Method for fabricating a piezoelectric microactuator having wraparound electrodes - Patent Application 20070123633

Abstract

To precisely control the amount of epoxy to which an adhesive is finally applied.SOLUTION: A method of manufacturing a piezoelectric microactuator with a wraparound electrode includes a step of forming a piezoelectric element having a large center electrode on the top surface and a wraparound electrode including a bottom surface, two opposite ends of the device, and two opposite ends of the top surface. The device is then cut centrally and the device is separated into two individual piezoelectric microactuators with the wraparound electrode.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 62 / 758,471, filed November 9, 2018, and U.S. Patent Application No. 16 / 669,251, filed October 30, 2019, all of which are incorporated herein by reference.

[0002] (Technical field) The present invention relates to the field of suspensions for hard disk drives. More specifically, the present invention relates to a method for fabricating a piezoelectric microactuator having wraparound electrodes for use in a dual stage actuation (DSA) disk drive suspension. [Background technology]

[0003] Magnetic hard disk drives and other types of rotating media drives, such as optical disk drives, are well known. FIG. 1 is a perspective view of an exemplary prior art hard disk drive and suspension to which the present invention may be applied. Prior art disk drive unit 100 includes a rotating magnetic disk 101 that contains a pattern of magnetic ones and zeros that constitute the data stored in the disk drive. The magnetic disk is driven by a drive motor (not shown). Disk drive unit 100 further includes a disk drive suspension 105 to which a magnetic head slider (not shown) is mounted near a distal end of a load beam 107. Suspension 105 is coupled to an actuator arm 103, which is coupled to a voice coil motor 112 that moves suspension 105 in an arc to position the head slider over the appropriate data track of data disk 101. The head slider is held in a gimbal which allows the slider to rock back and forth and side to side so that it follows the appropriate data track on the rotating disk and to accommodate variations in the disk such as vibrations, inertial events such as bumping, and irregularities in the disk surface.

[0004] Single stage actuation disk drive suspensions and dual stage actuation (DSA) suspensions are known in which the voice coil motor 112 alone moves the suspension 105.

[0005] In addition to the voice coil motor that moves the entire suspension, as well as many others, such as U.S. Patent No. 7,459,835 issued to Mei et al., at least one microactuator is located on the suspension to finely move the magnetic head slider to properly align it over the data track of the rotating disk. The microactuator provides finer control and higher bandwidth for the servo control loop than a voice coil motor alone, which only provides a relatively large amount of movement of the suspension, i.e., the magnetic head slider. Piezoelectric elements, sometimes simply called PZTs, are often used as microactuator motors, although other types of microactuator motors are possible. In the following description, for simplicity, the microactuator will be referred to as simply "PZT", although it will be understood that the microactuator need not be of the PZT type.

[0006] Figure 2 is a top view of the prior art suspension 105 of Figure 1. Two PZT microactuators 14 are mounted to the suspension 105 on a microactuator mounting shelf 18 formed in the base plate 12 such that the PZTs span each gap of the base plate 12. The microactuators 14 are attached at each end to the mounting shelf 18 by non-conductive epoxy 16. Positive and negative electrical connections can be made from the PZTs to the flexible wire traces of the suspension and / or to the grounded base plate by various techniques disclosed in commonly owned U.S. Patent No. 7,751,153 to Kulangara et al.

[0007] When assembling a DSA suspension, the process typically involves applying a liquid adhesive, such as an epoxy, over the suspension and / or PZT, placing the PZT in place on the suspension, and curing the adhesive, typically by thermal curing, ultraviolet (UV) curing, or other curing method depending on the adhesive used. DSA suspensions often include conductive and / or non-conductive epoxies to bond the PZT to the suspension. Conductive adhesives, such as silver-containing epoxies, are well known and commonly used.

[0008] FIG. 3 shows a prior art technique for bonding two PZTs in a DSA suspension including an electrical connection between the two PZTs. FIG. 3 is not admitted to be prior art within the legal meaning of the term "prior art". Similarly, the process described herein as applying to FIG. 3 is not admitted to be "prior art" within the legal meaning of the term "prior art". FIG. 4 and FIG. 5 are cross-sectional views along cut lines C-C' and D-D' of FIG. 3, respectively, showing the details of the bond. As best shown in FIG. 4, the PZT 330 has electrodes on both sides, with one end of the bottom electrode grounded by conductive epoxy 324 through gold 326 on a grounded stainless steel 328 layer, and the other end insulated by non-conductive epoxy 320. As best shown in FIG. 5, the top electrode is connected by conductive epoxy 322 above non-conductive epoxy 320 to a copper electrical contact pad 316, which is part of the suspension's electrical interconnect or flexible circuit, and is insulated from the stainless steel substrate 312 by an insulating layer 314 such as polyimide. Electrical contact pads 316 provide the driving voltage for the PZT 330. Non-conductive epoxy 320 primarily provides the mechanical bond between the PZT 330 and the stainless steel substrate 312. Generally, it is difficult to control the height of the conductive epoxy 322 for the top electrode, and the entire PZT attachment process requires three epoxy bonding steps, which are time-consuming and expensive. Also, the epoxies for the bottom and top electrodes require two separate curing steps.

[0009] Conventional methods of bonding PZTs to suspensions have drawbacks. Liquid adhesive flow and other issues make it difficult to precisely control the amount of epoxy that the adhesive ultimately applies. Various solutions have been proposed, including channels under the PZT that control adhesive flow and direct excess liquid epoxy away from sensitive areas. For example, U.S. Patent No. 6,856,075 by Houk proposes an adhesive attachment with one or more reliefs under or partially adjacent to the PZT transducer to control adhesive flow by limiting or influencing adhesive movement or flow, while simultaneously preventing excess adhesive fillet height adjacent to the piezoelectric motor. Furthermore, when the PZT is placed on or near a gimbal carrying a magnetoresistive read / write head, it becomes important to be able to predict and control adhesive flow, since differences in adhesive flow and distribution from part to part affect the geometry, mechanical properties, and performance results of the suspension. These issues become especially pronounced when the PZT is placed on a particularly sensitive portion of the suspension, such as on or near the gimbal head slider. In that field, repeatability and predictability are especially important. Furthermore, the presence of liquid epoxy and its dispensing equipment in the final assembly room represents both a potential source of contamination as well as an additional, expensive manufacturing step.

