JPH06244050A - Manufacture of laminated ceramic capacitor and laminated green body therefor - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a laminated ceramic capacitor and laminated green body without increasing the number of processes in laminating wherein the thickness of the part where there are internal electrodes is almost equal to that of the part where no internal electrode exists and no delamination or degradation at thermal shock levels will occur. CONSTITUTION:The title ceramic capacitor is one with external electrodes 12 baked on the ends of a bare chip 11 obtained by firing a laminated green body. The laminated green body consists of a lower cover dielectric section 13 obtained by laminating a plurality of ceramic dielectric layers; capacitor section 14 obtained by alternately laminating ceramic dielectric layers 17 and internal electrodes 18 on the upper face of the dielectric section 13; and upper cover dielectric section 15 obtained by a plurality of ceramic dielectric layers on the upper face of the capacitor section. In addition a dielectric section 16 for correcting distortion in lamination, composed of ceramic dielectric layer 17 only, is placed within the laminated capacitor section 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated ceramic capacitor using a dielectric ceramic composition and a method for producing a laminated green body thereof. More specifically, it relates to a method for producing a laminated green body that can be applied to a dry laminating method or a wet laminating method.

[0002]

2. Description of the Related Art In recent years, with miniaturization of radios, microcassette recorders, electronic tuners, video cameras, etc., and development of thin and lightweight electronic equipment, there has been a strong demand for miniaturization and large capacity of capacitors used as circuit elements. It started to come. A monolithic ceramic capacitor is known as a component that satisfies these requirements. In order to manufacture this laminated ceramic capacitor, first, for example, a dielectric ceramic powder, an organic binder, a plasticizer and an organic solvent are mixed to prepare a dielectric slurry, and this slurry is subjected to a doctor blade method, a screen printing method or the like. A sheet is formed by means. Then, a plurality of the dielectric sheets are laminated to form a lower cover dielectric portion, and a ceramic dielectric layer and internal electrodes are alternately laminated on the upper surface of the lower cover dielectric portion to form a capacitor portion. Here, the internal electrodes are formed by screen-printing a conductive paste on the upper surface of a ceramic dielectric layer made of a dielectric sheet with a gap and drying the paste. Next, a plurality of dielectric sheets are laminated on the upper surface of the capacitor section to form an upper cover dielectric section. After pressing the lower cover dielectric part, the capacitor part, and the upper cover dielectric part into a laminated green body, the laminated green body is cut into chips in units of the laminated internal electrodes. Subsequently, the chip body is subjected to binder removal processing, and then baked to form a bare chip, and finally an external electrode is formed on the end face of the bare chip.

On the other hand, demands for miniaturization and large capacity of capacitors have been further strengthened recently, and in order to meet these demands, it is indispensable to increase the number of laminated layers and thin dielectric layers. However, when a large-capacity monolithic ceramic capacitor is manufactured by the above method, if the number of laminated layers increases, the portion where the internal electrode 1 is formed due to the thickness of the internal electrode after the lamination as shown in FIG. The thickness a of 2 becomes larger than the thickness b of the portion 3 where the internal electrode 1 is not formed. In this state, if the layers are laminated by thermocompression bonding, the pressure in the portion 3 where the internal electrode is not formed becomes insufficient due to the difference between the thickness a of the portion 2 where the internal electrode is formed and the thickness b of the portion 3 where the internal electrode is not formed. Become. Therefore, the boundary is distorted, the adhesion between the layers is poor, and defects such as peeling phenomenon (delamination) and minute cracks may occur between the internal electrodes and the dielectric layer during firing due to internal stress. These defects have a problem that the capacitor deteriorates when it is subjected to a thermal shock to the extent that it is immersed in a solder bath without preheating, and the moisture-proof life is shortened to lower the reliability of the capacitor.

