JPH07123097B2 - Manufacturing method of multilayer capacitor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a multilayer capacitor, and more particularly to a method for manufacturing a multilayer capacitor having an improved external electrode forming method.

[Conventional technology]

In the conventional method of manufacturing a multilayer capacitor, first, a ceramic sintered body having a structure in which a plurality of internal electrodes are arranged so as to overlap with each other with a ceramic layer interposed therebetween and which is alternately drawn out to both end faces is prepared. . Next, a conductive paste such as an Ag paste is printed on both end faces of the ceramic sintered body and baked to form a first external electrode layer. Next, Ni is plated on the first external electrode layer, and Sn or Sn having excellent solderability is further deposited on the Ni plated layer.
The external electrode was formed by plating / Pb alloy. That is, the external electrodes are the first external electrode layer made of Ag, the second external electrode layer made of Ni, and Sn or Sn / Pb.
It was constituted so that it may have the 3rd external electrode layer which consists of.

Therefore, in the conventional external electrode forming method, it is necessary to perform the plating process twice after baking the Ag-containing paste. On the other hand, the first external electrode layer formed by baking the Ag paste has a large number of pores inside in the baked state. Therefore, after performing the plating process twice after forming the first external electrode layer by baking,
There is a problem that the plating solution penetrates into the ceramic sintered body through the pores. This invasion of the plating solution is particularly noticeable at the end surface portion of the sintered body where the internal electrode is drawn out, that is, it enters the ceramic sintered body along the main surface of the internal electrode from the portion where the internal electrode is drawn out. Tended to. As a result, there is a problem that the layer peeling and delamination of the ceramic sintered body are likely to occur due to the penetration of the plating solution.

As a solution to the above problems, Japanese Patent Publication 1-53
No. 497 discloses a method of impregnating the first external electrode layer with an anaerobic adhesive after baking an Ag paste.

Further, Japanese Patent Publication No. 1-55566 discloses a method of using a thermosetting synthetic resin dissolved in a solvent as a chemical to impregnate the first external electrode layer.

[Problems to be Solved by the Invention]

However, in the method disclosed in Japanese Examined Patent Publication No. 1-53497, the anaerobic adhesive is cured at room temperature, so the impregnation of the anaerobic adhesive into the first external electrode layer is performed at a low temperature of about 4 ° C. Had to be done in. Further, an organic solvent must be used to remove an excessive amount of the anaerobic adhesive after the impregnation, so that there is a problem that the working environment is deteriorated by the organic solvent. Furthermore, since it is anaerobic, the adhesive often hardens in the middle of the pores, making it difficult to completely seal the pores. In addition, there is a problem that a special device such as aeration is required for storing the anaerobic adhesive.

On the other hand, in the method disclosed in Japanese Patent Publication No. 1-55566,
Since the impregnating agent is a solvent-type thermosetting adhesive, the volume shrinkage during curing is large. Therefore, even if the fine pores are impregnated, there is a problem in that the volume contraction impairs the hermeticity, and sufficient sealing cannot be performed. Further, since the thermosetting adhesive contains gasoline as a solvent and a cleaning agent containing gasoline is used as a cleaning agent after impregnation, it is necessary to take special care in handling.

Therefore, an object of the present invention is to provide a method for manufacturing a multilayer capacitor including a step of easily and surely sealing the pores in the first external electrode layer formed by baking a conductive paste. Especially.

[Means for Solving the Problems]

The method for manufacturing a multilayer capacitor of the present invention is characterized by including at least the following steps.

That is, a step of preparing a ceramic sintered body having a structure in which a plurality of internal electrodes are overlapped with each other via a ceramic layer and having a structure in which both end surfaces are alternately drawn out, and both end surfaces of the ceramic sintered body A step of forming a first external electrode layer by printing a conductive paste on and baking it, and placing the sintered body on which the first external electrode layer is formed in a monomer solution of a water-soluble thermosetting resin. By immersing, vacuum suctioning and then applying pressure, removing the ceramic sintered body from the thermosetting resin monomer liquid after stopping the pressurization and washing, and heating the washed ceramic sintered body, The method includes a step of polymerizing and curing a thermosetting resin impregnated in the external electrode layer, and a step of plating a second external electrode layer on the first external electrode layer.

[Action]

In the manufacturing method of the present invention, the thermosetting resin monomer liquid is used for sealing the first external electrode layer formed by baking the conductive paste. Moreover, since the thermosetting resin monomer is impregnated by being pressed while being immersed in the monomer liquid of the thermosetting resin, it does not cure in the middle of the pores, Up to the thermosetting resin monomer is impregnated.

Further, since the thermosetting resin monomer liquid is used, vacuum suction and pressurization can be performed at room temperature. Therefore, no special cooling device is required.

Furthermore, since the water-soluble thermosetting resin monomer liquid is used, washing can be performed with water, and the use of harmful organic solvents can be omitted. Moreover, the impregnated thermosetting resin monomer is easily polymerized and hardened only by heating with hot water or the like.

