Acoustic Wave Device Layout for Thermal Distortion Cancellation
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Solution Overview
Problem
The challenge in mounting acoustic wave devices on a substrate is the mechanical distortion caused by differences in the coefficients of linear expansion between the piezoelectric substrate and the mounting substrate, leading to variations in the characteristics of the acoustic wave device during the reflow process.
Innovation Solution
The solution involves arranging acoustic wave devices with substrates having coefficients of linear expansion that are either higher or lower than the mounting substrate, such that their distortions cancel each other out, reducing mechanical deformation and maintaining the device's characteristics. This is achieved by using substrates like Si for one device and LiNbO3 for another, with a resin substrate having a coefficient of expansion between 8 ppm/°C and 14 ppm/°C, and strategically placing functional elements in regions where distortions are minimized.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If acoustic wave devices with different substrate materials are mounted on a resin substrate, then the coefficients of linear expansion can be balanced to reduce distortion, but the device complexity increases due to material selection constraints
Solution Approach 1:
The invention changes the parameter of linear expansion coefficient by selecting specific substrate materials (Si with 2.6 ppm/°C or laminated materials with 5-10 ppm/°C) to match and balance with the resin substrate's linear expansion coefficient (8-14 ppm/°C), thereby reducing thermal distortion during reflow processing
Solution Approach 2:
The invention uses laminated materials combining Si with other materials (such as metal layers or dielectric layers) to achieve intermediate linear expansion coefficients between pure Si and the resin substrate, enabling better matching and reduced distortion through composite structure
2Area of stationary object
If multiple acoustic wave devices are mounted on one substrate, then space utilization improves, but distortion increases due to cumulative effects of different coefficients of linear expansion
Solution Approach 1:
The invention applies different substrate materials to different device positions on the mounting substrate, selecting materials with appropriate linear expansion coefficients for each device based on its location and functional requirements, thereby locally optimizing distortion compensation
Solution Approach 2:
By varying the linear expansion coefficient parameter of substrate materials across different devices (using Si for some devices, laminated materials for others), the invention balances the cumulative thermal stress effects when multiple devices are mounted on the same resin substrate
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 approach significantly reduces or prevents distortion in the mounting substrate and the acoustic wave devices, thereby maintaining the integrity of their characteristics, as demonstrated by simulation results showing reduced distortion amounts and improved performance.
Implementation Method 1
the piezoelectric substrate of the acoustic wave device and the mounting substrate have different coefficients of linear expansion. As a result, when cooling in the reflow process, mechanical distortion occurs in the acoustic wave device itself due to a difference in the coefficient of linear expansion
Data Source
AI summary
A high-frequency apparatus includes a resin substrate, a first device including a substrate and provided on the resin substrate, and a second device provided adjacent to the first device on the resin substrate. Each of the first device and the second device includes an acoustic wave device. The second device includes a piezoelectric substrate and a functional element provided on the piezoelectric substrate. The substrate of the first device includes Si or a laminated material including Si. The piezoelectric substrate of the second device includes LiTaO3, LiNbO3, or a laminated material including LiTaO3 or LiNbO3. The resin substrate includes glass.