Elastic Wave Device Wiring Electrode Stress Relief
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Solution Overview
Problem
Elastic wave devices with multilayer films on support substrates face reliability issues and thermal shock failures due to stress concentration at the wiring electrode's step portion, leading to potential breaks during thermal shock tests.
Innovation Solution
The design includes a spacer layer outside the piezoelectric film with an embedded end portion in the cover layer, reducing stress concentration and enhancing the wiring electrode's reliability by securely supporting the spacer layer and covering the step portion, thereby improving thermal shock resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the wiring electrode extends along the side surface of the multilayer film to the insulating layer, then the electrical connection is achieved, but stress concentration occurs at the step portion leading to breakage during thermal shock tests
Solution Approach 1:
The patent introduces an intermediary structure (the spacer layer configuration) between the wiring electrode and the step portion to reduce stress concentration. The spacer layer is positioned to provide mechanical support and distribute stresses away from the vulnerable step portion of the wiring electrode, preventing breakage during thermal shock tests while maintaining electrical connectivity.
Solution Approach 2:
The patent applies beforehand cushioning by pre-positioning the spacer layer to cushion and absorb thermal expansion stresses before they can concentrate at the wiring electrode's step portion. This preventive measure ensures that the wiring electrode is protected from stress-induced breakage during subsequent thermal shock testing.
2Strength
If the spacer layer is disposed outside the piezoelectric film, then the structural support is improved, but the device complexity increases
Solution Approach 1:
The patent applies universality by designing the spacer layer to serve multiple functions simultaneously: it provides structural support to the multilayer film, reduces stress concentration at the wiring electrode, and maintains the necessary spacing between components. This multi-functionality reduces the need for additional separate structures, thereby limiting the increase in device complexity while achieving improved structural support.
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
The solution significantly increases the reliability of the wiring electrode and its ability to withstand thermal shock tests, reducing the occurrence of breaks and improving the overall structural integrity of the elastic wave device.
Implementation Method 1
a piezoelectric film (2)
Data Source
AI summary
An elastic wave device includes a spacer layer on or above a support substrate and outside a piezoelectric film as seen in a plan view from a thickness direction of the support substrate. A cover layer is disposed on the spacer layer. A through electrode extends through the spacer layer and the cover layer and is electrically connected to the wiring electrode. The wiring electrode includes a first section overlapping the through electrode as seen in the plan view from the thickness direction, a second section overlapping the piezoelectric film as seen in the plan view from the thickness direction, and a step portion defining a step in the thickness direction between the first section and the second section. The spacer layer includes an end portion embedded in the cover layer.