Glass Substrate for High-Frequency Devices with Low Dielectric Loss
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Solution Overview
Problem
Conventional alkali-free glass substrates struggle to maintain low dielectric loss for high-frequency signals beyond 30 GHz, and quartz glass substrates have a low thermal expansion coefficient mismatch with other device components, making them unsuitable for practical electronic devices.
Innovation Solution
A glass substrate with SiO2 as the main component, containing 0.001-5% alkali metal oxides, 1-40% Al2O3 and B2O3, and 0.1-13% alkaline earth metal oxides, with a dielectric dissipation factor of 0.007 or less at 35 GHz, and a surface roughness of 1.5 nm or less, is developed to reduce dielectric and transmission losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional alkali-free glass substrates are used, then dielectric loss is reduced at frequencies up to 20 GHz, but dielectric loss increases at frequencies exceeding 30 GHz
Solution Approach 1:
The patent modifies the chemical composition parameters of the glass substrate by precisely controlling the content of alkali metal oxides (0.001-5 mol%), alkaline earth metal oxides (0.1-13 mol%), Al2O3 (1-40 mol%), and B2O3 (1-40 mol%). This parameter optimization enables the substrate to maintain low dielectric loss at frequencies exceeding 30 GHz while ensuring signal quality, resolving the frequency-dependent performance degradation of conventional alkali-free glass substrates.
2Loss of energy
If quartz glass substrates are used, then dielectric loss remains low at frequencies exceeding 30 GHz, but thermal expansion coefficient mismatch increases with other device components
Solution Approach 1:
The patent creates a composite glass material system combining SiO2 as the base with optimized additions of alkali metal oxides, alkaline earth metal oxides, Al2O3, and B2O3. This composite composition achieves a thermal expansion coefficient of 30-90Ă10^-7/â, providing compatibility with other electronic device components while maintaining low dielectric loss at high frequencies, thus resolving the adaptability issue of pure quartz glass substrates.
3Loss of energy
If glass substrate surface roughness is reduced, then conductor loss decreases, but manufacturing complexity increases
Solution Approach 1:
The patent specifies a surface roughness parameter Ra of 1.5 nm or less for the glass substrate. This precise parameter control reduces conductor loss by minimizing surface irregularities that would otherwise increase resistance. The patent balances manufacturing feasibility by setting a practical threshold that can be achieved through standard polishing processes while still delivering the performance benefits of ultra-smooth surfaces.
Data Source
AI summary
A glass substrate for a high-frequency device, which contains, in terms of mole percent on the basis of oxides: 40 to 75% of SiO2; 0 to 15% of Al2O3; 13 to 23% of B2O3; 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.