Piezoelectric Device Substrate Thickness Design
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Solution Overview
Problem
The decreasing thickness of pressure chamber-formed substrates in liquid ejection heads leads to reduced stiffness, causing deformation and potential separation of substrates bonded together, which affects the reliability of piezoelectric devices used in applications like inkjet printers and biochips.
Innovation Solution
A piezoelectric device design where the first substrate with an empty chamber has a thicker thickness in the opening peripheral area compared to the outside, or gradually increases in thickness towards the empty chamber, to prevent substrate separation by managing deformation stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of the pressure chamber-formed substrate is decreased to downsize the liquid ejection head, then the size of the liquid ejection head is reduced, but the stiffness of the substrate decreases causing deformation and separation
Solution Approach 1:
The substrate is designed with non-uniform thickness, where the thickness varies in the opening peripheral area compared to other areas. This local variation in thickness provides enhanced stiffness at critical locations (opening peripheral area) while maintaining overall miniaturization of the liquid ejection head, thus resolving the contradiction between size reduction and stiffness maintenance
Solution Approach 2:
The thickness parameter of the substrate is changed spatially to optimize performance. By adjusting the thickness distribution pattern (making it thicker in the opening peripheral area), the substrate achieves sufficient stiffness to prevent deformation and separation while allowing the overall device size to be reduced
2Productivity
If the pitch of pressure chambers is narrowed to increase packaging density, then the packaging density is improved, but the stiffness of partition walls decreases leading to substrate deformation
Solution Approach 1:
The partition walls are designed with locally enhanced thickness in the opening peripheral area, providing increased stiffness at critical locations where deformation would most affect performance. This allows narrower spacing between pressure chambers while maintaining sufficient structural rigidity through localized reinforcement rather than uniformly increasing all dimensions
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 design enhances the reliability of the piezoelectric device by suppressing substrate separation and maintaining adhesion, reducing the risk of nozzle clogging and ink discharge defects.
Implementation Method 1
A piezoelectric element that includes a lower electrode layer, a piezoelectric layer of a piezoelectric material such as titanate zirconate (PZT), and an upper electrode layer is formed
Implementation Method 2
a flexible diaphragm... On the diaphragm, a piezoelectric element... The liquid ejection head of the structure applies a voltage to deform the pressure chambers
Implementation Method 3
the adhesive that bonds the pressure chamber-formed substrate 93 and the communication substrate 94 comes off
Data Source
AI summary
A piezoelectric device includes a first substrate having an empty chamber, a diaphragm defining a surface of the empty chamber, a piezoelectric element formed by stacking a first electrode layer, a piezoelectric layer, and a second electrode layer in sequence from the diaphragm side, the piezoelectric element provided on the side of the diaphragm opposite to the empty chamber, and a second substrate provided on the side of the first substrate opposite to the diaphragm. The thickness of at least a part of the first substrate in an opening peripheral area of the empty chamber is thicker than the thickness in an area outside the opening peripheral area.