JPH03148106A - Manufacture of capacitor - Google Patents

Abstract

PURPOSE:To easily manufacture capacitors having different permittivities by coating the surface of a ceramic molded form with metal oxide containing at lest one of Sr and Ti or/and at least one of Al, Si and Mg, and then conducting a predetermined step such as a baking step, etc. CONSTITUTION:When a ceramic molded form 1 is coated with metal oxide pastes 2a, 2b containing Sr or Ti and then baked, the Sr or Ti controls growth of crystal grains. Al, Si or Mg has an operation as a valence compensator. When the form 1 is coated with metal oxide pastes 2a, 2b containing Al, Si or Mg and then baked, the Al, Si or Mg controls growth of crystal grains. Thus, capacitors having different permittivity and made of the same ceramic material can be manufactured by altering the contents of the Sr, Ti, Al, Si, Mg.

Description

[Detailed description of the invention] Child! Uabe ■ Satokai black The present invention relates to a method for manufacturing a capacitor.

A semiconductor ceramic in which an insulating layer is formed at the armor-type Ω-limb stray grain boundaries is −
It has a large dielectric constant at m9. If such a semiconductor ceramic is used, a capacitor with a large capacity can be obtained.

FIG. 2 shows a cross-sectional view of this type of capacitor, in which a pair of upper and lower electrodes 52a and 52b are formed on both the front and back surfaces of a grain boundary insulated ceramic substrate 51.

As a ceramic raw material constituting the ceramic substrate 51, a material containing barium titanate (BaTiO, 1 as a main component) has been widely used.

However, although this capacitor mainly composed of B a Ti Os has a large dielectric constant of 20,000 to 70,000, it has a large dielectric loss of 5 to 6% (IKHz).
Furthermore, when the temperature change rate of capacitance is based on 20°C, there is a drawback that it shows a large value of ±50% in the range of -25°C to +85°C.

Therefore, in recent years, capacitors containing strontium titanate (SrTiO-) as a main component have been developed in an attempt to improve dielectric properties such as dielectric loss and temperature change rate of capacitance.

The ceramic capacitor whose main component is S r Ti Oa has a dielectric loss of 1% or less, and a temperature change rate of capacitance of -25 to +8 when 20°C is the standard.
It is within ±15% in the range of 5°C.

Further, the 5rTiOs capacitor has a crystal grain size of 5
0 μm = 100 μm, and the dielectric constant increases approximately in proportion to the average crystal grain size, so it is 50.000 to 120.0
A capacitor having a high dielectric constant of about 0.00 is obtained.

Conventionally, the grain boundary insulation type ceramic capacitor mentioned above is
It was manufactured according to the process shown in the figure.

That is, after a ceramic raw material containing a semiconducting agent is subjected to a predetermined shaping process to produce a compact (■), the compact is subjected to primary firing in a reducing atmosphere to produce a sintered compact (IT ). Next, after applying a metal oxide as an additive to the surface of the sintered body (III), heat treatment is performed in the air and secondary firing), and a ceramic substrate is produced (TV).
. Through this heat treatment, the additive penetrates into the interior of the semiconductor ceramic, and the grain boundaries are insulated. In other words,
While the crystal grains maintain their semiconductor state, only the grain boundary layer portions are vertically and horizontally connected to become an insulator.

Finally, a pair of upper and lower electrodes is formed on both the front and back sides of the ceramic substrate by screen printing or the like (V), completing the production of the ceramic capacitor.

Lesson 1: However, in the conventional capacitors mentioned above, their dielectric properties (permittivity, dielectric loss, insulation resistivity, rate of change of capacitance with temperature, etc.) largely depend on the ceramic raw material.
There was a problem in that as long as the same ceramic raw material was used, it was not possible to manufacture capacitors with significantly different dielectric constants.

In view of these problems, an object of the present invention is to provide a capacitor manufacturing method that allows capacitors with significantly different dielectric constants to be manufactured even when the same ceramic raw material is used.

In order to achieve the above object, the method for manufacturing a capacitor according to the present invention includes at least one component among Sr and Ti, and/or at least one component among Al1, Si, and Mg. a step of applying a metal oxide paste containing the component to the surface of a ceramic molded body containing a semiconducting agent; and a step of firing the ceramic molded body coated with the metal oxide paste to obtain a sintered body. , forming an electrode on the sintered body.

