Media Recovery Mechanism for LWF Stress Test Head Selection
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Solution Overview
Problem
Existing electronic systems face challenges in improving yield and performance due to transient conditions like lubricant waterfall (LWF), which cause write errors and reduce recording performance, especially as storage density increases, leading to high failure probabilities and yield loss.
Innovation Solution
The electronic system incorporates control circuitry to execute a LWF stress test, select the most robust heads for operation, and utilize a media-based cache to mitigate LWF effects, ensuring reliable data writing and reducing failure rates by prioritizing the use of heads with low susceptibility to LWF.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If storage density is increased to meet market demand for higher capacity and cost reduction, then storage capacity improves, but transient conditions like LWF cause more write errors and reduce recording performance
Solution Approach 1:
The system performs a LWF stress test during manufacturing to identify heads with low susceptibility to LWF effects before the product reaches the customer. This preliminary action allows the system to proactively select robust heads for operation, preventing write errors that would occur during normal use.
Solution Approach 2:
The system changes the operational parameters by selecting and using only those heads that pass the LWF stress test criteria. By filtering heads based on their LWF susceptibility characteristics and using only the robust ones, the system maintains high write operation reliability while achieving high storage capacity.
2Reliability
If traditional screening methods are used to identify defective heads, then potentially good products are screened out, but yield is reduced
Solution Approach 1:
Instead of using traditional screening methods that may be overly conservative, the system uses LWF stress test results to identify heads with specific LWF susceptibility characteristics. This allows the system to distinguish between heads that are truly defective and those that are merely sensitive to LWF, retaining potentially good products in the operational pool.
Solution Approach 2:
The system incorporates feedback from LWF stress test results to guide head selection and operational decisions. By using the test data to inform which heads to use and which to reserve or discard, the system optimizes both product quality and manufacturing yield based on actual performance characteristics rather than conservative assumptions.
3Productivity
If all heads are used for operation to maximize productivity, then output increases, but LWF-induced failures occur more frequently
Solution Approach 1:
The system applies local quality by differentiating between heads with different LWF susceptibility characteristics. Instead of treating all heads uniformly, the system identifies and designates specific heads as robust based on their individual stress test performance, allowing selective use of only the most reliable heads for critical operations.
Solution Approach 2:
The system changes the operational state by restricting write operations to only those heads that pass the LWF stress test criteria. This parameter change in head selection strategy maintains high productivity by utilizing multiple heads while simultaneously reducing failure rates by excluding susceptible heads from operation.
Data Source
AI summary
An apparatus includes: a media; a head over the media; and control circuitry, coupled to the heads, configured to: select an operational head from the heads based on margin data collected under a lube waterfall condition, and perform an access to the media with the operational head.