HAMR Write Head Flying Height Control via Multi-Source Thermal Management
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Solution Overview
Problem
Current data storage devices face challenges in precisely controlling the flying height of read/write heads over disk surfaces, particularly in heat assisted magnetic recording (HAMR) and microwave assisted magnetic recording (MAMR) processes, due to varying heat sources with different time constants, leading to inefficiencies in data writing and potential head damage.
Innovation Solution
A method involving pre-heating and feed-forward control using combined power from the write head coil, thermal flying height heater, and HAMR laser light to stabilize head protrusion, along with feedback control to manage laser power drop-offs, ensuring consistent flying height and reduced risk of mechanical contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pre-heating operation uses combined power from write head coil, thermal flying height heater, and HAMR laser light to increase head protrusion, then flying height control precision is improved, but device complexity increases due to multiple coordinated heat sources
Solution Approach 1:
The patent combines three separate heat sources (write head coil, thermal flying height heater, and HAMR laser light) into a unified pre-heating system that works synergistically to control head protrusion. This merging allows coordinated thermal management to achieve precise flying height control during the pre-heating operation that precedes data writing.
Solution Approach 2:
The patent implements a pre-heating operation that occurs before the actual data writing process. This preliminary thermal preparation stabilizes the head protrusion by activating all three heat sources in advance, ensuring optimal flying height conditions are established before writing begins, thereby improving overall control precision.
2Productivity
If feedback control is applied to manage laser power drop-offs, then writing efficiency is improved, but control system complexity increases
Solution Approach 1:
The patent implements a feedback control mechanism that continuously monitors laser power levels during the writing operation. When power drop-offs are detected, the system automatically adjusts the laser power compensation to maintain consistent heating效果, thereby preserving writing efficiency despite the added control complexity.
3Force
If thermal expansion is used to push pole pieces closer to disk surface, then magnetic field strength is improved, but risk of mechanical contact increases
Solution Approach 1:
The patent dynamically adjusts thermal parameters (heating power, duration, and distribution across three heat sources) to control the degree of thermal expansion. By precisely modulating these parameters during the pre-heating and writing operations, the system optimizes magnetic field strength while maintaining safe clearance between the pole pieces and disk surface, preventing mechanical contact.
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 approach enhances data storage precision and reduces the risk of head damage by dynamically controlling flying height, improving writing efficiency and maintaining signal strength while minimizing mechanical contact risks.
Implementation Method 1
data is written to the disk medium using a write head which generates a high localized magnetic field which aligns magnetic domains within the disk
Implementation Method 2
thermal flying height control which employs an electrical heater (with mW powers) to heat the pole pieces of the head
Implementation Method 3
resulting in nm-level thermal expansion which pushes the pole pieces slightly closer to the spinning disk surface
Implementation Method 4
One purpose for this light source may be to locally heat the disk medium, thereby momentarily lowering the coercivity and thus reducing the required writing current. This writing process is known as Heat Assisted Magnetic Recording, or HAMR
Implementation Method 5
The distance between the head and the disk is called the flying height since the head is said to flying above the disk on a cushion of compressed air which is entrained by the rapid rotation of the disk
Data Source
AI summary
A data storage device and method for improved flying height control (TFC) in a HAMR or MAMR system employing three heat sources to control the head protrusion: write coil current, TFC heater current, and media exciter power. The TFC heater is used to pre-heat the write head. The media exciter may be operated at a either a zero level or a low level below that required for the HAMR or MAMR process, optionally serving as an additional source of heat to the write head. The HAMR or MAMR data writing process commences only after the head protrusion has been increased and stabilized. During data writing, the media exciter power is increased to the higher level required to heat the disk medium in an HAMR or MAMR process and the TFC heater power is slightly reduced to maintain the total heat into the head approximately constant.