JP2001185439A - Method of manufacturing ceramic green sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a ceramic green sheet which, even when a green sheet is made thin, is superior in peelability, wherein both a front face and a peeling face (rear face) of the green sheet are smooth and the interior of the green sheet is also homogeneous without ununiformity due to coaggulation of a binder. SOLUTION: This method comprises a step of forming a precoat layer 12 by applying a binder solution containing an organic binder and a solvent or a ceramic slurry containing a ceramic powder and the solvent on a carrier film and drying by heating it stepwise from the room temperature to a temperature not less than the evaporation temperature of the solvent, and a step of applying the ceramic slurry containing the ceramic powder and the solvent on the precoat layer 12 and drying by heating it stepwise from the room temperature to a temperature not less than the evaporation temperature of the solvent in stepwise.

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 ceramic green sheet, and more particularly to a method for manufacturing a ceramic green sheet suitably used for a multilayer electronic component such as a multilayer substrate, a multilayer ceramic capacitor, a multilayer actuator, and a piezoelectric transformer. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Conventionally, a ceramic laminate, for example, a multilayer ceramic capacitor, has been manufactured by the steps described below. First, a solution in which an adhesive resin called an organic binder is dissolved in an organic solvent is mixed with a slurry in which ceramic powder is dispersed in an organic solvent, to produce a ceramic slurry.

[0003] The produced ceramic slurry is coated on a carrier film such as a PET film by a molding method such as gravure coater, microgravure, reverse coater, die coater, etc., dried, and dried on a ceramic green sheet (hereinafter referred to as ceramic green sheet). , A green sheet). Conventionally, the thickness of a green sheet used in a multilayer ceramic capacitor is about 5 to 20 μm.

[0004] Then, Ni, A
An internal electrode paste containing g, Pd and the like is printed by screen printing or the like to form an internal electrode pattern, a plurality of green sheets on which the internal electrode pattern is formed are laminated, cut into a predetermined shape, and then subjected to a binder removal step. Then, through a firing step, external electrodes that are electrically connected to the internal electrodes are formed to obtain a multilayer ceramic capacitor.

In recent years, as electronic components have become smaller and larger in capacity, it has become necessary to reduce the thickness of the green sheet, and a green sheet having a thickness of 4.0 μm or less has been required.

However, the conventional method of manufacturing a green sheet has a problem that it becomes difficult to peel off the green sheet from the carrier film when the required film thickness is reduced. Such a difficult-to-peel green sheet has a problem in that the green sheet is torn, peeled, and the like at the time of peeling due to a decrease in tape strength due to a reduction in film thickness, and thus lamination is impossible.

For this reason, a carrier film which has been subjected to a so-called light peeling treatment in which the surface of the carrier film is processed so that the green sheet can be easily peeled off has been developed. However, due to the light release treatment of the carrier film, the wettability of the ceramic slurry to the carrier film deteriorates, causing defects such as pinholes and film breaks in the green sheet, and roughening the surface of the green sheet. Sex problems are emerging.

[0008] Even if the green sheet can be peeled by such light peeling treatment, when a multilayer ceramic capacitor is manufactured, the opposing internal electrodes are short-circuited through pinholes in the dielectric layer therebetween. And the withstand voltage is reduced without causing a short circuit.

Therefore, in recent years, when forming a green sheet on a carrier film, the ceramic slurry is applied in two layers, thereby eliminating defects in the green sheet and improving the releasability. (Japanese Patent Application Laid-Open No. H11-144998).

In this method, the ceramic slurry applied in the first coating is raised from room temperature to a high temperature of 80 ° C. at a stretch, and dried in a short time to increase the surface roughness but improve the releasability. In the second coating, a ceramic slurry is applied on the sheet obtained in the first coating, and dried at a lower temperature than the first coating to fill the pinholes of the first coated sheet, This is a method of improving the surface roughness of the green sheet.

[0011]

However, in the method for manufacturing a green sheet as disclosed in Japanese Patent Application Laid-Open No. 11-144992, the drying temperature in the first coating is raised from room temperature to a high temperature of 80 ° C. at once. As a result, the solvent in the ceramic slurry boils, and there is a problem that the smoothness of the peeled surface of the green sheet coming into contact with the carrier film is impaired.

