Alkali-free glass, glass substrate, and core material for electronic circuit board

Abstract

The present invention relates to an alkali-free glass having a content ratio, in terms of oxide-based mole percentage, satisfying: 45-70% of SiO2, 4-15% of Al2O3, 15-30% of B2O3, 0.1-10% of MgO, 0.1-10% of CaO, 0.1-10% of SrO, 0.3-10% of BaO, and a total of specific metal oxides of 0.2-35%, wherein the specific metal oxides are at least one selected from the group consisting of ZnO, SnO2, Sc2O3, TiO2, Ga2O3, ZrO2, Nb2O5, In2O3, HfO2, Ta2O5, WO3, Yb2O3, and Lu2O3, and wherein the ratio of content represented by [Al2O3] / [B2O3] is greater than 0.27.

Description

Alkali-free glass, glass substrates, and core materials for electronic circuit boards

[0001] This invention relates to alkali-free glass, glass substrates, and core materials for electronic circuit boards.

[0002] An electronic circuit board is a substrate on which an electronic circuit is formed by creating a circuit pattern on a PCB (Printed Circuit Board) for arranging and connecting electronic components, and then mounting electronic components on top of that pattern. An example of such a PCB board is a CPO (Copper Plating on ODL: On-Dieelectric Layer) module substrate to which copper plating technology is applied.

[0003] While the wiring spacing on a CPO module board is several tens of micrometers, the wiring spacing in an interposer that electrically connects IC chips can be as low as 1 micrometer, or even on the order of nanometers. Thus, it is difficult to narrow the wiring spacing by directly connecting two components with such different orders of magnitude.

[0004] Therefore, a glass cloth, which is a glass fiber containing a resin composition, is used as a substrate, and a substrate with a wiring spacing of about 5 to 20 μm is interposed between the CPO module substrate and the interposer. This allows the CPO module substrate and the interposer to be connected effectively.

[0005] In response to this, in recent years there has been a demand to mount even more IC chips on electronic circuit boards and to integrate them. However, it is difficult to increase the surface area of ​​the glass cloth substrate mentioned above. This is because the Young's modulus (rigidity) of glass cloth is not very high to begin with, and due to its high expansion rate, it is prone to peeling due to the heat generated by the IC chips.

[0006] Therefore, recently, a technology that utilizes glass material as a core material for electronic circuit boards, known as a glass core, has been attracting attention. Compared to glass cloth substrates as described above, glass has higher rigidity and is more heat resistant.

[0007] In addition to the above, glass cores are also required to have good electrical properties. For example, dielectric loss tangent in the high-frequency range is one of the important material properties; a low dielectric loss tangent means that less electricity is lost during electrical signal communication. Relative permittivity is also an important material property; if the relative permittivity is too high, the wiring spacing on the device becomes too narrow, making it difficult to properly fabricate the device.

[0008] As a glass suitable for glass cores with such excellent electrical properties, Patent Document 1 discloses an alkali-free glass that satisfies a specific composition range.

[0009] International Publication No. 2020 / 209271

[0010] In addition to the electrical properties mentioned above, the glass used in the glass core also requires good metallization properties. Metallization properties refer to adhesion to electrodes. Specifically, for example, when copper electrodes are used, the copper electrodes need to be wired to the glass. When a glass cloth containing resin is used as the substrate, the uneven surface of the glass cloth makes it easy for the copper electrodes to adhere to the glass cloth substrate. On the other hand, glass has a smooth surface, resulting in poor adhesion to copper electrodes. Furthermore, even when attempting to wire copper electrodes to glass via an adhesion layer of metal oxide, the desired adhesion could not be achieved.

[0011] Therefore, the present invention aims to provide a glass that possesses the electrical properties required for a glass core while also having high adhesion to electrodes. Furthermore, the present invention also aims to provide a glass substrate and a core material for electronic circuit boards using the above-mentioned glass.

[0012] The inventors realized that when wiring electrodes to glass via a metal oxide adhesion layer, high adhesion between the glass and the metal constituting the electrode can be achieved if the ionic radii of the metal ions contained in the glass and the metal ions of the metal oxide constituting the adhesion layer are close. Furthermore, they found that the above objective can be achieved by adopting a specific glass composition that also achieves good electrical properties.

[0013] That is, the gist of one embodiment of the present invention is as follows. [1] The content ratio in mole percentage based on oxide is: SiO ２ 45 to 70%, Al ２ O ３ 4 to 15%, B ２ O ３ 15 to 30%, MgO 0.1 to 10%, CaO 0.1 to 10%, SrO 0.1 to 10%, BaO 0.3 to 10%, and the total of specific metal oxides satisfies 0.2 to 35%, wherein the specific metal oxides are ZnO, SnO ２ , Sc ２ O ３ , TiO ２ , Ga ２ O ３ , ZrO ２ , Nb ２ O ５ , In ２ O ３ , HfO ２ , Ta ２ O ５ , WO ３ , Yb ２ O ３ , and Lu ２ O ３ is at least one selected from the group consisting of, and the ratio of the content ratio represented by [Al ２ O ３ / [B ２ O ３ is more than 0.27. An alkali-free glass. [2] The alkali-free glass according to [1], wherein the content ratio in mole percentage based on oxide further satisfies a total of 0.2 to 12% of the specific metal oxides. [3] The alkali-free glass according to [1] or [2], wherein a haze value when the plate thickness is 1 mm is 10% or less. [4] The alkali-free glass according to any one of [1] to [3], wherein a dielectric loss tangent at 10 GHz is 0.006 or less. [5] The alkali-free glass according to any one of [1] to [4], wherein a relative dielectric constant at 10 GHz is 6 or less.

[0014] [6] A glass substrate having a pair of opposing main surfaces and end surfaces, wherein the glass constituting the glass substrate is the alkali-free glass described in any one of [1] to [5] above. [7] The glass substrate according to [6], having through holes in the thickness direction, wherein the surface of the glass substrate including the side walls of the through holes is covered with an adhesion layer of metal oxide. [8] The metal oxide constituting the adhesion layer is ZnO and SnO ２ A glass substrate according to [7], wherein at least one of the above. [9] A glass substrate according to [7] or [8], wherein the through hole is tapered from one main surface of the glass substrate to the other main surface.

[10] A glass substrate according to any one of [6] to [9], wherein the arithmetic mean roughness Ra of at least one of the pair of main surfaces is 1.5 nm or less.

[11] A glass substrate according to any one of [6] to

[10] , used as a core material for an electronic circuit board.

[0015]

[12] A core material for an electronic circuit board comprising glass, an adhesion layer of a metal oxide, and an electrode, wherein the glass is an alkali-free glass according to any one of [1] to [5] above, the glass has through holes in the thickness direction of the core material, the surface of the glass including the through holes is covered with the adhesion layer, and through electrodes which will be the electrodes are wired to the through holes via the adhesion layer.

[13] The metal oxide constituting the adhesion layer is ZnO and SnO ２ A core material for an electronic circuit board according to

[12] , which is at least one of the above.

[14] A core material for an electronic circuit board according to

[12] or

[13] , wherein the through hole is tapered.

[15] A core material for an electronic circuit board according to any one of

[12] to

[14] , wherein the through electrode is a copper electrode.

[0016] The alkali-free glass according to this embodiment possesses the electrical properties required for a glass core while also exhibiting high adhesion to electrodes. Specifically, because the alkali-free glass according to this embodiment can achieve low dielectric loss, it can reduce losses when electricity flows, and because it can achieve a low relative permittivity, it can reduce crosstalk due to capacitive coupling even when the wiring spacing of electrodes is narrowed. In addition to the above, because the alkali-free glass according to this embodiment has high adhesion to electrodes, it can contribute to the manufacture of highly reliable electronic devices. The same applies to the glass substrate and core material for electronic circuit boards according to this embodiment.

