Write Head Side Shield Magnetization Detection
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Solution Overview
Problem
Current data storage devices face challenges with side track erasure (STE) and adjacent track interference (ATI) due to reversed side shield conditions in write heads, which are difficult to detect using existing methods like Magnetic Force Microscopy and footprint techniques, as they are time-consuming and ineffective.
Innovation Solution
A method is developed to measure the reversed side shield condition by supplying a predetermined signal to a write head, performing a recording operation on a data storage medium, and analyzing the resulting magnetization pattern to determine if a reversed side shield condition is present, using techniques such as signal ratio calculations or narrow band filters to quickly and accurately identify the condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional methods like Magnetic Force Microscopy and footprint techniques are used to detect reversed side shield conditions, then measurement precision may be adequate, but productivity is severely reduced due to test times of up to 30 minutes
Solution Approach 1:
The patent replaces complex mechanical measurement systems (Magnetic Force Microscopy) with a simplified electrical measurement system. By applying a predetermined signal to the write head and measuring the resulting magnetization pattern on the storage medium through electrical readback, the system achieves accurate detection of reversed side shield conditions without requiring time-consuming mechanical scanning or complex microscopy equipment.
Solution Approach 2:
The patent changes the measurement parameter from direct magnetic field mapping (which is time-consuming) to signal ratio analysis of readback waveforms. By analyzing the ratio of signals read from different track positions and comparing it to expected values, the system can quickly determine the presence of reversed side shield conditions. This parameter transformation enables fast automated detection while maintaining measurement accuracy.
2Reliability
If traditional detection methods are used, then comprehensive analysis of side shield magnetization may be achieved, but loss of time increases significantly with test durations up to 30 minutes
Solution Approach 1:
The patent performs preliminary actions by pre-calculating expected signal ratios for normal and reversed side shield conditions during system setup. During actual testing, the measured signal ratios are simply compared against these pre-established reference values, eliminating the need for complex real-time analysis. This preliminary preparation enables rapid detection decisions to be made in seconds rather than minutes.
Solution Approach 2:
The patent creates a simplified electrical copy of the magnetic measurement process. Instead of directly measuring and analyzing complex magnetic field distributions, the system reads the magnetization pattern through the read head and analyzes electrical signal characteristics. This copied measurement approach maintains the essential diagnostic information while dramatically reducing measurement time and complexity.
3Productivity
If write heads with reversed side shield conditions are not properly detected, then productivity may be maintained, but object-generated harmful factors increase due to side track erasure and adjacent track interference
Solution Approach 1:
The patent implements a feedback mechanism where the readback signal from the storage medium is analyzed to detect anomalies indicating reversed side shield conditions. The signal ratio comparison provides immediate feedback about the write head's magnetization state, allowing defective heads to be identified and removed from production before they can cause side track erasure or adjacent track interference in actual operation.
Solution Approach 2:
The patent applies preliminary anti-action by detecting and eliminating write heads with reversed side shield conditions before they are installed in hard disc drives. By performing this detection during manufacturing testing, the system prevents the harmful effects of side track erasure and adjacent track interference from occurring in the first place, thereby protecting both productivity and data integrity.
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 allows for fast and accurate detection of reversed side shield conditions, increasing the yield of hard disc drives by effectively screening out affected heads and reducing STE and ATI, with a test time of about 1.5 seconds compared to traditional methods which can take up to 30 minutes.
Implementation Method 1
Current is supplied to write coils to induce a flux path in the main pole to record data on one or more magnetic storage layers of the media
Implementation Method 2
carrying out measurements on a portion of the recorded magnetization pattern influenced by a magnetization of the side shields
Data Source
AI summary
A method that includes supplying a predetermined signal to a write head having side shields. The method also includes performing, by the write head, a recording operation on a surface of a data storage medium, when the predetermined signal is supplied to the write head, to provide a recorded magnetization pattern. The method further includes carrying out measurements on a portion of the recorded magnetization pattern influenced by a magnetization of the side shields. The measurements are employed to determine whether a reversed side shield magnetization condition is present in the write head.