In order to solve this problem, there has been proposed a method of punching out only a portion of the internal electrode or thinning the portion of the ceramic dielectric sheet to be overlaid on the internal electrode when forming the capacitor portion. (JP-A-53-423
53). Further, as shown in FIG. 5, a conductive paste is printed and dried on the base film 5 at intervals to form a plurality of internal electrodes 6, and the internal electrodes 6 between the internal electrodes 6 and the ends of the internal electrodes 6 are formed. After the dielectric paste is printed and dried on the portion to form a thickness adjusting dielectric layer 7 having a thickness approximately equal to the thickness of the internal electrode, the dielectric slurry for thickness adjustment and the internal electrode 6 are overlaid with a dielectric slurry. A method for manufacturing a green sheet for a laminated ceramic capacitor, which forms the dielectric layer 8, has been proposed (JP-A-3-74820). In the case of the above manufacturing method, the printing pattern of the conductive paste and the printing pattern of the dielectric paste have a negative and positive relationship with the photographic film.

[0005]

However, according to these methods, the stress at the boundary between the ceramic dielectric layer and the internal electrode can be relieved, but the number of steps for stacking is increased, and the existing equipment is used. Had to be significantly remodeled. Particularly, in the method shown in FIG. 5, since the dielectric slurry and the dielectric paste have the same composition, in other words, the organic binder and the solvent contained in the dielectric slurry, the organic binder and the solvent contained in the dielectric paste, Since they are the same and compatible with each other, the solvent of the dielectric slurry dissolves a part of the binder of the dielectric paste in the stacked state, and the solvent of the dielectric paste also dissolves a part of the binder of the dielectric slurry. Cheap. As a result, the degree of adhesion between the thickness adjusting dielectric layer 7 and the stacking dielectric layer 8 is increased, and the binder of the conductive paste on which the internal electrodes are formed is less likely to be removed when the binder is removed from the laminated green body. If the removal of the binder from the internal electrodes is disturbed, the bubbles generated during the removal of the binder will remain inside the bare chip as they are after firing the laminated green body, causing delamination, cracks, etc., and reducing the thermal shock resistance of the capacitor. Happens anew.

An object of the present invention is to make the thickness of a portion where an electrode layer is formed after laminating to be approximately the same as the thickness of a portion where an electrode layer is not formed, without increasing the number of steps during lamination. An object of the present invention is to provide a laminated ceramic capacitor and a method for manufacturing the laminated green body, which does not hinder the removal of the binder from the internal electrodes when the binder is removed from the laminated green body and does not cause deterioration at the delamination or thermal shock level.

[0007]

In order to achieve the above object, as shown in FIGS. 1 and 2, a monolithic ceramic capacitor 10 of the present invention comprises a bare chip 11 formed by firing a laminated green body 20, and An external electrode 12 burned on the end surface of the bare chip 11 is provided, and the laminated green body is formed on the lower cover dielectric portion 13 formed by laminating a plurality of ceramic dielectric layers, and on the upper surface of the lower cover dielectric portion 13. A capacitor portion 14 formed by alternately laminating the ceramic dielectric layers 17 and the internal electrodes 18, and the capacitor portion 14
And an upper cover dielectric portion 15 formed on the upper surface of the above by laminating a plurality of ceramic dielectric layers. The characteristic configuration is that one or more dielectric strain adjusting dielectric portions 16 made of only the ceramic dielectric layer 17 are provided inside the capacitor portion 14.

In the method of manufacturing a laminated green body according to the dry method of the present invention, the lower cover dielectric portion 13 is formed by repeatedly laminating ceramic green sheets 17 formed by film-forming and drying a dielectric slurry as shown in FIG. And a step of forming a green sheet ceramic dielectric layer 17 on the upper surface of the lower cover dielectric portion 13, and an internal electrode 18 formed by printing and drying a conductive paste on the upper surface of the dielectric layer at intervals. The method includes a step of alternately stacking to form the capacitor section 14, and a step of repeatedly stacking the green sheet 17 on the upper surface of the capacitor section 14 to form the upper cover dielectric section 15. Its characteristic configuration is that a predetermined number of ceramic dielectric layers 17 and internal electrodes 18 are alternately laminated in the step of forming the capacitor section 14, and only the green sheet ceramic dielectric layers 17 are repeated on the upper surface of this laminated body. The lamination distortion adjusting dielectric portion 16 is formed by stacking, and a predetermined number of the ceramic dielectric layers 1 are formed on the upper surface of the lamination distortion adjusting dielectric portion 16.
7 and the internal electrodes 18 are alternately laminated. Figure 4
As shown in, the lower cover dielectric part 13 and the capacitor part 1
4, the dielectric distortion adjusting dielectric part 16, the capacitor part 14 and the upper cover dielectric part 15 are an upper press 21 and a lower press 22.
Then, the laminated green body 20 is obtained.

