Reduced stiffness printed circuit head interconnect

Details Reduced stiffness printed circuit head interconnect Reduced stiffness printed circuit head interconnect

1999-12-07

2004-03-30

Renner, Craig A. (Department: 2652)

Dynamic magnetic information storage or retrieval

Head mounting

Disk record

C360S244300

Reexamination Certificate

active

06714384

ABSTRACT:

FIELD OF THE INVENTION
The invention relates generally to magnetic disc drives and head gimbal assemblies, more particularly, to magnetic disc drives and head gimbal assemblies having a printed circuit head interconnect with a different material thickness.
BACKGROUND OF THE INVENTION
Modern computers require media in which digital data can be quickly stored and retrieved. Magnetizable (hard) layers on discs have proven to be a reliable media for fast and accurate data storage and retrieval. Disc drives that read data from and write data to hard discs have thus become popular components of computer systems. To access memory locations on a disc, a read/write head (also referred to as a “slider”) is positioned slightly above the surface of the disc while the disc rotates beneath the read/write head at an essentially constant velocity. By moving the read/write head radially over the rotating disc, all memory locations on the disc can be accessed. The read/write head is typically referred to as “flying” head because it includes a slider aerodynamically configured to hover above the surface on an air bearing located between the disc and the slider that is formed as the disc rotates at high speeds. The air bearing supports the read/write head above the disc surface at a height referred to as the “flying height.”
In conventional disc drives, one or more hard discs are coupled to and rotate about a spindle, each disc presenting two opposite substantially flat surfaces for reading and recording. Typically, multiple rotating hard discs are stacked in a parallel relationship with minimal spacing between adjacent discs. Accordingly, the read/write heads must be designed to move within the narrow space between adjacent discs and fly close to the disc surfaces. To achieve this positional capability, the read/write heads in typical disc drives are coupled to the distal end of thin, arm-like structures called head gimbal assemblies, or HGAs. The HGAs are inserted within the narrow space between adjacent discs. The HGAs are made of materials and thicknesses as to be somewhat flexible and allow a measure of vertical positioning as the read/write heads hover over the surface of the rotating discs.
Each HGA is coupled at its proximal end to a rigid actuator arm. The actuator arm horizontally positions the HGA and read/write head over the disc surface. In conventional disc drives, actuator arms are stacked, forming a multi-arm head stack assembly. The head stack assembly moves as a unit under the influence of a voice coil motor to simultaneously position all head gimbal assemblies and corresponding read/write heads over the disc surfaces.
The HGA in a typical disc drive includes four components: 1) a read/write head or slider, features a self-acting hydrodynamic air bearing and an electromagnetic transducer for recording and retrieving information on a spinning magnetic disc; 2) a gimbal, which is attached to the slider, is compliant in the slider's pitch and roll axes for the slider to follow the topography of the disc, and is rigid in yaw and in-plane axes for maintaining precise slider positioning; 3) a load beam or flexure, which is attached to the gimbal and to the actuator arm which attaches the entire HGA to the actuator. The load beam is compliant in a vertical axis to allow the slider to follow the topography of a disc, and is rigid in the in-plane axes for precise slider positioning. The load beam also supplies a downward force that counteracts the hydrodynamic lifting force developed by the slider's air bearing; and 4) a printed circuit head interconnect, which is disposed on the load beam and electrically coupled to the transducer of the slider. The printed circuit head interconnect sends the electric signals to and from the transducer of the slider.
The gimbal of the HGA traditionally includes a stainless steel member of substantially less thickness than the load beam of the HGA. The geometry of the gimbal allows an easy movement out of the plane of a disc but restricts an in-plane movement. Since the gimbal and the head interconnect are both attached to the slider, the head interconnect as well as the gimbal influence the mechanical characteristics, for example, fly height, etc., of the slider during a read/write operation.
One of the challenges facing a designer of a printed circuit head interconnect of an HGA is to minimize torque bias imparted to the slider due to a read/write operation. Torque affects a fly height, which in turn affects the ability of a transducer to read/write digital data from/to a disc. Generally, torque is the product of angular displacement and torsional stiffness. Torque is typically described as having a pitch direction and a roll direction. In a pitch direction, the slider rotates about an axis (referred to as a pitch axis) transverse to a longitudinal axis of a slider suspension and parallel to the surface plane of the disc. In a roll direction, the slider rotates about an axis (referred to as a roll axis) parallel to the longitudinal axis of the slider suspension.
One of the problems of an HGA is a fly height variation during an operation. The fly height variation may cause variation in electromagnetic signals used for reading/writing data from/to a disc. In addition, an excessive fly height variation, particularly when fly heights are relatively small, may raise reliability issues related to wear of a head-disc interface. Accordingly, a lower fly height variation is needed. Reduced HGA stiffness has proven to be a solution to such problem. One way of reducing HGA stiffness could be to reduce the material thickness of the printed circuit head interconnect. However, reducing the material thickness of the printed circuit head interconnect makes the printed circuit head interconnect fragile and difficult to handle, resulting in decreased yields and increased part costs. For a typical HGA, conductive materials on the printed circuit head interconnect are required to be large enough that their stiffness is considerable compared to the gimbal of the HGA. Further, not only is the stiffness due to the printed circuit head interconnect undesirable, but also the material properties of the printed circuit head interconnect are not predictable because the material properties vary with respect to temperature. This makes design decisions difficult. Furthermore, the different coefficients of thermal and hygroscopic expansion between the gimbal and head interconnect materials result in differential expansion causing changes in an angular displacement when the HGA is exposed to changes in heat and humidity.
It is, therefore, desirable to make the stiffness contribution due to the printed circuit head interconnect be as small as possible.
It is with respect to these and other considerations that the present invention has been made.
SUMMARY OF THE INVENTION
In accordance with this invention, the above and other problems were solved by providing a printed circuit head interconnect of a head gimbal assembly (HGA) having different material thicknesses in appropriate regions of the printed circuit head interconnect. The regions which need to have a lower stiffness are made thinner than the rest of the regions. The rest of the regions are made thick and robust enough to support the HGA.
In one embodiment of the present invention, a printed circuit head interconnect for electrically coupling to a magnetic head of a disc drive includes a lamination sheet of materials having dielectric materials and conductive materials. A thickness of the lamination sheet of materials is different in different regions of the printed circuit head interconnect.
Still in one embodiment, a thickness of the dielectric materials is different in different regions of the printed circuit head interconnect. Alternatively, a thickness of the conductive materials is different in different regions of the printed circuit head interconnect.
Further in one embodiment, a first region is thinner than a second region. The first region is formed by etching the materials by use of a resist mask pattern. Th

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