Piezoelectric Electrode Structure With Ni Etch-Stop Hole Protection
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Solution Overview
Problem
Existing piezoelectric elements face issues where etching to form a through-hole can unintentionally create holes in electrode layers opposite to the single-crystal piezoelectric layer, leading to potential cracking and insufficient contact areas.
Innovation Solution
The introduction of a third electrode layer made of Ni or Ni alloy with a lower etching rate than the second electrode layer, positioned outside the edge of the through-hole, acts as an etching stop layer, preventing holes from forming in the opposite electrode layer and reducing stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If etching is performed to form a through-hole in the single-crystal piezoelectric layer, then the through-hole is successfully formed, but the etching may continue and create unwanted holes in the electrode layer and other members
Solution Approach 1:
The patent applies preliminary action by forming a protective film on the electrode layer before etching the single-crystal piezoelectric layer. This protective film is prepared in advance to prevent etching damage to the electrode layer, thereby solving the problem of unwanted hole formation while maintaining through-hole formation precision
Solution Approach 2:
The protective film acts as an intermediary layer between the etching process and the electrode layer. It mediates the etching process by being selectively removed after serving its protective function, preventing direct contact between the etchant and the electrode layer, thus avoiding unwanted hole formation
2Stress or pressure
If the electrode layer is made thinner to reduce stress, then stress concentration is reduced, but the contact area becomes insufficient
Solution Approach 1:
The patent segments the electrode structure into multiple layers (first electrode layer and second electrode layer) with different functions. The first electrode layer provides electrical contact while the second electrode layer provides mechanical support and stress distribution, allowing the contact area to be sufficient while stress concentration is reduced through the multi-layer configuration
Solution Approach 2:
The patent extends the electrode structure in the vertical dimension by creating a multi-layer electrode configuration. This dimensional expansion allows the electrodes to provide both adequate contact area in the horizontal plane and stress distribution capability through the vertical stacking, resolving the contradiction between thinning for stress reduction and maintaining contact area
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 effectively prevents unwanted hole formation, reduces cracking, ensures adequate contact area, and improves electrical resistance, enhancing the reliability and efficiency of the piezoelectric element.
Implementation Method 1
a piezoelectric element including a piezoelectric layer
Data Source
AI summary
A piezoelectric element includes a second electrode layer on a second surface of a single-crystal piezoelectric layer. A hole continuous with a through-hole is provided in the second electrode layer. The second electrode layer is made of Pt, Ti, Al, Cu, Au, Ag, Mg, or an alloy including at least one of the metals as a main ingredient. A third electrode layer is on one side of the second electrode layer opposite to the single-crystal piezoelectric layer. The third electrode layer includes at least a portion outside of an edge of the hole with a distance maintained relative to the edge of the hole when viewed in a direction perpendicular or substantially perpendicular to the second surface. The third electrode layer is made of Ni or an alloy including Ni as a main ingredient.