Quartz Vibrator Through-Hole Insulation With Low Parasitic Capacitance
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Solution Overview
Problem
In vibrator devices, it is challenging to form a thicker SiO2 film on the inner surface of through holes without increasing parasitic capacitance, which affects the performance of quartz crystal vibrators due to larger parasitic capacitance between the base substrate and electrode films.
Innovation Solution
A vibrator device design that includes a silicon substrate with through holes, where a silicon oxide layer is formed on the inner walls and resin layers are placed between the wires and the inner walls, reducing parasitic capacitance and improving bonding reliability by using metal bumps for stable coupling of the vibrator element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thicker SiO2 film is formed on the inner surface of through holes, then insulation performance is improved, but parasitic capacitance increases
Solution Approach 1:
The patent uses a composite structure consisting of a resin layer and a SiO2 film layer combined together. The resin layer provides the primary insulation function with low dielectric constant, while the SiO2 film layer provides additional insulation and planarization. This composite approach allows achieving better insulation performance without proportionally increasing parasitic capacitance, as the resin material contributes less to capacitance compared to a purely thicker SiO2 film.
Solution Approach 2:
The patent changes the dielectric parameters by introducing a resin layer with different dielectric properties than SiO2. By selecting resin materials with lower dielectric constants and optimizing the thickness distribution between the resin layer and SiO2 film, the overall insulation performance is enhanced while controlling the parasitic capacitance to acceptable levels.
2Strength
If a thicker SiO2 film is formed on the inner surface of through holes, then breakdown voltage is improved, but parasitic capacitance between base substrate and electrode film increases
Solution Approach 1:
The composite structure of resin layer and SiO2 film layer works together to provide both electrical strength and controlled capacitance. The SiO2 film, being thinner, maintains lower capacitance while the resin layer compensates for breakdown voltage requirements through its material properties and thickness, achieving a balance between these two critical parameters.
Solution Approach 2:
The patent applies different material qualities to different regions and functions: the SiO2 film provides localized high dielectric strength at the through hole inner surface where breakdown risk is highest, while the resin layer provides bulk insulation with lower capacitance contribution. This localized quality differentiation optimizes both breakdown voltage and parasitic capacitance.
3Reliability
If metal bumps are used for coupling, then bonding reliability is improved, but warpage of silicon substrate may occur
Solution Approach 1:
The patent optimizes the parameters of the resin layer including its thickness, material composition, and curing characteristics to control thermal expansion and contraction behavior. By carefully selecting resin materials with matched thermal expansion coefficients and optimizing layer thickness, the patent minimizes warpage while maintaining bonding reliability of the metal bumps.
Solution Approach 2:
The patent addresses thermal expansion mismatch between different materials (silicon substrate, metal bumps, resin layer, SiO2 film) by selecting resin materials with appropriate thermal expansion properties and optimizing the layered structure. This reduces differential thermal stress during heating and cooling processes, thereby minimizing substrate warpage while preserving bonding integrity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design reduces parasitic capacitance, enhances bonding stability, and minimizes warpage of the silicon substrate, leading to improved vibration characteristics and reliability of the vibrator element.
Implementation Method 1
The SiO2 film formed on the inner side surface of the through hole is formed by the CVD method
Implementation Method 2
a resin layer placed between the wire and an inner wall defining the through hole
Implementation Method 3
a vibrator element bonded to the first terminal
Data Source
AI summary
A vibrator device includes a silicon substrate having a through hole, a first terminal placed on a first surface of the silicon substrate, a second terminal placed on a second surface opposite to the first surface of the silicon substrate, a wire passing the through hole and electrically coupling the first terminal and the second terminal, a resin layer placed between the wire and an inner wall defining the through hole, a silicon oxide layer placed between the resin layer and the inner wall, and a vibrator element bonded to the first terminal.