Glass ceramic dielectric material, sintered body, method for producing sintered body, and high frequency circuit component

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]

[0001] The present invention relates to a glass ceramic dielectric material, which is a precursor of a sintered body having a low dielectric loss tangent and high mechanical strength advantageous for signal processing in the high frequency range of 20 GHz or higher, a sintered body, and a high frequency circuit member. [Background technology]

[0002] Alumina ceramics are widely used as wiring boards and circuit components. However, due to their high dielectric constant of 10, alumina ceramics have the disadvantage of slow signal processing speed. Another drawback is that tungsten, which has a high melting point, must be used as the conductor material, resulting in high conductor loss.

[0003] To overcome this drawback, glass-ceramic dielectric materials composed of glass powder and ceramic powder have been developed, and sintered bodies of these materials are used as dielectric layers. For example, a sintered body of a glass-ceramic dielectric material using glass powder in which diopside precipitates as the primary crystal has a relative dielectric constant of 7.3 to 7.8 at 0.1 GHz, which is lower than that of an alumina ceramic material. Furthermore, because it can be fired at temperatures below 1000°C, it can be co-fired with low-melting-point metal materials such as Ag and Cu, which have low conductor loss, and this has the advantage of allowing these to be used as inner-layer conductors (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-120436 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, the frequency bands used in mobile communication devices, such as 5G, and local network communication fields, such as WiFi, have been increasing to 20 GHz or higher, and there is a strong demand for ceramic dielectric materials with even lower dielectric loss tangents in such high-frequency ranges.

[0006] 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 material disclosed in the above patent document exhibits high dielectric properties at 10.1 GHz, but has the problem of large transmission loss in the high-frequency range of 20 GHz and above because its dielectric loss tangent is not sufficiently low.

[0007] Furthermore, the bending strength is low at about 200 MPa, which is insufficient for use as a high-frequency circuit board.

[0008] An object of the present invention is to provide a glass ceramic dielectric material, which is a precursor of a sintered body having a low dielectric loss tangent and high bending strength in the high frequency region of 20 GHz or higher, a sintered body, and a high frequency circuit component. [Means for solving the problem]

[0009] 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 another outer layer are laminated in this order, the outer layers each being made of alumina and having a thickness of 0.1 to 5 μm, and the inner layer contains a crystallizable glass powder containing, in mass %, 50 to 60% SiO2, 20 to 30% CaO, and 15 to 21% MgO as a glass composition.

[0010] In the present invention, "crystallizable glass powder" refers to amorphous glass powder that has the property of precipitating crystals from a glass matrix when heat-treated. "Heat treatment" refers to heat treatment at 800 to 1000°C for 10 minutes or longer.

[0011] In the laminated glass-ceramic dielectric material of the present invention, the inner layer is preferably a green sheet compression-bonded body or a printed laminate.

[0012] In the laminated glass-ceramic dielectric material of the present invention, the inner layer is preferably substantially free of ceramic powder, where "substantially free of ceramic powder" means that the content of ceramic powder in the inner layer is less than 0.1% by mass.

[0013] The laminated glass-ceramic dielectric material of the present invention preferably contains a metal conductor in the inner layer.

[0014] In the laminated glass-ceramic dielectric material of the present invention, the metal conductor is preferably silver or a silver alloy.

[0015] The sintered body of the present invention is a sintered body obtained by sintering the laminated glass-ceramic dielectric material, and preferably has diopside-based crystals precipitated as the main crystals from the glass matrix of the inner layer. Note that "diopside-based crystals" refers to diopside crystals (CaMg(SiO)) and diopside solid solution crystals.

[0016] The sintered body of the present invention has a laminated structure in which at least an outer layer, an inner layer, and another outer layer are laminated in this order, and the outer layers are each made of alumina and have a thickness of 0.1 to 5 μm, and the inner layer contains, by mass%, 50 to 60% SiO2, 20 to 30% CaO, and 15 to 21% MgO, and is characterized in that diopside-based crystals are precipitated.

[0017] The sintered body of the present invention preferably has a three-point bending strength of 250 MPa or more. Here, the "three-point bending strength" refers to a value evaluated in accordance with JIS R1601.

[0018] The sintered body of the present invention preferably has a dielectric loss tangent of 0.0009 or less when measured at a temperature of 25° C. and 28 GHz.

