Glass Substrate for High-Frequency Device and Circuit Board for High-Frequency Device

Abstract

To provide a glass substrate for a high frequency device capable of reducing a dielectric loss of a high frequency signal and providing a practical electrical device.SOLUTION: A glass substrate 2 contains alkali metal oxide in a range of 0.001 to 5% by molar percentage based on oxide, and has a molar ratio represented by Na2O / (Na2O+K2O) in the alkali metal oxide in a range of 0.01 to 0.99, contains Al2O3 and B2O3 in a range of 1 to 40% as a total content, and has a molar ratio represented by Al2O3 / (Al2O3+B2O3) in a range of 0 to 0.45, and mainly contains SiO2. Surface roughness of at least one main surface of the glass substrate 2 is 1.5 nm or less as a value of arithmetic average roughness Ra, and a dielectric loss tangent at 35 GHz is 0.007 or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a glass substrate for high-frequency devices and a circuit board for high-frequency devices.

Background Art

[0002] In electronic devices such as mobile phones, smartphones, portable information terminals, communication devices such as Wi-Fi devices, surface acoustic wave (SAW) devices, radar components, and antenna components, in order to increase the communication capacity and communication speed, the signal frequency is being increased. As the circuit board used in such high-frequency electronic devices, insulating substrates such as resin substrates, ceramic substrates, and glass substrates are generally used. For the insulating substrate used in high-frequency devices, in order to ensure characteristics such as the quality and intensity of high-frequency signals, it is required to reduce transmission losses based on dielectric loss and conductor loss.

[0003] Among these insulating substrates, the resin substrate has low rigidity due to its characteristics. Therefore, when rigidity (strength) is required for semiconductor package products, it is difficult to apply the resin substrate. The ceramic substrate has a problem that it is difficult to improve the surface smoothness, and thus the conductor loss caused by the conductor formed on the substrate surface tends to increase. On the other hand, the glass substrate has high rigidity, so it is easy to achieve miniaturization and thinning of the package, has excellent surface smoothness, and is also easy to increase in size as the substrate itself.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, although conventional alkali-free glass substrates are effective in reducing dielectric loss and the transmission loss based thereon up to about 20 GHz, beyond that, for example, in a region exceeding 30 GHz, there is a limit to reducing dielectric loss. Therefore, in a circuit board using a conventional alkali-free glass substrate, it becomes difficult to maintain characteristics such as the quality and intensity of high-frequency signals exceeding 30 GHz. On the other hand, while a quartz glass substrate can maintain low dielectric loss even in a region exceeding 30 GHz, since its thermal expansion coefficient is too small, there is a drawback that the difference in thermal expansion coefficient from other members becomes too large when constructing an electronic device. This is a factor that reduces the practicality of the electronic device.

[0006] An object of the present invention is to provide a glass substrate for a high-frequency device capable of reducing the dielectric loss of a high-frequency signal and providing a practical electronic device, and a circuit board for a high-frequency device capable of reducing the transmission loss of a high-frequency signal using the same.

Means for Solving the Problems

[0007] The glass substrate for a high-frequency device according to the first aspect of the present invention contains alkali metal oxide in the range of 0.001 to 5% in terms of molar percentage based on oxides, and the molar ratio represented by Na2O / (Na2O + K2O) among the alkali metal oxides is in the range of 0.01 to 0.99, and contains Al2O3 and B2O3 in total in the range of 1 to 40%, and the molar ratio represented by Al2O3 / (Al2O3 + B2O3) is in the range of 0 to 0.45. It is a glass substrate mainly composed of SiO2, the surface roughness of at least one main surface of the glass substrate is 1.5 nm or less as the value of the arithmetic mean roughness Ra, and the dielectric tangent at 35 GHz is 0.007 or less.

[0008] The glass substrate for high-frequency devices according to the second aspect of the present invention contains alkali metal oxides in the range of 0.001 to 5% in terms of molar percentage based on oxides, and the molar ratio represented by Na2O / (Na2O + K2O) among the alkali metal oxides is in the range of 0.01 to 0.99, and contains alkaline earth metal oxides in the range of 0.1 to 13% as the total content, and is a glass substrate mainly composed of SiO2, wherein the surface roughness of at least one main surface of the glass substrate is 1.5 nm or less as the value of the arithmetic mean roughness Ra, and the dielectric tangent at 35 GHz is 0.007 or less.

[0009] The circuit board for high-frequency devices according to the third aspect of the present invention includes the glass substrate according to the first or second aspect of the present invention and a wiring layer formed on the main surface of the glass substrate, and the transmission loss at 35 GHz is 1 dB / cm or less.

Advantages of the Invention

[0010] According to the glass substrate for high-frequency devices of the present invention, the dielectric loss of high-frequency signals can be reduced. According to a circuit board using such a glass substrate, the transmission loss of high-frequency signals can be reduced, and high-frequency devices such as practical electronic devices can be provided.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described. In the following description, the numerical range indicated by "~" indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. The content rate of each component in the glass substrate indicates the molar percentage (mol%) based on oxide, unless otherwise specified. In this specification, "high frequency" means 10 GHz or more, preferably greater than 30 GHz, and more preferably 35 GHz or more.

[0013] FIG. 1 shows a circuit board for a high-frequency device according to an embodiment of the present invention. The circuit board 1 shown in FIG. 1 includes an insulating glass substrate 2, a first wiring layer 3 formed on the first main surface 2a of the glass substrate 2, and a second wiring layer 4 formed on the second main surface 2b of the glass substrate 2. The first and second wiring layers 3 and 4 form a microstrip line as an example of a transmission line. The first wiring layer 3 constitutes a signal wiring, and the second wiring layer 4 constitutes a ground line. However, the structures of the first and second wiring layers 3 and 4 are not limited to this, and the wiring layer may be formed only on one main surface of the glass substrate 2.

[0014] The first and second wiring layers 3 and 4 are layers formed of a conductor, and their thickness is usually about 0.1 to 50 μm. The conductor forming the first and second wiring layers 3 and 4 is not particularly limited, and for example, metals such as copper, gold, silver, aluminum, titanium, chromium, molybdenum, tungsten, platinum, nickel, alloys or metal compounds containing at least one of these metals are used. The structures of the first and second wiring layers 3 and 4 are not limited to a single-layer structure, and may have a multi-layer structure such as a laminated structure of a titanium layer and a copper layer, for example. The formation methods of the first and second wiring layers 3 and 4 are not particularly limited, and for example, various known formation methods such as a printing method using a conductor paste, a dipping method, a plating method, a vapor deposition method, and sputtering can be applied.