That is, in Japanese Patent Application Laid-Open No. H11-144998, the roughening of the sheet surface in the first coating is described.
Although the problem can be solved by the application in the second coating, the back surface of the sheet in the first coating is not treated at all, and when the green sheet is peeled off from the carrier film, the back surface is roughened.

[0013] In addition, since an agglomerate of an organic binder is generated due to rapid drying of the solvent, the inner structure differs between the upper half and the lower half of the green sheet formed by the first coating and the second coating. There is a problem that non-uniformity occurs. When a monolithic ceramic capacitor is manufactured using such a green sheet, particularly a green sheet having a thickness of 3.5 μm or less, the unevenness increases a short circuit between opposing internal electrodes or lowers a withstand voltage. There was a problem that caused.

According to the present invention, the green sheet has excellent releasability even when it is thinned, and the surface and the release surface (rear surface) of the green sheet are smooth, and the inside of the green sheet is uniform without unevenness due to binder aggregates. An object of the present invention is to provide a method for manufacturing a green sheet.

[0015]

According to the method for producing a ceramic green sheet of the present invention, a binder solution containing an organic binder and a solvent or a ceramic slurry containing a ceramic powder, an organic binder and a solvent is coated on a carrier film. A step of heating and drying stepwise from room temperature to a temperature equal to or higher than the evaporation temperature of the solvent to form a precoat layer, and applying a ceramic slurry containing a ceramic powder, an organic binder and a solvent on the precoat layer. And heating and drying stepwise from room temperature to a temperature equal to or higher than the evaporation temperature of the solvent.

In the present invention, the binder solution or the ceramic slurry applied on the carrier film is heated from room temperature to an evaporation temperature at which the solvent completely evaporates, the temperature is gradually increased, and the solution is gradually dried. Forming a uniform pre-coat layer with no surface due to boiling marks of the solvent due to rapid drying at high temperature, no roughening of the peeled surface, no sedimentation of organic binder due to long-time drying at low temperature, and no aggregation of organic binder it can.

Further, according to the method for manufacturing a green sheet of the present invention, since the wettability is poor on the carrier film subjected to the light release treatment, when a binder solution or ceramic slurry is applied, the coating film becomes porous. However, it is possible to form a precoat layer having no organic binder aggregates.

This porous pre-coat layer without binder agglomerates improves the wettability of the carrier film, and the coating film formed by the next coating process may be cut off due to the deterioration of the wettability. There is no pinhole, and the surface can be formed to a specified thickness without any surface roughness by a drying step of stepwise heating to a temperature higher than the evaporation temperature of the solvent.

Therefore, in the obtained green sheet, there are no defects such as pinholes, film breaks and the like, and no aggregates of the organic binder inside, that is, the green sheet is uniform, and the front and back surfaces have good smoothness and good releasability. It can be.

Here, the thickness of the precoat layer is preferably 1.5 μm or less. This is because the ceramic slurry formed by the main coat can close the pinhole of the precoat layer.

The thickness of the ceramic green sheet is preferably 5 μm or less, particularly preferably 3.5 μm or less. This is because if the thickness is 5 μm or more, the number of internal defects decreases, and the effect of the above method becomes unnecessary.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for producing a ceramic green sheet according to the present invention, first, a binder solution containing an organic binder and a solvent or a ceramic slurry containing a ceramic powder, an organic binder and a solvent is applied onto a carrier film. Then, it is heated and dried stepwise from room temperature to a temperature equal to or higher than the evaporation temperature of the solvent to form a precoat layer.

The binder solution contains an organic binder and a solvent, and is a solution in which the organic binder is dissolved in the solvent. Here, the solvent used is desirably the same as the solvent used for the ceramic slurry for forming the green sheet.

