Elastic Wave Device Partition Support Wiring Breakage
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Solution Overview
Problem
In elastic wave devices with three-dimensional crossing portions, the short distance between wiring lines and the cover leads to breakage due to contact, and the use of a partition support with different linear expansion coefficients exacerbates the issue under heat loads.
Innovation Solution
The implementation of a partition support on the piezoelectric substrate that covers the step portions of the second wiring line, positioned between the IDT electrodes and the insulating layer, reduces breakage by uniform expansion and contraction, and strategically placed to minimize contact with the cover, enhancing the device's strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a partition support is provided on the three-dimensional crossing portion to prevent contact between the cover and upper wiring line, then the reliability is improved, but the device complexity increases
Solution Approach 1:
An insulating layer is introduced as an intermediary element between the upper wiring line and the partition support. This insulating layer prevents direct contact between the cover and wiring lines while allowing the partition support to maintain its protective function, thereby improving reliability without significantly increasing device complexity
Solution Approach 2:
The patent utilizes vertical stacking to create a three-dimensional crossing portion where wiring lines cross at different heights. By positioning the upper wiring line above the lower wiring line with an insulating layer in between, the design prevents contact between the cover and wiring lines while maintaining a compact footprint, thus improving reliability without proportionally increasing device complexity
2Reliability
If the thickness of the three-dimensional crossing portion is increased to prevent contact, then the reliability is improved, but the distance between wiring lines and cover becomes short, worsening the reliability
Solution Approach 1:
Instead of increasing thickness in the vertical direction, the patent uses horizontal separation by creating a three-dimensional crossing structure. The upper wiring line is positioned above the lower wiring line with an insulating layer, allowing the cover to be placed closer to the wiring lines without causing contact, thus maintaining reliability while reducing the overall device height
3Strength
If a partition support with different coefficient of linear expansion is used, then the structural strength is improved, but breakage due to heat load increases
Solution Approach 1:
The partition support is designed with localized features rather than uniform structure throughout. By providing support only where needed in the three-dimensional crossing portion and using an insulating layer in strategic locations, the design maintains structural strength while reducing areas prone to thermal stress concentration, thereby improving resistance to heat-induced breakage
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
Significantly reduces breakage of wiring lines in three-dimensional crossing portions while maintaining structural integrity and preventing air bubble formation at contact points between the partition support and the cover.
Implementation Method 1
an elastic wave device includes a piezoelectric substrate, an interdigital transducer (IDT) electrode that is disposed on the piezoelectric substrate
Data Source
AI summary
An elastic wave device includes a piezoelectric substrate, IDT electrodes disposed on the piezoelectric substrate, a first wiring line, an insulating layer covering at least a portion of the first wiring line, a second wiring line at least a portion of which is disposed on the insulating layer to provide a three-dimensional crossing portion, a peripheral support including a cavity surrounding the IDT electrodes, the first and second wiring lines, and the insulating layer, a partition support disposed in the cavity, and a cover disposed on the peripheral support and the partition support to cover the cavity. The second wiring line includes a step portion electrically connecting a portion of the second wiring line located on the piezoelectric substrate and a portion of the second wiring line located on the insulating layer to each other. The partition support covers the step portion.