Acoustic Wave Substrate Layout for Thermal Stress and Charge Relief
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Solution Overview
Problem
Existing acoustic wave devices face issues with temperature characteristics, stress accumulation, and electrical charge accumulation due to differences in thermal expansion coefficients between support and piezoelectric substrates, leading to inefficiencies and potential damage to acoustic wave elements.
Innovation Solution
The acoustic wave device design includes a support substrate with a piezoelectric substrate jointed on it, where specific areas of the piezoelectric substrate are removed to minimize stress and electrical charge accumulation, and interconnection lines are formed on the remaining piezoelectric substrate to connect acoustic wave elements, improving temperature characteristics and reducing losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the piezoelectric substrate is fully retained on the support substrate, then the acoustic wave elements can be properly supported and connected, but stress and electrical charge accumulate due to thermal expansion coefficient differences
Solution Approach 1:
The patent applies the extraction principle by removing portions of the piezoelectric substrate in regions where acoustic wave elements are not present. Specifically, the piezoelectric substrate is removed from peripheral areas and areas between acoustic wave elements, while retaining it only in regions where acoustic wave elements are located. This selective removal eliminates the source of stress and electrical charge accumulation (the piezoelectric material itself) without affecting the functional areas, thereby resolving the contradiction between maintaining reliability and reducing stress.
2Ease of manufacture
If the piezoelectric substrate is fully retained, then interconnection lines can be properly formed and connected, but device complexity increases due to unnecessary material and processing
Solution Approach 1:
The patent removes unnecessary portions of the piezoelectric substrate that do not contribute to the functional performance. By extracting the piezoelectric material from areas where acoustic wave elements are not present, the substrate structure is simplified, reducing manufacturing complexity and eliminating unnecessary processing steps while maintaining ease of manufacture in the retained functional areas.
Solution Approach 2:
The patent applies local quality by creating a non-uniform piezoelectric substrate structure where different regions have different properties. The substrate is retained with appropriate thickness in areas requiring acoustic wave element support and interconnection, while being removed or reduced in areas where these components are absent. This localized differentiation optimizes the structure for manufacturing while reducing overall complexity.
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 design enhances the temperature characteristics of acoustic wave elements, reduces stress and electrical charge accumulation, and minimizes losses and damage, thereby improving the reliability and performance of the acoustic wave device.
Implementation Method 1
a piezoelectric substrate that is jointed on the support substrate; a plurality of acoustic wave elements that are provided on the piezoelectric substrate
Implementation Method 2
When a linear thermal expansion coefficient of the support substrate is smaller than that of the piezoelectric substrate, temperature characteristics of the acoustic wave device can be improved
Data Source
AI summary
An acoustic wave device includes: a support substrate; a piezoelectric substrate that is jointed on the support substrate; a plurality of acoustic wave elements that are provided on the piezoelectric substrate; and an interconnection line that is provided on the piezoelectric substrate and couples the plurality of acoustic wave elements, wherein: the piezoelectric substrate of a first area, on which the plurality of acoustic wave elements are provided, is remained; the piezoelectric substrate of a second area, on which the interconnection line is provided, is remained; the piezoelectric substrate of a third area is for cutting the support substrate; and the piezoelectric substrates of a fourth area is other than the first area, the second area and the third area, the fourth area having a fifth area in which at least a part of the piezoelectric substrate is removed.