HK1087831B - Apparatus for grounding a magnetic recording head - Google Patents

Description

Apparatus for grounding magnetic recording head

This application claims priority from U.S. application No. 60/417665, filed on 11/10/2002.

Technical Field

The present invention relates to a magnetic hard disk drive. More particularly, the present invention relates to a method and apparatus for grounding a magnetic recording head that avoids the use of conductive adhesives.

Background

Disk drives for data recording use magnetic recording heads to write and read data on recording disks. The recording heads are built on a substrate, called a wafer, made of a conductive material, such as AlTiC, by the same process as that used for semiconductor devices. The gold pads on the outer surface of the recording head are electrically connected to the recording device through internal electrical paths created during wafer-level processing. The wafer is then diced into rectangular blocks so that there is a separate recording head, called a slider, on each block with the substrate attached. Then, the slider is mounted on the suspension. The assembly is referred to as a head gimbal assembly, or HGA. The slider is then bonded to the suspension using an adhesive, which includes a conductive adhesive to form an electrical connection between the substrate and the stainless steel component of the suspension. Additional electrical connections are made between the gold pads on the recording head and the metal traces on the suspension using methods including ultrasonic bonding or solder bonding. Finally, the HGA is assembled into a hard disk drive device such that the suspension traces are connected to other electrical components, typically a preamplifier, and the stainless steel portion of the suspension is connected to the electrical ground of the drive.

There are generally two types of HGAs-wired and wireless. The wired HGA is one in which a separate lead is connected between the flex circuit of the HAS and the read/write head. The wireless HGA is one in which conductive traces are integrated with a flexure (flexure) and provide electrical conductance between the flexure of the HAS and the read/write head of the slider. In the prior art, there are typically two types of wireless suspensions. In the first type, such as Trace Suspension Assemblies (TSA) and integrated circuit suspensions (CIS), traces are built up by a removal process (e.g., an etching operation) performed on a stainless steel flexure or by an addition process (e.g., a plating or deposition process) such that an insulating layer is between the trace and the flexure. After the traces are placed in the appropriate locations, the flexure can then be welded to the rest of the suspension. In the second type, such as Flexible Suspension Assemblies (FSAs) and flexible beams on suspensions (FOS), the traces are built on an insulating layer and then covered with another insulating layer to form a flex circuit. The circuit can then be attached to the suspension with an adhesive. Alternatively, an additional metal layer, referred to as a ground plane, may be attached to the flex circuit prior to attachment to the suspension. In FSA, the flex beam is integrated with the load beam and the mounting plate along with integrated traces for making the connections.

As shown in FIG. 1, a head gimbal assembly 40 typically provides multiple degrees of freedom to the slider, such as vertical spacing, pitch angle, and roll angle, which describe the flying height of the slider. As shown in FIG. 1, suspension 74 holds HGA40 on a moving disk 76 (having an edge) and moves in the direction indicated by arrow 80. In operation of the disk drive shown in FIG. 1, the actuator 72 moves the HGA across various diameters (e.g., Inner Diameter (ID), Middle Diameter (MD), and Outer Diameter (OD)) of the disk 760 over the arc 78.

A typical preamplifier is connected to the head to provide write current to the write head and receive current from the read head. Preamplifiers exist in assemblies commonly referred to as Actuator Flexible Preamplification Assemblies (AFPAs). The preamplifier is typically soldered to the flex circuit. The flex circuit is provided with regions: HGA traces would be connected to this region to enable the circuitry to connect the preamplifiers to the read and write elements of the head.

The suspension provides two functions: mechanically supporting and providing an electrical connection between the head and the preamplifier. Instead of using physical wires to connect the head to the preamplifier, metal traces on the suspension are commonly used.

The method of electrically grounding the recording head substrate using a conductive adhesive has a number of disadvantages. Most importantly, the resistance of the conductive adhesive is unreliable and difficult to control. The resistance can be very high and can vary widely from part to part during the manufacturing process. In addition, it is difficult to control the flatness of the slider mounted to the HGA, which is another critical parameter. In addition, the assembly process requires many processes in order to apply and cure the conductive adhesive in the HGA, thereby increasing the cost and cycle time of the manufacturing process.

