Batch fabricated servo write head having low write-gap linewidth variation

• US 6,018,444 A
• Filed: 10/28/1997
• Issued: 01/25/2000
• Est. Priority Date: 10/28/1997
• Status: Expired due to Term

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Beck, Patricia A., Poorman, Paul W., Henze, Richard H., Clifford, George M. Jr.
• Primary Examiner(s): EVANS, JEFFERSON A
• Application Number:
  US08/959,509
• Time in Patent Office: 819 Days
• Field of Search: 360/77.12, 360/119-122, 360/124, 360/125
• US Class Current: 360/121
• CPC Class Codes: G11B 15/62 Maintaining desired spacing between record carrier and head
• CPC Class Codes: G11B 5/187 Structure or manufacture of the surface of the head in physical contact with, or immediately adjacent to the recording medium; Pole pieces; Gap features G11B5/265, G11B5/29 , G11B5/31 take precedence
• CPC Class Codes: G11B 5/1871 Shaping or contouring of the transducing or guiding surface
• CPC Class Codes: G11B 5/4893 relative to moving tape
• CPC Class Codes: G11B 5/584 for track following on tapes
• CPC Class Codes: Y10T 29/49032 Fabricating head structure or component thereof
• CPC Class Codes: Y10T 29/49043 Depositing magnetic layer or coating
• CPC Class Codes: Y10T 29/49048 Machining magnetic material [e.g., grinding, etching, polishing]
• CPC Class Codes: Y10T 29/49055 with bond/laminating preformed parts, at least two magnetic
• CPC Class Codes: Y10T 29/4906 Providing winding
• CPC Class Codes: Y10T 29/49789 Obtaining plural product pieces from unitary workpiece
• CPC Class Codes: Y10T 29/49798 Dividing sequentially from leading end, e.g., by cutting or breaking

Abstract

A batch fabrication technique is described that increases the manufacturing efficiency of servo write heads and also improves servo pattern definition for fine features, while reducing tape and head wear. Multiple heads are fabricated as a batch from one or more ferrite wafers. A nominally flat, large wafer surface and a contour suitable for uniform photoresist application and planar photolithography permit fine servo pattern definition with low linewidth variation. Non-magnetic material is photolithographically defined to produce gaps above the spacer. The non-magnetic material may be photoresist, semiconductor materials, glass, metal or the like. The material may even be removed later to leave air gaps. The non-magnetic material forms a region where the field loops out to intersect the passing tape, thereby transferring a magnetic pattern to tape. Additionally, a lower ferrite wafer may be mated to the upper ferrite wafer to complete a magnetic circuit around the gaps. The upper or lower ferrite wafer may have a channel through which an inductive winding passes. Multiple heads may be formed through batch processing of the upper and lower ferrite wafers.

Claims

1. A servo write head for magnetic tape, the head comprising:

first and second ferrite structures;

a non-magnetic material between the first and second ferrite structures to form a spacer and thereby produce a ferrite-nonmagnetic-ferrite arrangement; and

a layer of magnetic material having at least one magnetic gap over the non-magnetic material to form the magnetic pattern for writing a portion of a servo pattern to the tape, the gap having a linewidth variation which is not substantially greater than 0.5 μ

m.

2. The head as set forth in claim 1, wherein the first and second ferrite structures are part of a ferrite wafer, and a plurality of the heads are formed through a batch processing of the ferrite wafer.

3. The head as set forth in claim 1, wherein the layer of magnetic material has a plurality of the magnetic gaps over the non-magnetic material to form the magnetic pattern for writing the servo pattern to the tape.

4. The head as set forth in claim 1, wherein the first and second ferrite structures are part of an upper ferrite wafer, and comprising a lower ferrite wafer mated to the upper ferrite wafer to complete a magnetic circuit around the gap.

5. The head as set forth in claim 4, comprising an inductive winding, wherein the head has a channel through which the inductive winding passes.

6. The head as set forth in claim 4, wherein a plurality of the heads are formed through a batch processing of the upper and lower ferrite wafers.

7. The head as set forth in claim 1, wherein the gap linewidth variation is not substantially greater than 0.1 μ

m.

8. The head as set forth in claim 1, wherein the first and second ferrite structures are part of a ferrite wafer which has a substantially planar head surface;

and

a leading edge, the leading edge being disposed adjacent to the head surface such that the tape contacts the leading edge before passing over the head surface, the leading edge being rounded so as to form an air bearing between the head surface and the tape.

9. The head as set forth in claim 8, wherein the rounding of the leading edge is accomplished through a selected one or more of blending, grinding, machining, and faceting to the head surface.

10. The head as set forth in claim 8, comprising a trailing edge, the trailing edge being disposed adjacent to the head surface such that the tape passes over the trailing edge after passing over the head surface, the trailing edge being rounded.

11. The head as set forth in claim 10, wherein the rounding of the trailing edge is accomplished through a selected one or more of blending, grinding, machining, and faceting from the head surface.

12. The head as set forth in claim 1, wherein the first and second ferrite structures are part of a ferrite wafer, and comprising an inductive winding, wherein the inductive winding passes around a portion of the ferrite wafer.

13. The head as set forth in claim 1, wherein the first and second ferrite structures are part of a ferrite wafer, and the ferrite wafer forms a magnetic shunt around the gap.

14. A servo write method for magnetic tape, the method comprising the steps of:

passing the tape over a substantially planar head surface having a leading edge, the leading edge being disposed adjacent to the head surface such that the tape contacts the leading edge before passing over the head surface, the leading edge being rounded so as to form an air bearing between the head surface and the tape; and

using the head to write servo position code onto the tape, wherein the head comprises;

first and second ferrite structures;

a non-magnetic material between the first and second ferrite structures to form a spacer thereby produce a ferrite-nonmagnetic-ferrite arrangement; and

a layer of magnetic material having at least one magnetic gap over the non-magnetic material to form the magnetic pattern for writing a portion of a servo pattern to the tape, the gap having a linewidth variation which is not substantially greater than 0.5 μ

m.

15. The method as set forth in claim 14, wherein the rounding of the leading edge is accomplished through a selected one or more of blending, grinding, machining, and faceting to the head surface.

16. The method as set forth in claim 14, comprising the step of passing the tape over a trailing edge, the trailing edge being disposed adjacent to the head surface such that the tape passes over the trailing edge prior to passing over the head surface, the trailing edge being rounded.

17. The method as set forth in claim 16, wherein the rounding of the trailing edge is accomplished through a selected one or more of blending, grinding, machining, and faceting from the head surface.