JP2000077259A - Stacked capacitor and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stacked capacitor whose connection resistance between an external electrode and an internal electrode is low and stable, and its manu facturing method. SOLUTION: This stacked capacitor is comprised of a laminated body 6, which is formed by laminating a plurality of insulation sheets 4 in which internal electrodes 2 and 3 are formed, while cover sheets are arranged on the upper and lower sides thereof, and by sintering the whole body. The stacked body 6 is provided with semiconductor layers 12 on its both end faces. The internal electrodes 2 and 3 are electrically connected respectively with external electrodes 22 and 23 via the semiconductor layer 12. A reducing agent is applied to both end faces of the stacked body 6 and a plate for forming external electrodes is applied thereto, and then the stacked body 6 is heated at the same time so as to diffuse the reducing agent in the laminated body 6 as well as form external electrodes 22 and 23. A plated covering film is formed on the external electrodes 22 and 23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a multilayer capacitor and a method for manufacturing the same.

[0002]

2. Description of the Related Art Hitherto, as this type of multilayer capacitor, those described in Japanese Patent Application Laid-Open No. 2-277205 and those described in Japanese Patent Application Laid-Open No. 5-62859 have been known.
The multilayer ceramic capacitor described in Japanese Patent Application Laid-Open No. 2-277205 has a laminated structure in which a dielectric ceramic sheet and a noble metal internal electrode made of Pd or the like are stacked, and a semiconducting agent paste is provided on both end surfaces of the laminated body. Is applied. Thereafter, the laminate is fired in the air to make the laminate porcelain, and the semiconductor agent is thermally diffused into the laminate to reduce both ends of the laminate to form a semiconductor layer. next,
A silver paste is applied to both end surfaces of the stacked body on which the semiconductor layer is formed and baked in air to form external electrodes. In the multilayer ceramic capacitor thus obtained, the internal electrodes and the external electrodes are electrically connected via the semiconductor layer.

In the multilayer ceramic capacitor disclosed in Japanese Patent Application Laid-Open No. 5-62859, a dielectric ceramic sheet and internal electrodes are stacked to form a laminate, which is then fired. Furthermore, after applying a base metal paste such as Zn to both end surfaces of the sintered laminate, a silver paste is applied to isolate the base metal paste from the air, and these are baked in air to form external electrodes, Oxygen contained in the ceramic body of the body is taken into the base metal paste by interparticle diffusion and oxidizes the base metal paste. Thereby, the ceramic body near the end face of the multilayer ceramic capacitor to which the base metal paste has been applied is reduced and becomes a semiconductor layer. In the multilayer ceramic capacitor thus obtained, the internal electrodes and the external electrodes are electrically connected via a semiconductor.

[0004]

SUMMARY OF THE INVENTION However, Japanese Patent Laid-Open No.
In the ceramic capacitor described in Japanese Patent No. 277205 and the ceramic capacitor described in Japanese Patent Application Laid-Open No. 5-62859, the formation of the semiconductor layer and the formation of the external electrode are performed in separate steps. Is oxidized again by oxygen in the air, and the resistance of the semiconductor layer increases, and the connection resistance between the external electrode and the internal electrode increases. Further, the semiconductor layer also has a problem that the heat diffusion during the formation of the external electrode promotes the thermal diffusion of the semiconducting agent and oxygen again, and it is difficult to control the region of the semiconductor layer.

It is an object of the present invention to provide a multilayer capacitor in which the connection resistance between an external electrode and an internal electrode is low and stable, and a method of manufacturing the same.

[0006]

In order to achieve the above object, a multilayer capacitor according to the present invention comprises (a) a plurality of insulating material layers made of a non-reducing material and a plurality of internal electrodes made of a base metal material. And a laminate formed by stacking
(B) a semiconductor layer formed on an end face of the laminate,
(C) an external electrode provided at an end of the stacked body and electrically connected to the internal electrode via the semiconductor layer.