[0015] The glass substrate 2 is made of a glass substrate for high-frequency devices according to an embodiment of the present invention, and has a property that the dielectric loss tangent (tanδ) at 35 GHz is 0.007 or less. The relative permittivity of the glass substrate 2 at 35 GHz is preferably 10 or less. By setting the dielectric loss tangent of the glass substrate 2 at 35 GHz to 0.007 or less, the dielectric loss in a high-frequency region exceeding 30 GHz can be reduced. By setting the relative permittivity of the glass substrate 2 at 35 GHz to 10 or less, the dielectric loss in the high-frequency region can also be reduced. The dielectric loss tangent of the glass substrate 2 at 35 GHz is more preferably 0.005 or less, and even more preferably 0.003 or less. The relative permittivity of the glass substrate 2 is more preferably 7 or less, even more preferably 6 or less, and particularly preferably 5 or less.

[0016] Furthermore, the surface roughness of the main surfaces 2a and 2b on which the first and second wiring layers 3 and 4 of the glass substrate 2 are formed is 1.5 nm or less as the value of the arithmetic mean roughness Ra. By setting the arithmetic mean roughness Ra of the main surfaces 2a and 2b on which the first and second wiring layers 3 and 4 of the glass substrate 2 are formed to 1.5 nm or less, even when the skin effect occurs in the first and second wiring layers 3 and 4 in a high-frequency region exceeding 30 GHz, the skin resistance of the first and second wiring layers 3 and 4 can be reduced, thereby reducing the conductor loss. The arithmetic mean roughness Ra of the main surfaces 2a and 2b of the glass substrate 2 is more preferably 1.0 nm or less, and even more preferably 0.5 nm or less. The main surface of the glass substrate 2 refers to the surface on which the wiring layer is formed. When the wiring layer is formed on one main surface, it is sufficient that the value of the arithmetic mean roughness Ra of one main surface satisfies 1.5 nm or less. Note that the surface roughness Ra in this specification means a value obtained in accordance with JIS B0601 (2001).

[0017] The surface roughness of the main surfaces 2a and 2b of the glass substrate 2 can be achieved by subjecting the surface of the glass substrate 2 to a polishing process or the like as necessary. For the polishing process of the surface of the glass substrate 2, for example, a polishing agent mainly composed of cerium oxide, colloidal silica, or the like, and mechanical polishing using a polishing pad, a polishing slurry using a polishing agent, an acidic liquid or an alkaline liquid as a dispersion medium, and chemical mechanical polishing using a polishing pad, chemical polishing using an acidic liquid or an alkaline liquid as an etching liquid, etc. can be applied. These polishing processes are applied according to the surface roughness of the glass plate that is the material of the glass substrate 2, and for example, they may be applied in combination of preliminary polishing and finish polishing. Further, the end face of the glass substrate 2 is preferably chamfered in order to prevent cracking, chipping, and breakage of the glass substrate 2 caused by the end face during the process flow. The chamfering form may be any of C chamfering, R chamfering, thread chamfering, etc.

[0018] By using such a glass substrate 2, the transmission loss of the circuit board 1 at 35 GHz can be reduced, specifically, reduced to 1 dB / cm or less. Therefore, since the characteristics such as the quality and intensity of high-frequency signals, particularly high-frequency signals exceeding 30 GHz, and further high-frequency signals of 35 GHz or more are maintained, it is possible to provide a glass substrate 2 and a circuit board 1 suitable for high-frequency devices that handle such high-frequency signals. That is, the characteristics and quality of high-frequency devices that handle such high-frequency signals can be improved. The transmission loss of the circuit board 1 at 35 GHz is more preferably 0.5 dB / cm or less.

[0019] The glass substrate 2 having dielectric properties such as dielectric tangent as described above can be realized by satisfying the following condition (1) and condition (2), condition (1) and condition (3), or condition (1), condition (2) and condition (3) in a glass substrate having a network-forming substance mainly composed of SiO2. Here, the glass substrate 2 is formed by melting and curing a raw material composition. The manufacturing method of the glass substrate 2 is not particularly limited, but a method such as forming a general molten glass into a predetermined plate thickness by the float method and cutting it into a desired shape after slow cooling to obtain a plate glass can be applied.

[0020] Here, the glass in this specification means a solid that is amorphous from its definition and exhibits a glass transition. It does not include crystallized glass which is a mixture of glass and crystals, or a glass sintered body containing a crystalline filler. Whether it consists only of amorphous can be confirmed, for example, by performing X-ray diffraction measurement and finding no distinct diffraction peaks.

[0021] Also, "mainly composed of SiO2" in this specification means that the content of SiO2 is the largest in terms of the proportion of components in mol% based on oxides.

[0022] Condition (1): The glass substrate 2 contains alkali metal oxides in a total content range of 0.001 to 5%, and the molar ratio represented by Na2O / (Na2O + K2O) among the alkali metal oxides is in the range of 0.01 to 0.99.

[0023] Condition (2): The glass substrate 2 contains Al2O3 and B2O3 in a total content range of 1 to 40%, and the molar ratio represented by Al2O3 / (Al2O3 + B2O3) is in the range of 0 to 0.45.

[0024] Condition (3): The glass substrate 2 contains alkaline earth metal oxides in a total content range of 0.1 to 13%.

[0025] Regarding condition (1), by setting the content of alkali metal oxides in the glass substrate 2 mainly composed of SiO2 to 5% or less, the low dielectric loss property of the glass substrate 2 can be enhanced. Also, by setting the content of alkali metal oxides to 0.001% or more, excessive raw material purification is not required, and practical glass meltability and the productivity of the glass substrate 2 can be obtained, and the thermal expansion coefficient of the glass substrate 2 can be adjusted. Examples of the alkali metal oxides contained in the glass substrate 2 include Li2O, Na2O, K2O, Rb2O, and Cs2O. Since Na2O and K2O are particularly important, it is preferable that the total content of Na2O and K2O is in the range of 0.001 to 5%. The content of alkali metal oxides is preferably 3% or less, more preferably 1% or less, further preferably 0.2% or less, still further preferably 0.1% or less, and particularly desirably 0.05% or less. The content of alkali metal oxides is more preferably 0.002% or more, further preferably 0.003% or more, and particularly preferably 0.005% or more.

