Embodiments of the invention may relate generally to thin film devices and more particularly to an approach to row slicing a set of devices from a larger array of devices.
A hard-disk drive (HDD) is a non-volatile storage device that is housed in a protective enclosure and stores digitally encoded data on at least one circular disk having magnetic surfaces. When an HDD is in operation, each magnetic-recording disk is rapidly rotated by a spindle system. Data is read from and written to a magnetic-recording disk using a read-write head that is positioned over a specific location of a disk by an actuator. A read-write head uses a magnetic field to read data from and write data to the surface of a magnetic-recording disk. A write head makes use of the electricity flowing through a coil, which produces a magnetic field. Electrical pulses are sent to the write head, with different patterns of positive and negative currents. The current in the coil of the write head induces a magnetic field across the gap between the head and the magnetic disk, which in turn magnetizes a small area on the recording medium.
High volume magnetic thin film head slider fabrication involves high precision subtractive machining performed in discrete material removal steps. Slider processing starts with a completed thin film head wafer consisting of 40,000 or more devices, for example, and is completed when all the devices are individuated and meet numerous and stringent specifications. To balance the impact of material removal defects and artifacts on subsequent machining steps, specifications are required to be continuously improved. Of equal importance to improving the quality of material removal is to optimize the capacity of each material removal step in order to minimize capital equipment costs and cycle time.
In a typical first step of removal, a precision machining procedure is performed to individuate rows of devices from a wafer for batch processing, for example, usually an array of over 50 devices. These devices are then processed to final specifications through multiple removal steps, each with increasingly tight specifications. When slicing an array of rows from the wafer, there are limited means for providing cut support. However, cut support while machining directly impacts the quality of precision material removal.
Any approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.
Embodiments of the invention are generally directed toward a process or method for slicing a row from an array of devices, and toward a corresponding slicing tool for slicing a workpiece. A slicing process comprises positioning an array of devices such that a row of the array physically interfaces with a conforming fence, applying a force to the fence sufficient to conform the fence to a mating face of the row, applying a vacuum force to the fence to secure the fence in conformal interfacing position with the row, and then slicing the row from the array. Applying the force to the fence to conform it to the mating face of the row acts to inhibit leakage that might be associated with applying the vacuum force to the fence to secure the fence with the row. Thus, a stronger hold of the row is provided, which can lead to a more precise slicing of the row. One non-limiting potential use of such a process may include the slicing of a row of magnetic read-write head sliders from a wafer array of such devices.
An embodiment of a slicing tool comprises a rotatable support bearing comprising a fence to interface with a workpiece face, where the fence includes a gas channel configured to provide a pressure differential at an outlet port, a housing for the support bearing, a gap between the support bearing and the housing, and a pressure chamber configured to transfer pressurized gas to the channel and whereby gas suffuses into the gap thereby providing an air bearing for the support bearing, which urges the support bearing to rotate to a position such that the fence of the support bearing conforms to the face of the workpiece.
Embodiments discussed in the Summary of Embodiments section are not meant to suggest, describe, or teach all the embodiments discussed herein. Thus, embodiments of the invention may contain additional or different features than those discussed in this section. Furthermore, no limitation, element, property, feature, advantage, attribute, or the like expressed in this section, which is not expressly recited in a claim, limits the scope of any claim in any way.
Embodiments are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:
Approaches to slicing a row from an array of devices are described. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the invention described herein. It will be apparent, however, that the embodiments of the invention described herein may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the embodiments of the invention described herein.
Embodiments may be used in the context of slicing a row of magnetic read-write head sliders from a wafer, such as for use in a hard disk drive (HDD) storage device. Thus, in accordance with an embodiment, a plan view illustrating an HDD 100 is shown in
The HDD 100 further includes an arm 132 attached to the HGA 110, a carriage 134, a voice-coil motor (VCM) that includes an armature 136 including a voice coil 140 attached to the carriage 134 and a stator 144 including a voice-coil magnet (not visible). The armature 136 of the VCM is attached to the carriage 134 and is configured to move the arm 132 and the HGA 110, to access portions of the medium 120, being mounted on a pivot-shaft 148 with an interposed pivot bearing assembly 152. In the case of an HDD having multiple disks, the carriage 134 is called an “E-block,” or comb, because the carriage is arranged to carry a ganged array of arms that gives it the appearance of a comb.
An assembly comprising a head gimbal assembly (e.g., HGA 110) including a flexure to which the head slider is coupled, an actuator arm (e.g., arm 132) and/or load beam to which the flexure is coupled, and an actuator coil (e.g., the VCM) to which the actuator arm is coupled, may be collectively referred to as a head stack assembly (HSA). An HSA may, however, include more or fewer components than those described. For example, an HSA may refer to an assembly that further includes electrical interconnection components, a preamplifier, etc. Generally, an HSA is the assembly configured to move the head slider to access portions of the medium 120 for read and write operations.
