JPH04127410A - Manufacture of ceramic laminated body - Google Patents

Abstract

PURPOSE:To obtain the manufacturing method of a ceramic laminated body whose heating time is short, which does not cause a delamination, whose cost is low and whose quality is high by a method wherein, after a pressed body has been heated and an organic binder has been removed at a heating process, the pressed body is cooled and a pressure is exerted in an isotropic direction at a temperature near room temperature. CONSTITUTION:The prescribed number of green sheets is laminated at a lamination process; after that, the laminated green sheets are put into a press metal mold, pressurized and thermocompression-bonded at a thermal pressing process. Then, in order to remove a binder contained in this pressed body, the pressed body is heated at a first heating process. A delamination is caused at the pressed body as the binder is removed. In order to restore the delamination, a pressure is exerted on the pressed body at a cold isotropic-pressure pressing process. Then, the pressed body is again put into an electric furnace at a second heating process and is heated. After that, it is cooled down to room temperature; a sintered body is obtained. By this method, it is possible to form a ceramic laminated body which can shorten the time required for its manufacture, whose cost is low and whose quality is good without an interlayer exfoliation or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ceramic laminate, and particularly to a method for manufacturing a ceramic laminate used in a multilayer ceramic electrostrictive element, a multilayer ceramic capacitor, and the like.

[Conventional technology]

The structure and manufacturing method of a conventional ceramic laminate will be described using a slit-structured multilayer ceramic electrostrictive element (hereinafter referred to as slit-type element) as an example.

Generally, an electrostrictive element is a transducer that converts electrical energy into mechanical energy by utilizing the electrostrictive effect of a solid such as ceramic.

As the structure of this electrostrictive effect element, a laminated structure in which thin layers of electrostrictive material are alternately laminated with internal electrodes is widely used so that large mechanical energy can be obtained with a low voltage.

In particular, as disclosed in Japanese Patent Application Laid-Open No. 58-196077, the slit type element is manufactured by providing a slit parallel to the internal electrodes on the side surface parallel to the lamination direction of the laminated electrostrictive effect element. This increases the mechanical strength when applying voltage to the element to drive it.

Below, regarding the structure of the slit type element shown in Fig. 3,
This will be explained based on an embodiment of Japanese Patent Application Laid-Open No. 58-190677.

In this slit type element, ceramic layers 1 as electrostrictive materials and internal electrodes 2a and 2b are alternately laminated.

Furthermore, external electrodes 3a and 3b are provided on a pair of side surfaces parallel to the stacking direction.

The internal electrodes are distributed for each layer so as to be connected to the external electrode on the left side or the right side, and the internal electrode 2a is connected to the external electrode f.
i3a, and the internal electrode 2b is connected to the external electrode 3b.

In such a structure, when a voltage is applied to the lead wires 4a and 4b from the outside, the adjacent internal electrodes become opposite electrodes with the ceramic layer 1 in between, so that large mechanical energy can be obtained with a low voltage. .

This slit-type element further has several slits 5 parallel to the internal electrodes on four side surfaces parallel to the stacking direction.

This slit 5 is the boundary (indicated by C in the figure) between the part where no displacement occurs (indicated by A in the figure) and the part where displacement occurs (indicated by B in the figure) when a voltage is applied to the slit-type element.
This has the effect of alleviating the large stress concentrated on the slit element and increasing the mechanical strength of the slit element during operation.

The conventional manufacturing process of the above-mentioned slit type element will be explained below based on an example of Japanese Patent Application Laid-Open No. 115606/1983.

FIG. 4 shows a process diagram of a conventional manufacturing process for a slit-shaped element.

This slit-type element is manufactured by first adding an organic binder and an organic solvent to electrostrictive material powder and kneading them to form a slurry in a slurry manufacturing process.

Next, in a tape casting step, a green sheet is obtained by tape casting.

Next, in an internal electrode/cutting line printing step, internal electrode pastes 6a and 6b having patterns as shown in FIGS. 5(b) and 5(c) are screen printed on this green sheet.

