Multi-stage lapping of HDD sliders with selective heating

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

During the lapping process of sliders for hard disc drives, unintended expansion of transducer devices due to heating causes material removal from both intended and surrounding devices, leading to inaccuracies and potential damage to sensitive reader devices, which are not meant to be exposed to heat during read operations.

Innovation Solution

A multi-stage lapping process is employed where the transducer devices are selectively heated to expand and then cooled, allowing for precise control of material removal, with the first stage involving heating to expand the writer device and the second stage occurring without heat to ensure the reader device remains close to the air bearing surface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If heating is applied to expand transducer devices during lapping, then the writer device can be accurately planarized, but the reader device undergoes unintended expansion causing material removal and potential damage

Engineering Contradiction:

Improveplanarization accuracy of writer deviceVSAvoidheat exposure to reader device

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The lapping process is divided into multiple stages: a first lapping stage with heating applied selectively to the writer device, and a second lapping stage without heating. This segmentation allows the writer to receive heat treatment for accurate planarization while the reader is protected from harmful thermal effects during the second stage.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The writer device is pre-expanded through heating before the final lapping operation. By performing the thermal expansion action beforehand, the writer achieves the desired dimensional state for precise planarization, while subsequent cooling and unprotected lapping stages allow the reader to return to its original dimensions without heat-induced expansion.

Inventive Principle:

Principle #10Preliminary action

2Quantity of substance

If uniform heating is applied to the transducer region, then both writer and reader devices expand, but this causes material removal from the reader device which should remain close to the air bearing surface

Engineering Contradiction:

Improvematerial removal controlVSAvoidreader device position relative to air bearing surface

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

Heating is applied locally and selectively to the writer device rather than uniformly to the entire transducer region. This localized thermal treatment ensures that only the writer device undergoes expansion and subsequent material removal, while the reader device maintains its original dimensions and position relative to the air bearing surface.

Inventive Principle:

Principle #3Local quality

3Stability of the object's composition

If heating is applied during the entire lapping process, then consistent expansion is achieved, but the reader device recedes excessively after cooling

Engineering Contradiction:

Improvedimensional stability of transducer devicesVSAvoidfinal position accuracy of reader device

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The heating process is applied periodically rather than continuously - specifically during the first lapping stage and then discontinued before the second lapping stage. This periodic thermal action allows the writer device to maintain stable expansion during its lapping operation, while the reader device is allowed to cool and return to its original dimensions, preventing excessive recession after cooling.

Inventive Principle:

Principle #19Periodic 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 method mitigates the 'penalty' of unintended device expansion, allowing for accurate planarization and reducing exposure of sensitive reader devices to heat, thereby improving the precision and reliability of slider manufacturing.

Implementation Method 1

applying a current to the one or more heat-generating devices in the transducer region to generate heat

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

heating the transducer region to cause at least the first transducer device and the second transducer device to expand in the lapping direction toward a lapping plate

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS11331765B1Methods of lapping a substrate while heating at least a portion of the substrate, and related substrates and systems

Publication Date: 2022.05.17 SEAGATE TECH LLC

AI summary

The present disclosure includes methods and systems that include multiple lapping stages having at least one lapping stage that laps while a heat source is applied to cause expansion during lapping and at least one subsequent lapping stage that laps while the heat source is reduced (e.g., turned off).