JP2023049306A - Glass ceramic dielectric material, sintered body, method for producing sintered body and circuit member for high frequency - Google Patents

Abstract

To provide a glass ceramic dielectric material having low dielectric loss tangent and high flexural strength in a high frequency region of 20 GHz or more, a sintered body and a circuit member for high frequency.SOLUTION: A laminated glass ceramic dielectric material has a laminated structure in which at least an outer layer, an inner layer, and an outer layer are laminated in this order, each of the outer layers comprising alumina with a thickness of 0.1-5 μm, and the inner layer comprising crystalline glass powder that comprises, as a glass composition, in mass%, SiO2 50-60%, CaO 20-30%, and MgO 15-21%.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a glass-ceramic dielectric material, a sintered body, and a high-frequency circuit member, which are precursors of a sintered body having a low dielectric loss tangent and high mechanical strength that are advantageous for signal processing in a high-frequency region of 20 GHz or higher.

Alumina ceramics are widely used as wiring boards and circuit parts. Alumina ceramic has a high relative permittivity of 10, so it has the disadvantage of slow signal processing. In addition, since tungsten with a high melting point must be used as the conductor material, there is also the drawback that the conductor loss increases.

In order to compensate for the drawback, a glass-ceramic dielectric material composed of glass powder and ceramic powder has been developed, and its sintered body is used as a dielectric layer. For example, a sintered body of a glass-ceramic dielectric material using a glass powder in which diopside precipitates as a main crystal has a dielectric constant of 7.3 to 7.8 at 0.1 GHz, which is higher than that of an alumina ceramic material. lower than In addition, since it can be fired at a temperature of 1000° C. or less, it can be fired simultaneously with low melting point metal materials such as Ag and Cu, which have low conductor loss, and have the advantage that these can be used as inner layer conductors (Patent document 1).

JP-A-10-120436

By the way, in recent years, in the field of local network communication such as mobile communication equipment represented by 5G and WiFi, the frequency band used has increased to 20 GHz or higher. There is a strong demand for further reduction in dielectric loss tangent.

The transmission loss of electromagnetic waves in electronic circuits is proportional to the product of the square root of the dielectric constant of the circuit board, the dielectric loss tangent, and the frequency of the electromagnetic waves. The glass-ceramic dielectric materials disclosed in the above-mentioned patent documents exhibit high dielectric properties at 10.1 GHz, but the dielectric loss tangent is not sufficiently low in the high frequency region of 20 GHz or higher, resulting in a problem of increased transmission loss. rice field.

Moreover, there is a problem that the bending strength is as low as about 200 MPa, and the strength is insufficient for use as a high-frequency circuit board.

An object of the present invention is to provide a glass-ceramic dielectric material that is a precursor of a sintered body having a low dielectric loss tangent and high bending strength in a high frequency region of 20 GHz or higher, a sintered body, and a high frequency circuit member. be.

The laminated glass-ceramic dielectric material of the present invention has a laminated structure in which at least an outer layer, an inner layer, and an outer layer are laminated in this order, each of the outer layers is made of alumina with a thickness of 0.1 to 5 μm, and the inner layer is glass. The composition is characterized by containing crystallizable glass powder containing SiO ₂ 50-60%, CaO 20-30%, and MgO 15-21% by mass %.

In the present invention, "crystalline glass powder" means amorphous glass powder having the property of precipitating crystals from the glass matrix upon heat treatment. “Heat treatment” means heat treatment at 800 to 1000° C. for 10 minutes or longer.

In the laminated glass-ceramic dielectric material of the present invention, the inner layer is preferably a green sheet compact or printed laminate.

Preferably, in the laminated glass-ceramic dielectric material of the present invention, the inner layer is substantially free of ceramic powder. "Substantially free of ceramic powder" means that the content of ceramic powder in the inner layer is less than 0.1% by mass.

The laminated glass-ceramic dielectric material of the present invention preferably contains a metal conductor in said inner layer.

In the laminated glass-ceramic dielectric material of the present invention, the metal conductor is preferably silver or a silver alloy.

The sintered body of the present invention is a sintered body obtained by sintering the laminated glass-ceramic dielectric material described above, and it is preferable that diopside-based crystals are precipitated as main crystals from the glass matrix of the inner layer. The term “diopside-based crystal” refers to a diopside crystal (diopside, CaMg(Si ₂ O ₆ )) and a diopside solid solution crystal.

The sintered body of the present invention has a laminated structure in which at least an outer layer, an inner layer, and an outer layer are laminated in this order, each of the outer layers is made of alumina having a thickness of 0.1 to 5 μm, and the inner layer contains, by mass%, It contains 50 to 60% SiO ₂ , 20 to 30% CaO, and 15 to 21% MgO, and is characterized by the precipitation of diopside crystals.

