Elastic Wave Device Thermal Deformation Control
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Solution Overview
Problem
Existing elastic wave devices using anisotropic piezoelectric substrates like LiTaO3 and LiNbO3 experience significant thermal deformation due to temperature changes, leading to frequency shifts and potential substrate damage from thermal expansion.
Innovation Solution
The elastic wave device incorporates a first surface acoustic wave chip with a piezoelectric substrate having a Y-axis rotation angle neither at 0 degrees nor an integer multiple of 90 degrees, mounted on a package board with a slanted crystal Z-axis orientation extending toward the outer side, reducing thermal deformation and stabilizing frequency characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a piezoelectric substrate with standard crystal orientation is used, then the device structure is simple and manufacturing is easy, but thermal deformation occurs significantly when temperature changes, causing frequency shifts
Solution Approach 1:
The patent changes the crystal orientation parameters of the piezoelectric substrate, specifically setting the Y-axis rotation angle to neither 0 degrees nor an integer multiple of 90 degrees, and slanting the Z-axis orientation to extend toward the outer side portion. This parameter modification reduces thermal deformation and improves frequency stability under temperature changes.
2Reliability
If the piezoelectric substrate is positioned at the center of the package board, then the mounting structure is simple, but thermal deformation is significant due to heat from the power amplifier
Solution Approach 1:
The patent applies asymmetry by shifting the piezoelectric substrate from the center of the package board to a position that is not centrally located. This asymmetric positioning reduces thermal deformation by avoiding the highest heat concentration area while maintaining effective acoustic wave propagation.
3Strength
If the crystal Z-axis is oriented perpendicular to the substrate surface, then the manufacturing process is straightforward, but thermal expansion causes substrate damage
Solution Approach 1:
The patent modifies the crystal cutting parameters by slanting the Z-axis orientation so it extends toward the outer side portion from the central portion. This angular adjustment reduces thermal expansion stress and prevents substrate damage while maintaining manufacturability through precise crystal cutting.
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 significantly reduces thermal deformation of the piezoelectric substrate, thereby stabilizing the temperature characteristics of the elastic wave device and minimizing the risk of substrate damage from thermal expansion.
Implementation Method 1
a first surface acoustic wave chip including a first piezoelectric substrate and including an upper surface and a lower surface that oppose each other, and a first IDT electrode provided on the first piezoelectric substrate
Implementation Method 2
The temperature of an elastic wave device changes influenced by heat emitted from a power amplifier (PA) in use that is disposed in the vicinity of the device, or, the like. An elastic wave device using an interdigital transducer (IDT) electrode that is provided in an anisotropic piezoelectric substrate such as LiTaO3, LiNbO3, or the like, has a problem that a change in frequency occurs in the piezoelectric substrate in proportion to a magnitude of thermal deformation.
Data Source
AI summary
An elastic wave device is configured such that a first surface acoustic wave chip including a piezoelectric substrate is mounted on a package board, a center of the first surface acoustic wave chip is shifted from a center of the package board when viewed from above, and a crystal Z-axis orientation of the piezoelectric substrate of the first surface acoustic wave chip is slanted to extend toward an outer side portion from a central portion of the package board as it progresses toward an upper surface from a lower surface of the piezoelectric substrate.