[0019] The sintered body of the present invention preferably has a relative dielectric constant of 8.0 or less at a measurement temperature of 25° C. and 28 GHz.

[0020] The "dielectric loss tangent" and "relative permittivity" refer to values ​​measured at a temperature of 25°C and a frequency of 28 GHz based on the method for measuring microwave dielectric properties of fine ceramic substrates (JIS R1641).

[0021] The sintered body of the present invention preferably has a thermal expansion coefficient of 8 to 10 ppm / ° C. The "thermal expansion coefficient" refers to a value measured in a temperature range of 30 to 380° C. using a thermomechanical analyzer.

[0022] The method for producing a sintered body of the present invention preferably comprises firing the laminated glass-ceramic dielectric material.

[0023] In the method for producing the sintered body of the present invention, firing is preferably carried out at a temperature of 1000°C or less.

[0024] 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 above-mentioned sintered body. [Effects of the Invention]

[0025] The laminated glass-ceramic dielectric material of the present invention can be fired at a low temperature of 1000°C or less, and low-melting-point metal materials such as silver, silver alloys, and copper can be used as inner layer conductors. Furthermore, it has a low dielectric loss tangent in the high-frequency range of 20 GHz or more, and a high bending strength of 250 MPa or more. Therefore, the glass-ceramic dielectric material of the present invention is suitable as a high-frequency circuit component to be mounted on a resin motherboard. DETAILED DESCRIPTION OF THE INVENTION

[0026] 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 a crystallizable glass powder and the outer layer being made of alumina.

[0027] First, the inner layer will be described.

[0028] The glass powder constituting the inner layer preferably contains, in mass %, 50-60% SiO2, 20-30% CaO, and 15-21% MgO as a glass composition. The reasons for limiting the content range of each component as above are explained below. In the explanation of the content range of each component, % refers to mass %.

[0029] SiO2 is a constituent of diopside-based crystals and a component that acts as a network former for glass. The SiO2 content is 50 to 60%, preferably 53 to 57%, and particularly preferably 54 to 56%. If the SiO2 content is too low, vitrification becomes difficult. On the other hand, if the SiO2 content is too high, the melting temperature tends to be high and diopside-based crystals become difficult to precipitate.

[0030] CaO is a component of diopside crystals and a component that lowers the softening point of the crystallizable glass powder. The CaO content is 20 to 30%, preferably 23 to 29%, and particularly preferably 25 to 27%. If the CaO content is too low, the softening point becomes too high. Furthermore, the crystallinity decreases, and the dielectric loss tangent tends to increase. On the other hand, if the CaO content is too high, vitrification becomes difficult. Furthermore, the dielectric loss tangent tends to increase.

[0031] MgO is a component of diopside crystals and a component that lowers the softening point of the crystallizable glass powder. The MgO content is 15 to 21%, and preferably 17 to 20%. If the MgO content is too low, the softening point becomes too high. In addition, the dielectric loss tangent tends to become high. On the other hand, if the MgO content is too high, vitrification becomes difficult. In addition, the crystallinity decreases, and the dielectric loss tangent tends to become high.

[0032] In addition to the above components, components such as Al2O3, B2O3, and ZnO may be added up to 3% each within the range that does not impair the dielectric properties.

[0033] Alkali metal oxides (Li2O, Na2O, K2O) are components that lower the firing temperature but also increase the dielectric loss tangent. Therefore, the content of Li2O + Na2O + K2O is less than 2%, and preferably less than 1%, less than 0.5%, and particularly less than 0.1%. The content of Li2O is preferably less than 0.5%, and particularly less than 0.1%. The content of Na2O is preferably less than 0.5%, and particularly less than 0.1%. The content of K2O is preferably less than 0.5%, and particularly less than 0.1%. Here, "Li2O + Na2O + K2O" refers to the total amount of Li2O, Na2O, and K2O.

[0034] The inner layer is preferably a green sheet compression bonded body or a printed laminate.

[0035] Although the inclusion of ceramic powder in the inner layer can improve the dielectric properties and / or strength, it may hinder the densification of the sintered body. Therefore, it is preferable that the inner layer of the present invention is substantially free of ceramic powder.

[0036] The laminated glass-ceramic dielectric material of the present invention can be fired at temperatures below 1000° C., so that 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, which has low conductor loss.

