JP2003059758A - Method of manufacturing multilayer ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a multilayer ceramic capacitor, which prevents the oxidation of an electrode layer at baking by applying a Cu external electrode on the multilayer ceramic capacitor where the internal electrode is Ni and the dielectric ceramic is barium titanate, and which does not cause nonconformity in a plating process. SOLUTION: This a manufacturing method for a multilayer ceramic capacitor which gives neutral Ni plating and Sn plating to an external electrode after baking it in unoxidative atmosphere with a conductive paste containing based metal, in a multilayer ceramic capacitor which is constituted by providing a laminate being made by alternately multilayer dielectric ceramic layers and internal electrode layers having Ni for its main ingredients with an external electrode.

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 by a doctor blade method or the like in which a slurry is prepared by dispersing and mixing a dielectric ceramic powder containing barium titanate as a main component and a binder such as an organic resin in an organic solvent. A green sheet is produced by forming a film with a constant thickness. Next, an internal electrode paste made of a low resistance metal such as copper (Cu) or nickel (Ni) and an organic vehicle is printed on the green sheet by a screen printing method to form an internal electrode.

The green sheets, which are the electrodes in which the internal electrodes are alternately opposed to each other, are punched out, laminated in a mold and pressure-bonded by a hot press or the like to obtain a laminated body. 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.

Here, C used for the internal electrode layer
Unlike noble metals, u and Ni are easily oxidized, and it is important to prevent oxidation of the internal electrode layers in the external electrode formation step and 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 Cu powder is from 50% by weight to 80% by weight. %, A glass frit in the range of 5 wt% to 20 wt% inclusive, and an organic vehicle in the range of 10 wt% to 30 wt% inclusive may be applied and baked and formed in a non-oxidizing atmosphere. It is disclosed. FIG. 3 is a diagram showing a conventional electrode terminal baking temperature profile. This baking in a non-oxidizing atmosphere is performed at 600 ° C or higher to 9
The time from insertion of the chip component into the furnace to removal from the furnace in a N ₂ atmosphere at a temperature in the range of 00 ° C. or lower is about 60 minutes. Here, in order to efficiently decompose the organic vehicle component in the paste, JP-A-5-243083 and JP-A-11-11830 are used.
Such as disclosed in -195553, in the temperature zone ranging from 300 ° C. over 600 ° C. or less, N ₂
The atmosphere was doped with a trace amount of oxygen of 100 ppm or less and baked.

[0006]

Conventionally, the external electrode baking with Cu is performed at a low oxygen concentration in order to prevent deterioration of the electrical connection property with the internal electrode layer due to the oxidation of Cu and to obtain the adhesiveness with the dielectric ceramic. The external electrodes of are baked. However, when the amount of processing for baking the external electrode is increased, it is a zone for decomposing (debinding) the organic vehicle, the debinding is not sufficient in an atmosphere containing several tens of ppm of oxygen, and the undecomposed organic vehicle. If the components remain in the Cu external electrode, the adhesiveness of the dielectric material to the ceramic is reduced and the shrinkage rate of the Cu paste is large due to the change in oxygen partial pressure in the decomposition of the vehicle even at the melting temperature of the glass frit. Since residual stress remains, there is a problem that the plating process, solder heat resistance, etc. deteriorate.

Further, when a glass frit system containing zinc such as zinc borosilicate system is used and Sn plating is applied in the plating step after baking, Ni plating must be applied in order to prevent whiskers. . But,
When acidic Ni plating such as Watt bath is applied to a Cu external electrode with insufficient binder removal, the undecomposed organic vehicle leaves the external electrode in a porous state as residual carbon. There is a problem that it easily penetrates and causes deterioration of withstand voltage, insulation, and delamination.

According to the present invention, a Cu external electrode is applied to a monolithic ceramic capacitor in which the internal electrode is Ni and the dielectric ceramic is barium titanate to prevent oxidation of the electrode layer during baking, and also in the plating process. The present invention provides a method for manufacturing a monolithic ceramic capacitor that does not cause a problem.