It is known that when a metal-containing oxide paste containing Sr or Ti is applied to a ceramic molded body and then fired, the Sr or Ti acts to control the growth of crystal grains.

Moreover, AC31 or Mg has an action as a valence compensator, and when a metal oxide paste containing Aρ, Si or Mg is applied to the ceramic molded body and then fired, the above-mentioned It is known that AI2, Si or Mg suppresses the growth of crystal grains.

Therefore, according to the above manufacturing method, a ceramic molded body containing a semiconducting agent is made of a metal oxide paste containing at least one component among Sr and Ti and/or at least one component among Al, Si, and Mg. Since it includes a step of coating on the surface of Sr, Ti, A1
1. By changing the content of Si and Mg, capacitors with significantly different dielectric constants can be manufactured even if the ceramic raw materials are the same.

Consolidation Hereinafter, embodiments of the present invention will be explained in detail based on the drawings.

FIG. 1 is a process diagram showing a method of manufacturing a grain boundary insulated capacitor as an embodiment of the present invention.

That is, first, as shown in FIG. 1(I), a ceramic molded body 1 is manufactured.

Valence control agents that contribute to semiconducting ceramic raw materials (e.g. La, Dy, Nd, Y, Nb, Ta, Er, Gd,
oxides such as Ho, Ce) and sintering aids (Cu, Mn, etc.) that act to improve and stabilize the properties of ceramics.
After mixing a predetermined ceramic raw material with oxides such as oxides, etc., a sheet-shaped molded body is manufactured by press molding or extrusion molding.

Next, this sheet-like molded body is pressed into a predetermined shape using a mold press.

Here, as the ceramic raw material, a composite oxide having a perovskite crystal structure (-Toshiki RMOa), for example, BaTiOa, SrTiO3, (Ba, 5r)
(Ti, 5n)Os-based composite oxide (including solid solution), (
Ba, 5r) Ties-based composite oxide (including solid solution),
(Mg, Sr, Ca) TiOa-based composite oxide (including solid solution).

(Sr, Pb) Tie3 complex oxide (including solid solution)
, (Sr, Ca) Ties-based composite oxide (including solid solution), or the like is used.

Next, as shown in FIG. 1 (II), metal oxide pastes 2a and 2b are applied to both the front and back surfaces of the ceramic molded body 1.

As the metal oxide pastes 2a and 2b, those containing at least one component among Sr and Ti, and/or those containing at least one component among AI2, Si, and Mg are used.

Next, this is subjected to secondary firing to produce a sintered body 3 as shown in FIG. 1 (Ill).

That is, the ceramic molded body coated with the metal oxide pastes 2a and 2b was placed in a reducing atmosphere (H21-15V).
o1%, N299-85vo1%), 1400
Firing was performed at a temperature of ~1540°C for 4 to 6 hours, and the sintered body 3
Create. Then, the metal oxide paste 2a, 2
Due to the difference in the composition of b, sintered bodies 3 with different growth of crystal grains are produced during the second firing process.

That is, in the sintered body 3 obtained by applying Sr and Ti to the ceramic molded body 1 and firing it, the growth of the crystal grains is controlled. In other words, when using perovskite crystal structure RMO3 as a ceramic raw material, Sr and Ti
is A/B (A is metal ion R (Sr, Ca, Pb,
The number of atoms of Ba, Mg, etc.), B is the metal ion M (Ti, etc.)
Sr and T
By changing the composition ratio of the metal oxide containing i, the growth of crystal grains in the sintered body 3 can be appropriately controlled. Therefore, even if the ceramic raw materials are the same, it is possible to obtain capacitors with significantly different dielectric constants.

In addition, when a metal oxide containing Al, Si or Mg is contained in the ceramic molding weight, these AI2, Si
Alternatively, Mg acts as a valence compensator. That is, the ceramic molded body 1 contains a valence control agent (semiconducting agent)
However, when the ceramic molded body 1 contains a valence compensator, the growth of crystal grains is suppressed, and the ceramic molded body 1 is made into an insulator without being made into a semiconductor. Therefore, it is possible to obtain a capacitor with a low dielectric constant even if the ceramic raw materials are the same.

