Perpendicular Magnetic Recording Head Throat Height Definition
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Solution Overview
Problem
The existing methods for defining the throat height in perpendicular magnetic recording heads face issues with dimensional accuracy and reliability due to thermal expansion of organic resist materials and adhesion problems with plating foundation layers, leading to magnetic saturation and decreased recording performance.
Innovation Solution
A nonmagnetic metal plating layer is used to form a throat height determining layer with a return yoke reinforcement layer made of a magnetic material having a higher saturated magnetic flux density, which extends from the front end face of the throat height determining layer to its upper face, preventing magnetic saturation and improving dimensional accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a positioning layer made of organic resist material is used to define throat height, then the throat height can be positioned at a retracted location, but the positioning layer thermally expands during operation causing deformation and peeling defects
Solution Approach 1:
The patent changes the material parameter of the positioning layer from organic resist material to inorganic nonmagnetic insulating material, which has a coefficient of thermal expansion matching the surrounding structures. This parameter change eliminates thermal expansion mismatch, preventing deformation and peeling while maintaining positioning accuracy.
Solution Approach 2:
The patent uses a sacrificial organic resist layer that is intentionally designed to be removed after serving its positioning function. This disposable layer enables precise throat height definition during manufacturing, then is eliminated to avoid thermal expansion problems during operation.
2Strength
If heat treatment is performed to enhance adhesion of the positioning layer, then adhesion is improved, but the end parts of the positioning layer become rounded reducing dimensional accuracy
Solution Approach 1:
The sacrificial organic resist layer is designed to be removed after positioning, so adhesion enhancement through heat treatment is unnecessary. This eliminates the rounding problem while still allowing temporary adhesion during manufacturing processes.
Solution Approach 2:
The patent extracts the positioning function to a separate sacrificial layer that can be easily removed. This separation allows the final structure to use materials and processes optimized for their specific functions without compromise.
3Manufacturing precision
If plating is used to form the return yoke layer with desirable throat height, then the throat height can be defined by plating control, but the plating foundation layer may adhere to the return yoke layer during removal causing dimensional inaccuracy
Solution Approach 1:
The patent extracts the positioning function to a separate sacrificial organic resist layer rather than using the plating foundation layer for positioning. This separation prevents the adhesion problem during removal while maintaining plating control for throat height definition.
Solution Approach 2:
The sacrificial organic resist layer serves as a temporary positioning structure that is removed after defining the throat height. This disposable element eliminates the need to compromise plating foundation layer adhesion properties.
4Productivity
If the throat height is defined very short (100-200 nm) to improve recording performance, then magnetic saturation may occur in the front end part of the return yoke layer
Solution Approach 1:
The patent applies different material properties to different regions: the return yoke layer uses material with high saturated magnetic flux density specifically in the front end region where magnetic flux concentration is highest. This local optimization prevents magnetic saturation while maintaining short throat height for recording performance.
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 the dimensional accuracy of the throat height, prevents deformation and chipping of the return yoke layer, and improves recording performance by maintaining the perpendicularity of the front end face and preventing magnetic saturation.
Implementation Method 1
the coefficient of thermal expansion of the positioning layer is much higher than that of the return yoke layer and nonmagnetic insulating material positioned thereabout, so that the positioning layer thermally expands when the head operates, thereby deforming the end face in the height direction
Implementation Method 2
magnetic saturation may occur in the front end part of the return yoke layer exposed at the medium-opposing surface when the head operates, thereby deteriorating recording performances
Data Source
AI summary
In a perpendicular magnetic recording head comprising a main magnetic pole layer and a return yoke layer which are laminated with a magnetic gap layer interposed therebetween, a nonmagnetic throat height determining layer and a return yoke reinforcement layer made of a magnetic material having a saturated magnetic flux density higher than that of the return yoke layer are provided on the magnetic gap layer. The nonmagnetic throat height determining layer has a front end face parallel to the medium-opposing surface at a position retracted by a desirable throat height from the medium-opposing surface. The return yoke reinforcement layer is formed directly under the return yoke layer so as to extend at least from the front end face of the nonmagnetic throat height determining layer to the upper face thereof, and is exposed at the medium-opposing surface between the magnetic gap layer and return yoke layer.