JP809H - Multilayer ceramic capacitor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a laminated ceramic capacitor in which a ceramic and an external electrode are simultaneously fired. (Prior Art) A conventional multilayer ceramic capacitor obtained by simultaneously firing a ceramic and an external electrode is produced according to the following manufacturing procedure. First, a conductive paste containing conductive particles such as Ni and Cu is printed on the main surface of a plurality of long unfired dielectric ceramic sheets to form a plurality of conductive layers for internal electrodes. Every other sheet is shifted in the longitudinal direction and overlapped, and then pressure-bonded. Create a chip piece as a body. Then, a conductive paste is applied to the end face where the conductive layer of the chip piece is exposed and the peripheral edge portion continuing to this to form a conductive layer for external electrodes, and then in a reducing atmosphere at a temperature of 900 to 1200 ° C. Then, the electrodes of the ceramic body are simultaneously fired. The outer electrode of the thus obtained multilayer ceramic capacitor is electrically connected to the inner electrode at the end face, and directly adheres to the end face and the peripheral edge portion of the capacitor body connected to the inner face. (Problems to be Solved by the Invention) FIGS. 3 and 4 created by the above-described manufacturing procedure.
The multilayer ceramic capacitor shown in the figure has cracks C in the ceramic b around the outer electrode a formed on the peripheral edge of the capacitor body during a temperature shock test after soldering to a printed circuit board or the like. There has been a problem that some insulation resistance values are less than 10 ³ MΩ. In FIG. 4, d is an internal electrode. It is an object of the present invention to provide a multilayer ceramic capacitor which can solve the above-mentioned conventional problems. (Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention is directed to both ends of a capacitor element body obtained by laminating and crimping a plurality of unfired ceramic sheets on which a conductive layer for internal electrodes is formed. In a multilayer ceramic capacitor formed by forming a conductive layer for an external electrode on a surface and a peripheral edge portion continuous with the surface and firing the laminated ceramic capacitor, the ceramic is provided between the peripheral edge portion of the ceramic body and the conductive layer for the external electrode. An intermediate layer made of ceramic and conductive particles having the same composition is interposed. (Function) Since the shrinkage due to firing of the unfired ceramic and the shrinkage due to firing of the external electrode conductive layer are different, the ceramic at the peripheral edge of the external electrode formed at the peripheral edge of the capacitor body after firing is different. Distortion remains. However, when an intermediate layer made of ceramic having the same composition as the ceramic and conductive particles is interposed between the peripheral edge of the capacitor body and the external electrode, the shrinkage of the intermediate layer is reduced by the shrinkage of the ceramic. Since it is between the contraction amount of the external electrode and the contraction amount of the external electrode, the strain generated in the ceramic becomes small. Thus, in the temperature shock test after soldering the capacitor of the present invention to a printed circuit board or the like, cracks do not occur in the ceramic at the peripheral edge of the external electrode. (Embodiment) An embodiment of the present invention will be described with reference to the accompanying drawings. Example 1 A plurality of unfired dielectric ceramic sheets containing BaTiO ₃ as a main component and having a thickness of 38 μm were prepared. Also, 100g of Ni powder with 99.9% purity and 15% of ethyl cellulose
g, and butyl carbitol 94 g were kneaded to form an internal electrode conductive paste, 99.9% pure Ni powder 50 g, and 50 g unfired ceramic powder having the same composition as the ceramic sheet.
And paste for the intermediate layer made by kneading 20 g of ethyl cellulose and 94 g of butyl carbitol, 100 g of Ni powder with 99.9% purity, 20 g of ethyl cellulose and 94 g of butyl carbitol
An external electrode paste prepared by kneading and was prepared. Using the above-mentioned unfired ceramic sheet and conductive paste for internal electrodes, an unfired capacitor element body is prepared according to a conventional method, and one end of the internal electrode existing in the capacitor element body is continuous with the exposed end surface. After applying the intermediate layer paste in a strip shape on the peripheral edge portion and drying at 150 ° C., the external electrode paste is continuously applied on the intermediate layer and the end surface of the capacitor body, and after drying, H _A multilayer ceramic capacitor was prepared by firing at 1180 ° C. for 2 hours in an N ₂ gas atmosphere containing 2% of 2. A nickel plating film was formed on the external electrodes of these capacitors by a commercially available electroless nickel plating bath. 1 and 2 show a monolithic ceramic capacitor according to an embodiment of the present invention. In the figure, (1) is a capacitor element body having internal electrodes (2) laminated inside with ceramic layers alternately exposed at opposite end surfaces, and (3) is a capacitor element body (1) connected to the end surfaces. A strip-shaped intermediate layer (4) formed on the peripheral edge portion of (1) is an external electrode continuously formed on the intermediate layer (3) and the end face. This monolithic ceramic capacitor is soldered on a glass epoxy wiring board, and a capacitance is measured by using a commercially available LCR meter (manufactured by YHP) and an insulation resistance meter (manufactured by Toa Denpa).
(c), dielectric loss tangent (tan δ) and insulation resistance (IR) were measured.
Then, after carrying out 100 times of thermal shock tests, one cycle consists of holding at -55 ° C for 30 minutes, moving to + 125 ° C within 2 seconds and holding for 30 minutes. Tangent (tan
δ) and insulation resistance (IR) were measured, and the maximum rate of change of capacitance, the maximum value of tan δ, the number of insulation resistance 10 ³ MΩ or less and the number of those with cracks visually detected are shown in the table below. It was Example 2 As an intermediate layer paste, 50 g of Ni powder in Example 1
Instead of 50 g of unfired ceramic powder having the same composition as 35 g of ceramic, 65 g was prepared by the same method and conditions as in Example 1. The measurement results are shown in the table below. Example 3 As an intermediate layer paste, 50 g of Ni powder in Example 1
Instead of 50 g of unfired ceramic powder having the same composition as 20 g of ceramic, 80 g was prepared in the same manner and conditions as in Example 1. The measurement results are shown in the table below. Example 4 Created by the same method and under the same conditions as in Example 1 except that the Ni powder used in Example 1 was replaced with Cu powder as the conductive particles of the internal electrode paste, the intermediate layer paste, and the external electrode paste. did. The measurement results are shown in the table below. Comparative Example The same method and conditions as in Example 1 were used except that the intermediate layer was omitted. Note that Ag, Ag-Pd, or the like can be similarly used as the conductive particles of each paste. (Effects of the Invention) As described above, according to the present invention, even when soldered to a printed circuit board or when subjected to a temperature shock test or the like, the ceramic is cracked at the peripheral edge of the external electrode at the peripheral edge of the capacitor body. Is less likely to occur, and the insulation resistance is less deteriorated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged perspective view of an embodiment of the present invention, FIG. 2 is its sectional view, FIG. 3 is an enlarged perspective view of a conventional example, and FIG. 4 is its sectional view. . (1) …… Capacitor body, (2) …… Internal electrode (3) …… Intermediate layer, (4) External electrode

Claims (1)

[Claims] [Claims] [Claims] [Claim 1] Both end faces of a capacitor body formed by laminating and crimping a plurality of unfired ceramic sheets on which a conductive layer for internal electrodes is formed, and peripheral edges continuous with the both faces. In a multilayer ceramic capacitor formed by forming a conductive layer for external electrodes on a portion and then firing, a ceramic having the same composition as that of the above ceramic and a conductive layer between the peripheral edge portion of the ceramic body and the conductive layer for external electrodes. A multilayer ceramic capacitor having an intermediate layer composed of particles interposed.