# Patent

## Title
Low resistance ground joints for dual stage actuation disk drive suspensions

## Abstract

Stable, low resistance conductive adhesive ground connections between motor contacts and a gold-plated contact area on a stainless steel component of a dual stage actuated suspension. The stainless steel component can be a baseplate, load beam, hinge, motor plate, add-on feature or flexure.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of U.S. patent application Ser. No. 13/114,212 , filed May 24, 2011, now U.S. Pat. No. 8,885,299, issued Nov. 11, 2014, which claims the benefit under 35 U.S.C. 119 of Provisional Application No. 61/396,239 , filed May 24, 2010 , which are incorporated herein by reference in their entirety for all purposes.


TECHNICAL FIELD
The present invention relates to suspensions for disk drives. In particular, the invention is a dual stage actuation (DSA) suspension and method of manufacture.
BACKGROUND OF THE INVENTION
Dual stage actuation (DSA) disk drive head suspensions are generally known and commercially available. By way of example, one embodiment of a DSA head suspension 10 is shown in FIGS. 1A and 1B. The illustrated DSA suspension includes a baseplate 12, hinge 14 or spring region, load beam 16 and integrated lead flexure 18 with traces 20. The hinge 14 is mounted to the baseplate 12 and extends from the distal end of the baseplate. The load beam is mounted to the distal end of the hinge 14. The flexure 18 is mounted to the load beam 16, typically on the side of the load beam mounted to the hinge 14. Welds such as 22 are typically used to join these components. The baseplate 12, hinge 14 and load beam 16 are typically formed from stainless steel, and the flexure 18 typically includes a base layer of stainless steel. The copper or copper alloy traces 20 on the flexure 18 are separated from the stainless steel base layer by a layer of polyimide or other insulator.
The second stage actuation functionality of the illustrated DSA suspension 10 is incorporated into the baseplate 12. As shown, the baseplate 12 has one or more motor-receiving areas or openings 24 (two in the illustrated embodiment). Piezoelectric (PZT) motors 26 are mounted to the baseplate 12 in the motor-receiving openings 24. The motors 26 are mounted to tabs 28 extending from the baseplate 12 into the motor-receiving openings 24. In the illustrated suspension 10 the tabs 28 are portions of the hinge 14. In other embodiments (not shown) the tabs 28 to which the PZT motors 26 are mounted can be other components such as a separate motor plate welded to the baseplate. Epoxy or other adhesive is typically used to mount the motors 26 to the tabs 28.
DSA suspensions can be embodied in still other forms. For example, an alternative DSA suspension structure is illustrated and described in the Okawara U.S. Patent Publication No. 2010/0067151 which is incorporated herein by reference in its entirety and for all purposes. Briefly, the suspension shown in the Okawara publication has an actuator plate to which the motors are mounted. The actuator plate is mounted between the baseplate and hinge. In still other DSA suspensions (not shown), the motors can be mounted to the load beam or hinge.
An electrical connection or conductive joint between an electrical ground contact on a face of the motor and the ground plane of the suspension is typically made by conductive adhesive (e.g., epoxy with silver and/or nickel particles). The ground contacts on the motors typically have an external plated gold (Au) layer. These connections are typically formed by applying a mass of the conductive adhesive at a location where the ground contact of the motor is adjacent to a stainless steel portion of the baseplate, load beam, hinge or flexure. The conductive adhesive contacts both the motor ground contact and the stainless steel portion of the suspension, thereby providing an electrical connection or ground joint from the motor to the stainless steel portions of the suspension that function as the ground plane.
The conductive joint between the motor and the ground plane should be capable of functioning at or below a threshold level of acceptable resistance under all applied processing and operational load conditions. However, consistently maintaining acceptable resistance to ground levels has been difficult. In particular, the resistance of the conductive adhesive-to-stainless steel component joints have been determined to be relatively high and unstable.
SUMMARY OF THE INVENTION
A dual stage actuation (DSA) suspension in accordance with the invention has a stable, low resistance conductive adhesive electrical connection between an electrical contact on a motor and a plated contact area on a stainless steel component of the suspension. The contact area on the suspension component is plated with conductive and generally non-corrosive metal or metal alloy such as gold or nickel gold. In one embodiment, the stainless steel component includes a stainless steel layer of a flexure and the suspension includes a baseplate having a through hole. The conductive adhesive connection extends from the motor, across a portion of the baseplate, into the though hole of the baseplate and into contact with the plated contact area on the stainless steel layer of the flexure.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 A is an isometric illustration of the flexure side of a prior art dual stage actuation (DSA) suspension.
FIG. 1B is an isometric illustration of the opposite, baseplate side of the prior art suspension shown in FIG. 1A.
FIG. 2 is a plan view illustration of a portion of a DSA suspension in accordance with an embodiment of the invention having a plated flexure.
FIG. 3 is a plan view illustration of an alternative embodiment of the suspension shown in FIG. 2.
FIG. 4 is a side view illustration of a portion of a DSA suspension in accordance with another embodiment of the invention having a plated flexure.
FIG. 5 is a plan view illustration of the suspension shown in FIG. 4.
FIG. 6 is a plan view illustration of a portion of a DSA suspension in accordance with another embodiment of the invention having a formed flexure tab.
FIG. 7 is a side view illustration of the suspension shown in FIG. 6.
FIGS. 8 and 9 are plan view illustrations of portions of a DSA suspension in accordance with another embodiment of the invention having a plated hinge.
FIGS. 10 and 11 are plan view illustrations of portions of a DSA suspension in accordance with another embodiment of the invention having a plated hinge having a tab. The tab is shown unformed in FIG. 10 and formed in FIG. 11.
FIG. 12 is an isometric illustration of the suspension shown in FIG. 11.
FIGS. 13 and 14 are plan view illustrations of portions of a DSA suspension in accordance with another embodiment of the invention having a plated add-on feature.
FIG. 15 is a plan view illustration of a plated unformed baseplate in accordance with another embodiment of the invention.
FIG. 16 is a plan view illustration of the plated baseplate in FIG. 15 in the formed state.
FIG. 17 is a plan view illustration of a portion of a DSA suspension in accordance with an embodiment of the invention having a plated plug.
FIG. 18 is a plan view illustration of the baseplate and plated plug components of the suspension shown in FIG. 17.
FIG. 19 is a cross section side view illustration of the assembled baseplate and plated plug components shown in FIGS. 17 and 18.



