JP2020077878A - Method for manufacturing piezoelectric microactuator having wraparound electrode - Google Patents

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

(Cross reference of related application)
This application claims priority to US Provisional Patent Application No. 62 / 758,471 filed November 9, 2018, and US Patent Application No. 16 / 669,251 filed October 30, 2019. , All of which are incorporated herein by reference.

(Technical field)
The present invention relates to the field of suspensions for hard disk drives. More specifically, the present invention relates to a method of manufacturing a piezoelectric microactuator with wraparound electrodes for use in a two-step actuation (DSA) disk drive suspension.

  Other types of rotating media drives such as magnetic hard disk drives and 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 is applicable. A prior art disk drive unit 100 includes a rotating magnetic disk 101 containing magnetic 1 and 0 patterns that make up disk drive storage data. The magnetic disk is driven by a drive motor (not shown). The disk drive unit 100 further includes a disk drive suspension 105, and a magnetic head slider (not shown) is mounted on the suspension 105 near the distal end of the load beam 107. The suspension 105 is connected to an actuator arm 103, and the actuator arm 103 is connected to a voice coil motor 112 that operates the suspension 105 in an arc shape in order to arrange a head slider on an appropriate data track of the data disk 101. The head slider is held by a gimbal, which allows the slider to sway back and forth and to the left and right so that the slider follows the appropriate data tracks on the rotating disk, causing disk vibrations, inertia events such as bumping, and disk surface Changes such as irregularity are allowed.

  One-stage actuated disk drive suspensions and two-stage actuated (DSA) suspensions are known. In the one-stage actuated suspension, only the voice coil motor 112 moves the suspension 105.

  The DSA suspension, like many others, such as US Pat. No. 7,459,835 issued to Mei et al., Allows a magnetic head slider to be slightly moved in addition to a voice coil motor to move the entire suspension. At least one microactuator is disposed on the suspension for proper alignment above the data tracks of the rotating disk. Microactuators provide finer control of servo control loops and higher bandwidth than voice coil motors alone, which only operate the suspension, or magnetic head slider, relatively large. Piezoelectric elements, sometimes simply referred to as PZTs, are often used as microactuator motors, although other types of microactuator motors are possible. In the following description, the microactuator is simply referred to as "PZT" for simplicity, but it will be understood that the microactuator need not be of PZT type.

  FIG. 2 is a top view of the prior art suspension 105 in FIG. The two PZT microactuators 14 are attached to a suspension 105 on a microactuator mounting shelf 18 formed in the base plate 12 such that the PZT bridges each gap in the base plate 12. Microactuator 14 is attached to mounting shelf 18 by a non-conductive epoxy 16 at each end thereof. Positive and negative electrical connections can be made from the PZT to the flexible wire traces of the suspension and / or the grounded baseplate by various techniques disclosed in co-owned US Pat. No. 7,751,153 to Kulangara et al.

  When assembling a DSA suspension, this process typically involves applying a liquid adhesive such as epoxy over the suspension and / or PZT, placing the PZT in place on the suspension, and typically heat curing. Curing the adhesive by 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.

  FIG. 3 shows a prior art technique for joining two PZTs in a DSA suspension that includes an electrical connection between the two PZTs. Figure 3 is not admitted as prior art within the legal meaning of the term "prior art". Similarly, the process described herein as applied to FIG. 3 is not admitted as "prior art" within the legal meaning of the term "prior art". 4 and 5 are cross-sectional views taken along section lines C-C 'and D-D' of FIG. 3, respectively, showing details of the joint. As best shown in FIG. 4, the PZT 330 has electrodes on both sides, one end of the bottom electrode is grounded by a conductive epoxy 324 through gold 326 on a grounded stainless steel 328 layer and the other end is non-conductive. Insulated by a conductive epoxy 320. As best shown in FIG. 5, the top electrode is connected to a copper electrical contact pad 316 by a conductive epoxy 322 over a non-conductive epoxy 320, the electrical contact pad 316 being a suspension electrical interconnect or flexible circuit. And is insulated from the stainless steel substrate 312 by an insulating layer 314 such as polyimide. The electrical contact pads 316 provide the drive voltage for the PZT 330. The non-conductive epoxy 320 mainly mechanically bonds between the PZT 330 and the stainless steel substrate 312. In general, 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 is time consuming and expensive. Also, the bottom electrode and top electrode epoxies require two separate curing steps.