[0017] Embodiments of the present invention will be described below. In the following description, numerical ranges indicated using "~" indicate a range that includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively. Unless otherwise specified, the content ratios of each component of glass in alkali-free glass, glass substrates, and core materials are expressed as mole percentages (mol%) based on oxides. Also, the notation [metal oxide], for example [Al ２ O ３ The notations such as "[ ]" indicate the content percentage in mole percent of metal oxide components, such as aluminum oxide. In this specification, "high frequency" means 10 GHz or higher.

[0018] The alkali-free glass according to this embodiment (hereinafter sometimes simply referred to as "glass") will be described below. <Alkali-free glass> The alkali-free glass according to this embodiment satisfies the following content ratio in molar percentage based on oxides: SiO ２ 45-70%, Al ２ O ３ 4-15%, B ２ O ３ 15-30%, MgO 0.1-10%, CaO 0.1-10%, SrO 0.1-10%, BaO 0.3-10%, total of specific metal oxides 0.2-35%, and [Al ２ O ３ ] / [B ２ O ３ ] Greater than 0.27. Here, the specific metal oxides mentioned above are ZnO, SnO２ , Sc ２ O ３ , TiO ２ Ga ２ O ３ , ZrO ２ , Nb ２ O ５ In ２ O ３ , HfO ２ Ta ２ O ５ WO ３ Yb ２ O ３ , and Lu ２ O ３ It is at least one selected from the group consisting of the following:

[0019] In this specification, alkali-free glass means glass that does not substantially contain alkali metal oxides. Here, alkali metal oxide refers to Li ２ O, Na ２ O, K ２ O, Rb ２ O, Cs ２ This refers to O. "Substantially free of alkali metal oxides" means that, apart from impurities introduced from raw materials, etc., alkali metal oxides are not present; in other words, they are intentionally omitted. Specifically, the total content of alkali metal oxides in molar percentages based on oxides is preferably 0.1% or less.

[0020] As described above, the glass core possesses the electrical properties required for a glass core while also exhibiting high adhesion to the electrode. The inventors have found that, in relation to high adhesion to the electrode, it is important to include a specific metal oxide whose ionic radius is close to that of the metal ions of the metal oxide constituting the adhesion layer interposed between the glass and the electrode.

[0021] Specifically, the ionic radii of metal ions constituting metal oxides commonly used as adhesion layers are approximately 0.65 to 0.78 Å. In contrast, it has been found that good adhesion can be achieved by including a certain amount or more of metal oxides with metal ions having a similar ionic radius. Specifically, it has been found that good adhesion can be achieved by including metal oxides with ionic radii of approximately 0.55 to 0.88 Å in the glass. The reason for this is not entirely clear, but it is thought that while the adhesion layer chemically binds to the electrode as a buffer, the presence of metal ions in the glass with similar ionic radii to those in the adhesion layer causes some kind of interaction between the adhesion layer and the glass.

[0022] <Specific Metal Oxides> In this specification, metal oxides that improve adhesion as described above and are contained in the glass according to this embodiment are referred to as "specific metal oxides." Specifically, the above-mentioned specific metal oxides are ZnO, SnO ２ , Sc ２ O ３ , TiO ２ Ga ２ O ３ , ZrO ２ , Nb ２ O ５ In ２ O ３ , HfO ２ Ta ２ O ５ WO ３ Yb ２ O ３ , and Lu ２ O ３ It is at least one selected from the group consisting of the following:

[0023] Here, the ionic radii of the metal ions constituting the specific metal oxide described above are as follows. Zn (6-coordinate): 0.74Å, Sn (6-coordinate): 0.69Å, Sc (6-coordinate): 0.745Å, Ti (6-coordinate): 0.605Å, Ga (6-coordinate): 0.620Å, Zr (4-coordinate): 0.590Å, Nb (6-coordinate): 0.640Å, In (6-coordinate): 0.800Å, Hf (6-coordinate): 0.710Å, Ta (6-coordinate): 0.640Å, W (6-coordinate): 0.600Å, Yb (6-coordinate): 0.868Å, Lu (6-coordinate): 0.861Å.

[0024] In the present embodiment, the total content of the specific metal oxide is 0.2 to 35%.

[0025] The alkali-free glass according to the present embodiment includes, as the aforementioned specific metal oxide, ZnO, SnO ２ , Sc ２ O ３ , TiO ２ , Ga ２ O ３ , ZrO ２ , Nb ２ O ５ , In ２ O ３ , HfO ２ , Ta ２ O ５ , WO ３ , Yb ２ O ３ , and Lu ２ O ３It is preferable to include at least one selected from the group consisting of the above, and more preferably to include them in total at a concentration of 0.2 to 35%. From the viewpoint of good adhesion to the electrode, the total content is preferably 0.2% or more, more preferably 0.5% or more, even more preferably 0.7% or more, even more preferably 1.0% or more, especially preferably 1.5% or more, and particularly preferably 2.0% or more. Furthermore, from the viewpoint of obtaining good electrical properties, the total content is 35% or less, preferably 25% or less, more preferably 20% or less, and from the viewpoint of suppressing devitrification due to crystallization and phase separation of the glass and obtaining high transparency, it is preferably less than 15%, more preferably 12% or less, even more preferably 10% or less, even more preferably 7% or less, and particularly preferably 5% or less.

[0026] The alkali-free glass according to this embodiment uses ZnO and SnO as the specific metal oxides. ２ , Sc ２ O ３ , TiO ２ Ga ２ O ３ In ２ O ３ , HfO ２ , and Ta ２ O ５ It is more preferable to include at least one selected from the group consisting of the above, and even more preferable to include them in total at a concentration of 0.2 to 35%. From the viewpoint of good adhesion to the electrode, the total content is preferably 0.2% or more, more preferably 0.5% or more, even more preferably 0.7% or more, even more preferably 1.0% or more, especially preferably 1.5% or more, and particularly preferably 2.0% or more. Furthermore, from the viewpoint of obtaining good electrical properties, the total content is 35% or less, preferably 25% or less, more preferably 20% or less, and from the viewpoint of suppressing devitrification due to crystallization and phase separation of the glass and obtaining high transparency, it is preferably less than 15%, more preferably 12% or less, even more preferably 10% or less, even more preferably 7% or less, and particularly preferably 5% or less.

[0027] When the alkali-free glass according to this embodiment contains ZnO as a specific metal oxide, the total content of the specific metal oxide is not particularly limited, as long as it is between 0.2% and 35%. The ZnO content is preferably 0.2% to 35%, and more preferably 0.5% to 5%. Here, from the viewpoint of good adhesion to the electrode, the ZnO content is preferably 0.2% or more, more preferably 0.5% or more, even more preferably 0.7% or more, even more preferably 1.0% or more, especially preferably 1.5% or more, and particularly preferably 2.0% or more. Furthermore, from the viewpoint of suppressing devitrification due to crystallization and phase separation of the glass and obtaining high transparency, the ZnO content is preferably 35% or less, more preferably 15% or less, even more preferably 12% or less, even more preferably 10% or less, especially preferably 7% or less, and particularly preferably 5% or less.