The use of a stainless steel suspension as the electrical ground connection between the HGA and the electrical ground provided in the disk drive may also have drawbacks. The electrical resistance of the stainless steel suspension may vary considerably between such components. If the stainless steel resistance is high, there will be a very unreliable connection to other metal structures in the ground path (e.g., actuator).

In view of the foregoing, there is a need for an improved method and apparatus for grounding a read/write head/slider that overcomes the disadvantages of these known systems.

Disclosure of Invention

The invention provides an apparatus for grounding a magnetic recording head.

According to one aspect of the present invention, a suspension includes:

a substrate;

a dielectric layer disposed on the substrate;

a plurality of metal traces coupled to the dielectric layer that are coupled to read/write circuitry on a slider member coupled to the suspension; and

an individual trace segment to be electrically coupled to the slider component, the individual trace segment coupled to the substrate through an opening in the dielectric layer.

According to another aspect of the present invention, a suspension includes:

a flexible suspension assembly comprising:

a ground plane;

a dielectric layer;

a plurality of metal traces to be coupled to read/write circuitry in the slider component; and

an individual trace segment to be electrically coupled to the slider component, the individual trace segment being electrically coupled to the ground plane through an opening in the dielectric layer.

According to still another aspect of the present invention, a disk drive includes:

a head suspension assembly comprising:

a slider including read/write circuitry;

a plurality of traces coupled to pads on the slider, the slider coupled with the read/write circuitry;

an individual trace segment coupled to the slider;

a dielectric layer; and

a metal substrate such that the individual trace segments are electrically coupled to the metal substrate.

According to still another aspect of the present invention, a slider includes:

a slider body comprising a substrate, circuitry to write and read data on a recording disk, at least one bond pad to transmit read/write signals, and a separate ground bond pad electrically coupled to the substrate, wherein the slider body comprises a leading edge, a trailing edge, and a side edge, the separate ground bond pad being located at the leading edge or the side edge of the slider.

Drawings

FIG. 1 illustrates an actuator arm in a hard disk drive device configured to read from and write to a magnetic hard disk as known in the prior art;

FIG. 2 shows a gold ball bonding structure used in an embodiment of the present invention;

FIG. 3 is a perspective view showing a portion of a suspension with the addition of solder pads and traces for grounding the read/write head/slider in accordance with a first embodiment of the present invention;

FIG. 4 is a perspective view showing a portion of a suspension with the addition of bond pads and traces for grounding the read/write head/slider in accordance with a second embodiment of the present invention;

FIG. 5 is a perspective view showing a portion of a suspension with the addition of solder pads and traces for grounding the read/write head/slider in accordance with a second embodiment of the present invention;

FIG. 6 is a perspective view of a suspension with the addition of a segmented trace for grounding the slider component in accordance with one embodiment of the present invention;

FIG. 7 is a cross-sectional view of the suspension showing the electrical connection between the trace segment and the stainless steel substrate of the suspension according to the first embodiment of the present invention;

FIG. 8 is a cross-sectional view of a suspension illustrating an electrical connection between a trace segment and a stainless steel substrate of the suspension according to a second embodiment of the present invention;

fig. 9 is a cross-sectional view showing a suspension according to the present invention for making an electrical connection between a trace segment and a stainless steel substrate and connecting the substrate to a ground terminal of a preamplifier.

Detailed Description

Referring to fig. 2, a typical ball bond configuration is shown. As described above, the slider 5 includes electrical components and components that facilitate reading data from and writing data to a storage medium, such as a rotating hard disk. To facilitate the connection of the electrical components of the read/write "head" to other components in the disk drive, an external bonding pad 13 is provided on the outside of the slider. Similarly, the suspension also includes electrical components coupled to the read and write components of the slider. Typically, these electrical components include metal traces incorporated into the suspension 11, or separate flex circuits connected to the suspension. In either case, the solder pads 9 are typically provided on the surface of the suspension 11. A conductive material, such as gold balls or solder balls, is deposited on the bonding pads 13 of the slider 5 and the bonding pads 9 of the suspension 11. In the present embodiment, gold balls 7 are used in a conventional manner. Similarly, the bonding pads 9 and 13 are also made of gold.

