Mobile storage device

Abstract

Disclosed is a mobile storage device that combines high storage capacity and performance with low power consumption and portable operation. The key enabling component of the mobile storage device is an integrated base ceramic substrate upon which a plurality of spiral conductors, magnetoresistive sensors and interconnect conductors have been fabricated by a semiconductor process, and upon which electronic integrated circuits have been assembled. A dual-rotor spindle assembly, a multi-arm actuator assembly and a ceramic housing are assembled with the integrated base forming a chamber that is hermetically sealed and can been pressured with a low viscosity gas at below ambient pressures.

Description

BACKGROUND

[0002] 1. Field of Invention

[0003] This invention relates to Data Storage Systems, specifically those using magnetic recording on rigid disks.

[0004] 2. Description of Prior Art

[0005] Hard Disk Drives (HDDs) are based on magnetic recording technology which has been increasing the amount of data stored on a single 2.5-inch disk from today's 40 GB to an expected 180 GB in two to four years. However the manufacturing of HDDs has not kept pace with these advances and remains, for the most part, a labor intensive assembly operation. This approach requires expensive tooling and specialized capital equipment expenditures each time a new product is introduced. In addition, high power consumption and high performance are synonymous with HDDs and limits their use in emerging applications requiring mobile high speed digital storage and playback. One of the major contributors, to high power consumption, is the viscous drag of the surrounding air on the magnetic disks during high speed angular rotation. This drag is directly proportional to the air density and its viscosity which surrounds the disks and leads to high temperatures within the HDD. In addition, the surrounding air can be humid and condensation can occur on the surface of the disks during operation.

OBJECTS AND ADVANTAGES

[0006] Advances in disk storage capacities coupled with the high I/O performance of multi-actuators and high rotational speed disk drives, has created an opportunity to provide these features in a Mobile Storage Device (MSD) that can be either battery or bus powered. Accordingly, several objects and advantages of my invention are:

[0007] to provide a Mobile Storage Device that is battery and bus powered.

[0008] to provide an Integrated Base that integrates all key electrical components on a high strength ceramic substrate witch was manufactured by processes and equipment common to the semiconductor industry.

[0009] to provide a Mobile Storage Device totally enclosed in a hermetically sealed chamber.

[0010] to provide a robust Mobile Storage Device that can rotate at high rotational speeds with low power consumption.

[0011] to provide a Mobile Storage Device with multiple low inertia Actuator Arms for fast access times with minimum power.

[0012] to provide a variable speed Spindle Motor

[0013] Further objects and advantages of my invention will become apparent from a consideration of the drawings and ensuing description.

DRAWING FIGURES

[0014] FIG. 1 a -1c shows front, profile and back views of the Integrated Base, 100.

[0015] FIG. 2 a -2c shows the top, front, and bottom views of the disk, rotor and spindle assemblies.

[0016] FIG. 3 a shows the top, front, and bottom views of the Integrated Arm and FIG. 3b shows the top and front views of the multi-gap Actuator Assembly.

[0017] FIG. 4 shows the top, front and profile views of the Housing.

[0018] FIG. 5 a -5b shows the top and front view of the components and assemblies of the Mobile Storage Device.

[0019] FIG. 6 is various views of the Mobile Storage Device with the Lithium Polymer Battery and cable assembled.

[0020] FIG. 7 a -7c is cross sectional views of two, three and four arm Mobile Storage Devices.

[0021] FIG. 8 a -8c shows the relationship between the permanent magnets, stator coils and biased Mr Sensors and the resulting electrical waveforms.

DESCRIPTION—FIGS. 1 to 7

[0022] Integrated Base 100

[0023] FIG. 1 a -1c shows the front, profile and back views of the Integrated Base (IB), 100, a key and enabling component of the Mobile Storage Device. The IB consists of two parts; a bottom 10 and a top 20 and was manufactured on ceramic substrate 5 using the following materials and processes.

[0024] 1: In the preferred embodiment, ceramic substrate 5 is manufactured with an Yttria-partially Stabilized Zirconia (YTZP) material whose salient properties are given in Table 1. This material exhibits excellent strength and fracture toughness and is able to absorb the high energy of impact without shattering or deforming.

TABLE 1
Yttria-Partially Stabilized Zirconia (YTZP)1
Density:                        6.02 (grams/cm3)
Flexural Strength               1,300 (MPa)
Fracture Toughness              13 (MPa*m1/2)
Compressive Strength            2,500 (MPa)
Coefficient of Linear Expansion 10.3 (10−6/° C.)
Thermal Conductivity            2.2 (W/m*K)

[0025] 1-As per CoorsTek, a manufacturer of Technical Ceramics

[0026] 2: Front to back via holes are laser machined in substrate 5 and filled with low resistivity copper. The substrate is now lapped and polished, on both surfaces, for flatness and smoothness.

