Piezoelectric Vibrator Coating Structure for Frequency Stability
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Solution Overview
Problem
Existing piezoelectric vibrators experience frequency fluctuations due to chromium diffusion during manufacturing, leading to instability, as chromium exposed from the monomolecular film becomes oxidized or hydroxylated.
Innovation Solution
A piezoelectric vibrator design incorporating a piezoelectric vibration element with a pair of electrodes, a holder, a resin layer covering at least one electrode, and a water-repellent layer with lower moisture permeability than the resin layer, along with a manufacturing method involving annealing to disperse the conductive holding member and bonding a cover member to form these layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a monomolecular film is formed on the excitation electrode to suppress frequency fluctuations, then frequency stability is improved, but chromium diffusion and oxidation occur during manufacturing causing frequency instability
Solution Approach 1:
The protective film is divided into two distinct layers: a monomolecular film layer that provides the primary frequency stabilization function, and a water-repellent layer that prevents chromium oxidation. This segmentation allows each layer to perform its specific function independently, resolving the contradiction between frequency stability and compositional stability.
Solution Approach 2:
The water-repellent layer acts as an intermediary protective barrier between the chromium-containing electrode and the external environment. It mediates the protection by preventing moisture and oxygen from reaching the chromium, thus preventing oxidation while allowing the monomolecular film to maintain frequency stability.
2Reliability
If chromium is used as a base film for gold deposition, then electrode adhesion and conductivity are improved, but chromium diffuses and oxidizes during manufacturing
Solution Approach 1:
The water-repellent layer serves as an intermediary protective barrier that shields the chromium base film from oxidation while allowing the chromium to maintain its adhesion and conductivity functions in the electrode structure.
Solution Approach 2:
The water-repellent layer creates a chemically inert environment around the chromium by preventing contact with moisture and oxygen, effectively isolating the chromium from harmful oxidative reactions during manufacturing and operation.
3Reliability
If silicone-based adhesive is used for mounting, then electrical connection is achieved, but siloxane component evaporation and deposition occur
Solution Approach 1:
The harmful siloxane component is extracted and isolated into a separate water-repellent layer, away from the excitation electrode. This allows the silicone-based adhesive to provide electrical connection while its evaporated components are prevented from depositing on the electrode surface.
Solution Approach 2:
The water-repellent layer acts as an intermediary barrier that prevents siloxane vapor from the adhesive from reaching and depositing on the excitation electrode, while still allowing the adhesive to fulfill its electrical connection function.
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 provides improved frequency stability by inhibiting chromium oxidation and moisture penetration, thereby stabilizing the frequency of the piezoelectric vibrator.
Implementation Method 1
a water-repellent layer, which has a lower moisture permeability than the resin layer, between the electrode and the resin layer
Implementation Method 2
annealing the pair of electrodes so as to cause part of the electrically conductive holding member to disperse and deposit on surfaces of the pair of electrodes
Implementation Method 3
annealing the pair of electrodes so as to cause part of the electrically conductive holding member to disperse and deposit on surfaces of the pair of electrodes
Implementation Method 4
a piezoelectric vibration element, which includes a mechanical vibration part that converts electrical vibrations into mechanical vibrations using the piezoelectric effect
Data Source
AI summary
A piezoelectric vibrator having a piezoelectric vibration element that includes a piezoelectric piece and a pair of electrodes that face each other with the piezoelectric piece interposed therebetween; a holder that accommodates the piezoelectric vibration element; a resin layer covering at least one electrode of the pair of electrodes; and a water-repellent layer, which has a lower moisture permeability than the resin layer, between the electrode and the resin layer.