[0026] Furthermore, by coexisting Na2O and K2O in the glassy substance mainly composed of SiO2, in other words, by setting the molar ratio represented by Na2O / (Na2O + K2O) in the range of 0.01 to 0.99, the movement of the alkali component can be suppressed, and thus the low dielectric loss property of the glass substrate 2 can be enhanced. The molar ratio represented by Na2O / (Na2O + K2O) is more preferably 0.98 or less, further preferably 0.95 or less, and particularly preferably 0.9 or less. The molar ratio represented by Na2O / (Na2O + K2O) is more preferably 0.02 or more, further preferably 0.05 or more, and particularly preferably 0.1 or more.

[0027] In addition to the condition (1) that defines the amount and ratio of the above-mentioned alkali metal oxide, by satisfying the amount and ratio of Al2O3 and B2O3 in condition (2), the amount of alkaline earth metal oxide in condition (3), or both condition (2) and condition (3), the dielectric tangent of the glass substrate 2 at 35 GHz can be made 0.007 or less. In condition (2), Al2O3 is not essential, but it is a component that is effective in improving weather resistance, suppressing the phase separation of the glass, and reducing the thermal expansion coefficient, and its content is preferably in the range of 0 to 15%. B2O3 is a component that is effective in improving the dissolution reactivity of the glass and reducing the devitrification temperature, and its content is preferably in the range of 9 to 30%.

[0028] In condition (2), when the molar ratio represented by Al2O3 / (Al2O3 + B2O3) is 0.45 or less, the low dielectric loss property of the glass substrate 2 can be enhanced. The molar ratio represented by Al2O3 / (Al2O3 + B2O3) may be 0. Even when the molar ratio represented by Al2O3 / (Al2O3 + B2O3) is 0, it is more preferably 0.4 or less, and even more preferably 0.3 or less. The molar ratio represented by Al2O3 / (Al2O3 + B2O3) is preferably 0.01 or more, and more preferably 0.05 or more.

[0029] When the total content of Al2O3 and B2O3 (including the case where the content of Al2O3 is 0) is 1% or more, the solubility of the glass, etc. can be enhanced. The total content of Al2O3 and B2O3 is more preferably 3% or more, even more preferably 5% or more, and particularly preferably 7% or more. Also, when the total content of Al2O3 and B2O3 (including the case where the content of Al2O3 is 0) is 40% or less, the low dielectric loss property of the glass substrate 2 can be enhanced while maintaining the solubility of the glass, etc. The total content of Al2O3 and B2O3 is more preferably 37% or less, even more preferably 35% or less, and particularly preferably 33% or less.

[0030] If the content of Al2O3 is 15% or less, the solubility of the glass and the like can be improved. The content of Al2O3 is more preferably 14% or less. The content of Al2O3 is more preferably 0.5% or more. If the content of B2O3 is 30% or less, the acid resistance and the strain point can be improved. The content of B2O3 is more preferably 28% or less, further preferably 26% or less, particularly preferably 24% or less, and most preferably 23% or less. Also, if the content of B2O3 is 9% or more, the solubility can be improved. The content of B2O3 is more preferably 13% or more, and further preferably 16% or more.

[0031] In condition (3), examples of the alkaline earth metal oxide include MgO, CaO, SrO, and BaO, and all of these function as components that enhance the dissolution reactivity of the glass. If the total content of such alkaline earth metal oxides is 13% or less, the low dielectric loss property of the glass substrate 2 can be enhanced. The total content of the alkaline earth metal oxides is more preferably 11% or less, further preferably 10% or less, particularly preferably 8% or less, and most preferably 6% or less. Also, if the total content of the alkaline earth metal oxides is 0.1% or more, the solubility of the glass can be maintained well. The total content of the alkaline earth metal oxides is more preferably 3% or more, and further preferably 5% or more.

[0032] MgO is not an essential component, but it is a component that increases the Young's modulus without increasing the specific gravity. That is, MgO is a component that can increase the specific elastic modulus, thereby reducing the problem of deflection, improving the fracture toughness value, and increasing the glass strength. Also, MgO is a component that improves the solubility. MgO is not an essential component, but the content of MgO is preferably 0.1% or more, more preferably 1% or more, and further preferably 3% or more. If the content of MgO is 0.1% or more, the effect of containing MgO can be sufficiently obtained, and the thermal expansion coefficient can be prevented from becoming too low. The content of MgO is preferably 13% or less, more preferably 11% or less, and further preferably 9% or less. If the content of MgO is 13% or less, the increase in the devitrification temperature can be suppressed.

[0033] CaO has the characteristics of having a relatively high specific modulus of elasticity after MgO among alkaline earth metals and not excessively reducing the strain point, and is a component that improves solubility like MgO. Furthermore, it is also a component that has the characteristic of being difficult to increase the devitrification temperature compared to MgO. CaO is not an essential component, but the content of CaO is preferably 0.1% or more, more preferably 1% or more, and even more preferably 3% or more. If CaO is 0.1% or more, the effect of containing CaO can be sufficiently obtained. Also, the content of CaO is preferably 13% or less, more preferably 10% or less, and even more preferably 8% or less. If the content of CaO is 13% or less, the average coefficient of thermal expansion does not become too high, and the increase in the devitrification temperature can be suppressed to prevent devitrification during glass production.

[0034] SrO is a component that does not increase the devitrification temperature of the glass and improves solubility. SrO is not an essential component, but the content of SrO is preferably 0.1% or more, more preferably 0.5% or more, even more preferably 1.0% or more, even more preferably 1.5% or more, and particularly preferably 2% or more. If the content of SrO is 0.1% or more, the effect of containing SrO can be sufficiently obtained. Also, the content of SrO is preferably 13% or less, more preferably 10% or less, even more preferably 7% or less, and particularly preferably 5% or less. If the content of SrO is 13% or less, it is possible to suppress the excessive increase in the specific gravity and the average coefficient of thermal expansion without making the specific gravity too large.

