Inkjet Head Piezoelectric Element Bump Electrode Connection
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Solution Overview
Problem
The configuration of inkjet heads with piezoelectric elements results in high electric resistance due to long lead wiring, which can lead to decreased electric power supply and structural complexity.
Innovation Solution
The use of bump electrodes connected through a conductive film and elastic resin, eliminating the need for long lead wiring between the circuit board and piezoelectric elements, and employing a photosensitive adhesive to maintain the interval and prevent deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead wiring is used to connect the piezoelectric element to the terminal, then electrical connection is achieved, but electric resistance increases due to long wiring distance
Solution Approach 1:
The patent extracts the lead wiring from the connection path by introducing bump electrodes that directly connect the piezoelectric element to the terminal through the sealing plate, eliminating the need for long external lead wiring and reducing electrical resistance
Solution Approach 2:
The bump electrodes serve as intermediary connection points between the piezoelectric element and the terminal, providing a direct electrical pathway through the sealing plate that reduces the effective wiring distance and resistance
2Ease of operation
If lead wiring is drawn outside the sealing plate to connect electrodes, then electrical connection is established, but wiring length increases and resistance increases
Solution Approach 1:
The patent transitions from planar lead wiring outside the sealing plate to three-dimensional bump electrodes that penetrate through the sealing plate, creating vertical connection paths that reduce the effective wiring length and resistance
3Loss of energy
If the circuit board is placed close to the piezoelectric element, then connection distance is reduced, but the piezoelectric element may be deformed
Solution Approach 1:
The bump electrodes act as intermediaries that maintain a controlled gap between the circuit board and the piezoelectric element, allowing electrical connection while preventing direct contact that could cause deformation
Solution Approach 2:
The patent segments the connection path into distinct components (bump electrodes, sealing plate, piezoelectric element), allowing independent optimization of each component's position and function to balance electrical connection and mechanical stability
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 reduces electrical resistance, ensures accurate power supply to the piezoelectric elements, simplifies the structure, and prevents damage to the pressure chamber-forming plate and circuit board, while allowing for a more compact inkjet head design.
Implementation Method 1
The inkjet head is configured to drive the piezoelectric element to cause a pressure variation of liquid in a pressure chamber, thereby jetting liquid from a nozzle using this pressure variation. When voltage is applied to the lower electrode layer and the upper electrode layer through the flexible cable and the like, the piezoelectric layer between the electrode layers is deformed.
Implementation Method 2
the bump electrode includes elastic resin, and a conductive film covering a surface of the resin
Data Source
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AI summary
An inkjet head includes: a pressure chamber-forming plate in which a plurality of pressure chambers each communicating with a nozzle are formed; a vibration plate that defines one surface of each pressure chamber and allows for deformation of a defining region thereof; a piezoelectric element formed by stacking a first electrode layer, a piezoelectric layer, and a second electrode layer in a region corresponding to the pressure chamber in an order from a surface of the vibration plate, which is opposite to the pressure chamber; and a circuit board that is arranged at an interval from the vibration plate, with a plurality of bump electrodes interposed therebetween, and outputs a signal for driving the piezoelectric element, wherein the first electrode layer is formed independently for each piezoelectric element, the second electrode layer is formed continuously across the plurality of piezoelectric elements, and at least part of the bump electrodes is electrically connected with the first electrode layer and the second electrode layer in a region outside of the defining region.