Thin-Film Magnetic Head Thermal Expansion Layer Design
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Solution Overview
Problem
Conventional thin-film magnetic heads with heating means struggle to achieve small magnetic spacing due to thermal protrusions, leading to abnormal signal outputs and physical damage, while also facing challenges with high power consumption, which is inadequate for mobile devices with limited power supply.
Innovation Solution
A thin-film magnetic head design featuring a substrate with concave portions containing thermal expansion layers and a heating conductive layer positioned above the thermal expansion layer, with a spacer layer in between, allowing for precise control of magnetic spacing through controlled heating, reducing power consumption and minimizing thermal asperities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a heater is provided near or inside the magnetic head element to control magnetic spacing, then the magnetic spacing can be reduced to the order of 10 nm, but the trailing portion of the overcoat layer protrudes more toward the magnetic disk surface, causing thermal asperities and potential contact damage
Solution Approach 1:
The heating function is segmented from the magnetic head element structure. Instead of placing the heater directly near or inside the head element, the heating means is positioned on the rear surface of the slider substrate, separating the heating function from the read/write function to prevent thermal asperities while maintaining magnetic spacing control capability
Solution Approach 2:
The slider substrate acts as an intermediary medium between the heating means and the magnetic head element. The heating means heats the slider substrate, which then thermally expands to protrude the head end surface toward the magnetic disk, indirectly achieving magnetic spacing control without direct thermal contact between the heater and head element
2Reliability
If the head end surface is separated from the magnetic disk surface by a required amount to avoid contact, then contact damage is prevented, but the magnetic spacing cannot be efficiently set to an adequately small value
Solution Approach 1:
The magnetic spacing is made dynamically adjustable through thermal expansion. The slider substrate and head end surface are designed to protrude toward the magnetic disk when heated, allowing the magnetic spacing to be dynamically reduced from a larger initial separation to an adequately small value during operation, while maintaining reliability by controlling the protrusion amount
3Manufacturing precision
If more power is supplied to the heater to achieve sufficient protrusion of the head end surface, then writing and reading performance is improved, but the power consumption increases, which is inadequate for mobile devices with limited power supply
Solution Approach 1:
The heating is localized to specific regions of the slider substrate through strategically positioned heating means. By concentrating thermal energy only where needed (in the slider substrate beneath the head end surface), the system achieves sufficient head end surface protrusion with minimal power consumption, avoiding unnecessary heating of other slider regions
Solution Approach 2:
The system utilizes thermal expansion parameter changes of the slider substrate material. By selecting materials with appropriate thermal expansion coefficients and designing the slider substrate geometry, the system achieves large head end surface protrusion (sufficient for magnetic spacing reduction) with small temperature increases, thereby reducing the power required for heating
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 design effectively achieves smaller magnetic spacing with reduced power consumption, enhancing writing and reading performance while preventing physical damage and ensuring stable operation in devices with limited power supply.
Implementation Method 1
at least one heating means positioned directly above the at least one thermal expansion layer
Implementation Method 2
the amount of protrusion of a trailing portion of an overcoat layer covering the head elements toward the magnetic disk surface due to heat generated from the heater
Data Source
AI summary
A thin-film magnetic head that the protrusion of the head end surface due to heat generated from the heating means becomes large enough to set the magnetic spacing dMS to the smaller value efficiently is provided. The head comprises: a substrate having an element-formed surface on which at least one concave portion is formed and an ABS; at least one magnetic head element formed above or on the element-formed surface; at least one thermal expansion layer embedded in the at least one concave portion; and at least one heating means positioned directly above the at least one thermal expansion layer.