JPH04148576A - Manufacture of ceramic laminate - Google Patents

Abstract

PURPOSE:To increase the tensile strength and bend resistance of an electrostrictive element by laminating electrode units, each consisting of two sheets with their conducting surfaces in contact, so as to prevent the failure due to breaks of electrodes in the laminate. CONSTITUTION:Conductive past is printed on a green sheet and dried to form a conductive layer 2. The green sheet is cut into pieces of a specified size to provide electrode sheets 4, which are laminated with dummy sheets 5. The electrode sheets are paired to prepare electrode units, each unit being formed by put one sheet on the other with their conductive layers faced. First, dummy sheets 5 (e.g. 50 sheets) are stacked, and this laminate is stucked on 50 electrode units. In this structure, adjacent conductive layers are isolated by two ceramic layers. The laminated body 6a is heated to 100 deg.C and compressed at 250kg/cm<2> for 45 minutes. After heated to 400 deg.C to thermally decompose organic binder, the laminated body is sintered at 1100 deg.C for two hours.

Description

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

[Conventional technology]

Regarding the manufacturing method and structure of conventional ceramic laminates,
An explanation will be given using FIGS. 3 to 6, taking a laminated ceramic type electrostrictive effect element as an example.

A laminated ceramic type electrostrictive effect element converts electrical energy into mechanical energy by utilizing the piezoelectric longitudinal effect in a ceramic laminate, and generates minute displacement.
It is used in fields where it is necessary to precisely control the amount of movement of minute positions, such as X-Y tables in semiconductor integrated circuit manufacturing equipment, mass flow controllers, and optical systems in optical measuring instruments.

To manufacture the laminated ceramic electrostrictive effect element as described above, first, piezoelectric ceramic powder, an organic solvent, and an organic binder are mixed to form a slurry, and then this slurry is poured onto a polyethylene Lumirror sheet. Then, a green sheet is formed by a so-called tape casting method in which a uniform thin layer is formed using a doctor blade.

Next, as shown in FIG. 3, a conductor paste containing silver and palladium as main components is coated on the green sheet 1 by screen printing, leaving only a portion of the green sheet 1, to form a conductor of a constant thickness. Form layer 2.

Thereafter, the sheet obtained as described above is cut into predetermined dimensions to obtain an electrode sheet 4 consisting of the conductor layer 2 and the ceramic layer 3.

On the other hand, the green sheet on which the conductor layer is not attached is cut into the same size as the electrode sheet 4 to obtain a dummy sheet without the conductor layer.

Next, as shown in FIG. 4, the electrode sheet 4 and the dummy sheet 5 are sequentially laminated in a mold so that the surfaces of the conductive layer 2 are in the same direction, and pressed while heating to form a pressed body. Make 6a.

Note that the structure of the pressed body 6a is determined by the number and order of lamination of the electrode sheets 4 and dummy sheets 5. FIG. 4 schematically shows the structure.

Furthermore, the above-mentioned press body 6a is heated at 400°C in an electric furnace.
The organic binder contained in the press body is decomposed and scattered by slowly raising the temperature to a temperature of 1100°.
A sintered block is obtained by sintering at a high temperature of about C.

The sintered block that has gone through these steps is cut into a certain size to create a large number of ceramic laminates from one sintered block.

Next, as shown in FIG. 5, glass layers 8 are formed alternately every other layer by electrophoresis on the conductor layers 2 exposed on each of the pair of opposing side surfaces of the ceramic laminate 7. .

Next, external electrodes 9 are formed on this glass layer 8 to connect every other conductor layer 2 inside the ceramic laminate.

Finally, a lead wire 10 is soldered to this external electrode 9, and then an exterior is applied to complete the electrostrictive element 11.

[Problem to be solved by the invention]

As explained above, the conductive pair layer inside the ceramic laminate is mainly composed of metals such as silver and palladium, but in general, at high temperatures such as in the ceramic sintering process, the metal remains constant with respect to the ceramic. Causes a diffusion of quantity.

Furthermore, metals often shrink more than ceramics when sintered.

On the other hand, in the conventional manufacturing method described above, a screen printing method is used when forming a conductor layer on a green sheet, but there is a certain upper limit to the thickness of the conductor layer that can be formed by this screen printing method.

Although the upper limit of this film thickness varies depending on the screen printing method, printing conditions, etc., it is not easy to increase the thickness above a certain level.