[0010] Another drawback of conventional attachment means is the assembly time delay required for epoxies, including both conductive and non-conductive epoxies, to be applied and cured multiple times. Figure 6 shows a typical manufacturing process for PZT attachment in which liquid epoxy is applied to the PZT, interconnects, and / or load beam prior to attaching the PZT. Conductive epoxy is applied at the interconnects (610) and non-conductive epoxy is applied elsewhere on the load beam or PZT (612). The PZT is attached to the suspension (614) and the epoxy is cured in a first curing step (616). Then, conductive epoxy is applied again (618) and cured in a second curing step (620). Summary of the Invention

[0011] To address the above and other disadvantages in conventional assembly processes, the present invention employs types of adhesives other than those customarily used in DSA suspensions, and bonding and curing steps other than those customarily used in DSA suspensions.

[0012] In one aspect, the invention employs an adhesive film between the PZT and the suspension and / or partial curing (B-stage) of a liquid or paste adhesive, such as an epoxy, on the PZT before the PZT is placed on the suspension component. The suspension component to which the PZT is attached may be a base plate, as shown in Figures 1 and 2, in the case of a base plate with a microactuator mounted thereon, a flexure, as shown in Figures 3-5, in the case of a flexure with an actuator, a suspension load beam, the head slider itself mounted thereon if the PZT is aligned thereon, or another suspension component with a microactuator mounted thereon. After the two parts are mated, the epoxy or other adhesive is finally cured. Curing may be thermal, UV or other curing methods.

[0013] In a second aspect, the invention is a method of fabricating a PZT microactuator or other electronic device having wraparound electrodes, and methods of applying and using such devices. The wraparound electrodes are conductive paints that surround at least a portion of the PZT to cover multiple sides of the PZT and conduct electricity to the opposite side. The wraparound electrodes simplify both the assembly process and the eventual electrical connection to the PZT in the completed suspension. According to the method, a central electrode is first formed, such as by sputtering, on a first side of a wafer of piezoelectric material. A first side electrode is then formed on a first side or end of the wafer and over an adjacent edge such that the first electrode extends to the first side but is not electrically connected, i.e., is discontinuous, with the central electrode on that side. Similarly, a second side electrode is formed on a second side or end opposite the first side, such that the second electrode extends to the first side but is electrically discontinuous with the central electrode, and over an adjacent edge. A conductive material is then deposited, such as by sputtering, on a second side of the wafer opposite the first side, which extends to and electrically contacts the first and second side electrodes. The wafer has a central electrode on the first side covering most of the first side, and two side electrodes, each side electrode covering not only its respective side, but also surrounding and covering that side, at least a respective portion of the first and second sides, preferably each narrow strip on the first side on either side of the central electrode. The wafer is then cut in half. The result is two piezoelectric devices with wrap-around electrodes such that the first side includes both electrodes. Thus, drive and ground connections can be made to the first side of the PZT, simplifying electrical connections to the PZT.

[0014] The present invention simplifies the assembly process for DSA suspensions and eliminates a source of contamination of the delicate final suspension assembly.

[0015] Exemplary embodiments of the present invention are further described below with reference to the drawings, in which like numerals refer to like parts, and in which the figures may not be to scale and certain elements are shown in commercially designated generalized or schematic form for clarity and conciseness. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view of a prior art disk drive assembly having a DSA suspension. [Diagram 2] FIG. 2 is a top view of the prior art suspension 105 of FIG. [Diagram 3] FIG. 3 is a perspective view of a conventional DSA suspension that can be applied to the present invention. [Figure 4] FIG. 4 is a cross-sectional view taken along line CC' in FIG. [Diagram 5] FIG. 5 is a cross-sectional view taken along the line DD' in FIG. [Figure 6] FIG. 6 is a process flow diagram of the process used to attach the PZT to the suspension of FIG. [Figure 7] FIG. 7 is a process flow diagram of a simplified process used to attach a PZT to a suspension in accordance with the present invention. [Figure 8] FIG. 8 is a perspective view of a DSA suspension minus the flexure gimbal assembly according to one embodiment of the present invention that employs an integrated adhesive pattern printed above the PZT. [Figure 9] FIG. 9 is an exploded view of the suspension of FIG. [Figure 10] FIG. 10 is a perspective view of one of the PZT suspensions of FIG. 8, showing the integral adhesive film underneath. [Figure 11] FIG. 11 is a perspective view of a portion of a DSA suspension in which an integral adhesive film is used on top of a PZT according to an additional embodiment of the present invention. [Figure 12] FIG. 12 is a perspective view of the PZT in FIG. [Figure 13] FIG. 13 is a cross-sectional side view of a PZT having wraparound electrodes in accordance with an additional embodiment of the present invention. [Figure 14] FIG. 14 is a process flow diagram of the conventional epoxy application and bonding steps for the PZT of FIG. [Figure 15] FIG. 15 is a process flow diagram for the application and bonding steps of the PZT of the present invention and the conventional epoxy shown in FIG. [Fig. 16A-G] 16A-G show the fabrication steps for making the PZT with wraparound electrodes shown in FIG. [Figure 17A-B] 17A-B are isometric views of a PZT wafer at a second step during the manufacturing process according to the present invention. [Fig. 18A-G] 18A-G show alternative manufacturing processes that can be used to produce the PZT of FIG. [Figure 19] FIG. 19 is a perspective view of a PZT with adhesive applied in accordance with the present invention. [Figure 20] FIG. 20 is a top perspective view of the PZT of FIG. 19 shown B-staged. [Figure 21] FIG. 21 is a cross-sectional side view of the PZT of FIG. 20 after it has been applied to a suspension. [Figure 22] FIG. 22 is a cross-sectional side view of a PZT with wraparound electrodes after it has been applied to a suspension. [Figure 23A-B] 23A-B show a process for using a die attach adhesive at the PZT wafer level according to one embodiment. [Fig. 23C-D] 23C-D show a process for using a die attach adhesive at the PZT wafer level according to one embodiment. [Figure 24] FIG. 24 illustrates a cross-sectional view of a PZT die attached to a suspension, according to one embodiment. [Diagram 25] FIG. 25 illustrates one embodiment of a singulated PZT die that includes another portion of adhesive disposed between the first and second portions of adhesive. [Figure 26] FIG. 26 illustrates one embodiment of a singulated PZT die that includes another portion of adhesive disposed between the first and second portions of adhesive. [Figure 27] FIG. 27 shows one embodiment of a singulated PZT die including an adhesive portion. [Figure 28] FIG. 28 shows a fragment of a two-stage actuated suspension including two singulated PZT dies 2806 according to embodiments described herein. [Figure 29] FIG. 29 illustrates a cross section of a multi-layer singulated PZT die with adhesive according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The first aspect of the present invention is the use of an adhesive film to attach the PZT to the suspension. The method is shown in FIG. 7. A conductive epoxy is applied at the interconnect (710). A PZT with an integral adhesive film, or other B-staged adhesive, is attached to the suspension (712), and the adhesive is then cured (714). A conductive epoxy is then applied (716) and cured (718). The step of applying epoxy to the load beam is eliminated by using a PZT with an integral adhesive film. A PZT with an integral adhesive film can be manufactured using a laminated adhesive film at the PZT wafer level, or by printing or wafer backside coating processes used in the semiconductor industry. The adhesive film is attached to the PZT at the wafer level before dicing into individual PZT dies, which can simplify the process and reduce costs. It can also provide tighter control over the thickness of the adhesive. As shown in FIG. 7, the use of a PZT with an integral adhesive simplifies the process compared to FIG. 6. The step of applying non-conductive epoxy at the load beam is eliminated using the method of the present invention.

