JP2003217969A - Manufacturing method of laminated ceramic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a laminated ceramics capacitor for forming an external electrode terminal, wherein remaining stress due to contraction of a Cu paste is reduced, without degrading adhesion to a dielectric ceramics in a sintering process, while not allowing voltage-resistance and insulation property to degrade and no inter-layer peeling occurs in a plating process. <P>SOLUTION: An internal electrode 2 comprising Ni is laminated alternately on a dielectric ceramics 1, whose main component is BaTiO<SB>3</SB>. At both ends of a chip, a first Cu external electrode 3 is formed for electrical connection with the internal electrode. A second Ag external electrode 4 is baked on the first Cu external electrode 3, over which a plating layer 5 is formed, to obtain a laminated ceramic capacitor 10. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a monolithic ceramic capacitor using a base metal for internal electrodes,
In particular, it relates to a method of forming an external electrode.

[0002]

2. Description of the Related Art A conventional monolithic ceramic capacitor is manufactured as follows. First, a dielectric ceramic powder containing barium titanate as a main component and a binder such as a resin are dispersed and mixed in an organic solvent, and a slurry is formed into a film having a certain thickness by a doctor blade method or the like to produce a green sheet. To do. Next, copper (C
u), an internal electrode paste made of a low resistance metal such as nickel (Ni) and an organic vehicle is printed on the green sheet to form internal electrodes.

Further, this green sheet, which is an electrode in which the internal electrodes are alternately opposed to each other, is punched out and laminated in a mold,
A laminated body is obtained by pressure bonding with a hot press or the like. This laminated body is cut into individual capacitor elements, debindered and fired to obtain laminated ceramic capacitor elements. External electrode terminals are formed on both end faces of the thus obtained multilayer ceramic capacitor element, where the electrode lead-out portions of the opposing internal electrodes are exposed, and the multilayer ceramic capacitor is completed.

Conventionally, Pd or Ag-Pd is used as the internal electrode.
Ag is used for the external electrode of the monolithic ceramic capacitor using
However, when it is applied to a laminated ceramic capacitor that uses Cu, Ni, or the like for the internal electrodes, it burns in the air, and the connection between the internal and external electrodes is oxidized to obtain the required electrical characteristics. It's gone.

Therefore, it is important to prevent oxidation of the internal electrode layers in the step of forming external electrodes to obtain good electrical connectivity and strong adhesion.

As an external electrode composition of a monolithic ceramic capacitor having an internal electrode layer using a base metal material, Japanese Patent Publication No. 63-14856 and Japanese Patent Publication No. 8-4055 disclose that copper powder is 50% by weight or more and 80% by weight or more. It is disclosed that a copper paste having the following range, a glass frit in the range of 5% by weight to 20% by weight and a range of the organic vehicle in the range of 10% to 30% by weight is applied and baked in a reducing atmosphere. . The baking in this reducing atmosphere is performed in a N ₂ atmosphere at a temperature of 600 to 900 ° C.,
After the chip parts are inserted into the furnace, the furnace removal time is about 60 minutes. Here, in order to efficiently decompose the organic vehicle component in the paste, JP-A-5-24308 is used.
As disclosed in Japanese Unexamined Patent Publication No. 3 (1999), Japanese Unexamined Patent Publication (Kokai) No. 11-195553, etc., in a temperature zone of 300 to 600 ° C., a small amount of oxygen of 100 ppm or less is doped in N ₂ atmosphere and baking is performed.

[0007]

Conventionally, the external electrode baking with Cu is low in order to prevent the deterioration of the electrical connection with the internal electrode layer due to the oxidation of Cu and to obtain the adhesion with the dielectric ceramic. Oxygen concentration is used.

However, when the amount of processing for baking the external electrode was increased, the binder was not decomposed in the zone for binder removal for decomposing the organic vehicle in an atmosphere containing several tens of ppm of oxygen and was not decomposed. If the organic vehicle component remains in the Cu external electrode, the adhesiveness with the dielectric ceramic is reduced due to the change in oxygen partial pressure during the decomposition of the vehicle even at the melting temperature of the glass frit, and the contraction rate of the Cu paste is reduced. Becomes large and residual stress remains, so there were problems in high temperature load, humidity resistance test, and reliability after mounting on the board.

When glass frit containing zinc such as zinc borosilicate is used, it is necessary to perform Ni plating in order to prevent whiskers when Sn plating is applied in the plating step after baking. However, since the Ni plating such as Watt bath is acidic, the Ni plating solution easily penetrates into the external electrode, which causes problems such as deterioration of withstand voltage, insulation, and delamination. It was

Therefore, the technical problem of the present invention is to reduce the residual stress due to the contraction of the Cu paste without lowering the adhesion with the dielectric ceramic in the baking process, and also to withstand the voltage and insulation in the plating process. It is an object of the present invention to provide a method for manufacturing a monolithic ceramic capacitor capable of forming an external electrode terminal without causing deterioration of properties and delamination.