DETAILED DESCRIPTION
Overview
The invention is a dual stage actuation (DSA) suspension having a stable, low resistance conductive adhesive electrical connection or joint between an electrical contact on a motor of the suspension and a plated metal contact area on a stainless steel component of the suspension. One embodiment of the invention includes a ground joint between the electrical contact of a piezoelectric (PZT) motor and a gold or nickel gold plated contact area on the stainless steel suspension component. The gold or nickel gold or other conductive and generally non-corrosive metal or alloy plated area on the stainless steel suspension component is referred to generally in the description of the invention below as the plated region. In still other embodiments a layer of nickel is plated on the stainless steel, and a gold layer is plated on the nickel layer.
As described below in connection with the attached drawing figures, the invention can be embodied in a number of different structures. For example, the invention can be embodied in DSA suspensions such as that described above in connection with FIGS. 1A and 1B. Alternatively, the invention can be embodied in DSA suspension structures of the type disclosed in the Okawara U.S. Patent Publication No. 2010/0067151. For example, the stainless steel suspension component to which the ground joint is made can be a baseplate, load beam, hinge, motor plate, flexure or other component. The plated contact area on the stainless steel suspension component can be heat treat annealed. In some embodiments of the invention, the plated contact surface retains a full surface coverage of the plated alloy. In other embodiments of the invention the plated contact surface includes approximately 98% stainless steel and 2% gold following the heat treat and annealing process. In yet other embodiments, the plated contact surface includes about 90% stainless steel surface and about 10% gold. Only the portion of the component to which the conductive adhesive ground joint is being made need be plated (e.g., patterned and selectively plated), although in other embodiments larger areas or even the entire component surface can be plated.
The invention provides a reliable, stable and low resistance joint between the conductive adhesive and the plated stainless steel contact area. The desired resistance level can vary with the application of the suspension (e.g., with the drive circuitry that the motor is to be connected). One example specification calls for ground contact resistance levels no greater than 2500 ohms. Another specification calls for resistance levels no greater than 100 ohms. Still other embodiments of the invention have a resistance no greater than 10 ohms and even less than 1 ohm over the life of the suspension.
Plated Flexure Embodiments
FIGS. 2 illustrates portions of a suspension 110 in accordance with an embodiment of the invention having a through hole or opening 130 in the baseplate 112 that exposes a gold plated contact 132 on the flexure 118. Features of the suspension 110 that are similar to those of suspension 10 described above in connection with FIGS. 1A and 1B are identified by similar reference numbers in the “100” series. Conductive adhesive 134 extends from the motor contact 136, over the baseplate 112, into and through the baseplate opening 130, and to the plated flexure contact 132. The plated contact 132 on the flexure 118 can be a contact plated directly onto the stainless steel base layer of the flexure 118. In an alternative embodiment shown in FIG. 3 illustrating portions of suspension 110′ a through hole 131′ is etched or otherwise formed through the stainless steel base layer of the flexure 118′ to expose a plated portion of a trace 120′ on the flexure. In this alternative embodiment the conductive adhesive 134′ extend through the holes 130′ and 131′ in the baseplate 112′ and the flexure 118′, and contacts the plated flexure trace 120′.
FIGS. 4 and 5 illustrate portions of a suspension 210 in accordance with another embodiment of the invention. Features of the suspension 210 that are similar to those of suspension 10 described above in connection with FIGS. 1A and 1B are identified by similar reference numbers in the “200” series. In this embodiment the mass of conductive adhesive 234 extends from the motor contact 236, over the edge of the motor 226, into a gap 227 between the motor and baseplate 212, and into contact with the plated contact region 232 on the flexure 218. As with the embodiment shown in FIGS. 2 and 3, the plated contact 232 on the flexure 218 can be on the stainless steel base layer or on a trace exposed at a through hole (not shown) in the flexure. Non-conductive adhesive 233 is used to mount the motor 226 to the hinge tabs 228 and isolate the second (bottom) electrode of the motor from the conductive adhesive 234 of the ground joint.
