Acoustic Wave Element Hole Layout to Prevent Piezoelectric Cracking
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Solution Overview
Problem
Conventional acoustic wave devices with piezoelectric layers, such as lithium niobate or lithium tantalate, are prone to cracking during mounting due to pressure or impact, which can damage the excitation portion including functional electrodes.
Innovation Solution
Incorporating a hole through the piezoelectric layer on a straight line connecting functional electrodes and bumps, reducing the likelihood of crack growth and damage during mounting by providing a pathway for stress relief.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acoustic wave elements are mounted on the wiring substrate via bumps, then electrical connection is achieved, but cracks may occur in the piezoelectric layer due to pressure or impact during mounting
Solution Approach 1:
The piezoelectric layer is segmented by forming holes that divide the continuous layer into separate regions. These holes act as stress relief zones that prevent crack propagation while maintaining the structural integrity of the piezoelectric layer during bump mounting operations
Solution Approach 2:
Holes are formed in the piezoelectric layer before mounting the acoustic wave elements. These pre-formed holes serve as cushioning structures that absorb and distribute the stress and impact forces during the bump mounting process, preventing crack formation in the excitation portion
2Strength
If the piezoelectric layer is made solid without holes, then structural integrity is maintained, but cracks can propagate to the excitation portion including functional electrodes
Solution Approach 1:
The holes in the piezoelectric layer act as intermediary structures between the bumps and the excitation portion. They serve as stress relief zones that intercept and prevent crack propagation from the bump mounting area toward the functional electrodes, thereby protecting the excitation portion while maintaining overall layer integrity
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 effectively reduces or prevents crack formation in the piezoelectric layer, minimizing damage to the excitation portion and ensuring the integrity of functional electrodes during the mounting process.
Implementation Method 1
an acoustic wave element 11, a plurality of bumps 12 electrically connected to the acoustic wave element 11
Data Source
AI summary
An acoustic wave device includes an acoustic wave element, bumps electrically connected to the acoustic wave element, an under-bump metal layer between the acoustic wave element and the bumps, a wiring substrate on which the acoustic wave element is mounted, and an encapsulating body covering the acoustic wave element on the wiring substrate. The acoustic wave element includes a support substrate, a piezoelectric layer on one main surface of the support substrate, and a functional electrode on at least one main surface of the piezoelectric layer. The wiring substrate is electrically connected to the acoustic wave element via the under-bump metal layer and the bumps. The piezoelectric layer includes a hole passing through the piezoelectric layer on at least a portion of a straight line connecting the functional electrode and the bumps to each other.