KR20030037351A - Method For Manufacturing Multilayer Ceramic Capacitor - Google Patents

Abstract

PURPOSE: A method is provided to be capable of simplifying a process and of improving the adhesive strength and property of an external electrode. CONSTITUTION: A Cu inner electrode is printed on a shaped dielectric sheet, and a green chip is fabricated by stacking, compressing and cutting the dielectric sheet where the inner electrode is printed. An external electrode which consists of Cu metal of 40-70 weight%, a bonding agent of 1.6-5.6 weight% and remaining solvent paste, is made. The external electrode paste is coated at both ends of the green chip. A sintering process for the inner and outer electrodes is performed at a temperature of 870-1000 degrees under a deduction atmosphere.

Description

Method for manufacturing multilayer ceramic capacitors {Method For Manufacturing Multilayer Ceramic Capacitor}

The present invention relates to a method of manufacturing a laminated ceramic capacitor, and more particularly, to a method of manufacturing a laminated ceramic by simultaneously firing internal and external electrodes.

Multilayer ceramic capacitors (MLCCs, hereinafter simply referred to as "MLCCs") are used as functions such as DC signal blocking, bypassing, and frequency resonance, and are classified according to temperature characteristics.

The use of MLCC has been increased in accordance with the demand for miniaturization and light weight of electronic products, and explosive demand has been created due to the digitalization of electronic products and the expansion of the mobile communication market.

The MLCC is manufactured by printing an electrode paste on a green sheet, laminating it in multiple layers, cutting and sintering at a high temperature, and then applying, sintering and plating an external electrode.

Conventionally, after firing a ceramic capacitor body in which a dielectric layer made of a reducing-resistant dielectric composition and a Cu inner electrode layer are alternately laminated, an outer electrode mainly composed of Glass Frit and Cu metal is applied to both ends thereof, and then fired again. A laminated ceramic capacitor was prepared.

Referring to Figure 1 showing a representative example of a conventional method for manufacturing MLCC will be described with respect to the method for manufacturing MLCC.

That is, in the conventional MLCC manufacturing method, as shown in FIG. 1, preparing a powder of Ca (Ti _x Zr _1-x ) O ₃ , MnO, and Glass Frit, slurrying the prepared powder, and preparing the slurry Molding into a dielectric sheet, printing a Cu internal electrode on the dielectric sheet, laminating a sheet with an internal electrode printed thereon, and compressing the laminated sheet at a pressure of 500 to 1300 kgf / cm ² , compressing the lamination A method of manufacturing a green chip by cutting a sheet, burn-out of the green chip manufactured as described above for 20 to 40 hours at a temperature of 230 to 350 ° C. and a pressure condition of P _{O 2} = 10 ^{−6 to} Air. Firing at a temperature of 900 to 950 ° C. and a pressure condition of P _{O 2} = 10 ⁻¹⁵ to 10 ⁻¹⁰ for 10 hours, and after applying the external electrode, a temperature of 750 to 950 ° C. and a P _{O 2} = 10 ⁻ After baking for 0.5 to 2 hours at a pressure of ¹⁵ ~ 10 ^-6 , it comprises a step of plating.

As described above, the firing for the internal electrode and the firing for the external electrode are conventionally performed separately.

That is, as shown in Fig. 2 (a), after the internal electrode (2) is printed on the ceramic body (1) and subjected to the primary firing for the internal electrode, as shown in Fig. 2 (b), the internal electrode After the external electrodes 3 were formed at both ends of the ceramic body 1 on which (2) was formed, secondary firing was performed.

However, in the case of attaching the external electrode after the primary firing for the internal electrode as in the related art, since the firing is performed first and second, the firing time is long, the productivity is lowered, and the electrode is attached to the already fired. There is a problem that falls and thereby the contact and adhesive strength is lowered.

The present inventors have conducted research and experiments to solve the above-mentioned problems of the conventional method, and based on the results, the present invention proposes a ceramic body of a low-temperature calcined MLCC using Cu internal electrodes. It is an object of the present invention to simplify a process by simultaneously firing an electrode and an external electrode, and to provide a method for manufacturing an MLCC that can improve adhesion strength and contactability of an external electrode.

