Electric heating – Metal heating – By arc
Reexamination Certificate
2002-09-17
2003-12-23
Stoner, Kiley (Department: 1725)
Electric heating
Metal heating
By arc
Reexamination Certificate
active
06667457
ABSTRACT:
BACKGROUND OF THE INVENTION
Magnetic metal alloys such as permalloy are commonly used as one of the materials for forming magnetic head assemblies used in computer data storage devices. It is known in the art that the magnetic surfaces of magnetic head assemblies are attacked by moisture and chemicals causing corrosion, which reduces the reliability and accuracy of the head, and can lead to total disk drive failure.
Permalloy is a magnetic nickel-iron alloy which has excellent magnetic properties, but which is subject to corrosion. In particular, water, chlorides and sulfides are known to corrode permalloy. Other magnetic alloys are also susceptible to corrosion. Corrosion commonly occurs during the slider fabrication process on the wafer, which involves much water processing.
Magnetic head assemblies typically include a plurality of exposed magnetic surfaces, such as pole tips at or on the air bearing surface of the “flying head” assembly, for example. The air bearing surfaces for purposes of this disclosure are the surfaces of the magnetic head which contact the magnetic recording media when the magnetic recording media is not in motion. Frictional contact between the magnetic portions of the air bearing surfaces generated during starting and stopping prevents further corrosion.
Although it is known in the art generally that the air bearing surface of a magnetic head can be coated with a layer of anticorrosive material, this layer is not added until after slider fabrication and therefore does not prevent corrosion that occurs between the end of the wafer process and the placing of the layer of anticorrosive material on the head.
One prior art method of preventing corrosion during slider fabrication is the placement of a corrodible anode in the head assembly. The corrodible anode is constructed of a material having an ionization tendency larger than that of the magnetic material, and therefore will sacrificially corrode in place of the material to be protected. The material corrodes instead of protected material by providing a potential to the protected material.
For example, Japanese patent JP1102710A, Apr. 20, 1989 to Goto Hirochi et al. embeds a thin film corrodible anode in the head structure. The corrodible anode is in contact with magnetic thin films.
However, in prior art methods using corrodible anodes, the corrodible anode remains in the head after processing. As the anode corrodes, it creates corrosion products that remain in the head and which end up in the finished disk drive. The head can run into this debris, resulting in errors.
Another prior art method suggests use of a power supply to provide corrosion protection. However, the user of a power supply is not possible given the grounding requirements for other structures in the disk drive.
The above-mentioned prior art methods fail to disclose a method of protecting the magnetic surfaces of a magnetic head during the slider fabrication process for magnetic recording head assemblies. A corrodible anode which does not remain in the head structure after manufacture, significantly reduces corrosion, does not distort the signal generated by the magnetic recording head, and does not increase the potential for catastrophic hard disk failure would therefore be very desirable.
DISCLOSURE OF THE INVENTION
A slider fabrication assembly is provided according to one embodiment. A slider is formed on a substrate. A corrodible component of the slider such as a read element and/or a write element is exposed to an environment (chemicals, water, air, etc.) in contact with the slider. A kerf region of the substrate is positioned adjacent to the slider. The kerf region is removable from the slider and is removed during some stage of fabrication of the slider such as when slicing the slider from a row of sliders. A sacrificial anode is embedded in the kerf region and exposed to the environment, preferably on the air bearing surface side of the slider. The sacrificial anode is electrically coupled to the component of the slider thereby forming an electrochemical cell. The sacrificial anode is less noble, i.e., more easily corrodible, than the corrodible component of the slider, and thus corrodes first. When the kerf region is removed, the corroded sacrificial anode is removed as well. Thus, the sacrificial node can protect the corrodible slider components during processing, but will not create debris in the disk drive since it is removed with the kerf region.
The sacrificial anode is preferably constructed at least in part of aluminum, zinc, manganese, and/or magnesium, or an alloy of one or more of them. In one embodiment, a connector of a material different than the sacrificial anode couples the sacrificial anode to the component of the slider.
If multiple sliders are being constructed, the kerf region may be defined between aligned sliders. The sacrificial anode is removed with the kerf region during separation of the sliders. The kerf region can be removed via sawing and/or laser cutting.
A method for fabricating a plurality of sliders is also provided. First portions of the sliders are created on a substrate. Each first portion includes a corrodible component. Kerf regions are defined between the sliders. Sacrificial anodes are added to the kerf regions. The sacrificial anodes are exposed to an environment in contact with the sliders (at least after lapping the rows to define air bearing surfaces). Again, the sacrificial anodes are preferably constructed at least in part of aluminum, zinc, manganese, magnesium or an alloy thereof. The sacrificial anodes are connected to the components of the sliders. A remainder of each slider is constructed. The sliders are exposed to a substance that may be corrosive. The substrate is diced into rows. The rows are lapped to define air bearing surfaces. Air bearing surfaces are patterned on the rows. A protective layer is added to each of the sliders to prevent further corrosion and provide wear resistance. Preferably, the protective layer is a carbon-based layer. The kerf regions are removed such as by sawing and/or laser cutting for slicing the sliders from the rows. The sacrificial anodes are removed with the kerf regions.
REFERENCES:
patent: 3855625 (1974-12-01), Garnier et al.
patent: 4130847 (1978-12-01), Head et al.
patent: 4467382 (1984-08-01), Huisman
patent: 4835361 (1989-05-01), Strom
patent: 5023738 (1991-06-01), Prenosil
patent: 6034349 (2000-03-01), Ota
patent: 6049056 (2000-04-01), Balamane et al.
patent: 6059984 (2000-05-01), Cohen et al.
patent: 6255621 (2001-07-01), Lundquist et al.
patent: 1102710 (1989-04-01), None
patent: 2089210 (1990-03-01), None
patent: 3181009 (1991-08-01), None
patent: 7282410 (1995-10-01), None
Andricacos et al., “Inductive Recording Head Design for Electrochemical Potential Control”, Sep. 1992, Yorktown.
Lee Edward Hin Pong
Robertson Neil Leslie
Thomas Edward Dinan
Hitachi Global Storage Technologies
Johnson Jonathan
Kotab Dominic M.
Silicon Valley IP Group PC
Stoner Kiley
LandOfFree
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