JPH0831390B2 - Method for manufacturing laminated porcelain capacitor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a laminated ceramic capacitor.

2. Description of the Related Art In recent years, with the development of ultra-compact, thin and lightweight electronic devices such as radios, microcassette recorders, electronic tuners, video cameras, etc., miniaturization of capacitors used as circuit elements,
Large capacity has been strongly demanded. A multilayer ceramic capacitor is known as a component satisfying these requirements. As a method of manufacturing a laminated porcelain capacitor, first, a ceramic dielectric layer having a thickness of several tens of μm is provided on an organic film by a doctor blade method using a slurry composed of a dielectric powder, a binder, a plasticizer, and an organic solvent. Create a sheet. Next, after stacking a plurality of sheets on which the internal electrodes are printed on this sheet, a laminated molded body is prepared by pressure bonding, and after that, it is cut into chips and fired, and then the external electrodes are formed. ("Insulation derivative ceramics", published by CMC, edited by Tadashi Shiozaki, p211 to 227, 1985) Such a method, that is, as shown in FIG. 2, a dielectric layer 5 is formed on the surface of a base film 4 and an internal electrode 6 is formed thereon. When sheets formed by printing are stacked,
The laminated thickness differs between the portion where the internal electrodes 6 overlap and the portion where only the dielectric layer 5 is formed. For this reason, the magnitude of the pressure applied when the laminated body is pressed to make the thickness uniform is partially different. The pressure unevenness of this laminated body becomes larger as the quality becomes higher. In the cutting process for dividing the laminated body produced by using the sheet having the structure shown in FIG. 2 into the capacitor chips, the mechanical strength of the low-density portion where the pressing force is small is weak. Was large, and cracks and peeling of the internal electrodes 6 were generated.

In order to improve this point, an internal electrode 8 is formed on a support 7 such as a base film as shown in FIG. 3, and then a dielectric layer 9 is formed on the internal electrode 8 to form a dielectric layer 9 surface and an internal electrode. There has been proposed a method for producing a laminated ceramic capacitor using a sheet in which eight layers have the same surface. (Japanese Patent Publication No. 60-29209) Problems to be Solved by the Invention As shown in FIG. 3, the internal electrode 8 is embedded in the dielectric layer 9 and the surface of the dielectric layer 9 and the surface of the internal electrode 8 are the same. When a capacitor is formed using a sheet having a surface, pressure unevenness of the laminated molded body can be improved, but a large number of peeling phenomena occur between the dielectric layer 9 and the electrode layer 8 after sintering, resulting in poor yield. Had a point.

In view of the above problems, the present invention creates a capacitor using a sheet in which the internal electrodes are embedded in the dielectric layer and the dielectric layer surface and the internal electrode layer surface form substantially the same surface,
An object of the present invention is to provide a method for manufacturing a laminated ceramic capacitor that can suppress the occurrence of delamination and can significantly improve the yield.

Means for Solving the Problems In order to solve the above problems, the method for manufacturing a laminated ceramic capacitor of the present invention first creates a green sheet as described below. That is, an internal electrode is formed by a screen printing method or the like on the surface where the surface of the base film is uneven, and then a dielectric layer is formed on this surface. The inner electrodes and the dielectric layer of the green sheet are heated and pressure-bonded from the side where the dielectric layer is not formed, and the inner electrode and the dielectric layer formed on the green sheet are heat-transferred and laminated on the object at the same time. It is a thing.

Working If a sheet is used in which internal electrodes are formed on the surface of a conventional base film, and then a dielectric layer is further formed on this and the internal electrodes are embedded in the dielectric layer, the cause of delamination is likely to occur as follows. It seems to be due to. In the case of this green sheet, since the internal electrode surface and the dielectric layer surface are formed on a flat base film such as polyester, when this sheet is laminated, the surface from which the base film is peeled off, in other words, the electrode surface and The surface of the dielectric layer is an extremely flat surface without irregularities. Generally, in the case of a laminated ceramic capacitor containing BaTiO ₃ as a main component, the material used for the internal electrodes is a noble metal such as palladium or platinum. It is believed that these internal electrodes do not chemically react with BaTiO ₅ , but rather adhere to the uneven internal electrode surface by the physical effect of the dielectric layer entering. However, since the internal electrode surface and the dielectric layer surface are flat in the conventional sheet in which the internal electrodes are embedded in the dielectric layer, physical effects cannot be expected and the boundary between the internal electrodes and the dielectric layer cannot be expected when firing the laminated compact. Therefore, the peeling phenomenon easily occurs.

