JPH0382005A - Laminated capacitor - Google Patents

Abstract

PURPOSE:To improve the mutual adhesive properties of dielectric layers, and to obtain a laminated capacitor, in which delamination is difficult to be generated, by oxidizing at least the side edge of an internal electrode and forming an oxide film. CONSTITUTION:In a laminated capacitor, which has a laminated type dielectric, in which a plurality of dielectric layers are piled while interposing internal electrodes 13, 14 on the inside and in which the width of the internal electrodes 13, 14 is made narrower than said dielectric layer and side margin regions 34, 35 are shaped onto the sides of the internal electrodes 13, 14 by the narrowing of the width of the internal electrodes, at least the side edges of the internal electrodes 13, 14 are oxidized, and oxide films are formed. The first and second side faces of a sintered body 25 prepared while the width of the internal electrodes 13, 14 is made the same as that of a ceramic green sheet are covered with resist materials 26a, 26b, and third and fourth side faces 25c, 25d are etched, thus shaping the side margin regions 34, 35. An external electrode is formed, and the third and fourth side faces 25c, 25d of the sintered body 25 are oxidized.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a multilayer capacitor, and more specifically, to a multilayer capacitor having a structure in which the adhesion strength between an internal electrode and a dielectric layer is increased. .

[Conventional technology]

Multilayer capacitors are widely used to make capacitors smaller and larger in capacity. For an m-layer capacitor, for example, as shown in FIGS. 2(a) and 2(b), ceramic green sheets 3.4 coated with internal electrode materials 1 and 2 made of conductive paste are prepared, and a plurality of each are alternately applied. It is obtained by laminating the sheets, pressing the resulting laminate in the thickness direction, burning it, and forming an external electrode on the side surface of the easily sinterable body from which the internal electrode material 1.2 is pulled out.

By the way, the internal electrode material 1.2 formed on the ceramic green sheets 3, 4 extends from the first edge 3a, 4a to the second edge 3b of each ceramic green sheet 3.4.
, and are formed to extend toward the 4b side. In addition, each internal electrode material 1.2 is a ceramic green sheet 3.
.

The side margin region 5 is provided by the internal electrode material 1
．． This is to improve the adhesion between the ceramic green sheets located above and below 2 and to prevent the internal electrode materials 1.2 from coming into contact with each other on the side surfaces of the sintered body after sintering.

[Technical problem to be solved by the invention] In the multilayer capacitor as described above, when trying to obtain a larger capacity by using a sintered body of a predetermined size, the side margin area 5
It is necessary to narrow the width X. Therefore, conventionally, the width X of the side margin region 5 has been reduced to the extent possible.

However, if the width X of the side margin region 5 is made considerably narrower, the adhesion between the ceramics located above and below the internal electrode materials 1 and 2 will be impaired, and layer peeling called so-called delamination tends to occur. Met.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a multilayer capacitor in which the adhesion between dielectric layers is further improved and delamination is less likely to occur.

[Means for solving technical problems]

The present invention has a laminated dielectric in which a plurality of dielectric layers are laminated with internal electrodes interposed therebetween, and the width of the internal electrodes is narrower than that of the dielectric layers. A multilayer capacitor in which a side margin region is provided on the side of an electrode is characterized by having the following configuration.

That is, at least the side edges of the internal electrodes are oxidized to form an oxide film.

[Effect]

Since at least the side edges of the internal electrodes are oxidized to form an oxide film, the nuclear oxide film forms a chemical bond with the dielectric layer, increasing the bonding strength between the internal electrodes and the dielectric layer. Therefore, even if the internal electrode area is expanded and the side margin area is narrowed, the bonding strength between the dielectric layers located above and below is increased, so layer peeling and delamination are prevented from occurring.

[Explanation of Examples]

A manufacturing method according to an embodiment of the present invention will be described with reference to FIGS. 3 to 11. This embodiment is applied to a multilayer capacitor using dielectric ceramics.

FIG. 3 is a perspective view for explaining a ceramic green sheet as a dielectric layer used in the production of this example and an internal electrode material formed thereon. Internal electrode materials 13 and 14 are formed in the form of a film on the upper surfaces of the rectangular ceramic green sheets 11 and 12, respectively.

