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 for a high-frequency device, the glass comprising, 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 4 O 3 ;
2.5 to 11% of MgO; and
3 to 13% of CaO, and
having a total content of alkali metal oxides in the range of 0.001-5%,
wherein 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 , having a content of Fe, in terms of Fe 2 O 3 , of 0.012% or less in terms of mole percent on the basis of oxides.
3. The glass substrate according to claim 1 , having a total content of Al 2 O 3 and B 2 O 3 in the range of 24-38% in terms of mole percent on the basis of oxides.
4. The glass substrate according to claim 1 , wherein the total content of alkali metal oxides is in the range of 0.001-0.1%.
5. The glass substrate according to claim 1 , having a molar ratio represented by Al 2 O 3 /(Al 2 O 3 +B 2 O 3 ) in the range of 0-0.45, in terms of mole percent on the basis of oxides.
6. The glass substrate according to claim 1 , wherein the alkali metal oxides has a molar ratio represented by Na 2 O/(Na 2 O+K 2 O) in the range of 0.01-0.99.
7. The glass substrate according to claim 1 , which is amorphous.
8. The glass substrate according to claim 1 , having a β-OH value in the range of 0.05-0.6 mm −1 .
9. The glass substrate according to claim 1 , having a relative permittivity at 35 GHz of 10 or less.
10. The glass substrate according to claim 1 , having an average thermal expansion coefficient over the range of from 50° C. to 350° C. in the range of 3-15 ppm/° C.
11. The glass substrate according to claim 1 , having a Young's modulus of 40 GPa or higher.
12. The glass substrate according to claim 1 , having a porosity of 0.1% or less.
13. The glass substrate according to claim 1 , having a transmittance at 350-nm wavelength of 50% or higher.
14. The glass substrate according to claim 1 , having a thickness in the range of 0.05-1 mm and a substrate area in the range of 225-10,000 cm 2 .
15. A circuit board for a high-frequency device in which high-frequency signals having a frequency of 10 GHz or more is processed, the circuit board comprising:
the glass substrate according to claim 1 ; and
a wiring layer formed on the main surface of the glass substrate,
wherein the circuit board has a transmission loss at 35 GHz of 1 dB/cm or less.