[0011]

According to the present invention, a laminated ceramic capacitor having external electrodes provided on a laminated body formed by alternately stacking a plurality of dielectric ceramic layers and internal electrode layers containing Ni as a main component is formed. In the manufacturing method of
After baking a conductive paste containing Cu as a main component in at least one of a reducing atmosphere and a vacuum atmosphere as a first external electrode layer electrically connected to the internal electrode layer containing A second external electrode layer is formed on the first external electrode layer by applying at least one of low-resistance conductive pastes such as Cu, Ni, and Ag at a temperature lower than that of the first external electrode layer in a reducing atmosphere and a vacuum atmosphere. It is possible to obtain a method for manufacturing a laminated ceramic capacitor in which external electrodes are formed by two or more electrode layers which are neutral Ni-plated and Sn-plated after baking in at least one atmosphere.

According to the present invention, Cu metal powder and zinc borosilicate are used as the conductive paste containing Cu as a main component of the first external electrode layer electrically connected to the internal electrode layer containing Ni as a main component. And two or more types of C composed of glass frit not containing lead borosilicate and organic vehicle and having different particle sizes
By using u metal powder, when baked in at least one of a reducing atmosphere and a vacuum atmosphere,
A method of manufacturing a monolithic ceramic capacitor in which the void state in the first external electrode layer is 5 to 20% is obtained.

That is, according to the present invention, the dielectric ceramic layer and the N
In a method for manufacturing a laminated ceramic capacitor, in which external electrodes are provided on a laminated body formed by alternately stacking a plurality of internal electrode layers containing i as a main component, and the external electrodes are plated, the internal electrode layers and the As a first external electrode layer to be electrically connected, a conductive paste containing Cu as a main component is baked in at least one of a reducing atmosphere and a vacuum atmosphere, and then a first external electrode layer is formed on the first external electrode layer. A multilayer ceramic capacitor, wherein at least one kind of low resistance conductive paste is baked as a second external electrode layer at a temperature lower than that of the first external electrode layer in at least one atmosphere of a reducing atmosphere and a vacuum atmosphere. It is a manufacturing method.

Further, according to the present invention, in the above-mentioned method for manufacturing a monolithic ceramic capacitor, Cu is used as a conductive paste used for the internal electrode layers and the first external electrode layers.
Powder, glass frit not containing Zn and Pb, and an organic vehicle, two or more kinds of Cu powders having different particle sizes are used, and baked in at least one atmosphere of a reducing atmosphere and a vacuum atmosphere. A method of manufacturing a monolithic ceramic capacitor, wherein the porosity in the external electrode layer is 5 to 20%.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of a monolithic ceramic capacitor of an embodiment manufactured by the electrode terminal forming method of the present invention. As shown in FIG. 1, a dielectric ceramic 1 containing barium titanate (BaTiO ₃ ) as a main component 1
Internal electrodes 2 made of Ni are alternately laminated, first Cu external electrodes 3 for obtaining electrical connection with the internal electrodes are formed at both ends of the chip, and second A external electrodes 3 are formed on the first Cu external electrodes 3.
g A laminated ceramic capacitor 10 is formed by applying a plating layer 5 on the external electrodes 4 by baking.

FIG. 2 is a sectional view of a laminated ceramic capacitor of another embodiment manufactured by the electrode terminal forming method of the present invention. As shown in FIG. 2, BaTiO ₃
Internal electrodes 2 made of Ni are alternately laminated on a dielectric ceramic 1 containing as a main component, and first Cu external electrodes 3 for electrically connecting to the internal electrodes are formed at both ends of the chip.
The second Cu external electrode 6 is formed on the first Cu external electrode 3 by baking, and the plating layer 5 is formed on the second Cu external electrode 6 to form the monolithic ceramic capacitor 20.

The second Cu external electrode 6 used was one in which the amount of glass frit added was changed from that of the first Cu external electrode 3 and the baking temperature was lowered by 50 ° C.

In the case of FIG. 1, the plating layer 5 is Sn for ensuring solder wettability at the time of mounting with the second Ag external electrode 4.
In order to prevent characteristic deterioration due to diffusion with plating, neutral electroless Ni plating with a thickness in the range of 2 μm to 3 μm is used.
After coating on the Cu external electrode, neutral electrolytic Sn plating was applied to a thickness in the range of 6 μm to 12 μm.

