Elastic Wave Resonator Support Structure Against Film Cracking
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Solution Overview
Problem
Elastic wave devices with piezoelectric thin films are prone to cracking and chipping due to external forces during bonding and dicing, and interfacial peeling occurs during the connection of external terminals, leading to device damage and reduced strength.
Innovation Solution
The elastic wave device incorporates a support substrate with a multilayer film including a piezoelectric thin film and additional layers, featuring a first and second support layer surrounding the interdigital transducer electrode, an insulating layer extending beyond the multilayer film, and a cover sealing a cavity, which reduces interfacial peeling and enhances sealing performance, while the first and second support layers are disposed on the insulating layer to prevent cracking and chipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a piezoelectric thin film is used in the elastic wave device, then the device can function as intended with proper piezoelectric properties, but cracking and chipping easily occur due to external forces during bonding and dicing
Solution Approach 1:
A support structure comprising a first support layer and a second support layer is provided beneath the piezoelectric thin film. The first support layer is positioned directly under the piezoelectric thin film, and the second support layer is positioned under the first support layer. This layered support structure absorbs and distributes external forces before they reach the piezoelectric thin film, preventing cracking and chipping during bonding and dicing processes while maintaining the piezoelectric properties needed for device function.
2Ease of manufacture
If bonding is performed to connect external terminals, then electrical connection is achieved, but stress is applied to the multilayer body causing cracking and chipping of the piezoelectric thin film
Solution Approach 1:
The first support layer is positioned directly beneath the piezoelectric thin film before bonding operations. This support layer absorbs the stress applied during bonding of external terminals, preventing the stress from being transmitted to the piezoelectric thin film and causing cracking or chipping, while still allowing the bonding process to proceed.
3Productivity
If dicing is performed to divide the mother structure, then individual devices are produced, but cracking and chipping of the piezoelectric thin film occur due to forces during dicing
Solution Approach 1:
The first support layer and second support layer are positioned beneath the piezoelectric thin film before dicing operations. These support layers distribute and absorb the mechanical forces applied during dicing, preventing cracking and chipping of the piezoelectric thin film while allowing the dicing process to successfully separate individual devices from the mother structure.
4Ease of manufacture
If the multilayer body is structured for terminal connection, then external terminals can be connected, but interfacial peeling occurs during connection
Solution Approach 1:
The first support layer is positioned directly beneath the piezoelectric thin film before terminal connection operations. This support layer prevents interfacial peeling by distributing the stresses and forces applied during terminal connection, maintaining the stability of the multilayer body's interface while allowing external terminals to be successfully connected.
5Ease of operation
If a hollow portion is created for electrode facing, then the interdigital transducer electrode can face the hollow portion, but the elastic wave device is damaged when pressure is applied to the cover due to the hollow portion being crushed
Solution Approach 1:
The first support layer and second support layer are positioned beneath the piezoelectric thin film and extend into the hollow portion region. These support layers provide structural reinforcement to the hollow portion, preventing it from being crushed when pressure is applied to the cover, while still maintaining the configuration that allows the interdigital transducer electrode to face the hollow portion for proper operation.
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 significantly reduces cracking and chipping of the piezoelectric thin film, prevents interfacial peeling, and improves the sealing performance of the device, resulting in enhanced strength and reliability.
Implementation Method 1
a piezoelectric thin film (4) and a low acoustic velocity film (3)
Data Source
AI summary
An elastic wave device includes a multilayer film stacked on a support substrate. A first support layer surrounds a region including interdigital transducer electrodes. A second support layer is disposed in the region surrounded by the first support layer. A cover is fixed on the first support layer and the second support layer so as to close a cavity defined by the first support layer. The multilayer film is partially disposed on the support substrate, and an insulating layer is disposed in at least a portion of a region in which the multilayer film is not disposed. At least one of the first support layer and the second support layer is disposed on the insulating layer.