Patent Application
20070025023
The present invention relates to a magnetic disk drive and, more particularly, to a magnetic head slider capable of both suppressing the decrease of its flying height when used at high altitude or low pressure environments and reducing its flying height sensitivity on manufacturing process tolerance.
Achieving higher areal magnetic recording density of magnetic disk drive requires an extremely small and constant spacing between the air bearing slider, which carries the recording element, and the magnetic disk. At the same time, physical contact between the slider and disk must be minimized under a growing demanding variety of operational and environmental conditions. The move to smaller and smaller disk drives has placed increasing demands on power consumption, shock performance, and disk storage capacity. One of the key contributors to achieving these demanding requirements has been the reduction of slider form factor. The reduction of slider form factor can significantly improve the slider's mechanical performances and greatly reduce manufacturing cost. It is very necessary to suppress the reduction of flying height as effectively as possible when the magnetic disk drive is used at high altitude and to decrease flying height sensitivity on manufacturing process tolerances of the smaller and smaller slider.
Generally, the flying height of the slider decreases at high altitude because the mean free path of the air serving as a working fluid for the slider increases at high altitude. The reduction of the flying height is undesirable from the viewpoint of the reliability of the magnetic disk drive because the reduction of the flying height increases the possibility of the slider coming into contact with the magnetic disk. It is particularly desirable for a magnetic disk drive using a 2.5 in and 1.8 in and micro-drive and built in a portable information processing device that is often used at high altitude to prevent the change of the flying height of the slider with the increase of altitude, i.e., with the drop of the atmospheric pressure.
The miniaturization of the slider and the reduction of the diameter of the disk have progressively advanced with the miniaturization of the magnetic disk drive. Since a miniaturized slider has a small area and the circumferential speed of a small-diameter magnetic disk is low, negative pressure produced by the miniaturized slider is low; consequently, suppression of the reduction of the flying height at high altitude by those known prior art techniques has become progressively difficult.
A technique for suppressing the reduction of the flying height of the slider with the increase of the altitude is disclosed in U.S. patent application Ser. No. 11/104,998, filed Apr. 12, 2005 (Patent Document 1). According to patent document 1, the reduction of the flying height at high altitude can be effectively suppressed by the slider design with two longitudinal, separate carbon islands of a predetermined height h formed on the inlet rails.
Another technique for suppressing the reduction of the flying height of the slider with the increase of the altitude is disclosed in JP-A No. 2000-57724 (Patent Document 2). According to Patent document 2, the reduction of the flying height at high altitude can be effectively suppressed by optimizing the ratio between the depth of a step bearing surface and the depth of a negative-pressure groove.
Known magnetic head sliders similar in construction to a magnetic head slider according to the present invention are disclosed in JP-A Nos. 6-203514, 8-102164, 11-25629, 2003-151233, 2001-250215 and 2000-260015, and PCT patent Publication No. WO2003/515869. All those magnetic head sliders used a rail having a stepped surface or provided with a pad on air inlet side to reduce adhesion and friction between the slider and magnetic disk when the slider comes into contact with the magnetic disk.
A way to increase recording density in which a magnetic disk drive records data without losing the reliability of the magnetic disk drive is to reduce flying height across the entire surface of a magnetic disk and to suppress the reduction of the flying height at high altitude.
The miniaturization of the slider and the reduction of the diameter of the disk have progressively advanced with the miniaturization of the magnetic disk drive. Since a miniaturization of the slider has a small area and the circumferential speed of a small-diameter magnetic disk is low, negative pressure that can be produced by the miniaturized slider is low. Therefore, suppression of the reduction of the flying height at high altitude by those known techniques has become progressively difficult. Suppression of the reduction of the flying height of a small slider with 0.85 mm in overall length and 0.7 mm in overall width generally called Femto and below form factor slider at high altitude is difficult and further improvement of a small slider is desired.
The present invention has been made in view of such circumstances and it is a feature of the present invention to provide a magnetic head slider capable of minimizing the reduction of its flying height at high altitude and the lower sensitivity on manufacturing process tolerance.
According to one aspect of the present invention, there is provided a magnetic head slider comprising: a length less than or equal to 0.85 mm, a width less than or equal to 0.7 mm, and a thickness less than or equal to 0.23 mm, an air inlet end, an air outlet end and an air bearing surface wherein the air bearing surface includes a plurality of inlet rails respectively having inlet rail surface, a step bearing surface extending at a predetermined first depth from a reference plane including the inlet and the outlet rail surfaces, a negative surface extending in a plane at a predetermined second depth greater than the first depth from the reference plane, and longitudinal carbon islands of a predetermined height formed on the inlet rails, and an outlet rail having an outlet rail surface flush with the inlet rail surfaces and holding a magnetic R/W head wherein the step bearing surface extends at a predetermined first depth from a reference plane, and wherein the air bearing surface further includes two or more stepped leading air flow surfaces and rising wall profiles.