Ceramic Green Sea) 11 and 12 are obtained by shaping a ceramic slurry mainly made of dielectric ceramic into the shape shown in the figure.

The internal electrode materials 13 and 14 are constructed by applying a conductive paste mainly composed of a conductive material such as Ni or Cu. The materials that make up the internal electrode material are:
In addition to Ni and Cu, various metal materials such as Ag or Ag-Pd can be used. However, in this embodiment, it is necessary to use a material that can be etched with an appropriate etchant during etching, which will be described later.

The internal electrode material 13 is a rectangular ceramic green sheet) 1
It is formed so as to extend from one end edge 11a of 1 toward the opposite end edge llb and not to reach end edge flb. Further, the width of the internal electrode material 13 is the same as the width of the ceramic green sheet ll. That is, the side edges 11c, 1 of the ceramic green sheet 11
The internal electrode material 13 is formed over the entire width of 1d.

The internal electrode material 14 is also configured in the same manner as the internal electrode material 13. However, Serajutsuk Green Sea) 11.
When stacking 12, internal electrode material 13 and internal electrode material 14
Ceramic green sheet 1 with internal electrode material 14 drawn out so that
One edge 12a of the ceramic green sheet 11
It is located on the opposite side to one end edge 11a of.

By alternately stacking a plurality of ceramic green sheets 11 and 12 shown in FIG. 3, a laminate 15 shown in FIG. 4 can be obtained. In the laminate 15, collection 1. 2nd Seraju Ivy Green Sea) 11 and 3 pieces of 12 each,
The ceramic green sheets 1-16 are laminated alternately, and the ceramic green sheets 1-16 to which no internal electrode material is applied are further laminated on the top (or on the bottom if necessary).

Here, one of the three internal electrodes 13a to 13C is placed on the first side surface 15a of the laminate 15, and the other internal electrode material 14a is
14c are drawn out to the second side surface 15b. Also,
The internal electrode materials 13a to 13c and 14a to 14C are also exposed to the 3rd and fourth side surfaces 15c and +5d of the 11-layer body 15.

In order to obtain the laminate 15, in the actual mass production process, it is preferable to use the mother ceramic green sheet shown in FIG. The maintenance internal electrode material 18 extends from one end edge 17a to the other end edge 17b.
a, 18b are formed. Similarly, the thick internal electrode material 2 is also placed on the ceramic green sheet 19 as the thick electric sheet.
0a and 20b are formed from one edge 19a of the ceramic green sheet 19 to the other edge 19b.

Then, a plurality of ceramic green sheets 17 and 19 are alternately stacked in the direction shown in the figure, and cut at a portion corresponding to the portion along the dashed-dot lines A and B, resulting in a laminate 15 shown in FIG. Many similar structures can be obtained.

In this way, by using the mother cell electric green sheets 17 and 19, the laminate 15 shown in FIG. 4 can be efficiently mass-produced. Moreover, the laminate 1 in FIG.
5, each internal electrode material 13a to 13c, 14a to 14e
The third. It is formed in such a width that it is also exposed to the fourth side surfaces 15e and 15d.

Therefore, the ceramic green sheet 17°19 in Figure 5
Even if some misalignment occurs in the direction of arrow C in FIG. 5 when laminating the internal electrode materials, no misalignment of the internal electrode materials will occur in the direction of arrow C in the obtained laminated dielectric 15. Therefore, even if some unavoidable lamination misalignment occurs during lamination of the moat ceramic electric green sheets 17, 19, it is possible to stably obtain the laminated body 15 with little variation in electrode type and area.

In addition, in the conventional example shown in FIG. 2, when a conductive paste for forming the internal electrode material 1 is applied, the surface tension of the paste causes the internal electrode material 1 to change as shown in FIG. 6(a). A raised portion 21a is provided on the side edge.

21b was formed. Therefore, when a plurality of ceramic green sheets are laminated, the thickness of the internal electrode material is not uniform, which is one of the causes of layer peeling after sintering.

