectric breakdown voltage is liable to be lowered.

  Further, in the method of transferring the electrode pattern to the ceramic green sheet after forming the electrode pattern on another support such as the PET film as in the latter conventional method, the ceramic green sheet is relatively free from the erosion of the ceramic green sheet by the electrode paste. For example, when the thickness of the ceramic green sheet is less than 2.5 μm and becomes a highly laminated product exceeding 300 layers, the ceramic green sheet itself is damaged due to insufficient strength. The effects of sheet displacement and sheet elongation at the time become remarkable, and as a result, there is a problem that an increase in the short-circuit rate and a decrease in dielectric strength are likely to occur.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and a ceramic green sheet that can suppress an increase in short-circuit rate and a decrease in dielectric strength even when a dielectric layer is thinned, a multilayer ceramic electronic component using the same, and a production thereof It is intended to provide a method.

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

This onset Ming, especially, Tg of 30 ° C. or less, a polyester resin, EVA - those containing the (ethylene-vinyl acetate copolymer) resin, polyamide resin, at least one selected from the group consisting of polypropylene resin Thus, it is possible to suppress an increase in the short-circuit rate and a decrease in the withstand voltage. Moreover, not only the strength of the sheet can be improved, but also electrode step absorption and adhesion during lamination can be exhibited.

This onset Ming also in tensile strength, elastic constant at room temperature is 300N / mm ² or more, the strain at break of at lamination temperature is obtained by the fact that 20% or more, thereby, be thinned As well as being excellent in lamination properties, it is possible to suppress an increase in short-circuit rate and a decrease in dielectric strength voltage.

The present onset bright is obtained by the non-addition of a plasticizer, it can thereby be less likely to creep phenomena such as sheet misalignment or sheet elongation at the time of stacking.

Further, the present invention is a multilayer ceramic capacitor using a ceramic green sheet, and the use of the ceramic green sheet can suppress an increase in short-circuit rate and a decrease in dielectric strength.

In the present invention, the thicknesses of the upper and lower outermost effective layers are substantially the same, thereby suppressing the elongation of the sheet by the laminating process. As a result, the short circuit ratio is increased and the withstand voltage is decreased. Can be suppressed.

In the present invention, the ceramic green sheet is laminated after being heated to 60 ° C. or higher. By heating the ceramic green sheet before lamination, a high elastic modulus is obtained at room temperature, and the internal electrode is laminated at the time of lamination pressure bonding. It is possible to realize an excellent laminate property such as step absorption and adhesion, and it is possible to manufacture a highly reliable multilayer ceramic electronic component in a short time.

  The ceramic green sheet of the present invention has a high elastic modulus at room temperature, reduces the damage to the sheet in the process, the effect of sheet collapse and sheet shrinkage, and expresses the step difference absorption and adhesion at the time of laminating and bonding, and has excellent laminating properties. Therefore, even when the dielectric layer is thinned, an effect that a highly reliable multilayer ceramic electronic component can be manufactured without increasing the short-circuit rate and lowering the withstand voltage is obtained.

(Embodiment 1)
Hereinafter, the first and second aspects of the present invention will be described with reference to the first embodiment.

  In addition, it demonstrates using a multilayer ceramic capacitor as a multilayer ceramic electronic component. In the following embodiments, a polyester resin, EVA (ethylene-vinyl acetate copolymer) resin, polyamide resin, and polypropylene resin having a Tg of 30 ° C. or lower are collectively referred to as a highly crystalline resin. I write.

  First, a dielectric slurry is prepared by adding a butyral resin having a molecular weight of 20,000 to 200,000 to a ceramic raw material, and adding a polyester resin having a molecular weight of 5,000 to 50,000 as a highly crystalline resin and sufficiently dispersing in a butyl acetate solvent, Using this dielectric slurry, a dielectric green sheet having a thickness of about 1.6 μm was prepared by a doctor blade method.

Next, after forming a pattern of internal electrodes on the dielectric green sheet by screen printing, when the printed internal electrodes are separated into pieces, a pair of external electrodes are alternately formed on both end faces of the pieces. While aligning so that it could be connected, 300 laminated laminates were produced. The lamination conditions were a temperature of 70 to 130 ° C. and a pressure of 80 to 120 kgf / cm ² .

