JP3087450B2 - Manufacturing method of multilayer ceramic capacitor - Google Patents

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 multilayer ceramic capacitor used for various electronic devices.

[0002]

2. Description of the Related Art Multilayer ceramic capacitors have been used in various electronic devices such as electronic tuners, video tape recorders, and video cameras because of their small size and large capacity.

Hereinafter, a method for manufacturing a conventional multilayer ceramic capacitor will be described.

FIGS. 1 and 2 show the structure of a multilayer ceramic capacitor. FIG. 1 is a sectional view in the longitudinal direction.
Is a cross-sectional view in the width direction. 1 and 2, reference numeral 1 denotes a dielectric ceramic, and a plurality of the dielectric ceramics 1 and internal electrodes 2 alternately reaching different ends are alternately laminated to electrically connect the internal electrodes 2 to each other. And external electrodes 3 provided at both ends.

The multilayer ceramic capacitor having the above structure is fired at a high temperature of 1300 ° C. or more.
The capacitance (hereinafter referred to as capacitance) of the multilayer ceramic capacitor is determined by the dielectric constant of the dielectric ceramic 1 and
It is determined by the area of the electrode overlapping portion of the opposing internal electrode 2, the thickness of the dielectric ceramic 1 between the opposing internal electrodes 2, and the number of layers, and is obtained by the following equation.

C = ε · ε ₀ · S · N / T where C: capacitance of the multilayer ceramic capacitor , S: induction
Of the electrode overlapping portion of the internal electrode 2 opposed via one layer of the conductor.
Area, ε ₀ : dielectric constant of vacuum [8.854 × 10 ⁻¹² (F /
m)], ε: dielectric constant of dielectric ceramic 1, T: dielectric thickness after firing, N: number of dielectric layers. This capacitance C is
It is determined when the dielectric ceramic 1 and the internal electrode 2 are integrally sintered, and it is difficult to adjust the capacitance thereafter.

As a method of adjusting the capacitance, (1)
Two methods of adjusting the capacitance on the surface of the laminate and (2) adjusting the capacitance inside the laminate have been proposed.

In the case of (1), it has been proposed that the capacitance is designed to be slightly smaller than the target value, and a structure is provided in which a capacitance adjusting electrode having a variable area is provided on the surface of the dielectric ceramic 1 after sintering. (See Japanese Utility Model Laid-Open Nos. 49-70448, 53-23535, and 55-32027). However, in such a structure, considering the actual use of the multilayer ceramic capacitor, it was necessary to cover the capacitance adjusting electrode provided outside with an insulator.

In the case of the above (2), for example, 30 laminated bodies are formed by laminating a lower ineffective layer which is not involved in the capacitance and an effective layer whose capacitance is designed to be smaller than the target. The upper ineffective layer is laminated on one of the laminates, and the capacity is measured after firing. From this measurement result, the remaining 29 electrodes are printed in a stacked manner on the remaining 29 bodies in an amount less than the target capacity, and the upper ineffective layer is stacked.

[0010]

However, in the above-mentioned conventional method for manufacturing a multilayer ceramic capacitor, the method of adjusting the capacitance of the multilayer ceramic capacitor in the case of adjusting the capacitance on the surface of the multilayer body as described in the above (1) is a method of adjusting the capacitance. It changes the appearance of the ceramic capacitor.
There was a problem in implementation.

In addition, in the case of adjusting the capacitance inside the laminate of (2), the lead time becomes longer and the process becomes complicated due to the increase of one manufacturing inspection step. The cost is high because a screen printing plate is required. Moreover, the dielectric green sheet used for the multilayer ceramic capacitor is thin (80 μm
In addition, there is a problem that the density is difficult to measure and the thickness after firing is difficult to predict due to the unevenness of the surface.

The present invention solves the above-mentioned conventional problems, and makes it possible to accurately design a capacitance without changing the shape of an external electrode and without providing an electrode for capacitance adjustment inside. The purpose of the present invention is to provide a method for manufacturing a laminated ceramic capacitor.