Further, since the thermosetting resin monomer liquid is impregnated by using vacuum suction and pressurization together, even if the pores formed in the first external electrode layer have a complicated shape, The thermosetting resin monomer liquid is surely impregnated therein.

[Explanation of Examples]

Hereinafter, a manufacturing method according to an embodiment of the present invention will be described with reference to the drawings.

First, as shown in the sectional view of FIG. 1, a ceramic sintered body 1 is prepared in which internal electrodes 2a to 2d are arranged so as to overlap each other with a ceramic layer interposed therebetween. The internal electrodes 2a to 2d are alternately drawn out to the end faces 1a and 1b of the ceramic sintered body 1. Such a ceramic sintered body is prepared according to a well-known manufacturing method for a laminated capacitor.

Next, as shown in FIG. 1, the end surface of the ceramic sintered body 1
A conductive paste containing Ag is printed on 1a and 1b and baked to form first external electrode layers 3a and 3b. By baking, a large number of pores 4 are usually formed in the first external electrode layers 3a, 3b. As described above, the pores 4 are a cause of impairing the airtightness of the multilayer capacitor and causing layer peeling of the ceramic layer after plating.

In this embodiment, the ceramic sintered body 1 prepared as described above is immersed in a water-soluble thermosetting resin monomer liquid 5 at room temperature, as shown in FIG. Reference numeral 6 denotes a tank in which the thermosetting resin monomer liquid 5 is stored. As the water-soluble thermosetting resin monomer liquid, one that is liquid at room temperature and that is polymerized and solidified by heating is used. As such a thermosetting resin, for example, Daiichi Kasei Kogyo Co., Ltd., trade name; Seal First
An acrylic thermosetting resin such as GE-10 is used.

As shown in FIG. 2, the ceramic sintered body 1 is immersed in the thermosetting resin monomer liquid 5. Then, in the immersed state, it is sucked with a vacuum pump for 15 minutes, and then pressurized to a pressure higher than atmospheric pressure. By this pressurization, the thermosetting resin monomer liquid 5 is impregnated into the pores 4 of the first external electrode layers 3a and 3b. This pressurization is performed for about 5 minutes, although it depends on the viscosity of the thermosetting resin monomer liquid 5 and the pressure applied.

Next, after stopping the pressurization and returning to normal pressure, the ceramic sintered body 1 that has been immersed is taken out from the thermosetting resin monomer liquid 5. After that, the excess thermosetting resin monomer liquid adhering to the surface of the ceramic sintered body 1 is removed by washing with water.

In addition, when washing with water, the excess thermosetting resin monomer liquid adhering to the surfaces of the ceramic sintered body 1 and the first external electrode layers 3a and 3b is removed, but inside the pores 4. The impregnated thermosetting resin monomer liquid is not removed due to its surface tension. That is, the pores 4 are kept filled with the uncured thermosetting resin monomer liquid.

Thereafter, the ceramic sintered body 1 is immersed in hot water of 90 ° C. for 15 minutes and heated to polymerize and cure the filled thermosetting resin monomer. Then, the ceramic sintered body 1 is taken out of the hot water. In this way, FIG. 3 and FIG.
As shown in the figure, it is possible to obtain a structure in which the thermosetting resin 7 is filled in the pores of the first external electrode layers 3a, 3b. The thermosetting resin 7 is hardened by immersing it in hot water. Instead of immersing it in hot water, the ceramic sinter 1 is placed in a constant temperature bath at about 120 ° C. and heat-hardened. May be. However, the immersion in hot water can cure the uncured thermosetting monomer liquid impregnated into the pores more quickly.

Next, Ni is electrolytically plated on the first external electrode layers 3a and 3b to form second external electrode layers 8a and 8b (see FIG. 5).

Further, following the formation of the second external electrode layer made of Ni,
As shown in FIG. 6, third external electrode layers 9a and 9b made of Sn or Sn / Pb are formed by plating.

The formation of the second and third external electrode layers 8a, 8b, 9a, 9b is performed according to a conventionally known external electrode forming method.

In the manufacturing method of this embodiment, the second and third external electrode layers 8a, 8b,
Prior to forming 9a, 9b by plating, since the pores 4 in the first external electrode layers 3a, 3b are sealed with the thermosetting resin 7, even if immersed in a plating solution, The plating solution passes through the first external electrode layers 3a, 3b and the ceramic sintered body 1
Accidents such as entering the inside can be reliably prevented.

Moreover, since the water-soluble thermosetting resin monomer liquid is used, the above-mentioned operations such as immersion in the thermosetting resin monomer liquid and washing can be easily performed. Also,
Regarding the impregnation of the thermosetting monomer liquid 5 into the pores 4,
It is performed by sucking and pressing the ceramic sintered body 1 in a state of being immersed in the thermosetting monomer liquid 5. Therefore,
The thermosetting resin monomer liquid 5 can be surely impregnated into the pores 4.