  The obtained multilayer body was separated into individual pieces, then treated to remove the binder and fired in a reducing atmosphere, and then a pair of external electrodes were formed to obtain a multilayer ceramic capacitor.

  Hereinafter, specific examples will be described.

Example 1
Using 100 parts of ceramic material mainly composed of barium titanate, using 8 parts of butyral resin and 5 parts of polyester resin (Tg: −10 ° C.) as a high crystalline resin A dielectric green sheet was prepared.

  Then, using this dielectric green sheet, a laminate was obtained under the conditions described above, and after the laminate was separated into pieces, binder removal and firing were performed to produce a sintered body, and external electrodes were formed. Thus, a multilayer ceramic capacitor was produced.

(Example 2)
8 parts of butyral resin was used for 100 parts of the ceramic material mainly composed of barium titanate, and 5 parts of polyester resin (Tg: −20 ° C.) was used as the highly crystalline resin. Otherwise, a multilayer ceramic capacitor was produced by the same method as in Example 1.

(Example 3)
8 parts of butyral resin was used for 100 parts of the ceramic material mainly composed of barium titanate, and 5 parts of polyester resin (Tg: 30 ° C.) was used as the highly crystalline resin. Otherwise, a multilayer ceramic capacitor was produced by the same method as in Example 1.

(Comparative Example 1)
8 parts of butyral resin was used for 100 parts of the ceramic material mainly composed of barium titanate, and 2.5 parts of butylbenzyl phthalate was used as a plasticizer instead of the highly crystalline resin. Otherwise, a multilayer ceramic capacitor was produced by the same method as in Example 1.

(Comparative Example 2)
8 parts of butyral-based resin was used for 100 parts of the ceramic material mainly composed of barium titanate, and 5 parts of butylbenzyl phthalate was used as a plasticizer instead of the highly crystalline resin. Otherwise, a multilayer ceramic capacitor was produced by the same method as in Example 1.

(Comparative Example 3)
8 parts of butyral resin was used for 100 parts of the ceramic material mainly composed of barium titanate, and 5 parts of polyester resin (Tg: 35 ° C.) was used as the highly crystalline resin. Otherwise, a multilayer ceramic capacitor was produced by the same method as in Example 1.

With respect to the multilayer ceramic capacitors produced according to Examples 1 to 3 and Comparative Examples 1 to 3, BDV _ave (average value of dielectric strength) and the short-circuit rate were measured for each 500 pieces. The results are shown in (Table 1).

As apparent from (Table 1), in Examples 1 to 3 containing a highly crystalline resin having a Tg of 30 ° C. or less as a constituent component of the green sheet, those of Comparative Examples 1 and 2 in which a plasticizer was added to a butyral resin. It can be seen that a higher elastic modulus (300 N / mm ² or more) can be achieved at room temperature, and a high strain at break (20% or more) can be achieved at the time of laminating and crimping, and the short-circuit rate can be as low as 15% or less. Moreover, about the comparative example 3 containing highly crystalline resin whose Tg exceeds 30 degreeC, it turns out that a fracture | rupture at break point becomes less than 20% and a short circuit rate increases.

  FIG. 1 is a graph plotting the relationship between the elastic modulus at normal temperature, the strain at break at the lamination temperature, and the short rate for each of Examples 1-3 and Comparative Examples 1-3. The elastic modulus and the strain at break are measured by a tensile tester using a green sheet having a thickness of 15 to 20 μm.

According to FIG. 1, the green sheet has an elastic modulus of less than 300 N / mm ² , and the short ratio is high, and the elastic modulus is 300 N / mm ² or more and the strain at break is 20% or more, the short ratio is low. It can be seen that even when the elastic modulus is high, the short-circuit rate is high for those having a strain at break of less than 20%.

This is because for the elastic modulus less than 300 N / mm ² , the influence of damage during the process, sheet collapse during lamination and sheet elongation becomes remarkable due to insufficient strength of the ceramic green sheet itself. This is because the strength is increased and the influence is less for those of mm ² or more. Even when the elastic modulus increases, the short-circuit rate increases when the strain at break at the lamination temperature is less than 20% because it becomes impossible to exhibit electrode level difference absorption and adhesion of the green sheet. .