[0013]

In order to solve this problem, a method for manufacturing a multilayer ceramic capacitor according to the present invention comprises a firing method.
Dielectric powder per unit area of dielectric green sheet before forming
Powder and stacking multiple dielectric green sheets
Measure the density of the crimped material and determine the dielectric green after firing.
Measures the thickness of multiple sheets that have been laminated and crimped
The thickness of the dielectric green sheet after firing is
Laminate multiple powder weights and dielectric green sheets and crimp
Using the regression equation from the density of
A stacking cell that determines the overlapping area of the internal electrodes based on the results
This is a method of manufacturing a lamic capacitor .

[0014]

According to such a manufacturing method , firing is performed in advance.
Weight and density per unit area of previous dielectric green sheet
From, since it is possible to a dielectric green sheet thickness after firing a factor in dimensioning the process of the capacitive design simply by predicting accurately, it is possible to shorten and cost reduction of lead time.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be specifically described below.

First, raw material lots of the same characteristic material differ from each other.
40 μm thick dielectric green sheet, sheet No. 1,
Each of 2 and 3 is cut into a size of 160 mm × 140 mm. Then, apply this dielectric green sheet to Sheet No.
And 16 are pressure-bonded at a pressure of 600 kg / cm ² . 15mm in diameter from crimped dielectric green sheet block
Punch out five discs (hereinafter referred to as green discs).
This dielectric green sheet has a specific gravity of 4.5 g of the dielectric powder.
/ Cm ³ (90 wt%), binder 0.1 g / cm ³ (10 wt%)
%), The weight of the green disc and the molding of this
Since the weight of the dielectric powder used for
Of the green disk by measuring the weight of the green disk
Obtain the body powder weight, then measure the thickness of this green disk
Then, the unit area weight of the green disk and the green disk density are calculated by the following equations. At this time, an electronic balance (manufactured by Mettler) was used for the weight, and a flat micrometer was used for the thickness.

Green disk unit area weight (mg / cm ² ) =
Green disk weight (mg) / [disk area (1.767cm ² )
× number of sheets (16)] Green disk density (mg / cm ³ ) = green disk weight (m
g) / [Disc area (1.767 cm ² ) × Disc thickness (μm)] Place this green disc in a high-purity alumina sagger covered with ZrO ₂ powder, and at a temperature of 1350 ° C. in air. 2
Firing for a time to obtain a fired disk. Zr attached to this fired disk
O ₂ powder to drop sufficiently to determine the thickness at the point micrometer. The obtained green disk unit area weight, density and fired disk thickness are shown in (Table 1).

[0018]

[Table 1]

As is clear from Table 1 , if the unit area weight and the density of the green disk of the multilayer ceramic capacitor are known, the unit area weight of the green disk of Table 1 can be obtained.
Regression analysis to determine the thickness after firing using
There, it is possible to set the regression equation thickness after firing the dielectric green sheets (T) can be predicted accurately (regression equation) as follows.

Regression equation T = 16.695 + 2.915W
−6.233ρ where T: the thickness of the dielectric green sheet after firing (μ
m) , W: unit area weight of green disk (mg / cm ² ) ,
ρ: Density (g / cm ³ ) of the green disk.

Next, the dielectric green sheet ( 40 μm ) of the capacitance forming portion (hereinafter referred to as an effective layer) of the actually used multilayer ceramic capacitor was cut into a size of 500 mm × 140 mm, and the weight was measured. 6.455 g. The dielectric green sheet is 160 mm x 14 mm.
Cut into 0mm shape and laminated 16 sheets, pressure 600kg / cm
In crimped, where diameter punched green discs 15 mm, was weighed and the thickness, respectively 260.8Mg, 5
From this, the unit weight of the green disk can be calculated to be 9.224 mg / cm ² and the density can be calculated to be 2.674 g / cm ³ .

The result of the weight and density of the dielectric green sheet is used as a regression equation T = 16.6 for predicting the dielectric thickness.
95 + 2.915W-6.233ρ
Only (T) = 26.92 μm can be calculated.

