Low resistance coil structure for high speed writer

Details Low resistance coil structure for high speed writer Low resistance coil structure for high speed writer

1998-11-09

2001-12-25

Klimowicz, William (Department: 2652)

Dynamic magnetic information storage or retrieval

Head

Coil

C360S125330

Reexamination Certificate

active

06333830

ABSTRACT:

BACKGROUND
1. Field of the Invention
The present invention relates to the field of magnetic write heads.
2. Description of Related Art
Data is stored on magnetic media by writing to the magnetic media using a write head. Magnetic media can be formed in any number of ways, such as tape, floppy diskette, and hard disk. Writing involves storing a data bit by utilizing magnetic flux to set the magnetic moment of a particular bit or area on the magnetic media. As data density is improved by placing bits closer together, larger magnetic flux is required to set the bits to prevent them from inadvertently being changed by adjacent bits, or by stray magnetic flux.
In addition to improving density, the rate or frequency that data is stored to the media is an important measure of the operational performance of the write head. The operating frequency is determined, in part, by the structures and materials of the write head.
Thin film heads commonly employ separate write and read heads and are typically formed by depositing and etching layers of magnetic, non-magnetic, dielectric, and electrically conductive materials to form the structures of the head. The structures of the head, such as a lower pole structure, a write gap, an upper pole structure, and conductors are fabricated in separate steps. The conductors form a winding that provides magnetic flux along a path through the upper pole structure, across the write gap and into the lower pole structure. The magnetic flux crossing the write gap acts across an air bearing to set the magnetic moment of the media.
To improve the operating frequency of the write head, the overall length of the write head from the air bearing surface is reduced to decrease the magnetic flux path length. To accomplish this, the conductor winding may be moved closer to the air bearing surface. The cross sectional area of the conductor also may be reduced to decrease winding size.
Reducing conductor cross-section and distance to the air bearing surface, however, presents problems. Decreasing conductor size, for example, increases the resistance of the conductor winding causing a potential problem with Johnson Thermal Power Noise. Johnson Thermal Power Noise is given by:
Johnson Thermal Power Noise=
8Π
k
B
TR&Dgr;&ohgr;
where
T=temperature
R=resistance of the coil
&Dgr;&ohgr;=operating frequency bandwidth
As the resistance and operating frequency increase, Johnson Thermal Power Noise poses a greater problem.
Yet another way to improve the operating frequency of the write head is to use high moment materials to form the pole structures. Conventional thin film head design, however, limits the type of materials available for use. High moment materials generally are deposited by vacuum deposition and are prone to cracking when deposited over steep surfaces. As the size of the pole structures are reduced and the conductors are moved closer to the air bearing surface, the layers of conductors forming the winding typically present steep angles. These steep angles limit the deposition methods and type of materials available for forming the upper pole structure, thus presenting impediments to increasing the operating frequency of the write head.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a thin film write head having an upper and lower pole structures and conductor turns forming a winding for generating magnetic flux in the upper pole structure. The conductor is formed with a non-planar top surface. The winding of the present invention may be formed of lower and upper turns. The upper turns may also be formed with a non-planar top surface, a non-planar bottom surface, or both. It is preferred that the bottom surface of the upper conductor turns be coherent with the upper surface of the lower conductor turns.
The non-planar top surfaces may be formed by removing corners formed between a generally planar top surface and abutting side walls. The corners may be removed by ion milling to form the non-planar top surface. The conductor turns may be formed of copper with the non-planar top surface having sloping facets.
The preferred embodiment of the present invention provides reduced coil resistance thereby reducing Johnson Thermal Noise and power dissipation. It also allows for reduced yoke length and reduced stack height while providing low apex angles thereby expanding and improving yoke material deposition to improve head response and operational frequency.
The write head of the present invention may be utilized to provide an improved data storage and retrieval apparatus.


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