In addition, in this step, a green sheet is separately prepared on which only the cutting line paste 7 having a pattern as shown in FIG. 5 (a>) is printed.

These green sheets are used to indicate the positions at which the press body will be cut in a later step, and several green sheets are placed on the top of the press body.

Furthermore, in a separate pore-forming material printing step, a pore-forming paste 8 having a pattern as shown in FIG. 5(d) is screen-printed.

Although this pore-forming paste 8 decomposes and scatters and disappears in the heating step described later, it acts as a temporary filler for the portion that will eventually become the slit 5 shown in FIG. 3.

Next, in the lamination process, a predetermined number of each of the green sheets processed as described above is laminated, and in the heat press process, they are heated to a temperature that softens the binder, and then thermocompressed using a -axis processing press. A press body as shown in Fig. 6 is prepared.

This pressed body has a laminated structure in which one green sheet printed with hole-forming paste 8 is arranged for every four green sheets printed with internal electrode pastes 6a and 6b.

The top few sheets are green sheets printed with cutting line paste 7.

Next, in a heating step, this pressed body is heated to thermally decompose and remove the binder and pore-forming paste, and then the internal electrodes and ceramic are sintered to form a sintered body.

After that, in the polishing process, the top and bottom surfaces are polished to make them parallel, and then in the cutting process, the device is cut into the shape of the device, and the slit-shaped device is completed through the external electrode forming process and the lead edging process. do.

[Problem to be solved by the invention]

In the manufacturing process of the slit type element described above, the following occurs during the heating process.

That is, when the press body is heated and the temperature of the press body reaches the decomposition temperature of the molding binder contained in the press body, the binder decomposes and a large amount of decomposed gas is generated.

This decomposed gas reaches the surface from the inside of the press body and scatters, but at this time, if the surface area of the press body (i.e. the exit of the decomposed residue) is narrow, the decomposed gas stagnant inside the press body causes the press body to internal pressure increases.

As the binder decomposes further, the decomposed gas inside the press body will pass through the interface between the electrostrictive material and the internal electrode or the interface between the electrostrictive material and the pore-forming paste, which have relatively weak adhesion in the press body. By expanding this part, the so-called
Peeling between the eyebrows (delamination; hereinafter referred to as delamination) becomes more likely to occur.

This phenomenon is more pronounced as the outlet for the cracked gas is narrower relative to the amount of cracked gas generated.

This means that the larger the shape of the press body, the more
This indicates that delamination is more likely to occur because the ratio of the surface area to the volume of the pressed body becomes smaller.

However, in the above-mentioned slit-shaped element, the shape of the pressed body must be quite large. For example, - As an example, length 10011 x width 70 nm x height 12
It can be extremely large, such as am.

Regarding the height, this dimension is necessary to ensure the amount of displacement generated as an electrostrictive effect element, and regarding the length and width, it is necessary to improve the accuracy of the parallelism of the upper and lower surfaces during polishing after sintering. This is the size necessary to achieve a reasonably large area in order to increase production efficiency.

Moreover, the shape of the press body tends to become larger and larger in view of the improvement in performance of the slit-shaped element and the increase in production efficiency.

That is, in the conventional manufacturing method of a slit type element, delamination is very likely to occur during the heating process.

As a method for avoiding this delamination phenomenon, there is a method of slowing down the temperature increase rate near the decomposition temperature of the binder.

However, when this method is applied to a pressed body with the above-mentioned shape and dimensions, it is necessary to raise the temperature at an extremely slow rate of 1.0°C/h, which requires a total heating time of about 20 days. Another problem arises in that productivity is poor.

The problems described above do not only occur in the manufacturing process of slit-type elements, but also occur in the manufacturing process of other types of multilayer ceramic electrostrictive elements and multilayer ceramic capacitors. .

The purpose of the present invention is to improve the drawbacks of the conventional method for manufacturing ceramic laminates as described above, and to achieve an inexpensive manufacturing method that requires less heating time to remove the binder and is less likely to cause delamination. Our goal is to provide high-quality ceramic laminates.

