Dual PMR Writer Orientation Assignment for Hard Disk Drive Areal Density
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Solution Overview
Problem
Current PMR write heads face challenges in selecting the better writer before spin stand dynamic performance testing, leading to increased read-write offset and reduced area density capability at outer diameter skew, as the head orientation is predetermined before testing, resulting in suboptimal performance.
Innovation Solution
A dual PMR writer design with a symmetrical or semi-symmetrical air bearing surface, where the better writer is determined during backend testing, and subsequently paired with an appropriate up or down facing suspension to ensure optimal orientation and minimized read-write offset, utilizing separate bucking and driving coils and a dynamic fly height heater scheme to optimize write gap protrusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If head orientation is predetermined before spin stand dynamic performance testing, then manufacturing process is simplified, but read-write offset increases and area density capability decreases at outer diameter skew
Solution Approach 1:
The patent applies preliminary action by determining the better writer through spin stand dynamic performance testing before final head orientation assignment. This reverse sequencing allows the system to identify which writer ( Writer 1 or Writer 2) performs better at OD skew, then assign it to the appropriate head orientation (UP or DN) to minimize RWO, rather than predetermining orientation before testing.
Solution Approach 2:
The patent implements dynamics by making the head orientation assignment flexible and adaptive based on test results. The system can dynamically assign either Writer 1 or Writer 2 to the UP or DN orientation depending on which combination minimizes RWO at OD skew, rather than using a fixed predetermined assignment for all heads.
2Productivity
If head orientation is predetermined before spin stand dynamic performance testing, then production time is reduced, but area density capability deteriorates at outer diameter skew
Solution Approach 1:
The patent performs writer performance evaluation and orientation determination as a preliminary action before final head assembly integration. By completing spin stand testing and determining the optimal orientation assignment before the head is permanently assembled into the drive, the system ensures maximum area density capability without significantly extending overall production time.
3Adaptability or versatility
If symmetrical air bearing surface design is used with dual writers, then flexibility in head orientation assignment is improved, but device complexity increases
Solution Approach 1:
The patent utilizes asymmetry in the dual writer configuration where Writer 1 and Writer 2 are positioned at different locations on the air bearing surface, creating intentional asymmetric writing positions. This asymmetric design, combined with the symmetrical ABS geometry, enables flexible orientation assignment by allowing the system to select which writer (and thus which orientation) provides optimal performance at OD skew.
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 improved flexibility in assigning head orientations post-ABS formation, reducing read-write offset and enhancing area density capability by ensuring the better writer is always positioned closer to the disk center, thereby minimizing track misregistration and improving recording density.
Implementation Method 1
coils that conduct a current and generate a magnetic flux in the main pole such that the magnetic flux exits through the pole tip
Implementation Method 2
dynamic fly height heater scheme to optimize write gap protrusion
Data Source
AI summary
A dual PMR writer is disclosed wherein the better writer at outer diameter (OD) skew is paired with a suspension after dynamic performance (DP) spin stand testing so that the better writer is the inner writer formed closer to a recording disk center than the other writer. Accordingly, lower read write offset is achieved at OD skew and better area density capability is realized. Preferably, there is a symmetrical or substantially symmetrical air bearing surface design after lapping and spin stand testing to afford flexibility in pairing an up facing (UP) head configuration with an UP suspension, or a down facing (DN) head configuration with a DN suspension to enable the better writer to be the inner writer. The dual PMR writer may have a dual dynamic fly height heater on each side of a center plane separating the two writers to improve write gap protrusion in the better writer.