JPH09266132A - Multilayer electronic part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer capacitor which can reduce generation of improper insulation caused by water penetration and also can suppress generation of such structural defect as crack at the time of soldering. SOLUTION: The multilayer capacitor 20 comprises an element body 23 and a pair of external electrodes 24. The element body 23 is made up of dielectric layers 21 and internal electrodes 22 alternately stacked and then burned. The pair of external electrodes 24 are connected in parallel to the internal electrodes 22 alternately at both ends of the element body 23. The body 23 is burned so as to have locally different sintered densities to provide multilayer capacitor 20. Therefore, in a part of the element body 23 having low sintered densities, fine air layers are dispersed between the dielectric layers so that, when a stress occurred, the air layers cause the stress to be reduced. In a part of the element body 23 having high sintered densities, no fine air layers are present between the dielectric layers so that the body part becomes compact, thereby preventing external water penetration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated electronic component such as a laminated capacitor, and more particularly to a small laminated electronic component.

[0002]

2. Description of the Related Art FIGS. 2 to 4 show a multilayer capacitor as an example of conventional multilayer electronic components. 2 is an exploded perspective view,
3 is a plan view and FIG. 4 is a sectional view taken along the line AA of FIG.

[0003] In the drawing, reference numeral 10 denotes a multilayer capacitor in which a dielectric body 13 formed by alternately laminating dielectric layers 11 and internal electrodes 12 and internal electrodes are alternately connected in parallel at both ends of the dielectric body 13. And a pair of external electrodes 14.

The internal electrode 12 is composed of an internal electrode piece 12a provided near the central region of the dielectric layer 11 and an internal electrode lead portion 12b provided along the external electrode 14 and connected to the external electrode 14. The internal electrode piece 12a is connected to the external electrode 14 via the internal electrode lead-out portion 12b.

[0005] The dielectric layer 11 is formed of a ceramic sintered body on a rectangular sheet, and the ceramic sintered body is formed of a dielectric ceramic material containing, for example, barium titanate as a main component. The internal electrode 12 is formed of a metal thin film obtained by sintering a metal paste. As the metal paste, for example, an electrode mainly containing a noble metal material such as Pd or Ag-Pd is used. The external electrode 14 is also formed of the same material as the internal electrode 12, and the surface is plated with solder to improve solder wettability.

[0006]

However, in the above-mentioned conventional multilayer capacitor, moisture in the air may permeate to cause insulation failure between the internal electrodes. In addition, structural defects such as cracks may occur at the external electrode forming positions at both ends of the element body 13 due to the stress of the solder when the solder is mounted on the circuit board.

In view of the above problems, an object of the present invention is to provide a laminated electronic component capable of reducing the occurrence of insulation failure due to the penetration of moisture and the occurrence of structural defects such as cracks during soldering. It is in.

[0008]

In order to achieve the above object, the present invention provides a substantially rectangular parallelepiped in which an insulating layer and an internal electrode layer are alternately laminated and the laminated body is sintered. A laminated electronic component comprising a shaped element body and external electrodes in which internal electrodes formed on the internal electrode layers are alternately connected in parallel at both ends of the element body, wherein the element body is partially formed. We propose multilayer electronic components with different degrees of sintering.

According to the laminated electronic component, since the degree of sintering of the element body is partially different, a fine air layer is scattered between the dielectrics in the portion where the degree of sintering is low, and stress is generated. In this case, stress is relaxed by the air layer, and in a portion where the degree of sintering is high, there is no air layer between the dielectrics and the state becomes tight, so that permeation of moisture from the outside is prevented.

According to a second aspect, in the laminated electronic component according to the first aspect, the degree of sintering of the outer peripheral portion of the element body is set to be higher than the degree of sintering of the element body at the peripheral portion of the internal electrode. We propose a multilayer electronic component.

According to the laminated electronic component, the sintering degree of the outer peripheral portion of the element body is set to be higher than the sintering degree of the element body of the peripheral portion of the internal electrode, and the air layer is formed between the dielectric bodies in the outer peripheral portion. Is absent and is in a tightened state, which prevents moisture from penetrating from the outside to the internal electrode formation site.

According to a third aspect of the present invention, in the laminated electronic component according to the first aspect, the degree of sintering of one surface of at least one pair of side surfaces excluding both ends of the element body has a degree of sintering of the other surface. We propose a multilayer electronic component that is set higher than the degree of bonding.

