KR100372689B1 - A method for manufacturing microwave dielectrics - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a microwave dielectric for use in a mobile communication device. The method for manufacturing a microwave dielectric, which is sintered at low temperature without degrading the characteristics of a microwave dielectric material by milling using a mechanochemical method after weighing and mixing a raw material. It is an object of the present invention to provide a method for manufacturing a microwave dielectric.

The present invention for achieving the above object, in the method for producing a microwave dielectric,

Weighing and premixing the microwave dielectric raw powder;

Milling and mixing the premix into a powder by milling; And

Sintering the powder; The milling is a technical subject of the method for producing a microwave dielectric, characterized by using mechanochemical milling (mechanochemical milling).

Description

A method of manufacturing a microwave dielectric {A METHOD FOR MANUFACTURING MICROWAVE DIELECTRICS}

The present invention relates to a method for manufacturing a microwave dielectric used in a mobile communication device, and more particularly, by mixing the microwave dielectric composition, and then milling by a mechanical chemical method, the manufacturing process can be shortened and the sintering temperature can be reduced. The present invention relates to a method for manufacturing a microwave dielectric.

In recent years, with the miniaturization and modularization of components due to miniaturization of mobile communication devices, both existing RF passive and active components have been stacked or modularized. In such RF modularization, a module that is simply built with only C or L and connected to a circuit inside a stack or by attaching an active element thereon is used, and has a low dielectric constant of 10 or less due to a problem of signal transmission speed. Glass ceramics having a dominant state is the situation (LTCC technology).

However, since chip stacking of passive components such as dielectric filters and duplexers in RF components is dependent on the length of the transmission line constituting the filter according to the design frequency, a material having a low dielectric constant such as the LTCC described above is used. The larger size eliminates the effect of chipping.

Thus, the implementation of such components necessitates a microwave dielectric material having essentially a constant level of dielectric constant and low dielectric loss.

On the other hand, in the manufacture of the conventional microwave dielectric glass frit was added for low temperature sintering, there was a problem that the microwave characteristics deteriorate. In addition to the addition of a separate sintering aid or glass frit for low temperature sintering, a method of sintering using ultrafine ceramic powder as a starting material, such as oxalate method, coprecipitation method, hydrothermal synthesis method and alkoxide method, has been tried. However, these methods have a problem in commercialization because the manufacturing process is complicated compared to the conventional oxide mixing method, the facility investment is high, and the starting material used is expensive.

Accordingly, the present inventors have repeatedly conducted research and experiments to solve the above problems and propose the present invention based on the results, and an object of the present invention is to measure and mix raw materials in a method of manufacturing a microwave dielectric. After milling by using a mechanical chemical method, to provide a method for producing a microwave dielectric that can be sintered at a low temperature without degrading the characteristics of the microwave dielectric material.

The present invention provides a method for producing a microwave dielectric,

Weighing and premixing the microwave dielectric raw powder;

Milling and mixing the premix into a powder by milling; And

Sintering the powder; The milling relates to a method for producing a microwave dielectric characterized by using mechanochemical milling.

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

The present invention relates to a method for producing a microwave dielectric comprising conventional weighing-milling and mixing-heat treatment-crushing-sintering of a raw material, and mechanochemical milling which can omit the processes such as milling and mixing, heat treatment and grinding. It is characterized by the application of the method to microwave dielectrics.

That is, conventional ceramics such as dielectrics and piezoelectric materials are weighed according to the composition ratio, placed in a container with water, mixed well, crushed to a certain size, taken out of a drying container, dried to be separated from a dryer, and then synthesized well. Forming into a lump of a certain shape as much as possible, heat-treating (calcination) at 900 ° C or more for 3 hours or more so that the desired single phase is 70% or more, pulverizing the hardened mass into fine powder And a step of sintering by adding a low temperature sintering aid such as glass frit. In this case, by selecting an appropriate low temperature sintering aid, it was possible to sinter at a temperature as low as 100 ° C to 200 ° C without deterioration of material properties.

However, in the case of microwave dielectrics, dielectric loss (Qf), which is the most important characteristic, changes rapidly depending on impurities or second phase, and especially when various sintering aids are added for low temperature sintering, regardless of the type and amount of sintering aids Since this leads to a drop, there is a problem in that not only the purity management of the starting raw materials but also the process management must be performed more thoroughly than other ceramic products.

Accordingly, the inventor of the present invention has studied a method capable of low-temperature sintering without incorporation of additives or impurities during sintering in the manufacture of microwave dielectrics. milling). In mechanochemical milling, powder milling and synthesis occur simultaneously by high speed milling. Conventionally, the use of the above-mentioned mechanochemical milling method in the production of microwave dielectrics has been avoided because the iron component is mixed by wear in the media (stainless ball) and the inner wall of the container (stainless steel) due to ultra-fast milling, which causes Qf to drop sharply. Because I thought. However, the inventors of the present invention, through many studies and experiments, found that the use of the mechanochemical milling method in the production of microwave dielectrics can lower the sintering temperature at the time of sintering without deteriorating other properties, and thus to complete the present invention. It is early.

