Microactuator Electrode Gap Protection for Piezoelectric Displacement
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Solution Overview
Problem
In hard disk drives, the expansion/contraction displacement of piezoelectric elements in microactuators is limited by the risk of electrode short circuits when increasing the facing area to enhance displacement, as conductive adhesive materials can bridge the electrodes, preventing the desired increase in displacement.
Innovation Solution
A microactuator design featuring a piezoelectric element with a protective insulating layer covering the electrode ends, preventing short circuits by maintaining a gap between electrodes while allowing for increased active length and displacement through strategic electrode placement and connection to conductive pads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the facing area of the electrodes is increased to increase the expansion/contraction displacement, then the amount of displacement is improved, but the risk of short circuit between electrodes increases
Solution Approach 1:
An insulating layer is introduced as an intermediary between the first and second electrodes. This insulating layer prevents direct contact between the electrodes while allowing the electrodes to be positioned closer together, thereby increasing the facing area and expansion/contraction displacement without causing short circuits.
Solution Approach 2:
The physical state or properties of the gap between electrodes are changed by introducing an insulating material. This allows the gap to be reduced (increasing facing area) while maintaining electrical isolation through the insulating properties of the added layer, thus increasing displacement without increasing short circuit risk.
2Reliability
If the gap between electrodes is increased to prevent short circuits, then the reliability is improved, but the amount of displacement of the piezoelectric element decreases
Solution Approach 1:
The insulating layer serves as a mediator that allows the electrodes to be positioned closer together (reducing the gap) while maintaining electrical isolation. This enables both short circuit prevention and increased facing area, thereby resolving the contradiction between reliability and displacement.
Solution Approach 2:
The solution moves from considering only the one-dimensional gap distance between electrodes to introducing a second dimension - the thickness and material properties of the insulating layer. This allows the electrode spacing to be reduced while maintaining electrical isolation through the insulating layer's properties rather than relying solely on increased gap distance.
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 expansion/contraction displacement of the piezoelectric element, increasing the positioning accuracy and range of the magnetic head without electrode short circuits, thereby improving the microactuator's performance.
Implementation Method 1
a piezoelectric element which is mounted on the flexure and includes a piezoelectric substrate formed of a piezoelectric material
Data Source
AI summary
According to one embodiment, a microactuator includes a wiring substrate, and a piezoelectric element connected to first and second connecting pads of the wiring substrate. The piezoelectric element includes a piezoelectric substrate, and a first electrode and a second electrode provided on surfaces of the piezoelectric substrate. The first electrode includes a first electrode portion on an end portion on a first main surface. The second electrode includes a fifth electrode portion having an electrode end which faces the first electrode portion across a gap and provided on the first main surface. The piezoelectric element includes a protective insulating layer covering at lease an end portion of the fifth electrode including the electrode end.