JPH0414917Y2 - - Google Patents

Description

[Detailed explanation of the idea]

(Industrial Application Field) This invention relates to an annular multilayer capacitor, particularly an annular multilayer capacitor used for noise cancellation in a micromotor. (Prior Art) Ring capacitors using dielectric ceramics have conventionally been used to remove noise components from micromotors. However, in this ring capacitor 1, as shown in FIGS. 4A and 4B, the divided electrodes 3 are formed only on the main surface of the ring-shaped dielectric ceramic 2, so the opposing area is limited and a large static Capacity cannot be obtained. In order to compensate for this drawback, a ring capacitor 6 using semiconductor ceramics as shown in FIGS. 5A and 5B has been proposed. This ring capacitor 6 has a divided electrode 9 formed on one main surface of a ring-shaped substrate 8 made of semiconductor ceramic on which a dielectric layer 7 is formed. There are also capacitors with electrodes arranged like normal multilayer capacitors. (Problems to be solved by the invention) However, when semiconductor ceramics are used as in the ring capacitor 6 shown in FIGS. 5A and 5B, the equivalent series resistance (ESR) increases, resulting in poor high frequency characteristics. It will be inferior. Furthermore, if the internal electrodes are arranged like a normal multilayer capacitor in order to increase the opposing area, if an odd number of electrodes are required, problems may occur, such as the upper electrodes being shot together.
It becomes impossible to deal with an odd number of electrodes. Therefore, the main purpose of this invention is to provide a ring-shaped multilayer capacitor with large capacitance and good frequency characteristics. Furthermore, according to this invention, the stray capacitance generated between the electrodes becomes extremely small. (Means for Solving the Problems) This invention is a multilayer capacitor including an annular laminate sintered body in which a plurality of annular ceramic dielectric layers are laminated with internal electrodes interposed and sintered together. At least three internal electrodes are stacked at intervals in the thickness direction of the laminated ceramic dielectric layers, with the ends of adjacent internal electrodes overlapping each other, and the internal electrodes are made of ceramic dielectric layers. The dielectric layers are arranged in a spiral shape when viewed in the thickness direction,
The internal electrode is formed in an arc shape, and a lead-out portion connected to the external electrode is formed on one or both of the outer peripheral edge and the inner peripheral edge of the arc-shaped portion, and the external electrode is electrically connected to each of the internal electrodes. The external electrode is formed on the laminated sintered body, and the external electrode is formed on one or both of the inner peripheral end face and the outer peripheral end face of the annular laminated sintered body, and on one or both of the upper and lower main surfaces of the annular laminated sintered body. This is a multilayer capacitor that is formed by extending it to both sides. (Effect of the invention) According to this invention, since a porcelain dielectric is used,
The equivalent series resistance is smaller than when using semiconductor elements. Therefore, it is possible to obtain a device with excellent high frequency characteristics. Moreover, by stacking at least three internal electrodes at intervals in the thickness direction and with their ends overlapping each other, the facing area of the electrodes becomes large, and a large capacity is thereby obtained. Multiple electrodes can be formed. The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings. (Example) Fig. 1A is an exploded perspective view showing an embodiment of this invention, Fig. 1B is a partially exploded perspective view thereof, and Fig. 1C is a perspective view thereof. This annular multilayer capacitor 10 includes a plurality of annular dielectric layers of the same size. This dielectric layer consists of two types: a dielectric layer 11 on which no internal electrodes are formed and a dielectric layer 12 on which internal electrodes are formed. Internal electrode 13 formed on the main surface of dielectric layer 12
has a circular arc shape, and its outer peripheral portion reaches the outer peripheral edge of the dielectric layer, and has an external electrode 1, which will be described later.
The drawer portion 13 is a portion conductively connected to 4.
It has a. In this embodiment, a set of three dielectric layers 12 on which internal electrodes 13 are formed is used.
It is formed by stacking a large number of sets in the thickness direction of the dielectric layer 12 with the dielectric layer 12 facing upward. That is, on the dielectric layer 12 on which the internal electrode 13 is formed, there is a dielectric layer 12 on which another internal electrode 13 is formed, and the internal electrode 13 is placed on the dielectric layer 12 on which the internal electrode 13 is formed.
are laminated one after another with dielectric layers, internal electrodes,
A dielectric layer... is arranged. In this case, the dielectric layer 12 on which the upper, middle, and lower internal electrodes 13 are formed is different from the dielectric layer 1 laminated adjacent to it.
2 and the other dielectric layer 12 have an angle of 120°,
The arcuate portions of the internal electrodes 13 are arranged in three directions, and when viewed in the stacked thickness direction, are sequentially arranged in a right-handed spiral shape, with overlapping portions near both ends of the arcuate portions. Arranged. Therefore, the extended portions 13a connected to the external electrodes 14 are oriented in the same direction for every third dielectric layer 12, and the directions are oriented in three directions every 120 degrees. In this way, a plurality of sets of three dielectric layers 12 are laminated as described above,
A plurality of dielectric layers 11 on which the internal electrodes described above are not formed are laminated in the thickness direction of the dielectric layers 12 on the uppermost and lowermost surfaces, forming an annular laminated sintered body as a whole. Then, the three external electrodes 14 formed on the outer peripheral end surface of the annular laminated sintered body are connected to the drawn-out portions 13a, each facing in the same direction. Further, an external electrode 14a is formed on one or both of the upper and lower surfaces of the annular laminated sintered body, and also on the upper surface in the illustrated state. Experimental Example A dielectric green sheet that forms the dielectric layer of a ring capacitor was formed using a composition consisting of 87 mol% BaTiO ₃ and 13 mol% BaZrO ₃ . Then, Pd paste, which will be the material for the internal electrodes 13, is placed in the center of the main surface of these dielectric green sheets 15, with an outer diameter of 12 mm and an inner diameter of 10 mm, as shown in FIG.
mm, the length of the drawer part 13a is 1 mm,
Three types of patterns such as A, B, and C were printed. Thirty-one of these green sheets were stacked in the order of A, B, C, A...A, in the arrangement described in the previous example, and dielectric green sheets without this Pd paste printed on top and bottom were added. , 10 sheets each were stacked on top and bottom. Next, these stacked green sheets are
Under the conditions of 40℃ and 5t/ ^cm2 , crimping is performed for 15 seconds each on the top and bottom.
I went around. Next, this laminate is cut into an annular shape having an outer diameter of 13 mm and an inner diameter of 9 mm, and is molded into the shape shown in FIG. 1A. Due to this cutting, the leading portion 13a connected to the external electrode is located at its tip on the outer peripheral surface of the dielectric layer made of the dielectric green sheet. Next, the cut laminate is baked at 1350°C for a time, silver paste is applied to the external electrode portion of the end face of the annular dielectric layer including the lead-out portion 13a, and the external electrode is baked again at 800°C. was formed. The characteristics of the obtained multilayer capacitor were compared with those of a ring capacitor using semiconductor ceramics, and the results are shown in the following table.