For this reason, in the conventional manufacturing method of ceramic laminates, the amount of metal in the conductor layer on the ceramic layer is not sufficient to compensate for the diffusion and shrinkage of the conductor layer described above, and the amount of metal in the conductor layer after the sintering process is insufficient. As shown in FIG. 6, the result is a mesh-like shape.

FIG. 6 is a photograph of the surface state of the conductor layer 2 of the ceramic laminate produced by the conventional manufacturing method, magnified 400 times using an optical microscope.

If the conductive layer inside the ceramic laminate has a mesh shape as shown in FIG. 6, the contact area between the ceramic layer and the conductive layer becomes small, and the adhesion strength between the two decreases.

As a result, a disadvantage arises in that the tensile strength of the ceramic laminate is reduced.

Furthermore, due to slight variations in the manufacturing conditions of the overall process, such as the thickness of the conductor layer and the sintering temperature, the conductor layer may break inside the ceramic laminate, so-called electrode breakage, which makes it impossible to make an effective electrode sheet. Since the number of calendars decreases, the yield decreases.

Furthermore, the surface condition of the green sheet produced by the tape casting method differs in surface roughness between the surface that was in contact with the luminar sheet and the open surface when the green sheet was produced.

As a result, when electrode sheets are stacked to form a ceramic laminate, the adhesion strength between the conductor layers sandwiching the ceramic layer and the ceramic differs between the upper and lower sides of the ceramic layer.

In FIG. 3, when making the electrode sheet 4, the conductor layer 2 is printed on the above-mentioned open surface, and the metal particles of the conductor layer 2 formed on this open surface are inserted into the ceramic particles. It penetrates and provides sufficient adhesion strength due to its anchor effect.

On the other hand, the surface of the green sheet that was in contact with the Lumirror sheet comes into contact with the conductor layer of another electrode sheet for the first time during lamination, and the anchor effect does not work sufficiently, so the conductor layer 2 and the ceramic layer The adhesion strength between 3 and 3 is weak.

This is one of the reasons why the ceramic laminate cannot have high mechanical strength such as tensile strength.

Furthermore, in the conventional method of manufacturing a ceramic laminate, since the ceramic layer between the conductor layers inside the ceramic laminate is a single layer, it is easily affected by pinholes, etc. Short circuits between conductor layers are likely to occur.

[Means to solve the problem]

The ceramic laminate according to the present invention includes a process of forming a conductive layer on one side of a green sheet made of ceramic powder and an organic binder and cutting it into a predetermined size to obtain an electrode sheet, and a process of laminating the electrode sheets. In the method for manufacturing a ceramic laminate, the lamination step includes a structure in which a second electrode sheet is arranged on the first electrode sheet so that each conductor layer faces and contacts each other in a repeating unit. It is characterized by being laminated so that

〔Example〕

Next, the present invention will be explained with reference to FIGS. 1, 2, and 5.

First, a multi-component solid solution piezoelectric ceramic powder having a perovskite crystal structure was dispersed and mixed in an organic solvent together with an organic binder powder to form a slurry.

This slurry was cast into a silicone-coated polyethylene sheet by tape casting to produce a green sheet with a thickness of about 50 μm, which is half the thickness of a conventional green sheet.

Next, approximately 10 μm of conductive paste with a silver to palladium ratio of 723 is screen printed onto this green sheet.
A conductor layer was formed by printing to a thickness of m and drying.

This green sheet was cut to a rated size to make an electrode sheet, and a dummy sheet was also made, and this electrode sheet and dummy sheet were laminated in a mold.

In the lamination, as shown in FIG.
After that, two electrode sheets 4 were put together so that the conductor layers 2 faced each other, and five layers were laminated as one unit.Furthermore, 50 dummy sheets 5 were laminated.

The reason why the thickness of the green sheet was made half of the conventional thickness is as follows.

When the conductive layers 2 of the electrode sheets 4 are laminated so that they are in contact with each other, two ceramic layers are formed between one conductive layer and the next conductive layer.

Therefore, if the thickness of the green sheet is the same as the conventional one, the thickness of the ceramic layer after lamination will be twice that of the conventional one.

To avoid this, the thickness of the green sheet was reduced to 1/2 of the conventional thickness.
2, and the distance between the conductor layers was made to be the same as the conventional one.

