# Patent

## Title
Assembly method of carriage assembly of magnetic disk drive

## Abstract

A fabricating technique for a hard disk driver comprises: mounting a bottom plate onto a base having nuts integrally embedded therein by screwing fixing screws into the nuts via the corresponding tapped holes formed in the bottom plate so as to produce a first structure, surface treating the first structure, mounting a top plate having a pair of legs at opposite end portions bent in a L-shape onto the bottom plate by screwing fixing screws into the nuts via respective holes of the legs and corresponding tapped holes formed in the bottom plate so as to produce a second structure, and surface treating the second structure. Surface-treating the first and second structures are performed using an electrodeposit coating process so that dust particles accumulated during fabrication can be easily eliminated and static friction between recording head and recording medium embodied therein can be prevented.

## Background
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. .sctn.119 from an application for Method For Fabricating A Hard Disk Driving Apparatus earlier filed in the Korean Industrial Property Office on 27 Oct. 1994 and assigned Ser. No. 27722/1994.

1. Technical Field

The present invention relates to a method for fabricating a disk drive system of a hard disk, and more particularly to a method for surface-treating respective structural components of a disk drive system.

2. Background Art

In general, a hard disk apparatus of a rotary actuator type for use with a microcomputer, for example, as shown in U.S. Pat. No. 5,369,538 for Rotary Disk Drive Actuator issued to Moe et al., U.S. Pat. No. 5,363,262 for Magnetic Disk Apparatus And Method For Manufacturing The Same issued to Kawakami, and U.S. Pat. No. 5,404,636 for Method Of Assembling A Disk Drive Actuator issued to Stefansky et al., is constructed with a generally, rectangularly shaped base serving as a frame accommodating a plurality of circular disks coaxially mounted in a stack upon a spindle driven by a motor mounted on base to provide a plurality of cylindrical base surfaces that serve as a memory into which binary information may be written and read, an actuator mounted upon base by a pivot such as a threaded fastener to freely rotate about the longitudinal axis of pivot, and a voice coil motor assembly positioned to respond to electrical control signals and thereby arcuately displace a proximal end of actuator. Actuator arm supports, at its distal end, a plurality of electromagnetic transducers commonly known as read/write actuator heads corresponding to the distinct separate cylindrical base surfaces of disks that serves as memories. Typically, the base surfaces of disk are coated with a magnetically sensitive material that responds to fields created by corresponding ones of actuator heads, to enable the actuator heads to either write bits of information at selected locations along tracks formed on the surface of the disk, or to read information from those tracks. Generally, disk continuously rotates in a single direction while voice coil motor assembly acts upon the proximal end of actuator arm to arcuately displace the proximal arm relative to motor and thereby cause the distal ends of actuator arm to radially position heads along corresponding base surface of disk. A cover is then mounted upon the upper surface of base, to enclose disks, actuator and voice coil motor assembly, and to thereby seal the interior of disk drive in order to protect the environment where disks reside from dust and contaminants. Known tape seals such as one disclosed in U.S. Pat. No. 5,270,887 issued to Compact Disk Drive Head Disk Assembly With Conformable Tape Seal issued to Edwards et al. may be used to provide a substantial airtight seal between the base and cover to thereby maintain a desired clean environment within the disk drive.

Actuator heads "fly" over the corresponding base surfaces of disks, and are normally spaced apart from those surfaces by a low flying height, for example, 4.mu.m formed by a cushion of air generated by the rapid rotation of the disks. Voice coil motor assembly drives the proximal end of actuator to move heads to a desired information track of disks. Generally, voice coil motor assembly includes a bottom plate, a top plate, magnets and a current coil fixed to the proximal end of the actuator. The current coil is situated between the bottom plate and the magnet with fixed gaps between them. When a control current flows through the coil, the actuator rotates about the longitudinal axis of pivot by an interaction of magnetic fluxes produced individually by the coil and the magnet. As the actuator heads maintain a low flying height over the disk surface, even small dust particles, such as cracked particles created during fabrication of disk drive including voice coil motor assembly, can interfere with the head/disk interface, causing the heads to "crash" or otherwise interfering with the reading/writing of data onto the disk surface.

Accordingly, it has been necessary to keep the air in the disk drive housing relatively free of dust particles and other contaminants so as to maintain high performance of the disk drive. Conventional method for fabricating voice coil motor assembly requires all components to be surface treated individually with a thin nickel coating. For example, the top and bottom plates are individually coated by a well-known nickel plating process. The magnet is coated by either the nickel plating or an electrodeposit coating process. The base and the cover are individually coated by either electrodeposit coating process or chromate conversion treatment. In addition to the surface-treatment of each individual component of the voice coil motor assembly, cleaning, pretreatment, drying and packaging of each individual components are all necessary prior to the final assembly. Consequently, production cost of the hard disk is increased; moreover, it is difficult to completely eliminate all the dust particles generated during the assembling of all respective components of the voice coil motor assembly. If the dust particles are not completely eliminated, the hard disk is then contaminated, and "crash" or "scratch" often occurs in the actuator heads or the disk surface.

