Multi Reader Head With Varying Gap Layer For Noise Reduction
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Solution Overview
Problem
In multi reader heads of hard disk drives, there is a trade-off between reducing Reader-Reader Separation (RRS) to enhance reading accuracy and increasing the distance between shields to minimize capacitance, which affects high-frequency noise generation, and existing methods like changing the insulating layer material from aluminum oxide to silicon oxide are insufficient in reducing capacitance effectively.
Innovation Solution
The multi reader head design features a gap layer with varying distances between shields, where portions with greater distances are farther from the center on the air bearing surface and shields are bent or curved away from each other, maintaining minimal RRS while reducing capacitance by using materials with low permittivity like silicon oxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the distance between shields is reduced to minimize RRS, then reading accuracy is improved, but capacitance between shields increases causing high-frequency noise
Solution Approach 1:
The gap layer is designed with spatially varying thickness: thinner regions positioned near the center of the air bearing surface to minimize RRS and improve reading accuracy, and thicker regions positioned toward the edges to reduce capacitance and suppress high-frequency noise. This local differentiation allows simultaneous optimization of both reading precision and noise reduction.
Solution Approach 2:
The solution transitions from controlling only the lateral separation between readers to incorporating the vertical dimension through variable gap layer thickness. By modulating the thickness of the gap layer in the vertical dimension, the patent achieves capacitance reduction without compromising the lateral positioning required for accurate reading.
2Object-generated harmful factors
If the distance between shields is increased to reduce capacitance, then high-frequency noise is reduced, but reading accuracy deteriorates
Solution Approach 1:
The gap layer thickness is locally optimized: thicker regions are positioned where capacitance reduction is critical for noise suppression, while thinner regions are positioned where minimal RRS is critical for reading accuracy. This spatially differentiated design allows the system to achieve both low capacitance and high reading precision simultaneously.
3Object-generated harmful factors
If insulating layer material is changed from aluminum oxide to silicon oxide, then capacitance is reduced, but the reduction is insufficient
Solution Approach 1:
The patent changes the physical parameter of the gap layer (thickness) in addition to material selection. By varying the thickness parameter spatially, the design achieves superior capacitance reduction compared to material substitution alone, while maintaining electrical insulation properties.
Solution Approach 2:
The gap layer is formed as a composite structure combining silicon oxide material with spatially varying thickness characteristics. This composite approach—integrating material selection with geometric configuration—achieves more effective capacitance reduction than material substitution alone.
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 effectively reduces high-frequency noise and maintains high reading accuracy by minimizing capacitance between shields while keeping RRS small, addressing the limitations of previous technologies.
Implementation Method 1
The reader includes a magneto-resistive effect element (MR element), such as a tunnel magneto-resistance effect (TMR) element
Implementation Method 2
The reader includes a magneto-resistive effect element (MR element), such as a tunnel magneto-resistance effect (TMR) element or a giant magneto-resistance effect (GMR) element
Implementation Method 3
it is preferable to reduce capacitance between each shield of the readers as much as possible
Implementation Method 4
using materials with low permittivity like silicon oxide
Data Source
AI summary
A multi reader head has a plurality of readers that are laminated via a gap layer(s), and each of the readers has a structure in which a current-perpendicular-to-plane (CPP) type of magneto-resistive effect element, where a current flows along the lamination direction, is interposed between a pair of shields that function as an electrode, respectively, from both sides in the lamination direction. The shields that are opposed from each other via the gap layer of the readers that are adjacent in the lamination direction by a distance that is not constant, but include a portion with a greater distance between the shields and another portion with a smaller distance between the shields are included. The portion with a greater distance between the shields is situated at a position away from the center on an air bearing surface opposing to a recording medium in the magneto-resistive effect element.