JPH0391221A - Green sheet for laminated ceramic capacitor - Google Patents

Abstract

PURPOSE:To obtain a green sheet having a flat surface by forming inner electrodes newly in gaps of the electrodes to become a recessed surface when a lower dielectric layer is formed, and further forming an upper dielectric layer thereon. CONSTITUTION:A dielectric layer 6a is formed on a base film 4 in which inner electrodes 5a are formed. Upper inner electrodes 5b are formed in gaps of the electrodes 5a corresponding to the recesses of the sheet, dried, upper dielectric layer 6b is further formed from above, and a green sheet is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a green sheet for a multilayer ceramic capacitor used in a multilayer ceramic capacitor.

BACKGROUND OF THE INVENTION In recent years, demand for multilayer ceramic capacitors has been increasing as electronic devices become smaller and operate at higher frequencies.

A general method for manufacturing a multilayer ceramic capacitor is to first prepare a green sheet by a doctor blade method using a slurry consisting of dielectric powder such as barium titanate, an organic binder, a plasticizer, and an organic solvent.

Next, internal electrodes are formed on this sheet by screen printing or the like using an electrode paste whose main component is a noble metal such as palladium or platinum.

Next, the green sheets with internal electrodes formed thereon are stacked one after another by arranging the internal electrode layers to alternately face each other with dielectric layers in between, and the molded body with the desired number of stacked layers is shaped into a chip of the desired size. After cutting at 120.0'C to 1400C, the bottom of the hole is drilled. The internal electrodes appearing at both ends of the sintered body thus obtained are coated with silver, silver palladium, etc. so that these internal electrodes are electrically connected, and baked to form external electrodes, and laminated. Manufactures ceramic capacitors.

On the other hand, in order to increase the capacitance of capacitors, it is necessary to make the dielectric layer thinner, but there is a limit to the thickness of the dielectric layer in the doctor blade method. Therefore, by increasing the amount of organic binder in the slurry and further reducing the slurry viscosity, we produced a thin sheet of 10 μm or less using a reverse roll method, etc., and applied heat and pressure from above the base film using a heating plate, etc. to prepare the sheet in advance. After thermally transferring a green sheet onto the dielectric layer and peeling off the base film, internal electrodes are printed on the film surface of the green sheet, and after drying, another green sheet is placed with the base film side facing up. A manufacturing method (hereinafter referred to as the hot stamping method) has recently been proposed in which the layers are placed in the same manner as described above, thermal transfer is performed in the same manner as above, and the layers are sequentially stacked until the desired number of layers are stacked.

Problems to be Solved by the Invention However, in the case of the hot stamping method that employs the manufacturing process as described above, due to the thickness of the internal electrode white, as the lamination progresses to a higher level, the part containing the internal electrode in the laminate molded product becomes thinner. This results in noticeable unevenness in the area around the area. At this time, the surrounding area that does not include the internal electrode becomes a recess, and sufficient pressure is not applied during lamination, and many cracks and delaminations occur in this area in the laminated molded body and the subsequent sintered body element. This is a major problem in the manufacture of multilayer ceramic capacitors.

Recently, in order to improve this problem, after forming the internal electrodes 2 on the base film 1 as shown in FIG. 2, a dielectric layer 3 is formed to embed the internal electrodes 2.
Green sheets with relatively flat surfaces (hereinafter referred to as embedded sheets) for the purpose of offsetting the thickness of the internal electrodes 2 have also been proposed (for example, in Japanese Patent Application Laid-Open No. 53-688
In such a structure, after drying the dielectric layer 3, the portion of the dielectric layer 3 corresponding to the upper part of the internal electrode 2 forms the convex portion A.
Therefore, the current situation is that basically the problem of flattening the green sheet has not been solved.

Therefore, in view of the above-mentioned problems, the present invention provides a green sheet for a multilayer ceramic capacitor with a flat surface that is not adversely affected by the unevenness of the molded body during stacking due to the thickness of the internal electrode during the production of multilayer ceramic capacitors. This is what we are trying to provide.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides that a dielectric layer is formed on a base film on which internal electrodes are formed, and that a dielectric layer is formed in the gap between the internal electrodes from above the dielectric layer. This device has a structure in which internal electrodes that are exactly the same as the internal electrodes described above are formed, and a dielectric layer that is exactly the same as the dielectric layer that is described above is formed thereon.

