Patent Application
20070236836
Embodiments in accordance with the present invention relate to a magnetic head slider intended to realize a high recording density for a magnetic disk drive. More particularly, the present invention is concerned with a magnetic head slider having the capability to adjust the distance between a magnetic disk and a magnetic head.
Referring to
The magnetic head slider 1 is attached to the blade spring-like load beam 15 and is moved toward the surface of a magnetic disk by the load beam 15. The magnetic head slider 1 performs a seek in the radial direction of the magnetic disk 10, together with the load beam 15, by means of a voice coil motor 16, whereby recording or reproducing is performed all over the surface of the magnetic disk. When the magnetic disk drive is stopped or a Read or Write instruction is not issued for a certain period of time, the magnetic head slider 1 withdraws from above the magnetic disk 10 to the top of a ramp 14. Herein, the illustrated magnetic disk drive includes a loading/unloading mechanism. Even in a contact start/stop type magnetic disk drive in which when the disk drive is stopped, the magnetic head slider 1 stands by in a specific area on the magnetic disk 10, the present invention would also prove advantageous.
The air bearing surface 5 may be microscopically stepped through such a process of ion milling or etching (stepped bearing). When the air bearing surface 5 is opposed to a disk that is not shown, air pressure is generated on the air bearing surface so that the air bearing surface will fill the role of an air bearing which bears a load imposed on the back. In the drawing, the steps are exaggerated.
As mentioned above, the air bearing surface 5 is stepped and segmented into three kinds of surfaces that are substantially parallel to one another. Namely, the three kinds of surfaces include rail surfaces 6 that come closest to a disk, shallow-groove surfaces 7 that are stepped bearing surfaces and are located by a value ranging from approximately 100 nm to 200 nm more deeply than the rail surfaces 6 are, and a deep-groove surface 8 located by approximately 1 μm more deeply than the rail surfaces 6 are. An airflow derived from the rotation of a disk advances from the shallow-groove surfaces 7 on the air inflow end surface 11 side of the air bearing surface, which serve as a stepped bearing, into the rail surfaces 6 The airflow is compressed due to the narrowed channel. This results in positive air pressure. On the other hand, when an airflow advances from the rail surfaces 6 and shallow-groove surfaces 7 to the deep-groove surface 8, negative air pressure occurs due to the enlarged channel.
The magnetic head slider 1 is designed to fly in a posture causing the flying height of the air inflow end surface 11 side thereof to get larger than the flying height of the air outflow end surface 12 side thereof. Consequently, the flying pad (rail surface) 6 near the outflow end approaches a disk most closely. Near the outflow end, the rail surface 6 projects relative to the surrounding shallow-groove surface 7 and deep-groove surface 8. Unless the slider in the pitching or rolling posture tilts to a degree exceeding a certain limit, the rail surface 6 approaches the disk most closely. The write element 2 and read element 3 are formed in the portion of the rail surface 6 belonging to the thin-film head 1b. The shape of the stepped bearing is designed so that a load imposed by the load beam and the positive or negative air pressure generated on the air bearing surface 5 will be well-balanced and so that the distance from the write element 2 and read element 3 to the disk will be retained at an appropriate value equal to or smaller than about 10 nm.
Herein, a description has been made of the magnetic head slider having the two-step stepped bearing whose air bearing surface 5 is composed of three kinds of surfaces 6, 7, and 8 that are substantially parallel to one another. The present invention will prove equally advantageous even when applied to a magnetic head slider having a three or more-step stepped bearing composed of four or more kinds of parallel surfaces.
In one embodiment, the write element 2 includes a lower magnetic pole 21, an upper magnetic pole 23 that forms a magnetic gap 22 on the side of the air bearing surface and has the rear part thereof magnetically coupled to the lower magnetic pole 21, and a coil 25 formed between the lower magnetic pole 21 and upper magnetic pole 23 with an interlayer insulating layer 24 among them. In one embodiment, the read element 3 includes a lower shield 31, a gap layer 32, a magnetoresistive element 33 formed in the gap layer 32, and an upper shield 34. In some embodiments, the magnetoresistive element 33 is a giant magnetoresistive (GMR) element or a tunneling magnetoresistive (TMR) element. In one aspect, the heater 4 is realized with a thin-film resistor made of a permalloy and is disposed above (near) the read element 3.
