Acoustic Wave Substrate Edge Layout for Spurious Peak Suppression
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Solution Overview
Problem
End surface reflection-type acoustic wave devices experience increased spurious peaks due to chipping on cut surfaces, which existing methods fail to adequately address, particularly for edges extending in the direction of acoustic-wave propagation.
Innovation Solution
The acoustic wave device features a composite substrate with IDT electrodes, where the chipping size on one side face orthogonal to the propagation direction is 1/10 of the wavelength or smaller, and on the other side face in the propagation direction is between ½ and 50 times the wavelength, optimizing reflection and phase changes to suppress spurious peaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the composite wafer is cut using a dicing saw, then the acoustic wave device can be manufactured, but chipping occurs on the cut surfaces causing increased spurious peaks
Solution Approach 1:
The patent applies preliminary action by forming cutting grooves around rectangular areas before dicing. These grooves are created in advance to guide the dicing process and minimize chipping on the cut surfaces, thereby reducing spurious peaks while maintaining manufacturing capability
Solution Approach 2:
The patent converts the harmful effect of chipping into a beneficial outcome by controlling the chipping size to be 1/10 wavelength or smaller. This controlled chipping actually helps suppress spurious peaks by creating appropriate acoustic impedance at the edges, transforming a manufacturing defect into a functional feature
2Reliability
If the cut surface is polished to remove chipping, then spurious peaks are reduced, but manufacturing complexity and time increase
Solution Approach 1:
The patent extracts the harmful large chipping by controlling it to be 1/10 wavelength or smaller through the cutting groove method. This selective removal of only the problematic chipping size range achieves spurious peak suppression without requiring extensive polishing processes
Solution Approach 2:
The patent changes the parameter of chipping size from uncontrolled to precisely controlled (1/10 wavelength or smaller) through the cutting groove technique. This parameter control achieves the desired acoustic performance without adding complex manufacturing steps
3Manufacturing precision
If edges extending in the direction of acoustic-wave propagation are made smooth, then irrelevant acoustic waves are reflected causing increased spurious peaks
Solution Approach 1:
The patent applies asymmetry by treating different edges differently: edges extending orthogonally to acoustic-wave propagation are made smooth (1/10 wavelength chipping), while edges extending in the propagation direction are intentionally left with larger chipping (1/2 to 50 times wavelength). This asymmetric treatment suppresses spurious peaks by preventing unwanted reflections from the propagation-direction edges
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 configuration effectively reduces spurious peaks by controlling reflection and phase changes, ensuring a satisfactory reflection at the desired wavelength and minimizing irrelevant wavelength reflections, while maintaining a high Q factor.
Implementation Method 1
an acoustic wave excited by IDT (interdigital-transducer) electrodes provided on a piezoelectric substrate
Implementation Method 2
acoustic waves reflected by edges of substrates... acoustic wave excited by IDT electrodes provided on a piezoelectric substrate is propagated up to edges of the substrate and is reflected by the edges
Data Source
AI summary
An acoustic wave device is an end surface reflection-type acoustic wave device and includes a substantially rectangular-parallelepiped composite substrate in which a piezoelectric substrate and a supporting substrate are joined together, with a pair of IDT electrodes provided on the substrate in such a manner as to be intercalated with each other. A chipping size in a first side face of the substrate is 1/10 of a wavelength λ of an acoustic wave or smaller, the face extending orthogonally to a direction of acoustic-wave propagation. A chipping size in a second side face of the substrate is larger than the chipping size in the face and is, for example, ½ of the wavelength λ or larger and 50 times the wavelength λ or smaller, the face extending in the direction of acoustic-wave propagation.