The sintered body of the present invention preferably has a three-point bending strength of 250 MPa or more. In addition, "three-point bending strength" refers to a value evaluated based on JIS R1601.

The sintered body of the present invention preferably has a dielectric loss tangent of 0.0009 or less at a measurement temperature of 25° C. and 28 GHz.

The sintered body of the present invention preferably has a dielectric constant of 8.0 or less at a measurement temperature of 25° C. and 28 GHz.

“Dielectric loss tangent” and “relative permittivity” refer to values measured at a measurement temperature of 25° C. and a frequency of 28 GHz based on the method for measuring microwave dielectric properties of fine ceramics substrates (JIS R1641).

The sintered body of the present invention preferably has a coefficient of thermal expansion of 8 to 10 ppm/°C. "Thermal expansion coefficient" refers to a value measured with a thermomechanical analyzer within a temperature range of 30 to 380°C.

In the method for producing a sintered body of the present invention, it is preferable to sinter the laminated glass-ceramic dielectric material.

In the method for producing a sintered body of the present invention, firing is preferably performed at a temperature of 1000° C. or less.

The high-frequency circuit member of the present invention is a high-frequency circuit member having a dielectric layer, and the dielectric layer is preferably the sintered body described above.

The laminated glass-ceramic dielectric material of the present invention can be fired at a low temperature of 1000° C. or less, and a low-melting metal material such as silver, silver alloy, or copper can be used as the inner layer conductor. Furthermore, it has a low dielectric loss tangent in a high frequency region of 20 GHz or higher, and a high bending strength of 250 MPa or higher. Therefore, the glass-ceramic dielectric material of the present invention is suitable as a high-frequency circuit member to be mounted on a resin motherboard.

The laminated glass-ceramic dielectric material of the present invention is a laminate in which an outer layer, an inner layer, and an outer layer are laminated in this order, the inner layer containing crystallizable glass powder, and the outer layer consisting of alumina.

First, the inner layer will be explained.

The glass powder constituting the inner layer preferably contains 50 to 60% by mass of SiO ₂ , 20 to 30% by mass of CaO, and 15 to 21% by mass of MgO as the glass composition. The reason why the content range of each component is limited as described above will be described below. In addition, in description of the content range of each component, % notation refers to the mass %.

SiO ₂ is a constituent component of diopside crystals and a component that becomes a network former of glass. The content of SiO ₂ is 50-60%, preferably 53-57%, in particular 54-56%. If the _SiO2 content is too low, vitrification becomes difficult. On the other hand, if the SiO ₂ content is too high, the melting temperature tends to be high, and diopside crystals are less likely to precipitate.

CaO is a constituent component of diopside-based crystals, and is a component that lowers the softening point of the crystallizable glass powder. The content of CaO is 20-30%, preferably 23-29%, particularly 25-27%. If the CaO content is too low, the softening point will be too high. In addition, the degree of crystallinity is lowered, and the dielectric loss tangent tends to increase. On the other hand, when the CaO content is too high, vitrification becomes difficult. Also, the dielectric loss tangent tends to increase.

MgO is a constituent component of diopside-based crystals, and is a component that lowers the softening point of the crystallizable glass powder. The content of MgO is 15-21%, preferably 17-20%. If the MgO content is too low, the softening point will be too high. Also, the dielectric loss tangent tends to increase. On the other hand, when the content of MgO is too high, vitrification becomes difficult. In addition, the degree of crystallinity is lowered, and the dielectric loss tangent tends to increase.

In addition to the above components, components such as Al ₂ O ₃ , B ₂ O ₃ and ZnO may be added up to 3% each within a range that does not impair the dielectric properties.

Alkali metal oxides (Li ₂ O, Na ₂ O, K ₂ O) are components that lower the firing temperature but increase the dielectric loss tangent. Therefore, the content of Li ₂ O+Na ₂ O+K ₂ O is less than 2%, preferably less than 1%, less than 0.5%, especially less than 0.1%. The Li ₂ O content is preferably less than 0.5%, particularly less than 0.1%. The content of Na ₂ O is preferably less than 0.5%, especially less than 0.1%. The content of K ₂ O is preferably less than 0.5%, especially less than 0.1%. Here, " _Li2O + _Na2O + _K2O " means the total amount of _Li2O , _Na2O and _K2O .

Preferably, the inner layer is a green sheet compact or printed laminate.

If the inner layer contains ceramic powder, the dielectric properties and/or strength can be improved, but the densification of the sintered body may be hindered. Therefore, it is preferred that the inner layer of the present invention is substantially free of ceramic powder.

