Apparatus and Method for Precision Component Positioning

Abstract

An actuator stage, for precision positioning of a component, includes a base layer having a surface defining a z-axis normal to the surface; a set of electro-fluidic transport substrates disposed on the base layer, and a control port, coupled to a plurality of sets of electrodes in each of the electro-fluidic transport substrates, configured to measure a tilt of a carrier layer relative to the base layer and change the tilt of the carrier layer.

Claims

1. An actuator stage, for precision positioning of a component, the actuator stage comprising: a base layer having a set of sectors defining spatial regions of the base layer and a surface defining a z-axis normal to the surface; a set of electro-fluidic transport substrates, disposed on the base layer, each of the substrates having: a plurality of sets of electrodes, each set located in a given sector of the base layer; a dielectric layer, disposed over each set of electrodes and having a hydrophobic surface; a fluidic layer disposed over the hydrophobic surface and including a first non-conductive fluid and a second conductive fluid, wherein the first and second fluids are immiscible; and a carrier layer having defined hydrophilic and hydrophobic regions in selected contact with the second conductive fluid and the first non-conductive fluid, respectively, configured in a manner so that appropriate powering of the electrodes effectuates motion of the carrier layer; wherein, corresponding capacitances are established between the carrier layer and each set of electrodes in a given sector; and a control port, coupled to the plurality of sets of electrodes, configured to (i) determine a differential between capacitances of at least two of the given sectors, a difference in capacitance indicating a tilt in the carrier layer relative to the base layer and (ii) apply voltages, to at least one set of electrodes, the voltage configured to move the carrier layer so as to (a) change the tilt of the carrier layer relative to the base layer, or (b) change a position of at least one component on the actuator stage with respect to the z-axis.

2. A method for precision placement of components onto a substrate, the method comprising: using a component placement system to pick up a first set of components; configuring the first set into a first desired spatial configuration by adjusting a position of each component of the first set of components; causing the component placement system to convey the first set of components to a first position over the substrate and to deposit the first set of components, in the first desired spatial configuration, on the substrate at the first position; using the component placement system to pick up a second set of components; configuring the second set into a second desired spatial configuration by adjusting a position of each component of the second set of components; and causing the component placement system to convey the second set of components to a second position over the substrate and to deposit the second set of components, in the second desired spatial configuration, on the substrate at the second position; wherein a given component of the deposited first set and a given component of the deposited second set are separated by a distance smaller than that of any given component of the first set of components in the first desired spatial configuration or the second set of components in the second desired spatial configuration.

3. A method for precision placement of a component onto a substrate, the method comprising: removably attaching the component to the component placement system; adjusting the position of the component on the component placement system into a desired first position by aligning a first set of fiducials on the component and a second set of fiducials on the component placement system using a first imager configured to image the first and second set of fiducials; and causing the component placement system to place the component on the substrate at a desired second position by aligning, using a second imager configured to image: (a) a set of fiducials selected from the group consisting of (i) the first set of fiducials, (ii) the second set of fiducials, and (iii) combinations thereof; and (b) a third set of fiducials on the substrate.

4. The method of claim 3, wherein the first imager and the second imager are the same imager.

5. The method of claim 3, wherein at least one of the imagers is an IR imager.

6. The method of claim 3, wherein at least one of the imagers is a visible spectrum imager.

7. The method of claim 3, wherein at least one of the imagers is a multi-imager module.

8. A method for precision placement of a component onto a substrate, the method comprising: removably attaching the component to the component placement system; adjusting the position of the component on the component placement system into a desired first position by aligning a first set of fiducials on the component and a second set of fiducials on the component placement system using a first imager configured to image the first and second set of fiducials; causing the component placement system to place the component onto an intermediate structure; inverting the intermediate structure; aligning the component to a desired position on a destination substrate using: (i) a second imager configured to image the first set of fiducials and a third set of fiducials on the destination substrate; or (ii) a global encoder; and causing the intermediate structure to place the component onto the destination substrate at the desired position.

