Acoustic Wave Substrate Grinding Layout for Corner Stress Relief
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Solution Overview
Problem
Acoustic wave devices face separation issues between the support and piezoelectric substrate due to stress applied during grinding, particularly at corner portions, leading to potential detachment.
Innovation Solution
The acoustic wave device design includes a piezoelectric substrate with an interdigital transducer electrode and a support structure featuring a rectangular frame with a cavity, where the grinding trace on the substrate's second main surface leads to the corner portion of the support, with angles between the support sides and the grinding trace maintained at 9.5° or less, preventing separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the piezoelectric substrate is ground to be thinned, then the substrate thickness is reduced and manufacturing precision is improved, but stress is applied between the side walls and the piezoelectric substrate causing separation at corner portions
Solution Approach 1:
The invention applies local quality by creating a recess portion at the corner portion of the support where stress concentrates during grinding. This recess portion has a different structural property (reduced thickness or void space) compared to the rest of the support, allowing it to accommodate stress without causing separation. The recess is positioned specifically at the corner where the side walls meet the substrate, addressing the local stress concentration issue while maintaining the overall integrity of the support structure.
2Adaptability or versatility
If the support structure is added to surround the IDT electrode, then device functionality is improved, but stress concentration at corner portions increases leading to separation
Solution Approach 1:
The recess portion creates a local structural variation at the corner of the support. This local modification allows the corner region to have different mechanical properties (lower stress concentration) compared to the main body of the support. The recess acts as a stress relief feature specifically where the side walls converge, enabling the support to maintain its surrounding functionality while preventing stress-induced separation.
Solution Approach 2:
The recess portion serves as a pre-designed stress absorption zone that cushions the impact of grinding stress before it can propagate to cause separation. By providing this recess space in advance at the vulnerable corner portion, the structure is prepared to accommodate stress concentrations that will occur during the grinding process, preventing failure before it happens.
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 or prevents the separation of the support from the piezoelectric substrate, ensuring structural integrity and reliability during manufacturing and operation.
Implementation Method 1
a piezoelectric substrate that includes a first main surface and a second main surface that oppose each other; an interdigital transducer (IDT) electrode provided on the first main surface of the piezoelectric substrate
Data Source
AI summary
An acoustic wave device includes a piezoelectric substrate that includes first and second main surfaces, an IDT electrode on the first main surface, a support having a rectangular or substantially rectangular frame shape and including a cavity, first and second sides, and a first corner portion connected to the first and second sides, and the support being provided on the first main surface such that the cavity surrounds the IDT electrode, and a cover on the support and covering the cavity. A straight or substantially straight grinding trace is provided on the second main surface. The grinding trace leads to the first corner portion as viewed in plan. One of an angle between the first side and the grinding trace and an angle between the second side and the grinding trace as viewed in plan is about 9.5° or less.