According to the laminated electronic component, the degree of sintering is low on the one surface, and minute air layers are scattered between the dielectrics, and when stress occurs, the stress is relaxed by the air layer, On the other surface, the degree of sintering is high and there is no air layer between the dielectrics, and the surface is in a tightened state, which prevents the permeation of moisture from the outside.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an external perspective sectional view showing a multilayer capacitor according to a first embodiment of the present invention. In the figure, reference numeral 20 denotes a multilayer capacitor, which includes an element body 23 in which dielectric layers 21 and internal electrodes 22 are alternately laminated, and a pair of internal electrodes 22 alternately connected in parallel at both ends of the element body 23. And the external electrode 24.

The dielectric layer 21 is made of a rectangular sheet-shaped ceramic sintered body, and the sintered body is made of a dielectric ceramic material formed by firing a green sheet containing barium titanate as a main component, for example.

Each of the pair of internal electrodes 22 adjacent to each other with the dielectric layer 21 in between has a rectangular shape.
The long side of is substantially perpendicular to the external electrode 24. The width of each internal electrode 22 is formed to be equal.

On the other hand, the degree of firing near the upper surface 23a of the element body 23 is set higher than the degree of firing near the lower surface 23b. In the vicinity 23a of the upper surface, the dielectric body is sintered in a tight state, and near the lower surface 23b, the dielectric is formed. Fine air layers (air bubbles) 31 are scattered between the bodies. In addition, the peripheral portion 23c of the internal electrode 22 has a high degree of sintering because the internal electrode 22 is heated to a temperature higher than that of the surroundings during firing, and the dielectric is in a tight state.

The above-mentioned internal electrode 22 is made of a metal thin film obtained by sintering a thin film of a conductive paste, and as the conductive paste, for example, one containing palladium powder as a main component is used. The external electrode 24 is also made of the same material as the internal electrode 22, and the surface thereof is plated with solder to improve solder wettability.

This multilayer capacitor was manufactured as follows. First, an organic binder was added to the dielectric raw material powder.
% By weight, and further 50% by weight of water, and these were put into a ball mill and mixed well to prepare a slurry of a dielectric ceramic raw material.

Next, after putting this slurry in a vacuum defoamer to defoam it, put it in a reverse roll coater to form a thin film of this slurry on a polyester film,
This thin film is dried by heating to 100 ° C. on a polyester film, punched out, and 10 cm square, about 2 mm thick.
A green sheet of 0 μm was obtained.

On the other hand, 10 g of palladium powder having an average particle size of 1.5 μm and 0.9 g of ethyl cellulose dissolved in 9.1 g of butyl carbitol were placed in a stirrer.
By stirring for 10 hours, a conductive paste for an internal electrode was obtained.

After that, the above-mentioned internal electrode pattern is applied to 5
Using each of the screens having zero, a pattern of the internal electrode made of the conductive paste was printed on one surface of the green sheet, and dried.

Next, a plurality of green sheets were laminated with the printed surface facing upward, and further, unprinted green sheets were laminated on the upper and lower surfaces of this laminate. Then
This laminate was pressed at a temperature of about 50 ° C. by applying a pressure of about 40 tons in the thickness direction. Thereafter, the laminate was cut into a lattice to obtain about 50 laminated chips.

Next, this laminated chip is placed in a furnace capable of firing in an atmosphere and heated to 600 ° C. in the atmosphere to burn the organic binder, and thereafter, the atmosphere of the furnace is set in the atmosphere to heat the laminated chip. The temperature was maintained at 600 ° C. to 1150 ° C. (maximum temperature), which is the firing temperature, for 3 hours. After this, 1
The temperature was lowered to 600 ° C. at a rate of 00 ° C./hr and cooled to room temperature to obtain a sintered body chip.

During this firing, the laminated chips are placed on a setter and fired in a firing furnace. However, the setters may be fired by stacking a plurality of stages, and the element body is partially fired depending on the placement position of the laminated chips. It is possible to adjust the degree of connection.

Next, a conductive paste composed of silver, glass frit and vehicle is applied to the end surface of the sintered body chip where the internal electrodes are exposed and dried, and this is dried in the air at 800 ° C.
Baking at a temperature of 15 minutes to form a silver electrode layer, further depositing copper thereon by electroless plating, and providing a Pb-Sn solder layer thereon by electroplating to form a pair of external electrodes did. As a result, a multilayer capacitor having element bodies having partially different degrees of sintering was obtained as described above.