9. The method of claim 8, wherein the intermediate structure is a temporary bonding wafer.

10. The method of claim 8, wherein the first imager and the second imager are the same imager.

11. The method of claim 8, wherein at least one of the imagers is an IR imager.

12. The method of claim 8, wherein at least one of the imagers is a visible spectrum imager.

13. The method of claim 8, wherein at least one of the imagers is a multi-imager module.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The foregoing features of embodiments will be more readily understood by reference to the following detailed description, taken with reference to the accompanying drawings, in which:

[0028] FIG. 1A is a vertical section view of the head 101 of an actuator stage in accordance with an embodiment of the present invention.

[0029] FIG. 1B is a perspective rendering of some of the actuator stage components of FIG. 1A.

[0030] FIG. 1C is an exploded view of the layers shown in FIG. 1B.

[0031] FIG. 2A is a vertical section of one embodiment of a functional cell of an electro-fluidic transport substrate 201 in accordance with an embodiment of the present invention.

[0032] FIG. 2B is an enlarged view of the right end corner of the droplet 204 of FIG. 2A.

[0033] FIG. 2C is an equivalent circuit diagram of the electronic components shown in FIG. 2A.

[0034] FIG. 3A illustrates the mechanism of position control for a functional cell of the electro-fluidic transport substrate 201 of FIG. 2A.

[0035] FIGS. 3B, 3C, 3D, 3E, and 3F illustrate an example of position control, in accordance with an embodiment of the present invention, using an external capacitance switching arrangement. FIG. 3G illustrates an example of position control using a voltage source to set phase charges directly, in accordance with an embodiment of the present invention.

[0036] FIG. 4 is a vertical section of a system 401, in accordance with an embodiment of the present invention, using a combination of a plurality of functional cells, of the type shown in FIGS. 2A, 2B, 2C and 3A, in a manner to provide a single layer of a larger system, where the forces from each of the droplets are combined to make a stronger actuator.

[0037] FIG. 5 is a vertical section of a stack of layers, in accordance with an embodiment of the present invention, wherein each layer is of the type shown in FIG. 4, and stacked in the same orientation as each other layer.

[0038] FIG. 6 is a vertical section of a stack of layers, in accordance with an embodiment of the present invention, wherein each layer is of the type shown in FIG. 4, and stacked with adjacent pairs which are oriented back-to-back.

[0039] FIG. 7 is a vertical section of a stack of a plurality of layers, in accordance with another embodiment of the present invention, again wherein each layer is of the type shown in FIG. 4, and wherein the spatial frequency of electrodes is different in each layer and configured to provide vernier adjustment of position.

[0040] FIGS. 8A and 8B are diagrams of linear and circular patterns, respectively, of the array of electrodes in an electro-fluidic transport substrate, in accordance with embodiments of the invention.

[0041] FIGS. 9A and 9B are top views of an x/y stator layer 131 and an x/y translation layer 133, respectively, of the type shown in FIG. 1A-C, in accordance with embodiments of the invention. FIG. 9C is a top view of a set of x/y translation layers 133 interlaced with a set of x/y stator layers 131, in accordance with embodiments of the invention. FIG. 9D is a vertical section of the set of x/y translation layers 133 interlaced with the set of x/y stator layers 131 shown in FIG. 9C, in accordance with embodiments of the invention.

[0042] FIGS. 10A and 10B are top views of an x/y stator layer and an x/y translation layer, respectively, assembled in an alternate configuration of the push-pull system, in accordance with one embodiment of the invention.

[0043] FIGS. 11A, 11B, and 11C are views corresponding to FIGS. 9A, 9B, and 9C, respectively, but in this case showing an embodiment of the rotational stage layers.

[0044] FIG. 12A is an exploded perspective view of an embodiment including a plurality of actuator stage 101 of the type shown in FIG. 1B, here are arranged in a grid, in accordance with embodiments of the invention.

[0045] FIG. 12B is a cut-away view of the embodiment of FIG. 12A, revealing layer arrangements of two actuator stages, in accordance with embodiments of the invention.

[0046] FIGS. 12C, 12D, and 12E show an actuator stage 101 with a head extension on the top of die-handling head 1215 for vacuum connection, with a plurality of actuator stages in FIGS. 12D and 12E, in accordance with another embodiment of the present invention. The end of die-handling head 1215 can be firm or conformable and adapted for handling a variety of workpieces, including those with curved surfaces, such as microlenses.

