STO ESD Prevention via Dynamic Disk Potential Control
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Solution Overview
Problem
Current hard disk drives (HDDs) using spin-torque oscillators (STO) for microwave assisted magnetic recording face reliability issues due to electrostatic discharge (ESD) between the STO element and the disk, leading to potential destruction from friction and current flow, especially with the narrow gap between the slider and the disk.
Innovation Solution
A control circuit adjusts the electrical potential of the disk to maintain a potential difference of less than 115 millivolts between the STO element and the disk, using a current-limiting resistor to prevent electrostatic discharge by synchronizing the potential changes with the STO element's conduction and non-conduction states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed voltage is applied to the disk to control potential difference, then electrostatic discharge prevention is improved, but during writing operation the alternating ON/OFF voltage to STO element produces voltage difference that causes current flow and STO destruction
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed voltage application to a dynamic voltage control system. The control circuit dynamically adjusts the disk voltage based on the real-time state of the STO element, ensuring the potential difference remains below the threshold (e.g., 115 mV) regardless of whether the STO is in writing or non-writing mode. This dynamic adjustment prevents ESD while maintaining STO reliability.
Solution Approach 2:
The patent implements feedback by using the state information of the STO element (writing or non-writing mode) to control the voltage applied to the disk. The control circuit receives feedback about the STO's operational state and adjusts the disk voltage accordingly, creating a closed-loop system that maintains safe potential differences and prevents electrostatic discharge.
2Manufacturing precision
If the gap between slider and disk is reduced to increase storage density, then recording density is improved, but the risk of contact and electrostatic discharge between STO element and disk increases
Solution Approach 1:
The patent applies equipotentiality by actively controlling the voltage applied to the disk to match the potential of the STO element, maintaining a potential difference below the ESD threshold. This creates an equipotential condition between the STO element and disk surface, eliminating the electric field that would cause electrostatic discharge, thereby enabling safe operation at reduced gaps for higher recording density.
3Reliability
If STO element and disk come into contact, then friction causes abrasion of protective film and conductive contact, but current flow due to potential difference destroys the STO element
Solution Approach 1:
The patent applies preliminary anti-action by proactively controlling the voltage on the disk to prevent electrostatic discharge before it can occur. The control circuit continuously monitors or anticipates the STO element's state and adjusts the disk voltage in advance to ensure the potential difference never exceeds the ESD threshold, thereby preventing both current flow and the associated harmful effects of friction and abrasion.
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 solution effectively suppresses the flow of current between the STO element and the disk, reducing the risk of damage and maintaining the reliability of HDDs by keeping the potential difference below the threshold that causes destruction, thereby enhancing the operational stability of HDDs.
Implementation Method 1
performing magnetic recording using a spin torque oscillator (STO) element incorporated in the slider
Implementation Method 2
A control circuit adjusts a disk electrical potential to change with an electrical potential of a spin-torque oscillator (STO) element. The control circuit maintains a potential difference of less than about 115 millivolts (mV) between the disk and the STO element.
Data Source
AI summary
A method, apparatus, and system are provided for preventing electrostatic discharge (ESD) in hard disk drives using spin-torque oscillator (STO) for microwave assisted magnetic recording (MAMR). A control circuit adjusts a disk electrical potential with an electrical potential of a spin-torque oscillator (STO) element. The control circuit maintains a potential difference of less than about 115 millivolts (mV) between the disk and the STO element.