Elastic Wave Wire Bridge Layout for Crack-Resistant Routing
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Solution Overview
Problem
Elastic wave devices face issues with cracks and wire breakage due to thermal stress and non-planarities in the inorganic insulating film, particularly at bridged areas where wires intersect, and existing solutions either exacerbate thermal stress or compromise design flexibility and device size.
Innovation Solution
An elastic wave device with an interlayer insulating film made from an inorganic dielectric material, featuring first and second auxiliary wire electrodes that extend from the outer side of the interlayer film to the second wire, and a sloping surface design to reduce stress and enhance contact strength, along with a method involving photolithography-etching and dry etching techniques for manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an inorganic insulating film is used at bridged areas, then thermal stress resistance improves, but cracks and wire breakage occur due to non-planarities
Solution Approach 1:
The patent applies different surface treatments to different regions of the inorganic insulating film. The bridged area is planarized to prevent cracks, while other areas may retain non-planarities. This local differentiation allows the film to provide thermal stress resistance where needed without causing wire breakage at critical bridged locations.
Solution Approach 2:
The inorganic insulating film is formed and planarized before the wires are deposited. This preliminary planarization ensures that the wire deposition occurs on a flat surface, preventing wire breakage during subsequent processing and assembly, while the inorganic material already provides thermal stress resistance.
2Volume of moving object
If a resin support member covers bridged areas, then device size reduces, but thermal stress increases due to coefficient of linear expansion differences
Solution Approach 1:
The patent uses a resin support member that covers most areas of the device to reduce overall size, but specifically excludes coverage of the bridged areas. This local differentiation allows the resin to provide size reduction benefits while the exposed bridged areas avoid thermal stress from the resin's coefficient of linear expansion differences.
Solution Approach 2:
The inorganic insulating film serves as an intermediary between the resin support member and the wires at bridged areas. It provides a thermally stable interface that protects the wires from thermal stress while allowing the resin to cover and protect other areas of the device.
3Strength
If the interlayer insulating film surface is rounded, then crack formation is prevented, but manufacturing complexity increases
Solution Approach 1:
The patent applies a rounding treatment to the surface of the interlayer insulating film at bridged areas. This curvature eliminates sharp edges and corners that would concentrate stress and initiate cracks. The rounding is applied selectively to critical areas rather than the entire film, balancing crack prevention with manufacturing simplicity.
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
Effectively suppresses cracks and wire breakage in the second wire at bridged areas, while maintaining design flexibility and reducing thermal stress, allowing for a smaller device size without compromising performance.
Implementation Method 1
there is still a large difference in the coefficient of linear expansion between the piezoelectric substrate and the resin, and thus there is a problem that a large amount of thermal stress arises in the wires on the insulating layer
Implementation Method 2
A portion of the second wire bridges a portion of the first wire with the interlayer insulating film provided therebetween... it is difficult for cracks and wire breakage to occur in wires on the interlayer insulating film
Data Source
AI summary
An elastic wave device includes interdigital transducer electrodes on a piezoelectric substrate and wires electrically connected to the interdigital transducer electrodes. The wires include a first wire and a second wire. The device further includes an interlayer insulating film made from an inorganic dielectric material and covering a portion of the first wire. A portion of the second wire bridges a portion of the first wire with the interlayer insulating film provided therebetween. In a region, in a bridged area, where the second wire extends from a region on an outer side portion of the interlayer insulating film to above the interlayer insulating film, first auxiliary wire electrodes are provided on the piezoelectric substrate, such that when viewed in plan view, the first auxiliary wire electrodes at least partially overlap with the second wire and extend to within the interlayer insulating film.