[0035] BaO is not an essential component, but it is a component that does not increase the devitrification temperature of the glass and improves solubility. However, when a large amount of BaO is contained, the specific gravity increases, the Young's modulus decreases, the relative dielectric constant increases, and the average coefficient of thermal expansion tends to become too large. Therefore, the content of BaO is preferably 10% or less, more preferably 8% or less, more preferably 5% or less, even more preferably 3% or less, and it is particularly preferable not to substantially contain it.

[0036] In this specification, "substantially free of" means containing nothing other than inevitable impurities mixed in from raw materials, etc., that is, not intentionally containing. In the present invention, being substantially free of BaO means, for example, 0.3% or less.

[0037] As described above, in addition to condition (1), by satisfying condition (2) or condition (3), the dielectric tangent of the glass substrate 2 at 35 GHz can be made 0.007 or less, and the dielectric loss of the glass substrate 2 can be reduced. In order to further enhance the low dielectric loss property of the glass substrate 2, it is more preferable that the glass substrate 2 satisfies all of condition (1), condition (2), and condition (3).

[0038] Among the constituent components of the glass substrate 2, the content of SiO2 as a network-forming substance, which is the main component, is preferably in the range of 40 to 75%. If the content of SiO2 is 40% or more, the glass-forming ability and weather resistance can be improved, and devitrification can be suppressed. The content of SiO2 is more preferably 45% or more, further preferably 50% or more, and particularly preferably 55% or more. Also, if the content of SiO2 is 75% or less, the solubility of the glass can be improved. The content of SiO2 is more preferably 74% or less, further preferably 73% or less, and particularly preferably 72% or less.

[0039] In addition to the above-described components, the glass substrate 2 may contain, as optional components, Fe2O3, TiO2, ZrO2, ZnO, Ta2O5, WO3, Y2O3, La2O3, etc. Fe2O3 is a component that controls the light absorption performance of the glass substrate 2, such as infrared absorption performance and ultraviolet absorption performance. If necessary, the content of Fe in terms of Fe2O3 can be contained up to 0.012% or less. If the above-described content of Fe is 0.012% or less, the low dielectric loss property and ultraviolet transmittance of the glass substrate 2 can be maintained. For improving the ultraviolet transmittance, the content of Fe is more preferably 0.01% or less, and even more preferably 0.005% or less. By increasing the ultraviolet transmittance of the glass substrate 2, an ultraviolet curable material can be used in a lamination process or the like in the manufacturing process of a high-frequency device, and the manufacturability of the high-frequency device can be improved.

[0040] Further, the glass substrate 2 can enhance its ultraviolet shielding ability by containing 0.05% or more of Fe in terms of Fe2O3, if necessary. The content of Fe is more preferably 0.07% or more, and even more preferably 0.1% or more. By enhancing the ultraviolet shielding ability of the glass substrate 2, when a resin that deteriorates by ultraviolet rays is used as a member, the glass substrate 2 can be given a function as a protective material.

[0041] In further improving the low dielectric loss property of the glass substrate 2, the β-OH value of the glass substrate 2 is preferably in the range of 0.05 to 0.6 mm -1 . The β-OH value is a value used as an index of the moisture content of the glass. It is a value obtained by measuring the absorbance of the glass sample for light with a wavelength of 2.75 to 2.95 μm and dividing the maximum value βmax by the sample thickness (mm). By setting the β-OH value of the glass composition to 0.6 mm -1 or less, the low dielectric loss property of the glass substrate 2 can be further improved. The β-OH value of the glass substrate 2 is more preferably 0.5 mm -1 or less, and even more preferably 0.4 mm -1 or less. Also, when the β-OH value of the glass substrate 2 is 0.05 mm -1In this case, it is not necessary to melt in an extremely dry atmosphere or extremely reduce the moisture content in the raw materials, and the productivity of the glass and the quality of the foam can be improved. The β-OH value of the glass substrate 2 is 0.1 mm -1 or more is more preferable, and 0.2 mm -1 or more is even more preferable.

[0042] The glass substrate 2 has a coefficient of thermal expansion suitable for electronic devices according to the content of alkali metal oxides, alkaline earth metal oxides, etc. Specifically, the average coefficient of thermal expansion at 50 to 350 °C is in the range of 3 to 15 ppm / °C. According to the glass substrate 2 having such a coefficient of thermal expansion, when constructing a semiconductor package or the like as a high-frequency device, the difference in the coefficient of thermal expansion from other members can be adjusted more appropriately. For example, when constructing a glass through-wiring substrate (TGV substrate) of a 2.5D or 3D (three-dimensional) mounting type for high-frequency applications, the difference in the coefficient of thermal expansion from other members such as semiconductor chips can be adjusted more appropriately.

[0043] Furthermore, the glass substrate 2 preferably has a Young's modulus of 40 GPa or more. According to the glass substrate 2 having such a Young's modulus, when flowing the glass substrate 2 during the manufacturing process (wafer process) of a high-frequency device, the amount of deflection can be suppressed to, for example, 1 mm or less, so that the occurrence of manufacturing defects in high-frequency devices can be suppressed. The Young's modulus of the glass substrate 2 is more preferably 50 GPa or more, and even more preferably 55 GPa or more. Also, the porosity of the glass substrate 2 is preferably 0.1% or less. Thereby, the generation of noise and the like when manufacturing a high-frequency device can be suppressed. The porosity of the glass substrate 2 is more preferably 0.01% or less, and even more preferably 0.001% or less.

[0044] The transmittance of the glass substrate 2 at a wavelength of 350 nm is preferably 50% or more. By this, an ultraviolet curable material can be used in a lamination process or the like in the manufacturing process of a high-frequency device, and the manufacturability of the high-frequency device can be improved. Further, the transmittance of the glass substrate 2 at a wavelength of 350 nm is more preferably 70% or more in order to shorten the irradiation time of ultraviolet rays on the ultraviolet curable material and reduce the curing unevenness of the ultraviolet curable material in the thickness direction in the manufacturing process of the device.