In efforts to maximize a change in a flying height caused by heat dissipated from the heater while minimizing a change in the flying height caused by heat dissipation derived from a recording current, the order of forming the write element 2 and read element 3 in an embodiment of the present embodiment is the reverse of the order in which those of a conventional magnetic head are formed. A difference of the embodiment shown in
The AlTiC substrate 1a is superior in thermal conduction compared with other materials such as alumina used to form the magnetic head, and absorbs or disperses a large amount of heat. When the write element 2 is disposed closer to the AlTiC substrate 1a than the one included in a conventional magnetic head is, heat dissipated due to a recording current near the write element 2 is quickly absorbed by the substrate 1a. Thermal projection derived from the recording current can be reduced compared with thermal projection of the conventional magnetic head. Moreover, when the heater 4 is disposed farther away from the AlTiC substrate 1a than it is in the conventional magnetic head, heat dissipated from the heater is prevented from escaping into the substrate 1a. The thermal projection per a unit amount of heat dissipated from the heater can be increased compared with that of the conventional magnetic head.
Specifically, the adiabatic layer 9 fills the role of amplifying the advantage provided by forming the write and read elements in reverse order from the order in which those included in the conventional head structure are formed. When the write and read elements are formed in conventional order, that is, when the read element 3 is first formed on the AlTiC substrate 1a and the write element 2 is formed on the read element 3, even if the adiabatic layer 9 is interposed between the write element 2 and read element 3 (and heater 4), no advantage is won. On the contrary, heat dissipated due to a recording current is increased, but the projection caused by heat dissipated from the heater is decreased. Examples of a material exhibiting low thermal conductivity include silicon dioxide and a resin.
As shown in
Incidentally, the position of the heater 4 is shown in
Next, a method of forming the thin-film magnetic head 1b on a wafer according to an embodiment of the present invention will be described below. First, an under insulating layer 53 made of alumina or the like is formed on the wafer. Thereafter, the lower magnetic pole 21 of the write element 2 is formed on the under insulating layer 53, and the magnetic gap film 22 made of alumina or the like and the upper magnetic pole 23 of the write element 2 are formed. Moreover, the coil 25 through which a current for causing the upper magnetic pole 23 to induce a magnetic field flows, a recording lead line led out of the coil 25, and the insulating film 24 encircling the coil 25 are formed. The lower magnetic pole 21 and upper magnetic pole 23 are magnetically interconnected in a back gap (deep end).
Thereafter, the lower shield 31 is formed via the insulating layer 50 made of alumina or the like, and the (lower) gap layer 32 made of alumina or the like is formed. Furthermore, the magnetoresistive element 33 that is a major part of the read element 2 and a pair of electrodes (not shown) for use in drawing out a magnetic signal from the magnetoresistive element 33 are formed. Thereafter, the (upper) gap layer 32 made of alumina or the like and the upper shield 34 are formed. Furthermore, the insulating layer 50 made of alumina or the like is formed.
Thereafter, the heater 4 realized with a metallic thin-film resistor and a lead line (not shown) over which a current flows into the heater 4 are formed. For example, a thin line whose material is a permalloy, whose thickness is about 0.5 μm, and whose width is about 4.5 μm is laid tortuously in an area having a depth of about 60 μm and a width of about 60 μm, and the space in the area is filled with alumina. This results in a resistance of approximately 50Ω.
Thereafter, a protective insulating layer 52 made of alumina or the like and intended to protect and isolate the foregoing elements is formed to cover all of the layered elements. Finally, a terminal (not shown) of the write element 2 via which a current externally flows into the coil 25, a terminal (not shown) of the read element 3 via which a magnetic signal is transmitted externally, and a terminal (not shown) of the heater 4 via which a current externally flows into the heater 4 are formed.
In the case of the second embodiment shown in
Next, a process during which individual magnetic head sliders 1 are cut out of a wafer and a process during which the magnetic head slider is mounted in a magnetic disk drive according to embodiments of the present invention will be described below. After multiple thin-film heads 1b are formed simultaneously on the wafer, the wafer is diced into bar-like blocks. Thereafter, the cut surfaces of the blocks are polished in order to form air bearing surfaces, and then cleansed. Thereafter, a carbon protective film of several nanometers thick is formed on the air bearing surfaces for fear the air bearing surfaces may wear out due to short-time and light contact with a disk or in order to prevent the thin-film elements on the air bearing surfaces from corroding. Thereafter, the rail surfaces 6, shallow-groove surfaces 7, and deep-groove surface 8 are formed on the air bearing surfaces in order to stabilize the sliders. Each of the bar-like blocks is cut into the individual magnetic head sliders 1, and then cleansed again. Thus, the magnetic head sliders 1 are completed. Thereafter, the magnetic head sliders 1 are bonded to a gimbal that is part of a magnetic head supporting mechanism. Wiring, assembling, and cleansing are then performed. Finally, the assembly is mounted in a magnetic disk drive. Incidentally, as a magnetic recording method, either a longitudinal recording method or a vertical recording method may be adopted.
