JPH09120930A - Multilayered ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a capacitor element from being exposed, increase of failures such as tan δ and capacitance and decrease of insulation resistance. SOLUTION: A multilayered ceramic capacitor 9 is provided with a ceramic sheet 1, a dielectric sheet 4 provided with an inner electrode 2 overlapped with the ceramic sheet 1 and an electrode for terminals made of two or more layers at an end 6. The capacitor 9 is also provided with a primary electrode 5 for terminals provided on the surface of the end 6 and made of carbon whose particle size is smaller than the thickness of the electrode 2 and a secondary electrode 7 provided on the surface of the primary electrode 5 and made of copper powder or copper alloy powder whose particle diameter is larger than 5μm and organic adhesive.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a monolithic ceramic capacitor.

[0002]

2. Description of the Related Art A conventional monolithic ceramic capacitor 10
Usually has a configuration as shown in FIG. That is, a plurality of dielectric sheets 13 each having an internal electrode 12 having a thickness of 3 to 5 μm are laminated by applying a paste ink made of a silver-palladium alloy and an organic binder on the surface of the ceramic green sheet 11. The end portion 1 of the capacitor element 14 formed by laminating the dielectric sheets 13
5 is provided with a terminal electrode 16 made of a silver-palladium alloy and glass.

Another conventional example is a monolithic ceramic capacitor 17 having a structure as shown in FIG. In FIG. 3, the same parts as those in FIG. 2 are designated by the same reference numerals. In this conventional example, the terminal electrode has a two-layer structure. That is, the end portion 15 of the capacitor element 14
A first terminal electrode 18 made of a spherical powder of copper or a copper alloy having an average particle diameter of about 10 μm and an organic adhesive is provided in contact with the surface of the electrode. A second terminal electrode 19 plated with molten solder is provided on the surface of the first terminal electrode 18.

Further, as another conventional example, as shown in FIG. 4, there is also a monolithic ceramic capacitor 20 having a three-layer structure of terminal electrodes. In FIG. 4, the same components as those in FIG. 2 are designated by the same reference numerals. The monolithic ceramic capacitor 20 is provided with a first terminal electrode 21 made of a silver-palladium alloy and glass in direct contact with the surface of the end portion 15 of the capacitor element 14. The first terminal electrode 21
The surface of the is plated with nickel to provide the second terminal electrode 22. The surface of the second terminal electrode 22 is solder plated to provide a third terminal electrode 23.

[0005]

However, in the monolithic ceramic capacitor 10 shown in FIG. 2, the terminal electrode 16 is melted in the molten solder when it is mounted on a printed circuit board or the like by soldering, and the capacitor element 14 is There is a drawback that the end portion 15 is exposed.

The monolithic ceramic capacitor 1 shown in FIG.
In No. 7, since the organic adhesive is used to form the first terminal electrode 18, the baking temperature must be 200 ° C. or lower. Therefore, unlike the case where the terminal electrode is formed of glass or the like and baked at a temperature of 800 ° C., the internal electrode 12 and the first terminal electrode 18 are mutually diffused to completely form an alloy. Never be connected. Further, the average particle diameter of the thin layered internal electrode having a thickness of 3 to 5 μm and the first terminal electrode 18 is 10
It is in point contact with spherical copper or copper alloy having a large μm. Therefore, as the number of layers of the internal electrode 12 is smaller and the capacity is smaller, tan δ and capacity defect are more likely to increase.

Further, in the monolithic ceramic capacitor 20 of FIG. 4, the plating solution used for forming the second terminal electrode 22 remains, which lowers the insulation resistance during use and cannot be used for high withstand voltage products. There are drawbacks.

An object of the present invention is to provide a monolithic ceramic capacitor which can improve the above-mentioned drawbacks and prevent exposure of the capacitor element, increase of each defect of tan δ and capacitance, decrease of insulation resistance and the like and which can be used at high voltage. Is.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is directed to a terminal having two or more layers at the end thereof which are laminated with dielectric sheets having internal electrodes provided on the surface of a ceramic sheet. In a monolithic ceramic capacitor provided with electrodes, a first terminal electrode made of carbon and an organic adhesive having a grain size equal to or less than the thickness of the internal electrode provided on the end surface, and the first terminal electrode The particle size provided on the surface of the
The present invention provides a multilayer ceramic capacitor having the above-mentioned copper powder or copper alloy powder and a second terminal electrode made of an organic adhesive.

If necessary, a third terminal electrode made of solder or the like is provided on the surface of the second terminal electrode.

[0011]

According to the present invention, the first terminal electrode containing carbon having a grain size equal to or smaller than the thickness of the internal electrode is provided on the surface of the end of the capacitor element formed by stacking the dielectric sheets. Therefore, carbon contacts the internal electrodes in a large area. Therefore, it is possible to prevent an increase in each tan δ or capacity defect due to contact failure. And carbon is cheaper than copper and the like, and the manufacturing cost can be reduced.

Further, since the second terminal electrode containing copper powder or the like is provided on the surface of the first terminal electrode, the monolithic ceramic capacitor is mounted on the printed circuit board or the like at the location of the second terminal electrode. Even if soldering is performed or a third terminal electrode made of solder is formed on the surface of the second terminal electrode,
It is possible to prevent such a defect that the end of the capacitor element is exposed by being electrolyzed from the terminal electrode. Further, since no plating solution is used, it is possible to prevent a defect that the insulation resistance is lowered.

