Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2001-01-05
2003-07-15
Letscher, George J. (Department: 2653)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06594112
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to recording heads for use with magnetic recording media. More specifically, the present invention is an improved structure and method of manufacturing a recording head, resulting in better throat definition.
2. Description of the Related Art
Recording heads for use with magnetic recording media typically include a pair of magnetically coupled poles, with a coil located adjacent to one of the poles for inducing a magnetic field within the poles. A typical longitudinal recording head will have two poles having approximately the same surface area on their bottom surfaces, while a typical perpendicular recording head will have a main pole and opposing pole, with the main pole having a significantly smaller bottom surface area than the opposing pole. A common magnetic recording medium includes a layer having a plurality of magnetic tracks, with each track divided into sectors. The tracks are separated by nonmagnetized transitions. If perpendicular recording is used, the recording medium will typically include a layer of magnetically soft material below the recording layer.
The tip of the main right pole is typically in very close proximity to the tip of the opposing pole. The distance for which the main right pole and opposing pole maintain their close proximity is known as the throat height. The throat height in presently used recording heads is typically defined by a layer of hard baked photoresist. The process of spinning the photoresist fluid across the surface to which it is applied is a difficult process in which to control the thickness of the photoresist. Additionally, the photoresist shrinks at uncontrolled rates during the hard baked process. Furthermore, the hard baked process causes deterioration within the layers of a typical GMR read element or spin valve.
A main write pole having a proper tip structure is critical to the magnetic performance of the recording head. Therefore, a recording head having a more precisely defined throat height is desired. Additionally, a method of manufacturing a recording head having a precisely defined throat height is needed.
SUMMARY OF THE INVENTION
The present invention is an improved longitudinal recording head for use with magnetic recording media, and a method of making such a recording head.
A preferred embodiment of the present invention includes a recording head combining a read portion and a write portion, although the invention is primarily directed towards the write portion of the recording head. The read portion of the recording head includes a read element, which may be a GMR read element or a spin valve, and a pair of magnetic shields on either side of the read element. The write portion includes a main pole and an opposing pole magnetically coupled to the main pole. An electrically conductive coil is located adjacent to the main pole. One of the two shields of the read element may also serve as the opposing pole. The tips of the main and opposing poles incorporate a throat, wherein the main pole and opposing pole are in close proximity to each other. The height above the bottom surface of the poles for which the two poles are in such close proximity is known as the throat height. The throat height for a recording head of the present invention is defined by a plated layer of NiPd, directly adjacent to the write gap.
The process of manufacturing a recording head of the present invention begins by providing a substrate having a pair of shields with a read element therebetween. The shield farthest from the substrate may also function as one of the two opposing write poles. The surface of this shield is chemical mechanical polished to ensure that it is completely flat. A write gap, preferably alumina, is deposited on this surface. The NiPd throat height structure is then plated on top of the write gap. The edge of the throat height structure may be shaped using ion milling if desired. The initial portions of the write pole are then deposited, with a lower initial portion deposited on top of the write gap and bottom of the throat height structure, and an upper portion deposited so that it is magnetically coupled with the opposing pole/shield. Insulating material, preferably alumina, is deposited over the remainder of the throat height structure. The coil may then be deposited, followed by additional insulation and the remainder of the main write pole.
A typical magnetic recording medium includes a recording layer having a plurality of magnetically permeable tracks separated by nonmagnetized transitions. Each track is further divided into sectors.
The recording head is separated from the magnetic recording medium by a distance known as the flying height. The magnetic recording medium is moved past the recording head so that the recording head follows the tracks of the magnetic recording medium, with the write gap oriented perpendicular to the tracks and the direction of travel. Current is passed through the coil to create magnetic flux within the two opposing poles. The magnetic flux passing across the write gap will cause the magnetic fields in the tracks to align with the magnetic flux of the two opposing poles. Changing the direction of electric current changes the direction of the flux created by the recording head, and therefore, the magnetic fields within the magnetic recording medium. A binary “0” is recorded by maintaining a constant direction of magnetic flux through the main pole, and a binary “1” is recorded by changing the direction of magnetic flux through the main pole.
The use of plated NiPd to define the throat height instead of the photoresist as used in prior recording heads enables the throat height and throat configuration to be controlled with a significantly greater degree of precision. A properly configured throat will direct magnetic flux so that it enters the write gap perpendicular to the magnetic recording medium, thereby creating a higher gap field and improved “write bubble”. Additionally, steps may be created during the manufacturing process to ensure accurate alignment of the pole tip structure to the throat height structure. Furthermore, the use of plated NiPd instead of photoresist avoids the need for a hard bake process to cure the photoresist, thereby avoiding the various problems caused by this process. The hard bake process can degrade the various layers within the read element. During the hard bake process, the throat height structure shrinks at uncontrolled rates, thereby causing variation in the throat height. Photoresist is applied by spinning the photoresist liquid over the desired surface, a process within which it is difficult to control the thickness of the photoresist applied. Thermal expansion and contraction during the hard bake process also creates a possibility of cracking caused by the resulting stresses within the recording head structure.
It is therefore an aspect of the present invention to provide a longitudinal recording head for use with magnetic recording media having a more precisely defined throatheight than prior recording heads.
It is another aspect of the present invention to provide a method of manufacturing a longitudinal recording head wherein the throatheight may be more precisely controlled.
It is a further aspect of the present invention to provide a longitudinal recording head having an improved write bubble.
It is another aspect of the present invention to provide a longitudinal recording head free of thermally induced stresses.
It is a further aspect of the present invention to provide a method of manufacturing a longitudinal recording head that does not result in degradation of the read element.
These and other aspects of the invention will become apparent through the following description and drawings.
REFERENCES:
patent: 3940797 (1976-02-01), Brock et al.
patent: 3955213 (1976-05-01), Brower et al.
patent: 4017965 (1977-04-01), Brutsch et al.
patent: 4100584 (1978-07-01), Behr et al.
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patent: 4219855 (1980-08-01), Jones, Jr
Crue Billy Wayne
Rottmayer Robert Earl
Beacham Christopher R.
Lenart, Esq. Robert P.
Letscher George J.
Pietragallo Bosick & Gordon
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