JPH08148371A - Multilayer ceramic capacitor - Google Patents

Abstract

PURPOSE: To prevent the entrance of plating solution in the case of forming a metallic plating film into a capacitor body by bending the end faces of an inner electrode and a dielectric ceramic layer in the vertical direction. CONSTITUTION: Dielectric ceramic layers 9 and inner electrodes 10a, 11b are alternately stacked in a laminated ceramic capacitor 7. The end faces of the electrodes 10a, 10 and the layers 9 of the capacitor 7 are uniformly bent in the vertical direction, i.e., downward in the vicinity A of the end faces of a capacitor body 8 to be formed. Thus, the entrance of plating solution at the time of forming a metallic plating film on the outer electrode into the body is prevented to enhance the thermal shock resistance and to prevent the deterioration of the electrical characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monolithic ceramic capacitor, and more particularly to a monolithic ceramic capacitor having enhanced thermal shock resistance against a plating bath.

[0002]

2. Description of the Related Art Multilayer ceramic (porcelain) capacitors are
In general, dielectric ceramic layers and internal electrodes are alternately laminated to form a capacitor body, and a pair of external electrodes are electrically connected to the internal electrodes on both end surfaces of the body, where the ends of the internal electrodes are exposed. Is configured to connect. Such a monolithic ceramic capacitor is usually manufactured as follows.

First, a ceramic green sheet is formed by a doctor blade method from a slip in which a powder of a dielectric ceramic material and a binder are sufficiently mixed. On this green sheet, a conductive paste made by mixing a powder of an electrode material composed of silver (Ag) -palladium (Pd) alloy and a binder to form a paste is printed as an internal electrode pattern by a screen printing method or the like. A desired number of layers are laminated, pressure-bonded and cut to produce a green chip.
The green chip is fired to form a capacitor body, and a conductive paste made of Ag or Ag-Pd alloy for the external electrode is applied and baked on both end surfaces of the capacitor body where the internal electrode ends are exposed. An external electrode is formed, and a metal plating film such as nickel (Ni) plating, tin (Sn) plating, or solder plating is formed on the surface of the external electrode to form a monolithic ceramic capacitor.

The internal structure of the monolithic ceramic capacitor obtained as described above is as shown in the sectional view of FIG. In the monolithic ceramic capacitor 1 of FIG. 2, reference numeral 2 denotes a capacitor body, in which dielectric ceramic layers 3 and internal electrodes 4a and 4b are alternately laminated. 5a and 5b are external electrodes, 6a and 6b are metal plating films formed thereon, and the external electrodes 5a and 5b are electrically connected to the ends of the internal electrodes 4a and 4b on both end faces of the capacitor body 2. are doing.

As shown in the figure, in the conventional monolithic ceramic capacitor 1, the internal electrodes 4a and 4b are formed flat inside the capacitor body 2, and the internal electrodes 4a and 4b are formed.
b and the external electrodes 5a and 5b were connected substantially vertically at the end of the capacitor body 2.

[0006]

However, in such a conventional monolithic ceramic capacitor 1, when the metal plating films 6a and 6b are formed on the external electrodes 5a and 5b, the plating bath liquid is used. Penetrating 5b,
Internal electrodes 4a and 4b and internal electrode 4 on the capacitor body 2 side
There was a case where it penetrated into the interface between a.4b and the dielectric ceramic layer 2. As a result, the thermal shock resistance of the monolithic ceramic capacitor 1 deteriorates, and thermal shock due to solder when mounting on the circuit board causes cracks in the capacitor body 2, and dielectric loss and insulation resistance of the capacitor 1 occur. There is a problem that the electrical characteristics such as markedly deteriorate and the reliability during use decreases.

The present invention has been completed as a result of intensive research conducted by the present inventors in view of the above circumstances. The purpose of the present invention is to prevent the plating bath solution from entering the inside of the capacitor body due to the formation of a metal plating film. Therefore, it is to provide a highly reliable multilayer ceramic capacitor which has improved thermal shock resistance and prevented deterioration of electrical characteristics.

Another object of the present invention is to prevent the penetration of the plating bath solution into the inside of the capacitor body, so that even if a metal plating film is formed on the external electrodes or soldering is performed on the circuit board, the characteristics and reliability can be improved. It is an object of the present invention to provide a monolithic ceramic capacitor which is excellent in thermal shock resistance and does not deteriorate in properties.

