Elastic Wave Device Electrode Stress Balancing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional elastic wave devices experience warping and breaking of piezoelectric substrates during manufacturing due to internal stress, leading to reduced manufacturing yield.
Innovation Solution
The elastic wave device employs a comb-shaped electrode with a matte copper plating film having larger particle diameter, lower Young's modulus, and tensile stress, combined with a bright copper plating film with smaller particle size, higher modulus, and compressive stress, which balances and reduces total stress on the substrate, along with a sealing resin to enhance mechanical strength and bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single type of copper plating film is used for electrodes, then the manufacturing process is simple, but the piezoelectric substrate experiences warping and breaking due to unbalanced internal stress
Solution Approach 1:
The electrode structure is segmented into two distinct copper plating films: a first copper plating film with tensile stress and a second copper plating film with compressive stress. This segmentation allows each film to have different stress characteristics that can be independently optimized to balance the overall internal stress on the piezoelectric substrate, preventing warping and breaking while maintaining manufacturing simplicity.
Solution Approach 2:
The invention changes the stress parameter of the copper plating films by using different plating conditions or compositions. The first copper plating film is designed with tensile stress, while the second copper plating film is designed with compressive stress. By controlling these stress parameters, the total internal stress on the piezoelectric substrate is balanced, resolving the contradiction between simple electrode structure and substrate integrity.
2Reliability
If electro-plating is used for electrode films, then electrical conductivity is improved, but particle size variation causes inconsistent stress distribution
Solution Approach 1:
Different regions of the electrode structure are assigned different local qualities through the use of two distinct copper plating films. The first copper plating film has specific particle size characteristics producing tensile stress, while the second copper plating film has different particle size characteristics producing compressive stress. This local differentiation of quality allows each region to contribute differently to stress distribution, achieving uniform overall stress while maintaining high electrical conductivity through electro-plating.
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 reduces warping and breaking of the piezoelectric substrate, improves manufacturing yield, and ensures mechanical strength and electrical performance by balancing internal stresses and densities of the electrodes.
Implementation Method 1
The first electrode and the second electrode may be made of a film produced by electro-plating
Data Source
AI summary
An elastic wave device includes a piezoelectric substrate, a comb-shaped electrode above an upper surface of the piezoelectric substrate, a wiring connected to the comb-shaped electrode, an element cover above the upper surface of the piezoelectric substrate for covering the comb-shaped electrode across a space, a first electrode above an upper surface of the element cover, a sealing resin above the upper surface of the piezoelectric substrate for covering the element cover and the first electrode, a terminal electrode above an upper surface of the sealing resin, and a second electrode passing through the sealing resin for electrically connecting the first electrode with the terminal electrode. The first and second electrodes are made of films produced by electro-plating. The diameter of plating particles of the first electrode may be larger than that of plating particles of the second electrode.