Accordingly, it is therefore an object of the present invention to provide a novel method for assembly of, and a voice coil motor assembly in a hard drive so as to eliminate dust particles.

It is also an object of the present invention to provide a novel method for assembling a voice coil motor assembly in a hard drive in which the cleaning, pretreatment, drying and packaging of each individual component of the voice coil motor assembly can be eliminated.

It is another object of the present invention to provide a method for fabricating a voice coil motor assembly in a disk drive in which static friction between transducer heads and disk surface can be prevented.

According to the aspect of the present invention, the method for assembling a voice coil motor assembly in a disk drive includes the steps of: mounting a bottom plate onto a base having nuts integrally embedded therein by screwing a first plurality of screws into the nuts of the base via the corresponding tapped holes formed in the bottom plate, forming a first structure by attaching a first magnet onto an exterior surface of the bottom plate, treating the surface of the first structure with an electrodeposit coating, forming a second structure by attaching a second magnet onto an interior surface of a top plate having a pair of legs at opposite end portions bent in a L-shape, treating the surface of the second structure with an electrodeposit coating, and mounting the top plate onto the bottom plate by screwing a second plurality of screws into the nuts of the base via respective holes of the legs and corresponding tapped holes formed in the bottom plate.

According another aspect of the present invention, the method for assembling a voice coil motor assembly in a disk drive includes the steps of: affixing a bottom plate onto a base of a housing by adhesive exhibiting conductive characteristics, forming a first structure by attaching a first magnet by adhesive exhibiting conductive characteristics onto an exterior surface of the bottom plate, treating the surface of the first structure using an electrodeposit coating process, forming a second structure by attaching a second magnet by adhesive exhibiting conductive characteristics onto an interior surface of a top plate bent into a U-shape, affixing the top plate to a cover of a housing by adhesive exhibiting conductive characteristics, treating the surface of the second structure using the electrodeposit coating process, and then mounting the top plate attached to the cover onto the bottom plate affixed to the base. The electrodeposit coating is applied on both the first and second structures so as to prevent deterioration of adhesive bonding between the top plate and the cover, and between the bottom plate and the base.

The present invention is more specifically described in the following paragraphs by reference to the drawings attached only by way of example.

A more complete appreciation of the present invention, and many of the attendant advantages thereof, will become readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein:

FIG. 1 is a perspective view illustrating a hard disk drive containing a voice coil motor assembly constructed according to the principles of the present invention;

FIG. 2 is an exploded perspective view showing the way in which top and bottom plates of the voice coil motor assembly may be mounted in the practice of the present invention;

FIGS. 3A, 3B and 3C illustrate how the voice coil motor may be assembled in accordance with one embodiment of the present invention; and

FIG. 4 illustrates how the voice coil motor may be assembled in accordance with another embodiment of the present invention.

Referring now to the drawings and particularly to FIG. 1 which illustrates a hard disk drive of a rotary actuator type showing its cover removed. As shown in FIG. 1, the disk drive has a housing 1 having a substantially rectangular shaped base 3 serving as a frame providing a major interior surface accommodating at least one circular disk 5 coaxially mounted upon a spindle shaft 4 of motor 2 fixed on base 3, an actuator 6 mounted upon pivot shaft 8 so as to freely rotate about the longitudinal axis of pivot 13, a voice coil motor assembly 10 mounted onto base 3 so as to serve as drive mechanism for rotating the actuator 6 when a control current flows through coil 15 by an interaction of magnetic fluxes produced individually by the coil and magnet placed therein. Actuator 6 supports, at its distal end 9, an electromagnetic transducer 7. As disk 5 rotates during operation, transducer 7 reads or writes information on or from the disk in a manner such that it is kept narrowly above the disk surface.

FIG. 2 shows an exploded perspective view of how all individual components of the voice coil motor are assembled in accordance with the principles of the present invention. Bottom plate 12 may be formed from a magnetic material, is mounted on the base 3 having by screwing fixing screws 12b into nuts integrally embedded in base 3. If the bottom plate 12 is not formed from a magnetic material, permanent magnet 12 may be affixed onto bottom plate 13. Top plate 16 having a pair of legs 16b at opposite end portions bent in a L-shape is mounted onto the bottom plate 12 by screwing thread and receiving fasteners such as screws 14 into the receiving fasteners such as, for example, nuts integrally embedded in base 3, via respective holes 14b of legs 16b and corresponding tapped holes 14c formed through the bottom plate 12. Top plate 16 faces the bottom plate 12 at a predetermined distance therefrom in parallel relation while its legs 16b rest on the bottom plate 12. Permanent magnet 17 is fixed to the interior surface of the top plate 16, and also faces the bottom plate 12 at a predetermined distance in parallel relation therefrom.