According to one embodiment of the present invention, a more reliable and well controlled grounding of the substrate of the recording head 5 is achieved by an electrical connection between an additional ground trace on the suspension 11 and an additional grounding gold pad on the recording head/slider that is electrically connected to the substrate through internal conductive vias built into the recording head/slider at the wafer processing level. The same method used to connect other gold solder pads and suspension traces can be used to connect grounding gold solder pads and suspension grounding traces, which can be more reliable and well controlled than using a conductive adhesive. The suspension ground trace can then be electrically connected to the electrical ground of the hard disk drive, again using the same or similar method of connecting the other traces to other electrical components in the disk drive, typically a preamplifier.

Referring to fig. 3, a first embodiment of the present invention is shown. In this embodiment, disposing the slider 201 at the trailing edge of the slider includes read and write electrical components. Bond pads 209 and 211 are disposed on the slider for electrically connecting the read and write electrical components to the electrical components on the suspension. In this embodiment, the electrical components of the suspension include four conductive traces 205, 207 coupled to bond pads 215, 217, respectively, for read/write signals. In typical suspensions known in the art, the conductive traces 205, 207 may be incorporated into the suspension 221 or may be separately produced in a flex circuit or similar device coupled to the suspension. In addition, the traces may be electrically connected to electrical components of the disk drive (e.g., a preamplifier, not specifically shown in FIG. 3) for controlling the reading and writing of data from and to the storage medium.

According to this embodiment of the invention, the slider 201 is coupled to the tongue 203 of the suspension in a conventional manner (e.g., using an electrically insulating adhesive). A separate bonding pad 213 is disposed on the outer surface of the slider 201. For example, the solder pads may be coupled with electrical components within the slider 201 that are to be coupled to an electrical ground. A separate grounding pad 220 is disposed on the suspension along with the ground trace 219 to provide a conductive path to an electrically grounded component in the disk drive device (e.g., through the preamplifier). After the slider 201 is attached to the tongue 203, the bond pads 209, 211, 213 of the slider may be electrically connected to the bond pads 217, 215, 220 of the suspension by, for example, a gold ball bond configuration as shown in FIG. 2. Other methods of electrical connection may be used including ultrasonic welding and soldering.

Figure 4 shows an alternative embodiment of the invention. In this embodiment, a separate ground pad 225 is disposed on the side surface of the slider, rather than on the trailing edge side of the slider 201. As with the embodiment of fig. 3, the ground pad 225 is electrically coupled to components within the slider 201 that are to be electrically connected to ground. Similarly, a separate ground pad 227 is disposed on the suspension 221 along with the conductive trace 223 to electrically connect the solder pad 225 to electrical ground within the hard disk drive device. As with the embodiment of FIG. 3, gold ball bonding, as shown in FIG. 2, may be used to electrically connect the bonding pads 209, 211, 225 of the slider 201 to the bonding pads 217, 215, 227 of the suspension.

Many benefits are obtained from the embodiments of the invention shown thus far. First, the ground resistance can be made very low and consistent. Second, slider flatness control will be improved. In addition, the HGA assembly process can be greatly simplified. For example, the conductive adhesive application process may be eliminated during the manufacturing process. The foot paste placement process may also be simplified because the use of conductive epoxy may not be required.

The above-described invention is not limited to these embodiments. For example, the separate ground pad may be placed on the slider at a location other than that shown in fig. 3 and 4. For example, the shim may be placed on the leading edge of the slider. Further, conductors other than traces incorporated into either side of the suspension may be used, including separate wires. In one embodiment of fig. 3 and 4, a separate shim is attached to the base of the slider so that it can be grounded. The separate shim may be coupled with other components in the slider as desired. Also, the separate spacer may be coupled with other components in the disk drive device. When the read/write circuits and the separate pads are at the trailing edge of the slider (as in FIG. 3), electrical connections from the pads to the slider substrate can be isolated from the read/write circuits in the slider during wafer fabrication processing using any of a variety of known separation techniques. Furthermore, the embodiments of fig. 3 and 4 are for illustrative purposes only and they are not necessarily drawn to scale.

Referring to fig. 5, an additional embodiment of the present invention is shown. As described above, it may be sought to provide an electrical ground connection between the slider and the outside of the ground trace of the slider by the conductive adhesive bonding the slider to the HGA. In the embodiment of fig. 5, the ground pad 251 on the suspension 252 is coupled to a ground plane 254 within the body of the suspension. In this embodiment, the suspension 252 includes a metal plane that may be connected to ground (e.g., via a preamplifier). The connection between the ground pad 251 to the ground plane 254 may be accomplished by any of a variety of known methods (e.g., gold plated via connection 253).