Here, if the Ni plating is less than 2 μm, the peel strength is lowered, and if it exceeds 3 μm, the tensile stress due to the Ni plating becomes large. Therefore, the Ni plating has a thickness in the range of 2 μm or more and 3 μm or less. . Also, S
When the n plating is less than 6 μm, the wettability with solder becomes insufficient, and the solder joint variation becomes large, and when it exceeds 12 μm, the plating time becomes long. Therefore, Sn plating is performed in the range of 6 μm to 12 μm. And

The monolithic ceramic capacitors 10 and 20 of the present invention shown in FIGS. 1 and 2 were manufactured as follows. BaTiO ₃ powder as a main component as a dielectric ceramic, an organic binder, a dispersant, a plasticizer, and an organic solvent are weighed, kneaded to form a slurry, and a green sheet is formed using a doctor blade method or the like, and then Ni powder The paste for the internal electrode 2 obtained by kneading and the organic vehicle was laminated on the green sheet by screen printing, and the laminate obtained by hot pressing was cut into a predetermined chip size. A ceramic capacitor chip element is obtained. After firing the ceramic capacitor chip element in the atmosphere, Cu powder, in order to obtain an electrical connection,
A terminal paste to be the first external electrode 3 made of glass frit and an organic vehicle was applied.

An example of baking the external electrode terminal paste in the embodiment of the present invention will be described with reference to FIG. As shown in FIG. 3, the baking time in the furnace is 80
Minutes, the temperature of the first constant temperature holding section is 300 ° C., 1
After holding for 0 minutes, the temperature in the second constant temperature holding section was held at 900 ° C. for 10 minutes. The baking is performed in N ₂ as a baking atmosphere, and the oxygen concentration in the first holding section is 20 p.
pm, and the oxygen concentration in other sections was set to 5 ppm, and the external electrodes were baked.

Next, after a terminal paste to be the second external electrodes 4 or 6 was applied, baking was performed with the same baking profile as the baking of the first external electrode terminals.
However, the temperature in the second constant temperature holding section of the baking profile was 800 to 850 ° C. Neutral Ni plating after baking (either electrolytic or electroless is acceptable)
Was performed in the barrel, and then neutral Sn plating was performed to obtain a multilayer ceramic chip capacitor.

Next, the external electrode terminal paste according to the embodiment of the present invention will be described. For the first external electrode terminal paste, two or more kinds of metal powders having different particle sizes were used, and the state of the holes 7 in the electrode layer after baking the external electrode was changed. As the inorganic component, spherical copper powder having an average particle size of 1 μm and spherical copper powder having an average particle size of 10 μm or less, which is larger than the powder particle size, and Ba or Si-based glass frit are blended, and 80 to 95% by weight of this inorganic component is mixed. After that, an organic vehicle was added to the rest to make 100% by weight, and the mixture was kneaded with a three-roll mill to prepare a paste for external electrodes.

In the second external electrode terminal paste,
In order to make the melting temperature of the external electrode lower than that of the first external electrode, the spherical powder has a particle size of 1 μm or less, and is mixed with Ba and Si based glass frit, and the inorganic component is 80 to 95% by weight, and the balance is an organic vehicle. Was added to 100% by weight and kneaded with a three-roll mill to prepare a paste for external electrodes.

FIG. 4 shows a schematic diagram of the external electrode terminals of the laminated ceramic capacitor baked under the external terminal baking conditions according to the embodiment of the present invention.

As shown in FIG. 4, a first Cu external electrode 3 is formed on a chip composed of one layer of dielectric ceramic and two layers of Ni internal electrode, and a second Ag external electrode 3 is formed on the first Cu external electrode 3.
The external electrode 4 is baked and formed with a plating layer 5, and the first Cu external electrode 3 has pores due to the change in the metal powder molten state caused by the binder removal of the organic vehicle and the difference in the metal powder particle size. Forming 7.

This paste is applied to a laminated ceramic capacitor chip and baked under the external terminal baking conditions according to the above-described embodiment of the present invention to obtain electrical characteristics, mechanical characteristics (adhesion strength) and reliability. Was tested.

The multilayer ceramic capacitor chip was designed to have a length of 3.2 × width of 1.6 × thickness of 1.0 mm and a capacitance of 1 μF. Regarding the electrical characteristics of the obtained multilayer ceramic capacitor, the capacitance (C) was measured using an LCR meter. For joint strength,
Φ1mm on the external electrode terminal using the tensile compression tester
The pin was vertically joined with solder and fixed, and pulled to measure. As a criterion for determination, the capacitance variation is within ± 10%, and the adhesion strength is 1.5 kgf / m at which the external electrodes do not peel off when mounted on the board by soldering.
m ² or more was regarded as a good product. For the external electrode hole state,
The laminated ceramic capacitor chip was embedded in resin and polished, and then the porosity in the external electrode layer was measured using an image analyzer. Regarding the reliability, a high temperature load test for judging pass / fail by a change in insulation resistance after leaving for 500 hours by applying a voltage four times the rated voltage at a temperature of 125 ° C, a temperature of 85 ° C
And a humidity resistance load test with a humidity of 85% RH was performed. The results are shown in Table 1.

