Liquid Ejecting Head ZrO2 Crystal Orientation Stress Balance
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Solution Overview
Problem
Liquid ejecting heads with insulating films composed of ZrO2 and elastic films composed of SiO2, when actuated by piezoelectric elements, often suffer from residual stress leading to cracking due to external forces, which compromises their structural integrity and functionality.
Innovation Solution
A liquid ejecting head design featuring a vibrating plate with a stacked structure of SiO2 and ZrO2 layers, where the interface region has a higher degree of orientation of the (−211) crystal face, and the surface-layer region has a higher degree of orientation of the (−111) and (002) crystal faces, as measured by X-ray diffraction, to introduce residual compressive stress at the interface and balance stress across the film, enhancing the structural strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulating film composed of ZrO2 is used in the vibrating plate, then the electrical insulation performance is improved, but residual tensile stress causes cracking when external force is applied
Solution Approach 1:
The patent changes the crystallographic orientation parameters of the ZrO2 insulating film by controlling the sputtering process conditions (substrate temperature, sputtering gas flow ratio, power density). This results in a specific orientation where the (-211) crystal face has higher degree of orientation than other faces, which fundamentally alters the stress characteristics of the film from tensile to compressive, thereby preventing cracking while maintaining insulation performance
Solution Approach 2:
The patent creates a composite structure by stacking multiple films with different materials and stress characteristics: the ZrO2 insulating film with compressive stress, the SiO2 elastic film, and the piezoelectric element. This composite structure allows the compressive stress in the ZrO2 film to counterbalance the tensile stress generated during actuation, preventing cracking while maintaining the functional integrity of each layer
2Stability of the object's composition
If the degree of orientation of crystal faces in the ZrO2 layer is increased to improve stress balance, then the manufacturing precision requirements increase
Solution Approach 1:
The patent identifies specific controllable parameters in the sputtering process (substrate temperature range, sputtering gas flow ratio, power density) that directly influence the crystal orientation of ZrO2. By optimizing these parameters within specified ranges, the process achieves consistent (-211) orientation with high degree of orientation ratio, making the manufacturing process robust and repeatable
Solution Approach 2:
The patent replaces direct mechanical control of crystal orientation with process parameter control. Instead of physically aligning crystals during deposition, the method uses thermal and electromagnetic field parameters (substrate temperature, RF power, gas flow) to guide spontaneous crystal orientation toward the desired (-211) face, simplifying the manufacturing control system
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 design improves the strength of the vibrating plate by reducing cracking propensity and maintaining appropriate residual stress balance, leading to enhanced reliability and performance of the liquid ejecting head.
Implementation Method 1
a piezoelectric element that displaces the vibrating plate
Implementation Method 2
a degree of orientation of the (−211) crystal face of the second layer, measured by using an X-ray diffraction method
Data Source
AI summary
The interface region may include a region in which first intensity is higher than second intensity and in which the first intensity is higher than third intensity, where a degree of orientation of the (−211) crystal face of the second layer is denoted as the first intensity, the degree of orientation of the (−111) crystal face of the second layer is denoted as the second intensity, and the degree of orientation of the (002) crystal face of the second layer is denoted as the third intensity. The surface-layer region may include a region in which the first intensity is higher than the third intensity and in which the second intensity is higher than the third intensity.