Au-Ag-Pd Ternary Alloy Resonator Electrode for Frequency Stability
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Solution Overview
Problem
Existing piezoelectric resonators, such as quartz crystal resonators, face challenges in achieving low production dispersion and stable temporal frequency properties while maintaining a lower material cost, as conventional electrode materials like Au are expensive, and alternatives like Ag suffer from oxidation and sulfidation issues.
Innovation Solution
A ternary alloy composed of Au, Ag, and Pd is used as an excitation electrode, where Au ensures chemical stability, and Ag and Pd have opposing effects on the temporal frequency property, balancing to achieve low production dispersion and stable long-term frequency stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Ag is used as electrode material to reduce cost, then material cost is reduced, but oxidation and sulfidation occur causing poor temporal frequency property
Solution Approach 1:
The patent uses a composite electrode structure with multiple layers: Ag base layer (for cost reduction and electrical conductivity), Pd intermediate layer (to prevent oxidation and sulfidation), and Au top layer (for chemical stability and low production dispersion). This composite structure resolves the contradiction by combining materials with different properties to achieve both cost reduction and reliability improvement.
Solution Approach 2:
The Pd layer serves as an intermediary between the Ag base layer and the Au top layer, preventing direct contact between Ag and oxidizing/sulfidizing environments while also preventing Au diffusion into the Ag layer. This intermediary layer resolves the oxidation and sulfidation issues that would otherwise occur with Ag electrodes.
2Reliability
If Au is used as electrode material to ensure chemical stability and low production dispersion, then temporal frequency property is improved, but material cost increases
Solution Approach 1:
The patent applies local quality by using different materials in different layers of the electrode structure. The Au layer is applied only where chemical stability and low production dispersion are critical (at the top surface contacting the quartz crystal), while the Ag base layer provides cost reduction and electrical conductivity in the bulk. This resolves the contradiction by concentrating expensive material only where absolutely necessary.
Solution Approach 2:
The multi-layer composite electrode structure allows combining Au's superior temporal frequency properties with Ag's cost advantage, achieving both goals simultaneously through material composition rather than using pure Au throughout.
3Strength
If Cr, Ni, or NiCr alloy is used as underlayer electrode to ensure adhesion strength, then adhesion is improved, but compatibility with quartz crystal and temporal frequency property may be compromised
Solution Approach 1:
The Ag base layer serves as an intermediary between the quartz crystal and the Au/Pd electrode layers, providing both mechanical adhesion and electrical conductivity while being chemically compatible with the quartz crystal. This intermediary approach resolves the contradiction between adhesion strength and temporal frequency property.
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 ternary alloy suppresses production dispersion and maintains temporal frequency stability comparable to or better than Au, reducing material costs by alloying with less expensive metals and minimizing oxidation effects.
Implementation Method 1
by sputtering or vapor deposition in a vacuum chamber (in a vacuum atmosphere), the excitation electrode 6 and the extraction electrode 6a are formed on the quartz crystal element 2
Implementation Method 2
the excitation electrode 6a is irradiated with a gas ion, and thus the surface of the excitation electrode 6 is partially removed by abrasion to reduce the mass of the excitation electrode 6
Data Source
AI summary
An electrode material capable of making more satisfactory the dispersion at the time of production and the aging property of a resonator than Au and capable of reducing the price as compared to Au. An resonator electrode material including a ternary alloy composed of Au and two metals M1 and M2, and being used as an excitation electrode to excite oscillation in a piezoelectric element, wherein the two metals M1 and M2 are, respectively, (a) metal M1: a metal exhibiting a tendency to decrease the temporal frequency property (Δf1/f1) from the reference value f1, and (b) metal M2: a metal exhibiting a tendency to increase the temporal frequency property (Δf1/f1) from the reference value f1. The metal M1 is preferably at least any one of Ag, Al and Ni, and the metal M2 is preferably at least any one of Pd, Ru, Pt, Ir, Rh and Cu.