Next, as shown in FIG. 1 (TV), a metal oxide (for example, B i 20s
, Cub, Na2O, MnO2, Tl220. , Pb
O, Na2O5, ZnO, etc.).

This additive 4 is added in order to smoothly form an insulating layer at grain boundaries to obtain a ceramic capacitor having desired dielectric properties.

Next, as shown in FIG. 1(V), this is subjected to secondary firing to produce the ceramic substrate 5. 6 The secondary firing is performed in the atmosphere.
Heat treatment is performed in a temperature range of 1000 to 1300°C.

By this secondary firing, the additive 4 is diffused between the crystal grains in the sintered body 3, the grain boundaries are insulated, and a grain boundary insulating layer is formed.

Finally, a conductive metal paste is applied to both the front and back surfaces of the ceramic substrate 5 by screen printing, and then baked to form the electrodes 6a, as shown in FIG. 1 (Vl).
6b is formed to complete the production of the ceramic capacitor.

Here, as the metal paste, one containing at least one of Ag, Au, Zn, or Ni is used. However, in consideration of electrical characteristics etc., it is most desirable to use Ag. Further, the metal paste is baked in the atmosphere at a temperature of 700 to 900°C.

A specific example of manufacturing a (Sr, Ca) Tie 3 ceramic capacitor will be described below.

Mix ceramic raw materials to a predetermined composition ratio.

That is, T i O2, SrO as ceramic raw materials
, CaO is used as the main component, and its composition ratio is TiCh.
50.0-52.0 mo1%, 5rO40.0-5
0.0mo1%, Ca0O~10. It was blended so that the Omo content was 1%. Specifically, (Sr, Ca)T i O
In three types of ceramic raw materials, A/B = 0.994 ~
0.998 (A is the number of atoms of Sr ion or/and Ca ion, B is the number of atoms of Ti ion) 6 Next, Nb2O5, Y2O5, etc. were added to the ceramic raw material as a valence control agent. .1 to 0.5 mo1%, and 0.05 to 0.1% of CuO1M n 02 as a sintering aid.
After mixing approximately 1% by mole of 4 mo, these were kneaded together with a binder, water, and a dispersant. Thereafter, a sheet-like ceramic molded body was produced by press molding or extrusion molding.

Thereafter, the sheet-like ceramic molded body was pressed using a mold press to produce a ceramic molded body 1 having a predetermined shape.

Next, containing at least one component of Sr, Ti, or/and Al2. Metal oxide pastes 2a and 2b containing at least one component of Si and Mg
were prepared in a predetermined composition ratio and applied to both the front and back surfaces of the ceramic molded body I. Specifically, in this example, as the metal oxide pastes 2a and 2b, S r CO3, T
i02, Al210a, 5iOi, MgO,M
The metal oxide pastes 2a and 2b prepared using nCO3 at a predetermined composition ratio were applied to both the front and back surfaces of the ceramic molded body I.

1 2 After this, the ceramic molded body l coated with the metal oxide pastes 2a and 2b is placed in a reducing atmosphere (Hz:
1-l 5 vo1%, Na: 85-99 vol
%) at a temperature of 1400 to 1540° C. for 4 to 6 hours to produce a sintered body 3.

After this secondary firing, when the cross section of the sintered body 3 was observed with an SEM, it was found that the crystal grain size varied in the range of 2 μm to 200 μm due to the difference in the composition ratio of the metal oxides 2a and 2b.
It was confirmed that the growth states of crystal grains were different.

Next, add B z z Oa, Cub, Nag O to this.
After applying a mixed paste (additive 4), secondary firing was performed to produce a ceramic substrate 5. The conditions for this secondary firing are a temperature of 1000 to 1300°C and a firing time of approximately 1.
It's time. By this secondary firing, ions of the additive component diffuse between the crystal grains in the sintered body 3, thereby insulating the grain boundaries and forming a grain boundary insulating layer.