Since the precoat layer may have a thickness sufficient to adhere to the carrier film, the precoat layer may not be present as a complete film on the carrier film, but may be, for example, a porous film having holes in some places. . Considering the subsequent ceramic slurry application step, the precoat layer is desirably 1.5 μm or less because defects in the precoat layer are eliminated. Further, when a binder solution containing an organic binder and a solvent is used, the precoat layer is 0.1 to 0.5 μm because the binder film does not induce defects during firing.
When a ceramic slurry containing an organic binder and a solvent is used, the precoat layer has a thickness of 0.1 μm because it contains ceramic particles having an average particle size of 0.5 μm or more.
It is desirable that the thickness be 5 to 1.5 μm.

The coating film is dried by heating stepwise from room temperature to a temperature equal to or higher than the evaporation temperature of the solvent. For example, heating is performed at room temperature, 60 ° C., and 80 ° C., which is higher than the solvent evaporation temperature.
By heating stepwise in this manner, the solvent is uniformly and gradually dried from the liquid slurry film, and the surface due to boiling marks of the solvent due to rapid drying at a high temperature and the peeled surface are not roughened.

Since the temperature in the final zone is equal to or higher than the evaporation temperature of the solvent, a uniform precoat layer free of organic binder sedimentation and organic binder agglomeration due to long-time drying at a low temperature can be formed.

Further, since the wettability is poor on the carrier film subjected to the light release treatment, when a binder solution or ceramic slurry is applied, the applied film becomes porous. A precoat layer free of organic binder aggregates can be formed.

After the pre-coat layer forming step, the main coat is performed. In this coating, a ceramic slurry containing a ceramic powder, an organic binder and a solvent is applied on the precoat layer obtained in the precoat layer forming step, and dried by heating stepwise from room temperature to a temperature equal to or higher than the evaporation temperature of the solvent. Then, a green sheet having a predetermined thickness is formed on the carrier film.

The thickness of the green sheet is controlled by applying the ceramic slurry on the main coat. The thickness of this green sheet is desirably 3.5 μm or less. Only when forming a green sheet having such a thickness of 3.5 μm or less, the use of the present invention is significant.

The ceramic slurry is a mixture of a ceramic powder and a solvent. The ceramic powder used in the precoat layer forming step is not necessarily the same as the ceramic powder of the ceramic slurry used in the present coat. However, it is desirable that they be the same for controlling the electrical characteristics of the electronic component.

For the drying in the main coat, if the solvent of the ceramic slurry is the same as the solvent in the precoat layer forming step, the drying temperature can be set to be the same.

FIG. 1 is a structural view showing an apparatus for manufacturing a green sheet according to the present invention. In FIG. 1, reference numeral 1 denotes a roll. A PET film as a carrier film is pulled out from the roll 1 and a ceramic film or a binder film formed on the PET film by the roll 2 is made of PET.
In the form of a roll-to-roll winding the whole film, a coating unit 3 for applying a ceramic slurry or a binder solution to the PET film and a drying unit 4 for drying the applied ceramic slurry or the binder solution are provided.

Here, the coating method in the coating unit 3 may be any of a tape forming device such as a doctor blade, a gravure roll, a reverse roll method and the like, as long as the layer can be thinned. It is sufficient that the above drying chamber is provided. In FIG.
a, 4b, and 4c are divided into three chambers, each of which can be set to an individual temperature.

First, in the step of forming a pre-coat layer, a ceramic slurry or a binder solution is applied to a predetermined thickness (for example, 1.5 μm for a ceramic film and 0.3 μm for a binder film) on a PET film in a coating section 3. Then, after drying in the drying unit 4, it is wound up by the roll 2.

At this time, hot air at room temperature is blown into the drying chamber 4a, and hot air at a temperature higher than the evaporation temperature of the solvent contained in the ceramic slurry or the binder solution (for example, if the evaporation temperature of the solvent is 80 ° C.) (100 ° C.). In the drying room 4b, for example, warm air was blown at an intermediate temperature of 60 ° C.