[0037] Furthermore, it is preferable that, upon firing, diopside-based crystals are precipitated as the main crystals from the crystallizable glass powder contained in the inner layer. Precipitating diopside-based crystals in the inner layer makes it easier to reduce the relative dielectric constant and dielectric loss tangent.

[0038] The thickness of the inner layer is preferably 0.1 to 3.0 mm.

[0039] Next, the outer layer will be described.

[0040] The outer layer is made of alumina, which has high strength and a thermal expansion coefficient of 7 to 7.7 ppm / °C, similar to that of the highly expandable inner layer, making it suitable for increasing the mechanical strength of the glass-ceramic dielectric material of the present invention.

[0041] The outer layer is preferably formed on the surface of the inner layer to a thickness of 0.1 to 5 μm, particularly 0.3 to 4 μm. If the outer layer is too thin, the mechanical strength is likely to decrease. On the other hand, if the outer layer is too thick, there is a risk of the outer layer peeling off.

[0042] Next, the characteristics of the sintered body of the present invention will be described below.

[0043] 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, cracks and the like tend to occur in the sintered body. There is no particular lower limit to the three-point bending strength, but in practice it is 100 MPa or more.

[0044] In the sintered body of the present invention, the dielectric loss tangent at 25°C and 28 GHz is preferably 0.0009 or less, particularly 0.0008 or less. If the dielectric loss tangent is too high, the loss of the transmission signal tends to increase. There is no particular lower limit for the dielectric loss tangent, but in reality it is 0.0001 or more.

[0045] In the sintered body of the present invention, the relative dielectric constant at 25°C and 28 GHz is preferably 8.0 or less, particularly 7.5 or less. If the relative dielectric constant is too high, the signal processing speed tends to be slow. There is no particular lower limit to the relative dielectric constant, but in reality it is 5.0 or more.

[0046] 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 thermal expansion coefficient of the sintered body is too low, distortion is likely to occur due to the difference in thermal expansion when subjected to a heat cycle after soldering to a resin motherboard. On the other hand, if the thermal expansion coefficient is too high, thermal shock resistance will decrease. The "thermal expansion coefficient" is measured using a thermomechanical analyzer in the temperature range of 30 to 380°C.

[0047] Furthermore, a method for producing the sintered body of the present invention will be described below.

[0048] First, a slurry is prepared by adding predetermined amounts of a binder, a plasticizer, and a solvent to the crystallizable glass powder. Suitable binders include polyvinyl butyral resin and methacrylic acid resin, suitable plasticizers include dibutyl phthalate, and suitable solvents include toluene and methyl ethyl ketone.

[0049] The slurry of the crystallizable glass powder is then molded into a green sheet by a doctor blade method, dried, cut to a predetermined size, and mechanically processed to form via holes. For example, a silver conductor or a low-resistance metal material that will become an electrode is printed on the via holes and on the surface of the green sheet. A plurality of such green sheets are then stacked to obtain a laminated green sheet.

[0050] Furthermore, the laminated green sheet can be dip-coated with an alumina slurry to form a uniform alumina layer, followed by firing to obtain a sintered body. The alumina layer may also be formed by printing an alumina paste on the surface of the laminated green sheet after firing, followed by firing again. The thickness of the alumina layer can be changed by adjusting the viscosity of the paste.

[0051] The sintered body thus produced can also be provided with conductors or electrodes inside or on the surface. From the viewpoint of using low-melting-point metal materials such as silver and copper, which have low conductor loss, the firing temperature is preferably 1000°C or less, and particularly 800 to 950°C.

[0052] 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 to the surface of the sintered body produced as described above. [Example]

[0053] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0054] Table 1 shows examples of the present invention (samples Nos. 1 to 4) and comparative examples (samples Nos. 5 and 6).

[0055] [Table 1]

[0056] Each sample was prepared as follows. First, glass raw materials of various oxides were prepared and mixed uniformly to obtain the glass composition shown in the table. The mixture was then placed in a platinum crucible and melted at 1500 to 1580°C for 3 hours, and the molten glass was formed into a thin plate using a water-cooled roller. Next, the obtained glass film was roughly crushed, and then wet-pulverized in a ball mill with the addition of alcohol. The glass was then classified to obtain a glass powder with an average particle size of 1.5 to 3 μm.

