High Contrast Alignment Markers with Shields for HAMR

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Solution Overview

Problem

Conventional passive alignment methods in heat-assisted magnetic recording (HAMR) face challenges in accurately recognizing alignment markers due to interference from background features, particularly with increasing alumina thickness, which affects machine vision recognition and leads to poor alignment accuracy and energy efficiency.

Innovation Solution

The implementation of high contrast alignment markers with shields on the slider, positioned to block interference from optical circuitry and other components, enhancing visibility for machine vision systems to accurately align the laser Chip-On-Submount Assembly (COSA) with the optical waveguide.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional passive alignment methods are used with standard alignment markers, then the alignment process is simple, but the machine vision system cannot accurately recognize the markers due to interference from background features and alumina reflection

Engineering Contradiction:

Improvemarker recognition accuracyVSAvoidalignment marker structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The alignment marker structure is modified locally by adding shields around the marker. These shields have specific optical properties (reflectivity or absorptivity) that differ from the background alumina, creating a local contrast enhancement zone around the marker. This local modification improves marker visibility and recognition accuracy without fundamentally changing the entire alignment system.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention applies optical contrast principles by using shields with different reflectivity or absorptivity characteristics compared to the background alumina. This creates a visual distinction (analogous to color change) between the marker and surrounding features, enabling the machine vision system to accurately identify and locate the alignment marker despite the transparent and reflective nature of the alumina substrate.

Inventive Principle:

Principle #32Color changes

2Strength

If the alumina thickness is increased for better protection, then the structural integrity improves, but the background feature interference increases and reduces marker detection accuracy

Engineering Contradiction:

Improvealumina protectionVSAvoidmarker detection accuracy

Core Design Contradiction:

StrengthVSMeasurement precision

Solution Approach 1:

The shield acts as an intermediary element between the alignment marker and the background alumina features. It blocks or modifies the optical path of reflected light from the alumina, preventing these background features from interfering with marker detection. This intermediary structure allows the system to maintain thick alumina for protection while still achieving accurate marker recognition.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If active alignment method is used to achieve submicron bonding accuracy, then the alignment precision improves, but the process time and complexity increase

Engineering Contradiction:

Improvebonding accuracyVSAvoidalignment process time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The shield structure is pre-configured on the slider before the alignment process. This preliminary preparation creates optimal optical conditions for marker detection, allowing the machine vision system to quickly and accurately locate the alignment marker without requiring time-consuming active alignment procedures. The preliminary structural arrangement enables passive alignment to achieve submicron precision.

Inventive Principle:

Principle #10Preliminary action

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 solution improves alignment accuracy by reducing visual interference, enabling more efficient optical energy coupling and extending laser diode life through precise alignment, thereby enhancing the overall performance and reliability of HAMR systems.

Implementation Method 1

at least one shield arranged with the plurality of alignment marks... blocking interference from optical circuitry and other components

Methodology Applied

Scientific EffectOptical absorption: Absorption (EM radiation)

Implementation Method 2

the light energy from the laser diode chip is guided to an air bearing surface (ABS) through a waveguide to heat up the magnetic media

Methodology Applied

Scientific EffectLight absorption and conversion to heat: Absorption (EM radiation)

Implementation Method 3

Heat from the laser beam lowers the coercivity of the magnetic medium

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS9099145B1High contrast alignment marker

Publication Date: 2015.08.04 WESTERN DIGITAL TECHNOLOGIES INC

AI summary

A slider and method of making same to reduce contrast interference for visual identification of alignment marks on the slider for heat assisted magnetic recording (HAMR) includes a plurality of alignment marks arranged for alignment of a chip on submount assembly (COSA) with respect to the slider, and at least one shield arranged with the plurality of alignment marks. A hard disk drive includes a plurality of alignment marks arranged for alignment of a chip on submount assembly (COSA) with respect to the slider, and at least one shield arranged with the plurality of alignment marks.