The pressed body 6b laminated in this way was heated to 100°C and pressed at a pressure of 250 kg/cm2 for 45 minutes, then, after thermally decomposing the organic binder at 400''C, it was heated at 1100''C for 2 hours. A sintered block was created by time sintering.

Next, after cutting this sintered block into a ceramic laminate, a glass layer 8 is formed on the exposed portion of the conductive layer 2 as shown in FIG. 5 by the same process as the conventional manufacturing process. External electrodes 9 are formed thereon.

Thereafter, a lead wire 1o was soldered to this external electrode 9, and then an exterior was applied to complete the electrostrictive element 11.

In the electrostrictive effect element 11 manufactured in this way,
The defective rate due to electrode breakage was 0%, whereas it was 3 to 8% in electrostrictive elements manufactured by conventional manufacturing methods.

Moreover, both the tensile strength and the bending strength were about 1.5 times higher than those of the electrostrictive effect element produced by the conventional manufacturing method.

FIG. 2 shows the surface condition of the conductor layer 2 of the ceramic laminate according to this example.

FIG. 2 is a photograph of the surface of the conductor layer 2 of the ceramic laminate according to this example, magnified 400 times using an optical microscope.

It can be seen that, compared to the surface condition of the conductor layer of the ceramic laminate produced by the conventional manufacturing method shown in FIG. 6, the conductor layer according to this example is formed more densely.

It is believed that this was effective in reducing defects caused by electrode breakage and improving the mechanical strength of the electrostrictive effect element.

Further, in the electrostrictive effect element manufactured by the conventional manufacturing method, short-circuit defects between the conductive layers occur in several percent, whereas in this example, the short-circuit failure occurred in 0%.

Short-circuit defects occur when there is a pinhole in the green sheet and a conductor layer is formed on top of it, and this pinhole creates a through hole in the conductor layer sandwiching the ceramic layer. Conceivable.

In this embodiment, since the ceramic layer between two adjacent conductor layers is formed of two layers, even if there is a pinhole in the green sheet, the probability of creating a through hole is very low.

Therefore, it is considered that no short-circuit failure occurred between the conductor layers.

In addition, although the above explanation was about an electrostrictive effect element,
It is clear that the present invention is not limited to this, and can also be applied to multilayer ceramic capacitors.

〔Effect of the invention〕

As explained above, the present invention uses two electrode sheets,
By aligning the conductive layers so that they are in contact with each other and stacking them as a unit, an anchor effect is created at both the upper and lower interfaces of the ceramic layer, and furthermore, the metal particles are attached to the ceramic layer during sintering. A conductive layer can be formed with a thickness that compensates for diffusion and shrinkage.

Therefore, defects caused by electrode breakage inside the ceramic laminate can be eliminated, and the tensile strength and bending strength of the electrostrictive element can be increased by about 50%.

Furthermore, since the ceramic layer between two adjacent conductor layers is formed of two layers, it is possible to eliminate short-circuit defects between the conductor layers due to pinholes in the green sheet.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the laminated structure of an embodiment of the present invention, Fig. 2 is an optical microscope photograph showing the surface state of a conductor layer in an embodiment of the present invention, and Fig. 3 is a diagram showing the surface state of a conductor layer in an embodiment of the present invention. FIG. 4 is a schematic diagram showing the method, and FIG. 4 is a diagram showing the laminated structure in the conventional manufacturing method. FIG. 5 is a diagram showing the structure of the electrostrictive effect element.
The figure is an optical micrograph showing the surface condition of a conductor layer obtained by a conventional manufacturing method. 1... Green sheet, 2... Conductor layer, 3...
Ceramic layer, 4... Electrode sheet, 5... Dummy sheet, 6a, 6b... Pressed body, 7... Ceramic laminate, 8... Glass layer, 9... External electrode, 10
...Lead wire, 11...Electrostrictive effect element.

Claims (1)

[Scope of Claims] A process of forming a conductor layer on one side of a green sheet made of ceramic powder and an organic binder and cutting it into a predetermined size to obtain an electrode sheet, and a process of laminating the electrode sheets. In the method for manufacturing a ceramic laminate comprising: in the laminating step, a structure in which a second electrode sheet is arranged on the first electrode sheet so that each conductive layer faces and contacts becomes a repeating unit. A method for manufacturing a ceramic laminate, characterized in that the ceramic laminate is laminated in the following manner.