Further, the method for manufacturing a multilayer capacitor according to the present invention is characterized in that (d) an insulating material layer made of a non-reducing material and a plurality of internal electrodes made of a base metal material are stacked, fired and fired. (E) applying a reducing agent to an end face of the sintered laminate, and then applying an external electrode material on the reducing agent; (f) providing the reducing agent with the reducing agent; Simultaneously heat-treating the external electrode material and forming a semiconductor layer on the end face of the sintered laminate by diffusing the reducing agent into the sintered laminate, and forming an external electrode with the external electrode material; , Is provided.

In this manufacturing method, the internal electrode and the insulating material layer are formed such that an end of the internal electrode on the external electrode connection side forms a gap having a predetermined dimension between the edge of the insulating material layer. May be stacked to form a laminate. Alternatively, after stacking the insulating material layer and the internal electrode, when firing, the end of the internal electrode is pulled from the end face of the sintered laminate by shrinkage of the internal electrode, and the internal electrode is The external electrodes may be electrically connected via a semiconductor layer.

[0009]

Since the insulating material layer is made of a non-reducing material, the baking of the external electrode and the formation of the semiconductor layer can be performed simultaneously. Therefore, the semiconductor layer does not have to worry about re-oxidation or re-diffusion of the reducing agent due to baking of the external electrode.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a multilayer capacitor according to the present invention and a method for manufacturing the same will be described below with reference to the accompanying drawings.

[First Embodiment, FIGS. 1 to 4] As shown in FIG. 1, a multilayer capacitor 1 includes a plurality of insulating sheets 4 having internal electrodes 2 and 3 provided on the surface thereof, respectively, And a cover sheet 5 disposed on the upper and lower sides of the stack of the functional sheets 4. As the material of the sheets 4 and 5, a non-reducing material is used. In the present embodiment, a non-reducing dielectric material containing barium titanate as a main component is used. Internal electrodes 2 and 3 are printed, sputtered,
It is formed on the insulating sheet 4 by a method such as vapor deposition. As a material for the internal electrodes 2 and 3, a base metal material is used, and in the present embodiment, a conductive material containing Ni metal is used.

The internal electrode 2 is formed on the sheet 4 at a position closer to the left, and a gap distance g1 is secured between a left end (hereinafter, referred to as an external electrode connection side end) 2a and a left side 4a of the sheet 4. And the right end 2b and the right side 4 of the sheet 4
The gap distance g2 is ensured between the gap distance b and the gap distance b. Similarly, the internal electrode 3 is formed at a position on the right side of the sheet 4 and has a right end (hereinafter, referred to as an external electrode connection side end) 3.
a and a right side 4b of the sheet 4 are secured with a gap distance g1, and a gap distance g2 between the left end 3b and the left side 4a of the sheet 4 is secured. The internal electrodes 2 and 3 are opposed to each other with the sheet 4 interposed therebetween, and form a capacitance.

The above-mentioned insulating sheet 4 and cover sheet 5
Are stacked to form a laminate 6 as shown in FIG. Next, the laminate 6 is fired in a reducing atmosphere with a mixed gas of N ₂ / H ₂ / H ₂ O. The fired laminate 6 is usually polished thereafter, but the internal electrodes 2 and 3 are not polished.
And the external electrodes 22 and 23 to be described later are connected via the semiconductor layer 12, so that it is convenient to omit or simplify this polishing step to reduce the cost.

Next, as shown in FIG. 3, a reducing agent 10 is applied to both end surfaces of the sintered laminate 6. Reducing agent 10
For example, a paste in which a varnish and a solvent are kneaded with a rare earth element as a main component is used. Further, external electrodes 22 and 23 are applied to both ends of the laminate 6 so as to cover the reducing agent 10. These external electrodes 22, 23
As a material for the conductive paste, a conductive paste such as Ag, Ag-Pd, or Cu is used.