The method for manufacturing a laminated green body according to the wet method of the present invention comprises a step of repeatedly applying and drying a dielectric slurry to form a lower cover dielectric portion 13, and a step of forming an upper surface of the lower cover dielectric portion 13. A ceramic dielectric layer 17 formed by applying and drying the dielectric slurry and an internal electrode 18 formed by printing and drying a conductive paste at intervals on the upper surface of the dielectric layer are alternately laminated to form a capacitor section 14. The process includes a step of forming the upper cover dielectric portion 15 by repeatedly applying and drying the dielectric slurry on the upper surface of the capacitor portion 14. Its characteristic configuration is that a predetermined number of ceramic dielectric layers 17 and internal electrodes 18 are alternately laminated in the step of forming the capacitor section 14, and only the dielectric slurry is repeatedly applied and dried on the upper surface of this laminated body. The dielectric distortion adjusting dielectric portion 16 is formed, and a predetermined number of ceramic dielectric layers 17 are formed on the upper surface of the dielectric distortion adjusting dielectric portion 16.
And the internal electrodes 18 are alternately laminated.

[0010]

By providing the dielectric distortion adjusting dielectric portion 16 consisting only of the ceramic dielectric layer 17 inside the laminated portion of the capacitor portion 14, the thickness of the portion where the internal electrode 18 shown in FIG. The difference from the thickness of the part where no ridge is formed is reduced. Thereby, the stress at the boundary between the ceramic dielectric layer of the laminated green body 20 and the internal electrode can be relieved. The number of the dielectric distortion adjusting dielectric portions 16 is not limited to one as shown in FIGS. 1 and 2, and may be two or more depending on the number of laminated internal electrodes 18 of the capacitor portion 15. Also, the dielectric portion 1 for adjusting the stacking distortion
The number of ceramic dielectric layers 17 constituting 6 is also the internal electrode 1
It is determined according to the number of laminated layers of 8. Further, as shown in FIGS. 1 and 2, the internal electrodes 18 and 18 on the upper and lower surfaces of the dielectric distortion adjusting dielectric portion 16 are connected to the left and right external electrodes 12 and 12 formed on both end surfaces of the bare chip 11, respectively. In addition to increasing the capacitance by increasing the capacitance, the internal electrodes 18, 18 on the upper and lower surfaces of the dielectric distortion adjusting dielectric portion 16 are connected to one external electrode 12 as shown in FIG. It can also be configured so as not to increase the capacitance.

[0011]

EXAMPLES Next, examples of the present invention will be described together with comparative examples. The invention is not limited to this example. <Example> Lead-based dielectric powder [Pb (Mg _1/3 Nb _2/3 ) O
₃ ] as a main component was added to a resin solution containing polyvinyl butyral resin, dibutyl phthalate, toluene and ethyl alcohol, and the mixture was pulverized and kneaded by a ball mill to prepare a dielectric slurry. 40 this slurry
It was degassed with a vacuum pressure of 65 cmHg through a 0 mesh sieve. Next, the slurry was formed into a film by a doctor blade method and dried to prepare a ceramic green sheet having a thickness of 25 μm, which was cut into a size of 200 mm × width 200 mm. This green sheet is used to form the lower cover dielectric portion 13, the ceramic dielectric layer of the capacitor portion 14, the stacking distortion adjusting dielectric portion 16 and the upper cover dielectric portion 15 shown in FIG.