1 is a process flowchart showing a process of manufacturing a laminated ceramic capacitor according to a conventional method.

Fig. 2 is a schematic diagram of a laminated ceramic capacitor for explaining the firing process according to the conventional method, in which (a) shows the state before the primary firing, and (b) shows the state before the secondary firing. Schematic diagram of laminated ceramic capacitors to illustrate the simultaneous firing process

Explanation of symbols on the main parts of the drawings

One . . . Ceramic body 2. . . Internal electrode 3. . . External electrode

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The present invention includes the steps of printing a Cu internal electrode on a molded dielectric sheet, laminating, pressing, and cutting a dielectric sheet on which the internal electrode is printed to manufacture a green chip;

Preparing an external electrode paste composed of 40 to 70 wt% of Cu metal, 5 to 20 wt% of common material, 1.6 to 5.6 wt% of binder, and remaining solvent;

Applying the external electrode paste prepared as described above to both ends of the green chip before calcining the green chip; And

The present invention relates to a method of manufacturing a multilayer ceramic capacitor, comprising the step of calcining after applying the external electrode paste as described above, and then firing the internal electrode and the external electrode at a temperature of 870 to 1000 ° C. under a reducing atmosphere.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

In order to manufacture a multilayer ceramic capacitor according to the present invention, _first , dielectric powders of Ca (Ti _x Zr _1-x ) O ₃ , MnO, and Glass Frit are prepared.

As Ca (Ti _x Zr _1-x ) O ₃ , CaZrO ₃ or CaTiO ₃ synthesized by hydrothermal synthesis or the like is preferably used. In Ca (Ti _x Zr _1-x ) O ₃ , x is 0.01 ≦ x. It is preferable to set ≤ 0.1.

The amount of MnO added is preferably set to 1.0-5.0 wt%.

The glass frit is preferably a Ca-Li-B-Al-Si-based oxide, and the amount of the glass frit is preferably set to 1.0 to 5.0 wt%.

Next, the dielectric powder prepared as described above is slurried in a batch process.

The dielectric slurry is a mixture of a dielectric powder, an organic binder, and a solvent, and the organic binder can be appropriately selected from various binders such as PVB and acrylic.

Next, the dielectric slurry is molded into a dielectric sheet.

Next, a Cu internal electrode is printed on the dielectric sheet, a sheet on which the internal electrode is printed is laminated, and the laminated sheet is compressed, and then the compressed laminated sheet is cut according to a predetermined shape to manufacture a green chip.

The Cu internal electrode paste is prepared by mixing Cu, a conductive metal, and various oxides, binders, and solvents.

In the crimping, the crimping pressure is preferably set to 500 to 1300 kgf / cm ² .

Next, the green chip manufactured as described above is green polished to make the corner portion curved, and then external electrode paste is applied to both ends.

The external electrode paste is composed of 40 to 70 wt% of Cu metal, 5 to 20 wt% of common material, 1.6 to 5.6 wt% of binder, and the remaining solvent.

The Cu metal may be used alone or mixed with a spherical form and a flake form, but it is preferable to use a mixture, and more preferably, a mixture of a spherical form and a flake form is used so that spherical / flakes ≧ 1.

The Cu metal is preferably selected from 40 to 70 wt%.

In case of using glass frit as in the conventional method, the sintering density of the external electrode is very high due to the long simultaneous firing time. In order to prevent this phenomenon, the common electrode is used instead of the glass frit in order to prevent the phenomenon.

The common material is selected to not affect the properties as a component having the same or similar composition and physical properties as the dielectric composition to prevent cracking due to the difference in shrinkage between the ceramic and the metal.

When the content of the common material is too small, the external electrode is lifted due to the difference in shrinkage between the external electrode and the ceramic, or microcracks occur in the body, and when the content of the common material is too high, the common material occupies the entire surface of the external electrode. Since there are too many portions and plating bleeding occurs, the content thereof is preferably selected from 5 to 20 wt%.

On the other hand, when the acrylic binder is used as the binder as in the conventional method, the viscosity ratio according to the change of shear stress is large, and the thickness of the external electrode is thick as about 40-50 μm after rolling, so that the internal electrode and the dielectric are interposed in the plasticizing process. It was confirmed that delamination occurred in the.