[Means to solve the problem]

The method for manufacturing a ceramic laminate according to claim 1 includes forming a conductive layer on one surface of a ceramic green sheet;
A step of laminating electrode sheets cut into predetermined dimensions to obtain a pressed body, and heating the pressed body to remove the organic binder contained in the pressed body, followed by further heating to a high temperature and sintering. In the method for manufacturing a ceramic laminate, the heating step includes heating the pressed body to remove the organic binder, and then cooling the pressed body and applying pressure in an isodirectional manner at around room temperature. Features.

Further, the method for manufacturing a ceramic laminate for a slit-type electrostrictive element according to claim 2 includes: an electrode sheet formed by forming a conductor layer on one surface of a ceramic green sheet and cutting it into a predetermined size; A step of forming a layer of a pore-forming material on one side of a ceramic green sheet and laminating a pore-forming sheet formed by cutting the ceramic green sheet into a predetermined size to obtain a pressed body, and heating and pressing the pressed body. In the method for manufacturing a ceramic laminate for a slit-type electrostrictive element, the method includes a heating step of removing the organic binder and pore-forming material layer contained in the body, and then further heating to a high temperature and sintering. In the heating process, after the pressed body is heated to remove the organic binder, the pressed body is cooled with a layer of pore-forming material remaining, and pressure is applied isodirectionally at around room temperature. .

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a process diagram showing the manufacturing process of an embodiment of the present invention.

In addition, in the following explanation, in the part related to the manufacturing process, the first
In addition to the figures, reference is also made to FIG. 2(a), FIGS. 5(a) to (d), and FIG. 6.

In this embodiment, a lead zirconate titanate ceramic is selected as the electrostrictive material, and in the slurry manufacturing process, an organic binder and an organic solvent are added to this material powder and kneaded to form a slurry. Polyvinyl butyral is used as the binder.

Next, in a tape casting step, this slurry is tape cast onto a film using a doctor blade method to produce a green sheet.

The thickness of this green sheet is 130 μm.

Next, in an internal electrode/cutting line printing process, an internal electrode paste 6 containing a silver/palladium alloy as a main component is screen printed on this green sheet.

The printing pattern is the pattern shown in FIGS. 5(b) and 5(c).

Also, in this step, a green sheet on which only the cutting line paste 7 is screen printed is separately prepared.

The printing material is a paste whose main components are silver and palladium, like the internal electrode paste, and the printing pattern is the pattern shown in FIG. 5(a).

Furthermore, in a separate pore-forming material printing step, a pore-forming paste 8 containing graphite as a main component is printed.

The printing pattern is the pattern shown in FIG. 5(d).

Thereafter, in a sheet cutting process, each green sheet is cut into a 100+nm x 70 dragon shape.

Next, a predetermined number of green sheets processed as described above are laminated in an 11I layer process, and then in a hot press process, after being put into a press mold, it is heated to 110°C and 300kgf/co
The press body shown in FIG. 6 is obtained by applying pressure at t and thermocompression bonding.

The height of this press body is 12 mm.

Next, the press body is heated in a first heating step in order to remove the binder contained in the press body.

The temperature profile of this heating is shown in FIG. 2(a).

After heating to 350°C with a temperature gradient of 5°C/h and holding for 4 hours, it is cooled to room temperature at -50°C/h and taken out from the electric furnace.

At this point, the binder has been removed, but the pore-forming paste 8 still remains undecomposed.

Moreover, delamination occurs in the pressed body due to the removal of the binder.

In this example, in order to repair this delamination, a pressure of 2000 kgf/cTA is applied to the pressed body in the cold isostatic pressing process.

In this way, the delamination is repaired, but the portions that will later become slits retain their original form because the pore-forming paste 8 remains.

Next, in the second heating step, the press body is placed into the electric furnace again and heated.

At this time, the temperature is raised at a rate of 50'C/h up to 350°C, the temperature at which graphite, which is a pore-forming material, finishes decomposing (450°C).
℃), the temperature was raised at 5℃/h, and then the temperature was raised at 50℃/h to sinter the internal electrodes and ceramic.
After reaching 100'C, hold at this temperature for 4 hours. Thereafter, it is cooled to room temperature at -50''C/h to obtain a sintered body.