[0018] Suspension designs that facilitate the use of an integrated adhesive film are shown in Figures 8-10. Figure 8 is a perspective view of a DSA suspension, excluding the flexure gimbal assembly for clarity of illustration, according to one embodiment of the present invention employing an integrated adhesive film or pattern printed on a PZT. A PZT 830 is attached to the suspension component to be mounted, in this case base plate 812. Actuation of the PZT moves load beam 820 such that a head slider located at the distal end of the load beam moves radially.

[0019] FIG. 9 is an exploded view of the suspension of FIG.

[0020] Figure 10 is a perspective view of one of the PZTs 830 of the suspension 810 of Figure 8, showing integral adhesive films or printed adhesives 834, 836 underneath. In this embodiment, the integral adhesive films 834, 836 located on either end of the PZT 830 are formed by applying an adhesive film or printing an adhesive pattern onto the PZT wafer prior to dicing and singulating the individual PZTs. The exposed PZT surface between the adhesives provides an electrical connection between the liquid epoxy and the suspension's electrical circuitry.

[0021] FIG. 11 is a perspective view of a portion of a DSA suspension according to an additional embodiment of the present invention, in which an integral adhesive film is used on the top surface of a PZT 1130 to bond the PZT to a recess in a base plate 1112 .

[0022] FIG. 12 is a perspective view of the PZT of FIG. 11. In this design, an integral adhesive film or printed adhesive 1134 is placed on the top surface of the PZT. The integral adhesive film covers the entire top surface or partially the entire top surface, so no adhesive patterning is required. Also, a conductive film may be used in this design so that when the PZT is attached to the base plate, grounding through the base plate may be achieved. This further eliminates the necessary step of grounding the PZT to the base plate using a conductive liquid epoxy as shown in FIG. 6.

[0023] The adhesive films used can be either conductive or non-conductive depending on whether a conductive connection to the suspension or interconnect circuitry is desired or a non-conductive connection to the suspension. Film adhesives are generally "preformed" or "B-staged" and are available in rolls, sheets, or die cut forms.

[0024] (B-staged epoxy) In a slightly different embodiment, instead of applying an adhesive film to the PZT and / or suspension, an adhesive is applied to the PZT and B-staged prior to final assembly.

[0025] As used herein, the term "B-staged" or "B-staging" refers to partially solidifying an adhesive after it has been applied such that its flow is substantially reduced to the point where it no longer flows freely as a liquid, but is not so hard that it is no longer available to effectively bond to other surfaces. B-staging involves temporarily exposing the adhesive to an environment that accelerates the adhesive's hardening, and then removing the adhesive from that environment such that the cure rate is significantly reduced, so that the adhesive does not substantially solidify upon assembly. Removing the PZT from the accelerated hardening environment may simply involve removing the cure accelerator from the environment. B-staging may harden or solidify the adhesive to the point where it is no longer tacky. One method of B-staging is to partially cure a crosslinking polymer such as an epoxy, such as by heat and / or UV, such that the epoxy adhesive is less than 10% crosslinked, and then removing the source of hardening. In the case of a thermally B-staged epoxy, the epoxy is immediately quenched to a temperature low enough that crosslinking is negligible, i.e., the epoxy is not effectively solidified, to stop the crosslinking process. In the case of UV B-staged epoxies, removing the PZT from the accelerated cure environment can simply mean turning off the UV curing lamp.

[0026] In some adhesives, the adhesive may be mixed with a solvent to form a slurry, which is evaporated at a temperature below that at which crosslinking begins to occur significantly. The adhesive may be a printable paste that is applied to the PZT. After application, the adhesive is exposed to a specific form of heat designed to drive off most of the solvent from the material without significantly promoting crosslinking of the resin. The result is an epoxy or other adhesive that no longer flows, but can be bonded to another surface with full or near-full epoxy adhesive strength.

