Silver Alloy Electrical Lapping Guides for Disk Drive Slider Fabrication
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Solution Overview
Problem
Conventional electrical lapping guides (ELGs) in magnetic recording disk drives have unpredictable electrical resistance due to tapered back edges, which are formed simultaneously with magnetoresistive read sensors, and require a higher etch rate to achieve a non-tapered flat edge while maintaining a sheet resistance matching the lapping tool's capability.
Innovation Solution
Forming the ELG from a different material, such as an alloy comprising silver (Ag) and tin (Sn) with a higher etch rate and electrical resistivity, allowing for a sharp, well-defined non-tapered back edge and stable resistance measurement during the lapping process, while maintaining a film thickness similar to the MR sensor stack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the ELG is formed from the same materials as the MR sensor, then the manufacturing process is simplified, but the ELG back edge becomes tapered resulting in unpredictable electrical resistance
Solution Approach 1:
The patent changes the material composition of the ELG from matching the MR sensor stack to using a distinct material (such as tungsten, molybdenum, or tungsten silicide) with different etching characteristics. This parameter change in material composition enables the ELG to maintain a flat back edge during lapping while still being formed in the same manufacturing process, thereby resolving the contradiction between manufacturing simplicity and resistance predictability.
2Measurement precision
If the ELG film is made thinner to achieve a flat back edge, then the electrical resistance becomes predictable, but the sheet resistance no longer matches the lapping equipment requirements
Solution Approach 1:
The patent changes the material parameter of the ELG to achieve a higher etch rate relative to the MR sensor stack. This allows the ELG to be etched completely through to form a flat back edge while maintaining an appropriate film thickness for the desired sheet resistance, thus simultaneously achieving both predictable resistance and proper sheet resistance matching.
Solution Approach 2:
The patent employs composite material selection where the ELG is made from a material distinct from the MR sensor stack materials. This composite approach allows independent optimization of etching properties for flat back edge formation while maintaining electrical properties for proper sheet resistance, resolving the contradiction between resistance predictability and sheet resistance matching.
3Ease of manufacture
If the ELG has the same etch rate as the MR sensor stack, then both are etched simultaneously, but the ELG back edge becomes tapered and surface area becomes unpredictable
Solution Approach 1:
The patent changes the etch rate parameter of the ELG material to be higher than that of the MR sensor stack. This differential etch rate allows both structures to be etched simultaneously in the same process step while ensuring the ELG is completely removed to form a flat back edge, thereby maintaining manufacturing simplicity while achieving precise back edge geometry.
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
The high etch rate and resistivity of the AgSn alloy ensure a predictable electrical resistance and prevent corrosion, enabling precise control of the stripe height of the MR sensor with a stable resistance measurement and a non-tapered ELG back edge, enhancing the manufacturing process.
Implementation Method 1
the ELG material has a substantially higher rate of etching than the material of the MR sensor
Implementation Method 2
a high corrosion resistance, which prevents corrosion during the wet lapping process
Data Source
AI summary
An air-bearing slider used in a magnetic recording disk drive has a surface that supports a magnetoresistive (MR) read head or sensor and an electrical lapping guide (ELG) adjacent to the MR sensor. The ELG is formed of a different material than the MR sensor so as to have both a high electrical resistivity and a substantially higher etch rate. When the ELG and MR sensor are etched simultaneously to form their respective back edges, the ELG will have a sharp well-defined non-tapered wall at the back edge. The ELG has a film thickness close to but generally thinner than that of the MR sensor, and a sheet resistance to generally match the resistance measurement capability of the lapping tool. The preferred material for the ELG is an alloy comprising silver (Ag) and one or more of Sn, Ge and zinc Zn.