Next, the sintered laminate 6 is heated at a temperature of 800.degree.
Heat treatment in a neutral atmosphere for 20 minutes. As a result, the external electrodes 22 and 23 are baked, and
As shown in (1), the reducing agent 10 is thermally diffused into the laminate 6 to form the semiconductor layers 12 at both ends of the laminate 6. Furthermore, in order to prevent silver erosion of the external electrodes 22 and 23 and obtain good solderability, nickel, copper,
A plating film such as solder is formed.

The multilayer capacitor 1 thus obtained is
The baking of the external electrodes 22 and 23 and the formation of the semiconductor layer 12 are performed simultaneously. Therefore, the semiconductor layer 12 does not have to worry about re-oxidation due to baking of the external electrode or re-diffusion of the reducing agent 10. As a result, the diffusion distance of the reducing agent 10, in other words, the semiconductor layer 1
2 has a substantially constant thickness T (see FIG. 4),
The connection resistance between the internal electrodes 2 and 3 and the external electrodes 22 and 23 is low and stable, and the decrease in insulation resistance between the internal electrodes 2 and 3 and the semiconductor layer 12 facing the internal electrodes 2 and 3 is also suppressed.

Further, the multilayer capacitor 1 of the first embodiment will be described in more detail using specific numerical values.

[Evaluation] Non-reducing dielectric sheet (ceramic green sheet) 4 containing BaTiO ₃ as a main component
And an internal electrode paste containing Ni metal is prepared, and the internal electrodes 2 and 3 as shown in FIG.
Green sheet 4 was prepared. This green sheet 4
Were stacked to form a laminate 6. Here, the gap distance g1 is set to 3 so that the external electrode connection side ends 2a and 3a of the internal electrodes 2 and 3 are not exposed to the end surface of the laminated body 6.
0 μm (Example 1), 50 μm (Example 2), 100 μm
m (Example 3), 150 μm (Example 4), 200 μm
(Example 5) was set. On the other hand, the gap distance g2 in Examples 1 to 5 was all set to 300 μm.

After the multilayer capacitors 1 of Examples 1 to 5 were manufactured by the above-described manufacturing method, the results of various measurements are shown in Table 1. For comparison, Table 1 also shows the measurement results of a conventional multilayer capacitor in which the internal electrode and the external electrode are directly connected without forming the semiconductor layer 12. The “diffusion distance” of the reducing agent 10 in Table 1
Is the result of quantitative analysis of the polished surface of the end face of the sintered laminate 6 by an energy dispersive X-ray microanalyzer (EDX).

[0020]

[Table 1]

From Table 1, it can be seen that the number of occurrences of structural defects due to the plating solution in the multilayer capacitors 1 of Examples 1 to 5 is smaller than that of the conventional multilayer capacitor.
External electrodes 22 and 2 are used to improve silver erosion and solderability.
When a plating film such as nickel, copper, solder, or the like is formed on the surface of No. 3, the plating solution penetrates into fine voids (porous pores) of the external electrodes 22 and 23, and the plating solution passes through the internal electrodes and the ceramic body. Reaches the bonding interface. As a result, the adhesion strength at the bonding interface decreases, and peeling or the like may occur at the bonding interface. The structural defect caused by the plating solution refers to peeling or the like caused by the penetration of the plating solution.

The connection resistance between the internal electrodes 2 and 3 and the external electrodes 22 and 23 via the semiconductor layer 12 is also compared with the conventional connection resistance when the internal electrode and the external electrode are electrically connected directly. There is no practical problem.

However, if the gap distance g1 after firing of the internal electrodes 2 and 3 is less than 20 μm, structural defects occur as in the conventional multilayer capacitor. Also, reducing agent 1
If the diffusion distance of 0 does not reach the internal electrodes 2 and 3, electrical connection cannot be obtained. Therefore, the gap distance g1 after firing of the internal electrodes 2 and 3 is set so as to be 20 μm or more. The layer thickness T of the semiconductor layer 12 is set to at least 20 μm or more inside from the end face of the stacked body 6. External electrode 22
This is for ensuring the electrical connection between the internal electrode 2 and the external electrode 23 and the internal electrode 3 reliably and stably.