[0045] For the same reason, the transmittance of the glass substrate 2 at a wavelength of 300 nm is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. Further, the transmittance of the glass substrate 2 at a wavelength of 250 nm is preferably 5% or more, more preferably 10% or more, and even more preferably 20% or more.

[0046] The transmittance of the glass substrate 2 at a wavelength of 350 nm is preferably 80% or less. By this, when a resin deteriorated by ultraviolet rays is used as a member, the glass substrate 2 can be provided with an ultraviolet shielding ability and given a function as a protective material. The transmittance of the glass substrate 2 at a wavelength of 350 nm is more preferably 60% or less, even more preferably 30% or less, and most preferably 10% or less.

[0047] For the same reason, the transmittance of the glass substrate 2 at a wavelength of 300 nm is preferably 80% or less, more preferably 60% or less, even more preferably 30% or less, and most preferably 10% or less. Further, the transmittance of the glass substrate 2 at a wavelength of 250 m is preferably 60% or less, more preferably 30% or less, even more preferably 10% or less, and most preferably 5% or less.

[0048] The shape of the glass substrate 2 is not particularly limited, but its thickness is preferably in the range of 0.05 to 1 mm, and the area of one main surface of the glass substrate 2 is 225 to 10000 cm 2It is preferably so. When the thickness of the glass substrate 2 is 1 mm or less, it is possible to achieve thinning and miniaturization of the high-frequency device, and further improvement of production efficiency. In addition, the ultraviolet transmittance can be increased, and the productivity can be enhanced by using an ultraviolet curable material in the manufacturing process of the device. The thickness of the glass substrate 2 is more preferably 0.5 mm or less. Further, if the thickness of the glass substrate 2 is 0.05 mm or more, the strength and the like during the flow of the glass substrate 2 can be maintained. In addition, the ultraviolet shielding ability can be increased, and it becomes possible to protect the resin deteriorated by ultraviolet rays. The thickness of the glass substrate 2 is more preferably 0.1 mm or more, and even more preferably more than 0.2 mm. Furthermore, according to the glass substrate 2 of the embodiment, the substrate size of 2 10000 cm 2 can be provided with the above-described thickness, and it is possible to cope with an increase in panel size and the like. The area of the glass substrate 2 is more preferably 3600 cm

[0049] The devitrification temperature of the glass substrate 2 is preferably 1400 °C or less. When the devitrification temperature is 1400 °C or less, when forming the glass, the member temperature of the forming equipment can be lowered, and the member life can be extended. The devitrification temperature is more preferably 1350 °C or less, even more preferably 1330 °C or less, and particularly preferably 1300 °C or less. The devitrification temperature of the glass is the average value of the highest temperature at which crystals precipitate on the surface and inside of the glass and the lowest temperature at which no crystals precipitate, obtained by putting glass particles crushed in a platinum dish into an electric furnace controlled at a constant temperature and performing heat treatment for 17 hours, and observing the sample after heat treatment with an optical microscope.

[0050] Next, a method for manufacturing the glass substrate of the embodiment will be described. When manufacturing the glass substrate of the embodiment, it passes through a melting step of heating a glass raw material to obtain molten glass, a fining step of removing bubbles from the molten glass, a forming step of forming the molten glass into a plate shape to obtain a glass ribbon, and a slow cooling step of slowly cooling the glass ribbon to room temperature. Alternatively, a method of forming the molten glass into a block shape, slowly cooling it, and then manufacturing the glass substrate through cutting and polishing may also be used.

[0051] In the melting process, raw materials are prepared to achieve the composition of the target glass substrate, and the raw materials are continuously fed into a melting furnace and heated to about 1450°C to 1750°C, preferably, to obtain molten glass.

[0052] Halides such as oxides, carbonates, nitrates, hydroxides, and chlorides can also be used as raw materials. When there is a process in which the molten glass comes into contact with platinum during the melting or fining process, minute platinum particles may elute into the molten glass and may be mixed as foreign matter into the resulting glass substrate. However, the use of nitrate raw materials has the effect of preventing the generation of platinum foreign matter.

[0053] As nitrates, strontium nitrate, barium nitrate, magnesium nitrate, calcium nitrate, etc. can be used. It is more preferable to use strontium nitrate. The raw material particle size can be appropriately used from raw materials with a large particle size of several hundred microns to a small particle size of about several microns that does not cause scattering during raw material conveyance and does not aggregate as secondary particles so that no undissolved residue occurs. The use of granulated bodies is also possible. The water content of the raw materials can be appropriately adjusted to prevent the scattering of the raw materials. The melting conditions such as β-OH, the degree of oxidation-reduction of Fe (redox [Fe 2+ / (Fe 2+ +Fe 3+ )]) can also be appropriately adjusted and used.

[0054] The next fining process is a process of removing bubbles from the molten glass obtained in the above melting process. As the fining process, a defoaming method by reducing pressure may be applied, or defoaming may be performed by setting a temperature higher than the melting temperature of the raw materials. Further, in the manufacturing process of the glass substrate in the embodiment, SO3 or SnO2 can be used as a fining agent. As the SO3 source, sulfates of at least one element selected from Al, Na, K, Mg, Ca, Sr, and Ba are preferable, sulfates of alkaline earth metals are more preferable, and among them, CaSO4·2H2O, SrSO4, and BaSO4 are particularly preferable because they have a remarkable effect of enlarging bubbles.

[0055] In the defoaming method by reduced pressure, it is preferable to use a halogen such as Cl or F as a fining agent. As the Cl source, chlorides of at least one element selected from Al, Mg, Ca, Sr, and Ba are preferable, chlorides of alkaline earth metals are more preferable, and among them, SrCl2·6H2O and BaCl2·2H2O are particularly preferable because they have a remarkable effect of enlarging bubbles and have little deliquescence. As the F source, fluorides of at least one element selected from Al, Na, K, Mg, Ca, Sr, and Ba are preferable, fluorides of alkaline earth metals are more preferable, and among them, CaF2 is more preferable because it has a remarkable effect of increasing the solubility of the glass raw material.