(Embodiment 2)
The second aspect of the present invention will be described below with reference to the second embodiment.

  Specific examples of the plastic material (plasticizer) include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dinormaloctyl phthalate, diisononyl phthalate, dinonyl phthalate, Examples include diisodecyl phthalate, butyl benzyl phthalate, dioctyl phthalate, polyethylene glycol, glycerin, diisodecyl phthalate, diethyl phthalate, paraffin, and dibutyl phthalate.

Table 2 shows a comparison of the short-circuit rates of multilayer ceramic capacitors manufactured with and without a plasticizer as a constituent component of the green sheet. The process for manufacturing the multilayer ceramic capacitor is the same as that in the first embodiment, and the measurement method of BDV _ave (the average value of the withstand voltage) and the short-circuit rate was also performed in the same manner.

  As is clear from (Table 2), the short rate of the green sheet (Example 4) using the highly crystalline resin containing no plasticizer is good. The reason for this will be described with reference to FIG.

  FIG. 2 is a cross-sectional view of the multilayer ceramic capacitor according to the second embodiment.

  In FIG. 2, dielectric layers 1 and internal electrodes 2 are alternately stacked, and the internal electrodes 2 are alternately connected to a pair of external electrodes 3. Here, among the dielectric layers 1, the effective layer located on the outermost side with respect to the thickness direction of the multilayer ceramic capacitor is the upper outermost effective layer 4 and the lower is the lower outermost effective layer. 5.

  When the ceramic green sheet contains a plasticizer, the sheet is stretched at the time of laminating and crimping due to the creep phenomenon, and the thickness of the layer laminated first becomes thinner, and the thickness of the layer laminated last becomes the largest.

In fact, the film thickness growth rate (Table 2) (%) (film thickness elongation (%): 100 × 5 (thickness of the first laminated the lower outermost effective layer) - 4 (outermost on the last laminated comparing the film thickness of the active layer)) / 4 (the thickness of the outermost effective layer on laminated at the end), those ones containing a plasticizer to -7%, using high crystalline resin Sheet elongation is reduced by -0.5%. Thus, if the ceramic green sheet of this invention is used, since the thickness of the upper and lower outermost effective layers 4 and 5 can be made substantially the same, the increase in a short circuit rate and the fall of a dielectric strength voltage can be suppressed. Usually, the increase in the short-circuit rate and the decrease in BDV _ave are more likely to occur as the film thickness is thinner. Therefore, the green sheet of the present invention is effective for making the dielectric layer thinner. The film thickness elongation is preferably -5 to 0%.

(Embodiment 3)
The third aspect of the present invention will be described below with reference to the third embodiment. The process for producing the multilayer ceramic capacitor is the same as that of the first embodiment except that a heating process is performed before the ceramic green sheets are laminated.

  3A and 3B are perspective views showing a manufacturing process of the multilayer ceramic capacitor. FIG. 3A shows a cutting process, FIG. 3B shows a heating process, and FIG. 3C shows a multilayer crimping process.

In the cutting process of FIG. 3A, the ceramic green sheet 6 to which the internal electrode has been transferred is cut by the cutting machine 7 so as to have a size of 7 cm × 7 cm, and cut in the heating process shown in FIG. The ceramic green sheet 6 is heated by infrared rays with a heater 9 and the PET film as an unnecessary support is peeled off from the ceramic green sheet 6 and aligned. Then, in the laminating and crimping step shown in FIG. Lamination pressing is performed by the apparatus 11. The pressure during lamination here was 100 kgf / cm ² . Since the subsequent steps are the same as those in the first embodiment, a description thereof will be omitted. If the ceramic green sheet is heated to 60 ° C. or higher in advance as described above, the ceramic green sheet can easily absorb the step difference of the internal electrode and improve the adhesion during the subsequent lamination. In addition, it is preferable to perform a heating process and a lamination | stacking crimping | compression-bonding process continuously so that the temperature of a ceramic green sheet may not fall as much as possible, and the means which keeps the heated green sheet warm between a heating process and a lamination | stacking crimping | compression-bonding process. It is also possible to provide it.