  Conventional methods of joining PZT to suspensions have drawbacks. Due to liquid adhesive flow and other issues, it is difficult to precisely control the amount of epoxy that the adhesive will ultimately be applied to. Various solutions have been proposed, including, for example, channels under the PZT that control adhesive flow and keep excess liquid epoxy away from sensitive areas. For example, US Pat. No. 6,856,075 to Hook discloses a method for controlling the movement or flow of adhesive by limiting or affecting the movement of the adhesive while at the same time preventing excessive adhesive fillet height adjacent to the piezoelectric motor. To control the flow, an adhesive attachment has been proposed that has one or more reliefs below or partially below or adjacent to the PZT transducer. Furthermore, when the PZT is placed at or near the gimbal that carries the magnetoresistive read / write head, the difference in adhesive flow and distribution from part to part affects shape, mechanical properties, and suspension performance results. Therefore, it is important to be able to predict and control the flow of adhesive. These problems are especially pronounced when the PZT is located in a particularly sensitive portion of the suspension, such as at or near the gimbal head slider. Reproducibility and predictability are of particular importance in the field. In addition, the presence of liquid epoxy and its dispenser in the final assembly chamber is both a potential source of contamination and an additional expensive manufacturing step.

  Another drawback of conventional attachment means is the delay in assembly time required for epoxies, including both conductive and non-conductive epoxies, to be applied and cured multiple times. FIG. 6 illustrates a typical manufacturing process for a PZT attachment that applies liquid epoxy to the PZT, interconnect, and / or load beam prior to mounting the PZT. Conductive epoxy is applied at the interconnect (610) and non-conductive epoxy is applied at the load beam or elsewhere on the PZT (612). The PZT is attached to the suspension (614) and the epoxy is cured in the first curing step (616). The conductive epoxy is then reapplied (618) and cured in a second curing step (620).

  SUMMARY OF THE INVENTION To address the aforementioned and other disadvantages of conventional assembly processes, the present invention is directed to other types of adhesives than those conventionally used for DSA suspensions, and to conventional DSA suspensions. Adopt steps other than the joining and curing steps used in.

  In one aspect, the invention employs an adhesive film between the PZT and the suspension, and / or the PZT of a liquid or pasty adhesive, such as epoxy, before the PZT is placed on the components of the suspension. Partial curing (B stage) is adopted. The suspension component to which the PZT is attached may be a base plate as shown in FIGS. 1 and 2 in the case of a base plate on which a microactuator is mounted. If the actuator, suspension load beam, and PZT are arranged, the head slider itself may be arranged. In the case of a mounted flexure, it may be a flexure as shown in FIGS. 3-5, or other suspension component with a microactuator mounted. After mating the two parts, the epoxy or other adhesive is finally cured. Curing may be heat curing, UV curing or other curing methods.

  In a second aspect of the invention, the invention is a method of manufacturing a PZT microactuator or other electronic device having wraparound electrodes, and methods of applying and using such a device. The wraparound electrode is a conductive paint that surrounds at least a portion of the PZT so as to cover multiple surfaces of the PZT and conducts electricity to the opposite surface. The wrap-around electrode simplifies both the assembly process and the final electrical connection to the PZT within the finished suspension. According to that method, the central electrode is first formed on the first surface of the wafer of piezoelectric material by sputtering or the like. Then, the first side electrode extends to the first side, but is not electrically connected to the central electrode on that side, ie, is discontinuous, so that the first side electrode is the first side or edge of the wafer. Formed above the portion and the adjacent edge. Similarly, the second side electrode is formed on the second side surface or the end opposite to the first side surface so that the second electrode extends to the first surface, but is electrically discontinuous with the central electrode, The second electrode extends above the adjacent edge. Next, a conductive material is deposited on the second surface of the wafer opposite the first surface by sputtering or the like, and the conductive material extends to the first and second side electrodes and makes electrical contact. The wafer has one central electrode and two side electrodes on the first surface, which covers most of the first surface, and each side electrode covers not only each side surface but also the side surface thereof. And at least a respective portion of the second surface, preferably each narrow strip on the first surface on opposite sides of the central electrode. Then cut the wafer in half. As a result, the two piezoelectric devices have wraparound electrodes such that the first surface includes both electrodes. Therefore, a drive connection and a ground connection can be made on the first surface of the PZT, which can simplify the electrical connection to the PZT.

  The present invention simplifies the assembly process of the DSA suspension and eliminates the delicate final suspension assembly source of contamination.

  Exemplary embodiments of the invention are further described below with reference to the drawings, wherein like reference numerals indicate like parts. Graphics may not be to scale and certain elements may be displayed in a generalized or a generalized form, which is commercially designated for clarity and brevity.

