Interdigital Transducer Electrode Composition for Lower Resistance
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Solution Overview
Problem
The electrical resistance of comb-shaped electrode portions in acoustic wave devices, particularly in interdigital transducer electrodes, is not sufficiently lowered when an element M is precipitated at the crystal grain boundary of the CuM alloy grain, as described in Japanese Unexamined Patent Application Publication No. 2004-153654.
Innovation Solution
An acoustic wave device with an interdigital transducer electrode comprising a layer of electrode material that includes a base element A and an additive B, where A and B are two types of elements that do not form a compound in a binary phase diagram, and B is granularly dispersed in A, effectively lowering the electrical resistance. Specifically, using Cu as the base element and Ag as the additive, which are dispersed through heat treatment to form a supersaturated solid solution, preventing the formation of intermetallic compounds that increase resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If element M is precipitated at the crystal grain boundary of the CuM alloy grain, then the structural integrity of the electrode is improved, but the electrical resistance is not sufficiently lowered
Solution Approach 1:
The patent changes the distribution state of additive element M from boundary precipitation to granular dispersion within the crystal grains. This parameter change in the microstructure distribution enables simultaneous achievement of low electrical resistance and high reliability, resolving the technical contradiction between structural integrity and electrical resistance reduction.
Solution Approach 2:
The patent creates local quality differences by dispersing additive element M as granules within the Cu base element matrix, rather than uniform precipitation at boundaries. This localized granular distribution optimizes both the electrical conductivity in the bulk material and the structural integrity at grain boundaries, resolving the contradiction between these two properties.
2Strength
If a CuM alloy layer is formed with element M precipitated at crystal grain boundaries, then the mechanical strength is improved, but the electrical resistance remains high
Solution Approach 1:
The patent transforms the microstructural parameter from boundary precipitation to granular dispersion within grains. This parameter change allows the material to achieve both high mechanical strength through grain refinement and low electrical resistance through homogeneous distribution of additive elements in the matrix, resolving the contradiction between strength and electrical resistance.
Solution Approach 2:
The patent creates a composite structure where additive element M exists as dispersed granules within the Cu base element matrix. This composite microstructure combines the advantages of both elements: the ductility and electrical conductivity of Cu with the strength-enhancing and resistance-reducing effects of dispersed M granules, resolving the technical contradiction.
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
The electrical resistance of the interdigital transducer electrode is effectively lowered, enhancing the electric power handling capability and mechanical strength, while maintaining a crystal grain diameter within a range that supports these improvements.
Implementation Method 1
B is granularly dispersed in A, effectively lowering the electrical resistance. Specifically, using Cu as the base element and Ag as the additive, which are dispersed through heat treatment to form a supersaturated solid solution
Implementation Method 2
dispersed through heat treatment to form a supersaturated solid solution
Implementation Method 3
a piezoelectric substrate and an interdigital transducer electrode on the piezoelectric substrate
Data Source
AI summary
An acoustic wave device includes a piezoelectric substrate and an interdigital transducer electrode on the piezoelectric substrate. The interdigital transducer electrode includes a layer including an electrode material including a base element A and an additive B, where a metal element serving as the base element is denoted by A, and an element serving as the additive is denoted by B. The base element A and the additive B are two types of elements that do not form a compound in a binary phase diagram. The additive B is granularly dispersed in the base element A in the electrode material.