[0028] In this embodiment, the alkali-free glass is SnO as a specific metal oxide. ２ If it contains, the total content of specific metal oxides is not particularly limited as long as it is between 0.2% and 35%, but SnO ２ The content ratio is preferably, for example, 0.2 to 35%, and more preferably 0.5 to 5%. Here, from the viewpoint of good adhesion with the electrode, SnO ２ The content of is preferably 0.2% or more, more preferably 0.5% or more, even more preferably 0.7% or more, even more preferably 1.0% or more, especially preferably 1.5% or more, and particularly preferably 2.0% or more. In addition, from the viewpoint of suppressing devitrification due to crystallization and phase separation of the glass and obtaining high transparency, SnO ２ The content ratio is preferably 35% or less, more preferably 15% or less, even more preferably 12% or less, even more preferably 10% or less, especially preferably 7% or less, and particularly preferably 5% or less.

[0029] The alkali-free glass according to this embodiment is Sc as a specific metal oxide. ２ O ３ , TiO ２ Ga ２ O ３ , ZrO ２ , Nb ２ O ５ In２ O ３ , HfO ２ Ta ２ O ５ WO ３ Yb ２ O ３ , and Lu ２ O ３ When the material contains at least one metal oxide selected from the group consisting of the above, the content of each metal oxide is not particularly limited as long as the total content of the specific metal oxides is 0.2 to 35%. For example, the content of each of the above metal oxides is preferably 0.2 to 35%, and more preferably 0.5 to 5%. Here, from the viewpoint of good adhesion to the electrode, the content of each of the above metal oxides is preferably 0.2% or more, more preferably 0.5% or more, even more preferably 0.7% or more, even more preferably 1.0% or more, especially preferably 1.5% or more, and particularly preferably 2.0% or more. Also, from the viewpoint of obtaining high transparency, the content of each of the above metal oxides is preferably 35% or less, more preferably 15% or less, even more preferably 12% or less, even more preferably 10% or less, especially preferably 7% or less, and particularly preferably 5% or less.

[0030] <SiO ２ > The alkali-free glass according to this embodiment is SiO ２ It contains 45-70% of it, with a preferred content of 47.5-68%. Here, from the viewpoint of good glass formation ability, weather resistance, and devitrification suppression, SiO ２ The content of is 45% or more, preferably 47.5% or more, more preferably 50% or more, even more preferably 55% or more, even more preferably 57.5% or more, and particularly preferably 59% or more. Also, from the viewpoint of solubility, SiO ２ The content ratio is 70% or less, preferably 68% or less, more preferably 66% or less, even more preferably 65% ​​or less, even more preferably 64% or less, and particularly preferably 62% or less.

[0031] <Al ２ O ３ > The alkali-free glass according to this embodiment is Al ２ O ３It contains 4 to 15% of it, with a preferred content of 4.1 to 13%. Here, from the viewpoint of good weather resistance, Young's modulus, suppression of phase separation, and reduction of the coefficient of thermal expansion, Al ２ O ３ The content of is 4% or more, preferably 4.1% or more, more preferably 4.2% or more, even more preferably 4.5% or more, even more preferably 5.0% or more, and particularly preferably 5.5% or more. Also, from the viewpoint of solubility, Al ２ O ３ The content is 15% or less, preferably 13% or less, more preferably 12% or less, even more preferably 11% or less, even more preferably 10% or less, and particularly preferably 8.5% or less.

[0032] <B ２ O ３ > The alkali-free glass according to this embodiment is B ２ O ３ It contains 15-30% of it, and the content ratio is preferably 16-28%. Here, from the viewpoint of solubility and dielectric loss tangent in the high frequency range, B ２ O ３ The content of is 15% or more, preferably 16% or more, more preferably 17% or more, even more preferably 18% or more, even more preferably 19% or more, especially preferably 20% or more, and particularly preferably 20.5% or more. Also, from the viewpoint of chemical resistance, B ２ O ３ The content of is 30% or less, preferably 28% or less, more preferably 26% or less, even more preferably 25% or less, even more preferably 24% or less, and particularly preferably 23% or less.

[0033] <MgO> The alkali-free glass according to this embodiment contains 0.1 to 10% MgO, with a preferred content of 0.2 to 8.0%. Here, in addition to solubility, from the viewpoint of increasing the specific modulus and improving the fracture toughness value to increase the glass strength, the MgO content is 0.1% or more, preferably 0.2% or more, more preferably 0.5% or more, even more preferably 0.7% or more, even more preferably 1.0% or more, and particularly preferably 1.2% or more. Furthermore, from the viewpoint of suppressing the rise in devitrification temperature, the MgO content is 10% or less, preferably 8.0% or less, more preferably 6.0% or less, even more preferably 5.0% or less, even more preferably 4.0% or less, and particularly preferably 3.0% or less.

[0034] <CaO> The alkali-free glass according to this embodiment contains 0.1 to 10% CaO, with a preferred content of 0.2 to 8.0%. CaO has the characteristic of having the second highest specific modulus among alkaline earth metals after MgO, and does not excessively lower the strain point, and like MgO, it is a component that also improves solubility. Furthermore, it has the characteristic of not raising the devitrification temperature as much as MgO. From this viewpoint, the CaO content is 0.1% or more, preferably 0.2% or more, more preferably 0.5% or more, even more preferably 0.7% or more, even more preferably 1.0% or more, and particularly preferably 1.2% or more. Furthermore, from the viewpoint of preventing the average thermal expansion coefficient from becoming too high and suppressing the rise in devitrification temperature to prevent devitrification during glass manufacturing, the CaO content is 10% or less, preferably 8.0% or less, more preferably 6.0% or less, even more preferably 4.0% or less, even more preferably 3.0% or less, and particularly preferably 2.0% or less.

[0035] <SrO> The alkali-free glass according to this embodiment contains 0.1 to 10% SrO, with a preferred content of 1.0 to 9.5%. Here, from the viewpoint of improving solubility without raising the devitrification temperature of the glass, the SrO content is 0.1% or more, preferably 1.0% or more, more preferably 2.0% or more, even more preferably 3.0% or more, even more preferably 4.0% or more, and particularly preferably 5.0% or more. Furthermore, from the viewpoint of preventing the average thermal expansion coefficient from becoming too high without increasing the specific gravity too much, the SrO content is 10% or less, preferably 9.5% or less, more preferably 9.0% or less, even more preferably 8.5% or less, even more preferably 8.0% or less, and particularly preferably 7.5% or less.

[0036] <BaO> The alkali-free glass according to this embodiment contains 0.3 to 10% BaO, with a preferred content of 0.5 to 8.0%. Here, from the viewpoint of improving solubility without raising the devitrification temperature, the BaO content is 0.3% or more, preferably 0.5% or more, more preferably 0.7% or more, even more preferably 0.8% or more, even more preferably 0.9% or more, and particularly preferably 1.0% or more. Furthermore, from the viewpoint of specific gravity, Young's modulus, relative permittivity, average thermal expansion coefficient, etc., the BaO content is 10% or less, preferably 8.0% or less, more preferably 7.0% or less, even more preferably 5.0% or less, even more preferably 4.0% or less, and particularly preferably 3.0% or less.

[0037] <[Al ２ O ３ ] / [B ２ O ３ ]> The alkali-free glass according to this embodiment, [Al ２ O ３ ] / [B ２ O ３The ratio of the content represented by ] is greater than 0.27, and preferably greater than 0.27 and 0.6 or less. Here, from the viewpoint of reducing dielectric loss in the high-frequency region exceeding 10 GHz, acid resistance, and phase splitting suppression, the above ratio is greater than 0.27, preferably 0.28 or more, more preferably 0.29 or more, even more preferably 0.3 or more, even more preferably 0.31 or more, and particularly preferably 0.32 or more. Also, from the viewpoint of improving Young's modulus, the above ratio is preferably 0.33 or more, more preferably 0.34 or more, even more preferably 0.35 or more, even more preferably 0.36 or more, and particularly preferably 0.37 or more. On the other hand, from the viewpoint of reducing dielectric loss, the above ratio is preferably 0.6 or less, more preferably 0.55 or less, even more preferably 0.5 or less, even more preferably 0.45 or less, especially preferably 0.42 or less, and particularly preferably 0.4 or less.