[0009]

According to the present invention, an external electrode is provided in a laminate formed by alternately stacking a plurality of dielectric ceramic layers and an internal electrode layer containing a base metal such as Ni as a main component. In the laminated ceramic capacitor, the external electrode is manufactured by baking a conductive paste containing a base metal in a non-oxidizing atmosphere and a vacuum atmosphere, and then performing neutral Ni plating and Sn plating.

According to the present invention, in the conductive paste,
The metal content is in the range of 80% by weight to 95% by weight, the organic vehicle is in the range of 5% by weight to 20% by weight, and the Cu metal content as a metal component is 80% by weight to 98% by weight. And the range of Ti metal in the range of 2 wt% to 10 wt% or less can be obtained.

According to the present invention, in baking in a non-oxidizing atmosphere and a vacuum atmosphere, the furnace temperature is raised to the de-binder temperature for decomposing the organic vehicle component in the conductive paste, and the first heating section and the heating step. 300 for the purpose of binder
The first of the temperature maintenance in the range above ℃ to 400 ℃
And a second holding section at a temperature for melting the external electrode to obtain close contact with the ceramic, and after a certain period of time, baking is performed using an external electrode baking furnace that can cool the first electrode. In the case of baking in an inert gas atmosphere of Ar, N ₂ or the like in the holding section of, the oxygen concentration at the time of holding is carried out in an atmosphere of 10 ppm or more to 50 ppm or less, and in the case of baking in a vacuum atmosphere,
A method for producing a monolithic ceramic capacitor having a back pressure in the furnace of 1 × 10 ⁻⁴ Pa or less can be obtained.

According to the present invention, since the conductive paste composition is composed of Cu metal powder, Ti metal powder and organic vehicle, the chip can be made lead-free and whiskers at the time of Sn plating can be prevented. It becomes possible to eliminate heat treatment. Further, in baking in a non-oxidizing atmosphere and a vacuum atmosphere, the furnace temperature is up to the binder removal temperature that decomposes the organic vehicle component in the conductive paste,
A first temperature raising section for raising the temperature and the purpose of removing the binder 3
Since the binder in the external electrode can be sufficiently removed by having the first holding section for holding the constant temperature in the range of 00 ° C. or more and 400 ° C. or less, electrical connection and adhesion by oxidation are good and reliability is high. A method for manufacturing a high monolithic ceramic capacitor can be provided.

That is, according to the present invention, the dielectric ceramic layer and the N
In a multilayer ceramic capacitor in which external electrodes are provided in a laminate formed by alternately stacking a plurality of internal electrode layers containing i as a main component, the external electrodes are formed by baking a conductive paste containing a base metal in a non-oxidizing atmosphere. After that, neutral N
It is a method for manufacturing a monolithic ceramic capacitor which is subjected to i plating and Sn plating.

Further, in the present invention, in the conductive paste, the metal content is in the range of 80% by weight to 95% by weight and the organic vehicle is in the range of 5% by weight to 20% by weight. As a component, the Cu metal content is in the range of 90% by weight to 98% by weight,
A method for manufacturing a monolithic ceramic capacitor, wherein the metal content is in the range of 2% by weight to 10% by weight.

Further, according to the present invention, in the method for producing a monolithic ceramic capacitor, baking in a non-oxidizing atmosphere raises a furnace temperature to a binder removal temperature at which the organic vehicle component in the conductive paste is decomposed. Temperature rising section and from 300 ℃ to 400 ℃ for binder removal
Has a first holding section for temperature holding in the following range,
It has a second holding section at a temperature for melting the external electrode to obtain close contact with the ceramic, and after a certain period of time, baking is performed using an external electrode baking furnace capable of cooling,
In the holding section of, the oxygen concentration during holding is from 10 ppm or more to 50 in an inert gas atmosphere of Ar, N ₂ or the like.
This is a method for manufacturing a monolithic ceramic capacitor performed in an atmosphere in the range of ppm or less.