Referring to FIGS. 3A, 3B and 3C, the novel method for fabricating a voice coil motor assembly in a disk driver performed in accordance with the principles of the present invention is illustrated. As shown in FIG. 3A, bottom plate 12 is mounted onto base 3 having nuts integrally embedded therein by screwing screws 12b into the nuts via the corresponding tapped holes formed through bottom plate 12. Permanent magnet 13 is affixed onto bottom plate 12 by adhesive such as, epoxy exhibiting conductive characteristics, if the bottom plate 12 is not formed from a magnetic material so as to form a first structure. The first structure is subject to surface treatment so as to prevent even small dust particles from accumulating during the mounting of the bottom plate 12. Permanent magnet 17 is then affixed onto an interior surface of top plate 16 having a pair of legs 16b at opposite end portions bent in a L-shape so as to form a second structure. The second structure is also subject to surface treatment so as to eliminate dust particles formed thereon. The top plate 16 having permanent magnet 17 affixed thereon, is then mounted onto the bottom plate 12 by screwing threaded screws 14 into the nuts 14c via respective tapped holes 14b of the legs 16b and corresponding tapped holes 14c formed in the bottom plate 12 as shown in FIG. 3B.

According to the principles of the present invention, if all components of disk drive are to be assembled within a short time, for example, two weeks, and the humidity is normal, standard surface cleaning of the surface of the first and second structures may be sufficient to withstand erosion and eliminate dust particles. If, on the other hand, contact portions between the magnet 13 and bottom plate 12 and the between screws 12b, 14 and the base 3 exhibit conductivity, an electrodeposit coating is applied on the surface of the first and second structures so that dust particles accumulated during fabrication can be easily eliminated and static fiction between recording head and disk can be prevented. Electrodeposit coating may apply on both the interior surface and exterior surface of the top plate 16 having permanent magnet 17 affixed thereon for forming the second structure before top plate 16 is mounted onto bottom plate 12 having permanent magnet 12 affixed thereon. One example for such an application is to dip the entire top plate 16 into an electrodeposit coating bath so that all surface may be fully treated. Alternatively, electrodeposit coating may also apply on the surface of the voice coil motor assembly after the top plate 16 having permanent magnet 17 affixed thereon is mounted onto bottom plate 13 having permanent magnet 12 affixed thereon.

Once the surface of the first and second structures is treated with an electrodeposit coating so as to eliminate dust particles accumulated during fabrication, cover 20 is mounted upon base 3 of the housing so as to enclose disk, actuator and voice coil motor assembly, and to thereby seal the interior of disk drive in order to protect the environment where disks reside from dust and contaminants as shown in FIG. 3C. According to the present invention, since each of the first and second structures is cleaned because of the surface-treatment, even small dust particles accumulated during the mounting of bottom plate 12 and top plate 16 can be eliminated. Moreover, even those dust particles remaining on the structures, are solidly attached onto surface of the structures during the surface-treatment and thus do not interfere with the head/disk interface and do not cause the heads to "crash" or otherwise interfere with the reading/writing of data onto the disk surface as commonly occurs in the conventional art.

Referring now to FIG. 4 which illustrates another embodiment of the voice coil motor assembly according to the present invention. In this alternative embodiment, the voice coil motor assembly has similar circuit components, except that those circuit components are assembled together by adhesive rather than by fasteners such as nuts and bolts as shown in FIGS. 3A-3C. As shown in FIG. 4, the fabrication method follows the steps of: (1) affixing bottom plate 22 onto base 3 by adhesive exhibiting conductive characteristics; (2) attaching a first magnet 23 by the same adhesive therebetween so as to form a first structure; (3) surface-treating the first structure; (4) affixing top plate 26 bent into a U-shape to cover 24 by the same adhesive; (5) attaching a second magnet 27 by the same adhesive therebetween so as to form a second structure; (6) surface-treating the second structure; and (7) mounting the top plate 26 affixed to the cover 24 onto the bottom plate 22 affixed to the base 3. Similar to the first embodiment as shown in FIGS. 3A-3C, the surfaces of the first and second structures are separately treated with an electrodeposit coating process so as to cover the adhesive and to thereby advantageously prevent gas leaking from the adhesive bonding which contribute to the head erosion and contamination inside the disk drive and induce static friction between transducer head and disk. Alternatively, the surface of the first and second structure may be treated with an electrodeposit coating after the first structure is mounted onto the second structure to form the voice coil motor assembly. Accordingly, even if gas is generated due to deterioration of the adhesive bonding, it may not escape the electrodeposited coating and does not contribute to the head erosion and contamination of the disk drive. Moreover, static friction between transducer head and disk can be prevented.

