Embedded Contact Sensor for HDD Head-Disk Detection
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Solution Overview
Problem
Conventional manufacturing touch down detection methods in hard disk drives (HDDs) are prone to errors due to contamination, making it difficult to differentiate between true and pseudo contact between the head slider and the magnetic disk, which can lead to unintended contact and reduced recording performance.
Innovation Solution
The implementation of an embedded contact sensor (ECS) in conjunction with thermal fly height control (TFC) to enhance contact detection sensitivity, allowing for the differentiation between true and pseudo contact by monitoring resistance changes caused by head-disk contact, and the use of burnishing to remove contaminants and achieve accurate touch down detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional manufacturing touch down detection methods are used, then the detection process is simple, but the detection accuracy is low due to contamination causing pseudo contact
Solution Approach 1:
The detection system is segmented into multiple independent sensors: a first sensor (capacitive or inductive) for initial contact detection and a second sensor (embedded contact sensor) for verification. This segmentation allows the system to differentiate between true contact and pseudo contact caused by contamination, resolving the contradiction between simple detection and high accuracy.
Solution Approach 2:
An embedded contact sensor (ECS) is introduced as an intermediary element between the head slider and the magnetic disk. The ECS provides direct mechanical contact detection at the air bearing surface, serving as a mediator that accurately distinguishes true contact from contamination-induced pseudo contact, thereby improving detection accuracy without requiring complex external measurement systems.
2Reliability
If power to TFC is gradually increased for touch down detection, then the calibration procedure can be performed, but contamination can skew the results leading to unintended contact
Solution Approach 1:
The system performs preliminary contact detection using the first sensor before committing to the touch down power setting. This preliminary action allows the system to identify and reject pseudo contact events caused by contamination, ensuring that only true contact results in calibrated power settings, thereby improving reliability while eliminating contamination effects.
Solution Approach 2:
The system uses feedback from multiple sensors to verify contact detection. The first sensor provides initial feedback, and the second embedded contact sensor provides verification feedback. Only when both sensors confirm contact does the system finalize the touch down detection, creating a feedback mechanism that filters out contamination-induced false positives and ensures reliable detection.
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
The ECS provides higher contact sensitivity and accuracy in detecting true contact, reducing the risk of pseudo contact and ensuring reliable recording performance by effectively differentiating between true and pseudo contact and facilitating the removal of contaminants through burnishing.
Implementation Method 1
monitoring resistance changes caused by head-disk contact
Implementation Method 2
A thermal fly height control (TFC) disposed in a head slider adjusts the clearance by using the heater to heat the head element
Data Source
AI summary
A HDD including a magnetic disk, a magnetic head, an embedded contact sensor embedded in the magnetic head and configured to detect a contact between the magnetic disk and the magnetic head, and TFC embedded in the magnetic head and configured to facilitate in detecting the contact between the magnetic disk and said magnetic head.