Further studies in this regard confirmed that in the present invention, it is preferable to use a cellulose binder as a binder.

That is, in the case of using a cellulose-based binder, the viscosity ratio according to the change of the shear stress is low, so that the external electrode is thin and uniformly applied, so that it is easy to plasticize.

When using a cellulose-based binder as described above, the thickness of the external electrode is about 20-30㎛.

In the conventional method, when the thickness of the external electrode is thin, deterioration of characteristics due to penetration of the plating solution occurs during plating, but the thickness of the external electrode should be thick. There is no.

It is preferable to use ethyl cellulose as the binder.

The content of the binder is preferably selected to 1.6 ~ 5.6wt%.

In addition, the external electrode paste may have a viscosity of 15,000 to 40,000 cps (10 rpm).

Next, as described above, the green chip on which the inner electrode is printed and the outer electrode is coated is calcined and debindered, followed by firing to manufacture a laminated ceramic capacitor.

That is, as shown in FIG. 3, the internal electrode 2 and the external electrode 3 are formed in the ceramic body 1, and then they are calcined and fired simultaneously.

The calcining is carried out at a temperature of 200 to 600 ° C., preferably 230 to 350 ° C., for at least 5 hours, preferably about 20 to 40 hours, under a reducing component atmosphere.

The binder removal process (calcination) of the green chip is preferably performed in a reducing component atmosphere to prevent oxidation of the internal electrode and the external electrode, and a nitrogen atmosphere is more preferable.

At the time of firing, the atmosphere is a reducing component crisis, the firing temperature is selected from 870 ~ 1000 ℃, preferably 900 ~ 950 ℃, and the firing time is 5 hours or more, preferably 5 to 20 hours, more preferably 9 Select from 12 hours.

After firing as described above, Ni plating and Sn / Pb plating are sequentially performed.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example

Ca (Ti _0.03 Zr _0.97 ) O ₃ powder was prepared using CaZrO ₃ and CaTiO ₃ synthesized by hydrothermal synthesis.

MWO 3.0wt% and Ca-Li-B-Al-Si oxide, Glass Frit 3.5wt, based on 100 parts by weight of Ca (Ti _0.03 Zr _0.97 ) O ₃ and Ca (Ti _0.03 Zr _0.97 ) O ₃ prepared as described above The dielectric powder was prepared by mixing%.

The dielectric powder slurry was prepared by mixing 10 wt% of the resin, 40 wt% of the plasticizer, and 8 times the solvent of the resin with respect to the dielectric powder prepared as described above and 100 parts by weight of the dielectric powder.

Using the slurry prepared as described above to prepare a dielectric sheet and printed Cu internal electrode.

After stacking five layers of dielectric sheets printed with internal electrodes as described above, the sheets were pressed at a pressure of 1000 kg / mm ² and then cut to prepare a green chip.

After applying the external electrode paste prepared as shown in Table 1 on both ends of the green chip prepared as described above, and calcined at 300 ℃ for 25 hours under a nitrogen atmosphere, it was performed for 10 hours under the firing temperature conditions shown in Table 1 .

The electrical characteristics of the chip manufactured as described above were measured using Agilent's 4278A LCR meter and 4339B High resistance meter to measure the quality factor (Q) and IR value, and the tape test was used to measure the external electrode. The adhesive strength was measured, and the breakage of the Ni plated layer was examined by plating test, and the results are shown in Table 2 below.

The tape test is a method of evaluating the adhesive strength of the external electrode. In this embodiment, the plated chip was attached to the tape, and then peeled off, and then the number of external electrodes fell.

In addition, the plating test was used to check the degree of breakage of Ni plating by polishing the finished chip.