[0056] Tin compounds represented by SnO2 generate O2 gas in the glass melt. In the glass melt, it is reduced from SnO2 to SnO at a temperature of 1450 °C or higher, generating O2 gas and having an effect of greatly growing bubbles. When manufacturing the glass substrate 2 of the embodiment, since the glass raw material is heated to about 1450 to 1750 °C and melted, the bubbles in the glass melt become larger more effectively. When using SnO2 as a fining agent, the tin compound in the raw material is prepared to contain 0.01% or more in terms of SnO2 conversion based on the total amount of 100% of the mother composition. When the SnO2 content is 0.01% or more, a fining effect during the dissolution of the glass raw material can be obtained, preferably 0.05% or more, more preferably 0.10% or more. If the SnO2 content is 0.3% or less, the coloring and devitrification of the glass can be suppressed. The content of the tin compound in the non-alkali glass is more preferably 0.25% or less, even more preferably 0.2% or less, and particularly preferably 0.15% or less in terms of SnO2 conversion based on the total amount of 100% of the mother composition.

[0057] The next forming step is a step of forming the molten glass from which bubbles have been removed in the above fining step into a plate shape to obtain a glass ribbon. As the forming step, known methods for forming glass into a plate shape such as the float method of flowing the molten glass onto a molten metal such as tin to form a plate shape to obtain a glass ribbon, the overflow down-draw method (fusion method) of flowing the molten glass downward from a trough-shaped member, and the slit down-draw method of flowing it from a slit can be applied.

[0058] Next, the slow cooling process is a process of cooling the glass ribbon obtained in the above forming process under controlled cooling conditions to room temperature. As the slow cooling process, the glass ribbon is cooled so that the average cooling rate becomes R until the viscosity reaches the temperature from the annealing point to the strain point, and then slowly cooled to room temperature under predetermined conditions. After cutting the slowly cooled glass ribbon, a glass substrate is obtained.

[0059] If the cooling rate R in the slow cooling process is too large, strain is likely to remain in the glass after cooling. In addition, the equivalent cooling rate, which is a parameter reflecting the fictive temperature, becomes too high, and as a result, low dielectric loss characteristics cannot be obtained. Therefore, it is preferable to set R so that the equivalent cooling rate is 800 °C / min or less. The equivalent cooling rate is more preferably 400 °C / min or less, further preferably 100 °C / min or less, and particularly preferably 50 °C / min or less. On the other hand, if the cooling rate is too small, there is a problem that the required time for the process becomes too long and the productivity decreases. Therefore, it is preferably set to 0.1 °C / min or more, more preferably 0.5 °C / min or more, and further preferably 1 °C / min or more.

[0060] Here, the definition and evaluation method of the equivalent cooling rate are as follows. Glass of the target composition processed into a rectangular parallelepiped of 10 mm × 10 mm × 0.3 to 2.0 mm is held at the annealing point + 170 °C for 5 minutes using an infrared heating electric furnace, and then the glass is cooled to room temperature (25 °C). At this time, a plurality of glass samples with the cooling rate oscillated in the range of 1 °C / min to 1000 °C / min are prepared.

[0061] Using a precision refractometer (for example, KPR2000 manufactured by Shimadzu Corporation), the refractive index n d of the d-line (wavelength 587.6 nm) of a plurality of glass samples is measured. The V-block method or the minimum deviation method may be used for the measurement. By plotting the obtained n d against the logarithm of the cooling rate, a calibration curve of n d with respect to the cooling rate is obtained.

[0062] Next, measure the n of glass of the same composition actually manufactured through steps such as melting, forming, and cooling. d The obtained n d Find the corresponding cooling rate (referred to as the equivalent cooling rate in this embodiment) corresponding to the obtained n from the calibration curve.

[0063] The present invention is not limited to the above embodiments. Modifications, improvements, etc. within the scope that can achieve the object of the present invention are included in the present invention. For example, when manufacturing the glass substrate of the present invention, the glass may be formed into a plate shape by a press forming method in which molten glass is directly formed into a plate shape.

[0064] Also, when manufacturing the glass substrate of the present invention, in addition to the manufacturing method using a refractory melting tank, a crucible made of platinum or an alloy mainly composed of platinum (hereinafter referred to as a platinum crucible) may be used in the melting tank or the clarification tank. When using a platinum crucible, in the melting step, prepare raw materials so as to obtain the composition of the glass substrate to be obtained, heat the platinum crucible containing the raw materials in an electric furnace, and preferably heat it to about 1450°C to 1700°C. Insert a platinum stirrer and stir for 1 to 3 hours to obtain molten glass.

[0065] In the forming step in the manufacturing process of the glass plate using a platinum crucible, pour the molten glass, for example, onto a carbon plate or into a mold to make it into a plate shape or a block shape. In the slow cooling step, typically, after maintaining the temperature at about Tg + 50°C, cool it to near the strain point at about 1 to 10°C / min, and then cool it to room temperature at a cooling rate such that no strain remains. After cutting and polishing to a predetermined shape, a glass substrate is obtained. Also, the glass substrate obtained by cutting may be heated to about Tg + 50°C, for example, and then slowly cooled to room temperature at a predetermined cooling rate. By doing so, the equivalent cooling temperature of the glass can be adjusted.

[0066] The circuit board 1 using the glass substrate 2 of the above-described embodiment is suitable for high-frequency devices that handle high-frequency signals, particularly high-frequency signals exceeding 30 GHz, and more particularly high-frequency signals of 35 GHz or higher. It is possible to reduce the transmission loss of such high-frequency signals and improve characteristics such as the quality and intensity of the high-frequency signals. The glass substrate 2 and the circuit board 1 of the embodiment are suitable for high-frequency devices (electronic devices) such as semiconductor devices used in communication devices such as mobile phones, smartphones, portable information terminals, and Wi-Fi devices, surface acoustic wave (SAW) devices, radar components such as radar transmitters and receivers, and antenna components such as liquid crystal antennas.

Example

[0067] Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. Note that Examples 1 to 3 and 7 to 25 are examples, and Examples 4 to 6 are comparative examples.