[0057] Next, 15% by mass of polyvinyl butyral as a binder, 4% by mass of butyl benzyl phthalate as a plasticizer, and 30% by mass of toluene as a solvent were added to the glass powder to prepare a slurry. The slurry was then formed into 150 μm green sheets using a doctor blade method, dried, and cut to the specified size. Four of these green sheets were then stacked and integrated by thermocompression bonding. The laminated green sheets were then dip-coated with an alumina slurry to form a uniform alumina layer on their surfaces. The stacked green sheets were then fired at 900°C for 1 hour to obtain glass ceramics.

[0058] The samples thus obtained were evaluated for firing temperature, whether or not they could be fired simultaneously with silver, the presence of precipitated crystals, three-point bending strength, dielectric loss tangent, relative dielectric constant, and thermal expansion coefficient. The results are shown in Table 1.

[0059] The firing temperature is the lowest temperature at which ink is applied to sintered bodies fired at various temperatures and then wiped off, leaving no ink behind (i.e., the body is densely sintered).

[0060] The feasibility of silver co-firing was determined by printing a silver conductor on the green sheet before firing, co-firing it, and visually inspecting the silver wiring for discoloration or breakage.

[0061] The precipitated crystals were identified using a powder X-ray diffractometer (Rigaku Corporation, RINT2100).

[0062] The three-point bending strength was evaluated according to JIS R1601.

[0063] The dielectric loss tangent and relative permittivity were measured at a temperature of 25°C and a frequency of 28 GHz based on the method for measuring microwave dielectric properties of fine ceramic substrates (JIS R1641), after the green sheets were sintered at the firing temperatures shown in the table and processed into measurement samples of 25 mm x 50 mm x 0.1 mm.

[0064] The thermal expansion coefficient was measured in the temperature range of 30 to 380°C using a thermomechanical analyzer.

[0065] As is clear from Table 1, the three-point bending strength of Samples Nos. 1 to 4, which are examples, was high at 260 to 270 MPa because the alumina layer thickness was 0.5 to 3 μm. The dielectric loss tangent was also low at 0.0003 to 0.0007. On the other hand, Sample No. 5 did not vitrify because it had a low SiO2 content of 49% and a high MgO content of 26%. Sample No. 6 had a low bending strength of 190 MPa because no alumina layer was formed on the glass surface.

Claims

1. The glass has a laminated structure in which at least an outer layer, an inner layer, and an outer layer are laminated in this order, and the outer layers are each made of alumina with a thickness of 0.1 to 5 μm, and the inner layer has a glass composition of, in mass %, SiO ２ 1. A laminated glass-ceramic dielectric material comprising a crystallizable glass powder containing 50-60% of ZnO, 20-30% of CaO, and 15-21% of MgO.

2. 2. The laminated glass-ceramic dielectric material according to claim 1, wherein the inner layer is a green sheet pressed body or a printed laminate.

3. 3. The laminated glass-ceramic dielectric material of claim 1, wherein the inner layer is substantially free of ceramic powder.

4. 4. The laminated glass-ceramic dielectric material according to claim 1, wherein the inner layer contains a metal conductor.

5. 5. The laminated glass-ceramic dielectric material of claim 4, wherein the metallic conductor is silver or a silver alloy.

6. 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.

7. The laminated structure has at least an outer layer, an inner layer, and an outer layer laminated in this order, and the outer layers are each made of alumina with a thickness of 0.1 to 5 μm, and the inner layer is made of, in mass %, SiO ２ 1. A laminated glass-ceramic sintered body comprising 50 to 60% of SiO 2, 20 to 30% of CaO, and 15 to 21% of MgO, and in which diopside-based crystals are precipitated.

8. 8. The sintered body according to claim 6, wherein the three-point bending strength is 250 MPa or more.

9. 9. The sintered body according to claim 6, wherein the dielectric loss tangent measured at a temperature of 25° C. and a frequency of 28 GHz is 0.0009 or less.

10. 10. The sintered body according to claim 6, wherein the relative dielectric constant is 8.0 or less when measured at a temperature of 25° C. and a frequency of 28 GHz.

11. 11. The sintered body according to claim 6, wherein the inner layer has a thermal expansion coefficient of 8 to 10 ppm / °C.

12. A method for producing a sintered body, comprising 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, characterized in that the sintering is carried out at a temperature of 1000°C or less.

14. 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.

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