With further reference to
Other electronic components, including a disk controller and servo electronics including a digital-signal processor (DSP), provide electrical signals to the drive motor, the voice coil 140 of the VCM and the head 110a of the HGA 110. The electrical signal provided to the drive motor enables the drive motor to spin providing a torque to the spindle 124 which is in turn transmitted to the medium 120 that is affixed to the spindle 124. As a result, the medium 120 spins in a direction 172. The spinning medium 120 creates a cushion of air that acts as an air-bearing on which the air-bearing surface (ABS) of the slider 110b rides so that the slider 110b flies above the surface of the medium 120 without making contact with a thin magnetic-recording layer in which information is recorded. Similarly in an HDD in which a lighter-than-air gas is utilized, such as helium for a non-limiting example, the spinning medium 120 creates a cushion of gas that acts as a gas or fluid bearing on which the slider 110b rides.
The electrical signal provided to the voice coil 140 of the VCM enables the head 110a of the HGA 110 to access a track 176 on which information is recorded. Thus, the armature 136 of the VCM swings through an arc 180, which enables the head 110a of the HGA 110 to access various tracks on the medium 120. Information is stored on the medium 120 in a plurality of radially nested tracks arranged in sectors on the medium 120, such as sector 184. Correspondingly, each track is composed of a plurality of sectored track portions (or “track sector”), for example, sectored track portion 188. Each sectored track portion 188 may be composed of recorded data and a header containing a servo-burst-signal pattern, for example, an ABCD-servo-burst-signal pattern, which is information that identifies the track 176, and error correction code information. In accessing the track 176, the read element of the head 110a of the HGA 110 reads the servo-burst-signal pattern which provides a position-error-signal (PES) to the servo electronics, which controls the electrical signal provided to the voice coil 140 of the VCM, enabling the head 110a to follow the track 176. Upon finding the track 176 and identifying a particular sectored track portion 188, the head 110a either reads data from the track 176 or writes data to the track 176 depending on instructions received by the disk controller from an external agent, for example, a microprocessor of a computer system.
An HDD's electronic architecture comprises numerous electronic components for performing their respective functions for operation of an HDD, such as a hard disk controller (“HDC”), an interface controller, an arm electronics module, a data channel, a motor driver, a servo processor, buffer memory, etc. Two or more of such components may be combined on a single integrated circuit board referred to as a “system on a chip” (“SOC”). Several, if not all, of such electronic components are typically arranged on a printed circuit board that is coupled to the bottom side of an HDD, such as to HDD housing 168.
References herein to a hard disk drive, such as HDD 100 illustrated and described in reference to
Slider processing starts with a completed thin film head wafer consisting of 40,000 or more devices, and is completed when all the devices are individuated and meet numerous and stringent specifications. The individual devices ultimately become read-write heads. As mentioned, high volume magnetic thin film head slider fabrication involves high precision subtractive machining performed in discrete material removal steps. Precise control of the read head and write head dimensions and of the alignment of the read and write portions of the head relative to each other are critical components of the read-write head fabrication process, in order to achieve optimum yield, performance and stability.
In the first step of removal, a precision machining procedure is performed to individuate rows of devices for batch processing, usually an array of over 50 devices. These devices are then processed to final specifications through multiple removal steps, each with increasingly tight specifications. To balance the impact of material removal defects or artifacts on the following machining steps, read-write transducer parameters are continuously improved as the removal processes proceed. Of equal importance to improving the quality of material removal is to optimize the capacity of each material removal step in order to minimize capital equipment costs and cycle time.
When slicing an array of rows, there are limited means of providing cut support, where the cut support while machining directly impacts the quality of precision material removal. One approach to providing cut support involves the adhesive bonding of a wafer to a fixture or sacrificial substrate. This approach may provide adequate cut support as well as high volume capacity. However, issues with using a bonding agent and a sacrificial material remain, such as with the solvents, heat and tooling typically involved with removing bonding adhesives from the wafer, the significant cycle time associated with bonding and de-bonding wafers, and the devices being machined are inherently prone to corrosion which may be promoted by corrosive agents within the adhesive.
To avoid the foregoing undesirable conditions associated with machining bonded parts, another approach involves using vacuum as a medium of cut support, which provides cut support without using adhesives or solvents, and without realizing the resulting increase in cycle time. However, even with use of vacuum cut support, the precision of cuts is not necessarily as high quality as desired.
One approach to row slicing (or “bar slicing” or “row-bar slicing”) involves seating row arrays against a vacuum fence. Vacuum is actuated and provides cut support below the part, and at the interface in front of the row to be removed. The interface of concern is the air bearing surface (ABS) faces of the sliders and the vacuum fence. At this interface, the quality of uninterrupted vacuum directly impacts the precision and quality of the cut. Cutting forces, coolant flow, and the mating of the ABS to the vacuum fence represent significant challenges. The incoming angle of the row to be cut directly impacts the interface between the wafer/ABS and the vacuum fence.
Using a fence made of conforming material that seals the wafer against the fence, while providing conformality, may not provide sufficient datum rigidity and may therefore result in loss of cutting precision. On the other hand, using a rigid fence for a datum does not accommodate the incoming angle of the row, whereby any gaps in the ABS-fence interface is likely to result in a loss of vacuum and, consequently, a loss of cut support. However, is has been common practice to provide a rigid datum and accept the loss of vacuum during precision machining that results from the workpiece-fence surfaces not precisely mating.
