Piezoelectric Resonator Layout for Stable Frequency and Impact Resistance
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Solution Overview
Problem
In MEMS vibrators, variations in resonant frequency due to manufacturing variations and electric charges on insulator layers can occur, leading to instability and potential damage from collisions, which existing technologies have not adequately addressed.
Innovation Solution
A resonator design featuring vibration arms with a protective film and a conductive film, where via electrodes electrically connect the conductive film to the electrodes, positioning the via electrodes closer to the region with the protective film than the open end, to suppress the influence of electric charges and enhance structural strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a mass portion including an insulator layer and conductive layer is formed on the vibration arm to adjust resonant frequency, then resonant frequency adjustment is achieved, but electric charges are generated in the insulator layer causing frequency variation
Solution Approach 1:
The patent extracts the harmful insulator layer from the mass portion configuration. Instead of using a multi-layer mass portion with insulator and conductor, the invention uses only a conductive layer for frequency adjustment, eliminating the source of charge accumulation while maintaining the frequency tuning function
Solution Approach 2:
The patent introduces a charge discharge electrode as an intermediary component. This electrode provides a dedicated path for discharged charges to escape from the vibration arm, preventing charge accumulation that would otherwise cause frequency drift while allowing the mass portion to maintain its frequency adjustment function
2Ease of operation
If the distal end of the vibration arm is extended to increase movable range, then vibration amplitude is improved, but the distal end becomes vulnerable to collision damage
Solution Approach 1:
The patent applies beforehand cushioning by forming a protective film on the surface of the vibration arm, particularly at the distal end. This protective layer is prepared in advance to absorb or distribute collision impacts, preventing direct damage to the underlying structural materials while maintaining the extended geometry needed for vibration amplitude
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 design effectively stabilizes the resonant frequency by preventing charge-induced frequency variations and reduces the risk of damage from collisions by distributing impact away from vulnerable areas.
Implementation Method 1
a piezoelectric film provided between the upper electrode and the lower electrode, having a main surface facing the upper electrode, and causing bending vibration of the vibration arm when a voltage is applied between the upper electrode and the lower electrode
Implementation Method 2
a via electrode is formed in the protective film to electrically connect the conductive film to any one of the upper electrode and the lower electrode
Data Source
AI summary
A resonator includes a vibration portion with a vibration arm extending from a base and having an open end that performs bending vibration. The vibration portion includes upper and lower electrodes with a piezoelectric film disposed therebetween that causes bending vibration of the vibration arm when a voltage is applied between the upper and lower electrodes. A protective film faces the piezoelectric film with the upper electrode interposed therebetween and a conductive film faces the piezoelectric film with the protective film interposed therebetween. Moreover, the conductive film is exposed in a region at the open end and a via electrode is formed in the protective film to electrically connect the conductive film to one of the upper and lower electrodes. The via electrode is positioned closer to a first region than the open end in the second region of the vibration arm in a plan view of the piezoelectric film.