[0009]

A monolithic ceramic capacitor according to the present invention comprises a capacitor body formed by alternately laminating dielectric ceramic layers and internal electrodes, and a capacitor body formed on an end face of the capacitor body. In a multilayer ceramic capacitor provided with an external electrode electrically connected to the electrode, the end faces of the internal electrode and the dielectric ceramic layer are bent in the stacking direction.

[0010]

In the multilayer ceramic capacitor of the present invention, the end faces of the internal electrodes and the dielectric porcelain layer, which are laminated in a plurality of layers, are bent in the stacking direction near the end faces of the capacitor body. It is possible to prevent the plating bath liquid from entering the inside of the capacitor body such as the inside of the internal electrode or the interface between the internal electrode and the dielectric porcelain layer when forming the solder or mounting the solder on the circuit board. This is because by bending the internal electrode and the dielectric ceramic layer in such a manner, the thickness of the internal electrode on the end surface of the capacitor body becomes thin, and the internal electrode and the dielectric ceramic layer are sufficiently adhered to each other, and the dielectric It is considered that this is because the gap between the body porcelain layer and the internal electrode disappears, so that the cavity into which the plating solution penetrates becomes small.

Therefore, according to the monolithic ceramic capacitor of the present invention, it is possible to prevent the occurrence of cracks in the capacitor body due to the penetration of the plating solution, or the deterioration of the electrical characteristics such as the dielectric loss and the insulation resistance of the capacitor, It is possible to provide a highly reliable multilayer ceramic capacitor having excellent thermal shock resistance.

In the laminated ceramic capacitor of the present invention, various methods can be used to bend the end faces of the internal electrodes and the dielectric ceramic layers in the laminating direction. For example, by laminating a desired number of layers of a ceramic green sheet on which an internal electrode pattern is printed and pressure bonding, and by appropriately selecting the cutting method and conditions when cutting the green chip to produce a green chip, In the green chip, both end surfaces of the internal electrode pattern and the ceramic green sheet can be bent uniformly in the stacking direction.
Then, by firing it, it is possible to obtain a capacitor body in which the end faces of the internal electrode and the dielectric ceramic layer are bent in the stacking direction in the vicinity of the cut end face. Therefore, since the monolithic ceramic capacitor of the present invention can be easily produced in such a manner, a highly reliable monolithic ceramic capacitor excellent in thermal shock resistance can be manufactured at low cost without increasing the manufacturing process and the manufacturing cost. Can be provided.

[0013]

EXAMPLES The multilayer ceramic capacitor of the present invention will be described in detail below based on examples. The present invention is not limited to the following embodiments, and various modifications and improvements may be added without departing from the gist of the present invention.

FIG. 1 is a sectional view showing an example of the structure of the monolithic ceramic capacitor of the present invention. In the monolithic ceramic capacitor 7 of FIG. 1, reference numeral 8 is a capacitor body, in which dielectric ceramic layers 9 and internal electrodes 10a and 10b are alternately laminated. 11a and 11b are external electrodes, and 12a and 12b are metal plating films formed on the external electrodes.
11b is an internal electrode 10 on both end faces of the capacitor body 8.
It is electrically connected to the ends of a and 10b, respectively. As shown by the range A in the figure, in the monolithic ceramic capacitor 7 of the present invention, the end faces of the internal electrodes 10a and 10b and the dielectric ceramic layer 9 are in the laminating direction near the end face A of the capacitor body 8, that is, Is formed by being bent uniformly downward.

In the laminated ceramic capacitor 7 of the present invention, when the respective end faces of the internal electrodes 10a and 10b and the dielectric porcelain layer 9 are bent in the stacking direction in the vicinity of the end face of the capacitor body 8, both end faces are bent as shown in FIG. May be bent in the same direction, or both end surfaces may be bent in opposite directions. Further, the shape of the bent portion may be curved so that the cross section has a curved shape, and the curvature of the bent portion may be constant or may be changed. Further, the shape may be one-stepped or multi-stepped, or a combination thereof.

The lengths of the bent portions of the internal electrodes 10a and 10b and the dielectric porcelain layer 9 shown by A in FIG. 1 are appropriately set according to the dimensions and characteristics of the laminated ceramic capacitor to be manufactured, but are set to 30 to 100. The length is preferably μm, which can remarkably enhance the action and effect of the present invention.