  FIG. 4 is a diagram showing the required lamination pressure bonding time with respect to the temperature to be heated before laminating the ceramic green sheets. Here, the lamination pressure bonding time represents the shortest time required for the ceramic green sheet to absorb the step of the internal electrode and to adhere stably without peeling off the ceramic green sheet.

  As is apparent from FIG. 4, the lamination pressure bonding time can be significantly shortened by setting the heating temperature to 60 ° C. or higher. Therefore, the heating step shown in FIG. 3 (b) is provided immediately before the laminating and crimping step shown in FIG. 3 (c), and the heating temperature is set to 60 ° C. or higher so that the ceramic green sheet is bonded without peeling off. Thus, the lamination time is shortened, and a highly reliable multilayer ceramic capacitor can be manufactured efficiently.

  This is because in a process without normal heating, the temperature is raised during lamination, the green sheet becomes soft (exceeds the Tg of GS), and it takes time to develop lamination properties such as electrode step absorption and adhesion. On the other hand, when there is a heating step, a certain degree of lamination property is exhibited in the heating stage, and the lamination pressure bonding time can be shortened.

  In the present invention, the above-described resins are exemplified as the highly crystalline resin. However, any highly crystalline resin can be used and has the same effect.

  In this embodiment, a multilayer ceramic capacitor is used as an example. However, the present invention is not limited to this. For example, a multilayer ceramic electronic formed by stacking green sheets such as a multilayer inductor, an LC filter, or a noise filter is used. It can also be used for parts.

  The ceramic green sheet according to the present invention has an effect of suppressing an increase in a short-circuit rate and a decrease in a withstand voltage when the dielectric layer is thinned. In particular, the ceramic green sheet is thinned, increased in capacity, or highly reliable. This is useful for monolithic ceramic electronic components that require characterization.

Diagram showing the relationship between elastic modulus, strain at break and short rate of ceramic green sheet Sectional drawing of the multilayer ceramic capacitor in Embodiment 2 of this invention The perspective view which showed the manufacturing process of the multilayer ceramic capacitor in Embodiment 3 of this invention Diagram showing the relationship between the heating temperature of the ceramic green sheet and the lamination pressure bonding time

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dielectric layer 2 Internal electrode 3 External electrode 4 Upper outermost effective layer 5 Lower outermost effective layer 6 Ceramic green sheet 7 Cutting machine 9 Heating machine 11 Thermocompression bonding apparatus

Claims (6)

Selected from the group consisting of ceramic raw material, butyral resin or acrylic resin, and polyester resin, EVA (ethylene-vinyl acetate copolymer) resin, polyamide resin, and polypropylene resin having a Tg of 30 ° C. or less. at least one only contains,
A ceramic green sheet characterized by an elastic constant at room temperature of 300 N / mm ² or more in tensile strength and a strain at break at a lamination temperature of 20% or more. Selected from the group consisting of ceramic raw material, butyral resin or acrylic resin, and polyester resin, EVA (ethylene-vinyl acetate copolymer) resin, polyamide resin, and polypropylene resin having a Tg of 30 ° C. or less. Including at least one
In tensile strength, the elastic constant at room temperature is 300 N / mm ² As described above, a ceramic green sheet having a breaking strain at 70 ° C. to 130 ° C. of 20% or more. The ceramic green sheet according to claim 1, wherein a plasticizer is not added. The multilayer ceramic electronic component using the ceramic green sheet as described in any one of Claims 1-3. Selected from the group consisting of ceramic raw material, butyral resin or acrylic resin, and polyester resin, EVA (ethylene-vinyl acetate copolymer) resin, polyamide resin, and polypropylene resin having a Tg of 30 ° C. or less. Including at least one
A multilayer ceramic electronic component having a film thickness elongation of -5 to 0% obtained by dividing a difference between a film thickness of a lower outermost effective layer and a film thickness of an upper outermost effective layer by a film thickness of an upper outermost effective layer. A method for manufacturing a multilayer ceramic capacitor, comprising: heating the ceramic green sheet according to any one of claims 1 to 3 to 60 ° C. or more and then stacking the ceramic green sheets.

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