AT-Cut Quartz Vibrating Piece Electrode Layout for Low Impedance
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Solution Overview
Problem
Existing quartz crystal devices fail to meet the request for high-frequency quartz crystal devices with a thin film that is capable of achieving low crystal impedance, particularly in high-frequency applications exceeding 100 MHz.
Innovation Solution
The quartz crystal device incorporates a package with a specific electrode design, including a rectangular AT-cut quartz-crystal vibrating piece and a securing member, where the extraction electrode width to the short-side direction ratio is between 15% and 50%, optimizing the electrode configuration to reduce crystal impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the electrode film thickness is thinned to reduce device size in high-frequency crystal units, then the device size is reduced, but the crystal impedance increases and cannot meet the low crystal impedance requirement
Solution Approach 1:
The patent applies local quality by making the extraction electrode width variable rather than uniform. The extraction electrode has a wider section near the pad electrode and a narrower section toward the excitation electrode, optimizing the local electrical characteristics at different positions to achieve low crystal impedance while maintaining thin film thickness
Solution Approach 2:
The patent changes the geometric parameter of the extraction electrode, specifically setting its width to 15% or more and less than 50% of the dimension in the short-side direction of the quartz-crystal vibrating piece. This parameter optimization balances the electrical performance (low crystal impedance) with the mechanical constraint (thin film thickness)
2Loss of energy
If the extraction electrode width is increased to reduce wiring resistance, then the wiring resistance decreases, but the device area increases
Solution Approach 1:
The extraction electrode is designed with non-uniform width, being wider where it connects to the pad electrode (where current density is highest) and tapering toward the excitation electrode. This local quality variation reduces wiring resistance at critical interfaces without proportionally increasing the overall device area
Solution Approach 2:
By optimizing the extraction electrode width within the specific range of 15% to 50% of the short-side dimension, the patent achieves a balance between minimizing wiring resistance and controlling device footprint, avoiding both excessive width that would increase area and insufficient width that would increase resistance
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 optimized electrode design achieves low crystal impedance and stable wiring resistance, facilitating efficient energy confinement and vibration in high-frequency quartz crystal devices.
Implementation Method 1
an AT-cut quartz-crystal vibrating piece... The excitation electrodes, the pad electrodes, and the extraction electrodes are formed on front and back surfaces
Data Source
AI summary
A quartz crystal device includes a package, an AT-cut quartz-crystal vibrating piece, and a securing member. The package includes a bottom plate in a rectangular shape in plan view, a dike provided along an edge of the bottom plate, and an adhesion pad provided on one end side in a long-side direction in an inner region surrounded by the dike. The quartz-crystal vibrating piece includes an excitation electrode, a pad electrode positioned on one end side in a long-side direction thereof, and an extraction electrode connecting the excitation electrode to the pad electrode. The securing member secures the quartz-crystal vibrating piece to the adhesion pad at a position where the pad electrode is opposed to the adhesion pad. A ratio of a width of the extraction electrode to a dimension in a short-side direction of the quartz-crystal vibrating piece is 15% or more and less than 50%.