[0047] FIG. 13 is a schematic showing an actuator stage 101 with a control box 108 configured to measure capacitances of the actuator stage to determine the position of a translation layer relative to a corresponding stator layer, in accordance with embodiments of the invention. FIG. 14 shows a component die with alignment fiducials on a facet facing the substrate, wherein these fiducials are used to position the die with respect to the actuator stage in accordance with an embodiment of the present invention.

[0048] FIG. 15 illustrates an embodiment in which alignment fiducials 1501 on the die placement system 1502 and alignment fiducials 1503 on the substrate 1504 are used to align the die placement system to the substrate.

[0049] FIG. 16 shows an embodiment in which a plurality of linear stages are stacked on top of each other in a long-range linear motion stage 1601 to achieve a higher speed movement over a distance.

[0050] FIG. 17 is a side view of a die placement system 1702 receiving component dies 1704 from component feeder 1703 and moving via global gantry system 1701 to allow placement of component dies 1704 on substrate wafer 1710 (equivalent to, and used herein interchangeably with, substrate 1504) in accordance with an embodiment of the invention.

[0051] FIG. 18 is a side view of a die placement system 1702, here illustrated as receiving component dies 1704 from the multi-chip-transfer-module 1803; aligning the dies 1704 with imaging feedback provided by the multi-imager-module 1806; and bonding the dies 1704 to the target substrate/wafer 1710 with the target-bonding-module 1812, all in accordance with an embodiment of the invention. Multi-imager module 1806 may comprise a plurality of imagers, up to as many imagers as there are actuators, but no less than one imager. A multi-imager module 1806 having less imagers than there are actuators may acquire images and move in a systematic pattern, thereby scanning all actuator positions in a die placement system.

[0052] FIG. 19 is a flow-chart of a command sequence that may be executed by control box 1720 to cause performance of the die placement steps illustrated in FIG. 17, in accordance with embodiments of the invention.

[0053] FIG. 20 is a flow-chart of a command sequence that may be executed by control box 1720 to cause performance of the die placement steps illustrated in FIG. 18, in accordance with embodiments of the invention.

[0054] FIG. 21 is an illustration of command sequences executed by control box 1720 to cause a position change for a linear stage or a rotational stage, in accordance with embodiments of the invention.

[0055] FIG. 22 is an illustration of a multi-sector designed applied to a rotational stage stator layer, in accordance with embodiments of the invention. Four sectors are illustrated, with Sector 1 outlined. Each sector has its own group of electrodes connected to the controller box. A total of 16 control lines are shown, 4 each for the four sectors.

[0056] FIGS. 23A, 23B, and 23C are illustrations of multiple sectors used both to sense and to control vertical displacement and tilt, in accordance with embodiments of the invention.

[0057] FIG. 24 is an illustration of a different displacement on one of four individual actuators on a workpiece placement system, one actuator having decompressed fluidic layers while the other three actuators have compressed fluidic layers, in accordance with embodiments of the invention.

[0058] FIG. 25 is an illustration of an array of workpieces comprising repeated patterns of workpieces being positioned and attached using workpiece placement system 1702, in accordance with embodiments of the invention.

[0059] FIG. 26 is a side view of die placement system 1702 receiving dies 1704 (steps 1A and 2A); aligning the dies with imaging feedback provided by multi-imager-module 1806 (steps 1B and 2B); and bonding dies 1704 to the target destination substrate/structure 1710, (step 1C); or to the intermediate structure 2601 (step 2C), which then proceed to bond dies 1704 to the target substrate/wafer destination substrate/structure 1710 (step 2D), in accordance with embodiments of the invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0060] Unless defined otherwise, all technical and scientific terms used herein have the meaning commonly understood by a person skilled in the art to which this invention belongs. As used herein, the following terms have the meanings ascribed to them unless specified otherwise.

[0061] The terms a and an and the and similar reference used in the context of describing the invention (especially in the context of the claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0062] A set includes at least one member.