Formed Flexure Embodiments
FIGS. 6 and 7 illustrate portions of a suspension 310 in accordance with another embodiment of the invention having a flexure 318 with a tab 360 or paddle on the stainless steel base layer 361 that has a plated contact 362. Features of the suspension 310 that are similar to those of suspension 10 described above in connection with FIGS. 1A and 1B are identified by similar reference numbers in the “300” series. The flexure tab 360 is formed (e.g., two 90° bends 363, 364 are shown) to extend out of the plane of the other portions of the flexure 318, through a gap 365 between the baseplate 312 and motor 324, and into contact with the ground contact 336 on the motor. A mass of conductive adhesive 334 joins the plated contact 362 on the formed flexure tab 360 to the motor ground contact 336.
Plated Hinge Embodiments
FIGS. 8 and 9 illustrate portions of a suspension 410 in accordance with another embodiment of the invention having a plated contact 470 on a portion of the hinge near or adjacent to the motor 426 (e.g., the hinge motor tab). FIG. 9 shows the suspension 410 after a de-tabbing step relative to FIG. 8. Features of the suspension 410 that are similar to those of suspension 10 described above in connection with FIGS. 1A and 1B are identified by similar reference numbers in the “400” series. The conductive adhesive 434 extends from the motor contact 436 over the edge of the motor 426 and into contact with the plated contact 470 on the hinge 414. In the illustrated embodiments the conductive adhesive 434 also extends over a portion of the baseplate 412 and the edge of the baseplate.
FIGS. 10-12 illustrate portions of suspension 510 in accordance with another embodiment of the invention having a formed plated hinge 514. Features of the suspension 510 that are similar to those of suspension 10 described above in connection with FIGS. 1A and 1B are identified by similar reference numbers in the “500” series. A plated contact 570 is formed on a tab 580 extending from the hinge 514. The tab 580 is shown in an unformed state in FIG. 10. During suspension 510 assembly the tab 580 is formed to extend up the edge and over the baseplate 512 at a location adjacent to the motor 526. The conductive adhesive 534 extends between the motor ground contact 536 and the plated contact 570 on the formed tab 580, across the baseplate 512.
Add-On Feature Embodiments
FIGS. 13 and 14 illustrate portions of a suspension 610 in accordance with another embodiment of the invention including a separately manufactured plated element or feature 682 that is welded (e.g., by welds 622) or otherwise attached to the baseplate 612 adjacent to the motors 626. The conductive adhesive 634 extends from the motor contact pad 636 to the plated surface 681 of the feature 682, over the edge of the feature. FIG. 14 shows the suspension 610 after a de-tabbing step and application of conductive adhesive 634 relative to FIG. 13.
Plated Baseplate Embodiments
FIGS. 15 and 16 illustrate plated baseplates 712 in accordance with another embodiment of the invention. A plated stripe 790 is formed on the baseplate stock. FIG. 15 shows the baseplate 712 unformed. The stock is formed with the plated stripe 790 located adjacent to the motor openings 724 as shown in FIG. 16. The mass of conductive adhesive (not shown) will extend between the motor contact (not shown) and the plated portion 790 of the baseplate 712.
Plated Plug Baseplate
FIGS. 17-19 illustrate portions of a suspension 810 in accordance with another embodiment of the invention including plated stainless steel plugs 892 in the baseplate 812. Features of the suspension 810 that are similar to those of suspension 10 described above in connection with FIGS. 1A and 1B are identified by similar reference numbers in the “800” series. The plated plugs 892 can be manufactured separately from the baseplate 812, and mechanically forced into holes in the baseplate with the plated surface 893 oriented toward the same side of the baseplate as the motor contacts 836. The plug 892 can be press fit, coined or otherwise forced into the hole in the baseplate 812 to form a substantial and secure mechanical, and low resistance contact between the plug and baseplate. Coining provides the additional adavantage of leaving a depression that can be useful in adhesive wicking control. FIG. 19 is a cross section view of an assembled baseplate 812 and plated plug 892. The conductive adhesive 834 is applied so that it extends between the plated surface 893 of the plug 892 and the motor ground contact 836.
Although the invention is described with reference to a number of different embodiments, those skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the invention.

