Piezoelectric Resonator Electrode Composition for Ion Beam Frequency Tuning
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Solution Overview
Problem
Piezoelectric devices face issues with frequency adjustment precision, as ion beam irradiation can reduce excitation electrode dimensions unevenly, leading to unreliable frequency adjustments and potential insulation failures due to silver's oxidation and thermal instability, especially in miniaturized components.
Innovation Solution
A ternary alloy with silver as the major component, palladium as the first additive for enhanced oxidation resistance, and copper as the second additive to form a solid solution, is used for excitation electrodes. This alloy is rich in palladium at the outer peripheries to prevent sputtering and thermal aggregation, ensuring stable dimensions and resistance to oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ion beam irradiation is used for fine frequency adjustment, then the frequency can be increased to the target frequency, but the external dimension of excitation electrodes decreases due to greater mass removal at outer periphery
Solution Approach 1:
The patent applies local quality by creating a non-uniform composition distribution within the excitation electrode material. The outer peripheral region contains a higher proportion of corrosion-resistant material compared to the central region, allowing differential protection during ion beam irradiation. This compositional gradient ensures that the outer periphery, which experiences greater sputtering, has enhanced resistance to material removal, thereby maintaining electrode dimension precision while enabling frequency adjustment.
Solution Approach 2:
The patent uses composite materials by combining multiple materials with different properties in a single excitation electrode structure. The electrode consists of a core material for electrical conductivity and a peripheral material with higher corrosion and sputtering resistance. This composite structure allows the electrode to simultaneously achieve frequency tuning capability through ion beam irradiation while protecting the outer dimensions from excessive erosion.
2Ease of manufacture
If pure silver is used for excitation electrodes, then the cost is reduced compared to gold, but the weatherability and chemical resistance are insufficient due to oxidation
Solution Approach 1:
The patent employs composite materials by forming a layered or mixed-structure excitation electrode where pure silver or low-cost alloy forms the core for electrical conductivity, while a corrosion-resistant material layer is positioned at the outer peripheral region. This composite structure maintains cost-effectiveness through the use of cheaper materials in the bulk while providing superior weatherability and chemical resistance at the exposed surfaces where oxidation would occur.
Solution Approach 2:
The patent applies local quality by concentrating the corrosion-resistant material specifically at the outer peripheral regions of the excitation electrode where exposure to oxidizing environments occurs. The central region can remain as pure silver or cost-effective alloy to maintain electrical performance, while the peripheral zone provides protective functionality against oxidation and chemical degradation.
3Stability of the object's composition
If high temperature thermal treatment is applied, then thermal stress and strain are reduced, but silver particles coagulate causing delamination or disconnection of electrodes
Solution Approach 1:
The patent applies local quality by positioning corrosion-resistant material specifically at the outer peripheral regions of the excitation electrode where silver particles are most prone to coagulation and migration during thermal treatment. This localized reinforcement prevents delamination and disconnection at the vulnerable edge regions while allowing the central region to undergo thermal stress relief, achieving a balance between thermal stability and electrode integrity.
Solution Approach 2:
The patent employs beforehand cushioning by pre-positioning corrosion-resistant material at the outer peripheries of the excitation electrodes before thermal treatment occurs. This preventive measure creates a protective barrier that cushions against the harmful effects of high-temperature thermal treatment, preventing silver particle coagulation and subsequent delamination or disconnection that would otherwise occur during the thermal stress relief process.
4Volume of moving object
If excitation electrodes are miniaturized, then device size is reduced, but insulation failure risk increases due to migration of silver material
Solution Approach 1:
The patent applies local quality by concentrating corrosion-resistant material at the outer peripheral regions of miniaturized excitation electrodes. In miniaturized devices, the outer periphery represents a larger proportion of the total electrode volume and surface area. By reinforcing this region with migration-resistant material, the patent effectively prevents silver material migration that would cause insulation failure, while maintaining the miniaturized form factor and overall device compactness.
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 solution prevents microscopic dimension reduction during frequency adjustment, enhances chemical and thermal resistance, and maintains reliable electrode performance, even under high-temperature annealing, thereby ensuring stable and precise frequency tuning.
Implementation Method 1
the mass to be removed by the ion beam irradiation is greater at the ridge and the side surfaces of the excitation electrode. Hence, the frequency adjustment rate (the amount of frequency adjustment per unit time) is greater at the outer periphery of each excitation electrode than at the central portion.
Implementation Method 2
The first additive is a metal element which has a lower sputtering yield than silver and which is resistant to corrosion in an etching liquid.
Implementation Method 3
The second additive is an element for forming a solid solution with silver.
Implementation Method 4
the excitation electrodes are irradiated entirely, for example, by an ion beam. Ion beam irradiation to the excitation electrodes decreases the mass of the excitation electrodes and increases the frequency to the target frequency.
Implementation Method 5
In order to reduce thermal stress and strain generated in the production process of a piezoelectric device, a piezoelectric device is exposed to a high temperature for a thermal treatment (annealing).
Data Source
AI summary
A crystal resonator element 2 has excitation electrodes 23a, 23b formed on front and back main surfaces of a crystal resonator plate. Each of the excitation electrodes is made of a ternary alloy containing silver as a major component, a first additive, and a second additive. The first additive is a metal element having a lower sputtering yield than silver and being resistant to corrosion in an etching liquid. The second additive is an element for forming a solid solution with silver. Outer peripheries of the excitation electrodes are first additive-rich regions 9 in which the first additive is rich.