Thereafter, in this coating, the PET film on which the porous pre-coat layer formed by the roll 2 is formed is set again on the winding side of the roll 1, and a ceramic slurry is formed in the coating section 3. (For example, the total thickness of the ceramic slurry coating film is 3 μm), dried in the drying unit 4 and wound up by the roll 2 to obtain a desired green sheet. At this time, the drying conditions in the drying unit 4 can be the same drying temperature as long as the solvent of the ceramic slurry used in the main coat is the same as the solvent used in the step of forming the precoat layer.

If there are two green sheet manufacturing apparatuses, the precoat layer and the main coat can be continuously performed by connecting the apparatuses as shown in FIG. In FIG.
Reference numerals 5 and 10 are rolls, reference numeral 6 is a coating section in the precoat layer forming step, reference numeral 7 is a drying section in the precoat layer forming step, and reference numeral 8 is a ceramic slurry coating section in the main coating step. Reference numeral 9 denotes a drying unit in the main coating process. The drying unit 7 is, for example, room temperature, 60 ° C., 8
It has a drying chamber 7a, a drying chamber 7b, and a drying chamber 7c for heating to 0 ° C., respectively.
Drying room 9a, drying room 9 heated to 80 ° C. and 80 ° C., respectively.
b, a drying chamber 9c.

[0038]

Next, examples of the present invention will be described below. BaTi with average particle size of 0.4μm as ceramic powder
Using O ₃ powder, a ceramic slurry in which BaTiO ₃ powder was dispersed by a ball mill in a mixed solvent in which toluene and ethanol were mixed at a weight ratio of 1: 1 as a solvent was produced. The binder solution was prepared by dissolving butyral resin in the above mixed solvent at 8 wt%. Ceramic slurry is Ba
The above-mentioned binder solution was mixed at a 1: 1 weight ratio with ceramic slurry in which TiO ₃ powder was dispersed. Here, the evaporation temperature of the mixed solvent was about 80 ° C.

First, using a ceramic slurry for 1.5 μm
m of precoat layers were formed. That is, using a green sheet manufacturing apparatus as shown in FIG. 2, the above ceramic slurry is applied on a PET film in the coating section 6, and this coating film is dried at 25 ° C. in the drying chamber 7a and at 60 ° C. in the drying chamber 7b. The drying chamber 7c was heated in a stepwise manner in the drying unit 7 set at 100 ° C. and dried.

On the other hand, a 0.3 μm precoat layer was formed using a binder solution. The precoat layer was produced in the same manner as in the case of ceramic slurry.

In this coating, the ceramic slurry is applied on the two types of precoat layers in the coating section 8, and this coating film is dried at 25 ° C. in the drying chamber 9a.
In the drying section 9 in which b was set to 60 ° C. and the drying chamber 9c was set to 100 ° C., heating was performed stepwise and drying was performed. Further, both the precoat layer and the main coat of the examples of the present invention were applied by a doctor blade method.

The thickness of the entire green sheet layer was 3.0 μm and 3.5 μm when the ceramic slurry precoat layer was used, and 2.5 μm when the binder solution precoat layer was used.

An internal electrode pattern containing Ni is applied to the green sheet to form an internal electrode pattern. The green sheet on which the internal electrode pattern is formed is peeled off from the PET film, and 400 green sheets are laminated and vertically Green sheets on which no internal electrode pattern was formed were laminated, cut, degreased, and fired. Next, an external electrode paste was applied to both end surfaces of the sintered body and baked to form external electrodes, thereby producing 100 capacitors having a size of 2.0 mm long × 1.2 mm wide.

As a method for evaluating the obtained green sheet, first, the surface roughness (Ra) of the surface of the green sheet, the peeled surface (back surface), and the peelability of a square green sheet having a side of 20 mm as a peeling property are considered. The required force was measured by a 90 ° peel test, and the average value was calculated.

In order to evaluate the defects occurring in the green sheet, the short-circuit rate (N = 100) between the opposed internal electrodes of the manufactured capacitor was calculated, and the withstand voltage of the capacitor which did not short-circuit was measured ( N = 10), and the average value was calculated.

