Vertically Stacked DFH Heaters for Independent Protrusion Control
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Solution Overview
Problem
Existing merged read/write heads face challenges in achieving independent control of read and write gap protrusions, leading to inefficiencies in fly height control, increased power consumption, and limited actuation times due to the distance of heater elements from the write pole tip and read head sensor, resulting in suboptimal gamma ratios and reliability issues.
Innovation Solution
The implementation of two dynamic fly heaters, one proximate to the TMR element in the read head and another near the write pole tip in the write head, allows for independent control of read and write gap protrusions, enabling fast actuation and low power consumption by adjusting the resistance ratio between the heaters, which are strategically positioned and recessed from the air bearing surface to optimize gamma ratio and reduce mechanical impact sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single heater is used to control fly height, then device complexity is reduced, but independent control of read and write gap protrusions is lost leading to suboptimal gamma ratios
Solution Approach 1:
The single heater is divided into two separate heaters: a first heater positioned near the write pole tip and a second heater positioned near the read head sensor. This segmentation allows independent control of write gap protrusion and read gap protrusion, enabling precise gamma ratio control while maintaining relatively simple device structure.
Solution Approach 2:
Each heater is positioned at a specific location to provide localized thermal control: the first heater controls the write pole tip region while the second heater controls the read head sensor region. This local quality approach enables differentiated control of gap protrusions at different locations, achieving optimal gamma ratio without excessive complexity.
2Ease of manufacture
If heater elements are positioned far from the write pole tip and read head sensor, then manufacturing is easier, but actuation time increases and power consumption increases
Solution Approach 1:
The heaters are pre-positioned in recesses within the air bearing surface at optimal distances from the write pole tip and read head sensor. This preliminary positioning during manufacturing ensures that when activated, the heaters immediately affect the gap protrusion without requiring long thermal conduction paths, thus reducing actuation time while maintaining ease of manufacture.
Solution Approach 2:
The recess structures act as thermal intermediaries, concentrating and directing heat from the heater elements directly to the write pole tip and read head sensor. This intermediary structure improves thermal coupling efficiency, reducing the distance heat must travel and thereby decreasing actuation time without complicating the manufacturing process.
3Quantity of substance
If fly height is reduced to increase storage density, then areal density improves, but reliability decreases due to increased risk of head-media contact
Solution Approach 1:
The system dynamically adjusts fly height by independently controlling the protrusion of the write pole tip and read head sensor through separate heater activation. This dynamic control allows the head to maintain optimal spacing from the media during operation, reducing contact risk while enabling low fly height operation for high storage density.
Solution Approach 2:
The system changes the thermal parameters (heater power, temperature distribution) to precisely control the gap protrusion of different head components. By adjusting these parameters, the fly height can be optimized to balance storage density requirements with reliability concerns about head-media contact.
4Object-affected harmful factors
If thermal expansion is used to control fly height, then mechanical wear is reduced, but gamma ratio control becomes difficult when only one heater is used
Solution Approach 1:
The thermal control function is segmented into two independent heaters that can be activated separately to control different aspects of gap protrusion. This segmentation enables precise control of the gamma ratio (the relationship between mechanical minfly point and magnetic spacing) while maintaining the benefits of thermal expansion for reducing mechanical wear.
Solution Approach 2:
Each heater provides localized thermal expansion control at specific locations (write pole tip and read head sensor). This local quality approach allows independent adjustment of protrusion at each location, enabling precise gamma ratio control while using thermal expansion to minimize mechanical wear throughout the system.
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 configuration enables rapid and reliable read and write operations with reduced power consumption by allowing precise control of gap protrusions, achieving a gamma ratio close to 1, thus enhancing the reliability and performance of the merged read/write head.
Implementation Method 1
a first dynamic fly heater (DFH) proximate to the main pole in a perpendicular magnetic recording (PMR) head
Implementation Method 2
the heat generated when a current is applied to the coils in a write head tends to cause a thermal expansion of the write pole toward the magnetic media
Implementation Method 3
a second DFH heater proximate to a tunneling magnetoresistive (TMR) element in a read head
Implementation Method 4
heating of layers in the vicinity of the sensor in the read head causes thermal expansion which results in a read head protrusion toward the magnetic media
Data Source
AI summary
A vertically stacked DFH design in a read/write head is disclosed that allows independent control of write gap protrusion and read gap protrusion. A first heater is formed in an insulation layer proximate to a sensor in a read head. A second heater is formed in a second insulation layer proximate to the write pole tip in a main pole layer. The two heaters are connected in series or in parallel through leads to a power source that activates the heaters. In one embodiment, the heaters have a fixed resistance ratio. Preferably, there are two drivers in the power source so that a first power can be applied to the first heater and a second power can be applied to the second heater to enable an adjustment of reader protrusion/writer protrusion or gamma ratio. Fast reader and writer actuation is achieved and low power consumption is realized.