On the other hand, the mechanochemical milling is composed of a pre-mixing step and a milling step that is pulverized and mixed. In the mechanochemical milling step, the powder is mixed (synthesized) as it is pulverized, thereby reducing the process to one step by mechanochemical milling in the conventional multi-step process of milling-mixing-heat treatment-milling. Prior to milling after the premixing step, the powder of the same composition is put together with the stainless steel balls in a stainless circular container and pulverized. The reason is to minimize the incorporation of iron components due to high-speed grinding by coating ceramic powder of the same composition on the inner wall of the container and the media. The mechanochemical synthesis is then carried out in a high speed shaker mill. The powder is pulverized more finely because it rotates at a high speed in the high speed shaker grinder, and calcination is simultaneously performed by heat by friction energy. That is, a large portion of the single phase is formed due to the high heat caused by the friction during mechanical milling. Therefore, conventional calcination and coarse pulverization-fine pulverization can be omitted. As described above, by using a shaker mill of a special dry method in the grinding of the mechanochemical milling process, an additional process such as drying is performed. It becomes unnecessary.

According to the above-mentioned mechanochemical milling, it is possible to make the particle size of the obtained powder into a fine particle of 10 nm or less at 1 micrometer conventionally. That is, since the particle size of the powder is 10 nm or less, the reactivity is increased during sintering, thereby lowering the sintering temperature by about 100 to 150 ° C.

For this reason, in the present invention, the sintering temperature during sintering after the mechanochemical milling can be lowered to 1100 ° C. without deteriorating other properties. That is, the sintering may be performed at a temperature range of 1100 to 1400 ° C. when manufacturing the microwave dielectric of the present invention. At this time, if the sintering temperature is less than 1100 ℃, there is a problem that the reaction is not made enough to micronize, if higher than 1400 ℃ can not obtain the desired microwave dielectric properties due to over sintering, there is a problem that the shape is easy to deform .

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

(Example)

As a starting material, a microwave dielectric composition having a composition of (Pb _0.4 Ca _0.6 ) (Fe _0.5 Ta _0.5 ) O ₃ was used and heat-treated at 1100 ° C. for 4 hours by a columbite method in order to enhance the synthesis effect. Thereafter, a microwave dielectric was prepared by applying different manufacturing methods to the starting materials as shown in Table 1 below. That is, in the case of the conventional examples (1) to (4) manufactured using the conventional oxide mixing method, the sintering aid shown in Table 1 at the time of sintering was used, and the invention example in which a mechanochemical synthesis method was introduced ( In the case of 1), it was synthesized by pulverization only without the special high temperature synthetic heat treatment process and the addition of sintering aid to make powder and sintered.

When prepared according to the method of the present invention, in order to enhance the mixing effect of the preliminary wet mixing for 6 hours using a stabilized zirconia ball of diameter 10mm and 5mm with ethyl alcohol as a solvent, transfer to a wide baht and then a dryer at 80 ℃ Dried within.

Then, prior to the mechanochemical grinding process, about 2 g of powder of the same composition was added to a stainless circular container having a diameter of 40 mm and a depth of 60 mm, together with 1 stainless steel ball and 1 mm of 5 mm and two 5 mm, and pulverized for about 6 hours and 60 hours at 500 rpm. During the mechanochemical grinding process.

As described above, the dielectric properties of each of the microwave dielectrics obtained by the conventional method and the present invention were investigated, and the results are shown in Table 1 below.

division Manufacture conditions Dielectric properties additive Sintering Temperature k Qf Conventional Example 1 ― 1250 63 9200 Conventional Example 2 Glass frit 1100 61 7500 Conventional Example 3 CuV ₂ O ₅ 1100 60 5600 Conventional Example 4 B ₂ O ₃ -Li ₂ O 1100 62 4000 Inventive Example ― 1100 62 9000 * Qf (= 1 / tanδ, Quality factor): Dielectric loss * k: Dielectric constant

As shown in Table 1 above, when the mechanochemical grinding of the present invention was performed and sintered at 1100 ° C., it was found that there was no significant difference in dielectric properties from the conventional example (1) sintered at 1250 ° C. using an oxide mixing method. Can be. In addition, it can be seen that the dielectric properties are much superior to those of the prior arts (2) to (4), which were sintered at 1100 ° C. for 3 hours by adding an additive such as glass frit to the powder made by the conventional oxide mixing method. That is, in Table 1, Qf and k, which show dielectric properties, have an inverse relationship with each other. When the dielectric constant k is large, the dielectric loss increases and the Qf value decreases. It turns out that Qf value is also excellent while being above.

As described above, according to the present invention, the powder manufacturing process is shortened, the cost is reduced, the fine powder is produced, and the sintering temperature can be lowered by about 150 ° C. In addition, by producing a microwave dielectric without incorporation of impurities and additives, excellent material properties can be obtained.

Claims (3)

In the method of manufacturing a microwave dielectric, Weighing and premixing the microwave dielectric raw powder; Milling and mixing the premix into a powder by milling; And Sintering the powder; The milling method of producing a microwave dielectric, characterized in that by using mechanochemical milling (mechanochemical milling) The method of claim 1, wherein the particle size of the powder after mechanochemical milling is 10 nm or less. The method of claim 1, wherein the sintering after the mechanochemical milling is performed at a temperature range of 1100 to 1400 ° C. 6.