Liquid Ejecting Head Substrate Adhesion for Crack Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Piezoelectric elements in liquid ejecting heads, such as ink jet recording heads, experience cracks due to tensile stress from substrates during the manufacturing process, leading to breakage and reduced durability and reliability.
Innovation Solution
A method involving the formation of piezoelectric elements with a longer width in a reference direction on a first substrate, followed by adhering a second substrate with a lower thermal expansion coefficient in the same direction at a temperature lower than normal, applying compression stress to reduce tensile stress and prevent cracking, and using a carbon fiber composite material for the second substrate to enhance durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the piezoelectric element is formed with a standard substrate adhesion process at normal temperature, then the manufacturing process is simple, but tensile stress causes cracks in the piezoelectric layer
Solution Approach 1:
The patent changes the adhesion temperature parameter from normal temperature to a lower temperature (e.g., room temperature or below). This temperature parameter change causes the substrate to have reduced thermal expansion, thereby reducing tensile stress on the piezoelectric layer and preventing cracks while maintaining manufacturing feasibility
Solution Approach 2:
The patent utilizes the thermal expansion properties of the substrate material. By adhering the piezoelectric element at a lower temperature where the substrate has lower thermal expansion, the tensile stress during subsequent heating and cooling cycles is minimized, preventing crack formation in the piezoelectric layer
2Reliability
If the film thickness of the lower electrode is adjusted to relax tensile stress, then crack occurrence is reduced, but the manufacturing process becomes troublesome
Solution Approach 1:
Instead of adjusting the film thickness parameter of the lower electrode, the patent changes the adhesion temperature parameter. This alternative parameter change achieves stress relaxation without requiring complex thickness control processes, thereby maintaining manufacturing simplicity while improving reliability
3Strength
If the piezoelectric element operates under tensile stress from the substrate, then the substrate provides structural support, but cracks occur in the piezoelectric layer along the widthwise direction
Solution Approach 1:
The patent utilizes thermal expansion differences by adhering at a lower temperature. This ensures the substrate provides structural support while minimizing thermal expansion-induced tensile stress that would otherwise cause cracks in the piezoelectric layer during normal operation
Solution Approach 2:
The patent applies preliminary anti-action by pre-adhering the piezoelectric element at a lower temperature before normal operation. This preliminary condition counteracts the tensile stress that would develop during subsequent heating cycles, preventing crack formation before it can occur
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 method effectively suppresses crack formation in the piezoelectric layer, improving the durability and reliability of the liquid ejecting head by reducing tensile stress and maintaining accurate ink droplet landing positions through controlled thermal expansion.
Implementation Method 1
using a first thermal expansion coefficient in a first direction on an adhesion surface with the first substrate less than a second thermal expansion coefficient in a second direction orthogonal to the first direction and the first thermal expansion coefficient less than a thermal expansion coefficient of the first substrate
Implementation Method 2
the piezoelectric element of the deflection vibration mode is deformed in a short side direction (widthwise direction) when a voltage is applied
Data Source
AI summary
Provided is a method of manufacturing a liquid ejecting head, the method including forming a piezoelectric element having a width in a reference direction longer than a width in an orthogonal direction orthogonal to the reference direction on a first substrate, and adhering a second substrate to a surface of the first substrate opposed to the piezoelectric element at a temperature lower than a normal temperature, wherein, in the adhering of the second substrate, the second substrate is adhered such that the first direction of the second substrate is adjusted to the reference direction, using a first thermal expansion coefficient in a first direction on an adhesion surface with the first substrate, the first thermal expansion coefficient is less than a second thermal expansion coefficient in a second direction orthogonal to the first direction and the first thermal expansion coefficient is less than a thermal expansion coefficient of the first substrate.