Next, a conductive metal paste, specifically an Ag paste, was applied to both the front and back surfaces of the ceramic substrate 5, and then baked to form electrodes 6a and 6b, thereby manufacturing a ceramic capacitor. Incidentally, the baking was performed in the air at a temperature of 700 to 900°C.

Table 1 shows the dielectric properties (permittivity, dielectric loss, temperature change rate of capacitance, variation in capacitance) when ceramic capacitors are formed with various composition ratios of metal oxides 2a and 2b. Conventional example where no material is coated (Fig. 2)
This is shown together with Here, the dielectric constant ε and the dielectric loss tan δ (%) were determined from values measured under an alternating current voltage of 1 kHz and 1 V. In addition, the insulation resistivity ρ is the DC voltage 25
It was determined from the current value after applying V for 1 minute. Furthermore, the capacitance temperature change rate (C%) is determined by measuring the capacitance when cooled to -25°C and when heated to +85°C.
It was calculated from the difference between the capacitance and the capacitance at ℃.

4 No, 1=No, 10 is metal oxide, 5
Contains rCO- and T i O2 in equal mo1%, and Aj! 203, SiO□, shows cases where the content of MnCO3 is varied, No. 11 to No. 15 are metal oxide pastes,
S r CO3, T i O2, Aρ20x, respectively
, 5iOz, shows the case where only MgO is used, No. 16 to No. 21 are metal oxide pastes,
AA203.5in2. The case is shown using a mixture of MgO1M n COs.

Moreover, No. 22 is a conventional example (see FIG. 3),
A case is shown in which the metal oxides 2a and 2b are not applied to the ceramic molded body 1.

As is clear from this Table 1, (Sr,Ca)TiO
In a-type ceramic capacitors, the dielectric constant ε is 350.
Capacitors with significantly different dielectric constants in the range ˜79,000 can be obtained.

In addition, it contains S r COz and T i 02 at equal mo1%, Aj2a O3, S i 02 , MnCO3
When the content of (No, 1 to No.

10) It was found that the dielectric constant ε increases as the contents of SrCO3 and T i O□ are increased and as the amounts of Ag2O, SiO□, and M n CO3 added are decreased.

In addition, dielectric properties such as dielectric loss, insulation resistivity, and rate of change in capacitance with temperature can be sufficiently satisfied, and the intended purpose can be achieved.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and can be modified without departing from the spirit of the invention. Furthermore, ceramic raw materials are not limited to (Sr, Ca)TiOx type materials, but include BaTi0. The intended purpose of the present invention can also be achieved using l-based and other ceramic raw materials.

older brother! As detailed above, in the method for manufacturing a capacitor according to the present invention, a small amount of Sr and Ti, which control the growth of crystal grains (both are one type or/and which suppresses the growth of crystal grains), is used to control the growth of crystal grains. After applying a metal oxide containing at least one of Al1, Si, and Mg to the surface of a ceramic molded body, a capacitor is manufactured through a predetermined process such as a firing process, so the process of applying the metal oxide is added. By simply doing this, capacitors with significantly different dielectric constants can be manufactured simply and easily without impairing dielectric properties such as dielectric loss.Therefore, even when using the same ceramic raw material, it can be applied to various applications. Capacitors with widely different possible dielectric constants can be easily manufactured.

[Brief explanation of the drawing]

FIG. 1 is a manufacturing process diagram showing an example of the method for manufacturing a capacitor according to the present invention, FIG. 2 is a cross-sectional view showing a conventional grain boundary insulated capacitor, and FIG. 3 is a diagram showing a conventional method for manufacturing a capacitor. It is a process diagram. 2a, 2b...Metal oxide paste, 3...Sintered body, 4...Additive, 6a, 6b...Electrode. 8 (m) (V) Figure 2 Figure 3 (1) (n) /m)

Claims (1)

[Claims] (1) At least one component among Sr and Ti or/
and a step of applying a metal oxide paste containing at least one component among Al, Si, and Mg to the surface of a ceramic molded body containing a semiconducting agent; and the ceramic molded body coated with the metal oxide paste. A method for producing a capacitor, the method comprising the steps of: obtaining a sintered body by firing the sintered body; and forming an electrode on the sintered body.