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

  A first aspect of the invention is the use of an adhesive film to attach the PZT to the suspension. FIG. 7 shows the method. A conductive epoxy is applied at the interconnect (710). An integral adhesive film, or PZT with 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 PZT with an integral adhesive film. PZTs with integrated adhesive films can be manufactured using laminated adhesive films at the PZT wafer level or by printing or wafer backside coating processes used in the semiconductor industry. Since the adhesive film is attached to the PZT at the wafer level before dicing into individual PZT dies, it can realize process simplification and cost reduction. It is also feasible to tightly control the thickness of the adhesive. As shown in FIG. 7, the use of PZT with integral adhesive simplifies the process compared to FIG. The step of applying a non-conductive epoxy with a load beam is eliminated using the method of the present invention.

  A suspension design that facilitates the use of a one-piece adhesive film is shown in FIGS. FIG. 8 is a perspective view of a DSA suspension without flexure gimbal assembly for clarity of illustration, according to one embodiment of the present invention that employs a pattern printed on an integral adhesive film or PZT. The PZT 830 is attached to the suspension component to be mounted, in this case the base plate 812. The driving of the PZT moves the load beam 820 so that the head slider arranged at the distal end of the load beam moves in the radial direction.

  FIG. 9 is an exploded view of the suspension of FIG.

  FIG. 10 is a perspective view of one of the PZT 830 of the suspension 810 of FIG. 8, showing an integral adhesive film or printed adhesive 834, 836 below. In this embodiment, the integrated adhesive films 834, 836 located at both ends of the PZT 830 are provided by applying an adhesive film or printing an adhesive pattern on the PZT wafer before dicing and singulating the individual PZTs. It is formed. The exposed PZT surface between the adhesives electrically connects the electrical circuit of the liquid epoxy to the suspension.

  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 upper surface of the PZT 1130 to bond the PZT to the recess of the base plate 1112. Be seen.

  FIG. 12 is a perspective view of the PZT of FIG. In this design, an integral adhesive film or printed adhesive 1134 is placed on top of the PZT. Since the integral adhesive film partially covers the entire top surface or the entire top surface, patterning of the adhesive is not required. Also, a conductive film can be used in this design so that when the PZT is attached to the base plate, grounding through the base plate can 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.

  The adhesive film 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 is desired. Film adhesives are generally "preformed" or "B-staged" and are available in roll, sheet, or die cut form.

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

  As used herein, the term "B-staging" or "B-staging" means that after the flowable adhesive has been applied, it causes the adhesive to partially solidify so that its flow is no longer freely flowing as a liquid. It is substantially reduced to the point of disappearing, but is not so stiff that it is no longer available for effective adhesion to other surfaces. B-staging involves exposing the adhesive temporarily to an environment that accelerates the setting of the adhesive and removing it from the environment so that the curing rate is significantly reduced so that the adhesive does not substantially set during assembly. To do. Removing PZT from an environment with accelerated solidification can simply include removing the cure accelerator from the environment. B-staging can cure or solidify the adhesive to the extent that the adhesive is no longer tacky. One of the B-staging methods is to partially cure the cross-linked polymer such as epoxy by heat and / or UV so that the epoxy adhesive is cross-linked to 10% or less, and then remove the cure source. In the case of thermally B-staged epoxies, the epoxies are immediately quenched to a temperature so low that the crosslinking is negligible, that is, the epoxy does not solidify effectively, in order to stop the crosslinking process. In the case of UV B-staged epoxies, removing the PZT from the accelerated cure environment may simply mean turning off the UV cure lamp.

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

  B-staging adhesives allow the adhesive and substrate structure to be "staged" or held for a period of time before bonding and curing without loss of performance. The second heat cure cycle results in a fully crosslinked void-free bond. The term "fully crosslinked" as used herein means at least 90% crosslinked.

  The adhesive may take the form of a solid, thermosetting paste. The adhesive may be a printable paste 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 a printing technique is that the adhesive can be applied on the PZT in a very fine and precise pattern, which allows control and reproducibility of the total mass and distribution of the adhesive in the finished suspension. realizable. One commercially available silver-containing conductive epoxy suitable for fluid jetting, stencil printing, and stamping is EPO-TEKH20E from Epoxy Technology.

  UVB stage adhesives can be used. Such an adhesive is applied and irradiated with UV energy for B-stage. Immediately after printing, B-staging allows the adhesive to "freeze" in place and the spread of the liquid epoxy to be accurately controlled.

  The liquid epoxy or other adhesive may be applied first on the PZT and / or the suspension, after which the epoxy is B-staged to the point that its flow is negligibly reduced. The parts can be finally assembled in a clean room assembly area for the disk drive, after which the adhesive is fully cured with either heat or UV. Such techniques are 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 can be applied from the die attach process used in IC packaging to the PZT attach process for suspensions. Inkjet printing of polymers for both conductive and non-conductive adhesives has also been proposed. Such inkjet printing techniques can be adapted for use in printing adhesive on PZT to bond the PZT to the suspension.