[Evaluation] Next, as Examples 6 to 10, the gap distance g1 of the internal electrodes 2 and 3 shown in FIG. 1 was set to 100 μm, and the gap distance g2 was set to 300 μm. The laminated body 6 is manufactured. After the paste-like reducing agent 10 and the conductive paste for the external electrodes 22 and 23 are applied to the laminate 6, the laminate 6 is heated at a temperature of 800.
In a neutral atmosphere of 15 ° C., the heat treatment time was 15 minutes (Example 6), 20 minutes (Example 7), 30 minutes (Example 8),
40 minutes (Example 9) and 50 minutes (Example 10) were set. As a result, the external electrodes 22 and 23 are baked, and at the same time, the reducing agent 10 is thermally diffused into the laminate 6 to form the semiconductor layers 12 at both ends of the laminate 6. Next, in the multilayer capacitors of Examples 6 to 10, a plating film is formed on the external electrodes 22 and 23.

Table 2 shows the evaluation results of the multilayer capacitors 1 of Examples 6 to 10 thus obtained. Table 2 also shows, for comparison, evaluation results of a conventional multilayer capacitor having a structure in which an internal electrode and an external electrode are directly connected.

[0026]

[Table 2]

From Table 2, when the heat treatment time is 30 minutes or less, the effect of the present invention is recognized, and the characteristics are clearly improved. However, when the heat treatment time is 40 minutes or longer, the diffusion distance of the reducing agent 10 increases, the insulation distance between the internal electrodes 2 and 3 facing the formed semiconductor layer decreases, and a decrease in insulation resistance is observed. become. Therefore, it is desirable that the diffusion distance of the reducing agent 10 be set within 2/3 of the gap distance g2.

Here, the diffusion distance of the reducing agent 10 is changed by changing the heat treatment time. However, the control of the diffusion distance is not limited to only the heat treatment time. Any method, such as a change, can be used. The kind of the rare earth element which is the main component of the reducing agent 10 is preferably a so-called light rare earth element of La or Pm, but heavy rare earth elements after Sm can be diffused by controlling the heat treatment conditions. Also, the specifications of the rare earth paste are not particularly limited.

[Evaluation] Next, FIG.
The gap distance g1 between the internal electrodes 2 and 3 shown in FIG.
m, the gap distance g2 was set to 300 μm, and evaluation 1
The laminate 6 is manufactured in the same manner as described above. After applying the paste-like reducing agent 10 and the conductive paste for the external electrodes 22 and 23 to the laminate 6, the laminate 6 is subjected to a heat treatment in a neutral atmosphere at a temperature of 800 ° C. for 15 minutes. As a result, the external electrodes 22 and 23 are baked, and at the same time, the reducing agent 10 is thermally diffused into the laminate 6 and the semiconductor layer 12
To form

On the other hand, as Comparative Example 3, a laminate 6 is manufactured in the same manner as in Evaluation 1, except that the gap distance g1 of the internal electrodes 2 and 3 shown in FIG. 1 is set to 200 μm and the gap distance g2 is set to 300 μm. Next, after applying the paste-like reducing agent 10 to the laminate 6, heat treatment is performed for 15 minutes in a neutral atmosphere at a temperature of 800 ° C. Thereby, the reducing agent 10
Is thermally diffused into the laminate 6 to form the semiconductor layers 12 at both ends of the laminate 6. Thereafter, a Cu external electrode paste is applied, and heat treatment is performed again in a neutral atmosphere at a temperature of 800 ° C. for 15 minutes. Thereby, the external electrodes 22 and 23
Was baked.

