Thin-Film Magnetic Head Noise Testing via Periodic Heating
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Solution Overview
Problem
Existing methods for testing thin-film magnetic heads with MR read head elements are inefficient in detecting Barkhausen noise, especially under high-temperature conditions, and can cause irreversible changes to the head, making it difficult to identify defective products in a timely manner.
Innovation Solution
A noise-testing method that alternately applies electrical power at two different levels to the heating unit of the thin-film magnetic head, inducing intermittent heat and stress to simulate high-temperature conditions, allowing for the detection of both normal and special high-temperature noises in a short time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sense current is applied to test the head, then the head can be evaluated for noise, but the test takes a long time under high-temperature conditions and may cause irreversible changes
Solution Approach 1:
The patent applies periodic heating cycles to the head, alternating between heated and non-heated states. This periodic action allows the system to detect both normal high-temperature noises and special noises that occur only during heating, while reducing the total test time compared to continuous heating. The periodic heating also prevents irreversible changes by limiting exposure time at high temperature.
2Measurement precision
If the sense current value is increased to detect noise, then detection sensitivity improves, but irreversible changes occur in the MR effect element
Solution Approach 1:
The patent uses periodic heating with alternating high and low power states to the heating unit. This allows noise detection during both heated and non-heated periods without requiring continuously high sense currents, thereby maintaining detection sensitivity while preventing irreversible damage to the MR effect element.
Solution Approach 2:
The patent changes the temperature parameter periodically by controlling the heating unit's power state. This allows noise detection under varying thermal conditions without requiring high sense currents that would cause damage, achieving both detection sensitivity and head integrity.
3Reliability
If continuous heating is applied to simulate high-temperature conditions, then noise detection is improved, but the test takes too long for practical manufacturing
Solution Approach 1:
The patent implements periodic heating cycles that alternate between heated and non-heated states. This allows the system to detect high-temperature noises during heated periods while reducing overall test time through the non-heated intervals, making the test practical for manufacturing environments.
Solution Approach 2:
The patent skips continuous heating by using intermittent heating cycles. This allows the system to rush through the test process by only heating when necessary for noise detection, rather than maintaining continuous high-temperature conditions, thereby improving manufacturing efficiency.
4Stability of the object's composition
If a heating element is provided to adjust flying height, then flying height stability improves, but thermal asperities and crashes are avoided only by maintaining continuous heat
Solution Approach 1:
The patent uses periodic heating cycles for the flying height adjustment element. This maintains flying height stability through controlled thermal expansion during heated periods while allowing cooling during non-heated periods, preventing excessive temperature accumulation that could cause thermal asperities or crashes.
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 method enables quick and accurate evaluation of thin-film magnetic heads for noise defects by measuring noise outputs during alternating power applications, improving manufacturing efficiency and reducing the risk of irreversible changes to the MR read head elements.
Implementation Method 1
a heating unit capable of applying a heat and a stress to the MR read head element
Implementation Method 2
increase of deformation by the thermal expansion associated with an increase in the temperature of the element
Implementation Method 3
The Barkhausen noise is generated primarily because a magnetic domain wall is caught in defects in the magnetic film constituting the MR read head element as the magnetic domain wall moves
Implementation Method 4
thin-film magnetic heads with MR read head elements
Implementation Method 5
the end of the head element is caused to be protruded in the direction of the magnetic disk by the heat generated by the heating element
Data Source
AI summary
A noise-testing method for a thin-film magnetic head with an MR read head element and a heating unit capable of applying a heat and a stress to the MR read head element, includes a step of applying alternately and discontinuously with each other an electrical power having a first level and an electrical power having a second level higher than the first level to the heating unit, and a step of evaluating the thin-film magnetic head by measuring a noise output or noise outputs obtained from the MR read head element when the electrical power or the electrical powers are applied to the heating unit.