Piezoelectric Device Moisture Shielding Layer
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Solution Overview
Problem
Ink jet recording heads with piezoelectric actuators face issues due to moisture invasion, leading to delamination and cracks between layers, especially in high temperature and high humidity environments, as zirconium oxide becomes brittle and prone to damage.
Innovation Solution
A piezoelectric device with a substrate, diaphragm, and piezoelectric actuator laminated in a specific order, featuring layers of silicon, metal elements like chromium and titanium, and silicon nitride, with a zirconium layer between the diaphragm and the actuator, and a moisture shielding layer on the actuator side to prevent moisture invasion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diaphragm with an elastic film and insulator film is used in a piezoelectric actuator, then the basic functionality is achieved, but moisture invades the diaphragm in high temperature and high humidity environments, causing the zirconium oxide layer to become brittle and leading to delamination and cracks
Solution Approach 1:
The diaphragm is divided into multiple functional layers: an elastic film layer (first layer) providing mechanical flexibility, and an insulator film layer (second layer) providing moisture barrier and electrical insulation. This segmentation allows each layer to specialize in its function, with the insulator film specifically protecting against moisture invasion that causes brittleness in zirconium oxide.
Solution Approach 2:
The invention uses a composite structure combining an elastic film (e.g., silicon oxide) and an insulator film (e.g., zirconium oxide, silicon nitride) to create a diaphragm that simultaneously provides mechanical elasticity and moisture resistance. This composite material approach resolves the contradiction by integrating materials with complementary properties.
2Reliability
If the insulator film is formed by thermal oxidation of zirconium, then good electrical insulation is achieved, but the zirconium oxide becomes brittle when moisture invades, causing delamination and cracks
Solution Approach 1:
The elastic film acts as an intermediary layer between the insulator film and the piezoelectric actuator. This intermediate layer absorbs stress and prevents direct transmission of mechanical stresses that would otherwise cause delamination and cracks in the brittle zirconium oxide insulator film, while maintaining electrical insulation performance.
Solution Approach 2:
The invention changes the physical and chemical parameters of the diaphragm structure by selecting specific materials with appropriate properties: the elastic film provides mechanical compliance while the insulator film provides electrical insulation and moisture resistance. By optimizing material composition and layer thickness, the system achieves both electrical insulation and resistance to delamination.
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 suppresses moisture invasion, prevents embrittlement of the zirconium oxide layer, and reduces the risk of delamination and cracks, enhancing the durability and reliability of the ink jet recording head.
Implementation Method 1
a piezoelectric actuator provided on the diaphragm, and causes a pressure change in the ink in the pressure chamber by driving the piezoelectric actuator
Implementation Method 2
The elastic film is formed by thermally oxidizing one surface of the silicon single crystal substrate
Implementation Method 3
The insulator film is formed by thermally oxidizing a layer of zirconium alone formed on the elastic film by a sputtering method or the like
Data Source
AI summary
A substrate, a diaphragm, and a piezoelectric actuator are laminated in this order in a first direction, the diaphragm includes a first layer containing silicon as a constituent element, a second layer disposed between the first layer and the piezoelectric actuator, and containing any one or both of at least one metal element selected from the group made of chromium, titanium, aluminum, tantalum, hafnium, and iridium, and silicon nitride, as a constituent element, and a third layer disposed between the second layer and the piezoelectric actuator and containing zirconium as a constituent element, and a fourth layer containing any one or both of at least one metal element selected from the group made of chromium, titanium, aluminum, tantalum, hafnium, and iridium, and silicon nitride, as a constituent element is provided on the third layer on a piezoelectric actuator side.