[0038] <[MgO] + [CaO] + [SrO] + [BaO]> The total content of [MgO] + [CaO] + [SrO] + [BaO] in the alkali-free glass according to this embodiment is preferably 0.6 to 35%. Here, from the viewpoint of lowering the resistance value in the melting temperature range, the total content is preferably 0.6% or more, more preferably 3% or more, even more preferably 5% or more, even more preferably 6% or more, and particularly preferably 7.5% or more. Furthermore, from the viewpoint of acid resistance and dielectric loss in the high frequency range above 10 GHz, the total content is preferably 35% or less, more preferably 25% or less, even more preferably 20% or less, even more preferably 15% or less, and particularly preferably 10% or less.

[0039] <[Al ２ O ３ ]-([MgO]+[CaO]+[SrO]+[BaO])> The alkali-free glass according to this embodiment, [Al ２ O ３The difference in content expressed as ]-([MgO]+[CaO]+[SrO]+[BaO]) is preferably -20 to 10%. Here, from the viewpoint of acid resistance, the above difference is preferably -20% or more, more preferably -15% or more, even more preferably -10% or more, even more preferably -7.5% or more, and particularly preferably -5.0% or more. Furthermore, from the viewpoint of suppressing glass devitrification, the above difference is preferably 10% or less, more preferably 8% or less, even more preferably 6% or less, even more preferably 5% or less, and particularly preferably 3% or less.

[0040] <[SrO] / ([MgO]+[CaO]+[SrO]+[BaO])> The ratio of the alkali-free glass according to this embodiment, expressed as [SrO] / ([MgO]+[CaO]+[SrO]+[BaO]), is preferably 0.1 or higher, and more preferably 0.1 to 0.9. Here, from the viewpoint of lowering the surface devitrification temperature and improving productivity, the above ratio is preferably 0.1 or higher, more preferably 0.2 or higher, even more preferably 0.3 or higher, even more preferably 0.5 or higher, and particularly preferably 0.7 or higher. Furthermore, there is no particular upper limit, but for example, it may be 0.9 or lower.

[0041] Thus, the alkali-free glass according to this embodiment is SiO ２ 45-70%, Al ２ O ３ 4-15%, B ２ O ３ 15-30%, MgO 0.1-10%, CaO 0.1-10%, SrO 0.1-10%, BaO 0.3-10%, and [Al ２ O ３ ] / [B ２ O ３ By satisfying a content ratio of more than 0.27 as expressed by [ ], the material will have at least the electrical properties required for a glass core. Furthermore, by satisfying a total content of 0.2 to 35% of specific metal oxides, high adhesion to the electrodes can also be achieved.

[0042] The alkali-free glass according to this embodiment is SiO ２ 50-65%, Al ２ O ３ 4-10%, B ２ O３ 20-25%, MgO 0.1-5.0%, CaO 0.1-6.0%, SrO 0.1-8.0%, BaO 0.3-7.0%, and [Al ２ O ３ ] / [B ２ O ３ It is more preferable that the ratio of the content percentages represented by [ ] is greater than 0.27 and less than or equal to 0.45, and even more preferable that the total amount of specific metal oxides is 0.2 to 10%.

[0043] <Other Optional Components> The alkali-free glass according to this embodiment may contain other optional components, as long as they do not impair the effects of the present invention. Other optional components include, for example, P ２ O ５ Fe ２ O ３ SO ３ Cl, F, MoO ３ , Pt, Rh ２ O ３ These are some examples. However, optional components are not limited to these.

[0044] Furthermore, the glass according to this embodiment is alkali-free glass, and as mentioned above, it is preferable that the total content of alkali metal oxides in molar percentages based on oxides is 0.1% or less.

[0045] When alkali metal oxides are intentionally included, the glass according to this embodiment contains Li ２ O, Na ２ O and K ２ The total content of O may be expressed as a mole percentage based on the oxide, for example, 0.001 to 0.2%. Here, from the viewpoint of suitably obtaining the effects of alkali metal oxides, the total content may be 0.001% or more, 0.003% or more, 0.005% or more, 0.008% or more, 0.01% or more, or 0.02% or more. Furthermore, from the viewpoint of preventing alkali metals from moving when an electric field is applied to the glass, the total content may be 0.2% or less, 0.15% or less, 0.1% or less, 0.08% or less, 0.05% or less, or 0.03% or less.

[0046] P２ O ５ Although it is an optional component, if it is included, its content is preferably more than 0% and 10% or less. Here, from the viewpoint of improving solubility, P ２ O ５ When it contains, the content is preferably more than 0%, more preferably 0.5% or more, even more preferably 1.0% or more, even more preferably 1.5% or more, especially preferably 2.0% or more, and particularly preferably 3.0% or more. Also, from the viewpoint of weather resistance, P ２ O ５ The content of is preferably 10% or less, more preferably 9.0% or less, even more preferably 8.0% or less, even more preferably 7.0% or less, especially preferably 6.0% or less, and particularly preferably 5.0% or less.

[0047] Fe ２ O ３ Although it is an optional component, if it is included, its content is preferably more than 0% and 1.0% or less. Here, from the viewpoint of lowering the resistance value in the melting temperature range, Fe ２ O ３ When it contains, the content is preferably more than 0%, more preferably 0.01% or more, even more preferably 0.03% or more, even more preferably 0.05% or more, especially preferably 0.07% or more, and particularly preferably 0.1% or more. Also, from the viewpoint of transparency, Fe ２ O ３ The content of is preferably 1.0% or less, more preferably 0.9% or less, even more preferably 0.8% or less, even more preferably 0.7% or less, especially preferably 0.6% or less, even more preferably 0.5% or less, particularly preferably 0.3% or less, and most preferably 0.15% or less.

[0048] SO ３ SO is an optional component, but if included, its content is preferably 0.001 to 0.5%. Here, from the viewpoint of clarity, ３If it contains, the content is preferably 0.001% or more, more preferably 0.002% or more, even more preferably 0.003% or more, even more preferably 0.004% or more, especially preferably 0.005% or more, and particularly preferably 0.006% or more. Also, from the viewpoint of preventing the raw materials from overflowing due to an excessive increase in bubbles in the glass, SO ３ The content of is preferably 0.5% or less, more preferably 0.45% or less, even more preferably 0.40% or less, even more preferably 0.35% or less, especially preferably 0.33% or less, and particularly preferably 0.30% or less.

[0049] Cl is an optional component, but if included, its content is preferably 0.001 to 0.5%. Here, from the viewpoint of clarity, if Cl is included, its content is preferably 0.001% or more, more preferably 0.002% or more, even more preferably 0.003% or more, even more preferably 0.004% or more, especially preferably 0.005% or more, and particularly preferably 0.006% or more. Furthermore, from the viewpoint of preventing the raw materials from overflowing due to excessive bubbles in the glass, the Cl content is preferably 0.5% or less, more preferably 0.45% or less, even more preferably 0.40% or less, even more preferably 0.35% or less, especially preferably 0.33% or less, and particularly preferably 0.30% or less. Note that the Cl content refers to the proportion in cation form.