According to another aspect of the present invention, there is provided a magnetic head slider comprising: a length less than or equal to 0.85 mm, a width less than or equal to 0.7 mm, and a thickness less than or equal to 0.23 mm, an air inlet end, an air outlet end and an air bearing surface wherein the air bearing surface includes a plurality of inlet rails respectively having inlet rail surface, a step bearing surface extending at a predetermined first depth from a reference plane including the inlet and the outlet rail surfaces, a negative surface extending in a plane at a predetermined second depth greater than the first depth from the reference plane, and longitudinal carbon islands of a predetermined height formed on the inlet rails, and an outlet rail having an outlet rail surface flush with the inlet rail surfaces and holding a magnetic R/W head wherein the step bearing surface extends at a predetermined first depth from a reference plane; and wherein the air bearing surface further includes two or more stepped leading air flow surfaces and rising wall profiles; and wherein a load point is located to the point between the air inlet and the center of the magnetic head slider.
According to the present invention, the reduction of the flying height of the magnetic head slider at high altitude can be prevented, and the sensitivity of the flying height on the manufacturing process tolerance can be reduced and thereby the reliability of a magnetic disk drive can be improved.
A magnetic head slider in a first embodiment according to the present invention and a magnetic disk drive provided with this magnetic head slider will described with reference to the accompanying drawings.
Referring to FIGS. 1 to 4, the slider in the first embodiment has an air inlet end 1, an air outlet end 2 and an air bearing surface 3. The air bearing surface 3 includes an inlet step bearing surface 4, inlet rails 5 and 6 respectively having an inlet rail surfaces, an outlet rail 7 having an outlet rail surface and holding a magnetic head 8, two outlet step bearing surfaces 9 and 19, three rising wall profiles 15a, 15b and 15c, a negative-pressure groove 10, and island 11 and 12 formed on the respective inlet rails 5 and 6.
The inlet rail surfaces of the inlet 5 and 6 and the outlet rail surface of the outlet rail 7 are substantially flush with each other and included in a reference plane. Air 20 that flows through a space between a slider and a magnetic disk 22 produces an aerodynamic pressure to cause the slider to fly over the magnetic disk 22. Thus, the inlet rail surfaces 5 and 6 and the outlet rail surface of the outlet rail 7 serve as positive-pressure rail surfaces.
The inlet step bearing surface 4 and the outlet step bearing surface 9 are substantially flush with each other and included in a plane including the inlet rail surface of the rails 5 and 6 and the outlet rail surface of the outlet rail 7. Air 20 passes through the air inlet end 1 into the space between the slider and the magnetic disk 22, then flows along the inlet step bearing surface 4 and the outlet step bearing surfaces 9 and 19. The aerodynamic pressure of air 20 is increased by rising surface 13, 14, 15a, 15b and 15c. Air 20 of an increased aerodynamic pressure flows along the inlet rail surfaces of the inlet rails 5 and 6 and the outlet rail surfaces of the outlet rail 7.
The aerodynamic pressure of air 20 flowing along the inlet rail surfaces of the inlet rails 5 and 6 and reaching the islands 11 and 12 is further increased to a high aerodynamic pressure sufficient to lift up the slider by the second rising surfaces 17 and 18, i.e., the front surfaces of the island 11 and 12. The height of the second rising surfaces 17 and 18 of the islands 11 and 12 from the inlet rail surfaces of the inlet rails 5 and 6 is on the order of 20 nm. The islands 11 and 12 need to have certain length in the flowing direction of air 20, i.e., along the length of the slider, to produce a high aerodynamic pressure by the islands 11 and 12. Such a high aerodynamic pressure, namely, an aerodynamic lift, can be produced by the island 11 and 12 having the second rising surfaces 17 and 18 of such a very low height.
The stepped air flow surfaces 9 and 19 and rising wall profiles 15a, 15b and 15c are the foremost feature of the present embodiment. The first rising surfaces 13 and 14 of the inlet rails 5 and 6 produce aerodynamic pressure 30 and 31 to lift up the slider, and the second rising surfaces 17 and 18 of islands 11 and 12 increase the aerodynamic pressures to higher aerodynamic pressures 32 and 33. The first rising profile 15c produces the aerodynamic pressure of the airflow, the aerodynamic pressure is increased while the air flows through the rising wall profiles 15b and 15c, and produces the aerodynamic pressure 34b and 34a at outlet rail 7.