Referring to fig. 6-9, additional embodiments of the present invention are shown, such as those relating to the application of segmented traces for grounding a slider.

Referring to fig. 6, a suspension 261 is shown with an integral flexure 262 and an attached slider component 263. In the present embodiment, the slider part 263 includes four pads 265a-d that provide read and write signals to the head part 268 of the slider 263 in a conventional manner. These pads 265a-d are electrically connected to other pads on the flexure 262, which in turn are connected to read/write traces 267a-d connected to a preamplifier 269. In this embodiment, the suspension includes a stainless steel substrate 271 and a dielectric layer 273 that helps electrically isolate traces 267a-d from the stainless steel substrate 271.

According to one embodiment of the invention, segmented traces are provided to electrically couple the slider to ground. In this embodiment, the slider includes a ground pad 273 as described above. When the slider 263 is coupled to the flexure 262, the slider's ground pad 273 may be electrically coupled to a corresponding ground pad 274 on the flexure. The first segment 275 of the trace is electrically connected to a ground pad 274. In addition, the second segment 276 of the trace is electrically connected to ground (e.g., the ground 275 of the preamplifier). The first and second length traces 275, 276 may be electrically coupled through a stainless steel base 271 of the suspension 261 as described below.

Referring to fig. 7, a first embodiment of a method for electrically connecting a trace segment to a stainless steel substrate of a suspension is shown. In the embodiment of FIG. 7, the traces for electrically coupling the preamplifier to the slider are constructed by a subtractive process such as a Trace Suspension Assembly (TSA). In TSA, the suspension comprises at least three layers: a top conductor layer 283 (e.g., made of copper), an intermediate dielectric layer 282, and a base layer 286 (e.g., made of stainless steel). The material may then be removed (e.g., by etching) to form trace conductors (e.g., in the form shown in fig. 6). According to one embodiment of the present invention, an opening 280 is created through the copper layer 283 and the interlayer dielectric 282 and/or an edge 284 is created to expose the stainless steel substrate 286. A conductive material 281 (e.g., gold, solder) may then be deposited into the opening 280 or at the edge 284 to create an electrical connection between the copper traces 283 and the stainless steel substrate. Referring back to FIG. 6, such electrical connection will occur at the first and second trace segments to create an electrical connection between the slider (e.g., ground pad 273) and ground 275.

Referring to fig. 8, a second embodiment for electrically connecting a trace segment to a stainless steel substrate is shown. In the present embodiment, the traces are generated by an addition process performed in, for example, an integrated circuit suspension (CIS). In such an addition process, the dielectric layer 291 is deposited onto the stainless steel substrate 292, and then the conductive traces 293 are deposited on top of the dielectric layer 291. In this embodiment, an opening 290 is created in the dielectric layer 291. For example, after the dielectric layer 291 is deposited onto the stainless steel base 292, the opening 290 may be formed into the dielectric layer by an etching process. Alternatively, the dielectric layer 291 may be deposited in such a way as to form an opening to the substrate 292 during the deposition process. After the opening is created, a conductive trace 293 is deposited into the opening in order to create an electrical connection (e.g., between one of the trace segments 275, 276 and the stainless steel substrate 271 in fig. 6).

Referring to fig. 9, a third embodiment for electrically connecting trace segments to a stainless steel substrate is shown. In this embodiment, the copper traces are formed as part of a Flexible Suspension Assembly (FSA). Referring to fig. 9, the FSA includes a copper ground plane 301, a dielectric layer 303, and metal traces including trace segments 305. Once formed, the FSA may then be attached to the suspension 315, which is made entirely of stainless steel. The slider 307 can then be attached to the flexure of the suspension and electrically coupled to the copper trace segments through a separate ground pad 308 on the surface of the slider 307. In the present embodiment, an opening 310 is formed in the dielectric layer 303 to enable the trace segment 305 to make electrical contact with the copper ground plane 301. As with the embodiment shown in fig. 7, electrical connections may be made by providing a separate, conductive material (e.g., gold or solder balls) in the openings to connect the trace segments to the ground plane. Also, using the embodiment of fig. 8, a copper trace segment 305 may be formed across the opening to connect to a copper ground plane. While a separate trace segment may be provided to couple the ground terminal of the preamplifier 317 to the stainless steel substrate 315, in the present embodiment, the copper ground plane 301 may be directly coupled to the ground terminal 316.

