Piezoelectric Actuator Wiring with Selective Electroplating
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Solution Overview
Problem
Existing methods for manufacturing piezoelectric actuators in high-nozzle-density liquid ejection heads face challenges in reducing electrical resistance of wiring portions while maintaining reliability, due to stress issues and non-uniformity in film thickness, leading to performance variations and matching difficulties with other processes.
Innovation Solution
A method involving forming a lower electrode film on an insulating substrate, followed by a piezoelectric film, and then creating slits to expose the lower electrode, with subsequent metal film deposition to increase wire thickness selectively, thereby reducing electrical resistance without thickening the active electrode films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the film thickness of the lower electrode is increased to reduce electrical resistance, then the electrical resistance decreases, but the stress control becomes difficult and reliability declines
Solution Approach 1:
The patent applies local quality by differentiating the thickness of the lower electrode film across different regions. The wire portions (non-active regions) have a greater film thickness to reduce electrical resistance, while the active portions maintain the original thickness to ensure stress control and piezoelectric element reliability. This spatial variation in film thickness allows simultaneous optimization of both electrical performance and mechanical stability.
2Productivity
If a large number of piezoelectric elements are driven simultaneously to achieve high nozzle density, then the nozzle density increases, but the electrical resistance of wiring portions increases
Solution Approach 1:
The patent addresses the electrical resistance issue in high-density configurations by applying local quality to the lower electrode film. Specifically, the wire portions that carry current to multiple piezoelectric elements are given a greater film thickness, reducing their electrical resistance. This allows high nozzle density to be achieved without compromising electrical performance.
3Object-affected harmful factors
If the thickness of the lower electrode film is increased uniformly, then the electrical resistance decreases, but the stress in the film becomes difficult to control
Solution Approach 1:
The patent resolves the stress control issue by implementing local quality in the lower electrode film thickness. The active portions (where piezoelectric elements are located) maintain the original film thickness to ensure proper stress control, while only the wire portions are thickened to reduce electrical resistance. This selective thickening prevents uniform stress increase across the entire film.
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 approach effectively reduces the electrical resistance of wire portions supplying electricity to the piezoelectric film, enhancing the reliability and consistency of the piezoelectric actuator, suitable for high-nozzle-density liquid ejection heads.
Implementation Method 1
depositing a first metal film on the lower wire and thereby making a film thickness of the lower wire greater than a film thickness of the lower electrode film
Implementation Method 2
depositing a second metal film on a portion of the upper electrode film on the insulating layer and thereby making a film thickness of the portion of the upper electrode film on the insulating layer greater than a film thickness of a portion of the upper electrode film that has been deposited directly on the piezoelectric film
Data Source
AI summary
The method of manufacturing a piezoelectric actuator, includes the steps of: forming a lower electrode film on an insulating substrate; forming a piezoelectric film on the lower electrode film; forming a slit on the piezoelectric film to expose a portion of the lower electrode film on an upper surface side of the piezoelectric film; forming an insulating layer which covers a portion of the piezoelectric film; forming an upper electrode film so as to span the insulating layer and the piezoelectric film; forming, on the piezoelectric film, a lower wire in connection with the portion of the lower electrode film exposed through the slit; depositing a first metal film on the lower wire and thereby making a film thickness of the lower wire greater than a film thickness of the lower electrode film; and depositing a second metal film on a portion of the upper electrode film on the insulating layer and thereby making a film thickness of the portion of the upper electrode film on the insulating layer greater than a film thickness of a portion of the upper electrode film that has been deposited directly on the piezoelectric film.