Next, in the multilayer capacitors of Example 11 and Comparative Example 3, plating films are formed on the external electrodes 22 and 23. Table 3 shows the results of Example 11 thus obtained.
And the evaluation results of the multilayer capacitor of Comparative Example 3 are shown.

[0032]

[Table 3]

As can be seen from Table 3, if the step of forming the semiconductor layer 12 and the step of baking the external electrodes 22 and 23 are separated, the diffusion distance of the reducing agent 10 is increased, and the distance between the external electrodes 22 and 23 and the internal electrodes 2 and 3 is increased. It was found that electrical characteristics such as connection resistance were affected. That is, the diffusion distance of the reducing agent 10 is determined by the time of exposure to the high-temperature neutral atmosphere, and the multilayer capacitor of Comparative Example 3 subjected to the heat treatment twice promotes the diffusion too much. If the short-time heat treatment within 10 minutes can be performed twice, the formation of the semiconductor layer 12 and the external electrode 2
It is believed that baking of 2,23 can be performed in a separate step.
However, heat treatment for a short time of 10 minutes or less is practically impossible, and also increases the number of steps.

[Second Embodiment, FIGS. 5 to 8] As shown in FIG. 5, the multilayer capacitor 31 has internal electrodes 32 and 33
Are provided on the surface, and cover sheets 35 arranged on the upper and lower sides of the stack of these insulating sheets 34 and the like. As the material of the sheets 34 and 35, a non-reducing material is used. In the present embodiment, a non-reducing dielectric material containing barium titanate as a main component is used. The internal electrodes 32 and 33 are
It is formed on the insulating sheet 34 by a method such as printing, sputtering, or vapor deposition. As a material of the internal electrodes 32 and 33, a base metal material is used, and in this embodiment, a conductive material containing Ni metal is used.

The internal electrode 32 is formed at a position on the left side of the sheet 34, and a left end (hereinafter, referred to as an external electrode connection side end) 32 a is exposed on a left side 34 a of the sheet 34.
Further, a gap distance g2 is secured between the right end 32b and the right side 34b of the sheet 34. Similarly, the internal electrode 33 is formed at a position on the right side of the sheet 34, and the right end (hereinafter, referred to as an external electrode connection side end) 33 a is exposed to the right side 34 b of the sheet 34, and is connected to the left end 33 b. A gap distance g2 is secured between the sheet 34 and the left side 34a. The internal electrodes 32 and 33 are
4 to face each other to form a capacitance.

The above insulating sheet 34 and cover sheet 3
5, after being stacked, as shown in FIG.
6 is assumed. Next, the laminate 36 is fired in a reducing atmosphere with a mixed gas of N ₂ / H ₂ / H ₂ O. At this time,
The internal electrodes 32 and 33 are thermally contracted, and the external electrode connection side ends 32a and 33a are respectively drawn in from the end surfaces of the laminate 36 by a distance g1. The distance g1 is 20 μm or more,
The thickness is set to be less than the layer thickness T of the semiconductor layer 42 described later (see FIG. 8). Thereafter, the end face of the sintered laminate 36 is polished by a wet barrel if necessary.
Since 3 is connected to the external electrodes 52 and 53 via the semiconductor layer 42 described later, it is convenient to omit or simplify the polishing step to reduce the cost. .

Next, as shown in FIG. 7, a reducing agent 40 is applied to both end surfaces of the sintered laminate 36. Reducing agent 4
As the material of No. 0, for example, a paste in which a varnish and a solvent are kneaded with a rare earth element as a main component is used. further,
The conductive paste for the external electrodes 52 and 53 is applied to both ends of the laminate 6 so as to cover the reducing agent 40. next,
This sintered laminate 36 is subjected to a heat treatment in a neutral atmosphere at a temperature of 800 ° C. for 20 minutes. Thereby, the external electrode 5
2 and 53 are printed, and as shown in FIG.
The reducing agent 40 thermally diffuses into the stacked body 36 to form the semiconductor layers 42 at both ends of the stacked body 36.