The present invention also relates to a dielectric ceramic layer and N
In a monolithic ceramic capacitor in which external electrodes are provided in a laminated body formed by alternately stacking a plurality of internal electrode layers containing i as a main component, the external electrodes are formed by baking a conductive paste containing a base metal in a vacuum atmosphere. This is a method for manufacturing a monolithic ceramic capacitor that is subjected to neutral Ni plating and Sn plating.

Further, in the present invention, in the conductive paste, the metal content is in the range of 80% by weight to 95% by weight and the organic vehicle is in the range of 5% by weight to 10% by weight. As a component, the Cu metal content is in the range of 90% by weight to 98% by weight,
A method for manufacturing a monolithic ceramic capacitor, wherein the metal content is in the range of 2% by weight to 10% by weight.

Further, in the present invention, in the method for producing a monolithic ceramic capacitor, the baking in a vacuum atmosphere is carried out in a first heating step in which the furnace temperature is raised to a binder removal temperature at which the organic vehicle component in the conductive paste is decomposed. Temperature zone,
It has a first holding section for holding the temperature in the range of 300 ° C to 400 ° C for the purpose of binder removal, and a second holding section depending on the temperature for melting the external electrode to obtain adhesion with the ceramic. A method for producing a monolithic ceramic capacitor, wherein after baking for a certain period of time, baking is performed using an external electrode baking furnace that can be cooled, and the back pressure in the furnace is set to 1 × 10 ⁻⁴ Pa or less in the first holding section.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a method for manufacturing a monolithic ceramic capacitor according to the present invention will be described below.

FIG. 1 is a sectional view of a monolithic ceramic capacitor manufactured by the method for manufacturing a monolithic ceramic capacitor according to the present invention. Internal electrodes 2 made of nickel (Ni) are alternately laminated on a dielectric ceramic 1 containing barium titanate as a main component, copper (Cu) external electrodes 3 are formed at both ends of the chip, and Cu external electrodes 3 are formed on the external electrodes 3. Plating layer 4
An explanation will be given by taking as an example a laminated ceramic capacitor having a form. The plating layer 4 is a neutral electroless Ni plating layer of 2 μm or more to 3 μm or less in order to prevent deterioration of characteristics due to diffusion of the Cu external electrode 3 and tin (Sn) plating for securing solder wettability during mounting. After coating the Cu external electrode with a thickness in the range of, a neutral electrolytic Sn plating was performed with a thickness in the range of 6 μm to 12 μm.

Here, if the Ni plating is less than 2 μm, the peel strength decreases, and if it exceeds 3 μm, the plating time becomes long. Therefore, the Ni plating should be from 2 μm to 3 μm.
The thickness was set in the range of μm or less. Further, when the Sn plating is less than 6 μm, the peel strength is lowered, and the thickness is 12 μm.
When it exceeds m, the plating time becomes long, so the Sn plating is made in the range of 6 μm to 12 μm.

Here, the above-mentioned monolithic ceramic capacitor comprises BaTiO ₃ powder as a dielectric ceramic as a main component, an organic binder, a dispersant, a plasticizer and an organic solvent, which are weighed, kneaded and slurried to obtain a doctor blade method or the like. After forming a green sheet by using, the internal electrode paste obtained by kneading the Ni powder and the organic vehicle was screen-printed to laminate the green sheet formed on the green sheet. A ceramic capacitor chip element is obtained by cutting into a chip size. After firing this ceramic capacitor chip element in a predetermined atmosphere, in order to obtain an electrical connection, C
An external electrode terminal paste composed of u powder and an organic vehicle was applied.