In order to manufacture a multilayer ceramic capacitor of 18 pF using this 40 μm dielectric green sheet, the dielectric constant is 43 and the design of the two effective layers is the above equation.
Overlap of internal electrodes using C = ε · ε ₀ · S · N / T
An area of 0.636 mm ² is obtained. Therefore, this calculation result
Therefore, the area of the internal electrode overlapping with one dielectric layer
Dielectric green internal electrode so as to 0.636Mm ²
Print on a sheet and dry it.
Effective to express the capacitance by alternately stacking green sheets
Two layers, ceramic layers on the upper and lower surfaces, each being an ineffective layer
Nine layers of mic layers are laminated and pressed to form a laminate block
I do. The laminate block is cut into chips at a predetermined position at a cutting pitch of 2.24 mm in the length direction and 1.50 mm in the width direction, placed in a high-purity alumina sagger covered with ZrO ₂ , and heated in air. It was baked at 1350 ° C. for 2 hours.

Next, the edges were scraped with abrasive paper, silver paste for the external electrode was applied, and the chip was baked at a temperature of 850 ° C. to form an external electrode. Here, the capacitance was measured with a capacitance meter (manufactured by Yokogawa Hewlett-Packard Company).
A capacity of 8.16 pF was obtained.

This element is made of epoxy resin and has a diameter of 20 mm.
The chip body was polished with water abrasive paper so as to cover a column of mm, and the dielectric thickness of the effective layer portion was measured. As a result, it was 26.7 μm, and it was confirmed that the thickness was accurately predicted ( 26.92 μm ).

In this embodiment, in order to evaluate the weight of the dielectric powder of the dielectric green sheet, the weight of the green disk was measured.
Used, but also other sheet weight of specified length (500mm)
May be used for calculation. Also, regarding the thickness of the dielectric green sheet, it is natural that the prediction accuracy is improved by obtaining a regression equation for each thickness.

[0027]

As described above, according to the manufacturing method of the present invention, the capacitance can be designed without adjusting the capacitance. That is, the thickness of the dielectric, which is a design factor of the capacitor, is accurately predicted, and the process of designing the capacitor can be simplified, so that the lead time and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of a multilayer ceramic capacitor of an embodiment according to the present invention and a conventional example.

FIG. 2 is a cross-sectional view of the multilayer ceramic capacitor of FIG. 1 in a width direction.

[Explanation of symbols]

 1 Dielectric ceramic 2 Internal electrode 3 External electrode

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Mahito Omiya 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Katsuchi Tsuchimoto 1006 Kadoma Kadoma Kadoma City, Osaka Matsushita Electric Within Sangyo Co., Ltd. (72) Inventor Tatsuro Kikuchi 1006 Kadoma, Kazuma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Yasuo Tsuda 1006, Oaza Kadoma, Kadoma, Osaka Pref. Inventor Emiko Igaki 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Masakazu Tanahashi 1006 Kadoma Kadoma Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP 4-75311 (JP, A) JP-A-3-84993 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01G 4/00-4/40 H01G 13/00-13 / 06

Claims (1)

(57) [Claims] 1. A fired body at a high temperature of 1300 ° C. or higher after laminating a plurality of dielectric green sheets and internal electrodes alternately so that the internal electrodes alternately reach different ends. was ground so that the internal electrodes are exposed at the end portion, in the manufacturing method of a multilayer ceramic capacitor for forming the external electrode to the end, and dielectrics powder weight per unit area of the dielectric green sheet before the firing The density of a plurality of dielectric green sheets laminated and pressed is measured, and the thickness of a plurality of fired dielectric green sheets laminated and pressed is measured, and the fired dielectric green sheet is measured. The thickness of the dielectric powder and the dielectric
Of multiple green sheets laminated and pressed
And a method for manufacturing a multilayer ceramic capacitor, in which a prediction is made using a regression equation, and the overlapping area of the internal electrodes is determined based on the prediction result.