JPH0338812A - Laminated capacitor - Google Patents

Abstract

PURPOSE:To obtain a laminated capacitor whose volume efficiency is high at a high breakdown strength and whose reliability is excellent by a method wherein three kinds of sheetlike electrodes exposed on three different end faces are used and any of one kind of sheetlike electrode used as a common electrode and the two other kinds of sheetlike electrodes are piled up alternately. CONSTITUTION:Three kinds of sheetlike electrodes 1 to 3 are used as sheetlike electrodes; one end each of these sheetlike electrodes 1 to 3 is exposed on three different end faces of a laminated element to be formed. The laminated element is formed in such a way that any of one kind of sheetlike electrode is used as the common electrode 1 and that this common electrode 1 and the two other kinds of sheetlike electrodes 2, 3 are laminated so as to be piled up alternately. Thereby, it is possible to obtain a laminated capacitor whose volume efficiency is high at a high breakdown strength and whose reliability is excellent; this capacitor contributes to a large capacity of a small-sized laminated capacitor for high voltage use.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a multilayer capacitor, and particularly to a multilayer structure of internal electrodes thereof.

[Prior Art] Conventionally, in manufacturing a multilayer capacitor, two types of sheet-like electrodes, which are exposed on one end surface of a multilayer element to be formed and have a margin portion on the opposite end surface, are connected to each other. They are alternately laminated with sheet-like dielectrics in between so that the exposed ends are located on opposite sides, and then external electrodes are provided on the electrode exposed surfaces of the formed laminated elements. FIG. 6 is a diagram showing such a conventional general multilayer capacitor,
11 and 12 are two types of sheet-like electrodes, 13 is a sheet-like dielectric, and 14 is an external electrode.

By the way, a multilayer capacitor having such a structure has a drawback in that when the withstand voltage is increased, the capacitance per volume decreases.

The reason for this will be explained below. In other words, the thickness of the dielectric is determined according to the withstand voltage of the product capacitor.Although in theory the withstand voltage and the thickness of the dielectric are directly proportional, in reality the thickness of the dielectric is determined at a certain rate. Even if the resistance is increased, it is impossible to increase the withstand voltage at the same rate. For example, one of the most typical multilayer capacitors is a multilayer ceramic capacitor, and the relationship between the dielectric thickness and withstand voltage in this multilayer ceramic capacitor is as shown in FIG. As shown in this Figure 8,
The actual withstand voltage when the dielectric thickness is 50 μm is:
0.76 kV, while the dielectric thickness is doubled to 1.
00μm, the actual withstand voltage is twice as high as 1.52
It is not kV, ],.

20 kV, which is just under 1.6 times as high. In order to double the actual withstand voltage to 1.52 kV, the thickness of the dielectric must be tripled to 150 μm or more. .

On the other hand, since the capacitance of a capacitor is inversely proportional to the thickness of the dielectric, the higher the withstand voltage of the capacitor, the lower the capacitance per volume (hereinafter referred to as volumetric efficiency) will inevitably be. be. Therefore, especially for small high-voltage multilayer capacitors whose product dimensions are limited,
With the structure shown in the figure, it is difficult to obtain a large capacitance.

FIG. 7 shows a multilayer capacitor proposed to avoid the above drawbacks. The multilayer capacitor shown in FIG. 7 includes a first sheet-like electrode 15 that is exposed on both end faces of the multilayer element to be formed and has a machine in the center, and an exposed electrode of the first sheet-like electrode 15. A second sheet-like electrode 16 having margins on both end faces
These are alternately laminated with sheet-like dielectric material 17 interposed therebetween. The multilayer capacitor shown in FIG. 7 has a structure in which two capacitors are connected in series, and the applied voltage is halved. Therefore, if the thickness of the sheet dielectric 17 is the same, the structure shown in FIG. The withstand voltage is twice that of a multilayer capacitor. However, in the multilayer capacitor shown in FIG. 7, the margin portion provided at the center of the element becomes a wasted volume that does not contribute to capacitance. In other words, does the margin provided in the middle of the element need to be larger than a certain size depending on the rated voltage?In particular, in the case of small-sized, high-voltage multilayer capacitors, the size of the margin relative to the overall element size must be As the ratio of .

In addition, when manufacturing multilayer ceramic capacitors,
Dielectric powder and binder resin are mixed, a sheet-like dielectric of a certain thickness is formed into a bottom shape, and sheet-like electrodes are attached and stacked on top of this dielectric, which is then integrated by applying pressure. In the case of the structure shown in FIG. 7, during pressurization and imaging, the density becomes partially low in the central margin area. As a result, the density in the central part of the fired body decreases, and the mechanical strength of the circular part decreases, or the adhesion strength between the electrode and the ceramic dielectric decreases, making it easy for layers to peel off, and the electrical properties and reliability will decrease.

[Problems to be Solved by the Invention] The present invention has been proposed in order to solve the two problems of the prior art, and its purpose is to achieve high volumetric efficiency when the withstand voltage is increased, and By providing a highly reliable multilayer capacitor, we can contribute to increasing the capacity of small, high-voltage multilayer capacitors.