That is, as shown in FIG. 4, the green sheet 1
8 layers 7 were stacked to form a lower cover dielectric portion 13 having a thickness of 200 μm. Next, 26 layers of green sheets 17 and internal electrodes 18 were alternately stacked on the upper surface of the dielectric portion 13 to form a capacitor portion 14. Internal electrode 18
Was formed by screen-printing a conductive paste in a predetermined rectangular pattern on the upper surface of the green sheet 17 at intervals and drying. In this example, the shape of the internal electrode is 1.3 m
m x width 3.1 mm, one green sheet 1
A total of 2964 pieces were formed on the upper surface of No. 7. The conductive paste used was Ag / Pd = 70/30. Next, 7 layers of only the green sheet 17 on which the internal electrodes are not printed are stacked on the upper surface of the capacitor section 14 to stack the dielectric distortion adjusting section 16
After forming the above, the green sheet 17 and the internal electrode 18 were alternately stacked again on the upper surface of the dielectric portion 16 to form 26 layers each to form the capacitor portion 14. Eight layers of green sheets 17 were stacked on the upper surface of the capacitor portion 14 to form an upper cover dielectric portion 15 having a thickness of 200 μm.

The lower cover dielectric part 13, the capacitor part 14, the stacking distortion adjusting dielectric part 16, and the capacitor part 14.
And the upper cover dielectric portion 15 with the upper press 21 and the lower press 2
Then, the laminated green body 20 was manufactured by pressure bonding with 2. The lamination state of the internal electrodes 18 at this time was such that the positions of the internal electrodes 18, 18 on the upper and lower surfaces of the dielectric distortion adjusting dielectric portion 16 were displaced from each other. Subsequently, the laminated green body 20 is vertically cut into chips each having a size of 2.1 mm × horizontal 4.0 mm, and the chip bodies are heated at 600 ° C. for 1 hour to remove the binder, and further at 1060 ° C. for 2 hours. Burned for hours. This bare chip was barrel-polished to expose the internal electrodes on both end faces thereof, and then external electrodes were formed to fabricate a chip type monolithic ceramic capacitor 10 as shown in FIGS. 1 and 2.

<Comparative Example> The same green sheet and conductive paste as in the above-described embodiment were used, except that the dielectric distortion adjusting dielectric portion 16 was not formed and the number of laminated layers was changed. A type monolithic ceramic capacitor was produced. Here, the lower cover dielectric part and the upper cover dielectric part each have 12 layers of green sheets stacked to have a thickness of 300 μm.
In the capacitor part, 51 layers of green sheets and internal electrodes were stacked.

<Observation of Internal Structure of Chip Capacitor> When 20 cross-sections of each of the chip capacitors of the example and the comparative example were observed with a micrograph, a comparative example was obtained at the boundary between the ceramic dielectric layer of the capacitor part and the internal electrode. 4 chip capacitors were cracked, whereas the chip capacitors of the examples were not cracked at all.

<Thermal Shock Test> The chip capacitors of Examples and Comparative Examples were evaluated by a thermal shock test. That is, grab the chip capacitors one by one with tweezers and use Sn63 /
It was immersed in a eutectic solder bath of Pb37 for 3 seconds and then pulled up. Each of the chip capacitors of Examples and Comparative Examples is 1
It was tested by 00 pieces each, and it was examined by a microscope whether or not cracks were generated in the chip capacitor. As a result, the chip capacitors of the comparative example had three cracks, whereas the chip capacitors of the examples had no cracks at all. Also, the chip capacitor of the embodiment is 4
No cracks occurred at all in the thermal shock test at 00 ° C.

<Moisture Resistance Load Test> 20 chip capacitors of each of Examples and Comparative Examples were evaluated by a humidity resistance load test. That is, a DC voltage of 50 V is applied to the chip capacitor at a temperature of + 85 ° C. and a relative humidity of 85% to
The presence or absence of deterioration after 000 hours was examined. The chip capacitors of the comparative example had 5 defects within 1000 hours, whereas the chip capacitors of the examples did not have any defective products even after 1130 hours.

In the above example, the green body was manufactured by the dry laminating method, but the manufacturing method of the present invention is not limited to the above example, but can be applied to the wet laminating method.

[0019]

As described above, according to the present invention, the internal electrode of the laminated green body is formed by providing the laminated distortion adjusting dielectric portion in which the internal electrode is not formed by printing inside the laminated portion of the capacitor portion. The difference between the thickness of the portion where the internal electrode is not formed and the thickness of the portion where the internal electrode is not formed is reduced, and the internal strain when the green body is molded is reduced. As a result, a reliable multilayer ceramic capacitor that does not increase the number of steps during stacking, does not interfere with the removal of the internal electrodes during binder removal of the laminated green body, does not cause deterioration at delamination and thermal shock levels, and is highly reliable. Is obtained.