[0050] F is an optional component, but if it is included, its content is preferably 0.001 to 0.5%. Here, from the viewpoint of clarity, if F is included, its content is preferably 0.001% or more, more preferably 0.002% or more, even more preferably 0.003% or more, even more preferably 0.004% or more, especially preferably 0.005% or more, and particularly preferably 0.006% or more. Also, from the viewpoint of preventing the raw materials from overflowing due to excessive bubbles in the glass, the content of F is preferably 0.5% or less, more preferably 0.45% or less, even more preferably 0.40% or less, even more preferably 0.35% or less, especially preferably 0.33% or less, and particularly preferably 0.30% or less.

[0051] SnO２ Although it is an optional component, SnO ２ It can also be used as a clarifying agent. When included as a clarifying agent, its content is preferably 0.001 to 0.5%. Here, from the viewpoint of clarity, SnO ２ If it contains, the content is preferably 0.001% or more, more preferably 0.002% or more, even more preferably 0.003% or more, even more preferably 0.004% or more, especially preferably 0.005% or more, and particularly preferably 0.006% or more. Also, from the viewpoint of preventing the raw materials from overflowing due to an excessive increase in bubbles in the glass, SnO ２ The content of is preferably 0.5% or less, more preferably 0.45% or less, even more preferably 0.40% or less, even more preferably 0.35% or less, especially preferably 0.33% or less, and particularly preferably 0.30% or less.

[0052] MoO ３ Although it is an optional component, if it is included, its content is preferably 0.0001 to 0.5%. Here, from the viewpoint of meltability and moldability, MoO ３ If it contains, the content is preferably 0.0001% or more, more preferably 0.0002% or more, even more preferably 0.0003% or more, even more preferably 0.0004% or more, especially preferably 0.0005% or more, and particularly preferably 0.0006% or more. Also, from the viewpoint of preventing the raw materials from overflowing due to an excessive increase in bubbles in the glass, MoO ３ The content of is preferably 0.05% or less, more preferably 0.045% or less, even more preferably 0.040% or less, even more preferably 0.035% or less, especially preferably 0.033% or less, and particularly preferably 0.03% or less.

[0053] When the alkali-free glass according to this embodiment is used as a glass substrate for a core material of an electronic circuit board, it is preferable that it has good poromachinability. Poromachinability refers to the ease with which through holes for wiring electrodes can be formed in the thickness direction of the substrate.

[0054] When the above-mentioned through-holes are formed by alteration by laser irradiation followed by immersion in a chemical solution, high transparency of the alkali-free glass is important. From this viewpoint, it is sufficient for the alkali-free glass according to this embodiment to have a haze value of 10% or less when the plate thickness is 1 mm. Furthermore, from the viewpoint of reducing high-frequency signal transmission loss by ensuring high uniformity of the glass and suitably preventing localized irregularities on the substrate surface when the glass substrate is acid-cleaned, for example, the above-mentioned haze value may be 1.0% or less, 0.8% or less, 0.5% or less, or 0.4% or less. Also, the lower limit is not particularly limited and may be 0%, or 0.1% or more. Note that the haze value in this specification is a value measured in accordance with JIS K 7136:2000.

[0055] In this embodiment, the dielectric loss tangent (tanδ) at 10 GHz of the alkali-free glass is preferably 0.006 or less, more preferably 0.005 or less, even more preferably 0.004 or less, even more preferably 0.0038 or less, especially preferably 0.0035 or less, particularly preferably 0.003 or less, and the smaller the value, the better.

[0056] In this embodiment, the dielectric loss tangent (tanδ) at 35 GHz is preferably 0.007 or less, more preferably 0.0065 or less, even more preferably 0.0055 or less, even more preferably 0.0050 or less, especially preferably 0.0045 or less, particularly preferably 0.004 or less, and the smaller the value, the better, from the viewpoint of suitably reducing dielectric loss in high-frequency regions exceeding 30 GHz.

[0057] In this embodiment, the relative permittivity of the alkali-free glass at 10 GHz is preferably 6 or less, more preferably 5.5 or less, even more preferably 5.4 or less, even more preferably 5.3 or less, especially preferably 5 or less, particularly preferably 4.9 or less, and the smaller the value, the better.

[0058] In this embodiment, the relative permittivity of the alkali-free glass at 35 GHz is preferably 10 or less, more preferably 7 or less, even more preferably 6 or less, particularly preferably 5 or less, and the smaller the value, the better, from the viewpoint of suitably reducing dielectric loss in the high-frequency range.

[0059] When the alkali-free glass according to this embodiment is used as a glass substrate for a core material of an electronic circuit board, it is preferable that it has a certain level of rigidity. From the viewpoint of preventing warping, bending, cracking, etc. of the substrate, the Young's modulus is preferably 58 GPa or higher, more preferably 60 GPa or higher, even more preferably 62 GPa or higher, even more preferably 63 GPa or higher, especially preferably 64 GPa or higher, even more preferably 65 GPa or higher, particularly preferably 66 GPa or higher, especially preferably 67 GPa or higher, and most preferably 68 GPa or higher. There is no particular upper limit to the Young's modulus, but for example, it may be 90 GPa or lower.

[0060] The alkali-free glass according to this embodiment has a glass viscosity of 10 ２ Temperature T at which dPa·s occurs ２ The temperature is preferably 1700°C or lower, and more preferably 1500 to 1700°C. Here, the above T ２ From the viewpoint of reducing kiln-derived defects such as pitting and Zr defects, and extending the lifespan of equipment by reducing the burden on manufacturing equipment due to improved solubility, a temperature of 1700°C or lower is preferred, more preferably 1680°C or lower, even more preferably 1670°C or lower, even more preferably 1665°C or lower, especially preferably 1660°C or lower, and particularly preferably 1650°C or lower. ２ The lower limit is not particularly limited, but it may be, for example, 1500°C or higher.

[0061] The alkali-free glass according to this embodiment has a glass viscosity of 10 ４ Temperature T at which dPa·s occurs ４ The temperature is preferably 1290°C or lower, and more preferably 1050 to 1290°C. Here, from the viewpoint of moldability, reduction of glass defects caused by volatile substances in the atmosphere due to the decrease in temperature during molding, and reduction of the burden on manufacturing equipment, the above T ４The temperature is preferably 1290°C or lower, more preferably 1280°C or lower, even more preferably 1270°C or lower, even more preferably 1260°C or lower, especially preferably 1250°C or lower, and particularly preferably 1240°C or lower. ４ The lower limit is not particularly limited, but it may be, for example, 1050°C or higher.

[0062] Note that T in this specification ２ and T ４ The viscosity was measured using a rotational viscometer in accordance with the method specified in ASTM C 965-96, and 10 ２ d・Pa・s or 10 ４ It can be determined as the temperature when the temperature is d・Pa・s.

[0063] The surface devitrification temperature of the alkali-free glass according to this embodiment is preferably 1300°C or lower, and may be 1000 to 1300°C. Here, from the viewpoint of moldability, suppression of crystal formation inside the glass during molding which reduces transmittance, and reduction of equipment burden, the surface devitrification temperature is preferably 1300°C or lower, and is preferably in the following order: 1295°C or lower, 1290°C or lower, 1285°C or lower, 1280°C or lower, 1275°C or lower, 1270°C or lower, 1265°C or lower, 1260°C or lower, 1255°C or lower, 1250°C or lower, 1245°C or lower, 1240°C or lower, 1235°C or lower, 1230°C or lower, 1225°C or lower, 1220°C or lower, 1215°C or lower, 1210°C or lower, 1205°C or lower, and 1200°C or lower. Furthermore, the lower limit of the surface devitrification temperature is not particularly limited, but may be, for example, 1000°C or higher.