  One method of manufacture begins with a wafer of PZT material and either applies the adhesive to the wafer in the form of an adhesive film, which has already been B-staged, or applies the adhesive to the wafer and then B-stages the wafer, then It is expected to be dicing into individual PZT microactuator motors. Using a pick-and-place machine, pick up individual PZT dies with B-staged adhesive, assemble the PZT dies into a suspension, and time and temperature to fully cure the adhesive. And allow the PZT to adhere completely to the suspension under pressure conditions.

(Wrap-around electrode)
In another aspect, the invention is a method of making a piezoelectric microactuator or other electronic device having wraparound electrodes such that both the driving voltage and the ground electrode are located on the same side of the device and are accessible.

  FIG. 13 is a side sectional view of a PZT according to an additional aspect of the present invention. The PZT 1330 has a bottom electrode 1334 and a "wrap around" electrode 1336 to simplify electrical connection to the PZT. In this embodiment, the upper electrode 1336 is wrapped around the PZT on one end of the lower PZT surface. Therefore, the drive voltage is applied to the bottom surface of the PZT at the first end and the electrical ground is connected to the bottom surface of the opposite end. Therefore, both electrodes 1334, 1336 can be electrically connected on the same side or side of the PZT by conductive epoxies 1340, 1342, respectively. This reduces the number of epoxy bonding steps to two, making it difficult to control the epoxy height tolerance on top of the PZT surface. Moreover, only a single curing step is required.

  FIG. 14 is a flow diagram of a manufacturing process that uses conventional epoxy coating and bonding steps to attach the PZT to the suspension as shown in FIG. First, a conductive epoxy is applied for ground (1410). Thereafter, a non-conductive epoxy is applied for insulation (1412). Then, in step 1414, the PZT is attached to the suspension. The epoxy is then cured (1416). Then, a second epoxy coating step is performed (1418). Finally, the last applied epoxy is cured (1420). This process required two separate curing steps.

  FIG. 15 is a flow chart of the manufacturing process according to the present invention for joining the PZT to the suspension as shown in FIG. A conductive epoxy is applied (1510) for grounding. A conductive epoxy is then applied (1512) for the signal or drive voltage. The PZT is then attached to the suspension (1514). Finally, the assembly is cured (1516). The figure shows the simplification obtained by using PZT with wrap-around electrodes according to the invention.

  19-21 illustrate the preparation and placement of a PZT with a B-staged adhesive according to the present invention. FIG. 19 is a perspective view of a PZT 1930 with adhesives 1920, 1924 applied to what is on the bottom of the PZT 1930. Generally, the adhesive can be applied by any one of many known techniques, including screen printing, stencil printing, inkjet printing, spraying, application as a film, and the like. Any pattern generally desired for a combination of conductive and / or non-conductive adhesive may be applied to PZT1930. In the illustrated embodiment of the 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 thickness, one strip being thicker than the other.

  FIG. 20 is a top perspective view of a PZT 1930 with a B-staged adhesive. In the figure, the epoxy strips 1920, 1924 are B-staged by UV. In general, the adhesive 1920, 1924 can be B-staged using any known technique, including thermal B-staging and UV B-staging. Further, the two strips of adhesive 1920, 1924 can be B-staged to different extents, leaving one strip harder or more solidified than the other. In UV curing, a mask or screen can be used to illuminate one strip more than the other.

  FIG. 21 is a side cross-sectional view of PZT1930 after it has been applied to the suspension. FIG. 21 is similar to FIG. 3 and shows how the present invention can simplify conventional processes. After the PZT 1930 is in place, pressure is applied at least to the left side of the PZT to push the non-conductive epoxy 1920 into the gap between the PZT and the polyimide layer 314 and adjacent the PZT. Cover the previously exposed stainless steel 312. The pressure may be applied mechanically on the PZT. Alternatively, the weight of the PZT itself may provide sufficient force and pressure to force the non-conductive epoxy 1920 into the gap depending on how much solidification occurred during the B-stage process. After the PZT is placed and optionally depressed, the conductive epoxy 322 fills the gap between the metallized top surface of the PZT that defines the drive electrode and the copper contact pad 316 that supplies the drive voltage to the PZT. Is applied. Thereafter, all epoxies in the assembly are simultaneously cured in a single curing step. This process eliminates the need for a second curing step as was required for the assembly and process of Figures 3-6.

  FIG. 21 is just one of various types of electrical connections and methods for providing PZT drive voltage and ground to the PZT. Many other connection types and methods are possible, such as those disclosed by Schreiber, US Pat. No. 8,189,301, and Kulangara, US Pat. No. 7,751,153. The present invention is applicable to suspensions that employ various types of electrical connections to PZT.