[0027] 3: IC interconnect traces 15, stator coil 21 and Mr Stripes 22 interconnects 26, and stator coils 11 and Mr Stripes 12 interconnects 16 are fabricated by sputtering 2-4 microns of copper on the front and back surfaces of substrate 5. Photoresist is applied to both surfaces, exposed with photo masks defining the interconnect traces 15, 26 and 16, and developed. The substrate is sputter etched, or ion milled, to remove all copper not covered with photoresist.

[0028] 4: The biased Mr elements, 12 and 22, are fabricated by sputtering a magneto resistive material, such as 80-20 Nickel-Iron (Ni—Fe), followed by a film of Copper (Cu). Photoresist is applied, exposed, and developed and then the substrate is sputter etched, or ion milled, to removing the copper-Ni—Fe material not covered with photoresist.

[0029] 5: A 5-6 micron film of aluminum oxide (Al2O3) is sputter deposited on both surfaces of substrate 5 and then double sided lapped and polished with a process know as CMP (Chemical Mechanical Planarization).

[0030] 6: Via's back to interconnect traces 15, 16 and 26 are fabricated by applying photoresist to both surfaces of substrate 5, expose to define via location, develop, and etch Al2O3.

[0031] 7: The fabrication of the spindle motor stator coils 11 and 21 starts with the sputtering of a copper seed layer followed by the application of an ultra-thick photoresist (20-100 microns) on the front surface of substrate 5. The substrate is exposed with a photo mask defining the spiral coil pattern, developed, and copper is electroplated into the openings with the thickness of the copper equal to the photoresist thickness. The photoresist is stripped and the copper seed layer is removed by etching. These resists, such as the Shipley BRP100 or the Clariant AZ PLP 100XT, can achieve aspect ratios of 10 to 1 (height/width) with near vertical walls and optimized for the fabrication of copper electroplated conductors.

[0032] 8: Mount “bumped” IC's 70, 71 and 72 and the mini-connector 75 using a solder re-flow operation.

[0033] 9: An YTPZ Zirconia spindle motor shaft 77 is bonded to substrate 5 in a fixture to ensure its extension and perpendicularity to substrate 5.

[0034] 10: A precision ceramic washer, 92, and a spring type washer 91 are bonded to substrate 5 as shown in FIGS. 1a and 1b. Washer 92 establishes the spindle motor air gap and washer 91 will pre-load the spindle motor bearings.

[0035] Dual Rotor Spindle Assembly 200

[0036] FIG. 2 a is the top, front and bottom views of the Magnetic Disk, 210, consisting of a magnetic film deposited on a glass substrate. Magnetic Disk 210 is available from a variety of manufactures in high volume and at reasonable cost.

[0037] FIG. 2 b is the top, front and bottom view of the top 215 and bottom 216 rotor assemblies consisting of thin cylindrical permanent magnets of Neodymium-Iron-Boron (NdFeB) 211 mounted on rings 212 of 50-50 Nickel-Iron (Ni—Fe), a soft magnetic material having high saturation magnetization. The Ni—Fe ring acts as a rigid holder of the NdFeB permanent magnet, and a low reluctance magnetic flux return. The rotor assemblies are ground and lapped flat and then magnetized perpendicular to their face.

[0038] FIG. 2 c is the top, front and bottom view of the assembled Spindle Assembly 200. It was assembled as follows:

[0039] Bearing Sleeve 250 consists of two precision bearings installed in an alumina (Al2O3) ceramic sleeve. The bearings were installed with their races flush with the ends of the ceramic sleeve.

[0040] Magnetic recording disks 210 are precisely located and bonded to bearing sleeve 250, using pre-forms of UW curable glass filled adhesives.

[0041] Rotor Assemblies 215 and 216 are located and bonded to magnetic disks 210.

[0042] Actuator Assembly 300

[0043] FIG. 3 a is the top, front and bottom view of the Integrated Arm Assembly 305.

[0044] FIG. 3 b is the top and front view of the Actuator Assembly 300 consisting of two Integrated Arms 305 mounted to multi-gap Voice Coil Motor 310 using precision spacers 311.

[0045] Housing 400

[0046] FIG. 4 shows the top, front and profile view of the injection molded YTPZ Zirconia ceramic Housing, 400. The top and bottom surfaces have been ground and polished parallel and flat and are separated by a dimension controlled to within 0.0001 inches.

[0047] Assembly of the Mobile Storage Device 500

[0048] FIG. 5 a is the top view and FIG. 5b is the front view of the assemblies and components, of the Mobile Storage Device 500, which can be assembled as follows.

[0049] Dual-Rotor Spindle Assembly 200 is assembled to bottom Integrated Base 10 over the spindle motor shaft 77 with the inner race of the spindle motors bearings resting on precision spacer 92.

[0050] Actuator assembly 300 is placed in position on the bottom Integrated Base 10 and secured with an UW curable epoxy adhesive.

