Contact Pad Thermal Protrusion for Head-Disk Spacing Control
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Solution Overview
Problem
Conventional thermal fly-height control (TFC) methods in magnetic disk drives are uncertain regarding the absolute spacing of the reader from the disk, leading to potential damage due to contact between the AlTiC edge or the reader and the hard disk, causing corrosion, malfunction, or performance issues.
Innovation Solution
A thin film stack with a magnetic transducer and a contact pad, where the heater induces thermal protrusion, ensuring the contact pad protrudes farther than the magnetic transducer, allowing controlled head-medium contact without damaging the disk or reader, by positioning the heater behind the contact pad relative to the media-facing side.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional TFC calibration method is used to control head-disk spacing, then the reader can be positioned close to the disk surface for proper reading and writing, but the contact location is uncertain and may be away from the reader, causing uncertainty in absolute spacing
Solution Approach 1:
A separate contact pad structure is introduced as an intermediary element between the reader and the disk surface. This contact pad serves as a dedicated calibration interface that allows the reader to be calibrated without requiring direct contact between the reader and disk, thereby eliminating the uncertainty in absolute spacing measurement while maintaining proper reading and writing capability.
2Manufacturing precision
If TFC heating is applied to move the reader closer to the disk surface, then proper reading and writing can be enabled, but contact between the reader or AlTiC edge and the disk may cause damage, corrosion, or malfunction
Solution Approach 1:
The contact pad acts as a protective intermediary that absorbs the mechanical contact stress during TFC calibration. By designating a specific sacrificial contact area separate from the reader and AlTiC edge, the reader and critical components are protected from direct contact with the disk, preventing damage, corrosion, and malfunction while still enabling proper spacing control.
Solution Approach 2:
The contact pad is designed as a sacrificial element that may wear or degrade during calibration procedures. By using a dedicated contact pad rather than protecting the entire reader structure, the system accepts that this specific component may have limited lifespan during calibration, thereby protecting the more valuable and critical reader elements from damage.
3Manufacturing precision
If the reader is made to contact the disk during TFC calibration, then the spacing can be controlled, but the contact may cause wear of the carbon overcoat and corrosion of the head
Solution Approach 1:
The contact pad serves as a dedicated intermediary surface that is specifically designed to contact the disk during calibration. This separates the calibration function from the reader elements, concentrating the wear and potential corrosion effects on the contact pad rather than on the reader or carbon overcoat, thereby protecting the critical components from harmful wear and corrosion.
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 ensures deterministic calibration of head-disk spacing, minimizing the risk of damage during TFC touchdown, maintaining performance and preventing corrosion, by using a contact pad with a higher thermal expansion coefficient than the reader material.
Implementation Method 1
heating the components of the reader/writer causing thermal expansion of the materials, which results in the reader/writer transducers protruding closer to the surface of the hard disk
Data Source
AI summary
A system according to one embodiment includes a thin film stack having a magnetic transducer and a contact pad; and a heater in the thin film stack for inducing thermal protrusion of a media-facing side of the thin film stack, wherein the thin film stack is characterized by the contact pad protruding farther than the magnetic transducer upon the thin film stack being heated by the heater. A method for calibrating a protrusion of a magnetic head includes increasing a thermal protrusion of a magnetic head to induce head-medium contact; determining that the head has contacted the medium, wherein a portion of the head that contacts the medium is a contact pad or overcoat of the contact pad; determining parameters for inducing a desired amount of protrusion based in part on the determination that the head has contacted the medium; and storing the parameters.