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

  16A-16G show the manufacturing steps for making a PZT with the wraparound electrode shown in FIG. First, the PZT block or wafer 1630 is placed on the transfer tape 1602 with the PZT bottom surface 1631 facing down (FIG. 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 on the top surface (FIG. 16B). The mask leaves the PZT surface strips 1606 unmetallized. The kerf 1608 is then cut into the PZT wafer, separating the first portion, called the PZT precursor 1632, from the rest of the wafer (FIG. 16C). The second mask 1612 is placed over the PZT precursor 1632 and additional metallization 1605 is sputtered onto the kerfs on the sides of the PZT precursor 1632 in the kerf 1608 to render those sides conductive and adjacent the kerf. To be electrically continuous with the top metallization of the PZT (FIG. 16D).

  The PZT precursor 1632 is then flipped over and preferably placed on the second transfer tape to expose what was the bottom surface 1631 of the PZT precursor (FIG. 16E). The bottom surface 1631 continues to be called the bottom surface even if it is currently facing upward. A metallization layer 1614 is then sputtered over the bottom surface 1631 of the PZT precursor (FIG. 16F). Finally, a new cut 1616 is made in the PZT, the first PZT is separated in approximately half, and what is called the first PZT1634 and the second PZT1636 are defined (FIG. 16G).

  As a result of this process, the two PZTs 1634, 1636 each have the same structure. The upper surface 1633 of the first PZT and the narrow stripe 1650 of metallization near its edges define the 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 side surface 1605 of the metallized PZT. The 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 way, the first PZT in which the first electrode 1650 is arranged on the same surface of the first PZT as the second electrode 1652 is constructed. 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.

  17A and 17B are isometric views of a PZT wafer at selected steps during the manufacturing process of the present invention. 17A is an isometric view of PZT strips 1634, 1636 at the end of the process of FIG. The PZT is now ready for polarization and the final dicing operation is done to produce the individual PZT as shown in Figure 17B. As a result, both the first row 1638 of PZT and the second row 1640 of PZT have wraparound electrodes.

  18A-18G show an alternative form of manufacturing process for making a PZT with wraparound electrodes. The PZT wafer 1830 is placed on the transfer tape 1802 so that the bottom surface 1831 faces downward (FIG. 18A). The kerf 1808 is then cut into the PZT 1830 to separate the 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 of copper, silver, or other conductive material or particles (FIG. 18C). Silver epoxy is one of the commonly used materials and is used as an example. Thereafter, the silver epoxy 1820 is solidified. Next, a suitable mask is placed over the top surface of the PZT precursor 1832 and a metallization layer 1804, such as aluminum metallization, is sputtered on the top surface (FIG. 18D). The mask prevents metallization along the two narrow strips 1806, 1807 on the top surface of the PZT precursor near the edges. As a result, 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 region 1846 approximately in the center of the PZT precursor. At this point in the process, each stripe 1842, 1844 of metallization near the edge of the PZT precursor is electrically connected to the silver epoxy 1820 on the edge of the PZT precursor where the stripe is adjacent to the metallization of the metallization. The two stripes 1842, 1844 and the large central metallization region 1846 are all electrically isolated from each other or electrically discontinuous.

  The PZT precursor is then flipped over and preferably placed on a second transfer tape to expose what was the bottom surface 1831 of the PZT precursor (FIG. 18E). The bottom surface 1831 continues to be called the bottom surface even if it is currently facing upward. A metallization layer 1814 is then sputtered over the bottom surface of the PZT precursor (FIG. 18F). Finally, a new cut 1818 is made in the PZT precursor, the PZT precursor is cut in approximately half, and another cut 1816 is made via silver epoxy. This splits the PZT precursor in approximately half, defining what are called the first PZT and the second PZT (FIG. 18G). The cut 1816 is within the kerf 1808 and is narrower than the kerf 1808 to leave the sides of the PZT precursor covered with conductive silver epoxy 1820 and acts as an electrical bridge or wraparound from the top to the bottom of the PZT.

  As a result of this process, the two PZTs each have the same structure. A top surface 1833 of the first PZT and a narrow metallization stripe 1844 near its edge define a first electrode. The first electrode 1844 electrically surrounds the bottom surface 1831 of the PZT and the metallization that substantially covers the bottom surface 1831 via the silver epoxy 1820. In this way, a first PZT is constructed in which the first electrode 1844 is located on the same surface of the first PZT as the opposite electrode 1852. The second PZT is substantially the same as the first PZT.