[0064] In this specification, the surface devitrification temperature is determined as follows: Crushed glass particles are placed in a platinum dish and heat-treated for 17 hours in an electric furnace controlled to a constant temperature. After the heat treatment, the highest temperature at which crystals precipitate on the glass surface and the lowest temperature at which crystals do not precipitate are observed using an optical microscope, and the average value of these is defined as the surface devitrification temperature.

[0065] As an indicator of the acid resistance of alkali-free glass according to this embodiment, HNO ３ 6% by weight, and H ２ SO ４The amount of glass components eluted per unit surface area when glass is immersed for 170 seconds in an aqueous solution containing 5% by weight at 45°C is given as follows: 0.025 mg / cm². ２ The following is preferable as it indicates good acid resistance, and the above elution amount is 0.020 mg / cm³. ２ The following are more preferable, and the fewer the better.

[0066] The alkali-free glass according to this embodiment preferably has a resistance value of 400 Ω·cm or less at 1500°C for total electromelting, and may be between 10 and 400 Ω·cm. If the resistance value at 1500°C is within the above range, melting by electric heating is possible during glass manufacturing. The resistance value at 1500°C is more preferably 300 Ω·cm or less, even more preferably 250 Ω·cm or less, and even more preferably 200 Ω·cm or less. The lower limit is not particularly limited, but it should be 10 Ω·cm or more.

[0067] The method for manufacturing alkali-free glass according to this embodiment is not particularly limited and can be manufactured by conventionally known methods. For example, it may include a melting step of heating glass raw materials to obtain molten glass, a clarification step of removing bubbles from the molten glass, and a cooling step of the molten glass. Furthermore, if a plate-shaped glass substrate is to be obtained, the cooling step of the molten glass may include a molding step of forming the molten glass into a plate to obtain a glass ribbon, and a slow cooling step of slowly cooling the glass ribbon to room temperature. Alternatively, the molten glass may be formed into a block shape, slowly cooled, and then cut and polished to become a glass substrate.

[0068] The melting process involves preparing the raw materials to achieve the target glass composition, continuously feeding the raw materials into a melting furnace, and heating them to a temperature of preferably 1450°C to 1750°C to obtain molten glass. In this embodiment, the alkali-free glass has a low resistance value in the temperature range where the glass raw materials melt, for example, around 1500°C. Therefore, it is preferable to use an electric melting furnace and melt the glass by electric heating. However, electric heating and heating with a burner may be used in combination.

[0069] In addition to oxides, halides such as carbonates, nitrates, hydroxides, and chlorides can also be used as raw materials. If there are processes in the dissolution or clarification process in which molten glass comes into contact with platinum, minute platinum particles may dissolve into the molten glass and become foreign matter in the resulting glass plate. However, using nitrate raw materials is effective in preventing the formation of platinum foreign matter.

[0070] The clarification process involves removing bubbles from the molten glass obtained in the melting process. The clarification process may be carried out by degassing under reduced pressure, or by raising the temperature above the melting temperature of the raw materials. A clarifying agent may also be used.

[0071] In the molding process, the molten glass from which bubbles have been removed in the clarification process is formed, for example, into a plate to obtain a glass ribbon. The molding process can utilize known methods for forming glass into a plate, such as the float method, where molten glass is poured onto a molten metal such as tin to form a plate and obtain a glass ribbon; the overflow down-draw method (fusion method), where molten glass is poured downwards from a trough-shaped member; or the slit down-draw method, where molten glass is poured down through a slit. Among these, the float method and the fusion method are preferred from the viewpoint of no polishing or light polishing.

[0072] The annealing process involves cooling the glass ribbon obtained in the molding process to room temperature under controlled cooling conditions. The annealing process involves cooling the glass ribbon to form a glass ribbon, and then further annealing it to room temperature under predetermined conditions. After cutting the annealed glass ribbon, a glass substrate is obtained.

[0073] The alkali-free glass according to this embodiment is suitable for glass substrates, surface acoustic wave (SAW) devices, radar components such as radar transceivers, antenna components such as liquid crystal antennas and panel antennas, window glass, vehicle window glass, touch panel cover glass, electronic components, etc., due to the characteristics described above. Suitable examples of the glass substrate include semiconductor package substrates, interposers, and optical element substrates for semiconductor devices used in communication equipment such as mobile phones, smartphones, personal digital assistants, and Wi-Fi devices. As semiconductor package substrates, glass substrates used as core materials for electronic circuit boards are more preferred.

[0074] <Glass Substrate> The glass substrate according to this embodiment has a pair of opposing main surfaces and end surfaces. The glass constituting this glass substrate is the glass described in <Alkali-Free Glass> above, and is the same as in the preferred embodiment.

[0075] The arithmetic mean roughness Ra of at least one main surface of the glass substrate according to this embodiment is not particularly limited, but is, for example, 1.5 nm or less. This can be said to be a value unique to glass compared to substrates containing glass cloth and resin.

[0076] The value of the arithmetic mean roughness Ra on the main surface of the glass substrate according to this embodiment is not particularly limited, but as mentioned above, if it is 1.5 nm or less, it is difficult to achieve high adhesion when wiring metal electrodes due to its smoothness.

[0077] In this embodiment, it is preferable that metal electrodes are wired on the surface of the glass substrate, and more preferably that the metal electrodes are wired via an adhesion layer, as described above, from the viewpoint of achieving high adhesion. Therefore, it is preferable that an adhesion layer is formed on the surface of the glass substrate in this embodiment.

[0078] The adhesion layer is not particularly limited as long as it can achieve high adhesion between the metal electrode and the glass substrate, but metal oxides are preferred, for example, ZnO and SnO ２ At least one of the following is often used: ZnO and SnO ２ In all cases, the ionic radii are close to those of the metals constituting the specific metal oxides contained in the alkali-free glass according to this embodiment, thus enabling more favorable adhesion.

[0079] In this embodiment, the glass substrate preferably has through holes in the thickness direction to accommodate the wiring of through electrodes, and it is preferable that the surface of the glass substrate, including the side walls of the through holes, is covered with an adhesion layer. When through electrodes are wired, a conductor is secured between one main surface side of the glass substrate and the opposite main surface side. By covering the surface of the glass substrate, including the side walls of the through holes, with an adhesion layer, the through electrodes can be wired with high adhesion.

[0080] The adhesion layer only needs to be formed on the surface of the glass substrate in the area where the electrodes are wired. For example, the adhesion layer may cover only the surface of the side wall of the through hole and the through-hole electrodes may be wired, or the adhesion layer may cover not only the surface of the side wall of the through hole but also the surfaces of the main surfaces of the glass substrate near the through hole that are connected to it, and electrodes may be wired not only to the through-hole electrodes but also to the surfaces of the main surfaces of the glass substrate near the through hole.

[0081] The thickness of the adhesion layer is not particularly limited, but may be, for example, 1 nm to 20 nm. Here, from the viewpoint of adhesion between the electrode and the glass, the thickness of the adhesion layer is preferably 1 nm or more, more preferably 1.5 nm or more, even more preferably 2 nm or more, even more preferably 2.5 nm or more, especially preferably 3 nm or more, and particularly preferably 3.5 nm or more. Also, from the viewpoint of surface roughness between the electrode and the glass, the thickness of the adhesion layer is preferably 20 nm or less, more preferably 18 nm or less, even more preferably 16 nm or less, even more preferably 15 nm or less, especially preferably 14 nm or less, and particularly preferably 12 nm or less.

[0082] The method for coating the surface of a glass substrate with an adhesion layer is not particularly limited, but if the adhesion layer is a layer of metal oxide, it can be coated by, for example, dip coating, spin coating, spray coating, curtain coating, rolling, printing, screen printing, inkjet printing, brush coating, etc. These methods may be combined and performed multiple times, or one method may be performed multiple times. When the above coating is performed multiple times, it is preferable to remove the solvent before applying the next coating to at least partially dry the coated material. Heating may be used for drying.