The present invention has a two-layered structure. When the lower dielectric layer is formed, a new internal electrode is formed in the gap between the internal electrodes whose surface has a concave portion, and the upper dielectric layer is further formed on top of the internal electrode. By forming this, it is possible to flatten the surface of the green sheet, eliminate the adverse effects of unevenness of the green sheet due to the thickness of the internal electrode even in high-order lamination, and obtain a good laminated molded product. This makes it possible to obtain a multilayer ceramic capacitor with a uniform thickness.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention in which a dielectric layer is formed on a base film on which internal electrodes have been formed in advance, and a dielectric layer is formed in the gap between the internal electrodes from above the electric layer to cover the internal electrodes (similar to the above). This figure shows a cross section of a green sheet in which after forming internal electrodes, a dielectric layer exactly the same as the dielectric layer described above was formed to flatten the surface.Here, 4 is the base film, and 5a is the lower part. 6a is the lower dielectric layer, 5b is the upper internal electrode, and 6b is the upper dielectric layer.

Next, an example of how to make a green sheet according to the present invention and a method of manufacturing a multilayer ceramic capacitor using the green sheet will be described. First, internal electrodes 5a having a desired pattern were formed on the base film 4 by screen printing using a commercially available internal electrode paste containing palladium as a main component.

Next, 100 parts by weight of barium titanate powder, 30 parts by weight of polyvinyl butyral resin, and 150 parts by weight of butyl calpitol.
parts by weight and 4 parts by weight of dioquidyl phthalate were mixed in a ball mill for 20 hours to prepare a slurry for the dielectric layer, and this slurry was used to coat the base film 4 on which the internal electrodes 5a prepared above were formed. A dielectric layer 6a was formed using a reverse roll method. After measuring the surface level difference of the embedded sheet obtained in this way with a contact type surface film difference meter, the upper internal electrode 5b is formed in the gap between the internal electrodes 5a corresponding to the recessed part of this sheet in exactly the same manner as described above, After drying, an upper dielectric layer 6b was further formed thereon in exactly the same manner as described above to obtain a green sheet of the present invention.

After measuring the surface level difference of the thus obtained green sheet in the same manner as described above, it was heated to 1800C using a heat press machine.
,15kg/cm? , The number of laminated layers was 60, according to the above-mentioned hot stamping condition for 2 seconds. A laminated cell, a laminated capacitor, was manufactured. When the lamination of these 60 layers was completed, the surface level difference of the molded body was measured in exactly the same manner as described above,
After cutting into chips, they were fired at 1300°C for 2 hours. Incidentally, in order to remove the binder during the process, the temperature was maintained at 350° C. for 6 hours. After the above firing, the occurrence rate of delamination of the obtained multilayer ceramic capacitor was calculated, and the results were compared to those shown in FIG. Using a green sheet that covers the internal electrode 2 only with a single dielectric layer 3,
The results were compared with the results obtained when a multilayer ceramic capacitor was manufactured using the same hot stamping method as described above.

The table below shows the surface level difference between the conventional embedded sheet and the sheet of the present invention in the green sheet state, the surface level difference of the molded body after lamination of 60 layers, and the number of samples of delamination of the sintered body element. The results are compared for 1000 items.

(Margins below) As is clear from the table, in the sheet of the present invention, the surface level difference of the green sheet is overwhelmingly reduced, and even after lamination, a uniform molded product with no surface irregularities is obtained. Further, by using the sheet of the present invention, it is possible to suppress the occurrence of delamination of the sintered body element.

As described above, according to this embodiment, by using the green sheet with a flat surface according to the present invention, the yield in manufacturing a multilayer ceramic capacitor can be improved.

Effects of the Invention As described above, the present invention provides a green sheet with a flat surface, and at the same time brings about an epoch-making effect in improving productivity in the production of multilayer ceramic capacitors.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of a green sheet for a multilayer ceramic capacitor according to the present invention, and FIG. 2 is a sectional view of a conventional embedded sheet. 4...Base film, 5a...Lower internal electrode, 5b...Upper internal electrode, 6a...
... lower dielectric layer, 6b ... upper dielectric layer.

Claims (1)

[Claims] A dielectric layer is formed on the base film on which the internal electrodes are formed, and an internal electrode exactly the same as the internal electrode is formed on the dielectric layer in the gap between the internal electrodes, and the dielectric layer is formed on top of the dielectric layer. A green sheet for a multilayer ceramic capacitor characterized by forming a dielectric layer exactly the same as the body layer.