If the particle size of the copper powder or copper alloy powder is smaller than 5 μm, it becomes difficult for the solder to adhere to the surface. In the present invention, the particle size of the copper powder or the like contained in the second terminal electrode is set to 5
Since the thickness is at least μm, the solder is likely to adhere to the surface of the second terminal electrode. Therefore, the monolithic ceramic capacitor can be easily soldered to a printed circuit board or the like. Further, it is easy to form solder on the surface of the second terminal electrode.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 is a green sheet made of a barium titanate-based ferroelectric ceramic and having a thickness of 30 μm. Reference numeral 2 denotes an internal electrode having a thickness of 1 to 3 μm, which is formed on the surface of the green sheet 1 from one end to the front of the other end and is made of a paste-like ink in which an organic binder is added to silver palladium. Reference numeral 3 is a capacitor element in which the green sheets 1 and the dielectric sheets 4 provided with the internal electrodes 2 are superposed by the number of sheets required to obtain the required capacitance. 5
Is a first terminal electrode formed on the surface of the end portion 6 of the capacitor element 3 and made of carbon having an average particle diameter of 3 μm or less and an organic adhesive. Reference numeral 7 is a second terminal electrode formed on the surface of the first terminal electrode 5 and comprising a copper alloy powder having an average particle diameter of 10 μm and silver coated on copper powder, and a phenol resin adhesive. is there. Reference numeral 8 denotes a third terminal electrode made of solder and provided on the surface of the second terminal electrode 7.

Further, the manufacturing method of the above embodiment will be described. First, a barium titanate-based ferroelectric ceramic powder and an organic binder are kneaded and made into a slurry to form a ceramic green sheet 1 by a doctor blade method or the like. Next, a paste-like ink obtained by adding an organic binder to silver-palladium is applied to the surface of the green sheet 1 by screen printing or the like, and dried to form the internal electrode 2. After forming the internal electrodes 2, a predetermined number of the dielectric sheets 3 having the internal electrodes 2 formed thereon are superposed on the green sheet 1 and thermocompression bonded. After thermocompression bonding, it is cut into a predetermined size, the binder is removed, and firing is performed to form the capacitor element 3. After the capacitor element 4 is formed, the end portion 6 of the capacitor element 3 is coated with a substance consisting of carbon and an organic adhesive and baked at a temperature of 200 ° C. to form the first terminal electrode 5. After the first terminal electrode 5 is formed, a substance consisting of copper alloy powder and a phenol resin adhesive is applied to the surface and baked at a temperature of 200 ° C. to form the second terminal electrode 7. After the second terminal electrode 7 is formed, hot solder plating is performed on the surface to form the third terminal electrode 8.
The monolithic ceramic capacitor 9 is manufactured.

The third terminal electrode 8 may be omitted.

Next, the rated voltage 63 of the above embodiment and the conventional example
Regarding the 0VDC multilayer ceramic capacitor, the tan δ defect rate generated when various capacitances were manufactured was measured, and the results are shown in Table 1. The conventional monolithic ceramic capacitor has the structure shown in FIG. 10 samples each
The number is set to 0,000.

[0018]

[Table 1]

As is clear from Table 1, when the same capacities are compared, in Examples 1 to 6, the tan δ defect rate was reduced to 1/5000 or less than in Conventional Examples 1 to 6. There is.

[0020]

As described above, according to the present invention, the first terminal electrode provided in contact with the surface of the end portion of the capacitor element is organically bonded to carbon whose grain size is less than the thickness of the internal electrode. In addition to being formed of a material composed of an agent, a second terminal electrode composed of an organic adhesive and copper powder having a particle size of 5 μm or more is provided on the surface of the first terminal electrode.
When soldering, the end of the capacitor element is not exposed, each defect of tan δ and capacitance can be reduced, the defect of lowering insulation resistance can be prevented, it can be used at high voltage, and it can be easily soldered to a printed circuit board etc. A solder layer can be easily formed on the surface of the second terminal electrode, and a relatively inexpensive multilayer ceramic capacitor can be obtained.

[Brief description of the drawings]

FIG. 1 shows a sectional view of an embodiment of the present invention.

FIG. 2 shows a cross-sectional view of a conventional monolithic ceramic capacitor.

FIG. 3 shows a cross-sectional view of a conventional monolithic ceramic capacitor.

FIG. 4 shows a sectional view of a conventional monolithic ceramic capacitor.

[Explanation of symbols]

1 ... Ceramic green sheet, 2 ... Internal electrodes,
3 ... Capacitor element, 4 ... Dielectric sheet, 5 ... First terminal electrode, 6 ... End portion, 7 ... Second terminal electrode,
8 ... Third terminal electrode, 9 ... Multilayer ceramic capacitor.

Claims (1)

[Claims] 1. A monolithic ceramic capacitor in which a dielectric sheet having an internal electrode provided on a surface of a ceramic sheet is laminated and a terminal electrode having two or more layers is provided at an end of the ceramic sheet. A first terminal electrode made of carbon and an organic adhesive, the diameter of which is equal to or less than the thickness of the internal electrode;
A monolithic ceramic capacitor, comprising: a second terminal electrode made of an organic adhesive and copper powder or copper alloy powder having a particle size of 5 μm or more provided on the surface of the first terminal electrode.