Example No. Form of Cu Cu content (wt%) Vacancy content (wt%) Resin amount (wt%) Solvent Viscosity (CPS) Firing temperature (℃) Comparative Example 1 100% spherical 66 4.62 3.94 Remainder 39.000 950 Inventive Example 1 100% spherical 59 11.8 3.54 Remainder 28.000 950 Comparative Example 2 Spherical / flakes = 50/50 60 4.2 3.6 Remainder 35.000 950 Inventive Example 2 Spherical / flakes = 50/50 56 11.2 3.36 Remainder 32.000 950 Comparative Example 3 Spherical / flakes = 50/50 51 20.4 3.06 Remainder 39.000 950 Comparative Example 4 100% spherical 66 4.62 3.94 Remainder 39.000 925 Inventive Example 3 100% spherical 59 11.8 3.54 Remainder 28.000 925 Comparative Example 5 Spherical / flakes = 50/50 60 4.2 3.6 Remainder 35.000 925 Inventive Example 4 Spherical / flakes = 50/50 56 11.2 3.36 Remainder 32.000 925 Comparative Example 6 Spherical / flakes = 50/50 51 20.4 3.06 Remainder 39.000 925

Example No. Q IR Plating failure rate (%) Tape testing Comparative Example 1 3263 3.48E + 14 0% Poor: 3/50 Inventive Example 1 3135 2.38E + 14 0% Good Comparative Example 2 2930 1.91E + 14 0% Poor: 3/50 Inventive Example 2 2878 1.47E + 14 0% Good Comparative Example 3 3010 1.54E + 14 40% Good Comparative Example 4 3126 3.86E + 14 0% Poor: 8/50 Inventive Example 3 3065 3.54E + 14 0% Good Comparative Example 5 3202 2.62E + 14 0% Poor: 8/50 Inventive Example 4 3082 2.64E + 14 0% Good Comparative Example 6 3045 1.67E + 14 30% Good

As shown in Table 2, in the case of Inventive Examples (1) to (4) manufactured according to the present invention, not only the Q value and the IR value were excellent, but also no plating defect was generated, and the tape test also appeared well. It can be seen.

On the other hand, in the case of Comparative Examples (1), (2), (4) and (5) in which the common material was added less than the scope of the present invention, tape test results were poor, and the common material was more than the scope of the present invention. In the case of the added Comparative Examples (3) and (6) it can be seen that the plating failure occurs.

In the above, the case where the internal electrode is Cu has been described, but the present invention is also applied to the case where Ni is used as the internal electrode.

As described above, since the firing of the internal and external electrodes proceeds at the same time, the process of firing the external electrodes does not need to be performed separately, thereby reducing the cost and lead time due to external electrode firing.

In addition, the present invention has an effect that can provide a laminated ceramic capacitor with improved adhesive strength of the external electrode and the contact between the internal and external electrodes.

Claims (8)

Printing a Cu internal electrode on the molded dielectric sheet, and stacking, pressing, and cutting the dielectric sheet on which the internal electrode is printed to manufacture a green chip; Preparing an external electrode paste composed of 40 to 70 wt% of Cu metal, 5 to 20 wt% of common material, 1.6 to 5.6 wt% of binder, and remaining solvent; Applying the external electrode paste prepared as described above to both ends of the green chip before calcining the green chip; And After applying the external electrode paste as described above, calcining, and then firing for the internal electrode and the external electrode at a temperature of 870 ~ 1000 ℃ under a reducing atmosphere comprising the step of manufacturing a multilayer ceramic capacitor. The method of manufacturing a multilayer ceramic capacitor according to claim 1, wherein the firing temperature is 900 to 950 ° C and the firing time is 9 to 12 hours. The method of manufacturing a multilayer ceramic capacitor according to claim 1 or 2, wherein the binder is a cellulose-based binder. The method of manufacturing a multilayer ceramic capacitor according to claim 3, wherein the binder is an ethyl cellulose binder. The method for producing a multilayer ceramic capacitor according to claim 1, 2 or 4, wherein calcining is carried out at a temperature of 200 to 600 캜 for at least 5 hours under a reducing component atmosphere. The method of manufacturing a multilayer ceramic capacitor according to claim 3, wherein the calcining is performed at a temperature of 200 to 600 캜 for at least 5 hours under a reducing component atmosphere. The method for producing a multilayer ceramic capacitor according to claim 5, wherein the calcining temperature is 230 to 350 캜 and the calcining time is 20 to 40 hours. The method for producing a multilayer ceramic capacitor according to claim 6, wherein the calcining temperature is 230 to 350 캜 and the calcining time is 20 to 40 hours.