AT-Cut Crystal Geometry for Higher Piezoelectric Impedance
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Solution Overview
Problem
Existing piezoelectric devices with AT-cut crystal elements have limitations in impedance improvement due to the shape of the crystal element's distal end and variations in crystallographic axis orientations, leading to reduced performance in vibration damping and crystal impedance.
Innovation Solution
A piezoelectric device with an AT-cut crystal element having a square planar shape and specific side surfaces intersecting with the Z′-axis, secured to a container with conductive adhesive, where the dimensions and angles of the crystal element's sides are optimized to achieve improved crystal impedance by reducing unnecessary vibrations and expanding the planar area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a long-time etching process is used to create the first to third surfaces, then the crystal impedance is improved, but the planar area of the crystal element is reduced
Solution Approach 1:
The invention changes the etching parameters by limiting the etching time and controlling the etching depth to prevent excessive material removal. By adjusting the etching process parameters, the patent achieves the necessary surface geometry for vibration damping while preserving the planar area of the crystal element, thus maintaining high crystal impedance.
Solution Approach 2:
The invention applies partial etching action by only etching specific regions (creating the first to third surfaces) rather than etching the entire crystal element uniformly. This selective partial etching achieves the vibration damping effect in critical areas while leaving the planar area largely intact, resolving the contradiction between impedance improvement and area preservation.
2Adaptability or versatility
If the distal end shape varies depending on crystallographic axis orientation, then manufacturing flexibility is increased, but the crystal impedance becomes inconsistent
Solution Approach 1:
The invention applies local quality control by specifying different geometric requirements for different parts of the crystal element. The distal end is given a controlled shape with specific dimensional ratios (W1/W0 ≥ 0.91) while the side surfaces have specific angular relationships. This localized geometric control ensures consistent vibration damping characteristics regardless of the overall crystallographic orientation, maintaining impedance consistency.
Solution Approach 2:
The invention introduces asymmetry in the etching process by creating non-uniform surface geometries (first to third surfaces with specific angles) that compensate for variations in crystallographic orientation. This asymmetric surface treatment at the distal end ensures that vibration damping performance remains consistent even when the crystal element is oriented differently along the crystallographic axes.
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 design enhances crystal impedance and reduces variations in the distal end shape, resulting in improved performance by achieving better damping of unnecessary vibrations and increased crystal impedance compared to conventional designs.
Implementation Method 1
The AT-cut crystal element is connected and secured to the container with the conductive adhesive
Implementation Method 2
achieving better damping of unnecessary vibrations
Data Source
AI summary
A piezoelectric device includes a conductive adhesive, a container, and an AT-cut crystal element. The AT-cut crystal element has at least one side surface intersecting with a Z′-axis of the crystallographic axis of the crystal constituted of three surfaces. When a dimension of a straight-line portion along the Z′-axis of a second side opposed to the first side is expressed as W1 and a dimension along the Z′-axis of the AT-cut crystal element is expressed as W0, W1/W0 is 0.91 or greater, and the straight-line portion has both sides constituting corner portions in approximately right angles with sides along an X-axis of the crystal of the AT-cut crystal element. The side of the first side is at a −X-side in an X-axis of the crystallographic axis of the crystal and a side of the second side is at a +X-side in the X-axis.