Piezoelectric Actuator Bonding with Non-Flat Surface
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Solution Overview
Problem
In known piezoelectric actuators, the flexible substrate bonded to the piezoelectric element experiences abnormal vibrations that lead to stress concentration and potential separation due to its own resonance, causing instability and premature detachment.
Innovation Solution
A piezoelectric actuator design where the flexible substrate is bonded to a surface with degraded flatness, using a conductive bonding member with low elastic modulus, such as an anisotropic conductive adhesive, to distribute stress and enhance bonding strength, thereby preventing separation and ensuring long-term stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the flexible substrate is bonded to a main surface with good flatness, then the bonding area is maximized, but the flexible substrate undergoes abnormal vibrations and stress concentration occurs at the base portion, causing separation
Solution Approach 1:
The patent applies local quality by creating a non-flat region specifically at the bonding area between the flexible substrate and piezoelectric element, while keeping other regions flat. This localized modification reduces stress concentration at the bonding interface without sacrificing overall bonding area, thereby improving bonding reliability while maintaining adequate bonding coverage.
2Reliability
If a conductive bonding member is used to bond the flexible substrate, then electrical connection is achieved, but stress concentration occurs during vibration, leading to separation over time
Solution Approach 1:
The patent changes the geometric parameter of the bonding surface by introducing a non-flat region, which modifies the stress distribution parameters during vibration. This parameter change reduces peak stress concentration at the bonding interface, allowing the conductive bonding member to maintain both electrical connection reliability and bonding strength over time.
3Ease of manufacture
If the flexible substrate is bonded to a flat surface, then manufacturing is simplified, but resonance of the flexible substrate causes abnormal vibrations and separation
Solution Approach 1:
The patent converts the harmful effect of stress concentration during vibration into a beneficial design feature by intentionally creating a non-flat bonding region. This design modification allows the bonding interface to accommodate vibration-induced stresses without causing separation, effectively converting the harmful vibration effect into a controlled design parameter that enhances reliability.
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 allows for stable, long-term operation of the piezoelectric actuator without substrate separation, even under prolonged drive conditions, by reducing stress concentration and enhancing bonding reliability through the use of a conductive adhesive with low elastic modulus and improved bonding area.
Implementation Method 1
a part of the flexible substrate is bonded to the one main surface via a conductive bonding member
Implementation Method 2
piezoelectric actuators that use bimorph-type piezoelectric elements
Data Source
AI summary
A piezoelectric actuator, a piezoelectric vibration apparatus and a portable terminal are disclosed. The actuator includes a piezoelectric element, a flexible substrate and a bonding layer. The piezoelectric element includes a laminate in which inner electrodes and piezoelectric layers are alternatively stacked; and surface electrodes on a first main surface of the laminate, each electrically connected to some of the inner electrodes, respectively. The flexible substrate includes a wiring conductor that is electrically connected to the surface electrodes. The bonding layer is located between a part of flexible substrate and the first main surface. At least a region, where the flexible substrate is bonded, of the first main surface has a flatness worse than a flatness of an second main surface which is opposed to the first main surface.