Magnetic Head Sensor Corrosion Protection via Bias Current Heating
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Solution Overview
Problem
Magnetic heads in tape drives face issues with corrosion and oxidation, leading to increased Wallace spacing losses and reduced magnetic performance, especially at higher data densities, due to the propensity of AMR, GMR, and TMR sensors for corrosion and the limitations of existing protective coatings.
Innovation Solution
The method involves reducing relative humidity around the magnetic head by passing an elevated bias current through the sensor when not in use, or setting potentials to prevent corrosion, and applying organic coatings to protect the head from oxidation and corrosive materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hard protective coatings (e.g., alumina) are applied to the sensor, then corrosion resistance is improved, but the coating wears away due to contact with the tape, leaving the sensor unprotected
Solution Approach 1:
The patent introduces an intermediary substance (organic coating or lubricant) that mediates between the sensor and the tape. This coating provides corrosion protection while reducing direct mechanical contact and wear, allowing the sensor to remain protected without the coating degrading from friction with the tape surface
2Reliability
If the sensor is recessed to protect it from corrosion, then corrosion resistance is improved, but Wallace spacing signal losses increase
Solution Approach 1:
Instead of recessing the sensor (which creates spacing losses), the patent uses an intermediary protective coating that allows the sensor to remain at its optimal position. The coating acts as a barrier against corrosion while maintaining the sensor's close proximity to the tape, thus preserving signal amplitude
3Reliability
If organic coatings are applied to protect the head from oxidation, then corrosion resistance is improved, but the coating may be removed during operation
Solution Approach 1:
The patent employs a self-service protection mechanism where the tape itself applies the protective organic coating to the sensor during normal operation. The coating is applied continuously as the tape passes over the sensor, and can be removed by a cleaning portion of the tape, providing ongoing protection without requiring separate application processes
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 effectively reduces corrosion and maintains signal integrity by controlling humidity and applying protective coatings, thereby minimizing Wallace spacing losses and ensuring consistent magnetic performance across varying data densities.
Implementation Method 1
passing an elevated bias current through a sensor of the head during at least some time periods when the sensor is not in use for reading data, the elevated bias current being chosen to be sufficient to heat the sensor to a level which will reduce the local relative humidity to below a threshold level for reducing or eliminating corrosion of the sensor
Implementation Method 2
applying organic coatings to protect the head from oxidation and corrosive materials
Data Source
AI summary
A method for protecting a magnetic head according to one embodiment includes reducing a relative humidity in a vicinity of a magnetic head by passing an elevated bias current through a sensor of the head during at least some time periods when the sensor is not in use for reading data, the elevated bias current being chosen to be sufficient to heat the sensor to a level which will reduce the local relative humidity to below a threshold level for reducing or eliminating corrosion of the sensor. Additional methods are also presented.