FIG. 2 is a diagram showing the baking temperature profile of the electrode terminals of the present invention. As shown in FIG. 2, the external electrode paste was baked at a temperature of 400 ° C. for 10 minutes as a first temperature holding section and a temperature of 900 ° C. as a second temperature holding section after the baking time in the furnace was 70 minutes. 10,
Hold for minutes. Performed in N ₂ as a baking atmosphere, the oxygen concentration in the first holding section is (a) 5 ppm,
(B) 20ppm, (c) 150ppm three levels,
The oxygen concentration in the other sections was set to be 5 ppm, and the external electrodes were baked. After baking, neutral Ni plating (either electrolytic or electroless) is performed in the barrel, and then neutral Sn plating is performed to obtain a monolithic ceramic chip capacitor.

Here, Table 1 is a comparison of the temperature profile, the electrical characteristics with respect to the baking atmosphere, and the mechanical characteristics (adhesion strength) in the manufacturing method of the laminated ceramic capacitor of the present invention.

Here, the invention 2 is a case where the temperature profile of the present invention shown in FIG. 2 is a vacuum atmosphere in all temperature regions and the back pressure in the furnace is 1 × 10 ⁻⁴ Pa or less. . Here, Table 1 is a comparison of the temperature profile in the baking of the electrode terminals, the electrical characteristics with respect to the baking atmosphere, and the mechanical characteristics (adhesion strength).

The laminated ceramic capacitor chip was set to have a length of 3.2 × width of 1.6 × thickness of 1.0 mm and an electrostatic capacity of 1 μF. With respect to the obtained multilayer ceramic capacitor, as an electric characteristic, the capacitance (C), the dielectric loss (tan δ) and the insulation resistance (IR) were measured using an LCR meter and an insulation resistance meter. Regarding the bonding strength, a tensile compression tester was used to fix a pin of φ1 mm vertically soldered on the external electrode terminal, and the tensile strength was measured by pulling. As a criterion of judgment,
The capacitance variation was within ± 10%, and the adhesion strength was 1.5 kgf / mm ² or more so that the external electrodes were not peeled off when the solder was mounted on the substrate.

[0027]

[Table 1]

From the results shown in Table 1, it is found that the capacitance is good in the range of 5 to 20 ppm of oxygen in the first holding section, and the adhesion strength is
In the first holding section, it is preferable that the oxygen is doped with 20 to 150 ppm of oxygen.

As a result of further study, it was found that the first holding section doped with 10 to 100 ppm of oxygen satisfies the electrostatic capacity and the adhesion strength. That is, when the oxygen concentration was less than 10 ppm, the adhesion strength was low and the external electrodes were peeled off in the plating process. Further, when the oxygen concentration is 101 ppm or more, Ni that is the internal electrode is oxidized and the variation of the capacitance is increased, so that stable electrical characteristics cannot be obtained. Further, conventionally, when the oxygen doping is 20 ppm or more when the temperature of the temperature rising portion in the temperature profile is 400 ° C. or more, Ni that is the internal electrode is oxidized and the variation in capacitance increases, and stable electrical characteristics can be obtained. lost.

Next, the composition of the conductive paste of the present invention will be described. Spherical Cu with an average particle size of 1 μm as a metal component
Powder and flakes Cu powder and Ti powder were blended as shown in Table 2, and this metal component was adjusted to 80 to 95% by weight,
Add organic vehicle to the rest to make 100% by weight
This roll mill was kneaded to prepare an external electrode paste.

This paste was applied to a monolithic ceramic capacitor chip and baked under the above-mentioned external electrode terminal baking conditions according to the embodiment of the present invention.

[0032]

[Table 2]

From the results shown in Table 2, the Cu powder of the metal component was 8
If it is less than 0%, the depletion part of the external electrode increases, the variation in the electrical characteristics increases, and the penetration of the plating solution increases, resulting in poor reliability. Further, when the Cu powder of the metal component is 96% or more, T which contributes to the bonding with the ceramic is
Since the amount of i powder was small, the bonding strength was low, and in some cases, it peeled off after solder mounting on the substrate.

In the present embodiment, 80% to 95% by weight of Cu powder was mixed with Ti powder in the balance, and an organic vehicle was added.
All the electrical characteristics of δ and IR were good, and the values as designed were obtained.

