Resonator Element Break-Off Geometry for Stable Frequency Control
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Solution Overview
Problem
Existing methods for manufacturing piezoelectric resonator elements, such as those described in JP-A-2007-142995, suffer from etching anisotropy in quartz crystal wafers leading to uneven crack formation during breaking off, resulting in unpredictable stress concentration and shape variation.
Innovation Solution
A method involving dry etching is used to form a resonator element assembly with a narrow portion in the holding portion, where the width is minimal near the resonator element, and the angle between the side surface and flat surface of the holding portion is controlled within 85° to 95°, concentrating stress at the narrowest point for controlled breaking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wet etching is used to form the holding portion, then the etching process is simple, but the etching anisotropy of quartz crystal causes unpredictable crack formation and stress concentration during breaking off
Solution Approach 1:
The patent changes the etching method from wet etching to dry etching, which fundamentally alters the etching parameters and mechanism. Dry etching provides isotropic etching characteristics that eliminate the directional dependence and crack formation issues associated with wet etching anisotropy, while maintaining manufacturing simplicity
Solution Approach 2:
The patent introduces an asymmetric narrow portion in the holding portion design, where the width varies along the length. This asymmetric geometry creates a predetermined stress concentration point that controls where cracking occurs during breaking off, ensuring consistent separation at the intended location rather than unpredictable crack formation
2Device complexity
If the holding portion width is uniform, then the structure is simple, but stress is not controlled during breaking off leading to shape variation
Solution Approach 1:
The patent applies local quality by creating a narrow portion with reduced width at a specific location within the holding portion. This localized geometric modification concentrates stress at the narrow portion during breaking off, providing controlled and predictable separation while maintaining the overall simplicity of the holding portion structure
3Manufacturing precision
If crack formation is unpredictable, then breaking off location varies, but this leads to shape variation of the support portion and unstable resonation characteristics
Solution Approach 1:
The patent performs preliminary action by designing the holding portion with a predetermined narrow portion before the breaking off process. This pre-designed geometric feature ensures that cracking occurs at the intended location during breaking off, eliminating unpredictable crack formation and ensuring consistent support portion shape and stable resonation characteristics
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
This approach reduces shape variation and stress concentration, ensuring stable resonation characteristics and consistent resonator element shape, minimizing frequency variation and residue after breaking off.
Implementation Method 1
The etching process is dry etching
Data Source
AI summary
A method for manufacturing a resonator element includes: a substrate preparation step of preparing a substrate; an etching step of performing an etching process on the substrate to form a resonator element, a frame portion, and a holding portion that couples the resonator element and the frame portion; and a break-off step of breaking off the resonator element from the frame portion. The holding portion includes a narrow portion in which a part of a width is narrow. The width of the narrow portion is minimum at a position closer to a resonator element side than at a center of the holding portion. In a cross-sectional view, an angle formed by a side surface of the narrow portion with respect to a flat surface of the holding portion is in a range of 85° or more and 95° or less. The etching process is dry etching.