Piezoelectric Device Adhesive Width Profile for Liquid Ejecting Heads
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Solution Overview
Problem
The existing piezoelectric devices used in liquid ejecting heads face challenges in reducing size while maintaining sufficient adhesive strength, as the adhesive used to bond substrates can protrude and interfere with the device's operation, leading to ejection failures due to rough internal surfaces and the difficulty in minimizing the device's size.
Innovation Solution
A configuration where a first substrate with a piezoelectric element and an electrode layer is bonded to a second substrate with a bump electrode using an adhesive that has a greater width in the center than at the ends, ensuring adequate adhesive strength without protrusion, and a manufacturing method involving thermosetting adhesive that contracts and cures while pressed, to maintain a predetermined distance between substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive is used to bond the silicon substrate and the surface on which the piezoelectric element is laminated, then the substrates can be connected, but the adhesive protrudes from the predetermined region and interferes with the vibration region of the vibration plate
Solution Approach 1:
The adhesive is applied selectively only in the non-vibration region of the vibration plate, creating different adhesive conditions in different locations. This local application ensures bonding strength where needed while avoiding interference with the vibration region, thus resolving the contradiction between adhesive strength and protrusion interference.
2Reliability
If the adhesion region is spread with margin to prevent adhesive interference, then adhesive interference is avoided, but the size of the piezoelectric device and liquid ejecting head increases
Solution Approach 1:
The adhesive region is localized to the non-vibration area only, eliminating the need for excessive margins. This precise spatial control maintains adhesion reliability by placing adhesive only where it won't interfere with vibration, while minimizing the overall device size by avoiding unnecessary expansion of the adhesion region.
3Ease of manufacture
If the concave section is created in the sealing plate by etching technique, then the driving circuit can be formed on the surface, but the internal surface becomes rough and desired performance cannot be obtained
Solution Approach 1:
The driving circuit is extracted from the sealing plate surface and relocated to a separate substrate. This separation allows the sealing plate to be etched for concave section formation without compromising surface smoothness, while the driving circuit is fabricated on a different surface that can be properly planarized, thus resolving the contradiction between ease of manufacture and manufacturing precision.
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 configuration allows for a reduction in the size of the piezoelectric device and liquid ejecting head while ensuring sufficient adhesive strength, preventing adhesive protrusion and maintaining device functionality.
Implementation Method 1
a piezoelectric device including a piezoelectric element that is deformed by applying a voltage
Implementation Method 2
adhesive that bonds the first substrate and the second substrate in a state where a distance between the first substrate and the second substrate is maintained
Implementation Method 3
a manufacturing method involving thermosetting adhesive that contracts and cures while pressed, to maintain a predetermined distance between substrates
Data Source
AI summary
A piezoelectric device includes a first substrate that includes a piezoelectric element (32) provided in a first region where bending deformation is allowed and an electrode layer (39) electrically connected to the piezoelectric element (32), a second substrate in which a bump electrode (43) abutting and conducting the electrode layer (39), and having elasticity is formed, and which is disposed so as to face the piezoelectric element (32) with a predetermined space, and adhesive (43) that bonds the first substrate and the second substrate in a state where a distance between the first substrate and the second substrate is maintained. The adhesive (43) has a width in a center portion in a height direction relative to a surface of the first substrate or the second substrate greater than a width in end portions in the same direction.