After this, in the polishing process, the sintered body is polished to make the upper and lower surfaces parallel, and in the cutting process, it is cut into elements of predetermined dimensions, and in the external electrode forming process, silver paste is baked to form external electrodes. , the lead wire diagram is made into a slit-type element through a process.

Next, in order to confirm the effects of this example, the results of a comparison between the slit type element manufactured according to the above-mentioned example and the slit type element manufactured by the conventional manufacturing method will be explained.

The slit-shaped element by the conventional manufacturing method was manufactured according to the process diagram shown in FIG. 4, and the temperature profile in the heating step was set to two types as shown in FIGS. 2(b) and 2(c).

In the above comparison, the materials used and the structure of the slit-shaped element were the same for both manufacturing methods.

In the conventional manufacturing method, the slit was made under the heating conditions 1 shown in Figure 2(b), that is, the temperature was raised to 450"C at a temperature increase rate of 5°C/h in the binder removal and pore forming material removal steps. When 600 mold elements were produced, the yield rate with respect to occurrence of delamination was 7%.

Further, using the same conventional manufacturing method, the yield rate of 600 devices was 100% under heating condition 2 shown in FIG. 2(c), that is, when the temperature increase rate was 1° C./h.

However, in this case, it took about 20 days to remove the binder and complete the firing.

On the other hand, in this example, the above heating process was completed in about 7 days, and the yield rate of 600 devices was 10.
It was 0%.

〔Effect of the invention〕

As explained above, according to the present invention, during the manufacturing process of the ceramic laminate, after removing the binder in the pressed body, pressure is applied to the pressed body in the same direction at around room temperature, and then firing is performed. As a result, it is possible to shorten the time required for manufacturing and increase the rate of non-defective products, so it is possible to provide a ceramic laminate of low cost and high quality without peeling between the eyebrows.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing the manufacturing process of an embodiment of the present invention, and FIGS. 3 is a longitudinal cross-sectional view showing the structure of the slit-type element, FIG. 4 is a process diagram showing the conventional manufacturing process of the slit-type element, and FIGS. 5(a) to 5(d) are diagrams showing the profile. FIG. 6 is a longitudinal cross-sectional view showing the structure of the pressed body of the slit-shaped element. . 1... Ceramic layer, 2a, 2b... Internal electrode, 3
a, 3b...external electrode, 4a, 4b...lead wire,
5... Slit, 6a, 6b... Internal electrode paste, 7... Paste for cutting line, 8... Hole forming paste.

Claims (3)

[Claims] 1. A process of forming a conductor layer on one side of a ceramic green sheet and stacking electrode sheets cut to a predetermined size to obtain a pressed body; In the method for manufacturing a ceramic laminate, the method includes a heating step of heating the pressed body to a higher temperature and sintering the organic binder after removing the organic binder from the press. A method for manufacturing a ceramic laminate, characterized by cooling the body and applying pressure in an isodirectional manner at around room temperature. 2. An electrode sheet is formed by forming a conductor layer on one side of a ceramic green sheet and cutting it to a specified size, and an electrode sheet is formed by forming a layer of pore-forming material on one side of a ceramic green sheet and cutting it to a specified size. and heating the pressed body to remove the layer of organic binder and pore-forming material contained in the pressed body, followed by further heating to a high temperature. In the method for manufacturing a ceramic laminate for a slit-type electrostrictive element, the heating step includes heating the pressed body to remove the organic binder, and then forming a layer of pore-forming material. A method for manufacturing a ceramic laminate for a slit-type electrostrictive effect element, characterized in that the pressed body is cooled while the pressed body remains, and pressure is applied isodirectionally at around room temperature. 3. The method for manufacturing a ceramic laminate according to claim 1 or 2, wherein the method of applying pressure to the pressed body in an isodirectional manner at around room temperature is a cold isostatic pressing method. Production method.