[Means for Solving the Problems] The multilayer capacitor according to the present invention has a sheet-like electrode,
Three types of sheet-like electrodes are used, and one end of each of these sheet-like electrodes is exposed on three different end faces of the laminated element to be formed, and the laminated element is made of any one type of sheet. It is characterized in that it is formed by using a common electrode as a common electrode and stacking this common electrode and two other types of sheet-like electrodes so as to overlap each other alternately.

Furthermore, in connecting the multilayer capacitor to the outside, it is conceivable to provide an external electrode on the exposed electrode surface of the multilayer body.

[Function] Since the multilayer capacitor of the present invention having the configuration as described below has a structure in which two capacitors are connected in series,
When the product dimensions, dielectric thickness, and number of laminated layers are the same as that of a conventional multilayer capacitor having a general structure as shown in Fig. 6, the capacitance is 1 ．．
/2, the withstand voltage is doubled, and even if the withstand voltage is increased, the volumetric efficiency will not decrease. As described above, in the present invention, even if the withstand voltage is increased, a high volumetric efficiency can be obtained, so that it can contribute to increasing the capacity of a small-sized multilayer capacitor for high voltage. In addition, unlike the conventional technology shown in Figure 7, there is no margin provided at the center, so when applied to multilayer ceramic capacitors, there is no weakness in mechanical strength or adhesion strength, resulting in improved reliability. It is possible to obtain a multilayer capacitor with high performance.

[Example] Below, a first example of a multilayer capacitor according to the present invention will be described.
This will be explained in detail with reference to FIGS. 4 to 4.

FIG. 1 is a diagram showing a multilayer capacitor of this example,
In the figure, 1 to 3 are first to third sheet-like electrodes, and 4 is a sheet-like dielectric. Here, the first sheet-like electrode 1 is a sheet-like electrode that exposes the electrode on the first end surface S1 along the longitudinal direction of the laminated element and serves as a common electrode, and the second sheet-like electrode 2 is Second and third end faces S2 on both sides in the longitudinal direction of the laminated element. This is a sheet-like electrode that exposes the electrode to S3. Then, on one side of the laminated element, the first sheet-like electrode 1 and the second sheet-like electrode 2 are stacked alternately, and on the lower side of the laminated element, the first sheet-like electrode 1 and the third sheet-like electrode Sheet electrodes 3 are alternately stacked on top of each other.

Next, the manufacturing process of the multilayer capacitor of this example will be explained.

■ Add a binder to fine powder of high dielectric ceramic dielectric, mix in a ball mill to make a slurry, form a dielectric sheet with a thickness of 50 μm using the doctor blade method, and punch out to a certain size.

■Using two types of printing patterns, an electrode paste consisting of palladium powder and an organic vehicle is applied to a dielectric sheet by screen printing, dried, and then dried as shown in Figure 2 (A).
B) The first and second printing sheets)・PI, P
form 2. Here, the first printed sheet) P+ is applied to the sheet-like dielectric material 4'' and the first sheet-like electrode 1, which becomes the first sheet-like electrode 1.
The second printed sheet 1-P2 is formed by forming an electrode pattern 5 on the sheet-like dielectric material 4, which becomes the second and third sheet-like electrodes 2 and 3. 6. Further, 7 is a cut mark.

(2) Prepare 20 each of the first and second printing sheets p, p2, position each 10 of them so that their cut marks 7 match, and stack them alternately.

Next, the remaining 10 second printing sheets P2 are placed 1 on a flat surface.
The remaining ten first printed sheets P1 are rotated by 80 degrees, and while the orientation of the remaining ten first printed sheets P1 remains unchanged, they are positioned so that the cut marks 7 coincide with each other and stacked alternately. FIG. 3 is a perspective sectional view showing such a lamination method. After this, the laminate
5 sheets of dielectric material 4 without printed electrodes are placed below the second layer.
Stack them one by one.

(2) After the entire laminate is hot-pressed and completely crimped, it is cut vertically and horizontally at the cut mark 7 position. Thereafter, it is sintered at a high temperature to produce a laminated element as shown in FIG.

By the steps shown in "2" to "■", an element of length 4.5 mm, width 3.2 mm, and thickness 1.5 mm was formed, and then
A chip-shaped capacitor having an external electrode 5 as shown in FIG. 4 was manufactured by baking silver paste on the exposed surface (3 locations) of the internal electrode, and as Comparative Examples 1 and 2, FIGS. Capacitors with the same product dimensions were manufactured using the conventional structure shown in FIG. That is, in Comparative Example 1, a sheet-like electrode of the same quaternary material was formed on a sheet-like dielectric of the same material with a thickness of 100 μm, and a multilayer ceramic capacitor having the structure shown in FIG. 6 was obtained by laminating 20 layers. In Comparative Example 2, a sheet-like electrode made of the same material was formed on a sheet-like dielectric material made of the same material with a thickness of 50 μm, and a multilayer ceramic capacitor having the structure shown in FIG. 7 was fabricated with 40 layers. was created. Various characteristic tests were conducted on the thus obtained capacitor of this example and the capacitors of Comparative Examples 1 and 2, and the results shown in Tables 1 and 2 were obtained.