[0027] B-staging adhesives allow the adhesive and substrate structure to be "staged" or held for a period of time prior to bonding and curing without loss of performance. A secondary thermal cure cycle results in a fully crosslinked, void-free bond. As used herein, the term "fully crosslinked" means at least 90% crosslinked.

[0028] The adhesive may take the form of a solid, thermosetting paste. The adhesive may also be a printable paste that is printed by any known printing technique suitable for use with adhesives, including screen printing, stencil printing, inkjet printing, spraying, stamping, and the like. The advantage of using such printing techniques is that the adhesive may be applied onto the PZT in very fine and precise patterns, allowing for control and repeatability of the total mass and distribution of adhesive in the finished suspension. One commercially available silver-containing conductive epoxy suitable for fluid jetting, stencil printing, and stamping is EPO-TEKH20E from Epoxy Technology.

[0029] UVB stage adhesives may be used. Such adhesives are applied and then irradiated with UV energy to B-stage. B-staging immediately after printing "freezes" the adhesive in place and allows precise control over the spreading of the liquid epoxy.

[0030] A liquid epoxy or other adhesive may be applied first on the PZT and / or on the suspension, after which the epoxy is B-staged to a point where its flow is negligibly reduced. The parts may be finally assembled in a clean room assembly area for the disk drive, after which the adhesive is fully cured, either thermally or UV. Such techniques have been used or proposed for use in the integrated circuit (IC) packaging field under the broad term wafer backside coating (WBC). Wafer backside coating techniques using both conductive and non-conductive adhesives may be adapted from the die attach process used in IC packaging to the PZT attach process for the suspension. Inkjet printing of both conductive and non-conductive adhesive polymers has also been proposed. Such inkjet printing techniques may be adapted for use in printing adhesives on the PZT to bond the PZT to the suspension.

[0031] It is expected that one method of fabrication would be to start with a wafer of PZT material and apply the adhesive already B-staged, such as in adhesive film form, to the wafer, or to apply the adhesive to the wafer and then B-stage, and then dice the wafer into individual PZT microactuator motors. A pick and place machine would be used to pick up the individual PZT die with the B-staged adhesive, assemble the PZT die onto a suspension, and dwell for the appropriate time and under the appropriate temperature and pressure conditions to fully cure the adhesive, fully bonding the PZT to the suspension.

[0032] (wraparound electrode) In another aspect, the invention is a method of fabricating a piezoelectric microactuator or other electronic device having wraparound electrodes such that both the drive voltage and ground electrodes are located and accessible on the same side of the device.

[0033] FIG. 13 is a cross-sectional side view of a PZT according to an additional embodiment of the present invention. The PZT 1330 has a bottom electrode 1334 and a "wrap-around" electrode 1336 that simplifies electrical connections to the PZT. In this embodiment, the top electrode 1336 is wrapped around the PZT on one end of the bottom PZT surface. Thus, the driving voltage is applied to the bottom surface of the PZT at the first end, and electrical ground is connected to the bottom surface at the opposite end. Thus, both electrodes 1334, 1336 can be electrically connected on the same face or side of the PZT by conductive epoxy 1340, 1342, respectively. This reduces the number of epoxy bonding steps to two steps and eliminates the difficulty in controlling the epoxy height tolerance on top of the PZT surface. Furthermore, only a single curing step is required.

[0034] Figure 14 is a flow diagram of a manufacturing process using a conventional epoxy application and bonding step to attach a PZT to a suspension as shown in Figure 3. First a conductive epoxy is applied (1410) for grounding. Then a non-conductive epoxy is applied (1412) for insulation. The PZT is then attached to the suspension in step 1414. The epoxy is then cured (1416). Then a second epoxy application step is performed (1418). Finally, the last applied epoxy is cured (1420). This process required two separate curing steps.

[0035] Figure 15 is a flow diagram of a manufacturing process according to the present invention for bonding a PZT to a suspension as shown in Figure 13. Conductive epoxy is applied for ground (1510). Then conductive epoxy is applied for the signal or drive voltage (1512). The PZT is then attached to the suspension (1514). Finally, the assembly is cured (1516). The diagram illustrates the simplification gained by using a PZT with wraparound electrodes according to the present invention.

[0036] 19-21 illustrate the preparation and placement of a PZT with B-staged adhesive in accordance with the present invention. FIG. 19 is a perspective view of a PZT 1930 with adhesive 1920, 1924 applied to what is on the bottom side of the PZT 1930. Generally, the adhesive may be applied by any one of a number of known techniques including screen printing, stencil printing, inkjet printing, spraying, application as a film, and the like. Generally, any desired pattern of conductive and / or non-conductive adhesive combinations may be applied to the PZT 1930. In an exemplary embodiment of the present invention, the adhesive is jetted by inkjet heads 1910, 1911 to produce one strip of conductive epoxy 1924 and one strip of non-conductive epoxy 1920. The two strips may be of different thicknesses, one strip thicker than the other.

[0037] FIG. 20 is a top perspective view of a PZT 1930 with adhesive being B-staged. In the figure, strips of epoxy 1920, 1924 are B-staged by UV. In general, the adhesive 1920, 1924 may be B-staged using any known technique, including thermal B-staging and UV B-staging. Additionally, the two strips of adhesive 1920, 1924 may be B-staged to different degrees, leaving one strip more cured or solidified than the other. For UV curing, a mask or screen may be used to expose one strip more than the other.

[0038] FIG. 21 is a side cross-sectional view of the PZT 1930 after it has been applied to the suspension. FIG. 21 is similar to FIG. 3 and shows how the present invention can simplify a conventional process. After the PZT 1930 is in place, pressure is applied to at least the left side of the PZT as shown in the figure to force the non-conductive epoxy 1920 into the gap between the PZT and the polyimide layer 314 and cover the previously exposed stainless steel 312 adjacent to the PZT. Pressure may be applied mechanically on the PZT. Alternatively, depending on how much solidification has occurred during the B-stage process, the weight of the PZT itself may provide enough force and pressure to force the non-conductive epoxy 1920 into the gap. After the PZT is in place and pressed down if necessary, conductive epoxy 322 is applied to fill the gap between the metallized top surface of the PZT that defines the drive electrode and the copper contact pad 316 that provides the drive voltage to the PZT. All of the epoxies in the assembly are then cured simultaneously in a single curing step. This process eliminates the need for a second curing step as was required for the assembly and process of FIGS.