Note that although only one or two trace segments are provided in the above embodiments, the present invention is not limited thereto. Multiple trace segments may be used between the slider and ground. Further, the slider has been shown to be connected to the ground of the preamplifier using trace segments, but other components may be electrically connected using such trace segments. For example, trace segments may be used to connect the slider to other ground components in the disk drive. In addition, the trace segments may also be used to connect circuitry within the slider to other components in the disk drive.

Although several embodiments are specifically illustrated and described herein, it will be appreciated that modifications and variations of the present invention are covered by the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention.

Claims (20)

1. A suspension, comprising:

a substrate;

a dielectric layer disposed on the substrate;

a plurality of metal traces coupled to the dielectric layer that are coupled to read/write circuitry on a slider member coupled to the suspension; and

an individual trace segment to be electrically coupled to the slider component, the individual trace segment coupled to the substrate through an opening in the dielectric layer.

2. The suspension of claim 1 wherein the substrate is made of stainless steel.

3. The suspension of claim 2, further comprising:

a second trace segment electrically coupled to the substrate.

4. The suspension of claim 3 wherein the second trace is to be coupled to an electrical component in a disk drive.

5. The suspension of claim 3 wherein the second trace is to be coupled to a ground terminal of a preamplifier.

6. The suspension of claim 5, further comprising:

a slider including read/write circuitry electrically coupled to the plurality of traces and trace segments on the suspension.

7. The suspension of claim 1 wherein the individual trace segments are coupled to the substrate across an edge of the dielectric layer.

8. The suspension of claim 7 wherein the substrate is made of stainless steel.

9. The suspension of claim 8, further comprising:

a second trace segment electrically coupled to the substrate.

10. The suspension of claim 9 wherein the second trace segment is to be coupled to a ground terminal of a preamplifier.

11. The suspension of claim 4, further comprising:

a slider including read/write circuitry electrically coupled to the plurality of traces and trace segments on the suspension.

12. A suspension, comprising:

a flexible suspension assembly comprising:

a ground plane;

a dielectric layer;

a plurality of metal traces to be coupled to read/write circuitry in the slider component; and

an individual trace segment to be electrically coupled to the slider component, the individual trace segment being electrically coupled to the ground plane through an opening in the dielectric layer.

13. The suspension of claim 12 wherein the individual trace segments are to be electrically coupled to a grounding pad on the slider component.

14. The suspension of claim 13, further comprising:

a substrate coupled to the flexible suspension assembly.

15. The suspension of claim 14 wherein the ground plane is to be coupled to ground on a preamplifier component in a disk drive.

16. The suspension of claim 14, further comprising:

a slider including read/write circuitry electrically coupled to the plurality of traces and the individual trace segments on the flexible suspension assembly.

17. A disk drive, comprising:

a head suspension assembly comprising:

a slider including read/write circuitry;

a plurality of traces coupled to pads on the slider, the slider coupled with the read/write circuitry;

an individual trace segment coupled to the slider;

a dielectric layer; and

a metal substrate such that the individual trace segments are electrically coupled to the metal substrate.

The disk drive of claim 17, further comprising:

a preamplifier including a ground terminal electrically coupled to the metal substrate of the head suspension assembly.

The disk drive of claim 18 wherein said head suspension assembly further comprises:

a second trace segment coupled between a ground terminal of the preamplifier and the metal substrate of the head suspension assembly.

20. The disk drive of claim 17 wherein the head suspension assembly further comprises a ground plane located between the metal substrate and the dielectric layer, wherein the ground plane is electrically coupled to a ground terminal on the preamplifier.

21. A slider, comprising:

a slider body comprising a substrate, circuitry to write and read data on a recording disk, at least one bond pad to transmit read/write signals, and a separate ground bond pad electrically coupled to the substrate, wherein the slider body comprises a leading edge, a trailing edge, and a side edge, the separate ground bond pad being located at the leading edge or the side edge of the slider.

22. The slider of claim 21 wherein said electrical connections between said separate ground pads and said substrate are electrically isolated from other circuitry in the slider.

The slider of claim 21 wherein the electrical connection is between a separate ground pad and a component within the slider.