[Table] As can be seen from this table, the capacitance C of the multilayer capacitor according to the present invention and the conventional ring capacitor using semiconductor ceramics does not change when the frequency is 1KHz, but increases by about 4 times when the frequency is 100KHz. It turns out that the dielectric layer DF also has a frequency of
It can be seen that at 1KHz, it becomes 2/3, and at 100KHz, it becomes about 1/9. In addition, in the embodiment described above, the external electrode 1
4 was formed on the outer surface from the inner peripheral end surface of the annular ceramic dielectric layer 12, and as shown in FIG. Print electrode paste in the shape of green sheets 16 and 17 to form on the inside or both sides thereof,
An external electrode may also be formed. Further, the shape of the annular multilayer capacitor is not limited to the illustrated annular shape, but may be a polygonal annular shape, and the size, the number of external electrodes, and the shape and number of internal electrodes may be changed as appropriate.

[Brief explanation of drawings]

FIG. 1A is an exploded perspective view showing an embodiment of this invention. FIG. 1B is a partially exploded perspective view of the embodiment. FIG. 1C is a perspective view of the embodiment. FIG. 2 is a plan view showing a dielectric green sheet on which internal electrodes were formed, which was used in an experimental example of this invention. FIG. 3 is a plan view of a dielectric green sheet showing a modification of the above embodiment. FIG. 4A is a perspective view showing a conventional ring capacitor using dielectric ceramic;
FIG. 4B is an enlarged sectional view taken along the - line. Fifth
Figure A is a perspective view showing a conventional ring capacitor using semiconductor ceramics, and Figure 5B is a perspective view of the ring capacitor using semiconductor ceramics.
It is a line enlarged sectional view. In the figure, 10 is an annular multilayer capacitor, 1
1 is a dielectric layer on which internal electrodes are not formed, 12
Reference numeral 13 indicates a dielectric layer on which internal electrodes are formed, 13 indicates an internal electrode, 13a indicates a lead-out portion, and 14 indicates an external electrode.

Claims (1)

[Claims for Utility Model Registration] A multilayer capacitor including an annular laminated sintered body in which a plurality of annular ceramic dielectric layers are laminated with internal electrodes interposed therebetween and sintered together, the internal electrodes being: At least three or more internal electrodes are stacked at intervals in the thickness direction of the stacked ceramic dielectric layers, with end portions of adjacent internal electrodes overlapping each other, and the internal electrodes include the ceramic dielectric layers. The internal electrodes are arranged in a spiral shape when viewed in the stacked thickness direction, and the internal electrodes are formed in an arc shape, and on one or both of the outer peripheral edge and the inner peripheral edge of the arc-shaped part,
A lead-out portion connected to the external electrode is formed, an external electrode electrically connected to each of the internal electrodes is formed on the laminated sintered body, and further, the external electrode is connected to the inner peripheral end face and the outer periphery of the annular laminated sintered body. A multilayer capacitor formed on one or both of the end faces and extending to one or both of the upper and lower main surfaces of the annular multilayer sintered body.