[0083] It is preferable to clean the glass substrate before coating it with the adhesion layer. Alternatively, the adhesion of the adhesion layer may be improved by pre-heating after coating with the metal oxide adhesion layer. The conditions for the heat treatment are not particularly limited, but for example, pre-heating at 350 to 1200°C for 1 to 180 minutes may be performed.

[0084] The heat treatment temperature may be, for example, 350°C or higher, 400°C or higher, 450°C or higher, 1200°C or lower, 1000°C or lower, 800°C or lower, or 600°C or lower. Alternatively, calcination may be performed with a temperature gradient. The heat treatment time may be, for example, 1 minute or more, 10 minutes or more, 30 minutes or more, 180 minutes or less, 120 minutes or less, or 90 minutes or less.

[0085] The shape of the through-hole is not particularly limited as long as the two main surfaces of the glass substrate can conduct electricity through the through-electrode. For example, it may be a through-hole formed perpendicular to the main surface from one main surface to the opposite main surface, or it may be a through-hole tapered from one main surface of the glass substrate toward the other main surface. By tapering the shape so that the diameter of the through-hole decreases from each of the two main surfaces of the glass substrate toward the center of the glass substrate, it may also be a through-hole with a constriction in the central part of the glass substrate.

[0086] The dimensions of the through-hole are not particularly limited, but the diameter of the through-hole may be, for example, 20 to 300 μm. Here, the diameter may be, for example, 20 μm or more, 50 μm or more, 75 μm or more, or 100 μm or more. Also, the diameter may be, for example, 300 μm or less, 250 μm or less, 200 μm or less, or 150 μm or less. Here, if the cross-sectional shape of the through-hole is not circular, the diameter refers to the length of the longest diameter. Also, if the diameter is not constant, the diameter refers to the diameter of the opening on the main surface, but if the through-hole is tapered, it refers to the diameter of the opening on the main surface on the side with the larger diameter.

[0087] The number of through-holes in the glass substrate according to this embodiment is not particularly limited, but for example, the distance between adjacent through-holes can be about 200 to 1000 μm. Here, from the viewpoint of suitably preventing the electrodes from becoming clogged and causing dielectric breakdown, the above distance may be 200 μm or more, 300 μm or more, 350 μm or more, or 400 μm or more. Also, from the viewpoint of forming fine wiring, the above distance may be 1000 μm or less, 900 μm or less, 800 μm or less, or 700 μm or less. Here, the above distance refers to the distance between the centers of the through-holes.

[0088] The size and thickness of the glass substrate according to this embodiment are not particularly limited, but for example, sizes that were difficult to adopt from the viewpoint of rigidity in glass cloth and composite substrates of resin and glass cloth can be adopted with the glass substrate according to this embodiment. For example, when the glass substrate according to this embodiment is made larger, the size of at least one side may be 300 to 4000 mm. Here, the size of at least one side may be 300 mm or more, 500 mm or more, or 1000 mm or more. Furthermore, the upper limit of the above size is not particularly limited, but for example, it may be 4000 mm or less. In addition, the shape of the glass substrate is often rectangular, but it is not limited to this.

[0089] The thickness of the glass substrate according to this embodiment may be, for example, 0.01 to 2 mm. Here, from the viewpoint of thinning and miniaturizing the device, improving production efficiency, and improving ultraviolet transmittance so that ultraviolet curing materials can be used in the device manufacturing process, the above thickness is preferably 2 mm or less, preferably 1.5 mm or less, preferably 1.3 mm or less, preferably 1.1 mm or less, and preferably 1.0 mm or less. Furthermore, it is preferably 0.7 mm or less, more preferably 0.6 μm or less, even more preferably 0.5 mm or less, even more preferably 0.4 mm or less, especially preferably 0.3 mm or less, very preferably 0.2 mm or less, and particularly preferably 0.1 mm or less. Also, there is no particular lower limit, but it may be, for example, 0.01 mm or more.

[0090] Through-holes can be formed using conventionally known methods. For example, a laser can be used to alter the material at the location where the through-hole is to be formed, and then the material can be immersed in a concentrated alkaline solution or a chemical solution such as hydrofluoric acid. This process dissolves the altered material, forming the through-hole.

[0091] The glass substrate according to this embodiment is preferably used in high-frequency devices, and more preferably in core materials for electronic circuit boards.

[0092] <Core material for electronic circuit board> The core material for an electronic circuit board according to this embodiment includes glass, a metal oxide adhesion layer, and electrodes. Here, the glass can be the same as the alkali-free glass described above, and the preferred embodiment is the same. The glass also has through holes in the thickness direction of the core material. The surface of the glass including the through holes is covered with an adhesion layer, and through electrodes are wired to the through holes via the adhesion layer.

[0093] In other words, the glass described in the above-mentioned "Glass Substrate" can be used as the glass having through holes covered with an adhesion layer in the core material for electronic circuit boards according to this embodiment, and the preferred embodiment is the same. For example, the metal oxides constituting the adhesion layer are ZnO and SnO ２ At least one of these is preferred. Furthermore, the through-hole may be tapered.

[0094] <Electrodes> The through-electrodes in this embodiment are not particularly limited as long as they adhere well to the glass via the adhesion layer. Examples include copper electrodes, copper alloy electrodes, zinc electrodes, zinc alloy electrodes, platinum electrodes, platinum alloy electrodes, etc. Among these, copper electrodes and zinc electrodes are preferred from the viewpoint of electrical resistance, and copper electrodes are more preferred.

[0095] The method of wiring the electrodes is not particularly limited, and conventionally known methods can be used. Examples of methods for wiring metal electrodes include wet chemical plating. Examples of wet chemical plating methods include electroplating, dipping plating, and electroless plating.

[0096] In the case of wiring copper electrodes, for example, a seed layer may be formed by electroless plating, and then the copper electrodes may be formed by electrolytic plating.

[0097] Specific methods for electroless copper plating to form a seed layer include, for example, contacting glass coated with an adhesion layer with an aqueous solution containing a catalyst metal, and then contacting it with an electroless copper plating aqueous solution containing a copper ion source and a reducing agent.

[0098] Examples of catalysts in aqueous solutions containing the above-mentioned catalyst metals include Pt, Pd, Au, Ag, Cu, Rh, Os, and Ir. Alkaline solutions are preferred as aqueous solutions, such as sodium hydroxide solution and potassium hydroxide solution. A preferred combination of these is, for example, a sodium hydroxide solution containing a Pd catalyst.

[0099] Examples of reducing agents for electroless copper plating aqueous solutions include formaldehyde, hypophosphate, glyoxylic acid, dimethylaminoborane, and sodium borohydride. Examples of copper ion sources include copper sulfate, copper phosphate, and copper nitrate.

[0100] In addition to the above, the electroless copper plating aqueous solution may contain pH adjusters, complexing agents, accelerators, stabilizers, and other additives as needed.

[0101] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Examples 1 to 14 are examples, and Example 15 is a comparative example.

[0102] Examples 1 to 15: Glass raw materials were weighed and mixed to obtain 400 g of glass having the composition shown in Table 1 (expressed in mol% based on oxide). The mixed glass raw materials were placed in a platinum crucible and placed in an electric furnace, where they were heated at a temperature of 1500 to 1700°C for about 3 hours to melt, degass and homogenize to obtain molten glass. A portion of the obtained molten glass was poured into a metal mold, held at a temperature of about 600 to 800°C for 1 hour, and then cooled to room temperature at a rate of 1°C / min to form a glass plate (main surface area: 10,000 mm²). ２ A thickness of 10 mm was obtained.

