Electronic Lapping Guides for Sensor Array Stripe Height Control
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Solution Overview
Problem
Conventional magnetic recording transducers face challenges in achieving high recording densities and performance across various skew angles, particularly in two-dimensional magnetic recording (TDMR) technology, due to issues with sensor alignment and fabrication complexity.
Innovation Solution
The use of multiple read sensors with electronic lapping guides (ELGs) to control the stripe heights of the sensors, allowing for precise lapping and alignment, thereby improving the performance and yield of the magnetic recording read transducer by optimizing sensor responses across different skew angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple read sensors are used for TDMR to achieve higher recording densities, then recording density is improved, but sensor alignment precision and fabrication complexity become problematic
Solution Approach 1:
The patent applies preliminary action by forming electronic lapping guides (ELGs) alongside the sensor arrays before the lapping process. These ELGs serve as reference structures that define the precise lapping plane and stripe height targets. By establishing these guides in advance, the system ensures that subsequent lapping operations achieve the required alignment precision for multiple sensors without requiring post-fabrication adjustments.
Solution Approach 2:
The patent implements feedback through the use of ELGs that provide real-time reference during the lapping process. The ELGs are measured to determine actual stripe heights, and this measurement feedback is used to control and adjust the lapping operation to achieve target stripe heights. This closed-loop control ensures precise alignment of multiple sensors even as material is removed during lapping.
2Ease of manufacture
If conventional lapping methods are used for multiple sensor arrays, then fabrication simplicity is maintained, but stripe height control precision deteriorates
Solution Approach 1:
The patent introduces electronic lapping guides (ELGs) as intermediary structures that mediate between the simple lapping process and the precision requirements. The ELGs act as reference standards that translate the straightforward mechanical lapping operation into a precision-controlled process. By measuring the ELGs and using them to control the lapping depth, the system achieves high stripe height control precision while maintaining relative fabrication simplicity.
Solution Approach 2:
The patent replaces purely mechanical lapping control with an electrical/electronic measurement and control system. Instead of relying solely on mechanical fixtures and manual control, the system uses electrical resistance measurements of the ELGs to precisely determine stripe heights and control the lapping process. This substitution of mechanical control with electrical measurement enables higher precision.
3Reliability
If sensors are aligned for zero skew angle, then performance at zero skew is optimized, but performance across all skew angles deteriorates
Solution Approach 1:
The patent applies local quality by creating controlled variations in the sensor array configuration to address different operating conditions. Specifically, the sensor array includes sensors at different longitudinal positions and with different stripe height offsets. This local differentiation allows the array to maintain optimal performance across various skew angles, as sensors at different positions can compensate for skew-induced misalignment.
Solution Approach 2:
The patent introduces an additional dimension of control by varying stripe heights in the vertical dimension, not just in the longitudinal position. By deliberately offsetting stripe heights of different sensors, the system creates a three-dimensional sensor configuration that can accommodate skew angles. This dimensional approach allows the sensor array to maintain performance across a range of skew conditions rather than being optimized for a single angle.
Data Source
AI summary
A method and system provide a storage device. A plurality of read sensor stacks for each reader of the storage device are provided. The read sensor stacks are distributed along a down track direction and offset in a cross-track direction. A plurality of electronic lapping guides (ELGs) are provided for the read sensor stacks. The read sensor stacks are lapped. Lapping is terminated based on signal(s) from the ELG(s).