Next, a method of adjusting the flying height of the magnetic head slider in accordance with embodiments of present invention will be described below. A procedure of adjusting the flying height is broadly divided into three steps of adjustments, that is, adjustment during designing, adjustment during testing at a factory prior to delivery, and adjustment at the time of use. During designing, a magnetic head slider is designed so that when the magnetic head slider travels during continuous writing with the environmental temperature set to a maximum predictive value and the air pressure set to a minimum predictive value, the uncertainty in the travel will be rated at a lower limit and the magnetic head slider will come into contact with a magnetic disk. In other words, the designing is identical to conventional designing of a slider unaccompanied with adjustment of the flying height.
In the case of a magnetic disk drive incorporated in handheld equipment, the magnetic disk drive is subjected to a large variance in the environmental temperature. In the case of a magnetic disk drive incorporated in a server, heat dissipated from magnetic poles during continuous writing brings about thermal projection of a slider and the flying height of the slider decreases very largely. Thus, the conditions for designing vary depending on equipment to which the magnetic disk drive is adapted.
During testing at a factory prior to delivery, the flying height of each magnetic head slider is tested and stored in a memory. A flying height adjustment value is proportional to supplied power. Therefore, the supplied power is first set to zero and then gradually increased. When the contact of the slider with a disk is sensed, the supplied power at that time and the proportionality coefficient between the flying height adjustment value and supplied power are used to calculate the flying height of the magnetic head slider. Methods of sensing the contact include a method of monitoring an off-track signal (position error signal) signifying that an off-track incident has occurred because the magnetic head slider is microscopically turned on a pivot due to contact frictional force. Incidentally, not only a variance in the flying height among sliders but also differences among zones such as differences among internal, middle, and circumferential zones of a magnetic disk and a difference in the flying height between recording and reproducing may be stored in the memory. In this case, the precision in adjusting the flying height can be improved.
At the time of use, in principle, when a Read or Write instruction is received from a client such as a computer, power proportional to the flying height of a selected active magnetic head slider is supplied to the magnetic head slider alone. No power is supplied to an idle magnetic head slider. An amount of power to be supplied to the active magnetic head slider is decreased or increased according to a proportionality coefficient between a flying height adjustment value and supplied power. That is, when continuous writing proceeds or the environmental temperature is high, the amount of power to be supplied to the active magnetic head slider is decreased. When the environmental temperature is low, the amount of power to be supplied to the active magnetic head slider is increased. Information on the environmental temperature is acquired from a temperature element accompanying a magnetic disk drive.
The procedure of testing the flying height of each slider at a factory prior to delivery may be omitted. An alternative method according to an embodiment of the present invention will be described below. A target value is determined for a value indicating recording/reproducing performance such as an error rate or an overwriting frequency. While a heater-conduction current value is increased, the recording/reproducing performance is measured. If the target recording/reproducing performance is attained with a current value smaller than a limit heater-conduction current value, the current value is adopted as a current value set for the head slider. If the current value reaches the limit heater-conduction current value before the target recording/reproducing performance is attained, the product is regarded as defective and sent to a disassembling and reassembling line.
As long as a nominal value of and a variance in an original gap between a flying head and a disk, a nominal value of and a variance in a difference in environmental temperature, and a nominal value of and a variance in a difference in a flying height between recording and reproducing are statistically known, a current value can be determined so that it will permit satisfactory recording/reproducing performance while suppressing the possibility of a magnetic head slider and a magnetic disk coming into contact with each other to the greatest possible extent.
As mentioned above, according to embodiments of the present invention, two demands, that is, a demand for increasing a change in a flying height caused by heat dissipated from a heater and a demand for decreasing a change in the flying height caused by heat dissipation derived from a recording current can be met simultaneously. Consequently, low flying of a magnetic head slider and a high recording density for a magnetic disk drive can be accomplished.
While the present invention has been described with reference to specific embodiments, those skilled in the art will appreciate that different embodiments may also be used. Thus, although the present invention has been described with respect to specific embodiments, it will be appreciated that the present invention is intended to cover all modifications and equivalents within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-105048 | Apr 2006 | JP | national |
