Ring Electrode Passivation for Inkjet Piezoelectric Moisture Protection
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Solution Overview
Problem
Ring-shaped top electrodes on piezoelectric actuators in inkjet devices leave areas of the piezoelectric layer uncovered, exposing them to moisture that can degrade the layer and cause the actuators to break down.
Innovation Solution
A ring electrode design with an annular lower and upper portion is used, where the annular lower portion is disposed on the piezoelectric layer, and a moisture barrier layer covers the remaining uncovered areas, with the annular upper portion extending to cover parts of the moisture barrier layer, ensuring protection from moisture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a ring-shaped top electrode is deposited directly on the piezoelectric layer, then the electrode structure is simplified and manufacturing is easier, but areas of the piezoelectric layer remain uncovered and exposed to moisture causing degradation
Solution Approach 1:
The patent applies local quality by creating different structures in different regions: the ring electrode provides electrical contact at specific locations while the moisture barrier layer provides protection in uncovered areas. This regional differentiation allows the piezoelectric layer to have both electrical functionality and moisture protection simultaneously, resolving the contradiction between manufacturing simplicity and reliability.
Solution Approach 2:
The patent uses composite materials by combining the conductive ring electrode with a moisture barrier layer (such as silicon nitride or silicon oxide). This composite structure integrates both electrical functionality and moisture protection, allowing the system to achieve reliability without compromising manufacturing ease, as both layers can be deposited using standard semiconductor fabrication processes.
2Reliability
If the piezoelectric layer is fully covered by electrode material, then moisture protection is improved, but the ring electrode structure cannot be implemented and solid/central electrodes are required
Solution Approach 1:
The patent applies local quality by creating different structures in different regions: the ring electrode provides electrical contact at specific locations while the moisture barrier layer provides protection in uncovered areas. This regional differentiation allows the piezoelectric layer to have both electrical functionality and moisture protection simultaneously, resolving the contradiction between manufacturing simplicity and reliability.
Solution Approach 2:
The moisture barrier layer acts as an intermediary between the piezoelectric layer and the environment. It fills the protective function that would otherwise require complete electrode coverage, allowing the ring electrode structure to be used without compromising reliability. The intermediary layer enables the system to achieve both goals without increasing device complexity.
3Productivity
If ring-shaped electrodes are used to improve fluid ejection performance, then ejection efficiency is enhanced, but uncovered piezoelectric areas are exposed to moisture causing breakdown
Solution Approach 1:
The patent applies local quality by creating different structures in different regions: the ring electrode provides electrical contact at specific locations while the moisture barrier layer provides protection in uncovered areas. This regional differentiation allows the piezoelectric layer to have both electrical functionality and moisture protection simultaneously, resolving the contradiction between manufacturing simplicity and reliability.
Solution Approach 2:
The patent uses composite materials by combining the conductive ring electrode with a moisture barrier layer (such as silicon nitride or silicon oxide). This composite structure integrates both electrical functionality and moisture protection, allowing the system to achieve reliability without compromising manufacturing ease, as both layers can be deposited using standard semiconductor fabrication processes.
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 solution effectively prevents moisture degradation of the piezoelectric layer, enhancing the durability and longevity of the inkjet device by reducing the risk of breakdown and maintaining efficient fluid ejection performance.
Implementation Method 1
The piezoelectric actuator includes a layer of piezoelectric material that changes geometry (or actuates) in response to a voltage applied across the piezoelectric layer by a pair of opposing electrodes
Implementation Method 2
a moisture barrier layer covering a remainder of the piezoelectric layer over the pumping chamber that is not covered by the annular lower portion of the ring electrode
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
An inkjet device includes: a pumping chamber; a piezoelectric layer disposed above the pumping chamber; a ring electrode having an annular upper portion and an annular lower portion disposed on the piezoelectric layer; and a moisture barrier layer covering a remainder of the piezoelectric layer over the pumping chamber that is not covered by the annular lower portion. The annular upper portion includes an annular inner upper portion and an annular outer upper portion. The annular lower portion includes an annular inner lower portion and an annular outer lower portion. The annular inner upper portion extends inwardly from the annular inner lower portion to cover a portion of the moisture barrier layer surrounded by the annular inner lower portion. The annular outer upper portion extends outwardly from the annular outer lower portion to cover a portion of the moisture barrier layer that surrounds the annular outer lower portion.