Slider Lapping via Bias Current Thermal Expansion
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Solution Overview
Problem
The existing methods for lapping sliders in hard disc drives face challenges in accurately and efficiently removing material, particularly during the transition from rough to fine lapping stages, where transducer devices may be at different distances from their target values, and there is a need for precise control of heat generation to expand and remove these devices effectively.
Innovation Solution
A method and system that apply positive-bias and negative-bias currents to heater devices in sliders to generate heat, allowing for controlled expansion and precise material removal during the lapping process, utilizing a lapping system with a rotating lapping plate and a controller to manage electrical power distribution and prevent excessive current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lapping methods are used without electrical power application, then the lapping process is simpler, but material removal accuracy and efficiency are insufficient
Solution Approach 1:
The patent applies electrical parameters (positive-bias and negative-bias currents) to the heater devices during lapping, changing the physical state of the transducer devices through thermal expansion. This enables precise control of material removal by adjusting current magnitude and duration, directly improving manufacturing precision while accepting increased system complexity
Solution Approach 2:
The patent replaces purely mechanical lapping with a combined thermal-mechanical process. Electrical current is applied to heater devices to generate heat, causing thermal expansion of transducer devices, which are then removed by the lapping plate. This substitution of mechanical-only removal with thermally-assisted removal improves precision and efficiency
2Productivity
If heat is applied to expand transducer devices for material removal, then lapping efficiency improves, but excessive heat may damage surrounding structures
Solution Approach 1:
The patent applies heat locally to specific transducer devices through individually addressable heater devices. By applying positive-bias or negative-bias current selectively to specific sliders, thermal energy is concentrated only where material removal is needed, improving lapping efficiency while preventing thermal damage to surrounding structures through localized heating
Solution Approach 2:
The patent uses controlled, periodic application of electrical current to heater devices during the lapping process. Current is applied in controlled pulses or cycles, generating heat only when needed for thermal expansion and material removal, then paused to allow cooling, thereby improving productivity while preventing excessive heat accumulation and thermal damage
3Productivity
If multiple sliders are lapped simultaneously in a row bar, then production throughput increases, but current distribution control becomes more difficult
Solution Approach 1:
The patent segments the row bar into individually addressable sliders, each with its own heater device and contact pads. This segmentation allows independent electrical connection and current control for each slider, enabling precise current distribution control across multiple sliders lapped simultaneously, thereby maintaining measurement precision while achieving high production throughput
Solution Approach 2:
The patent introduces electrically conductive portions and contact pads as intermediaries between the power source and heater devices in each slider. These intermediaries facilitate controlled current distribution by providing dedicated electrical pathways, enabling precise current management for multiple sliders lapped simultaneously while maintaining individual control over each device's heating
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 and efficient material removal, ensuring that transducer devices are accurately lapped to their target values, improving the accuracy and reliability of write pole width in perpendicular magnetoresistive heads and break point control in head-assisted magnetoresistive heads, thereby enhancing areal density and reliability.
Implementation Method 1
a positive-bias current is applied to the first heater device to generate heat and a negative-bias current is applied to the second heater device to generate heat
Implementation Method 2
generate heat, allowing for controlled expansion and precise material removal during the lapping process
Data Source
AI summary
The present disclosure includes methods and systems for lapping a row bar of sliders. According to the present disclosure, an electrical interconnect configuration is provided that permits the net current provided to a row bar to heat electrical heating devices during lapping to be managed so as help prevent exceeding breakdown currents of related electrical channels.