Disc Alignment Using Printed Index Marks
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Solution Overview
Problem
Existing methods for aligning disc storage media within a disc drive unit, such as multiple disc write (MDW) techniques, face challenges with orientation, track alignment, eccentricity, and angular misalignment, particularly when using patterned magnetic media, which are not efficiently addressed by conventional laser marking or magnetic index marks.
Innovation Solution
A method involving the creation of printed index marks (PIMs) and template patterns on disc media to align the template relative to the spindle hole center, allowing for concentric track alignment and angular orientation during assembly, using reactive ion etching and mix-and-match lithography to transfer patterns onto the disc substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional laser marking or magnetic index marks are used for alignment, then alignment can be achieved, but the cost increases and the process becomes more complex
Solution Approach 1:
The patent uses printed alignment marks that are copies of standard barcode or data patterns already familiar to the system, rather than requiring specialized laser marking or magnetic index mark technologies. This copying approach achieves precise alignment while avoiding the complexity and cost of specialized alignment systems.
Solution Approach 2:
The alignment marks use universal barcode or data patterns that can be processed by existing read/write heads and control systems already present in the disc drive, eliminating the need for specialized alignment equipment. The same infrastructure used for data reading also handles alignment mark recognition.
2Productivity
If discs are mounted on a different spindle for servo writing, then multiple discs can be written simultaneously, but track eccentricity and angular misalignment occur
Solution Approach 1:
The patent applies preliminary action by pre-calculating and pre-positioning the alignment marks and servo patterns during the MDW process. The alignment marks are placed at specific angular positions that account for the spindle difference, and the system uses these marks to determine the correct angular orientation when mounting discs in the final drive assembly, thereby compensating for the eccentricity introduced by using different spindles.
Solution Approach 2:
The patent replaces mechanical alignment methods (physical indexing features, precision mechanical mounting) with an optical/electronic solution using printed alignment marks that are read by magnetic or optical sensors. This substitution allows the system to achieve precise angular alignment through software-based recognition of printed patterns rather than through mechanical precision.
3Quantity of substance
If discs are tightly stacked to increase storage density, then storage capacity increases, but thermal management and accessibility become more difficult
Solution Approach 1:
The patent applies segmentation by dividing the disc stack into individually addressable units, each with its own unique alignment marks and identification patterns. This allows the system to selectively access and operate on specific discs within the stack without requiring physical manipulation of the entire stack, thereby maintaining ease of operation while achieving high storage density.
Solution Approach 2:
The alignment marks serve as an intermediary between the mechanical disc stack and the electronic control system. These marks enable the control system to identify, locate, and address individual discs within the tightly stacked configuration, facilitating selective accessibility without requiring physical separation or complex mechanical manipulation of the stack.
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 enables precise alignment of disc media within a hard drive unit, reducing disc drive head seek time and maintaining track congruence, even when the disc is eccentrically mounted, without the need for expensive laser marking tools or complex metrology equipment.
Implementation Method 1
detecting the alignment mark and determining a radial direction between the center of the spindle hole and the alignment mark
Implementation Method 2
etching the substrate pattern onto the surface according to the outline
Data Source
AI summary
Processes include aligning a disc with a template at a location so that the pattern from the template is transferred to the disc in a relative orientation. The relative orientation provides that when the disc with the transferred pattern is finally assembled into a hard disc drive, an inner diameter of the spindle hole of the disc may be abutted against an outer diameter of the disc drive spindle, and the data-containing patterns on the discs will be aligned concentrically with a center of the disc drive spindle. While the data-containing patterns are aligned concentrically with the disc drive spindle, the substrate itself is allowed to be non-concentric. Still other aspects include a disc having eccentric formations including PIM and one or more of bit patterns and servo information formed on a disc surface, the eccentricity of the formations is determined based on an expected difference between the radius of the spindle hole of the disc and the radius of the spindle on which the disc will be placed during assembly, with the PIM used to determine the angular alignment of the disc with the spindle.