Piezoelectric Actuator Repolarization for HGA Precision
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Solution Overview
Problem
Monolayer type thin film piezoelectric actuators face characteristic reduction due to fluctuations or reversals in piezoelectric polarization direction, which complicates their structure and increases manufacturing costs, and reduces their precision and reliability in high-density hard disk drives.
Innovation Solution
A method for manufacturing a head gimbal assembly using a monolayer type thin film piezoelectric actuator with a pair of piezoelectric laminates, each having a single piezoelectric layer, where repolarization treatment is applied to restore the original polarization direction after stress, and electrical connections are made to allow opposite-phase expansion and contraction, simplifying circuitry and enhancing displacement range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a monolayer type thin film piezoelectric actuator is used, then the structure is simplified and manufacturing cost is reduced, but the piezoelectric polarization direction fluctuates or reverses under stress causing characteristic reduction
Solution Approach 1:
The patent applies preliminary repolarization treatment to the piezoelectric layer before the actuator is subjected to stress during assembly. This preliminary action establishes a stable polarization direction that prevents subsequent fluctuation or reversal when mechanical stress is applied, thereby maintaining characteristic stability while using a simple monolayer structure
Solution Approach 2:
The patent applies a preliminary electric field in the opposite direction to counteract the stress-induced polarization reversal. By applying this counteracting electric field during assembly, the piezoelectric layer's polarization direction is protected from fluctuation or reversal, ensuring reliable operation of the simplified monolayer actuator
2Reliability
If a two-layer type thin film piezoelectric actuator is used, then the piezoelectric polarization direction stability is improved, but the structure becomes more complicated and manufacturing cost increases
Solution Approach 1:
The patent changes the electrical parameter (applying a preliminary electric field) rather than changing the structural parameter (adding layers). This allows the monolayer actuator to achieve the same polarization stability as a two-layer actuator without increasing structural complexity, thereby resolving the contradiction between reliability and device complexity
3Ease of manufacture
If a monolayer type thin film piezoelectric actuator is used, then the manufacturing process is simplified, but the precision and reliability in high-density hard disk drives are reduced
Solution Approach 1:
The preliminary repolarization treatment ensures that the piezoelectric layer maintains its polarization direction under the mechanical stress of assembly and operation. This prevents characteristic reduction that would otherwise degrade positioning precision, allowing the simplified monolayer actuator to achieve high-precision operation in hard disk drives
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 method effectively suppresses characteristic reduction and enhances the precision and reliability of the thin film piezoelectric actuator by restoring polarization direction and allowing opposite-phase operation, improving the displacement range and simplifying manufacturing and circuitry.
Implementation Method 1
if it is subjected to stress, for example, upon fixing it to a suspension, an electric field is generated in the piezoelectric layer by a positive piezoelectric effect, which produces polarization in the piezoelectric body
Implementation Method 2
a first repolarization treatment step for performing repolarization treatment to the first piezoelectric layer by applying voltage between the first electrode layer and the second electrode layer such that, after the fixing step, an electric field having a direction that orients from the first electrode layer to the second electrode layer is generated in the first piezoelectric layer
Data Source
AI summary
A method for manufacturing an head gimbal assembly (HGA) according to the present invention is comprised of: a step for preparing a thin film piezoelectric actuator including a first piezoelectric laminate having a first piezoelectric layer, and a second piezoelectric laminate having a second piezoelectric layer; a step for preparing a suspension; a fixing step for fixing the thin film piezoelectric actuator to the suspension; a first repolarization treatment step for performing repolarization treatment to the first piezoelectric layer after the fixing step; and a second repolarization treatment step for performing repolarization treatment to the second piezoelectric layer after the fixing step.