First, Table 1 shows the results of examining the average value of capacitance and average value of dielectric breakdown voltage for three types of capacitors using 10 samples each.

Table 1 From Table 1, it can be seen that the capacitor of the present example has a DC breakdown voltage of 6.5% compared to Comparative Example 1 while obtaining the same capacitance.
The difference was 0%, and compared to Comparative Example 2, it was 1%.
．． Although it has four times the capacitance, the DC breakdown voltage is also 14
It can be seen that it has increased by about %.

Next, Table 2 shows three types of capacitors using 55 samples each, temperature 125°C, voltage 250Vd.
c shows the results of a life test with a test time of 5000 hours.

Table 2 From Table 2, in Comparative Example 1 and Comparative Example 2, the number of defects per 5000 hours was 55, 2 and 7, respectively, which was 10% to 20%, and the number of defects per 1000 hours was 10% to 20%. Although the failure rates of these are high at 4.4% and 2.5%, in this example, the number of failures out of 55 is zero, and the failure rate is as low as 0.33% or less. It is clear that the life of the capacitor of Example is significantly improved compared to Comparative Example 1.2.

Furthermore, in the capacitor of Comparative Example 2 which has a margin in the center, the density is partially lowered only in the center, the mechanical strength and adhesion strength are weakened, and the electrical characteristics and reliability are reduced. In contrast to the drawbacks, the capacitor of this embodiment has no such weak point in terms of strength and has excellent electrical characteristics and reliability.

Note that the present invention is not limited to the above embodiments, and the specific number of laminated layers, ratings, product dimensions, etc.
This can be selected. Furthermore, in the embodiment, the fourth
As shown in the figure, silver paste was burnt on the exposed surfaces (3 locations) of the internal electrodes to provide external electrodes 5.
If necessary, as shown in FIG. 5, the lead wires 6 can be electrically connected with solder 7 or the like and covered with an exterior material 8.

[Effects of the Invention] As explained below, in the present invention, three types of sheet-like electrodes exposed on three different end faces are used, and one type of sheet-like electrode is used as a common electrode and the other sheet-like electrodes are connected to each other. By simply improving the structure by stacking two types of sheet-shaped electrodes and stacking them alternately, we can provide a multilayer capacitor with high volumetric efficiency and excellent reliability when the withstand voltage is increased. It can contribute to increasing the capacity of high-voltage multilayer capacitors.

z

[Brief explanation of drawings]

FIG. 1 is a diagram showing the laminated structure of a multilayer capacitor according to an embodiment of the present invention, and FIG. 1(A) is a perspective view, and FIG.
B) is a cross-sectional view taken along the line A-A in Figure 1 (A), Figure 1 (C) is a cross-sectional view taken along the line B-B in Figure 1 (A), and Figure 2 is used in the manufacturing process of the same example. FIG. 2(A) is a plan view showing a first printed sheet on which an electrode pattern that becomes a common electrode is printed, and FIG. 2(B) shows an electrode that becomes another sheet-like electrode. FIG. 3 is a plan view showing a second printed sheet with a pattern printed thereon, FIG. 3 is a perspective cross-sectional view showing a method of laminating the printed sheets shown in FIG. 2, and FIG. Perspective view shown, fifth
The figures are cross-sectional views showing different embodiments of the invention. 6 and 7 are cross-sectional views showing different conventional multilayer capacitors, and FIG. 8 is a graph showing the relationship between dielectric thickness and withstand voltage in a multilayer ceramic capacitor. DESCRIPTION OF SYMBOLS 1... 1st sheet-like electrode (common electrode), 2... 2nd sheet-like electrode, 3... 3rd sheet-like electrode, 4...
... Sheet dielectric, 5... External electrode, 6... Lead wire, 7... Solder, 8... Exterior material, 81-S3...
End face of laminated element, PI, P2...Printed sheet. 11.12, 15.16...Sheet electrode, 13゜1
7... Sheet-like dielectric material, 14... External electrode.

Claims (2)

[Claims] (1) In a multilayer capacitor formed by laminating a plurality of sheet-like electrodes via a sheet-like dielectric material to form a multilayer element, three types of sheet-like electrodes are used as the sheet-like electrodes, and these sheet-like electrodes are One end of each of the sheet-shaped electrodes is exposed on three different end faces of the laminated element to be formed, and one of the sheet-shaped electrodes is used as a common electrode, and this common electrode and the other two A multilayer capacitor characterized by being formed by laminating different types of sheet-like electrodes in an alternating manner. (2) The multilayer capacitor according to claim 1, characterized in that an external electrode is provided on the exposed electrode surface of the multilayer element.