Electric heating – Metal heating – By arc
Reexamination Certificate
2000-01-31
2001-07-03
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
By arc
C219S121690
Reexamination Certificate
active
06255621
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to the manufacture of air-bearing sliders used for supporting the read/write heads in magnetic recording hard disk drives, and more particularly to a method for separating sliders from rows of uncut sliders.
BACKGROUND OF THE INVENTION
In a hard disk drive each magnetic recording data storage disk surface has an associated slider. The slider has a side that faces the disk that includes an air-bearing surface (ABS), and a back or trailing side that supports the patterned read/write head. In operation of the disk drive, the disks are rotated and the sliders are supported with their ABS very close to the disk surfaces. Because of the extremely close proximity of the sliders and their associated disk surfaces, and the high stresses encountered when the sliders are brought into contact or removed from contact with the disk surfaces, it is advantageous that the sliders have blended or rounded edges at their disk sides.
The sliders are built in wafer form, in which a large number of magnetic read/write heads are formed using semiconductor processing techniques on the surface of a ceramic wafer. Typically up to 20,000 heads can be patterned on a 5-inch diameter wafer. The wafer is formed of a ceramic composite material containing TiC and Al
2
O
3
, as well as trace amounts of other materials, such as MgO. After the read/write heads are patterned, the wafer is cut into blocks called “quads”, the quads are cut into rows, and the rows are cut into sliders. Each of these cutting processes is typically performed with a diamond-tipped saw. Once the wafer rows have been cut from the wafer, the individual sliders can be partially cut with a saw and then later completely separated by a mechanical snapping or cleaving process. The sawing process, including the partial cutting process of the sliders in the wafer row, is described in detail in IBM's U.S. Pat. No. 5,739,048, which is incorporated herein by reference. In that patent, FIG. 1A shows a wafer with the patterned read/write heads, FIG. 2A shows a wafer row, and FIGS. 8-9 show a wafer row with partially separated sliders.
There are many disadvantages to the sawing process. The manufacturing cost of the sawing process is affected by several physical limitations. The size of the saw blade and therefore the size of the kerf area that is eradicated by the saw determines the spacing density of the sliders on a wafer. If the size of the saw kerf can be reduced, the sliders can be formed closer together and thus more sliders contained on a wafer, thereby reducing the per-slider cost. The sawing process with its associated large mechanical and frictional forces tearing into the slider material also produces a variety of physical damage, such as chipping, scratching, and cracking of the sliders and delamination of the patterned layers of the read/write heads. Because the sawing process includes significant rubbing it can also cause the accumulation of static electrical charge, which can damage the read/write heads when discharged. Finally, the sawing process leaves sharp comers and edges so that a separate edge blending or rounding step must be performed.
What is needed is a method of cutting wafers into quads, quads into rows, and especially rows into sliders that produces a reduced kerf region to allow closer packing of sliders on a wafer, that reduces physical and electrical damage to the sliders and the read/write heads, and that leaves blended or rounded edges on the disk sides of the sliders.
SUMMARY OF THE INVENTION
The invention is a method for cutting a ceramic wafer to form individual sliders for use in supporting the read/write heads in magnetic recording disk drives. After the wafer has been cut into individual rows, a pulsed laser beam is directed to that surface of the row that will become the disk sides of the sliders (i.e., the sides of the sliders that will face the disks in the disk drive). The laser beam scribes or partially cuts a generally V-shaped trench in the row while simultaneously blending the surface edges adjacent the trench. In the preferred process, the laser is pulsed as the laser spot is moved along a first scan line across the surface of the wafer row to form the trench. The laser spot is then moved in a direction generally perpendicular to the first scan line a distance less than the laser beam diameter, and then pulsed while the laser spot is scanned along a second line generally parallel to the first scan line. This slight offset of the laser beam during the second scan blends the edges of the wafer surface at the trench to remove protrusions formed at those edges by the first laser scan. The laser is then moved to the other side of the first scan line a distance less than the laser beam diameter and a third scan is made to blend the other edge. If it is desired to cut deeper into the wafer row the laser beam can be moved back to the first scan line and one or more subsequent laser scans can be formed to either cut deeper, or to cut completely through the wafer row to completely separate the sliders.
The method of the present invention simultaneously partially cuts the sliders from the wafer row and blends the edges at the disk sides of the sliders, thereby eliminating a subsequent separate edge blending step. The laser cutting process allows more sliders to be formed from a single ceramic wafer since substantially less ceramic material is removed than would be removed if the conventional diamond-tipped sawing process were used.
For a fuller understanding of the nature and advantages of the present invention, reference should be made to the following detailed description taken together with the accompanying figures.
REFERENCES:
patent: 4835361 (1989-05-01), Strom
patent: 5198637 (1993-03-01), Noda et al.
patent: 5739048 (1998-04-01), Kerth et al.
patent: 6049056 (2000-04-01), Balamane et al.
patent: 58-9782 (1983-01-01), None
patent: 61-186185 (1986-08-01), None
patent: 3-64043 (1991-03-01), None
patent: 4-309480 (1992-11-01), None
Lundquist Paul Matthew
Tam Andrew Ching
Berthold Thomas R.
Evans Geoffrey S.
International Business Machines - Corporation
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