Elastic Wave Electrode Layout to Prevent Thin-Film Cracking
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Solution Overview
Problem
Elastic wave devices face issues with cracking, chipping, and interfacial peeling of piezoelectric thin films due to external forces and the dicing process, as well as breaking of wiring electrodes during the bonding and cutting processes.
Innovation Solution
The design includes a support substrate with a lamination layer film and a piezoelectric thin film, featuring an interdigital transducer electrode and a first insulation layer with a rounded shape that extends from the piezoelectric thin film over the lamination layer film, reducing stress and peeling, and a wiring electrode with a width of at least 6 μm to minimize damage and short-circuiting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a piezoelectric thin film is used in the elastic wave device, then the device achieves proper piezoelectric functionality, but the film is likely to be cracked or chipped by external force during bonding and cutting processes
Solution Approach 1:
A resin layer is introduced between the piezoelectric thin film and the electrode pad, acting as a flexible protective shell that absorbs external forces during bonding and cutting processes, preventing stress transmission to the fragile piezoelectric film while maintaining its piezoelectric functionality
Solution Approach 2:
The resin layer serves as an intermediary element between the electrode pad and the piezoelectric thin film, mediating the mechanical stress during external connection terminal bonding and dicing operations, thereby protecting the piezoelectric film from direct force application
2Ease of operation
If external connection terminals are bonded to the piezoelectric thin film, then external connection is achieved, but stress is applied to the multilayer body causing cracking, chipping, or interfacial peeling
Solution Approach 1:
The resin layer acts as a flexible protective shell that absorbs bonding stress, allowing external connection terminals to be attached to the electrode pad without transmitting damaging forces to the piezoelectric thin film or causing interfacial peeling in the multilayer structure
Solution Approach 2:
The resin layer is pre-positioned between the electrode pad and piezoelectric thin film to provide beforehand cushioning against bonding stress, preventing stress-induced cracking, chipping, or interfacial peeling before the actual bonding process occurs
3Productivity
If the device is cut with a dicing machine, then individual devices are separated, but the force applied during cutting causes cracking, chipping, or interfacial peeling of the piezoelectric thin film
Solution Approach 1:
The resin layer serves as a flexible protective shell that absorbs cutting forces during dicing operations, preventing stress transmission to the piezoelectric thin film and eliminating the need for fragile film handling during device separation
Solution Approach 2:
The resin layer acts as an intermediary that mediates cutting forces between the dicing blade and the piezoelectric thin film, allowing efficient device separation while preventing cutting-induced cracking, chipping, or interfacial peeling
4Reliability
If wiring electrodes extend from the support substrate to the piezoelectric thin film, then electrical connection is achieved, but breaking of the wiring electrode is likely to be generated
Solution Approach 1:
The resin layer provides a flexible protective environment for wiring electrodes, allowing them to be routed and connected without direct exposure to mechanical stresses that would cause breaking, while maintaining electrical connection 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 configuration effectively reduces the likelihood of cracking, chipping, and interfacial peeling of the piezoelectric thin film and breaking of the wiring electrode, enhancing the reliability and durability of the elastic wave device.
Implementation Method 1
a piezoelectric thin film laminated on the lamination layer film
Implementation Method 2
an elastic wave device in which a lamination layer film and a piezoelectric thin film are laminated on a support substrate
Data Source
AI summary
An elastic wave device includes a lamination layer film including a piezoelectric thin film on a support substrate. The lamination layer film is not partially present in a region located in an outer side portion of a region where IDT electrodes are provided. A first insulation layer extends from at least a portion of a region where the lamination layer film is not present to an upper portion of the piezoelectric thin film. A wiring electrode has a width of about 6 μm and extends from the upper portion of the piezoelectric thin film to an upper portion of the first insulation layer, and extends onto a section of the first insulation layer in the region.