[0039] 21 shows only one of many different types and methods of electrical connections for providing the PZT drive voltage and ground to the PZT. Many other connection types and methods are possible, such as those disclosed in patents 8,189,301 to Schreiber and 7,751,153 to Kulangara. The present invention is applicable to suspensions employing many different types of electrical connections to the PZT.

[0040] As an alternative to the bonding structure shown in FIG. 21, the PZT 1930 may be extended further to the left of the figure so that the PZT is bonded directly to the copper contact pad 316 .

[0041] Figures 16A-16G show the manufacturing steps for creating a PZT with wraparound electrodes as shown in Figure 13. First a PZT block or wafer 1630 is placed on a transfer tape 1602 with the PZT bottom surface 1631 facing down (Figure 16A). Next, a suitable mask is placed over the top surface of the PZT wafer and a metallization layer 1604, such as aluminum metallization, is sputtered onto the top surface (Figure 16B). The mask leaves strips 1606 of the PZT surface unmetallized. A kerf 1608 is then cut into the PZT wafer to separate a first portion, called the PZT precursor 1632, from the rest of the wafer (Figure 16C). A second mask 1612 is placed over the PZT precursor 1632 and additional metallization 1605 is sputtered into the kerf on the sides of the PZT precursor 1632 within the kerf 1608, making those sides conductive and electrically continuous with the metallization on the top surface of the PZT adjacent to the kerf (Figure 16D).

[0042] Next, the PZT precursor 1632 is flipped over and preferably placed onto a second transfer tape to expose what was previously the bottom surface 1631 of the PZT precursor (FIG. 16E). The bottom surface 1631 continues to be referred to as the bottom surface even though it is now facing up. A metallization layer 1614 is then sputtered over the entire bottom surface 1631 of the PZT precursor (FIG. 16F). Finally, a new cut 1616 is made in the PZT, separating the first PZT approximately in half to define what will now be referred to as a first PZT 1634 and a second PZT 1636 (FIG. 16G).

[0043] As a result of this process, the two PZTs 1634, 1636 each have the same structure. A narrow stripe 1650 of metallization near the top surface 1633 and its edge of the first PZT defines a first electrode. The first electrode 1650 electrically surrounds the bottom surface 1631 of the PZT and the metallization 1604 that substantially covers the bottom surface 1631 via the metallized side surface 1605 of the PZT. A second electrode 1652 on the top surface 1633 of the first PZT covers most, but not all, of the PZT top surface 1633. In this manner, a first PZT is constructed in which the first electrode 1650 is located on the same surface of the first PZT as the second electrode 1652. In general, the first electrode can be the electrode to which the PZT drive voltage is applied and the second electrode can be the electrode to which the PZT is grounded, or vice versa. The second PZT is substantially the same as the first PZT.

[0044] Figures 17A and 17B are isometric views of a PZT wafer at selected steps during the manufacturing process of the present invention. Figure 17A is an isometric view of PZT strips 1634, 1636 at the end of the process of Figure 16. The PZTs are now ready to be poled and a final dicing operation can be performed to create the individual PZTs shown in Figure 17B. As a result, both the first row of PZTs 1638 and the second row of PZTs 1640 have wraparound electrodes.

[0045] 18A-18G show an alternative manufacturing process for creating a PZT with wraparound electrodes. A PZT wafer 1830 is placed on a transfer tape 1802 with the bottom surface 1831 facing down (FIG. 18A). A kerf 1808 is then cut into the PZT 1830 to separate a first portion, called the PZT precursor 1832, from the rest of the wafer (FIG. 18B). The kerfs 1808 on either side of the PZT precursor 1832 are filled with a conductive and curable material 1820, such as a conductive epoxy paste made of copper, silver, or other conductive materials or particles (FIG. 18C). Silver epoxy is one commonly used material and is used as an example. The silver epoxy 1820 is then allowed to solidify. A suitable mask is then placed over the top surface of the PZT precursor 1832, and a metallization layer 1804, such as aluminum metallization, is sputtered onto the top surface (FIG. 18D). The mask prevents metallization along two narrow strips 1806, 1807 on the top surface of the PZT precursor near the ends. As a result, the PZT precursor 1832 has two relatively narrow stripes of metallization 1842, 1844 on the top surface of the PZT precursor near both ends, and a large metallization area 1846 approximately in the center of the PZT precursor. At this point in the process, each stripe of metallization 1842, 1844 near the ends of the PZT precursor is electrically connected to the silver epoxy 1820 on the end of the PZT precursor to which it is adjacent, and the two stripes of metallization 1842, 1844 and the large central metallization area 1846 are all electrically isolated or electrically discontinuous from one another.

[0046] Next, the PZT precursor is flipped over and preferably placed on a second transfer tape to expose what was previously the bottom surface 1831 of the PZT precursor (FIG. 18E). The bottom surface 1831 continues to be referred to as the bottom surface even though it is now facing up. A metallization layer 1814 is then sputtered over the entire bottom surface of the PZT precursor (FIG. 18F). Finally, a new cut 1818 is made in the PZT precursor, cutting it approximately in half, and another cut 1816 is made through the silver epoxy, thereby separating the PZT precursor approximately in half and defining what are now referred to as the first and second PZTs (FIG. 18G). The cut 1816 is within the kerf 1808 and is narrower than the kerf 1808 to leave the side of the PZT precursor covered with conductive silver epoxy 1820, which acts as an electrical bridge or wraparound from the top to the bottom surface of the PZT.