On the other hand, in this embodiment, as shown in a corresponding cross-sectional view in FIG. Since the internal electrode material 13 can be formed completely, the thickness of the internal electrode material 13 is uniform in the width direction. Therefore, the occurrence of delamination caused by uneven wear of the internal electrode material can be effectively prevented.

Furthermore, in this example, the internal electrode material is formed to have a width that extends to the entire width of the ceramic green sheet.

This also has the effect of reducing the number of electrode pattern documents and reducing production costs.

Returning to FIG. 4, prior to firing, the laminate 15 is pressed in the thickness direction so that the ceramic green sheets are brought into close contact with each other. In this case, in the laminate 15 of this embodiment,
Internal electrode materials 13a to 13c.

14a to 14c are the third. Since it is formed to span the entire width between the fourth side surfaces 15c and 15a,
As shown in the schematic cross-sectional view of FIG. 7(b) along the line, the pressure bonding can be performed so that the thickness becomes uniform in the Y direction of FIG. 4.

On the other hand, in the conventional example using the ceramic green sheet shown in FIG. The thickness is thinner in the part Z where the regions are formed, and the difference between the thickness of the laminate in the part where the internal electrode materials 1 and 2 are formed and the thickness of the side region where the side margin regions are formed. As a result, delamination tends to occur on the side surfaces of the resulting sintered body.

Therefore, in the laminate of this example, the occurrence of delamination due to such reasons can be effectively prevented.

Next, the laminated body 15 shown in FIG. 4 which has been crimped in the lamination direction is fired to obtain a sintered body as a laminated dielectric. In the laminated body of this example, the internal electrodes exposed on the side surfaces , serves as a medium that promotes sintering inside the dielectric, and sintering can be performed well in a short time. Furthermore, as shown in FIG. 8, the first and second sides of the obtained sintered body 25 are coated with resist materials 26a and 26b.
Cover with The resist materials 26a and 26b are made of a material that is not attacked by an etchant used in etching to be described later, and for example, synthetic resin such as epoxy resin can be used.

The internal electrode material 13 is baked into the sintered body 25 when the ceramic is fired.
a to 13c and 14a to 14c are formed. In addition,
The reference numbers of the internal electrodes will be explained using the same reference numbers as those of the internal electrode materials described above.

Each of the internal electrodes 13a-13c, 14a-14c is connected to the third electrode of the sintered body 25, except for the portions covered with the resist materials 26a, 26b. It is exposed on the fourth side surfaces 25c and 25d.

Next, the third. Fourth side 25c, 25
d is etched using an etchant capable of etching the material constituting the internal electrodes 13a-13c, 14a-14c. As an etchant, for example, a strong acid such as nitric acid can be used, but as an internal electrode material, Cu
When a metal material other than Ni is used, an appropriate etchant capable of etching such a metal material is used.

The state after etching is shown in a plan sectional view in Fig. 9.
As is clear from the figure, in the sintered body 25, the two sides 32 and 33 adjacent to the edge 31 where the internal electrode 13a is drawn out to the first side surface 25g of the sintered body 25 are Margin area 34°35 as 3rd. fourth side 25c,
25d, the third. Fourth aspect 25
c, has been retreated inward from 25d. This means that both side edge portions of the internal electrode 13a are etched by etching, thereby forming side margin regions 34 and 35.

Side margin regions are similarly formed in the other internal electrodes 13b, 13c, and 14a to 14c.

Further, as shown in an enlarged view in FIG. 10, voids 34a and 35a are formed by etching in the portion where the side margin region is formed.

After etching, the sintered body 25 is washed with water or the like to remove the etchant. However, it is difficult to completely remove the residual etchant, especially the etchant remaining in the voids 348.35a, by only washing with water. Therefore, in this embodiment, the sintered body 25 is next placed in a heated atmosphere, Spatter and remove residual etchant.

Note that the above-mentioned heating may utilize heat given in the step of baking the external electrodes, which will be described later. In that case, the removal of the residual etchant and the baking of the external electrodes can be performed in the same step.