As a method of bending the end faces of the internal electrodes 10a and 10b and the dielectric ceramic layer 9 in the stacking direction in the vicinity of the end face of the capacitor body 8, various methods can be used as described above. According to the cutting method and conditions for cutting into chips, it is preferable in that it can be performed relatively easily and at low cost.

For example, in order to obtain the capacitor body 8 in which the end faces of the internal electrodes 10a and 10b and the dielectric porcelain layer 9 are bent by cutting, a dry cutting method using a dicing blade heated to about 50 to 100 ° C. is used. is there. According to this, since the cut surface can be softened by the heat of the dicing blade and the frictional heat, the end surfaces of the internal electrodes 10a and 10b and the dielectric ceramic layer 9 can be uniformly bent in the stacking direction, and the length of the bent portion can be increased. Also, it can be set in a desired range by adjusting the heat of the dicing blade.

Various dielectric materials can be used for the dielectric ceramic layer 9 of the monolithic ceramic capacitor 7 of the present invention. For example, BaTiO ₃ .LaTiO ₃ .CaTiO _{3
· NdTiO 3 · MgTiO 3 · SrTiO} 3 · CaZ
rO ₃ · SrSnO ₃ · BaTiO ₃ with Nb ₂ O ₅ · T
a composition containing a ₂ O ₅ , ZnO, CoO or the like, or Ba
A barium titanate-based material such as a solid solution in which Ba, which is a constituent atom of TiO ₃ , is partially replaced by Ca, and Ti is partially replaced by Zr or Sn, Pb (Mg _1/3 Nb _2/3 ) O ₃ .Pb (Fe, N
d, Nb) O ₃ based perovskite structure compound, Pb
_{(Mg 1/3 Nb 2/3) O 3} -PbTiO 2 -component composition such as _{3, Pb (Mg 1/3 Nb 2/3} ) O 3 -PbTiO 3
-Pb (Mg _1/2 W _1/2 ) O ₃ · Pb (Mg _1/3 Nb
_{2/3) O 3 -Pb (Zn 1/3} Nb 2/3) O 3 -PbTi
O ₃ · Pb (Mg _1/3 Nb _2/3 ) O ₃ -Pb (Zn _1/3
3 such as Nb _2/3 ) O ₃ -Pb (Sm _1/2 Nb _1/2 ) O 3
Component composition, or MnO · MnO ₂ · C in their
Lead-based relaxor materials such as those to which uO / BaTiO _{3 and the} like are added can be used. When the capacitor body 8 is formed, a ceramic green sheet formed from slips in which these dielectric powders are sufficiently mixed with an organic binder is used.

Examples of materials for forming the internal electrodes 10a and 10b include Pd, Ag, Pt, Ni, Cu, Pb and alloys thereof. In forming the internal electrodes 10a and 10b, a conductive paste is used which is prepared by mixing and pulverizing such electrode material powder with a binder.
The conductive paste is printed as an internal electrode pattern on a ceramic green sheet by a screen printing method or the like, laminated, pressure-bonded, fired and sintered to form desired internal electrodes 10a, 10b.

The material for forming the external electrodes 11a and 11b is almost the same as that of the internal electrodes 10a and 10b. If necessary, glass frit or the like is added to apply and bake on the end face of the capacitor body 8 as a conductive paste. As a result, desired external electrodes 11a and 11b are formed. Alternatively, a conductor film may be formed by a thin film forming method such as sputtering.
The external electrodes 11a and 11b may be formed not only on the end faces of the capacitor body 8 but also on the side faces as necessary.

The material of the metal plating films 12a and 12b formed on the external electrodes 11a and 11b is Ni.Ni-Sn.A.
u, etc., and is formed by a plating method such as electrolytic plating or electroless plating.

When the monolithic ceramic capacitor 7 is mounted on the circuit board by soldering, a reflow method or a flow soldering method is used.

Specific examples of the chip type multilayer ceramic capacitor of the present invention will be shown below. [Example 1] First, as a material for the dielectric porcelain layer, a material powder having X7R characteristics containing barium titanate as a main component was prepared, mixed with an organic binder, and the obtained slip was used to obtain a thickness of 15 μm by a doctor blade method. The ceramic green sheet of was molded.