  FIG. 22 is a side cross-sectional view of a PZT having wraparound electrodes such as the PZT shown in either FIG. 16 or FIG. 18 after suspension coating. The PZT 1830 has a first electrode that functions as a drive electrode or a positive electrode, a wraparound electrode 1844, and a second electrode 1852 that functions as a ground electrode. Drive electrode 1844 is bonded via conductive epoxy 1924 to copper contact pads 316 on polyimide layer 314 above stainless steel substrate 312. The ground electrode 1852 is grounded to the stainless steel substrate 328 via the gold bond pad 326 and the conductive epoxy 1928. A strip of conductive epoxy 1924 and 1928 can be the B-staged epoxy described above, with the epoxy 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 eliminates any liquid or pasty epoxy from that room, thereby helping to maintain a pollution free environment. ..

(Die attach adhesive)
The conventional approach to PZT bonding used liquid epoxy in the manufacturing process. The use of liquid results in unnecessary and inconsistent extrusion. If the amount of liquid adhesive extruded is not constant, the adhesive will flow beyond the interconnect area. In addition, unwanted adhesive splatters on other areas or other parts of the suspension. Each of the above summaries can adversely affect PZT and suspension performance. In some cases, a non-constant amount of adhesive can lead to PZT and / or suspension failure.

  23A-23D illustrate a process for making a die attach adhesive at the PZT wafer level according to one embodiment. After printing the adhesive on the PZT wafer, a drying or B-stage process, such as the process described herein, is performed to transform the adhesive into a semi-solid state. As a result, in the PZT, the adhesive is incorporated on the side wall and bottom surface of the PZT, and the size and thickness of the adhesive can be finely controlled. The PZT can then be bonded onto the suspension by a heat or curing process. Since the adhesive film is attached to the PZT at the wafer level before dicing into the individual PZTs, simplification of the process and cost reduction can be realized. In addition, more control over the position of the adhesive with the embodiments described herein may result in more consistent performance results and yields for PZT and PZT-incorporated suspensions.

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

  FIG. 23B illustrates a strip of PZT wafer with adhesive printed on the strip, according to one embodiment. The die attach adhesives 2304a-d are placed on the strips 2302a-c of the PZT wafer 2301. In some embodiments, the die attach adhesive 2304a-d is formed on a top portion of the strip 2302a-c adjacent the edge. Further, the die attach adhesives 2304a-d are disposed on the side surfaces of each strip 2302a-c. In some embodiments, the die attach adhesives 2304a-d are formed on the strips 2302a-c using screen printing. For example, the screen containing the pattern is placed over the PZT wafer 2301 and the liquid adhesive is applied to the screen, preventing the liquid adhesive from being placed except the portion of the PZT wafer that is exposed in the pattern. The liquid adhesive is placed on the screen and pressed onto the exposed portion 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 located on PZT wafer 2301 matches the design required for the suspension. Other methods of placing the liquid adhesive 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.

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

  FIG. 23D illustrates a cross-sectional view of a singulated PZT die that includes an adhesive according to one embodiment. According to some embodiments, adhesive 2304 is disposed on PZT wafer 2301 such that portions 2308 of adhesive 2304 are formed on at least two sides of PZT die 2306. For example, the portion 2308a is formed on the first side surface of the PZT die 2306 and a part of the bottom surface. Portion 2308b is formed on the second side of PZT die 2306 opposite the first side and includes a portion on the bottom surface of PZT die 2306. In some embodiments, the portion 2308 of the adhesive 2304 is formed on the sides of the PZT die 2306 and a portion on the top surface. The process described above allows more control over the size and thickness of the adhesive deposited 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 can be caused by adhesive splattering and overfilling.

  FIG. 24 shows a cross-sectional view of a PZT die attached to a suspension, according to one embodiment. As shown, for example, a singulated PZT die 2406 formed using the techniques described herein may be a base plate formed from a base plate 2412 as described herein, or a microactuator mounted. It is arranged in the recess of the shelf 2418. In some embodiments, microactuator mounting shelf 2418 is formed from a load beam coupled to base plate 2412. In another embodiment, the mounting shelf 2148 is a structure separate from the load beam attached to the base plate 2412. The singulated PZT die 2406 including the adhesive 2408 is formed on two sides of the singulated PZT die 2406 using techniques including those described herein. An adhesive portion 2408a is disposed on the first side of the singulated PZT die 2404 and is configured to contact and adhere to the first edge 2410a of the base plate 2412 and the first shelf 2148a extending from the mounting plate. It Similarly, the portion 2408b is on the side of the singulated PZT die 2406 opposite the portion 2408a and contacts and adheres to the second edge 2410b of the base plate 2412 and the second mounting shelf 2418b extending from the mounting plate. To be configured. The adhesive is attached to the suspension portion with which it is in contact using techniques including those described herein. Since the singulated PZT die 2406 already has an adhesive disposed on it, the process of mounting the singulated PZT die 2406 is dependent on the adhesive used to mount the microactuator on the suspension. Since it is not applied, it eliminates the adhesive from splattering into another part of the suspension, or spilling into a part of the suspension, and causing deleterious changes or failures in the performance characteristics of the suspension. According to an embodiment, when a singulated PZT die containing B-staged adhesive is placed on the suspension, the adhesive is completely removed using techniques including those described herein. Hardened to. In some embodiments, at least one or more portions of the suspension are in contact with an adhesive disposed on a singulated PZT die according to embodiments herein, and the one or more portions of the suspension are in contact. Chamfered or beveled to have better contact with.