The length of the stepped surfaces 9 and 19 necessary for producing a high positive pressure is about 50 μm or longer, preferably about 100 μm or longer, and the stepped surface 19 is wider than stepped surface 9. In this embodiment, the length of the island 11 and 12 is about 100 μm.
Since the arrangement of the rising surfaces at two steps is effective in producing a high aerodynamic lift, the sizes of the inlet rails 5 and 6 and the outlet 7 can be reduced, therefore the negative pressure area is increased.
The inlet rail surfaces of the inlet rails 5 and 6 and the outlet rail surfaces of the outlet rail 7 that serve in producing the aerodynamic pressure are positive-pressure rail surfaces. Since the area of the rail surfaces of the slider of the present embodiment necessary for producing a predetermined aerodynamic lift can be reduced, the reduction of the flying height at high altitude can be minimized, which will be described later.
The depth 16 of the negative-pressure groove 10 from the plane including the inlet step bearing surface 4 is on the order of about 800 nm. The depth of the negative-pressure groove 10 from the reference plane including the inlet rail surfaces of the inlet rails 5 and 6 is on the order of about 1 μm.
The depth of the stepped surface 19 from the plane including the outlet step bearing surface 9 is on the order of about 300 nm. The depth of stepped surface 9 from the reference plane including the inlet rail surfaces of the outlet rail 7 is on the order of about 200 nm.
The slider in the first embodiment is the so-called Femto slider with 0.85 mm in length 0.7 mm in width and 0.23 mm in thickness. Generally, the area of the negative-pressure groove 10 decreases with the decrease of the area of the slider, negative pressure that can be produced by the slider decreases with the decrease of the area of the slider and, consequently, the reduction of the flying height at high altitude increases.
At present, the magnetic disk drive has been progressively miniaturized and magnetic disks of smaller diameters that are rotated at low rotational speeds have been used. Consequently, negative pressure that can be produced by the slider has been progressively decreased. These matters are factors that increase the reduction of flying height at high altitude.
As mentioned above, the present embodiment achieves the minimization of the reduction of the flying height at high altitude successively because the area of the rails of the slider in the first embodiment necessary for producing a predetermined aerodynamic lift can be reduced.
The effect of the first embodiment will be concretely described. Air 20 causes the slider to fly over the disk 22 in an inclined position such that the flying height of the air inlet end 1 is higher than that of the air outlet end 2. Consequently, the flying height 23 of the outlet rail surface of the outlet rail holding the magnetic head 8 is the lowest.
If the flying height 24 of the back end of the island 11 and the flying height 25 of the back end of the island 12 is lower than the flying height 23 of the outlet rail surface of the outlet rail 7, the islands 11 and 12 contact with the disk 22. If the islands 11 and 12 contact with the disk 22, the slider vibrates significantly and, in the worst case, the slider would crash. Therefore, the islands 11 and 12 of the slider must be designed such that the slider flies in a proper position and the flying heights 24 and 25 never decrease less than the flying height 23.
As illustrated in
Flying height profiles of the sliders in Comparative example 1 shown in
As mentioned above, the step surface 19, 9 and rising wall profiles 15a, 15b and 15c can increase the air bearing stiffness in translation and pitch direction in the trailing pad due to increasing the pressure gradient. The increase of air bearing stiffness also reduces its sensitivity on the manufacturing process tolerance.
An additional step surface and relative rising wall profile is in the first embodiment compared to the prior sliders; consequently, an additional process is done in the process of manufacturing, so that this process tolerance effect on slider flying height should be evaluated.
A load point where a suspension load 21 is applied to the slider in the first embodiment is set to the point between the air inlet end 1 and the center of the slider, and corresponds to the opposite side of the islands 11 and 12. When the aerodynamic pressures 32 and 33 acting on the islands 11 and 12 decrease at high altitude, a moment Mp tending to decrease the flying height of the air inlet end 1 acts on the slider to suppress the decrease of the flying height 23 of the air outlet end 2.
The slider of the foregoing embodiments capable of reducing the reduction of flying height at high altitude improves the reliability of the magnetic head drive. The effect of the slider of the present invention is particularly significant when the slider of the present invention is applied to a magnetic disk drive provided with small magnetic disks smaller than 2.5-inch magnetic disks.
It is to be understood that the above description is intended to be illustrative and not restrictive. Many embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims alone with their full scope of equivalents.
