Thin-Film Magnetic Head Coil-Insulating Layer Thermal Expansion Control
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Solution Overview
Problem
Existing thin-film magnetic heads face challenges in suppressing the thermal pole tip protrusion (TPTP) phenomenon due to environmental temperature, leading to potential thermal asperity and crush issues, as current solutions either require new components or insufficiently regulate heat expansion coefficients and Young's modulus.
Innovation Solution
A thin-film magnetic head design with a coil-insulating layer having a width of at least 46 μm and a length of at least 75 μm, a heat expansion coefficient of 30×10−6/K or higher, and a Young's modulus between 1 GPa and 4 GPa, which effectively absorbs heat and prevents protrusion of the magnetic head element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the effective distance dM is reduced to 10 nm or less to increase recording density, then writing and reading performance is improved, but the magnetic head element is more susceptible to thermal pole tip protrusion and contact with the magnetic disk surface
Solution Approach 1:
The patent changes the material parameters of the coil-insulating layer by specifying a heat expansion coefficient of 30×10−6/K or higher and a Young's modulus of 1 GPa to 4 GPa. These parameter changes enable the insulating layer to compensate for thermal expansion differences, suppressing thermal pole tip protrusion while maintaining the reduced effective distance dM for high recording density
Solution Approach 2:
The patent uses a composite structure combining the coil-insulating layer with specific material properties (heat expansion coefficient ≥30×10−6/K, Young's modulus 1-4 GPa) and the overcoat layer. This composite material approach allows the system to achieve both high recording density through reduced dM and thermal stability through coordinated thermal expansion characteristics
2Reliability
If the heat expansion coefficient difference between the magnetic head element and overcoat layer is large, then thermal pole tip protrusion is suppressed, but the magnetic head element may contact the magnetic disk surface causing thermal asperity
Solution Approach 1:
The patent precisely controls the heat expansion coefficient parameter of the coil-insulating layer to be 30×10−6/K or higher, and the Young's modulus to be 1 GPa to 4 GPa. These parameter specifications enable the insulating layer to provide appropriate thermal expansion compensation without excessive protrusion, preventing thermal asperity while maintaining thermal stability
Solution Approach 2:
The patent exploits thermal expansion effects by selecting materials with specific heat expansion coefficients. The coil-insulating layer with heat expansion coefficient ≥30×10−6/K expands thermally to compensate for the thermal contraction of the magnetic head element, suppressing thermal pole tip protrusion to a level that prevents contact with the magnetic disk surface
3Reliability
If a heating element is added to actively control the effective distance dM, then writing and reading performance is maintained, but the device complexity increases and environment temperature control becomes difficult
Solution Approach 1:
The patent extracts the thermal expansion compensation function from the magnetic head element itself and assigns it to the coil-insulating layer. By specifying the heat expansion coefficient and Young's modulus of the insulating layer, the system passively compensates for thermal effects without requiring active heating elements, thereby reducing device complexity while maintaining effective distance control
Solution Approach 2:
The coil-insulating layer performs self-compensation for thermal effects through its specifically selected material properties (heat expansion coefficient ≥30×10−6/K, Young's modulus 1-4 GPa). The layer automatically adjusts to temperature changes through its thermal expansion characteristics, eliminating the need for external heating elements or active control systems
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 design ensures the TPTP phenomenon is reliably suppressed without using new components, maintaining low flying height and preventing thermal asperity and crush, even with a heating portion present.
Implementation Method 1
a heat expansion coefficient of the coil-insulating layer being larger than or equal to 30×10−6/K
Implementation Method 2
an electromagnetic coil element for writing data with a coil layer which generates magnetic field by current flowed in its own
Implementation Method 3
a temperature of the magnetic head element increases by Joule heat, eddy current loss heat, and so on
Data Source
AI summary
A thin-film magnetic head which suppresses the TPTP phenomenon due to the environment temperature is provided. The thin-film magnetic head includes, an electromagnetic coil element having a coil layer and coil-insulating layer, and an overcoat layer. A width of the coil-insulating layer in a track-width direction is larger than a width that is needed to insulate the whole coil layer, and is at least 46 μm, and a length of the coil-insulating layer in a direction perpendicular to the track-width direction is larger than a length that is needed to insulate the whole coil layer, and is at least 75 μm. In addition, a heat expansion coefficient of the coil-insulating layer is larger than or equal to 30×10−6/K, and a Young's modulus of the coil-insulating layer is larger than or equal to 1 GPa and smaller than or equal to 4 GPa.