HAMR Head Heat Sink Segmentation for NFT Thermal Management
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Solution Overview
Problem
Conventional heat-assisted magnetic recording (HAMR) heads face issues with deformation and oxidation of the near-field transducer (NFT) and main magnetic pole due to heat, leading to reduced reliability and efficiency, as well as increased power consumption and lower areal density.
Innovation Solution
The implementation of additional heat-sink materials on the cross-track sides of the main pole and waveguide, along with an optically reflective material between the waveguide and heat-sink, to reduce the temperature of the NFT and main pole, thereby minimizing deformation and oxidation, and enhancing optical efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat is applied to the recording material for HAMR writing, then the coercivity is reduced enabling writing, but the NFT and main pole temperature rise causing deformation and oxidation
Solution Approach 1:
The heat sink structure is segmented into multiple regions: a first heat sink region adjacent to the main pole and a second heat sink region adjacent to the waveguide. This segmentation allows targeted thermal management at different locations, effectively cooling both the main pole and NFT without requiring a single large heat sink that would complicate the head structure.
Solution Approach 2:
A thermal shunt is introduced as an intermediary thermal conduction path between the NFT and the first heat sink region. This thermal shunt acts as a heat transfer bridge, efficiently conducting heat away from the NFT to the main pole heat sink region, thereby reducing NFT temperature without directly thermal-coupling the waveguide to the main pole heat sink.
2Productivity
If laser power is increased to improve heating efficiency, then the thermal gradient increases, but power consumption increases
Solution Approach 1:
The patent converts the harmful thermal energy that would otherwise be wasted into a beneficial cooling effect by directing it through the thermal shunt to the heat sink regions. This回收利用 of thermal energy reduces the need for additional laser power to maintain the required thermal gradient, thereby lowering overall power consumption while maintaining or improving areal density.
Solution Approach 2:
The patent optimizes the thermal conductivity parameters of the thermal shunt and heat sink regions to achieve efficient heat transfer. By carefully selecting and positioning materials with appropriate thermal conductivities, the system achieves effective cooling with minimal impact on the thermal gradient required for HAMR writing, thus reducing the laser power needed.
3Reliability
If heat sink material is added to cool the NFT, then deformation is reduced, but device complexity increases
Solution Approach 1:
The patent merges the heat sink functionality with existing head structures by positioning the first heat sink region adjacent to the main pole and the second heat sink region adjacent to the waveguide. This integration allows the heat sink to be incorporated into the existing magnetic head architecture without requiring separate, complex cooling systems, thereby reducing overall device complexity while maintaining effective thermal management.
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 reduces the likelihood of NFT deformation and main pole oxidation, improves optical efficiency, and lowers laser power consumption, resulting in increased areal density and improved head reliability.
Implementation Method 1
The thermal shunt is in contact with the NFT output tip and the first heat-sink material so that heat flows to the first heat-sink material through the thermal shunt
Implementation Method 2
The second heat-sink material further reduces the temperature of the NFT, and thus the likelihood of NFT deformation. The second heat-sink is in contact with the NFT and thermal shunt so the heat from the NFT output tip flows to the second heat sink material through the NFT and the thermal shunt
Implementation Method 3
In some embodiments, optically reflective material may be located between the waveguide and the second heat-sink material to improve the optical efficiency of the NFT
Implementation Method 4
A NFT with a generally triangular or trapezoidal shaped output end is described in US 8,705,327 B2 assigned to the same assignee as this application. In this NFT an evanescent wave generated at a surface of the waveguide couples to surface plasmons excited on the surface of the NFT and a strong optical near-field is generated at the apex of the output end
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A heat-assisted magnetic recording (HAMR) head has a gas-bearing slider that supports a near-field transducer (NFT) and a main magnetic pole. First heat-sink material is located on the cross-track sides of the main pole and second heat-sink material is located on the cross-track sides of the waveguide. The second heat-sink material may be in contact with the first heat-sink material, and a thermal shunt of high thermal conductivity may interconnect the NFT with the first and second heat-sink material. Heat from the NFT output tip flows to the second heat sink material through the NFT and the thermal shunt. Optically reflective material may be located between the waveguide and the second heat-sink material to improve the optical efficiency of the NFT.