[0103] The glass plate obtained above was coated with an adhesion layer and a copper plating film that could serve as a copper electrode was formed on it using the following procedure. The glass plate was washed by immersing it in sulfuric acid and then in an aqueous sodium hydroxide solution. After that, the glass plate was immersed in a solution of zinc acetate dihydrate dissolved in ethanol (0.25 M), pulled out at a speed of 0.5 cm / s, and then pre-annealed at a temperature of 150°C for 10 minutes. After repeating these steps three times, the glass plate surface was coated with an adhesion layer by annealing at 560°C for 1 hour. Next, a seed layer was formed on the glass plate coated with the adhesion layer by electroless copper plating. In electroless plating, the glass plate is immersed in a plating solution, and copper, which is a metal, is deposited on the surface of the glass plate by the reduction of complexed metal ions. The plating solution contains a metal source, a complexing agent, and a reducing agent, with copper sulfate used as the metal source. Rochelle salt (potassium sodium tartrate) was used as the complexing agent. Formaldehyde was used as the reducing agent. The glass plate on which the seed layer had been formed as described above was immersed in the plating solution as the cathode electrode, and a voltage was applied between the cathode electrode and the anode electrode to deposit copper on the surface of the glass plate, resulting in a glass plate coated with an adhesion layer and a copper plating film that could serve as a copper electrode. The plating solution used was an aqueous solution containing copper sulfate and sulfuric acid. Oxygen-free copper was used as the anode electrode. The current density was 1.5 ASD (A / dm²). ２ The procedure was carried out under the following conditions.

[0104] 《Evaluation》 〈Adhesion: Peel Strength〉 The peel strength of the above glass plate was measured using a precision universal testing machine, Autograph (Shimadzu Corporation, AGX-V). The tensile speed was 50 mm / min, the peel angle was 90°, and the test stroke was 30 mm. The test was conducted under conditions of 25°C and 40% humidity. The results are shown in Table 1. If the peel strength was 5 N / cm or more, it was marked as "◎" indicating very good adhesion to the metal electrode; if it was 3 N / cm or more and less than 5 N / cm, it was marked as "○" indicating good adhesion; if it was 1 N / cm or more and less than 3 N / cm, it was marked as "△" indicating it was usable and acceptable; and if it was less than 1 N / cm, it was marked as poor adhesion and "×".

[0105] <Electrical properties: relative permittivity Dk, dielectric loss tangent Df> Before forming the adhesion layer and copper plating film, a glass plate was processed to 35 mm × 35 mm × 0.5 mm, and the relative permittivity Dk and dielectric loss tangent Df were measured using a network analyzer by the slip-post dielectric resonance method (SPDR method) according to the method specified in JIS R 1641:2007. The measurement frequency was set to 10 GHz, which is the resonant frequency of the air in the cavity resonator. The results are shown in Table 1.

[0106] <Transparency> Both main surfaces of the obtained glass plates were mirror-polished, and the haze value at a thickness of 1 mm was measured using a haze meter (manufacturer: Suga Test Instruments Co., Ltd., model: HZ-V3 Hazemeter). Glass with a haze value of 10% or less was marked as having high transparency ("○"), and glass with a haze value exceeding 10% was marked as having low transparency ("×"). The results are shown in Table 1, but the glass in Example 14 showed clouding due to phase separation or crystallization.

[0107]

[0108] From the above results, it was found that the alkali-free glass according to this embodiment has a relative permittivity of 6 or less and a dielectric loss tangent of less than 0.006, possessing the electrical properties required for a glass core while also exhibiting sufficient peel strength, thus demonstrating high adhesion to the metal electrode. Furthermore, from the results of Examples 1 to 13, it was found that by adjusting the specific metal oxide to an appropriate range, good transparency can also be achieved in addition to the above. On the other hand, from the results of Example 15, it was found that without containing the specific metal oxide, the peel strength was insufficient, making it an unsuitable material for glass core applications.

[0109] <Performability of Hole Processing> Hole processing was performed on the glass plate obtained in Example 1. Hole processing was carried out by altering the glass plate by irradiating it with a laser with a wavelength of 532 nm, and then immersing it in a 3 M sodium hydroxide aqueous solution. As a result, through holes with a diameter of 100 μm and a distance of 500 μm between adjacent through holes were formed. Furthermore, by controlling the hole diameter by adjusting the laser irradiation time and the hole spacing by adjusting the laser irradiation position, it was also possible to form through holes with a diameter of 50 μm and a distance of 250 μm between adjacent through holes. From the above results, it was confirmed that the glass substrate made of alkali-free glass according to this embodiment also has excellent perforation properties.

[0110] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2025-044726 filed on 19 March 2025, the contents of which are incorporated herein by reference.

Claims

1. The content ratio in terms of mole percentage based on oxides is SiO ２ 45 to 70%, Al ２ O ３ 4 to 15%, B ２ O ３ 15 to 30%, MgO 0.1 to 10%, CaO 0.1 to 10%, SrO 0.1 to 10%, BaO 0.3 to 10%, and the total of specific metal oxides satisfies 0.2 to 35%, wherein the specific metal oxides are ZnO, SnO ２ , Sc ２ O ３ , TiO ２ , Ga ２ O ３ , ZrO ２ , Nb ２ O ５ , In ２ O ３ , HfO ２ , Ta ２ O ５ , WO ３ , Yb ２ O ３ , and Lu ２ O ３ , which is at least one selected from the group consisting of, the ratio of the content ratio represented by [Al ２ O ３ / [B ２ O ３ is more than 0.27, an alkali-free glass.

2. The alkali-free glass according to claim 1, wherein the content ratio in molar percentage based on oxides further satisfies the requirement of 0.2 to 12% of the total of specific metal oxides.

3. The alkali-free glass according to claim 1, wherein the haze value when the plate thickness is 1 mm is 10% or less.

4. The alkali-free glass according to claim 1, wherein the dielectric loss tangent at 10 GHz is 0.006 or less.

5. The alkali-free glass according to claim 1, wherein the relative permittivity at 10 GHz is 6 or less.

6. A glass substrate having a pair of opposing main surfaces and end surfaces, wherein the glass constituting the glass substrate is alkali-free glass as described in any one of claims 1 to 5.

7. The glass substrate according to claim 6, wherein the glass substrate has through holes in the thickness direction, and the surface of the glass substrate, including the side walls of the through holes, is covered with an adhesive layer of metal oxide.

8. The metal oxides constituting the adhesion layer are ZnO and SnO ２ The glass substrate according to claim 7, which is at least one of the two.

9. The glass substrate according to claim 7, wherein the through hole is tapered from one main surface of the glass substrate toward the other main surface.

10. The glass substrate according to claim 6, wherein the arithmetic mean roughness Ra of at least one of the pair of main surfaces is 1.5 nm or less.

11. The glass substrate according to claim 6, used as a core material for an electronic circuit board.

12. A core material for an electronic circuit board comprising glass, an adhesion layer of a metal oxide, and electrodes, wherein the glass is alkali-free glass according to any one of claims 1 to 5, the glass has through holes in the thickness direction of the core material, the surface of the glass including the through holes is covered with the adhesion layer, and through electrodes are wired to the through holes via the adhesion layer.

13. The metal oxides constituting the adhesion layer are ZnO and SnO ２ The core material for an electronic circuit board according to claim 12, which is at least one of the above.

14. The core material for an electronic circuit board according to claim 12, wherein the through hole is tapered.

15. The core material for an electronic circuit board according to claim 12, wherein the through electrode is a copper electrode.

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