Further, the purpose of removing the residual etchant is to prevent corrosion of the internal electrodes due to the residual etchant. Therefore, a method other than heating may be used as long as it is possible to remove the etching effect.For example, if the etchant is a strong acid, the remaining etchant may be neutralized by immersion in an alkaline solution.

Following the removal of the residual etchant, the resist material 26
g, remove 26b. The resist materials 26a and 26b can be removed by mechanical polishing, a method using chemicals, or the like.

In this embodiment, the side margin j1M34.35 is formed by etching, so the third. A side margin region with an accurate width can be formed inward from the fourth side surfaces 25c and 25d. Moreover, since the side margin regions 34 and 35 are formed after the ceramic green sheets and internal electrode materials are laminated to obtain a laminate, an extra width of side margin is required to take into consideration lamination misalignment, etc. There is no need to form a side margin region 34. In other words, the width of the side margin region 34 is narrower than in the conventional example.
35 can be formed. Therefore, it can be seen that a small-sized, large-capacity multilayer capacitor can be realized.

Note that when the laminate 15 is obtained, the internal electrode material may sag from the portion exposed on the side surface, but even if such sagging internal electrode material exists, it is reliably removed by the etching described above. .

Next, by applying IT paste mainly composed of Ag, for example, to the surface from which the resist materials 26a and 26b have been removed and baking it, a pair of external electrodes 36 and 37 are formed, as shown in FIGS. 1 and 11. form. The external electrode 36 is connected to the internal electrodes 13a-13e, and the external electrode 37 is connected to the internal electrodes 14a-14a.
14e.

Finally, after forming the external electrodes 36 and 37, the sintered body 2
3rd of 5. The oxidation treatment of the fourth side surfaces 25e and 25d is accomplished, for example, by heating the multilayer capacitor shown in FIG. 11 for a predetermined period of time in an oxidizing atmosphere. In this embodiment, on the third and fourth side surfaces 25C125d sides of the sintered body 25, the internal electrodes 13ax13c are
.

Because the side edges of 14ax14c are arranged, and because the gaps 34a + 35a in FIG. 10 are formed, the side edges of the internal electrodes are easily oxidized by the oxidizing atmosphere (thereby An oxide film is formed on the edge.The formation of this oxide film effectively increases the adhesion strength between the internal electrode and the ceramic.This is because when oxidized, the dielectric ceramic and the heel electrode This is because a chemical bond is created between the two.

Therefore, by performing the oxidation treatment as described above, it is possible to further improve the adhesion of the internal electrodes 13a to 13e, 14a to 14c, etc. to the dielectric ceramic.

Note that the above oxidation treatment may be performed at any stage after the side margin regions 34.35 are formed by etching, that is, the oxidation treatment may be performed prior to the formation of the external electrodes 36.37. .

Preferably, after the oxidation treatment, a synthetic resin such as an epoxy resin is injected under pressure into the gaps 34a and 35a in FIG.
The gaps 34a and 35a of d can be sealed.

Note that as the sealing material, in addition to synthetic resin, any material such as rubber can be used.

The above-mentioned sealing treatment may also be performed after the formation of the external electrodes, or may be performed prior to the formation of the external electrodes.

Further, in the above embodiment, the pair of external electrodes 36 and 37 are formed after etching, but the external electrodes may be formed prior to etching.

In the above embodiment, the internal electrodes 13a to 13e, 14ax1
Since the electrode 4e is made of inexpensive Ni or Cu, the electrode cost can be reduced. In addition, the mother ceramic green sheet can be I
ff layer, the manufacturing process is simplified,
The mass production cost of multilayer capacitors can be effectively reduced.

Preferably, the side surfaces of the sintered body on which the external electrodes 36 and 37 are formed are coated with a conductive paste mainly composed of Ni, and then the external electrodes 36 and 37 are formed, so that the internal electrodes and the external The reliability of electrical connection with the electrode can be increased.