[0068] [Examples 1 to 3, 7 to 25]

[0069] Glass substrates having the compositions shown in Tables 1 to 4, a thickness of 0.125 mm, a shape of 50 × 50 mm, and an arithmetic mean roughness Ra of the main surface of 1.0 nm were prepared. The glass substrates were produced by a melting method using a platinum crucible. Raw materials such as silica sand were mixed so as to be 1 kg of glass, and a batch was prepared. Based on 100% of the raw materials of the target composition, in terms of mass percentage representation based on oxides, 0.1% to 1% of sulfate in terms of SO3 conversion, 0.16% of F, and 1% of Cl were added. The raw materials were placed in a platinum crucible and heated in an electric furnace at a temperature of 1650 ° C for 3 hours to be melted into molten glass. During melting, a platinum stirrer was inserted into the platinum crucible and stirred for 1 hour to homogenize the glass. The molten glass was poured out onto a carbon plate and formed into a plate shape. After that, the plate-shaped glass was placed in an electric furnace at a temperature of about Tg + 50 ° C and held for 1 hour, and then the temperature of the electric furnace was lowered to Tg - 100 ° C at a cooling rate of 1 ° C / min, and then the glass was allowed to cool until it reached room temperature. Thereafter, the glass was formed into a plate shape by cutting and polishing.

[0070] For the glass substrates of Examples 1 to 3 and 7 to 25, the average coefficient of thermal expansion, β-OH value, Young's modulus, porosity, transmittance at a wavelength of 350 nm, density, specific elastic modulus, and devitrification temperature at 50 to 350 °C are shown in Tables 5 to 8. Note that the values in parentheses in the table are obtained by calculation. Also, the dielectric tangent at 35 GHz, relative permittivity at 35 GHz, wiring width, transmission loss at 35 GHz, and transmission loss at 110 GHz are shown in Tables 9 to 12. As shown in FIG. 1, a copper wiring layer with a thickness of 0.125 mm was formed as a signal wiring on the first main surface of the glass substrate, and a solid film-like copper layer with a thickness of 0.125 mm was formed as a ground line on the second main surface. The circuit board thus fabricated was subjected to the characteristic evaluation described below.

[0071] [Example 4]

[0072] A soda-lime glass substrate having the composition shown in Table 1, a thickness of 0.125 mm, a shape of 50 × 50 mm, and an arithmetic mean roughness Ra of the main surface of 1.0 nm, manufactured by the float process, was prepared. The characteristics of the glass substrate of Example 4 are shown in Tables 5 and 9 in the same manner as in Example 1. On both main surfaces of such a glass substrate, a copper wiring layer with a thickness of 0.125 mm and a copper layer with a thickness of 0.125 mm were formed in the same manner as in Example 1, and the characteristic evaluation described below was performed.

[0073] [Example 5]

[0074] An alkali-free glass substrate having the composition shown in Table 1, a thickness of 0.125 mm, a shape of 50 × 50 mm, and an arithmetic mean roughness Ra of the main surface of 1.0 nm, manufactured by the float process, was prepared. The characteristics of the glass substrate of Example 5 are shown in Tables 5 and 9 in the same manner as in Example 1. On both main surfaces of such a glass substrate, a copper wiring layer with a thickness of 0.125 mm and a copper layer with a thickness of 0.125 mm were formed in the same manner as in Example 1, and the characteristic evaluation described below was performed.

[0075] [Example 6]

[0076] A quartz glass substrate having the composition shown in Table 1, with a thickness of 0.125 mm, a shape of 50×50 mm, and an arithmetic mean roughness Ra of the main surface of 1.0 nm, manufactured by the vapor phase synthesis method, was prepared. In the composition in Table 1, (0.0) indicates that the component content is less than 0.05%. The characteristics of the glass substrate of Example 6 are shown in Tables 5 and 9 in the same manner as in Example 1. Copper wiring layers with a thickness of 0.125 mm and copper layers with a thickness of 0.125 mm were formed on both main surfaces of such a glass substrate in the same manner as in Example 1, and used for the characteristic evaluation described later.

[0077] The measurement methods for each physical property are shown below. (Relative permittivity, dielectric loss tangent) Measured using a cavity resonator and a vector network analyzer in accordance with the method specified in JIS R1641 (2007). The measurement frequency is 35 GHz, which is the resonance frequency of the air in the cavity resonator. (Average coefficient of thermal expansion) Measured using a differential thermal dilatometer in accordance with the method specified in JIS R3102 (1995). The measurement temperature range is 50 to 350 °C, and the unit is expressed as ppm / °C. (Young's modulus) Measured for glass with a thickness of 0.5 to 10 mm by the ultrasonic pulse method in accordance with the method specified in JIS Z 2280. The unit is expressed as GPa. (Transmittance) The transmittance of a mirror-polished glass with a predetermined thickness was measured using a visible ultraviolet spectrophotometer. The transmittance was expressed as the external transmittance including the loss due to reflection. (Porosity) The bubbles contained in the glass substrate were observed with an optical microscope, the number and diameter of the bubbles were determined, and the volume of the bubbles contained per unit volume was calculated to obtain the porosity. (β-OH) Obtained by the method described in the above embodiment. (Ra) The average roughness of the glass surface in a 10 μm□ area was measured by AFM in accordance with the method specified in JIS B0601 (2001). (Density) The density of a glass mass of about 20 g without bubbles was measured by the Archimedes method. (Devitrification temperature) The ground glass particles were placed in a platinum dish and heat-treated in an electric furnace controlled at a constant temperature for 17 hours. The average value of the highest temperature at which crystals precipitate inside the glass and the lowest temperature at which no crystals precipitate was determined by optical microscope observation of the sample after heat treatment.

[0078] [Table 1]

[0079] [Table 2]

[0080] [Table 3]

[0081] [Table 4]

[0082] [Table 5]

[0083] [Table 6]

[0084] [Table 7]

[0085] [Table 8]

[0086] (Calculation example of transmission loss) To confirm the influence of the dielectric characteristics of the glass substrate materials in Examples 1 to 6 on the transmission loss of high-frequency signals, the transmission loss of the transmission line in a simplified model was calculated. As the analysis method, a commercially available method of moments simulator Sonnet Lite(R) (manufactured by Sonnet Software Inc.) was used. The transmission line was a microstrip line (MSL). The analysis model is as follows. The copper wiring layer formed on one main surface of the glass substrate was defined to have a width (shown in Tables 9 to 12) such that the characteristic impedance of the line was 50 Ω, and the S-parameters (scattering parameter S21) at 1 GHz to 110 GHz were calculated. The surface roughness of the copper layer was set to be sufficiently smooth so that the skin effect would not be a problem. The calculated S21 (transmission characteristics) is shown in Figure 2. Also, the values of the signal transmission loss at 35 GHz and 110 GHz are shown in Tables 9 to 12.

