Glass substrate for high-frequency device and circuit board for high-frequency device
A glass substrate for a high-frequency device, which contains, in terms of mole percent on the basis of oxides: 40 to 75% of SiO 2 ; 0 to 15% of Al 2 O 3 ; 13 to 23% of B 2 O 3 ; 2.5 to 11% of MgO; and 0 to 13% of CaO, and having a total content of alkali metal oxides in the range of 0.001-5%, where at least one main surface of the glass substrate has a surface roughness of 1.5 nm or less in terms of arithmetic average roughness Ra, and the glass substrate has a dielectric dissipation factor at 35 GHz of 0.007 or less.
1 . A glass substrate, comprising:
a glass composition comprising, in terms of mole percent on a basis of oxides:
40 to 75% of SiO 2 ;
0 to 10% of Al 2 O 3 ;
13 to 36% of B 2 O 3 ; and
0.1 to 6% of CaO,
wherein
a total content of Al 2 O 3 and B 2 O 3 is in a range of 13-40%,
a total content of alkaline earth metal oxides is in a range of 0.1-6%, and
a total content of alkali metal oxides is in a range of 0.001-5%,
wherein the glass composition has a molar ratio Al 2 O 3 /(Al 2 O 3 +B 2 O 3 ) in a range of 0-0.45, at least one main surface of the glass substrate has a surface roughness of 1.5 nm or less in terms of arithmetic average roughness Ra, and the glass substrate has a dielectric dissipation factor at 35 GHz of 0.007 or less.
2 . The glass substrate according to claim 1 , wherein the glass composition comprises 13-30% of B 2 O 3 in terms of mole percent on the basis of oxides.
3 . The glass substrate according to claim 1 , wherein a content of Fe, in terms of Fe 2 O 3 , is 0.012% or less in terms of mole percent on the basis of oxides.
4 . The glass substrate according to claim 1 , wherein the alkali metal oxides has a molar ratio Na 2 O/(Na 2 O+K 2 O) in a range of 0.01-0.99.
5 . The glass substrate according to claim 1 , wherein the glass substrate has a β-OH value in a range of 0.05-0.6 mm −1 .
6 . The glass substrate according to claim 1 , wherein the glass substrate has a relative permittivity at 35 GHz of 10 or less.
7 . The glass substrate according to claim 1 , wherein the glass substrate has an average thermal expansion coefficient over the range of from 50° C. to 350° C. in a range of 3-15 ppm/° C.
8 . The glass substrate according to claim 1 , wherein the glass substrate has a Young's modulus of 40 GPa or higher.
9 . The glass substrate according to claim 1 , wherein the glass substrate has a porosity of 0.1% or less.
10 . The glass substrate according to claim 1 , wherein the glass substrate has a transmittance at 350-nm wavelength of 50% or higher.
11 . The glass substrate according to claim 1 , wherein the glass substrate has a thickness in a range of 0.05-1 mm and a substrate area in a range of 225-10,000 cm 2 .