Further, instead of Ni, another conductive material layer may be applied to the first and second side surfaces 25a and 25b of the sintered body 25. In that case, if a material that is not etched by the etchant is used, It can also have the functions of the resist materials 26a and 26b described above. That is, the resist materials 26a and 26b can be used as base electrodes for forming external electrodes. In this case, removal of the resist material is not necessary.

In the embodiments described above, the side edges of the internal electrodes were etched using a chemical agent such as nitric acid as an etchant.
Actual etching can be performed by immersing the sintered body in an etchant, or by storing the etchant in a rotating barrel, placing the sintered body into the barrel, and rotating the barrel.

In the embodiments described above, the side margin regions 34 and 35 were formed by etching, but the present invention can also be applied to multilayer capacitors in which side margin regions are formed by other methods. That is, even in the conventional example described with reference to FIG. 2, the bonding strength between the dielectric ceramic and the internal electrodes can be similarly increased by forming the oxide film of the present invention. However, if the voids 34a and 35a are formed as in the above embodiment, the oxide film can be formed more easily and reliably.

In the embodiments described above, ceramic green sheets were used as dielectric sheets, but the present invention is limited to multilayer ceramic capacitors formed by laminating a plurality of ceramic green sheets and firing them together with internal electrode materials. In other words, a dielectric resin film can be used as the dielectric sheet as long as it can form a chemical bond with the internal electrode material through oxidation treatment, and the present invention is also applicable to so-called laminated film capacitors. be able to.

Furthermore, the present invention can also be applied to a wound type capacitor formed by winding a long ceramic green sheet or a resin film together with an internal electrode formed on its main surface. It should be pointed out that wound type capacitors are also included in the multilayer capacitors referred to in the present invention (
.

〔Effect of the invention〕

As described above, according to the present invention, at least the side edges of the internal electrodes are oxidized to form an oxide film. When this oxide film is formed, the internal electrodes and the dielectric layer are bonded by chemical bonds, so the bonding strength between the dielectric layers above and below the internal electrodes is increased, and the stacked dielectric layers are bonded together. The adhesion strength is increased. Therefore, even if the internal electrode area is increased and the side margin area is narrowed, delamination can be effectively prevented from occurring.

Therefore, according to the present invention, it is possible to stably obtain a smaller and larger capacity multilayer capacitor.

[Brief explanation of drawings]

Figure 1 is a cross-sectional plan view of a multilayer capacitor according to an embodiment of the present invention, and Figures 2 (a) and (b) are ceramic green sheets used to manufacture conventional multilayer capacitors and the ceramic green sheets formed thereon. Each plan view showing the shape of the internal electrode material and FIG. Perspective view, 4th
The figure is a perspective view showing a laminate, FIG. 5 is a perspective view for explaining the process of laminating mother ceramic green sheets, and FIG.
Figures (a) and (b) are cross-sectional views for explaining the shapes of the side edges of internal electrode materials in conventional examples and examples, and Figures 7 (a) and (b) are, respectively, 7(a) and 8(b) are schematic cross-sectional views for explaining the shapes of the laminates after crimping in conventional examples and examples; FIG. The figure is a perspective view showing the state in which resist material is applied to the side surface of the sintered body, Figure 9 is a plan cross-sectional view for explaining the shape of the internal electrode after etching, and Figure 1O is a schematic diagram showing the voids created by etching. FIG. 11 is a perspective view of a multilayer capacitor according to an embodiment of the present invention. In the figure, 11.12 is a ceramic green sheet as a dielectric layer, lla, llb, 12a, 12b are edges, llc, lid, 12c, 12d are side edges, 13,
13a-13c, 14.14a-14c are internal electrode materials,
25 is a sintered body, 25a and 25b are first. Second aspect, 2
5c and 25d are the third. On the fourth side, 34.35 is a lower margin region, 34a and 35a are gaps, and 36.37 is an external electrode.

Claims (1)

[Claims] It has a laminated dielectric in which a plurality of dielectric layers are laminated with internal electrodes interposed therebetween, and the width of the internal electrodes is narrower than that of the dielectric layers. A multilayer capacitor in which a side margin region is provided on a side of an internal electrode, wherein at least a side edge of the internal electrode is oxidized to form an oxide film.