Dynamic magnetic information storage or retrieval – Head mounting – Disk record
Reexamination Certificate
1998-11-19
2001-08-28
Ometz, David L. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
Disk record
C360S234600
Reexamination Certificate
active
06282063
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to disk drive suspensions, and more particularly, to the bonding of the sliders in such suspensions to the suspension flexure tongues.
2. Related Art
The flexure tongue of a magnetic or magnetic-optical recording head suspensions has as one of its functions providing a surface for bonding attachment of the slider. This surface is generally flat to provide the maximum bonding surface area between the slider and the flexure tongue. In some designs, this surface also includes a dimple to provide a point of contact and a point of rotation between the flexure and the applied load supplied by the load beam. The adhesive bond between the slider and the flexure tongue is required to carry some of the loads applied to the slider by the external environment. These loads include shear, tension, compression, and bending.
Of these loads, three immediately test the adhesive bond. Shear (horizontal) load between the suspension and the slider is due to friction of the disk, acceleration of the slider across tracks during accessing (moving to a new radial location on the disk), and horizontal (in the plane of the disk) shock from movement of the disk drive. The tension load the slider applies to the adhesive bond joint between the slider and the flexure tongue is due to vertical shock, and liftoff, as is the bending load. Tension and shear loads are the most significant.
To achieve an adhesive bond between the slider and the flexure tongue, typically one or more small deposits of fluid, curable adhesive, “dots”, are applied to the flexure tongue portion of the suspension before it is moved into contact with the slider in a bonding fixture which holds the assembly in the exact correct position until enough cure of the adhesive has taken place that the assembled slider/suspension combination can be removed from the fixture safely, that is, without relative movement from the correct position. The cure is then continued without fixturing until the cure is complete. The adhesives are chosen for their low outgassing, long pot life, adhesion strength, environmental and safety compatibility, and cost. It is common to have an adhesive that will spot cure under UV light exposure, and then final cure under thermal (oven cure) process.
It is known to use a small hole or holes in the flexure tongue as shown in U.S. Pat. No. 5,008,768 to Carlson, Zarouri and Coon to enhance bond strength by forming a rivet-head like structure so that the adhesive will seep through the hole and form a three dimensional bond instead of a two dimensional bond. Other small holes are used to allow UV light to pass through the load beam and flexure to initiate the cure in some types of UV curing adhesives.
SUMMARY OF THE INVENTION
The requirement for increased bond strength over past requirements stems from the trend toward higher shock loads resistance, i.e. an ability to withstand more “G” forces. The requirement for higher shock load resistance is increasing as more disk drives are being designed for portable/mobile applications.
This requirement cannot be met by increasing the adhesive area, and thus the areal amount of adhesive, for even as higher bond strengths are needed the trend is to smaller and smaller sliders, so the bonding area available is getting smaller.
The decrease in size of suspensions and their components has created another difficulty beyond maintaining or increasing adhesive bond strength. The adhesive must be fluid to apply to the bonding surfaces, but should not extend into areas where its presence will interfere with the clearance between the slider/flexure tongue and other parts of the flexure such as the outrigger area or the load beam. The adhesive must be confined to its proper application area and not be permitted to flow (by drip, capillary, run, or otherwise) beyond its intended locus. Ongoing size reductions in suspension parts increase the difficulty of controlling adhesive placement since the clearance between the different parts of the assembly becomes less. Insufficient or poorly placed adhesive will cause a failure, but excess adhesive may bridge between the flexure tongue or slider, its intended locus, and the flexure outrigger or other part of the assembly causing a failure of a different sort.
Under ideal conditions the bond strength between a slider and flexure tongue will be as high as about 3000 psi. A typical pico or 30% slider provides about 0.002 square inches at most available for bonding. With a 3000-psi adhesive, a slider to flexure tongue bond strength of a maximum of 6 pounds is possible. This is equivalent to several thousand “G”s, and more than sufficient for the applications presently known. Nonetheless, pico slider adhesion sometimes fails, with fatal results to the assembly and a lowering of yields.
It is an object therefore of the present invention to provide improvements in the bonding of slider to flexure tongues. It is a further object to provide more secure bonding through increases in bond adhesive mass, confinement of the adhesive in the proper locus, and texturing of the bonding surface opposite the slider. It is a further object to control the flow paths of the adhesive to prevent bridging between the tongue and flexure outriggers. Still another object is to increase the apparent length of the tongue edges adhered to the slider for additional bonding improvement.
These and other objects of the invention, to become apparent hereinafter are realized in basic form by imposing a partial etch pattern on the bonding side, that is the slider-facing side of the flexure tongue to increase the contact area available for the adhesive by roughening it. The etching also serves to diminish or prevent capillary flow of the adhesive toward areas where it is not desired. The area of the flexure tongue where the dimple force is applied on the far (non-slider) side is not etched or otherwise changed so that the contact area of the dimple is as smooth, flat, and stiff as possible. In addition, in a further embodiment, the perimeter of the flexure tongue is increased with etch-formed fingers such that the adhesive will flow across the fingers for increased adhesion but not flow out from the tongue area to the opposing outriggers.
In particular, the invention provides a disk drive suspension flexure and slider assembly, the flexure comprising an outrigger portion and a tongue portion, the tongue portion having a slider-attaching surface extending in a surface plane, the slider being fluid adhesive-attached to the tongue portion at a predetermined attachment locus on the tongue slider-attaching surface, the slider-attaching surface being surface-etched in surface roughening relation opposite the slider in slowing relation to fluid adhesive flow from the attachment locus.
In this and like embodiments, typically, the etched slider-attaching surface and the slider are substantially coextensive, and the slider-attaching surface is etched below the surface plane to increase the mass of fluid adhesive at the slider and the strength of the adhesive bond.
In a further embodiment, the invention provides a disk drive suspension flexure and slider assembly, the flexure comprising an outrigger portion and a tongue portion, the tongue portion having a slider-attaching surface extending in a surface plane, the slider being fluid adhesive-attached to the tongue portion at a predetermined attachment locus on the tongue slider-attaching surface, the slider-attaching surface being surface-etched below the surface plane opposite the slider and at least partially circumferentially of the attachment locus in trough-forming relation against fluid adhesive flow beyond the trough.
In this and like embodiments, typically: the trough is of uniform depth throughout its length; the trough has a roughened surface for slowing flow of adhesive fluid therethrough; the trough extends fully circumferentially about the attachment locus; the trough defines a repository for the fluid adhesive, whereby the adhesive is locally of a depth greater t
Bachand Louis J.
Magnecomp Corp.
Ometz David L.
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