Magnetic Head Coil Adjacent Layer Thermal Expansion Suppression
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Solution Overview
Problem
The challenge in magnetic disk drives is to reduce the flying height of sliders while preventing damage from collisions and heat-induced protrusion of the medium facing surface, which is exacerbated by the high thermal expansion coefficient of resist materials used in coil insulating layers, leading to increased heat generation and difficulty in heat dissipation.
Innovation Solution
A magnetic head with a coil adjacent layer made of a nonmagnetic material having a low linear thermal expansion coefficient and high thermal conductivity, such as SiC, W, or AlN, is used to suppress heat-induced expansion and enhance heat dissipation, allowing the coil adjacent layer to directly contact or be insulated from the coil sides, thereby reducing protrusion and improving flying height stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If resist material is used as coil insulating layer, then ease of manufacture is improved, but thermal expansion causes protrusion of medium facing surface
Solution Approach 1:
The patent changes the material parameter of the coil insulating layer from resist (high thermal expansion coefficient) to low thermal expansion coefficient material (such as alumina or its composite). This parameter change directly addresses the protrusion problem by reducing thermal expansion-induced deformation while maintaining ease of manufacture through established ceramic processing techniques.
Solution Approach 2:
The patent employs composite materials, specifically alumina-based composites or combinations of low thermal expansion materials with other ceramics, to achieve both low thermal expansion properties and manufacturability. These composite materials provide the necessary mechanical strength and thermal stability while allowing for practical fabrication processes.
2Manufacturing precision
If SiO2, Si nitride or Si oxide is used as coil insulating layer, then protrusion is suppressed, but heat dissipation becomes difficult
Solution Approach 1:
The patent changes the thermal conductivity parameter of the coil insulating layer by selecting materials with high thermal conductivity (alumina with 30-40 W/mK or diamond-like carbon with 700-2000 W/mK). This parameter change simultaneously achieves protrusion suppression through low thermal expansion and improves heat dissipation capability, resolving the contradiction between dimensional stability and thermal management.
3Productivity
If flying height is reduced to improve recording density, then recording density is improved, but collision damage risk increases
Solution Approach 1:
The patent changes the thermal and mechanical parameters of the coil insulating layer material to reduce thermal expansion and improve dimensional stability. This allows the medium facing surface to maintain its designed geometry even at reduced flying heights, preventing collision damage while enabling higher recording densities through closer spacing to the recording medium.
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 solution effectively suppresses heat-induced protrusion and enhances heat dissipation, allowing for reduced flying heights and improved recording density and signal-to-noise ratios by using materials with low thermal expansion and high conductivity, specifically SiC, W, or AlN, in the coil adjacent layer.
Implementation Method 1
having a thermal conductivity of 40 W/m·K or higher at a temperature of 25° C.
Implementation Method 2
having a linear thermal expansion coefficient of 5×10−6/° C. or smaller at a temperature of 25° C. to 100° C.
Data Source
AI summary
A magnetic head includes a coil, a pole layer, and a coil adjacent layer. The coil includes a winding portion having two side surfaces. The coil adjacent layer is adjacent to at least part of the whole of the two side surfaces of the winding portion. The coil adjacent layer is formed of a nonmagnetic material having a linear thermal expansion coefficient of 5×10−6/° C. or smaller at a temperature of 25° C. to 100° C. and having a thermal conductivity of 40 W/m·K or higher at a temperature of 25° C.