When a multilayer capacitor was manufactured according to the manufacturing method of the above example, the compressive strength in the length direction of the ceramic sintered body 1 was as shown in Table 1 below. Also,
For comparison, the compressive strength in the thickness direction was similarly measured for the conventional products manufactured in the same manner except that the first external electrode layers 3a and 3b were not impregnated with the thermosetting resin 7. As a result, the results shown in Table 1 below were obtained.

As is clear from Table 1, in the conventional example, compared with the compressive strength after forming the first external electrode layer, the compression strength after forming the second and third external electrodes (that is, after plating) It can be seen that the strength of the multilayer capacitor of the present example is rather lowered, but rather increased, while the strength is greatly reduced.

The Q value of the conventional laminated capacitor was about 2000, while the Q value of the laminated capacitor of the example impregnated with the thermosetting resin monomer liquid was 10,000 or more. That is, it can be seen that the Q value can be prevented from decreasing by impregnating the thermosetting resin monomer liquid.

Furthermore, when many prototypes of the multilayer capacitors of the above-described example and the conventional example were made, delamination occurred at a rate of 2 per 1000 in the multilayer capacitor of the conventional example, whereas in the multilayer capacitor of the example, delamination occurred. Was never generated.

Although the Ag-containing paste is used to form the first external electrode layer in the above-described embodiments, a conductive paste containing another conductive metal such as Ag-Pd may be used instead of Ag.

Further, in the above-mentioned embodiment, after forming the second external electrode layer made of Ni, the third external electrode layer made of Sn or Sn / Pb is formed by plating. However, in some cases, a Sn or Sn / Pb layer may be directly formed as the second external electrode layer.

In the above description of the present invention, the first external electrode layer is impregnated with the thermosetting resin monomer, but impregnation with the outer surface of the sintered body is not hindered.

〔The invention's effect〕

According to the present invention, the thermosetting resin monomer liquid is impregnated into the pores of the first external electrode layer by immersing in the water-soluble thermosetting resin monomer liquid and applying pressure thereto. The pores in the external electrode layer can be reliably filled with the thermosetting resin monomer liquid, and the pores can be sealed only by heating in the subsequent step. Moreover, since the water-soluble thermosetting resin monomer liquid is used as the impregnating agent, it is not necessary to pay special attention to handling. In addition, the conventional method using an anaerobic adhesive requires a cooling device because it needs to be processed at a low temperature, requires a special device such as an aeration device for storage, and further requires a thermosetting adhesive containing gasoline. In the conventional example used, since gasoline was used as a solvent, it was necessary to pay attention to handling, and there was also a problem in terms of safety, whereas in the production method of the present invention, the water-soluble thermosetting resin monomer is used. Since a liquid is used, such a special device is not required. In addition, the working environment is not deteriorated. Furthermore, since the surface after impregnation can be washed with water,
The whole process of impregnation and washing can be carried out quickly.

Therefore, according to the present invention, without requiring a special device,
Moreover, it becomes possible to mass-produce a highly reliable multilayer capacitor by an extremely simple process.

[Brief description of drawings]

FIG. 1 is a sectional view showing a state in which a first external electrode layer is formed in a manufacturing method according to an embodiment of the present invention, and FIG. 2 is a sectional view for explaining a step of immersing in a water-soluble thermosetting monomer liquid. Fig. 3 is a sectional view showing a state where the thermosetting resin monomer impregnated in the pores is cured, and Fig. 4 is a partially cutaway sectional view showing an enlarged main part of Fig. 3, Fig. 5 Is a sectional view showing a state in which a second external electrode layer is formed, and FIG. 6 is a sectional view showing a state in which a third external electrode layer is formed. In the figure, 1 is a ceramic sintered body, 2a to 2d are internal electrodes, 3a and 3b are external electrodes, 4 are pores, 5 is a water-soluble thermosetting resin monomer liquid, 7 is a thermosetting resin, and 8a and 8b. Indicates a second external electrode layer, and 9a and 9b indicate a third external electrode layer.

Claims (1)

[Claims] 1. A step of preparing a ceramic sintered body having a structure in which a plurality of internal electrodes are overlapped with each other with ceramics interposed therebetween, and both end surfaces of the ceramic sintered body are alternately drawn out; A step of forming a first external electrode layer by printing a conductive paste on both end faces and baking it; and a step of forming a ceramic sintered body on which the first external electrode layer is formed in a water-soluble thermosetting resin monomer liquid The step of immersing in a vacuum and then vacuum-pressurizing, the step of removing the ceramic sintered body from the thermosetting resin monomer liquid after the pressurization is stopped and washing, and heating the ceramic sintered body Of the thermosetting resin monomer impregnated in the external electrode layer of
A method of manufacturing a multilayer capacitor, comprising: a curing step; and a step of plating a second external electrode layer on the first external electrode layer.