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

  FIG. 26 illustrates one embodiment of a singulated PZT die 2606 that includes another portion of adhesive disposed between a first portion 2608a of adhesive and a second portion 2608b of adhesive. As shown in FIG. 26, a third portion 2608c of 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. One or more optional portions of the adhesive may be conductive or non-conductive adhesive. Each type of adhesive is deposited on the singulated PZT die 2606 using techniques including those described herein. As shown in FIG. 26, embodiments include the first portion 2608a and the third portion 2608c of the adhesive being conductive adhesive and the second portion 2608b of the adhesive being non-conductive adhesive. The first portion 2608a and the third portion 2608c as conductive adhesives are each singulated to provide a drive signal or ground connection to, for example, one or more electrodes of the singulated PZT die 2606. Configured to form an electrical connection between the PZT die 2606 and the contacts.

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

  FIG. 28 illustrates a fragment of a two-stage actuated suspension including two singulated PZT dies 2806, according to an embodiment having a flexure-mounted microactuator utilizing the methods and structures described herein.

  FIG. 29 shows a cross section of a multi-layered PZT die with an adhesive according to one embodiment. The multi-layer singulated PZT die 2901 comprises two layers of PZT wafer material. The multi-layer singulated PZT die 2901 includes a plurality of electrodes 2904. First PZT wafer 2902 is formed using techniques including those described herein. The second PZT wafer 2906 is arranged 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 placed is at least partially metallized to form intervening electrodes 2904b using techniques including those described herein. It PZT wafers 2902, 2906 are metallized to form electrodes 2904a, c using techniques including those described herein. Other embodiments include more than one PZT wafer and a plurality of intervening electrodes. PZT wafers 2902, 2906 are diced to form a multi-layer singulated PZT die 2901 using techniques including those described herein.

  According to some embodiments, the adhesive is a PZT wafer such that each portion 2908 of the adhesive is formed on at least two surfaces of PZT die 2901 using techniques including those described herein. 2902, 2906. For example, the portion 2908a is formed on the first side surface, and the portion 2908b is on the opposite side of the PZT die 2901 from the first side surface, and is formed on the second side surface including the portion on the bottom surface of the PZT die 2901. In some embodiments, portions 2308 of adhesive 2304 are formed on portions of the side and top surfaces of PZT die 2901. Other embodiments include a portion on the bottom surface of PZT die 2901. The process described above allows more control over the size and thickness of the adhesive deposited 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 can be caused by adhesive splattering and overfilling.

  All features disclosed in this specification, including the claims, abstract, and drawings, and all steps in any method or process of disclosure, are mutually exclusive in at least some of those features and / or steps. Can be combined in any combination, except the combinations that are Each feature disclosed in the specification, including the claims, abstract, and drawings, can be replaced by an alternative feature serving the same, equivalent, or similar purpose, unless explicitly stated. Thus, unless explicitly stated, each feature disclosed is only an example from a comprehensive set of equivalent or similar features.

  The terms "generally," "approximately," "about," and "substantially" as used in the specification and claims, refer to any precise dimension, measurement, and arrangement from any given dimension. It is understood that various degrees of variation are permissible and those terms need to be understood within the context of the description and practice of the invention disclosed herein.

  Terms such as "top," "bottom," "top," and "bottom," as used in the specification and claims, do not refer to each other in any particular spatial or weight direction. It is further understood that it is a convenient term that describes the spatial relationship of the part to. Thus, the term includes an assembly of parts whether or not the assembly is shown in the figures and oriented in the particular direction described in the specification, opposite that direction, or any other degree of rotation. Is intended.

It is recognized that the term "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 shown. .. Similarly, it is also understood that the term "present invention" includes many individual inventions, each of which can be considered an individual invention. Thus, the present invention has been described in detail with reference to the preferred embodiments and its drawings, but it is understood that various applications and modifications of the present invention can be made without departing from the spirit and scope of the present invention. Obvious in the technical field. For example, instead of selectively applying and partially curing the adhesive on the PZT, other suspension components such as flexures may be selectively applied and partially cured. Therefore, the foregoing detailed description and accompanying drawings are not intended to limit the scope of the present invention which is to be determined solely by the following claims and their properly understood legal equivalents. Be recognized.