On the other hand, the following green sheets are used in the method for manufacturing a laminated ceramic capacitor of the present invention. That is, as shown in FIG. 1, a base film 3 serving as a support for the internal electrodes 1 and the dielectric layer 2 is used, in which the surface of the base film 3 is finished in advance by embossing or the like to give an uneven shape. The internal electrode 1 and the dielectric layer 2 are formed on this surface by a printing method or the like. When the base film 3 of the green sheet having such a structure is peeled off, the surfaces of the internal electrode 1 and the dielectric layer 2 become uneven, so that the laminated molded body obtained by heating and transferring this sheet is laminated with the internal electrode 1. The adhesion of the dielectric layer 2 is extremely good, and the delamination can be remarkably suppressed even after sintering.

EXAMPLES Specific examples of the present invention will be described in detail. BaTi
After blending 10 parts by weight of polyvinyl butyral resin and 2 parts by weight of dioctyl phthalate with 100 parts by weight of dielectric powder containing O ₃ as a main component, kneading was carried out for 20 hours by a ball mill using n-butyl acetate as a solvent, and 1800 cps. A slurry of viscosity was created.

Next, the average surface roughness is 1.
Commercially available Pd electrode paste was printed in a predetermined shape on the surface of a polyester film having a thickness of 50 μm and finished in an uneven shape of 5 μm by a screen printing method, and then dried. Further, the above-mentioned slurry was formed into a sheet on this surface by a doctor blade method to prepare a green sheet having a dielectric layer thickness of 25 μm and embedded with internal electrodes. For comparison, a conventional green sheet for laminated ceramic capacitors was also prepared by the following method. That is, an internal electrode was formed on the surface of a polyester film having a thickness of 50 μm and no unevenness by the same electrode material and method as described above, and then the above-mentioned slurry was used to form a 25 μm-thick dielectric layer for laminated ceramic capacitors. Created a sheet.

Using these two types of green sheets, a laminated molded body having 40 layers was prepared by a heat transfer method. Specifically, the dielectric layer that does not directly contribute to the 200 μm thick capacitor is overlaid so that the internal electrodes and the dielectric layer of the green sheet face each other, and then heat-pressed with a hot plate press from the base film surface side. The internal electrode and the dielectric layer were simultaneously transferred and laminated. After repeating this step, a dielectric sheet having a thickness of 200 μm, which does not directly contribute as a capacitor, was laminated again. The temperature during heat transfer is 150 ° C. and the pressure is 30 kg / cm ² . After cutting this laminated compact into chips, the chip compact was baked for 2 hours at 1300 ° C. while being sprinkled with ZrO ₂ powder. The state of cracks and internal electrode peeling at the time of cutting the inside of the sintered body of the multilayer chip capacitor thus produced and the multilayer molded body was observed with an electron microscope. As a result, no defective product was found when cutting the laminated molded body in any of the 100 samples. However, as a result of observing the fine structure in the sintered body, when the conventional green sheet was used, delamination occurred between the dielectric layer and the internal electrode, and the defect rate was 10%. No delamination was observed in the manufacturing method of the present invention. As is clear from the above results, using the method for manufacturing a laminated ceramic capacitor according to the present invention, that is, using a sheet in which internal electrodes and a dielectric layer are formed on the surface of the green sheet on which the base film surface is uneven. By thermal transfer by thermocompression bonding and stacking, there is no crack at the time of cutting the laminated molded body, peeling of the internal electrode, and good adhesion between the internal electrode and the dielectric layer even after firing, resulting in delamination of the sintered body. The generation could be suppressed significantly. In this embodiment, the laminated porcelain capacitor is taken up, but it goes without saying that the same effect can be obtained even when applied to other laminated porcelain electronic parts such as a laminated actuator, a laminated varistor and a laminated substrate.

EFFECTS OF THE INVENTION As described above, in the method for manufacturing a laminated ceramic capacitor according to the present invention, a green sheet in which internal electrodes and a dielectric layer are formed on the surface of an uneven base film is used as the electrode layer and the dielectric layer. Since the internal electrodes and dielectric layer formed on the base film are transferred to the object at the same time by thermocompression bonding from the side of the base film that has not been formed, the laminated molded body is cut into chips. In this case, since the pressure unevenness during lamination is small, cracks and internal electrodes do not peel off, and the adhesion between the internal electrodes and the dielectric layer is good even after firing, so delamination of the sintered body also occurs significantly. Its industrial value is extremely great as it can be suppressed.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a laminated ceramic capacitor green sheet used in the present invention, and FIGS. 2 and 3 are sectional views showing the structure of a laminated ceramic capacitor green sheet used in a conventional method. 1 ... internal electrode, 2 ... dielectric layer, 3 ... base film.

Claims (1)

[Claims] 1. An internal electrode of a base film of a green sheet produced by printing an internal electrode on a surface of a base film having an uneven surface and then forming a dielectric layer on the surface. A method for manufacturing a laminated ceramic capacitor, comprising a step of laminating the internal electrodes and the dielectric layer onto an object by applying heat and pressure from the surface side on which the dielectric layer is not formed.