Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2001-04-25
2004-06-08
Miller, Brian E. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
C360S235100
Reexamination Certificate
active
06747841
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the field of magnetic data storage and retrieval systems. In particular, the present invention relates to a thin film transducing head having improved performance due to a reduced thermal pole-tip recession.
In a magnetic data storage and retrieval system, a thin film transducing head typically includes a transducer, a substrate upon which the transducer is built, and an overcoat deposited over the transducer. The transducer, which typically includes a writer portion for recording magnetically-encoded information on a magnetic media and a reader portion for retrieving that magnetically-encoded information from the magnetic media, is formed of multiple layers successively stacked upon the substrate. The volume of the transducer is typically much smaller than both the volume of the substrate and the volume of the overcoat.
The layers of the transducer, which include both metallic and insulating layers, all have differing mechanical and chemical properties than the substrate. These differences in properties affect several aspects of the transducer. First, the layers of the transducing head will be lapped at different rates. Thus, when an air bearing surface (ABS) of the transducing head is lapped during its fabrication, differing amounts of the layers will be removed—resulting in the transducing head having an uneven ABS. Commonly, a greater amount of the metallic layers of the transducer will be removed during the lapping process than will be removed from the substrate. Thus, this lapping process results in a Pole Tip Recession (PTR) of the metallic layers of the transducer with respect to the substrate. The PTR of a particular layer is defined as the distance between the air bearing surface of the substrate and the air bearing surface of that layer.
The differing mechanical and chemical properties of the substrate and transducer layers further affect the air bearing surface during operation of the transducing head. As the magnetic data storage and retrieval system is operated, the transducing head is subjected to increasing temperatures within the magnetic data storage and retrieval system. In addition, a temperature of the transducing head itself, or a part thereof, may be significantly higher than the temperature within the magnetic data storage and retrieval system due to heat dissipation caused by electrical currents in the transducer.
The coefficient of thermal expansion (CTE) of materials used in forming the substrate is typically much smaller than the CTE of materials used in forming the metallic layers of the transducer. Due to the larger CTE of the transducer's metallic layers, those layers will tend to expand a greater amount in response to high temperatures than will the substrate. Thus, when the transducing head is subjected to higher operating temperatures, the metallic layers tend to protrude closer to the magnetic disc than the substrate, thereby affecting the PTR of the transducer. This change in PTR caused by temperature is referred to as the Thermal PTR (T-PTR).
During operation of the magnetic data storage and retrieval system, the transducing head is positioned in close proximity to the magnetic media. A distance between the transducer and the media is preferably small enough to allow for writing to and reading from the magnetic medium with a large areal density, and great enough to prevent contact between the magnetic media and the transducer. Performance of the transducer depends primarily on this distance.
To keep the distance between the transducing head and the magnetic media constant, PTR should not change significantly with temperature. IfT-PTR is large, then the spacing between the transducer and the medium will change significantly with temperature, thereby requiring that the low-temperature fly height be high enough to accommodate this variation at higher operating temperatures. On the other hand, if T-PTR is close to zero, the low-temperature fly height can be reduced.
Commonly assigned and co-pending provisional Application No. 60/221,549, entitled “Design and Process of Making Planarized Insulating Layers with Low Thermal Expansion Using Planarization of Material with Larger Thermal Expansion”, filed on Jul. 28,2000, discloses an improved transducing head having low-CTE insulating layers positioned substantially coplanar to at least one of a plurality of metallic layers of the transducing head to reduce T-PTR in the transducing head.
In addition to coplanarly positioning low-CTE insulating layers as disclosed in provisional Application No. 60/221,549, further improvements are desirable to reduce T-PTR and thereby allow smaller fly heights.
BRIEF SUMMARY OF THE INVENTION
A magnetic head has an air bearing surface, a substrate, a data transducer and a composite overcoat layer. The data transducer is positioned upon the substrate adjacent the air bearing surface. The data transducer includes a plurality of metallic layers. The composite overcoat layer is positioned upon the data transducer on a side of the data transducer opposite the substrate. An effective coefficient of thermal expansion of the composite overcoat layer is substantially equal to a coefficient of thermal expansion of a material forming the substrate.
REFERENCES:
patent: 4853810 (1989-08-01), Pohl et al.
patent: 5021906 (1991-06-01), Chang et al.
patent: 5083365 (1992-01-01), Matsumoto
patent: 5283942 (1994-02-01), Chen et al.
patent: 5303105 (1994-04-01), Jorgenson
patent: 5377058 (1994-12-01), Good et al.
patent: 5452164 (1995-09-01), Cole et al.
patent: 5473486 (1995-12-01), Nepela et al.
patent: 5636088 (1997-06-01), Yamamoto et al.
patent: 5640753 (1997-06-01), Schultz et al.
patent: 5663856 (1997-09-01), Packard
patent: 5687045 (1997-11-01), Okai et al.
patent: 5710683 (1998-01-01), Sundaram
patent: 5771570 (1998-06-01), Chhabra et al.
patent: 5793207 (1998-08-01), Gill
patent: 5896243 (1999-04-01), Koshikawa et al.
patent: 5896244 (1999-04-01), Watanabe et al.
patent: 5898106 (1999-04-01), Babcock et al.
patent: 5898542 (1999-04-01), Koshikawa et al.
patent: 5909340 (1999-06-01), Lairson et al.
patent: 5949627 (1999-09-01), Williams et al.
patent: 5963401 (1999-10-01), Dee et al.
patent: 5991113 (1999-11-01), Meyer et al.
patent: 6074566 (2000-06-01), Hsiao et al.
patent: 6078455 (2000-06-01), Enarson et al.
patent: 6130809 (2000-10-01), Santini
patent: 6154952 (2000-12-01), Tangren
patent: 6212040 (2001-04-01), Hungerford
patent: 6219200 (2001-04-01), Waki et al.
patent: 6252741 (2001-06-01), Ahn
patent: 6366428 (2002-04-01), Yamanaka et al.
patent: 6373659 (2002-04-01), Hamaguchi et al.
patent: 6441994 (2002-08-01), Wang et al.
patent: 6473265 (2002-10-01), Zhou et al.
patent: 6477007 (2002-11-01), Shukh et al.
patent: 6661605 (2003-12-01), Pust et al.
patent: 2002/0006018 (2002-01-01), Narumi et al.
R.M. Bozorth, Ferromagnetism,IEEE Press.
H. Masumoto, ‘On the Thermal Expansion of the Alloys of Iron, Nickel, and cobalt and the Cause of the Small Expansibility of Alloys of the Invar Type’,Science Reports of the Tohoku Imperial University, vol. XX, 1931.
Olim Moshe
Pust Ladislav R.
Kinney & Lange , P.A.
Miller Brian E.
Seagate Technology LLC
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