Claims (23)

A method of manufacturing a microactuator, comprising:
Forming at least a first wafer of piezoelectric material that includes one or more electrodes;
Forming one or more strips of piezoelectric material from the first wafer of piezoelectric material;
Printing one or more adhesives on at least one surface of the strip of piezoelectric material;
Forming one or more singulated dies comprising one or more portions of at least one of any of the adhesives from the one or more strips of piezoelectric material. Method.   The method of claim 1, wherein forming the one or more strips of piezoelectric material from the first wafer comprises dicing the first wafer. Printing one or more adhesives on at least one surface of the strip of piezoelectric material comprises:
Placing a template above the strip;
Applying one or more liquid adhesives to the template;
Pressing one or more of the liquid adhesives onto one or more portions of the strip that are still exposed by the template.   The method of claim 3, wherein applying one or more of the liquid adhesives to the template comprises applying a non-conductive adhesive to the template.   The method of claim 3, wherein applying one or more of the liquid adhesives to the template comprises applying a conductive adhesive to the template.   The manufacturing method according to claim 3, wherein the one or more liquid adhesives include one of a conductive adhesive and a non-conductive adhesive.   Forming one or more of the singulated dies containing one or more portions of at least one of any of the adhesives from one or more of the strips of piezoelectric material is performed on one of the piezoelectric materials. The manufacturing method according to claim 1, comprising dicing the above strip.   The dicing of one or more strips of piezoelectric material comprises dicing one or more strips of piezoelectric material to include at least two portions of any of the adhesives. The manufacturing method described.   The template is configured to expose one or more portions of the strip, and when one or more liquid adhesives are pressed onto one or more portions of the strip that remain exposed by the template, 1 The method of claim 3, wherein at least one of the one or more liquid adhesives is disposed on at least the first end of each strip.   The template is configured to expose one or more portions of the strip such that pressing the one or more liquid adhesives onto one or more portions of the strip that remains exposed by the template results in 1 The method of claim 4, wherein at least one of the one or more liquid adhesives is disposed on the top surface of each strip.   The template is configured to expose one or more portions of the strip such that pressing the one or more liquid adhesives onto one or more portions of the strip that remains exposed by the template results in 1 At least one or more of the one or more liquid adhesives disposed on the upper surface of the strip and at least one of the one or more liquid adhesives disposed on the first end of each strip. The method of claim 9, wherein the method is contacted with the liquid adhesive of.   The template is configured to expose one or more portions of the strip such that pressing the one or more liquid adhesives onto one or more portions of the strip that remains exposed by the template results in 1 The method of claim 11, wherein at least one of the one or more liquid adhesives is disposed on at least the second end of each strip.   The template is configured to expose one or more portions of the strip such that pressing the one or more liquid adhesives onto one or more portions of the strip that remains exposed by the template results in 1 At least one of the one or more liquid adhesives is disposed on a top surface of the strip and a first end of the one or more liquid adhesives is disposed on the second end of each strip. 13. The manufacturing method according to claim 12, which is contacted with one or more of the liquid adhesives.   The template is configured to expose one or more portions of the strip such that pressing the one or more liquid adhesives onto one or more portions of the strip that remains exposed by the template results in 1 At least one of the one or more liquid adhesives is disposed on an upper surface of each strip and a second end of the one or more liquid adhesives is disposed on the first end of each of the strips One or more of said liquid adhesives in contact with at least one or more of said liquid adhesives and one or more of said liquid adhesives disposed on said second end of each strip. The manufacturing method according to claim 13, wherein the manufacturing method is arranged on the upper surface between   The method of claim 1, comprising partially solidifying one or more of the adhesives.   16. The method of manufacturing of claim 15, comprising placing one or more of the singulated dies in a suspension.   The method of claim 16, comprising solidifying one or more of the adhesives.   The method of claim 1, comprising disposing a second wafer of piezoelectric material on the first wafer of piezoelectric material. A microactuator,
A first portion of adhesive disposed on a first side of the microactuator;
A microactuator comprising a second portion of adhesive disposed on a second side of the microactuator.   20. The microactuator of claim 19, wherein the first portion of adhesive and the second portion of adhesive are partially cured.   20. The microactuator of claim 19, wherein the first portion of adhesive and the second portion of adhesive are disposed on at least two surfaces of the microactuator.   20. The microactuator of claim 19, wherein the third portion of adhesive is located on the surface of the microactuator between the first portion of adhesive and the second portion of adhesive. 20. The microactuator of claim 19, wherein the microactuator comprises multiple layers of PZT wafer material.