[0047] As a result of this process, each of the two PZTs has the same structure. A narrow metallization stripe 1844 near the top surface 1833 and edge of the first PZT defines a first electrode. The first electrode 1844 electrically surrounds the bottom surface 1831 of the PZT and the metallization substantially covering the bottom surface 1831 via the silver epoxy 1820. In this manner, a first PZT is constructed in which the first electrode 1844 is disposed on the same surface of the first PZT as the opposing electrode 1852. The second PZT is substantially identical to the first PZT.

[0048] FIG. 22 is a side cross-sectional view of a PZT with wrap-around electrodes like the PZT shown in either FIG. 16 or FIG. 18 after suspension application. The PZT 1830 has a first electrode and wrap-around electrode 1844 that functions as the drive or positive electrode, and a second electrode 1852 that functions as the ground electrode. The drive electrode 1844 is bonded to a copper contact pad 316 on a polyimide layer 314 above a stainless steel substrate 312 via conductive epoxy 1924. The ground electrode 1852 is grounded to the stainless steel substrate 328 via a gold bond pad 326 and conductive epoxy 1928. The strips of conductive epoxy 1924 and 1928 can be the B-staged epoxy described above, with the epoxy being fully cured after the parts are assembled as shown. This embodiment completely eliminates the need to apply any epoxy in the suspension assembly room and keeps any liquid or paste-like epoxy out of that room, thereby helping to keep the environment contamination-free.

[0049] (Die Attach Adhesive) Traditional approaches to PZT bonding used liquid epoxy in the manufacturing process. The use of liquid results in unnecessary and inconsistent extrusion. Inconsistent amounts of extruded liquid adhesive can cause the adhesive to flow beyond the interconnect area. Additionally, unwanted adhesive can splatter onto other areas or parts of the suspension. Each of the above aspects can adversely affect the performance of the PZT and suspension. In some cases, inconsistent amounts of adhesive can result in failure of the PZT and / or suspension.

[0050] 23A-23D illustrate a process for creating a die attach adhesive at the PZT wafer level according to one embodiment. After printing the adhesive onto the PZT wafer, a drying or B-stage process, such as the processes described herein, is performed to transform the adhesive into a semi-solid state. As a result, the PZT is embedded with adhesive on the sidewalls and bottom of the PZT, allowing fine control over the size and thickness of the adhesive. The PZT can then be bonded onto the suspension by a thermal or curing process. The adhesive film is attached to the PZT at the wafer level before dicing into individual PZTs, which may simplify the process and reduce costs. Additionally, the greater control over the location of the adhesive with the embodiments described herein may allow for more consistent performance results and yields of the PZTs and suspensions incorporating the PZTs.

[0051] FIG. 23A illustrates a PZT wafer cut into individual strips according to one embodiment. In some embodiments, the PZT wafer 2301 is formed from lead zirconate titanate. Other embodiments of the PZT wafer 2301 include wafers formed from other piezoelectric materials, including those known in the art. Additionally, the PZT wafer 2301 may include one or more electrodes or electrode layers. In some embodiments, one or more electrode layers are disposed between one or more layers of piezoelectric material. The PZT wafer 2301 is cut into one or more strips 2302a-c. In some embodiments, the PZT wafer 2301 is cut using techniques, including those known in the art.

[0052] FIG. 23B illustrates a strip of a PZT wafer with adhesive printed on the strip, according to one embodiment. Die attach adhesive 2304a-d is disposed on strips 2302a-c of PZT wafer 2301. In some embodiments, die attach adhesive 2304a-d is formed on top portions of strips 2302a-c adjacent to the edges. Additionally, die attach adhesive 2304a-d is disposed on the sides of each strip 2302a-c. In some embodiments, die attach adhesive 2304a-d is formed on strips 2302a-c using screen printing. For example, a screen containing a pattern is placed over PZT wafer 2301 and liquid adhesive is applied to the screen to prevent the liquid adhesive from being placed on the screen except on the portions of the PZT wafer that are exposed by the pattern. The liquid adhesive is placed on the screen and pressed onto the exposed portions of the PZT wafer defined by the pattern. In some embodiments, the height of the screen is configured such that the thickness of the adhesive layer placed on PZT wafer 2301 matches the design required for the suspension. Other methods of depositing liquid adhesives may be used, including but not limited to chemical vapor deposition. In some embodiments, the die attach adhesives 2304a-d are B-staged using techniques including those described herein.

[0053] 23C illustrates a singulated PZT die with adhesive according to one embodiment. Strips 2302a-c formed from a PZT wafer 2301 are cut into one or more singulated PZT dies 2306a-i. In some embodiments, the PZT wafer 2301 is cut using techniques including those known in the art. According to some embodiments, the PZT wafer 2301 is cut to have portions 2308a-r of adhesive 2304a-d disposed in the strips 2302a-c on a first end of each singulated PZT die 2306a-i and on a second end opposite the first end of each singulated PZT die 2306a-i.

[0054] FIG. 23D illustrates a cross-sectional view of a singulated PZT die including adhesive according to one embodiment. According to some embodiments, adhesive 2304 is disposed on PZT wafer 2301 such that each portion 2308 of adhesive 2304 is formed on at least two sides of PZT die 2306. For example, portion 2308a is formed on a first side of PZT die 2306 and a portion on the bottom side. Portion 2308b is formed on a second side of PZT die 2306 opposite the first side, including a portion on the bottom side of PZT die 2306. In some embodiments, portion 2308 of adhesive 2304 is formed on a side of PZT die 2306 and a portion on the top side. The above process provides more control over the size and thickness of the adhesive disposed on singulated PZT die. This provides the advantage of producing PZT dies with more uniform performance characteristics at higher yields and eliminates performance degradation that may be caused by adhesive splashing or overfilling.

