Multi-Layer Resonator Electrode Structure for Stable Package Bonding
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Solution Overview
Problem
Existing piezoelectric resonator elements face instability in mechanical and electrical coupling due to insufficient bonding strength between the resonator element and the package, primarily because of inadequate thickness of the pad electrode, leading to unstable vibration characteristics and electrical coupling.
Innovation Solution
A resonator element with a substrate having a thin-wall and thick-wall part, featuring a multi-layered electrode structure where the pad electrodes are thicker than the excitation and extraction electrodes, ensuring sufficient bonding strength and reduced sheet resistance, and a resonator device with a package that houses the element using a bonding member for secure fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the thickness of the pad electrode is reduced to achieve higher frequency, then the frequency is improved, but the bonding strength between the resonator element and the package deteriorates
Solution Approach 1:
The electrode structure is segmented into multiple functional layers: the pad electrode (for bonding), the extraction electrode (for electrical coupling), and the excitation electrode (for vibration generation). Each layer has optimized thickness independent of the others, allowing the pad electrode to maintain sufficient thickness for bonding strength while the excitation electrode can be thin for high frequency operation
Solution Approach 2:
Different regions of the electrode structure have different thickness characteristics tailored to their specific functions. The pad electrode region has greater thickness for mechanical bonding, while the excitation electrode region has minimal thickness for high frequency resonance, achieving local optimization of both bonding strength and frequency performance
2Volume of moving object
If the thickness of the pad electrode is reduced, then the device size is reduced, but the mechanical coupling stability deteriorates
Solution Approach 1:
The electrode system is divided into separate functional segments where the pad electrode maintains adequate thickness for mechanical coupling stability, while other electrode regions are minimized for size reduction, achieving both compact dimensions and reliable mechanical coupling
Solution Approach 2:
The pad electrode region is locally optimized with sufficient thickness to ensure mechanical coupling stability, while other parts of the electrode structure are minimized for size reduction, creating local quality variations that satisfy both requirements
3Reliability
If the thickness of the extraction electrode is increased to reduce sheet resistance, then the electrical coupling is improved, but the device complexity increases
Solution Approach 1:
The electrical coupling function is segmented between the extraction electrode and the pad electrode. The extraction electrode can be thin since the pad electrode provides the primary electrical connection to the package, reducing the complexity and material usage of the extraction electrode while maintaining electrical coupling reliability
Solution Approach 2:
The electrode thickness is locally optimized based on functional requirements: the pad electrode region has greater thickness for both mechanical and electrical coupling, while the extraction electrode region can be thinner, creating a non-uniform thickness profile that reduces overall device complexity
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 enhances the mechanical and electrical reliability of the resonator element by maintaining stable vibration characteristics and ensuring robust bonding between the resonator element and the package, thereby improving the overall performance and reliability of the resonator device.
Implementation Method 1
a substrate (10) made of a piezoelectric material
Data Source
AI summary
A resonator element includes a substrate including a thin-wall part and a thick-wall part, and an electrode part including an excitation electrode, a pad electrode, and an extraction electrode, wherein the electrode part includes a first electrode layer arranged in the pad electrode placement area and the first area on the substrate, a second electrode layer which is arranged in an area overlapping the first electrode layer on the first electrode layer, and which is larger in thickness than the first electrode layer, a third electrode layer which is arranged throughout an area overlapping the pad electrode placement area and the first area in a plan view on the second electrode layer, and an area overlapping the second area and the excitation electrode placement area in a plan view on the substrate, and which is smaller in thickness than the second electrode layer, and a fourth electrode layer which is arranged in an area overlapping the third electrode layer on the third electrode layer, and which is smaller in thickness than the second electrode layer.