[0051] Housing 400 is bonded to bottom Integrated Base 10 with a continuous film so as to form an air-tight seal.

[0052] The top Integrated Base 20 is now bonded to Housing 400 with a continuous film so as to form an air-tight seal.

[0053] The chamber formed by the top Integrated Base 20, the bottom Integrated Base 10 and the Housing 400 can now be evacuated and refilled with a low viscosity gas at a pressure below one atmosphere.

[0054] Mobile Storage Device 500

[0055] FIG. 6 shows the attachment of the Lithium Polymer battery 625 and a electrical cable connecting interconnects 26 to the motor control IC on the bottom Integrated Base 10.

[0056] Multi-Integrated Arm Mobile Storage Devices

[0057] FIG. 7 a -7c shows the side view of a two, three and four Integrated Arms Actuator Assemblies and the addition of magnetic disks 210 to spindle assembly 200. The Integrated Arms can be operated independently or can be mechanically secured together and operated as a single unit.

OPERATION—FIG. 8

[0058] The NdFeB magnets 211 have been magnetized, perpendicular to their faces, into 6 equal segments of alternating polarity as shown in FIG. 8a. This creates a magnetic intensity in the air gap of +B and −B. With the Mr Sensors biased to the magnetic intensity −B, the resistance of the Mr Stripe will change when the magnetic intensity in the air gap is +B, and the resistance will remain the same when the magnetic intensity in the air gap is −B.

[0059] The relationship between the spiral stator coils 11, Mr Sensors 12 and NdFeB magnet 211 is shown in FIG. 8b. The start of the stator coil 11 is labeled S1 and the spiral conductor goes along radial lines inward in region 1 and along radial lines outward in region 2. Region 1 is connected to region 2 along circular arc conductors until it terminates in the center of the spiral coil. In the preferred embodiment, the angular widths of regions 1 and 2 are 30° and they are separated by an angular width of 30°. A mirror image of this spiral coil is located as shown in FIG. 8b and the following table.

	Spiral Coil 1		Spiral Coil 2
	Start	End	Start	End
Region 1	0	30	240	270
Region 2	60	90	180	210

[0060] A duplicate of spiral stator coil 11 and Mr Stripes 12 are made on the top Integrated Base 20. The top NdFeB magnet is offset 30° from the bottom magnet as shown in FIG. 8b.

[0061] The first Mr Sensor is located 120° from the start conductor in region 1 and the second Mr Sensor is located 30° from the first. When the bottom NdFeB magnet rotates CCW relative to spiral stator coil 11, the outputs of the Mr Stripes, labeled Mr1 and Mr2, will be as shown in the bottom waveforms of FIG. 8c with the outputs reflecting the polarity and intensity of the magnetic field in the air gap. The logical signals Mr1 and Mr2 are used to derive the current gating waveforms I+ and I−. During I+, a positive current from S1 to S2 produces a positive torque and during I−, a negative current produces a positive torque.

[0062] With the top NdFeB magnet offset by 30° from the bottom magnet, the top waveforms will be identical to the bottom waveforms but offset by 30°.

[0063] The combined I+ and I− waveforms, from the bottom and top Mr Sensors, allow current, and therefore torque, to be applied to the stator coils on a near continuous basis.

CONCLUSIONS, RAMIFICATIONS, AND SCOPE

[0064] Accordingly, the reader will see that the Mobile Storage Device of this invention, has shown and demonstrated;

[0065] a Mobile Storage Device having high performance and capacity with low power consumption.

[0066] a Mobile Storage Device which is battery and bus powered

[0067] a Mobile Storage Device where the key and enabling components are manufactured using processes and equipment common to the semiconductor industry.

[0068] a variable speed dual-rotor spindle motor with near continuous torque control.

[0069] a Mobile Storage Device with multiple actuator arms and disks.

[0070] A Mobile Storage Device with the actuator and spindle assemblies enclosed in a hermetically sealed chamber with the electronics.

[0071] While my above description contains many specifications, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of one preferred embodiment thereof Many other variations are possible. For example the Integrated Base could be made from other materials, use other semiconductor processes, have other electrical components and have different shapes and sizes. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents.

Claims

1. A mobile storage device comprising: a top and bottom integrated base including a thin ceramic substrate having a plurality of spiral conductor patterns, a plurality of magnetoresistive sensors, and a conductor interconnect pattern for IC, connector and flex cable attachment; a shaft; a spindle assembly wherein each spindle assembly is mounted to and rotates about said shaft and each spindle assembly includes a least one magnetic disk and at least one permanent magnet rotor and said magnetic disks and said permanent magnets are assembled in combination with a ceramic bearing sleeve; an actuator assembly; a ceramic housing; wherein the top and bottom integrated base assemblies are assembled and bonded to said ceramic housing forming a hermetically sealed chamber containing the spindle and actuator assemblies; wherein said permanent magnets interact with said spiral conductor patterns to provide torque to the spindle assembly.