Piezoelectric Electrode Bonding With Roughened Silicon Contact Surface
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Solution Overview
Problem
Existing piezoelectric elements with silicon-containing electrode layers experience increased electrical resistance at the bonding interface due to insufficient adhesion between the electrode layers, leading to reduced performance.
Innovation Solution
The piezoelectric element design includes a second electrode layer with a connecting surface having a higher surface roughness than the major surface, where a metal connecting electrode is bonded, and the connecting surface is processed to remove natural oxide films, ensuring improved adhesion and reduced contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon-based electrode layer is bonded to a metal connecting electrode, then electrical connection is established, but adhesion is insufficient leading to increased electrical resistance
Solution Approach 1:
The patent applies different surface roughness characteristics to different regions of the electrode layer. The connecting surface (where metal bonding occurs) has a surface roughness Ra of 0.03 µm or more, while the major surface (adjacent to piezoelectric layer) maintains lower roughness. This local differentiation improves adhesion at the bonding interface without compromising the overall electrode performance.
Solution Approach 2:
The connecting surface is pre-processed to increase surface roughness before bonding to the metal connecting electrode. This preliminary surface treatment creates a rougher interface that enhances mechanical interlocking and adhesion, preventing subsequent bonding failures and resistance increases.
2Strength
If surface roughness is increased to improve adhesion, then bonding strength improves, but manufacturing complexity increases
Solution Approach 1:
The surface roughness modification is applied locally only to the connecting surface rather than the entire electrode layer. This selective processing reduces manufacturing complexity compared to treating the whole surface, while still achieving the adhesion improvement where it is most needed at the bonding interface.
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 enhances adhesion between the silicon-based electrode layer and the metal connecting electrode, reducing electrical resistance and improving electromechanical conversion efficiency and device characteristics.
Implementation Method 1
a piezoelectric layer (110), a first electrode layer (120), a second electrode layer (130), and a connecting electrode (140)... improving electromechanical conversion efficiency
Data Source
AI summary
A piezoelectric element includes a piezoelectric layer, a first electrode layer, a second electrode layer, and a connecting electrode. The piezoelectric layer includes first and second surfaces, and a through-hole. The second electrode layer is adjacent to the second surface of the piezoelectric layer. The second electrode layer faces the through-hole. The second electrode layer includes silicon as a major component. The connecting electrode is on a connecting surface of the second electrode layer, and the connecting surface faces the through-hole. The connecting electrode is made of a metal. A surface roughness of the connecting surface is greater than a surface roughness of a major surface. The major surface is a portion, other than the connecting surface, of a surface of the second electrode layer, and the surface is adjacent to the piezoelectric layer.