## Claims

1. A dual stage actuation suspension, including:
a flexure, the flexure having a stainless steel base layer, a trace layer, a through hole, and a plated contact, the plated contact comprising a non-corrosive metal or metal alloy plated on the trace layer, the plated contact exposed through the through hole in the flexure;
a motor having an electrical contact; and
a conductive adhesive joint extending from the electrical contact to the plated contact to electrically connect the electrical contact with the trace layer.

2. The suspension of claim 1, wherein the through hole extends through the stainless steel base layer.

3. The suspension of claim 2, wherein the conductive adhesive extends though the through hole to connect to the plated contact.

4. The suspension of claim 1, wherein the trace layer is formed by copper or copper alloy.

5. The suspension of claim 1, wherein the trace layer is separated from the stainless steel base layer by a layer of polyimide.

6. The suspension of claim 1, wherein the conductive adhesive extends from the electrical contact, over an edge of the motor, and into contact with the plated contact.

7. The suspension of claim 1, further comprising a base plate, wherein the conductive adhesive extends from the electrical contact, over an edge of the motor, into a gap between the motor and a baseplate, and into contact with the plated contact.

8. The suspension of claim 1, further comprising a non-conductive adhesive onto which the motor is mounted to isolate a second electrode, located on the bottom of the motor, from the conductive adhesive.

9. The suspension of claim 1, wherein the non-corrosive metal or metal alloy is gold.

10. The suspension of claim 1, wherein the non-corrosive metal or metal alloy is a gold alloy.

11. The suspension of claim 1, wherein the trace layer includes a plurality of traces that extend along the flexure.

12. The suspension of claim 11, wherein the plated contact is on the plurality of traces.

13. A dual stage actuation suspension, including:
a flexure, the flexure having a stainless steel base layer, a trace layer, and a plated contact, the plated contact comprising a non-corrosive metal or metal alloy plated on the trace layer, the trace layer exposed through an opening in the flexure;
a motor having an electrical contact; and
a conductive adhesive joint, the conductive adhesive extending from the electrical contact, over an edge of the motor, through the opening, and into contact with the plated contact to electrically connect the electrical contact with the trace layer.

14. The suspension of claim 13, wherein the opening is in the stainless steel base layer.

15. The suspension of claim 13, wherein the trace layer is formed by copper or copper alloy.

16. The suspension of claim 15, wherein the trace layer includes a plurality of traces and the plated contact is on the plurality of traces.

17. The suspension of claim 13, further comprising a base plate, wherein the conductive adhesive extends from the electrical contact, over the edge of the motor, into a gap between the motor and a baseplate.

18. The suspension of claim 13, wherein the opening is a through hole.

19. The suspension of claim 13, further comprising a non-conductive adhesive onto which the motor is mounted to isolate a second electrode, located on the bottom of the motor, from the conductive adhesive.

20. The suspension of claim 13, wherein the non-corrosive metal or metal alloy is gold or a gold alloy.