JPH0352210A - Laminated ceramic capacitor - Google Patents

Abstract

PURPOSE:To enable attainment of a laminated ceramic capacitor being free substantially from delamination, crack, etc., by forming a sheet on either the uppermost or lowermost side out of a powder material having a larger particle size than inner ones. CONSTITUTION:A plurality of sheets are laminated, while an internal electrode 4 is interposed between the sheets, and at least one of the sheets in a plurality on either the uppermost or lowermost side is formed of a powder material having a larger particle size than the inner ones. Since the particle size of the uppermost or lowermost sheet is large, in other words, a filling rate of the powder in the sheet lowers and, consequently, removal of a binder from this sheet, of course, and also from the inner sheets is facilitated. Since a shrinkage factor in the direction of the thickness of this uppermost or lowermost sheet becomes large, in addition, a strain of the part of the inner sheets affected by the expansion and shrinkage of the internal electrode in the course of baking can be mitigated. Thereby the occurrence of delamination, crack, etc., is prevented substantially.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a multilayer ceramic capacitor used in various electronic devices.

Conventional technology Multilayer ceramic capacitors are used in various electronic devices such as electronic tuners, video tape recorders, and video cameras, but as these electronic devices have become smaller in recent years,
Multilayer ceramic capacitors are being actively developed for smaller size and larger capacity. Therefore, as shown in FIG. 2, a plurality of sheets 1 were laminated and an internal electrode 2 was interposed between each sheet 1.

Problems to be Solved by the Invention For the sheet 1, a powder having a small and uniform particle size is used in order to increase the withstand voltage. However, when the sheet 1 is formed using powder having such a small particle size, the filling rate of the powder in the sheet 1 increases, making it difficult for the binder to come off. As a result, the sheet 1 loses its flexibility with respect to the behavior of the internal electrodes during firing, causing problems such as delamination and cracks.

An object of the present invention is to provide a multilayer ceramic capacitor that is resistant to delamination, cracking, etc. as described above.

SUMMARY OF THE INVENTION In order to solve the problem and achieve this object, the present invention provides a top surface,
At least one of the first and bottom sheets is formed from a powder raw material having a larger particle size than the inner sheet.

Operation In the present invention, the uppermost surface, ′-! Or, because the particle size of the sheet on the bottom surface is large, the filling rate of powder in the sheet is low.
As a result, it is easy to remove the binder not only from this sheet but also from the inner sheet, and because the shrinkage rate in the thickness direction of the top, first, or bottom sheet increases, the internal electrodes are removed during firing. It is possible to alleviate the distortion of the inner sheet portion that is affected by expansion and contraction, and this makes it difficult for dideramination, cracks, etc. to occur.

Embodiment An embodiment of the present invention will be described with reference to FIG. 1
First, powder raw materials with the same composition (in this example, BaTiO 2 type) were prepared under different mixing conditions to powder raw materials with average particle sizes of 0.97 μm, 1.24 μm, and 1.38 μm. Then, an organic binder, an organic solvent, and a plasticizer were respectively added and mixed to form a slurry, and a green sheet with a thickness of 30 μm was prepared by the doctor blade method.

After cutting these sheets into 7 QJff A layer that does not affect the capacitor capacity) was provided in 3 parts. The internal electrodes 4 were printed with Pd paste using a screen method. 1. Effective layer (layer that affects capacitor capacity)
Sheet 5 with an average particle size of 0.97 μm is placed in each part of 5.
were laminated, further applying main pressure, and cut into a shape of 1.8 x 3.5 m using a cutting machine to form individual laminates. Thereafter, each laminate was subjected to binder removal at 300°C for 12 hours, and then main firing was performed at 1350'C for 2 hours in a firing furnace.

This fired body was embedded in resin, and after polishing, the incidence of delamination was confirmed as shown in the table below.

Table 1 As shown in Table 1 above, delamination did not occur in the sintered body in which a sheet with a large average grain size was used in the ineffective layer.

As described above, according to the present invention, it is possible to prevent the occurrence of delamination, etc., and the effect is particularly great for thin film and highly laminated products, and its utility value is great.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a multilayer ceramic capacitor according to an embodiment of the present invention, and FIG. 2 is a sectional view of a conventional example. 3... Effective layer sheet, 4... Internal electrode, 6... Ineffective layer sheet.

Claims (1)

[Claims] A plurality of sheets are laminated, and an internal electrode is interposed between each sheet, and at least one of the uppermost surface and the lowermost surface of the plurality of sheets has a powder raw material having a coarser particle size than the inner sheet. A multilayer ceramic capacitor made with