Since the laminated glass-ceramic dielectric material of the present invention can be fired at 1000° C. or less, a metal conductor with a low melting point can be introduced into the inner layer. The metal conductor is preferably silver or a silver alloy with low conductor loss.

In addition, when fired, it is preferable that diopside-based crystals precipitate as main crystals from the crystallizable glass powder contained in the inner layer. Precipitating diopside-based crystals in the inner layer facilitates lowering the dielectric constant and dielectric loss tangent.

The inner layer preferably has a thickness of 0.1 to 3.0 mm.

Next, the outer layer will be explained.

The outer layer consists of alumina. Alumina has high strength and has a coefficient of thermal expansion of 7 to 7.7 ppm/° C., which is close to that of the high-expansion inner layer. Therefore, it is suitable for increasing the mechanical strength of the glass-ceramic dielectric material of the present invention. .

Also, the outer layer is preferably formed on the surface of the inner layer with a thickness of 0.1 to 5 μm, particularly 0.3 to 4 μm. If the outer layer is too thin, the mechanical strength tends to decrease. On the other hand, if the outer layer is too thick, the outer layer may peel off.

Next, the characteristics of the sintered body of the present invention are described below.

The sintered body of the present invention preferably has a three-point bending strength of 250 MPa or more, particularly 260 MPa or more. If the three-point bending strength is too low, the sintered body is likely to crack or the like. Although the lower limit of the three-point bending strength is not particularly limited, it is practically 100 MPa or more.

The sintered body of the present invention preferably has a dielectric loss tangent of 0.0009 or less, particularly 0.0008 or less at 25° C. and 28 GHz. If the dielectric loss tangent is too high, transmission signal loss tends to increase. Although the lower limit of the dielectric loss tangent is not particularly limited, it is practically 0.0001 or more.

The sintered body of the present invention preferably has a dielectric constant of 8.0 or less, particularly 7.5 or less at 25° C. and 28 GHz. If the dielectric constant is too high, the speed of signal processing tends to slow down. Although the lower limit of the dielectric constant is not particularly limited, it is practically 5.0 or more.

The sintered body of the present invention preferably has a thermal expansion coefficient of 8 to 10 ppm/°C, particularly 8.5 to 9 ppm/°C. If the coefficient of thermal expansion of the sintered body is too low, distortion is likely to occur due to the difference in thermal expansion when the sintered body is soldered to a resin mother board and then subjected to a heat cycle. On the other hand, if the coefficient of thermal expansion is too high, the thermal shock resistance is lowered. The "thermal expansion coefficient" is measured in a temperature range of 30 to 380°C with a thermomechanical analyzer.

Furthermore, the method for producing the sintered body of the present invention will be described below.

First, predetermined amounts of a binder, a plasticizer and a solvent are added to the crystallizable glass powder to prepare a slurry. Suitable binders include, for example, polyvinyl butyral resin and methacrylic acid resin, suitable plasticizers include dibutyl phthalate, and suitable solvents include toluene and methyl ethyl ketone.

Next, the slurry of the crystalline glass powder is formed into a green sheet by a doctor blade method, dried, cut into a predetermined size, and mechanically processed to form a via hole. A low-resistance metal material that will serve as an electrode is printed on the via hole and the surface of the green sheet. Then, a plurality of such green sheets are laminated to obtain a laminated green sheet.

Furthermore, a sintered body can be obtained by dip-coating the laminated green sheet with an alumina slurry to form a uniform alumina layer and then firing the same. The alumina layer may be formed by firing the laminated green sheet, printing alumina paste on the surface, and firing again. Also, the thickness of the alumina layer can be changed by adjusting the paste viscosity.

The sintered body thus produced can be provided with a conductor or an electrode inside or on the surface. From the viewpoint of using low-melting metal materials such as silver and copper with low conductor loss, the firing temperature is desirably 1000.degree.

The high-frequency circuit member of the present invention can be produced by forming a coil with wiring or by connecting a chip of a Si-based or GaAs-based semiconductor element on the surface of the sintered body produced as described above. can be done.

EXAMPLES The present invention will be described below based on examples, but the present invention is not limited to these examples.

Table 1 shows examples of the present invention (samples Nos. 1 to 4) and comparative examples (samples Nos. 5 and 6).

Each sample was produced as follows. First, glass raw materials of various oxides were prepared so as to have the glass composition shown in the table, mixed uniformly, then placed in a platinum crucible and melted at 1500 to 1580° C. for 3 hours, and the molten glass was cooled with a water-cooled roller. It was molded into a thin plate. Next, after crushing the resulting glass film, alcohol was added, wet pulverization was performed with a ball mill, and classification was performed so that the average particle size was 1.5 to 3 μm to obtain glass powder.