An internal electrode pattern was printed on this ceramic green sheet by a screen printing method using a conductive paste prepared by adding an organic binder to Pd or Ag-Pd powder and mixing them.

Then, 90 layers were laminated so that the printed internal electrode patterns were alternately formed into a comb structure, and thermocompression bonding was performed at 100 ° C. to obtain a laminated body 13 having a structure shown in the sectional view of FIG.
As shown in FIG. 3, in the laminated body 13, the ceramic green sheets 14 and the internal electrode patterns 15 are alternately laminated so as to have a comb structure. Here, the alternate long and short dash line in the figure indicates the position where the laminated body 13 is cut to obtain a green chip.

Next, the laminated body 13 was dry-cut using a dicing blade heated to about 50 to 100 ° C. under the conditions of a rotation speed of 10,000 rotations / minute and a speed of 10 cm / second to produce a green chip.

Then, after removing the binder from the green chip, it was fired at 1,300 ° C. for 2 hours to be chamfered to prepare a sample A of the embodiment of the present invention.

As a comparative example, a green chip was produced by cutting the laminate 13 as follows. One is the above dicing blade, the number of rotation is 10,000 without heating the blade.
Wet cutting was performed under the conditions of rotation / minute and speed of 10 cm / second. The other was cut by pressing with a 100 μm thick leather blade. In the same manner, binder removal processing, firing, and chamfering processing were performed to prepare samples B (wet dicing blade cutting) and C (leather blade push cutting) of comparative examples.

The shapes of the internal electrodes and the dielectric porcelain layers of Samples A, B and C were observed by a metallographic microscope after cross section processing. As shown in FIG. 1, it was uniformly bent in the stacking direction near the end face, and the length of the bent portion was 50 μm. On the other hand, the end faces of the internal electrodes and the dielectric porcelain layers of Samples B and C each had a linear flat shape up to the end face as shown in FIG.

[Example 2] Next, sample A prepared in [Example 1]
For B and C, external electrodes were formed as follows, and the thermal shock resistance to the plating bath was evaluated and compared.

First, a conductive paste prepared by adding an organic binder to Ag powder was mixed and applied to the end faces of the internal electrodes of Samples A, B, and C, which were baked at 700 ° C. to form external electrodes with a thickness of 100 μm. Formed.

Then, Ni plating was continuously applied in a Watt bath and then Sn plating was applied in a sulfuric acid bath.

Then, 200 samples of each plated sample were placed in a solder bath of 300 ° C., 360 ° C. and 400 ° C. for 3 seconds and subjected to thermal shock. After that, the sample taken out
The number of samples in which cracks were generated by thermal shock was examined by observing with a 40 × binocular microscope and compared.

Further, the insulation resistance of each sample was measured, and the number of samples having a resistance value of 1 × 10 ⁴ MΩ or less and causing insulation failure was examined and compared.

Table 1 shows the evaluation results of these thermal shock resistances.

[0037]

[Table 1]

As can be seen from the results in Table 1, in sample A of the present invention, no cracks were found at 300 ° C and 360 ° C, and only one was found at 400 ° C. . On the other hand, in Samples B and C, considerable cracking was observed.

Insulation failure did not occur in Sample A of the present invention, whereas in Samples B and C, insulation failure occurred at 360 ° C. or higher.

From these results, the sample A of the present invention is the conventional multilayer ceramic capacitor sample B in which the internal electrodes and the dielectric ceramic layer are formed flat to the end surface of the capacitor body.
-It was confirmed from C that the thermal shock resistance was superior.

[Example 3] Next, with respect to the samples A, B and C produced in [Example 1], without forming an external electrode, [Example 2]
The thermal shock resistance to the plating bath was evaluated and compared in the same manner as in.

Then, in the same manner as in [Example 2], 200 pieces of each plated sample were placed at 300 ° C and 360 ° C.
It was placed in a solder bath at 400 ° C for 3 seconds and subjected to thermal shock. After that, the taken-out samples were observed with a 40 × binocular microscope, and the number of samples in which cracks due to thermal shock were generated was examined and compared.

Table 2 shows the evaluation results of this thermal shock resistance.

[0044]

[Table 2]

As can be seen from the results in Table 2, in sample A of the present invention, no cracks were found at 300 ° C and 360 ° C, and only three were found at 400 ° C. . On the other hand, in Samples B and C, 4 to 5 cracks were observed at 300 ° C., around 50 cracks at 360 ° C., and near 100 cracks at 400 ° C.