While there have been illustrated and described what are considered to be preferred embodiments of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made, and equivalents may be substituted for elements thereof without departing from the true scope of the present invention. In addition, many modifications may be made to adapt a particular situation to the teaching of the present invention without departing from the central scope thereof. Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out the present invention, but that the present invention includes all embodiments falling within the scope of the appended claims.

## Claims

1. A method for fabricating a voice coil motor assembly in a disk driver, comprising: by screwing a first plurality of screws into the nuts of said base via corresponding tapped holes formed in the bottom plate; surface of said bottom plate; surface of a top plate having legs at opposite end portions bent in a L-shape; and plurality of screws into the nuts of said base via respective holes of the legs and corresponding tapped holes formed in the bottom plate.

2. The method as claimed in claim 1, wherein said protective coating of said first and second structures is provided by an electrodeposit coating process.

3. The method as claimed in claim 1, wherein said first magnet is attached onto the exterior surface of said bottom plate, and said second magnet is attached onto the interior surface of said top plate by adhesive exhibiting conductive characteristics, respectively.

4. A method for fabricating a voice coil motor assembly in a disk drive, comprising: conductive characteristics; exhibiting conductive characteristics onto an exterior surface of said bottom plate; process; adhesive exhibiting conductive characteristics; exhibiting conductive characteristics onto an interior surface of said top plate; coating process; and to the base.

5. The method as claimed in claim 4, wherein the surface of said first and second structures is treated by dipping said first and second structures into an electrodeposit coating bath.

6. The method as claimed in claim 4, wherein the surface of said first and second structures is treated with an electrodeposit coating.

7. A method for fabricating a voice coil motor assembly in a disk drive, comprising: conductive characteristics; exhibiting conductive characteristics onto an exterior surface of said bottom plate; structure; adhesive exhibiting conductive characteristics; exhibiting conductive characteristics onto an interior surface of said top plate; to the base.

8. The method as claimed in claim 7, wherein said protection coating is applied onto said first structure by an electrodeposit coating process.

9. The method as claimed in claim 7, wherein said protection coating is applied onto said second structure by dipping said second structure into an electrodeposit coating bath.

10. A method for fabricating a voice coil motor structure in a disk driver, comprising: by screwing a first plurality of screws into the nuts of said base via corresponding tapped holes formed in the bottom plate; adhesive exhibiting electrically conductive characteristics; pair of legs at opposite end portions bent in a L-shape by adhesive exhibiting electrically conductive characteristics; plurality of screws into the nuts of said base via respective holes of the legs and the corresponding tapped holes formed in the bottom plate to form said voice coil motor structure; and structure.

11. A disk drive fabrication process comprising: having first and second plurality of threaded nuts integrally formed therein, for rotatably supporting a transducer head to record information on a recording medium and to reproduce information from the recording medium; to rotate substantially in a radial direction of the recording medium, said voice coil motor assembly being formed by the steps of: base by screwing a first plurality of screws into said base via corresponding tapped holes formed in said bottom plate; and L-shape and having a second magnet attached thereon, on said bottom plate by screwing a second plurality of screws into said base via respective holes of the legs and the corresponding tapped holes formed in said bottom plate, after opposite surfaces of said bottom plate and said top plate have been treated with a protective coating; and mounting a coil on said actuator between said first and second magnets, for interacting with said magnets to produce magnetic flux enabling said actuator to rotate substantially in the radial direction of the recording medium.

12. The disk drive fabrication process of claim 11, wherein said protective coating is provided by an electrodeposit coating process.

13. The disk drive fabrication process of claim 11, wherein said first magnet is attached onto the exterior surface of said bottom plate, and said second magnet is attached onto the interior surface of said top plate by adhesive exhibiting conductive characteristics, respectively.

14. A disk drive fabrication process comprising: for supporting a transducer head to record information on a recording medium and to read information from the recording medium; to rotate substantially in a radial direction of the recording medium, said voice coil motor assembly being formed by the steps of: base by adhesive exhibiting conductive characteristics; attached thereon, on a cover of a housing by said adhesive; and bottom plate by said adhesive after each of said bottom plate affixed on said base and said top plate affixed on said cover has been treated with a protective coating; and interacting with said magnets to produce magnetic flux enabling said actuator to rotate substantially in the radial direction of the recording medium.

15. The disk drive fabrication process of claim 14, wherein said protective coating is provided by an electrodeposit coating process.