Elastic Wave Electrode Thickness Layout for Spurious Emission Control
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Solution Overview
Problem
Existing elastic wave devices face challenges in effectively reducing spurious emissions and balancing loss and reflection characteristics due to the design of strip electrodes and end surfaces.
Innovation Solution
The elastic wave device incorporates a first strip electrode with a smaller average thickness than the second strip electrode, and employs a design with inclined or curved shapes and end surfaces to manage spurious emissions and adjust wave propagation, using a manufacturing method that etches both the end surface and strip electrodes simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the first strip electrode has a smaller average thickness than the second strip electrode, then spurious emissions are reduced, but the manufacturing precision requirement increases due to the need for selective thickness control
Solution Approach 1:
The first strip electrode is designed with a different thickness characteristic compared to the second strip electrode. Specifically, the first strip electrode has a smaller average thickness in the direction parallel to the substrate surface, creating local quality differentiation. This thickness variation is achieved through selective removal of material from the first strip electrode, allowing it to reduce spurious emissions while the second strip electrode maintains its original thickness for proper excitation function.
Solution Approach 2:
The strip electrodes are segmented into at least two distinct groups: the first strip electrode with reduced thickness and the second strip electrode with original thickness. This segmentation allows each electrode to perform its specific function optimally - the thinned first electrode for spurious emission reduction and the full-thickness second electrode for effective excitation, thereby resolving the contradiction between reducing harmful emissions and maintaining manufacturing feasibility.
2Object-generated harmful factors
If the end surface is designed to be inclined or curved, then wave propagation is better managed and spurious emissions are reduced, but the device complexity increases
Solution Approach 1:
The end surface of the substrate is designed with curvature rather than being perfectly flat. The end surface may be inclined or curved to manage wave propagation effectively. This curvature helps in directing the elastic wave propagation and reducing spurious emissions by controlling the reflection and scattering of waves at the end surface, thereby reducing harmful emissions through geometric design.
3Productivity
If simultaneous etching of end surface and strip electrodes is used, then manufacturing efficiency is improved, but the difficulty of detecting and measuring increases due to precise pattern control requirements
Solution Approach 1:
The manufacturing process merges the etching operations for the end surface and the strip electrodes into a single simultaneous etching step. This is achieved by forming a mask that covers both the end surface and the strip electrodes, then performing one etching operation that processes both features concurrently. This combination improves manufacturing efficiency by reducing the number of separate processing steps, although it requires precise mask alignment and pattern control.
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 reduces spurious emissions and improves the balance between loss and reflection characteristics, enhancing the performance of the elastic wave device.
Implementation Method 1
a substrate (2) having an end surface (41) and including a piezoelectric body (21)
Implementation Method 2
At least some strip electrodes among the plurality of strip electrodes are each an excitation portion that can excite an elastic wave
Implementation Method 3
The elastic wave device has a structure that reflects a propagating elastic wave
Data Source
AI summary
An elastic wave device includes a substrate having an end surface and including a piezoelectric body, and strip electrodes located above the substrate, each of the strip electrodes extending in parallel. Some of the strip electrodes are excitation portions that can excite an elastic wave, the end surface is parallel to the direction the strip electrodes extend, and located in an elastic wave propagation direction. The plurality electrodes include a first strip electrode located closest to the end surface in the elastic wave propagation direction, and a second strip electrode farther from the end surface than the first strip electrode in the elastic wave propagation direction, the second strip electrode is the excitation portion, and an average thickness of the first strip electrode is smaller than an average thickness of the second strip electrode, in a cross section cut in the elastic wave propagation direction.