[0055] FIG. 24 illustrates a cross-sectional view of a PZT die according to one embodiment mounted on a suspension. As shown, a singulated PZT die 2406 formed, for example, using techniques described herein is disposed in a recess in a base plate or microactuator mounting shelf 2418 formed from a base plate 2412 as described herein. In some embodiments, the microactuator mounting shelf 2418 is formed from a load beam coupled to the base plate 2412. In other embodiments, the mounting shelf 2148 is a separate structure from the load beam attached to the base plate 2412. A singulated PZT die 2406 containing adhesive 2408 is formed on two sides of the singulated PZT die 2406 using techniques including those described herein. A portion 2408a of adhesive is disposed on a first side of the singulated PZT die 2404 and configured to contact and adhere to a first edge 2410a of the base plate 2412 and a first shelf 2148a extending from the mounting plate. Similarly, portion 2408b is on the side of the singulated PZT die 2406 opposite portion 2408a and is configured to contact and adhere to a second edge 2410b of the base plate 2412 and a second mounting shelf 2418b extending from the mounting plate. The adhesive is attached to the suspension portion it contacts using techniques including those described herein. Because the singulated PZT die 2406 already has adhesive disposed thereon, the process of mounting the singulated PZT die 2406 eliminates the adhesive from splattering onto another portion of the suspension or flooding a portion of the suspension and causing a detrimental change or failure in the performance characteristics of the suspension since no adhesive is applied when mounting the microactuator to the suspension. According to an embodiment, once the singulated PZT die with the B-staged adhesive is placed on the suspension, the adhesive is fully cured using techniques including those described herein.In some embodiments, at least one or more portions of the suspension are chamfered or beveled to contact and have better contact with the adhesive disposed on the singulated PZT die according to embodiments herein.

[0056] FIG. 25 illustrates an embodiment of a singulated PZT die 2506 including another portion of adhesive disposed between the first portion 2508a and the second portion 2508b of the adhesive. Thus, the embodiment includes one or more portions of adhesive disposed between the first portion 2508a and the second portion 2508b. As shown in FIG. 25, a third portion 2508c of adhesive is disposed between the first portion 2508a and the second portion 2508b, for example, on the bottom surface of the singulated PZT die 2506. Any one or more portions of adhesive may be a conductive adhesive or a non-conductive adhesive. Each type of adhesive may be disposed on the singulated PZT die 2506 using techniques including those described herein. As shown in FIG. 25, the embodiment includes the first portion 2508a and the second portion 2508b of adhesive being a non-conductive adhesive and the third portion 2508c of adhesive being a conductive adhesive. The third portion 2508c as a conductive adhesive is configured to form an electrical connection between the singulated PZT die 2506 and contacts, for example, to provide a drive signal to one or more electrodes of the singulated PZT die 2506. Other embodiments include more than two portions of adhesive.

[0057] FIG. 26 illustrates an embodiment of a singulated PZT die 2606 including another portion of adhesive disposed between the first portion 2608a and the second portion 2608b of the adhesive. As shown in FIG. 26, a third portion 2608c of the adhesive is disposed between the first portion 2608a and the second portion 2608b, for example, on the bottom surface of the singulated PZT die 2606. Any one or more portions of adhesive may be a conductive adhesive or a non-conductive adhesive. Each type of adhesive may be disposed on the singulated PZT die 2606 using techniques including those described herein. As shown in FIG. 26, an embodiment includes where the first portion 2608a and the third portion 2608c of the adhesive are a conductive adhesive and the second portion 2608b of the adhesive is a non-conductive adhesive. The first portion 2608a and the third portion 2608c as conductive adhesives are each configured to form an electrical connection between the singulated PZT die 2606 and a contact, for example, to provide a drive signal or ground connection to one or more electrodes of the singulated PZT die 2606.

[0058] FIG. 27 illustrates one embodiment of a singulated PZT die 2706 including a portion of adhesive. As shown in FIG. 27, the singulated PZT die 2706 includes a first portion of adhesive 2708a and a second portion of adhesive 2708b. The first portion 2708a is disposed on a first side and a portion of the bottom surface of the singulated PZT die 2706 using techniques including those described herein. The second portion 2708b is disposed on the bottom surface of the singulated PZT die 2706. In this embodiment, the second portion is disposed on a single surface of the singulated PZT die 2706. Any portion of adhesive may be a conductive adhesive or a non-conductive adhesive. Each type of adhesive may be disposed on the singulated PZT die 2706 using techniques including those described herein. As shown in FIG. 27, this embodiment includes that the first portion 2708a and the second portion 2708b of adhesive are conductive adhesive. The first portion 2708a and the second portion 2708b as conductive adhesives are each configured to form an electrical connection between the singulated PZT die 2706 and a contact, for example, to provide a drive signal or ground connection to one or more electrodes of the singulated PZT die 2606.

[0059] FIG. 28 shows a fragment of a dual-actuated suspension including two singulated PZT dies 2806 according to an embodiment having a flexure mounted microactuator utilizing the methods and structures described herein.

[0060] FIG. 29 illustrates a cross section of a multi-layer singulated PZT die with adhesive according to one embodiment. The multi-layer singulated PZT die 2901 includes two layers of PZT wafer material. The multi-layer singulated PZT die 2901 includes a plurality of electrodes 2904. A first PZT wafer 2902 is formed using techniques including those described herein. A second PZT wafer 2906 is disposed on the first PZT wafer 2902. In various embodiments, the surface of the first PZT wafer 2902 on which the second PZT wafer 2906 is disposed is at least partially metallized using techniques including those described herein to form an intervening electrode 2904b. The PZT wafers 2902, 2906 are metallized using techniques including those described herein to form electrodes 2904a, c. Other embodiments include more than one PZT wafer and a plurality of intervening electrodes. The PZT wafers 2902, 2906 are diced to form multi-layer singulated PZT dies 2901 using techniques including those described herein.

[0061] According to some embodiments, the adhesive is placed on the PZT wafers 2902, 2906 such that each portion 2908 of adhesive is formed on at least two surfaces of the PZT die 2901 using techniques including those described herein. For example, portion 2908a is formed on a first side and portion 2908b is formed on a second side opposite the PZT die 2901 from the first side and including a portion on the bottom surface of the PZT die 2901. In some embodiments, portion 2308 of adhesive 2304 is formed on a side and a portion on the top surface of the PZT die 2901. Other embodiments include a portion on the bottom surface of the PZT die 2901. The above process allows for more control over the size and thickness of the adhesive placed on the singulated PZT die. This provides the advantage of producing PZT dies with higher yields and more uniform performance characteristics, eliminating performance degradation that may be caused by adhesive splashing or overfilling.