[0030]

[Table 1]

From the results of Table 1, when the porosity of the first Cu external electrode layer is less than 5%, the electrical characteristics and the adhesion strength are good, but the first Cu external electrode layer and the laminated ceramic capacitor chip are good. In the high temperature load test, the shrinkage stress when Cu is baked on the chip and the internal stress when the chip is baked are not relaxed because the adhesion with the film is strong and the porosity is small, and the failure occurrence rate due to insulation resistance deterioration increases. ing.

Further, the porosity of the first Cu external electrode layer is 3
If it is 1% or more, the electrical connection with Ni of the internal electrode layer is not secured, and the variation of the electrical characteristics becomes large, and
Similar to the electrical characteristics, the adhesion strength also varied greatly, and the adhesion strength also decreased.

For the chip (conventional example) prepared for comparison, in which the second external electrode layer was not formed, even if the porosity of the first external electrode layer was within the range of 5 to 20%, plating was performed. Due to the permeation of the liquid, the moisture resistance load characteristic was deteriorated.

By the method for manufacturing a monolithic ceramic capacitor according to the embodiment of the present invention, an external electrode having high electric characteristics and adhesion strength was formed, and high reliability was obtained.

As described above, in the embodiment of the present invention, the conductive paste composition is composed of Cu metal powder, glass frit excluding zinc borosilicate and lead borosilicate, and an organic vehicle. In addition to being lead-free, heat treatment for preventing whiskers of Sn plating and stress relaxation of Ni plating can be eliminated.

Further, in baking in a reducing atmosphere and a vacuum atmosphere, the furnace temperature is raised to the binder removal temperature at which the organic vehicle component in the conductive paste is decomposed, and the first temperature raising step and binder removal are aimed at. By having the first step of maintaining a constant temperature in the range of 400 to 400 ° C., the binder in the external electrode can be sufficiently removed, and by controlling the porosity of the first external electrode layer, electrical connection and It is possible to provide a multilayer ceramic capacitor having good adhesion and high reliability.

[0037]

As described above, according to the present invention,
External electrode terminals that do not reduce the adhesion with the dielectric ceramic during the baking process, alleviate the residual stress due to the contraction of the Cu paste, and do not cause deterioration of withstand voltage, insulation and delamination during the plating process. It was possible to provide a method for manufacturing a monolithic ceramic capacitor capable of forming.

[Brief description of drawings]

FIG. 1 is a sectional view of a monolithic ceramic capacitor manufactured by a manufacturing method according to an embodiment of the present invention.

FIG. 2 is a sectional view of a laminated ceramic capacitor of another embodiment manufactured by the manufacturing method of the present invention.

FIG. 3 is a diagram showing an external electrode terminal baking temperature profile in the present invention.

FIG. 4 is a schematic view of a monolithic ceramic capacitor according to an embodiment manufactured by a manufacturing method according to the present invention.

[Explanation of symbols] 1 Dielectric ceramic 2 internal electrodes 3 First (Cu) external electrode 4 Second (Ag) external electrode 5 plating layer 6 Second (Cu) external electrode 7 holes 10, 20 Multilayer ceramic capacitors

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5E082 AB03 BC33 EE04 EE23 EE35                       FG26 GG10 GG11 GG28 JJ03                       JJ12 JJ23 LL01 MM24 PP10

Claims (2)

[Claims] 1. A laminated ceramic capacitor having external electrodes provided on a laminate formed by alternately stacking a plurality of dielectric ceramic layers and internal electrode layers containing Ni as a main component, and the external electrodes being plated. In the manufacturing method, as the first external electrode layer electrically connected to the internal electrode layer,
After baking the conductive paste containing Cu as a main component in at least one of a reducing atmosphere and a vacuum atmosphere,
At least one kind of low-resistance conductive paste is used as a second external electrode layer on the first external electrode layer at a temperature lower than that of the first external electrode layer and at least one of a reducing atmosphere and a vacuum atmosphere. A method for manufacturing a monolithic ceramic capacitor, which is characterized by being baked by. 2. The method for manufacturing a monolithic ceramic capacitor according to claim 1, wherein the conductive paste used for the internal electrode layer and the first external electrode layer is Cu powder and a glass frit containing no Zn or Pb. Two or more kinds of Cu powders having different particle sizes are used, which are made of an organic vehicle, and baked in at least one of a reducing atmosphere and a vacuum atmosphere, and the porosity in the first external electrode layer is 5 to 5%. 20% of the manufacturing method of the laminated ceramic capacitor.