[0035]

According to the present invention, Cu as an external electrode terminal of a monolithic ceramic capacitor having a base metal internal electrode is used.
It is possible to provide a paste and a method for manufacturing a monolithic ceramic capacitor having high bonding strength and good electrical connectivity.

[Brief description of drawings]

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

FIG. 2 is a view showing an electrode terminal baking temperature profile of the present invention.

FIG. 3 is a view showing a conventional electrode terminal baking temperature profile.

FIG. 4 is a diagram showing a change in bonding strength with respect to the amount of Ti added.

[Explanation of symbols]

1 Dielectric ceramic 2 internal electrodes 3 external electrodes 4 plating layer

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5E001 AB03 AC04 AC09 AF00 AF06                       AH01 AH07 AH08 AH09 AJ03                 5E082 AB03 BC32 EE04 EE23 EE35                       FG26 FG54 GG10 GG11 GG26                       GG28 JJ03 JJ12 JJ23 LL01                       LL02 MM22 MM23 PP03 PP06                       PP07 PP10

Claims (6)

[Claims] 1. A monolithic ceramic capacitor in which external electrodes are provided in a laminated body formed by alternately stacking a plurality of dielectric ceramic layers and internal electrode layers containing Ni as a main component, wherein the external electrodes contain a base metal. After baking the conductive paste in a non-oxidizing atmosphere, neutral Ni plating and S
A method of manufacturing a monolithic ceramic capacitor, which comprises performing n plating. 2. The conductive paste has a metal content of 80% by weight to 95% by weight, an organic vehicle of 5% by weight to 20% by weight, and Cu metal as a metal component. The content is in the range of 90% by weight to 98% by weight and the content of Ti metal is 2% by weight.
From the above, the range is 10% by weight or less. 3. In the method for producing a monolithic ceramic capacitor, the baking in a non-oxidizing atmosphere is performed in a first temperature raising section in which a furnace temperature is raised to a binder removal temperature at which an organic vehicle component in a conductive paste is decomposed. And a first holding section for holding the temperature in the range of 300 ° C. to 400 ° C. for the purpose of binder removal, and a second holding section at a temperature for melting the external electrode to obtain close contact with the ceramic. After a certain period of time, baking is performed using an external electrode baking furnace capable of cooling, and in the first holding section, in an inert gas atmosphere of Ar, N _2, etc., when the oxygen concentration during holding is 10 ppm or more, The method for producing a monolithic ceramic capacitor according to claim 1 or 2, wherein the method is performed in an atmosphere of 50 ppm or less. 4. A monolithic ceramic capacitor in which external electrodes are provided in a laminated body formed by alternately stacking a plurality of dielectric ceramic layers and internal electrode layers containing Ni as a main component, wherein the external electrodes contain a base metal. A method for manufacturing a monolithic ceramic capacitor, which comprises baking a conductive paste in a vacuum atmosphere and then performing neutral Ni plating and Sn plating. 5. The conductive paste has a metal content of 80% by weight to 95% by weight, an organic vehicle of 5% by weight to 10% by weight, and Cu metal as a metal component. The content is in the range of 90% by weight to 98% by weight and the content of Ti metal is 2% by weight.
From the above, the range is 10% by weight or less, and the method for manufacturing a monolithic ceramic capacitor according to claim 4. 6. In the method for manufacturing a monolithic ceramic capacitor, baking in a vacuum atmosphere comprises a first temperature raising section in which a furnace temperature is raised to a binder removal temperature at which an organic vehicle component in a conductive paste is decomposed. It has a first holding section for holding the temperature in the range of 300 ° C to 400 ° C for the purpose of binder removal, and a second holding section depending on the temperature for melting the external electrode to obtain adhesion with the ceramic. After a certain period of time, baking is performed using an external electrode baking furnace capable of cooling, and in the first holding section,
The method for producing a monolithic ceramic capacitor according to claim ⁴ , wherein the back pressure in the furnace is set to 1 × 10 ⁻⁴ Pa or less.