The multilayer capacitor 31 thus obtained
The internal electrodes 32 and 33 and the external electrodes 52 and 53 are electrically connected via the semiconductor layer 42. This capacitor 31 has the same operation and effect as the multilayer capacitor 1 of the first embodiment.

[Other Embodiments] The present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the invention.

When a multilayer capacitor is manufactured, the method is not necessarily limited to a method in which insulating sheets or the like having internal electrodes provided on the surface are stacked and then integrally fired. For example, a multilayer capacitor may be manufactured by a method described below. That is, after an insulating layer is formed from a paste-like insulating material by printing or the like, a paste-like conductive material is applied to the surface of the insulating layer to form internal electrodes. Next, a paste-like insulating material is applied from above the internal electrodes to form an insulating layer in which the internal electrodes are embedded. In the same manner, a capacitor having a laminated structure is obtained while successively coating.

[0041]

As is apparent from the above description, according to the present invention, the baking of the external electrode and the formation of the semiconductor layer can be performed at the same time. There is no worry about re-spread. As a result, the diffusion distance of the reducing agent, in other words, the thickness of the semiconductor layer becomes substantially constant, the connection resistance between the internal electrode and the external electrode becomes low and stable, and the insulation resistance between the internal electrode and the semiconductor layer facing the internal electrode decreases. The reduction is also suppressed, and a highly reliable multilayer capacitor can be obtained.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a first embodiment of a multilayer capacitor according to the present invention.

FIG. 2 is a partial cross-sectional perspective view showing a manufacturing step following FIG. 1;

FIG. 3 is a partial cross-sectional perspective view showing a manufacturing process following FIG. 2;

FIG. 4 is a partial cross-sectional perspective view showing a manufacturing step following FIG. 3;

FIG. 5 is an exploded perspective view showing a second embodiment of the multilayer capacitor according to the present invention.

FIG. 6 is a partial cross-sectional perspective view showing a manufacturing step following FIG. 5;

FIG. 7 is a partial cross-sectional perspective view showing a manufacturing step following FIG. 6;

FIG. 8 is a partial cross-sectional perspective view showing a manufacturing step following FIG. 7;

[Explanation of symbols]

 1, 31 multilayer capacitor 2, 3, 32, 33 internal electrode 4, 34 insulating sheet 5, 35 cover sheet 6, 36 multilayer body 10, 40 reducing agent 12, 42 semiconductor layer 22, 23, 52, 53 ... external electrode g1 ... gap distance

Claims (4)

[Claims] A stacked body formed by stacking a plurality of insulating material layers made of a non-reducing material and a plurality of internal electrodes made of a base metal material; a semiconductor layer formed on an end face of the stacked body; An external electrode provided at an end of the multilayer body and electrically connected to the internal electrode via the semiconductor layer. 2. An insulating material layer comprising a non-reducing material,
After stacking multiple internal electrodes made of base metal material,
Baking to form a sintered laminate, applying a reducing agent to an end face of the sintered laminate, and then applying an external electrode material on the reducing agent; and the reducing agent and the external electrode Simultaneously heat-treating the material and diffusing the reducing agent into the sintered laminate to form a semiconductor layer on the end surface of the sintered laminate, and forming an external electrode with the external electrode material. A method for manufacturing a multilayer capacitor, comprising: 3. The external electrode connection side end of the internal electrode,
3. The laminate according to claim 2, wherein the internal electrode and the insulating material layer are stacked so as to form a gap having a predetermined size between the edge of the insulating material layer. Manufacturing method of die capacitor. 4. When the insulating material layer and the internal electrode are stacked and then fired, an end of the internal electrode is drawn from an end face of the laminate by shrinkage of the internal electrode when the internal electrode is fired. 3. The method for manufacturing a multilayer capacitor according to claim 2, wherein the external electrode is electrically connected to the external electrode via the semiconductor layer.