[0087]

Table 9

[0088]

Table 10

[0089]

Table 11

[0090]

Table 12

[0091] As shown in FIG. 2 and Tables 9 to 12, according to the circuit boards using the glass substrates of Examples 1 to 3 and 7 to 25, compared with the circuit boards using the conventional soda-lime glass substrate of Example 4 and the conventional alkali-free glass substrate of Example 5, the transmission characteristics in the high-frequency region can be improved, and low transmission loss characteristics in the high-frequency region close to those of the circuit board using the conventional quartz glass substrate of Example 6 can be obtained. Since the quartz glass substrate of Example 6 has a small thermal expansion coefficient of 0.7 ppm / °C, when an electronic device is configured using it, the difference in thermal expansion coefficient from other members becomes large, and a practical electronic device cannot be provided. As shown in Example 5, even the so-called alkali-free glass substrate contains about 0.05 to 0.1% of an alkali component.

[0092] As an example of the ultraviolet transmittance, for the glass of Example 21, the transmittance values at wavelengths of 250, 300, and 350 nm at plate thicknesses of 0.5 mm and 1.0 mm when the content of Fe2O3 was changed were measured. The measurement results are shown in Table 13. The transmittance was measured using a visible ultraviolet spectrophotometer. From this, it can be seen that by adjusting the plate thickness and Fe2O3 content of the glass, the ultraviolet transmittance of the glass can be adjusted to a desired value.

[0093] [Table 13]

Industrial Applicability

[0094] The glass substrate for high-frequency devices of the present invention is excellent in the dielectric loss property of high-frequency signals. Further, a circuit board using such a glass substrate is excellent in the transmission loss property of high-frequency signals. Such a glass substrate and a circuit board are useful for all high-frequency electronic devices that handle high-frequency signals exceeding 10 GHz, particularly high-frequency signals exceeding 30 GHz, and further high-frequency signals of 35 GHz or more, for example, glass substrates of communication devices, frequency filter components such as SAW devices and FBARs, bandpass filters such as waveguides and SIW (Substrate Integrated waveguide) components, radar components, antenna components (particularly liquid crystal antennas optimized for satellite communication), and the like.

Explanation of Signs

[0095] 1... Circuit board, 2... Glass substrate, 2a, 2b... Main surfaces, 3, 4... Wiring layers.

Claims

1. Containing alkali metal oxides in a total content range of 0.001 to 5% in terms of molar percentage based on oxides, and among the alkali metal oxides, Na ２ O / (Na ２ O + K ２ O) has a molar ratio of 0.01 or more and 0.99 or less, and contains Al ２ O ３ and B ２ O ３ with a total content in the range of more than 13% and 40% or less, and the content of B ２ O ３ is 13 to 36%, and the molar ratio represented by Al ２ O ３ / (Al ２ O ３ + B ２ O ３ ) is in the range of more than 0 and 0.45 or less, and contains alkaline earth metal oxides in a total content range of 0.1 to 13%, and the content of MgO is in the range of 0.1 to 9%, a glass substrate mainly composed of SiO ２ , wherein the glass substrate has a transmittance of 90% or more at a wavelength of 350 nm, the average thermal expansion coefficient at 50 to 350 °C is in the range of 3 to 3.8 ppm / °C, and the dielectric loss tangent at 35 GHz is 0.007 or less, a glass substrate used for a high-frequency device that handles high-frequency signals of 10 GHz or more.

2. The glass substrate according to claim 1, having a relative permittivity of 5 or less at 35 GHz.

3. The molar ratio represented by the above Na ２ O / (Na ２ O + K ２ O) is 0.7 or more, the glass substrate according to claim 1 or 2.

4. The glass substrate according to claim 1 or 2, having a CaO content of 2 to 8% in terms of molar percentage based on oxides.

5. Al ２ O ３The glass substrate according to claim 1 or 2, wherein the content of is 0.5% or more.

6. In terms of molar percentage based on oxides, Fe ２ O ３ The glass substrate according to claim 1 or 2, wherein the content of Fe in terms of conversion is 0.012% or less.

7. The glass substrate according to claim 1 or 2, wherein the β-OH value is 0.05 mm －１ or more.

8. The thickness is in the range of 0.05 to 1 mm, and the substrate area is 225 to 10,000 cm ２ The glass substrate according to claim 1 or 2, which is in the range of.

9. The glass substrate according to claim 1 or 2, which is amorphous.

10. A circuit board comprising a glass substrate used for a high-frequency device that handles high-frequency signals of 10 GHz or more, and A wiring layer formed on the main surface of the glass substrate, wherein The glass substrate contains alkali metal oxides in a total content range of 0.001 to 5% in terms of molar percentage based on oxides, and among the alkali metal oxides, Na ２ O / (Na ２ O + K ２ O) has a molar ratio represented by 0.01 or more and 0.99 or less, contains Al ２ O ３ and B ２ O ３ and has a total content range of more than 13% and 40% or less, the content of B ２ O ３ is 13 to 36%, and Al ２ O ３ / (Al ２ O ３ + B ２ O ３The molar ratio represented by ) is in the range of more than 0 and 0.45 or less, and contains 0.1 to 13% as the total content of alkaline earth metal oxides, and the content of MgO is in the range of 0.1 to 9%, SiO ２ with as the main component, The glass substrate has a transmittance of 90% or more at a wavelength of 350 nm, The glass substrate has an average thermal expansion coefficient in the range of 3 to 3.8 ppm / °C at 50 to 350 °C, The glass substrate has a dielectric loss tangent of 0.007 or less at 35 GHz, A circuit board used for a high-frequency device that handles high-frequency signals of 10 GHz or more, with a transmission loss of 1 dB / cm or less at 35 GHz.

11. The conductor of the wiring layer is a metal, or an alloy or metal compound containing at least one of the metals, The metal is copper, gold, silver, aluminum, titanium, chromium, molybdenum, tungsten, platinum or nickel. The circuit board according to claim 10.

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