Next, 15% by mass of polyvinyl butyral as a binder, 4% by mass of butylbenzyl phthalate as a plasticizer, and 30% by mass of toluene as a solvent were added to the above glass powder to prepare a slurry. Next, the above slurry was formed into a green sheet of 150 μm by a doctor blade method, dried, and cut into a predetermined size, and then four green sheets were laminated and integrated by thermocompression bonding. Further, the laminated green sheet, which was dip-coated with an alumina slurry to form a uniform alumina layer on the surface thereof, was fired at 900° C. for 1 hour to obtain a glass ceramic.

Each sample thus obtained was evaluated for firing temperature, possibility of co-firing with silver, deposited crystals, three-point bending strength, dielectric loss tangent, dielectric constant, and coefficient of thermal expansion. Table 1 shows the results.

The firing temperature is the lowest temperature at which ink is wiped off after applying ink to a sintered body fired at various temperatures (that is, densely sintered).

Whether or not silver co-firing was possible was determined by printing a silver conductor on a green sheet before firing, co-firing the green sheet, and visually inspecting whether there was any discoloration or disconnection in the silver wiring.

Precipitated crystals were identified by a powder X-ray diffractometer (Rigaku RINT2100).

Three-point bending strength was evaluated according to JIS R1601. .

For the dielectric loss tangent and relative dielectric constant, after sintering the green sheet molded at the firing temperature shown in the table, it was processed into a size of 25 mm × 50 mm × 0.1 mm to make a measurement sample, and then fine ceramics It was measured at a measurement temperature of 25° C. and a frequency of 28 GHz based on the method for measuring microwave dielectric properties of substrates (JIS R1641).

The coefficient of thermal expansion is measured with a thermomechanical analyzer in the temperature range of 30 to 380°C.

As is clear from Table 1, Sample No. 1, which is an example, 1 to 4 had a high three-point bending strength of 260 to 270 MPa because the thickness of the alumina layer was 0.5 to 3 μm. Also, the dielectric loss tangent was as small as 0.0003 to 0.0007. On the other hand, sample no. 5 did not vitrify due to a low _SiO2 of 49% and a high MgO of 26%. Sample no. No. 6 had a low bending strength of 190 MPa because no alumina layer was formed on the glass surface.

Claims (14)

It has a laminated structure in which at least an outer layer, an inner layer, and an outer layer are laminated in this order, each of the outer layers is made of alumina with a thickness of 0.1 to 5 μm, and the inner layer has a glass composition of SiO ₂ 50 to 50% by mass. A laminated glass-ceramic dielectric material comprising a crystallizable glass powder containing 60% CaO, 20-30% CaO, and 15-21% MgO. 2. The laminated glass-ceramic dielectric material of claim 1, wherein said inner layer is a green sheet compact or printed laminate. 3. The laminated glass-ceramic dielectric material of claim 1 or 2, wherein said inner layer is substantially free of ceramic powder. A laminated glass-ceramic dielectric material according to any one of claims 1 to 3, characterized in that said inner layer contains a metal conductor. A laminated glass-ceramic dielectric material according to any one of claims 1 to 4, characterized in that said metal conductor is silver or a silver alloy. A sintered body obtained by sintering the laminated glass-ceramic dielectric material according to any one of claims 1 to 5, characterized in that diopside-based crystals are precipitated as main crystals from the glass matrix of the inner layer. sintered body. It has a laminated structure in which at least an outer layer, an inner layer, and an outer layer are laminated in this order, each of the outer layers is made of alumina with a thickness of 0.1 to 5 μm, and the inner layer is composed of 50 to 60% by mass of SiO _{2 and} CaO. A laminated glass-ceramic sintered body containing 20 to 30% MgO and 15 to 21% MgO, and having diopside crystals precipitated therein. 8. The sintered body according to claim 6 or 7, having a three-point bending strength of 250 MPa or more. 9. The sintered body according to any one of claims 6 to 8, wherein the dielectric loss tangent at a measurement temperature of 25°C and a frequency of 28 GHz is 0.0009 or less. 10. The sintered body according to any one of claims 6 to 9, wherein the dielectric constant at a measurement temperature of 25°C and a frequency of 28 GHz is 8.0 or less. The sintered body according to any one of claims 6 to 10, wherein the inner layer has a coefficient of thermal expansion of 8 to 10 ppm/°C. A method for producing a sintered body, characterized by firing the laminated glass-ceramic dielectric material according to any one of claims 1 to 5. 13. The method for producing a sintered body according to claim 12, wherein the sintering is performed at a temperature of 1000[deg.] C. or less. A high-frequency circuit member having a dielectric layer, wherein the dielectric layer is the sintered body according to any one of claims 6 to 11.