According to the above-mentioned multilayer capacitor, since the peripheral portion of the internal electrode 22 is in a state where the dielectric is tightened, the permeation of moisture from the outside is prevented and the occurrence of insulation failure between the internal electrodes is prevented. can do. Further, when soldering to the circuit board, as shown in FIG. 5, when the element body 23 is placed on the circuit board 32 with the upper surface thereof facing upward, the vicinity of the upper surface 23a is in a state in which the dielectric is tightened. Therefore, even if the tension P of the solder 33 is applied to the vicinity 23a of the upper surface, the generation of cracks is prevented. Further, as shown in FIG. 6, when the element body 23 is placed on the substrate 32 with the lower surface thereof facing upward, fine bubbles 31 are formed between the dielectrics near the lower surface 23b.
Therefore, even if the tension P of the solder 33 is applied to the lower surface neighborhood 23b, the stress caused by the tension P is
It is relaxed by 1 and can be kept to a minimum crack even if a crack occurs.

Next, a second embodiment of the present invention will be described. FIG. 7 is a perspective sectional view showing the multilayer capacitor of the second embodiment. In the figure, the same components as those of the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted. The difference between the first embodiment and the second embodiment is that the degree of sintering of the outer peripheral portion 23d is set higher than that of the central portion of the element body 23 (including the peripheral edge portion 23c of the internal electrode). is there.

As a result, in comparison with the first embodiment, it is possible to further prevent the permeation of moisture from the outside, have sufficient strength to withstand the stress during soldering, and to prevent structural defects such as cracks. Occurrence can be prevented.

These embodiments are merely examples, and the present invention is not limited to these.

[0031]

As described above, according to the laminated electronic component according to the first aspect of the present invention, since the sintering degree of the element bodies is partially different, the dielectric body is formed in the portion where the sintering degree is low. Fine air layers are scattered between them, and when stress is generated, the air layers relieve the stress, and in the portion where the degree of sintering is high, there is no air layer between the dielectrics and the state becomes tight. Since the permeation of water is prevented, the relaxation of the stress reduces the occurrence of structural defects such as cracks, and the prevention of the permeation of water can prevent the occurrence of insulation failure between the internal electrodes.

According to the laminated electronic component of the second aspect, in addition to the above effects, the degree of sintering of the outer peripheral portion of the element body is set higher than the degree of sintering of the element body at the peripheral portion of the internal electrode. In the outer peripheral part, there is no air layer between the dielectrics, and it is in a tight state, and moisture permeation from the outside to the internal electrode formation site is blocked, so that high strength is achieved over the entire element body and cracks etc. It is possible to prevent the occurrence of structural defects and prevent the penetration of moisture, and thus prevent the occurrence of insulation failure between the internal electrodes.

Further, according to the laminated electronic component of the third aspect, in addition to the above effect, at least one set of facing surfaces of the side surface excluding both ends of the element body has a sintering degree of the other surface. Since the degree of sintering is set higher than that of the surface, the degree of sintering is low on the one surface, and minute air layers are scattered between the dielectrics. It is relaxed, the degree of sintering is high on the other surface, and there is no air layer between the dielectrics, resulting in a tight state.
Since the penetration of moisture from the outside is prevented, the occurrence of structural defects such as cracks is reduced by the relaxation of the stress, and the insulation failure between the internal electrodes can be prevented by preventing the penetration of moisture. .

[Brief description of drawings]

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

FIG. 2 is an exploded perspective view showing a conventional multilayer capacitor.

FIG. 3 is a cross-sectional plan view showing a conventional multilayer capacitor.

FIG. 4 is a sectional view taken along line AA of FIG. 3;

FIG. 5 is a diagram for explaining operation effects of the first embodiment of the present invention.

FIG. 6 is a diagram for explaining the function and effect of the first embodiment of the present invention.

FIG. 7 is a perspective sectional view showing a multilayer capacitor according to a second embodiment of the present invention.

[Explanation of symbols]

20 ... Multilayer capacitor, 21 ... Dielectric layer, 22 ... Internal electrode, 23 ... Element body, 24 ... External electrode, 31 ... Bubble, 32 ...
Circuit board, 33 ... Solder.

Claims (3)

[Claims] 1. A substantially rectangular parallelepiped element body obtained by alternately laminating an insulator layer and an internal electrode layer and sintering the laminated body, and formed on the internal electrode layer at both ends of the element body. A laminated electronic component comprising external electrodes in which internal electrodes are alternately connected in parallel, wherein the element bodies have partially different degrees of sintering. 2. The laminated electronic component according to claim 1, wherein the degree of sintering of the outer peripheral portion of the element body is set to be higher than the degree of sintering of the element body of the peripheral edge portion of the internal electrode. 3. The sintering degree of one surface is set to be higher than the sintering degree of the other surface of at least one set of opposing surfaces of the side surfaces excluding both ends of the element body. Item 1. The laminated electronic component according to item 1.