Based on these results, the sample A of the present invention is also obtained.
It has been confirmed that the thermal shock resistance is superior to the conventional multilayer ceramic capacitor samples B and C in which the internal electrodes and the dielectric ceramic layer are formed flat to the end face of the capacitor body.

[Example 4] Next, samples A and B and C respectively
Using 2,000 pieces, solder mounting was performed on the board by flow soldering at 340 ° C. These were put into a wet tank in a temperature / humidity environment of 90 ° C. and 65% RH, and a pulse voltage application test under the condition of 1 V / 1 second was performed for 96 hours. Then, the insulation resistance of each sample after the test was measured, and the resistance value was 1 × 10 ⁴
The number of samples having MΩ or less and causing insulation failure was examined and compared.

Table 3 shows the evaluation results.

[0049]

[Table 3]

As can be seen from the results in Table 3, no defective insulation was found in the sample A of the present invention, whereas 10 defective samples were found in the sample B and 15 defective samples were found in the sample C. Was given.

Based on these results, the sample A of the present invention is also obtained.
It has been confirmed that, as compared with the conventional multilayer ceramic capacitor samples B and C in which the internal electrodes and the dielectric porcelain layer are formed flat to the end face of the capacitor body, have excellent thermal shock resistance and high reliability.

As described above, according to the monolithic ceramic capacitor of the present invention, the end faces of the internal electrode and the dielectric ceramic layer are bent in the stacking direction in the vicinity of the end face of the capacitor body, respectively. Since it is possible to prevent the plating bath liquid from entering the capacitor body at the interface between the capacitor and the dielectric ceramic layer, etc., it is possible to provide a highly reliable multilayer ceramic capacitor that has excellent thermal shock resistance and does not deteriorate electrical characteristics. I was able to.

Further, since the monolithic ceramic capacitor of the present invention can be easily manufactured by selecting the method and conditions for cutting the laminated body into green chips as described above, for example, compared with the conventional monolithic ceramic capacitor. However, the manufacturing man-hours and manufacturing costs do not increase. Therefore, a highly reliable monolithic ceramic capacitor having excellent thermal shock resistance can be provided at low cost.

[0054]

As described in detail above, according to the monolithic ceramic capacitor of the present invention, since the end faces of the internal electrode and the dielectric ceramic layer are bent in the laminating direction, the metal plating on the external electrode is performed. It has been possible to provide a highly reliable multilayer ceramic capacitor which prevents the plating bath solution from entering the inside of the capacitor body at the time of forming a film, enhances thermal shock resistance, and prevents deterioration of electrical characteristics.

According to the monolithic ceramic capacitor of the present invention, the end surfaces of the internal electrode and the dielectric porcelain layer are bent in the laminating direction to prevent the plating bath solution from entering the inside of the capacitor body. It has been possible to provide a monolithic ceramic capacitor having excellent thermal shock resistance, in which characteristics and reliability are not deteriorated not only by forming a metal plating film on the substrate but also by solder mounting on a circuit board.

Further, the monolithic ceramic capacitor of the present invention can be easily manufactured, and the number of manufacturing steps and the manufacturing cost are not increased as compared with the conventional monolithic ceramic capacitor. Therefore, the thermal shock resistance is excellent and the reliability is high. A monolithic ceramic capacitor with low cost can be provided at low cost.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a monolithic ceramic capacitor of the present invention.

FIG. 2 is a sectional view showing the structure of a conventional monolithic ceramic capacitor.

FIG. 3 is a cross-sectional view showing a structure and a cutting position of a laminated body in an example of the laminated ceramic capacitor of the present invention.

[Explanation of symbols]

1, 7 ..... multilayer ceramic capacitors 2, 8 ..... capacitor body 3, 9 ..... dielectric ceramics Layers 4a, 4b, 10a, 10b ... Internal electrodes 5a, 5b, 11a, 11b ... External electrodes 6a, 6b, 12a, 12b ... Metal plating film

Claims (1)

[Claims] 1. A capacitor main body formed by alternately laminating dielectric ceramic layers and internal electrodes, and an external electrode formed on an end surface of the capacitor main body and electrically connected to the internal electrode. A monolithic ceramic capacitor provided with the internal electrode and the dielectric ceramic layer, each end face of which is bent in the laminating direction.