[Brief description of drawings]

FIG. 1 is a perspective view of a monolithic ceramic capacitor of the present invention showing a main part in cross section.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view of another monolithic ceramic capacitor of the present invention corresponding to FIG.

FIG. 4 is a configuration diagram showing a situation in which laminated green bodies are laminated by the dry laminating method of the present invention.

FIG. 5 is a cross-sectional view illustrating the manufacture of a green body for stacking by a conventional dry stacking method.

FIG. 6 is a cross-sectional view of a conventional laminated green body.

[Explanation of symbols]

 10 Multilayer Ceramic Capacitor 11 Bare Chip 12 External Electrode 13 Lower Cover Dielectric Part 14 Capacitor Part 15 Upper Cover Dielectric Part 16 Laminate Distortion Adjusting Dielectric Part 17 Ceramic Dielectric Layer 18 Internal Electrode 20 Multilayer Green Body

Claims (3)

[Claims] 1. A bare chip (11) formed by firing a laminated green body (20), and an external electrode (12) baked on an end face of the bare chip (11), wherein the laminated green body (20) is A lower cover dielectric part (13) formed by laminating a plurality of ceramic dielectric layers, a ceramic dielectric layer (17) formed on the upper surface of the lower cover dielectric part (13), and an internal electrode (18). Capacitor parts that are laminated alternately (14)
And a top cover dielectric part (15) formed by stacking a plurality of ceramic dielectric layers formed on the upper surface of the capacitor part (14), wherein the inside of the capacitor part (14) is laminated. A monolithic ceramic capacitor, characterized in that one or two or more dielectric distortion adjusting dielectric parts (16) consisting only of a ceramic dielectric layer are provided. 2. A step of repeatedly laminating ceramic green sheets (17) formed by film-forming and drying a dielectric slurry to form a lower cover dielectric part (13), and a step of forming the lower cover dielectric part (13). The ceramic dielectric layer (17) of the green sheet on the upper surface and the internal electrode (1) formed by printing and drying a conductive paste on the upper surface of the dielectric layer at intervals.
And 8) are alternately laminated to form the capacitor section (14), and the green sheet (17) is formed on the upper surface of the capacitor section (14).
In the method for manufacturing a laminated green body, which comprises repeatedly stacking to form the upper cover dielectric part (15), in the step of forming the capacitor part (14), a predetermined number of ceramic dielectric layers (17) and The internal electrodes (18) are alternately laminated, and only the ceramic dielectric layer (17) of the green sheet is repeatedly laminated on the upper surface of the laminated body to laminate lamination distortion adjusting dielectric portion.
(16) is formed, and a predetermined number of ceramic dielectric layers (17) and internal electrodes (18) are alternately laminated on the upper surface of the dielectric distortion adjusting dielectric portion (16) to form a laminated green. Body manufacturing method. 3. A step of forming a lower cover dielectric part (13) by repeatedly applying and drying a dielectric slurry, and applying and drying the dielectric slurry on an upper surface of the lower cover dielectric part (13). A ceramic dielectric layer (17) and an internal electrode (18) formed by printing and drying a conductive paste at intervals on the upper surface of this dielectric layer are alternately laminated to form a capacitor section (1
In the method for manufacturing a laminated green body, which comprises the step of forming 4), and the step of forming the upper cover dielectric portion (15) by repeatedly applying and drying the dielectric slurry on the upper surface of the capacitor portion (14), In the step of forming the capacitor section (14), a predetermined number of ceramic dielectric layers (17) and internal electrodes (18) are alternately laminated, and only the dielectric slurry is repeatedly applied and dried on the upper surface of the laminated body. To form a dielectric distortion adjusting dielectric part (16), and a predetermined number of ceramic dielectric layers (17) and internal electrodes (18) are alternately laminated on the upper surface of the dielectric distortion adjusting dielectric part (16). A method of manufacturing a laminated green body, comprising: