JPH01317153A - Production of calcined substance for producing inorganic dielectric powder - Google Patents

Abstract

PURPOSE:To improve a change both in dielectric constant of a multi-component substrate by temperature and in the dielectric constant and loss thereof by frequency and reduce cost by presubjecting raw material powder to specific treatment, calcining the resultant powder and quenching the calcined substance in obtaining the calcined substance for producing inorganic dielectric powder for manufacturing the substrate consisting of an inorganic dielectric powder and resin. CONSTITUTION:Raw material powder is calcined to provide a calcined substance for producing inorganic dielectric powder. In the process, powder prepared by preapplying a material for weakening bond of mutual powder in calcining to the surface is used as the above-mentioned raw material powder. After calcining, the resultant calcined substance is then quenched to a temperature below the Curie temperature. For example, fine ZrO2 powder, is cited as the substance for weakening the afore-mentioned bond. The above-mentioned substance as a granular substance 2 or layered substance 3 can be applied to the raw material powder 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a fired product for producing inorganic dielectric powder.

[Conventional technology]

As we enter the advanced information age, information transmission tends to become faster and more frequent. Mobile radios such as car telephones and personal radios, new media such as satellite broadcasting, satellite communications, and CATV are also at the stage of practical application.

On the other hand, in mobile radio and new media, devices are being made more compact, and along with this, there is a strong desire for miniaturization of microwave three-dimensional circuit elements such as dielectric resonators.

The size of the microwave three-dimensional circuit element is based on the wavelength of the electromagnetic waves used. The wavelength λ of an electromagnetic wave propagating in a dielectric material with relative permittivity εr is the propagation wavelength in vacuum. Then, λ−
λ. /εr0S. Therefore, the larger the dielectric constant of the circuit dielectric substrate used, the smaller the element becomes. Further, when the relative dielectric constant of the dielectric substrate is large, electromagnetic energy is concentrated within the substrate, which is advantageous in that leakage of electromagnetic waves is small.

A ceramic substrate is often used as the dielectric substrate. The most popular ceramic substrate is A1z.
It is an Os substrate. Although the relative dielectric constant is somewhat small (9, 8),
Larger than normal resin substrates.

However, with ceramic substrates, post-processing (drilling and cutting) is not easy, heat dissipation plates cannot be easily crimped, and it is difficult to increase the area. There is a drawback that it is low.

In order to solve these problems, a high dielectric constant (εr=50
Composite substrates using inorganic dielectric powders and resins having a particle size of 0 to 8,000) are being developed. This composite substrate is required to have a relative dielectric constant εrf)<moderately large (εr=about 10 to 30). This is because if the dielectric constant is too large, the required width of the circuit becomes too narrow, making it difficult to form the circuit. By mixing inorganic dielectric powder with a high relative permittivity with a resin, a suitably large relative permittivity εr can be obtained.

[Problem to be solved by the invention]

However, a composite substrate using an inorganic dielectric powder and a resin has large changes in relative permittivity with respect to temperature and changes in relative permittivity and dielectric loss with respect to frequency, and is not sufficiently stable.

Moreover, the inorganic dielectric powder used in composite substrates has the drawback of long manufacturing time and high cost. This is because it takes time to grind an inorganic fired product.In view of these circumstances, the present invention improves the relative permittivity of a composite substrate relative to temperature, and the relative permittivity and dielectric loss relative to frequency. An object of the present invention is to provide a method for producing a fired product that can produce inorganic dielectric powder in a short production time and at low cost.

[Means to solve the problem]

In the manufacturing method of the present invention, in order to obtain a fired product for producing an inorganic dielectric powder by firing a raw material powder, the raw material powder is a powder on which a substance that weakens the bond between the powders during firing is adhered in advance to the surface. In addition, after firing,
It is rapidly cooled to a temperature below the Curie temperature.

[For production]

The fired product remains a paraelectric material at high temperatures due to rapid cooling after firing. In a paraelectric material, the change in relative permittivity with respect to temperature and the change in relative permittivity and dielectric loss with respect to frequency are small.

On the other hand, in the fired product, a substance that weakens the bond between the powders is attached during firing at the required temperature, so the degree of sintering, that is, the degree of bonding is weak. Not only that, but the fired product becomes brittle due to rapid cooling, with cuts appearing in the sintered parts. Therefore, the time required for crushing can be shortened.

〔Example〕

Hereinafter, the present invention will be explained in detail based on examples thereof.

Calcined powder is usually used as the raw material powder. The dielectric powder is calcined in advance to form a dielectric powder with a certain composition.

For example, powders of TiOx and B a CO@ are mixed well in an equimolar ratio as starting materials to obtain a B a T i Ch composition, and the mixture is heated in an alumina crucible at a temperature of 1150°C under an air atmosphere. Obtain a calcined product. This is pulverized into a calcined powder by wet pulverization using a nylon pot and nylon coated steel balls. This calcined powder has a particle size in the range of, for example, about 0.5 to 5.0 μm. In addition, in the case of BaTi0, the composition is MgTioz, CaTi0i, Ba5 as so-called Debresosa.
ins, Fe, 02, etc. may be used in combination. However, when crushed, the depressosa effect tends to weaken.

Next, a raw material powder is prepared by attaching a substance to the surface of this calcined powder to weaken the bond between the powders during firing. This substance may be attached to the surface of the calcined powder 1 as granules 2, as shown in FIG. 1, or as a layered material 3, as shown in FIG. . Specifically, a process such as attaching ZrO2@ powder is performed.

Next, the raw material powder thus created is fired (main firing) to produce a fired product.

In the case of main firing, the firing temperature is usually 1200 to 1400.
℃ range. This is to cause the constituent crystals to grow to a certain extent so as to have predetermined dielectric properties.

When firing in the above temperature range, the powder of the fired product is usually strongly sintered, but in the fired product of the present invention, the sintering is weakened by the substances adhering to the surface.

After the raw materials are fired, they are rapidly cooled to lower the temperature from a certain level to below the Curie temperature. Rapid cooling is performed by dropping the raw material into distilled water. Usually, the quenching start temperature is slightly lower than the required firing temperature.

This is because the temperature of the high-temperature raw material drops before it is taken out of the crucible (calcination furnace) and dropped into water. If the temperature of the raw material is too low, even if it is rapidly cooled, a sufficient effect cannot be obtained. The quenching start temperature is usually preferably 700°C or higher.

Rapid cooling brings the crystal structure at high temperature to room temperature, making it a paraelectric material. In the case of 13 a T j Ox, the Curie temperature is 120°C. At temperatures above 12.0°C, it forms a cubic crystal, and this cubic crystal is brought to room temperature by rapid cooling.

Another specific method of rapid cooling is to leave it on a cold iron plate with a sufficiently large heat capacity.

The fired product is pulverized by, for example, wet pulverization using a nylon pot and a nylon-coated steel ball.

The powder particle size (average particle size) of this inorganic dielectric powder (ceramic dielectric powder) is usually 0.1 to 3
．． c+m (with particle size distribution of about 0.1 to 10 μm)
degree is preferred.

To make a composite board, resin (which may contain a crosslinking agent, etc.) and inorganic dielectric powder are mixed, a thin metal such as copper is layered as needed, and the mixture is heated and pressed.

In order to provide strength to the composite substrate, a base material such as glass cloth is impregnated with a mixture of resin and powder, and if necessary, a thin metal layer is laminated and molded under heat and pressure. for example,
Add 3 parts by volume of inorganic dielectric powder to 70 parts by volume of a resin solution containing PPO (polyphenylene oxide) resin and styrene as a polymerization crosslinking agent.
A glass cloth having a thickness of 100 μm is impregnated with a sufficiently mixed mixture of 0 parts by volume and dried. Five dried base materials and 35 μm thin copper were laminated on both sides and cured by heating and pressing at a temperature of 200°C to form a copper-clad composite board (thickness 0).
．． 8m1) completed. Of course, the copper thin film is used for forming a circuit, and the circuit is formed by a normal etching method or the like.

As mentioned above, during hot-press molding, depending on the type of resin and the type of inorganic dielectric powder, the inorganic dielectric powder may be heated again to above the Curie temperature and then cooled to room temperature. Even in this case, the powder does not change from paraelectric to ferroelectric. This is due to the compressive stress caused by the resin in the powder and the compressive stress generated on the powder surface due to rapid cooling.
It is assumed that this is because the inorganic dielectric powder remains as a paraelectric substance. Of course, in powder obtained by pulverizing a fired product that has been slowly cooled without rapid cooling, the ferroelectric material will not change to a paraelectric material due to resin stress or heating and cooling during molding. It is only through the rapid cooling of the present invention that the paraelectric state can be maintained and the temperature characteristics and frequency characteristics are improved.

Next, more specific examples and comparative examples from obtaining a fired product according to the present invention and from powdering to obtaining a composite substrate will be explained.

Example 1- Calcined powder (dielectric powder) was created as follows.

13 A mixture of T i Ot and B a COs powders were blended in an equimolar ratio as starting materials so as to have a T i Os composition, and the mixture was preliminarily calcined at a temperature of 1150°C in an alumina crucible. A calcined product was obtained.

This calcined product was powdered by wet pulverization using a nylon pot and a nylon coated steel ball, and the powder was 0.5 to 5 μm.
A calcined powder of m was obtained.

On the other hand, ZrOi fine particles (manufactured by Jujutsu Cement, particle size 0.007-0.01 μm) were mixed in distilled water (solid content 3%).
) and prepared a slurry.

Using a Raikai machine, this slurry was dropped little by little while stirring the previously calcined powder, and ZrOi (a substance that weakens the bond between powders during firing) was attached to the surface of the calcined powder to create a raw material powder.

The amount of slurry 1) dropped was such that the amount of Zr0z fine powder deposited after drying was 0.5 parts by weight per 100 parts by weight of the calcined powder.

After drying this raw material powder at 100°C, it was once ground in a Raikai machine, and then pulverized at 1350'C1 in a ZrCh crucible.
Main firing was performed for 3 hours, and then the product was poured into distilled water to be rapidly cooled to obtain a fired product.

This fired product was pulverized by wet pulverization using a nylon pot and nylon coated steel balls, and the average particle size was 1.7.
A μm-sized inorganic dielectric powder was obtained. The time required for crushing is approximately 1
It was 0 hours.

A mixture of 25 parts by volume of this powder and 75 parts by volume of PPO resin was made, set in a mold so that a 35 μm thick copper thin layer was laminated on both sides, and pressure-molded at a temperature of 230°C. A composite substrate was obtained by cooling the substrate to room temperature.

Example 2 - Example 1 except for the following differences in the preparation of the calcined product.
A composite substrate was obtained in the same manner.

B a o , 95P b o , o s T i
TiOx, BaCOs so as to have an O2 composition
and PbO powders and mixed well,
Temporary firing was carried out at a temperature of 1150° C. in a ZrO□ crucible in an air atmosphere.

Example 3 - Example 2 except for the following differences in the preparation of the fired product
A composite substrate was obtained in the same manner.

Instead of ZrO2 slurry, Zr alkoxide coating material (high purity chemical 8M Zr coating material) 8
A 1% solution was prepared by diluting the 1% solution with isopropyl alcohol, and poured into the calcined powder in a beaker to sufficiently wet the powder, and then filtered to remove and separate the excess coating liquid. In other words, the Zr coating material is a substance that weakens the bond between powders during firing.

Example 4 - Tetrafluoroethylene (fluororesin) instead of PPO resin
A composite substrate was obtained in the same manner as in Example 1, except that the 25 μm powder was used and direct pressure molding was performed at 350°C.

Example 5 - A composite substrate was obtained in the same manner as in Example 2, except that a 25 μm powder of tetrafluoroethylene was used instead of the PPO resin and direct pressure molding was performed at 350°C.

Example 6 - A composite substrate was obtained in the same manner as in Example 3, except that 25 μm powder of tetrafluoroethylene was used instead of PPO+1 fat and direct pressure molding was performed at 350°C.

- Comparative Example 1 - Example 2 except that the calcined powder obtained in Example 2 was subjected to main firing without attaching ZrO□ fine powder, and then the fired product was obtained by slow cooling instead of rapid cooling. A composite substrate was obtained in the same manner as in 2. The time required to crush the fired product was approximately 3
It was 6 hours.

-Comparative Example 2- A composite substrate was obtained in the same manner as in Comparative Example 1, except that 25 μm powder of tetrafluoroethylene was used instead of the PPO resin and direct pressure molding was performed at 350°C.

Regarding the composite substrates of Examples 1 to 6 and Comparative Example 1.2,
The relative permittivity εr and dielectric loss tanδ at IMHz and IGHz, and the rate of change in the relative permittivity εr at −20 to 80° C. (IMHz) were measured. The measurement results are shown in Table 1.

As shown in Table 1, in the examples, the relative dielectric constant and dielectric loss hardly change even if the frequency changes. -2
Even with a large temperature change of 0 to 80°C, the change in relative dielectric constant is about 3%, which is extremely small compared to 20% in the comparative example. In Example 1, where it is clearly seen that the frequency characteristics and temperature characteristics were significantly improved, the time required for pulverization was about 10 hours, but in Comparative Example 1, the pulverization time was about 36 hours, which is three times as long. It can be clearly seen that the effect of shortening the grinding time is large.

This invention is not limited to the first embodiment. It goes without saying that the composition of the fired product may be other than those exemplified above.

The pulverization of the fired product may also be performed using a vibration mill or a jet mill.

The resin in the composite substrate may be unsaturated polyester resin, epoxy resin, or the like. However, composite substrates using unsaturated polyester resin tend to have large dielectric loss.

〔Effect of the invention〕

As mentioned above, since the dielectric powder obtained by pulverizing the fired product obtained by the manufacturing method of the present invention is a paraelectric material, a composite substrate using this powder has different temperature characteristics and frequency characteristics of the dielectric constant, and The frequency characteristics of dielectric loss are improved. Moreover, the time required for pulverizing the fired product is shortened, the powder production time is short, and the powder cost is low.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are respectively schematic cross-sectional views of raw material powder used in the manufacturing method of the present invention. 1... Calcined powder 2.3... Substance agent that weakens the bond between powders during firing Patent attorney Takehiko Matsumoto

Claims (1)

[Claims] 1. When firing a raw material powder to obtain a fired product for producing an inorganic dielectric powder, the raw material powder is a powder on which a substance that weakens the bond between the powders during firing is attached in advance to the surface, and A method for producing a fired product for producing an inorganic dielectric powder, which comprises rapidly cooling the fired product to a temperature below the Curie temperature after firing.