As a comparative example, in the precoat layer process, the temperatures in the drying chambers 7a, 7b and 7c of the drying unit 7 were all set to 80 ° C., and a 1.5 μm precoat layer was formed. Drying rooms 9a and 9b of the part 9;
The temperature at 9c was all set to 40 ° C. to obtain a green sheet having a thickness of 3.0 μm. Using this green sheet, a capacitor was manufactured in the same manner, and the evaluation of the green sheet and the capacitor was performed. The results are shown in Table 1.

Examples 1 and 2 are cases where a precoat layer is formed using ceramic slurry, and Example 3 is a case where a precoat layer is formed using a binder solution.

FIG. 3 is a cross-sectional view of a green sheet using the ceramic slurry precoat layer of Example 1,
FIG. 4 shows a cross-sectional view of the green sheet of the comparative example. FIG.
In FIG. 4, reference numeral 12 denotes a ceramic slurry precoat layer, and in FIG. 4, reference numeral 14 denotes a precoat layer, reference numeral 15 denotes an upper layer of the precoat layer, and reference numeral 16 denotes a binder aggregate.

[0049]

[Table 1]

According to Table 1, in the examples, a smooth green sheet having a surface roughness Ra of 63 nm or less was produced on both the surface and the peeled surface, and the peel force of the green sheet from the PET film was 1.1 kgf or less. Compared to the comparative example, there was no inferiority. In addition, since the smoothness of the green sheet was enhanced and the cross section of the green sheet of the example had no defects such as binder aggregates and pinholes as shown in FIG. It can be seen that the short-circuit rate was 0% and the withstand voltage was dramatically improved as compared with the comparative example.

On the other hand, the green sheet in the comparative example
Although the surface roughness is at the same level as that of the example, the surface roughness of the peeled surface is considerably rough. As shown in FIG. 4, the cross section of the green sheet of the comparative example has two layers due to the difference in drying temperature. The structure became uneven, and aggregates 16 of the binder were generated in the lower precoat layer 14.

Therefore, when a capacitor is evaluated using a green sheet having a thickness of 3.0 μm, it is found that more than half of the capacitors are short-circuited, and the withstand voltage is reduced even in a capacitor that has not been short-circuited.

[0053]

As described above, according to the present invention, even if the thickness of the green sheet is 3.5 μm or less, for example, the surface of the sheet and the peeled surface are smooth, and the aggregate of the binder In addition, a uniform green sheet free from defects such as pinholes can be easily manufactured, and the size and capacity of the multilayer electronic component can be further reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an apparatus for manufacturing a green sheet for carrying out a method for manufacturing a ceramic green sheet of the present invention.

FIG. 2 is a configuration diagram showing a state in which two green sheet manufacturing apparatuses are connected.

FIG. 3 is a cross-sectional view of the green sheet according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view of a green sheet of a comparative example.

[Explanation of symbols]

1, 2, 5, 10 ... Roll 3, 6, 8 ... Coating part 4, 7, 9 ... Drying part 4a, 4b, 4c, 7a, 7b, 7c, 9a, 9b, 9
c: Drying room 12: Pre-coat layer

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 5E001 AB03 AC09 AD04 AE02 AE03 AF06 AH01 AH05 AH06 AH08 AH09 AJ02 5E082 AA01 AB03 BC38 BC39 EE04 EE23 EE35 FF15 FG06 FG26 FG27 FG46 FG54 GG10 GG28 GG24 GG28 GG24 H0343

Claims (3)

[Claims] 1. A carrier solution containing a binder solution containing an organic binder and a solvent, or a ceramic slurry containing a ceramic powder, an organic binder and a solvent, is applied stepwise from room temperature to a temperature equal to or higher than the evaporation temperature of the solvent. Heating and drying to form a pre-coat layer, a ceramic slurry containing a ceramic powder, an organic binder and a solvent is applied on the pre-coat layer, and stepwise from room temperature to a temperature equal to or higher than the evaporation temperature of the solvent. And a step of drying by heating. 2. The method according to claim 1, wherein the thickness of the precoat layer is 1.5 μm or less. 3. The ceramic green sheet has a thickness of 3.5.
The method for producing a ceramic green sheet according to claim 1, wherein the thickness is not more than μm.