[0062] All features disclosed in this specification, including the claims, abstract, and drawings, and all steps in any method or process disclosed herein, may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive. Each feature disclosed in this specification, including the claims, abstract, and drawings, may be replaced by an alternative feature serving the same, equivalent, or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is only one example from a generic series of equivalent or similar features.

[0063] It is understood that the terms "generally," "approximately," "about," and "substantially" as used in the specification and claims permit a certain degree of variation from any precise dimensions, measurements, and configurations, and that such terms should be understood within the context of the description and practice of the invention disclosed herein.

[0064] It is further understood that terms such as "upper," "lower," "above," and "below," as used in the specification and claims, are convenient terms that describe the spatial relationship of parts to one another, rather than any particular spatial or weight orientation. As such, the terms are intended to include an assembly of parts, regardless of whether the assembly is oriented in the particular orientation shown in the figures and described in the specification, opposite that orientation, or at any other degree of rotation.

[0065] It is recognized that the term "the present invention" as used herein should not be understood to mean that only a single invention having a single essential element or group of elements is presented. Similarly, it is also recognized that the term "the present invention" includes many separate inventions, each of which may be considered to be a separate invention. Thus, although the present invention has been described in detail with reference to preferred embodiments and drawings thereof, it is apparent to those skilled in the art that various adaptations and modifications of the present invention may be made without departing from the spirit and scope of the present invention. For example, instead of selectively applying and partially curing the adhesive on the PZT, the adhesive may be selectively applied and partially cured on other suspension components, such as the flexures. It is therefore recognized that the above detailed description and the accompanying drawings are not intended to limit the scope of the present invention, which is to be determined solely from the following claims and their properly understood legal equivalents.

Claims

1. 1. A method for manufacturing a microactuator, comprising the steps of: providing at least a first wafer of piezoelectric material including one or more electrodes; forming one or more strips of piezoelectric material from said first wafer of piezoelectric material; printing one or more adhesives onto at least one surface of said strip of piezoelectric material; forming one or more singulated dies from one or more of said strips of piezoelectric material, the singulated dies including one or more portions of at least one of any of said adhesives; a portion of the one or more adhesives is disposed in each of the strips on a first end of each of the one or more singulated dies and on a second end of each of the one or more singulated dies opposite the first end; Printing one or more adhesives onto at least one surface of said strip of piezoelectric material includes: placing a template over the strip; applying the one or more adhesives, including a liquid adhesive, to the template; and forcing the liquid adhesive onto one or more portions of the strip remaining exposed by the template.

2. The method of claim 1 , wherein forming the one or more strips of piezoelectric material from the first wafer comprises dicing the first wafer.

3. The method of claim 1 , wherein applying the liquid adhesive to the template comprises applying a non-conductive adhesive to the template.

4. The method of claim 1 , wherein applying the liquid adhesive to the template comprises applying a conductive adhesive to the template.

5. The method of claim 1 , wherein the liquid adhesive comprises one of a conductive adhesive and a non-conductive adhesive.

6. 2. The method of claim 1, wherein forming one or more singulated dies including one or more portions of at least one of the adhesives from one or more of the strips of piezoelectric material comprises dicing one or more of the strips of piezoelectric material.

7. The method of claim 6 , wherein dicing the one or more strips of piezoelectric material comprises dicing the one or more strips of piezoelectric material to include at least two portions of any of the adhesives.

8. 2. The method of claim 1, wherein the template is configured to expose one or more portions of the strips, and wherein pressing the liquid adhesive onto one or more portions of the strips that remain exposed by the template disposes the pressed liquid adhesive onto at least the first end of each of the strips.

9. The method of claim 3 , wherein the template is configured to expose one or more portions of the strips, and when the liquid adhesive is pressed onto one or more portions of the strips left exposed by the template, the pressed liquid adhesive is disposed on a top surface of each of the strips.

10. 9. The method of claim 8, wherein the template is configured to expose one or more portions of the strips, and wherein pressing the liquid adhesive onto one or more portions of the strips left exposed by the template causes the pressed liquid adhesive to be disposed on a top surface of the strips and a portion of the liquid adhesive disposed on the top surface of the strips to come into contact with the liquid adhesive disposed on the first end of each of the strips.

11. The method of claim 10, wherein the template is configured to expose one or more portions of the strips, and wherein pressing the liquid adhesive onto one or more portions of the strips left exposed by the template disposes the pressed liquid adhesive onto at least the second end of each of the strips.

12. 12. The method of claim 11, wherein the template is configured to expose one or more portions of the strips, and wherein pressing the liquid adhesive onto one or more portions of the strips left exposed by the template causes the pressed liquid adhesive to be disposed on a top surface of the strips and a first end of the liquid adhesive disposed on the top surface of the strips to come into contact with the liquid adhesive disposed on the second end of each of the strips.

13. 13. The method of claim 12, wherein the template is configured to expose one or more portions of the strips, and wherein pressing the liquid adhesive onto one or more portions of the strips left exposed by the template causes the pressed liquid adhesive to be disposed on a top surface of each of the strips, with a second end of the liquid adhesive disposed on the top surface of the strips being disposed on top between the first end of the liquid adhesive in contact with the liquid adhesive disposed on the first end of each of the strips, and the liquid adhesive disposed on the second end of each of the strips.

14. The method of claim 1 , further comprising partially setting one or more of the adhesives.

15. The method of claim 14 including disposing one or more of the singulated dies on a suspension.

16. The method of claim 15 further comprising allowing the one or more adhesives to harden.

17. The method of claim 1 including disposing a second wafer of piezoelectric material over said first wafer of piezoelectric material.

Images