A typical head slider fabrication process flow may include the following: a wafer (e.g., wafer 202 of
At block 302 an array of devices is positioned such that a row physically interfaces with a slicing tool conforming fence (i.e., a conforming fence of a slicing tool) that is configured to conformally interface with a mating face of the row. For example, array 410 (
At block 304, a force is applied to the conforming fence where the force is sufficient to substantially conform the conforming fence to the mating face of the row. The manner in which the conforming fence is made to conform to the mating face of the row may vary from implementation to implementation. For non-limiting examples, a pressurized gas force or a spring force may be applied to the conforming fence in order to position the fence such that it conforms to the mating face of the row. Multiple embodiments are described in more detail herein, but practice of the method of
While the force applied generally conforms the fence to the row, the term “substantially” is used because of the variation, or deviation from the plane, associated with the mating face of the row. That is, the face of the row is not usually perfectly planar or flat as there is effectively always some deviation from the plane at various locations across the face due to the fabrication and slicing processes (e.g., perhaps 1° or more), and in the context of the micro-scale of such devices (e.g., a 180 micron height row). Thus, at such a micro-scale it is not feasible to completely, perfectly or precisely conform due to this micro-variation, but substantially conforming eliminates a significant portion of mismatch or non-conformity between the face of the fence and the face of the row, and consequently provides for a better, less leaky vacuum at block 306.
At block 306 a vacuum (force) is applied to the conforming fence to secure the conforming fence in a conformal interfacing position with the row. For example, a vacuum may be pulled on conforming fence 404 (
At block 308 the row is sliced from the array of devices. Thus, because of the relatively tight securing of the row resulting from the conformal fence-row interface, even the already sliced portion of the row is better secured than with non-conformal fence approaches, thereby facilitating a more precise slicing or cutting operation than if the sliced portion of the row was less secured. Effectively, the blade 402 (
With reference first to
Returning to
Because the air bearing support 601 is now being supported or held up by an actual air bearing generated in the gap 608, near-frictionless rotational movement 610 of the air bearing support 601, and its constituent pressurized fence 602, is now possible. Thus, by the nature of the near-frictionless air bearing supported state of the support 601, in conjunction with the interfacial interaction between the array 410 and the pressurized fence 602 of the air bearing support 601, the air bearing support 601 is urged to rotate such that the pressurized fence is forced to substantially conform with the mating surface of the row of the array of devices (i.e., array 410). Stated otherwise, urging the air bearing support 601 to rotate effectively causes the fence to self-align in conformance with the mating surface of the row. Thus, the mating surface or face of the row can reference to, i.e., evenly make contact with, the fence 602, hence resulting in robust support of the row before and during subsequent slicing.
With reference to
With further reference to
At block 508 the row is sliced from the array of devices, e.g., from the array 410 (
Conforming fence 1000 is configured to interface with and provide support to a workpiece, such a wafer array of devices, during slicing. Conforming fence 1000 comprises two or more segments 1002a, 1002b-1002n, where the number of segments may vary from implementation to implementation. Each of the segments 1002a-1002n is configured to move independently of the other segments. For example, small gaps may be implemented between adjacent segments 1002a-1002n such that the segments are able to slide freely relative to each other.
Conforming fence 1000 further comprises a force mechanism configured to apply a force sufficient to conform each of the segments 1002a-1002n to a respective mating portion of a face 411 of array 410. For example, the force applied to each of the segments 1002a, 1002b-1002n may be a respective spring force 1004a, 1004b-1004n that operates to conform each corresponding segment 1002a, 1002b-1002n to the face 411.
Conforming fence 1000 further comprises a vacuum actuation mechanism configured to secure each of the segments 1002a-1002n in place in a conformal position with each respective mating portion of the face 411 of the array 410. For example, the vacuum force 1006 applied to each of the segments 1002a, 1002b-1002n to effectively couple the segments 1002a-1002n together to lock them in place against the face 411 of the array 410 may be implemented as a pressure chamber internal to a portion of each segment, whereby creating a vacuum in the pressure chamber effectively locks in place each of the segments 1002a-1002n so that each segment is inhibited from further movement under the influence of the respective spring force 1004a-1004n.
In the foregoing description, embodiments of the invention have been described with reference to numerous specific details that may vary from implementation to implementation. Therefore, various modifications and changes may be made thereto without departing from the broader spirit and scope of the embodiments. Thus, the sole and exclusive indicator of what is the invention, and is intended by the applicants to be the invention, is the set of claims that issue from this application, in the specific form in which such claims issue, including any subsequent correction. Any definitions expressly set forth herein for terms contained in such claims shall govern the meaning of such terms as used in the claims. Hence, no limitation, element, property, feature, advantage or attribute that is not expressly recited in a claim should limit the scope of such claim in any way. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.
In addition, in this description certain process steps may be set forth in a particular order, and alphabetic and alphanumeric labels may be used to identify certain steps. Unless specifically stated in the description, embodiments are not necessarily limited to any particular order of carrying out such steps. In particular, the labels are used merely for convenient identification of steps, and are not intended to specify or require a particular order of carrying out such steps.