Bleed Resistor Shunt Structure for Read Sensor Probing
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Solution Overview
Problem
The existing methods for determining the stripe height of a magnetoresistive read sensor using electronic lapping guides are unreliable due to noise interference and require expensive, high-cost probe connections, which are impractical for smaller devices.
Innovation Solution
A bleed resistor network with two resistors in parallel and one resistor in series is used, allowing for accurate measurement of the stripe height through the resistance of an electronic lapping guide, which is electrically coupled to a substrate and bonding pad, enabling precise control of the lapping process without occupying excessive physical space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the read transducer's shunt resistance is increased to prevent probing errors, then measurement reliability improves, but the resistor shunt layout occupies an extremely large portion of the slider area
Solution Approach 1:
The shunt resistance function is segmented into two parts: a first shunt resistor (R1) connected to the read pad and a second shunt resistor (R2) connected to the ELG pad. This segmentation allows each resistor to be smaller individually while maintaining the required shunt resistance ratio (R2/R1 ≥ 4), thereby reducing the total area occupied on the slider compared to a single large resistor layout
Solution Approach 2:
Different regions of the slider are assigned different resistance values locally: the first shunt resistor has a lower resistance value optimized for the read pad region, while the second shunt resistor has a higher resistance value optimized for the ELG pad region. This local differentiation allows efficient space utilization while maintaining measurement reliability
2Measurement precision
If higher-cost probe connections with finer pitch/spacing resolution are used to avoid bonding contact errors, then probing accuracy improves, but implementation cost increases
Solution Approach 1:
A substrate is introduced as an intermediary element that provides a common reference potential for both the read pad and ELG pad. This substrate-mediated reference system enables accurate probing using standard-cost probe connections by establishing a stable electrical reference that eliminates measurement errors without requiring expensive fine-pitch probing equipment
3Ease of manufacture
If standard probe connections are used for probing the ELG pad, then manufacturing cost is reduced, but the read pad may be inadvertently contacted causing measurement errors
Solution Approach 1:
The reference potential function is extracted from the read pad and assigned to a dedicated substrate connection. This extraction allows the ELG pad to be probed independently using standard probe connections without the risk of inadvertently contacting the read pad, as the reference potential is now provided by the substrate rather than being shared with the read sensor circuitry
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 provides reliable and cost-effective probing of the read sensor's stripe height, reducing noise interference and minimizing physical space requirements, thus enhancing the accuracy and efficiency of the lapping process.
Implementation Method 1
measuring the change in resistance as the ABS is lapped
Implementation Method 2
The materials of the read sensor may introduce noise into the current that makes this technique unreliable
Data Source
AI summary
Embodiments described herein generally relate to resistive shunt design in a read sensor for providing accurate measurements from an electronic lapping guide (ELG). More specifically, embodiments described herein relate to a transducer resistor shunt structure for low cost probing. A bleed resistor network for a read sensor may comprise one or more first resistors arranged in parallel with one another and a second resistor arranged in series with the one or more first resistors. The resistor arrangement may require a small physical area and reduce or prevent ELG measurement errors.