[0063] An electro-fluidic transport substrate includes: [0064] an array of electrodes; [0065] a dielectric layer, disposed above the array and having a hydrophobic surface; [0066] a fluidic layer disposed on the hydrophobic surface and including a first non-conductive liquid and a second conductive liquid, wherein the first and second liquids are immiscible; and [0067] a carrier layer having defined hydrophilic and hydrophobic regions in selected contact with the second conductive liquid and the first non-conductive liquid, respectively, configured in a manner so that appropriate powering of the electrodes effectuates motion of the carrier layer.

[0068] A hydrophobic surface of a dielectric layer is a member selected from the group consisting of a hydrophobic finish included in the dielectric layer and a distinct hydrophobic layer disposed on the dielectric layer.

[0069] As used herein, a die is a workpiece, and the two terms are used interchangeably herein. A die or a workpiece may also be referred to as a component herein.

[0070] A die placement system includes a substrate structure having a plurality of actuator stages in a regular grid.

[0071] In various embodiments of the present invention, there is provided a many-head parallel stage for an actuator that is configured to position many dies simultaneously, combining the simplicity and flexibility of die-bonders, with the parallelism of wafer-bonders, achieving both throughput gain and high precision.

[0072] FIG. 1A is a vertical section view of the head 101 of an actuator stage 101 in accordance with an embodiment of the present invention. In this embodiment, the actuator stage includes an x/y-linear stage 102 (thus configured to achieve translation) having electro-fluidic transport substrates including interleaved stator layers 131 and translation layers 133, which are mounted on a base assembly 103. Attached to the x/y-linear stage 102 of the actuator stage is a rotational stage 104 having electro-fluidic transport substrates including interleaved stator layers 132 and rotor layers 134. The actuator stage further includes; a die-handling head 105 attached to the rotational stage 104. In turn, vacuum tube 107, which is coupled to the die-handling head 105 and mounted in the base assembly 103, feeds a vacuum to the handling head 105 in a manner to removably hold onto the head 105 a semiconductor die 106. A control box 108 is connected to the x/y-linear stage stator layers 131 and the rotational stage stator layers 132 to provide power and movement control. In one embodiment, to obtain position information of the die 106 relative to the substrate 109 onto which the die 106 is to be placed, the control box 108 is configured to obtain and utilize capacitance data from the stages, as described below in connection with FIG. 2.

[0073] In the context of FIG. 1A, we refer to the Z axis as corresponding to the central axis Z-Z of the vacuum tube 107, and the X-Y axes as perpendicular to the Z axis.

[0074] In another embodiment, a gripper is used in place of the vacuum tube 0107 to removably adhere the die 106 to the head 105.

[0075] In a related embodiment, the control box 108 obtains position information from a camera configured to image appropriately situated fiducials to obtain relative positions of the die 106 and the substrate 109. In one embodiment, the fiducials are on the die 106 and the actuator stage 101, while in another embodiment, the fiducials are placed on the actuator stage 101 and the substrate 109 onto which the die 106 is to be placed.

[0076] The base assembly 103 in FIG. 1A contains an opening 143 to which is coupled a vacuum supply. The vacuum tube 107 receives the vacuum from the opening 143. The vacuum tube 107 includes in its base a flange 142 that is mounted with ball bearings 141 in a corresponding slot 140. The handling head 105 is configured to slide and rotate within the slot 140 riding on ball bearings 141. To assure tight coupling between the opening 143 and the vacuum tube 107, the slot 140 is appropriately sealed, by means that may include vacuum grease, a set of O-rings, or both vacuum grease and a set of O-rings. As discussed above, the x/y linear stage 102 is composed of an electro-fluidic transport substrate, including a plurality of x/y stator layers 131, alternating with a plurality of x/y translation layers 133. The stator layers 131 are attached together along one or more outer edges as described in connection with FIG. 9, and, similarly, the translation layers 133 are attached together along one or more outer edges and one or more inner edges as described in connection with FIG. 9.

[0077] A mounting plate 111 has a core 112 that is fitted into the central opening of the translation layers 133 and around the vacuum tube 107. The rotational stage 104 is attached to the mounting plate 111. As described above, the rotational stage 104 is composed of another electro-fluidic transport substrate, including a plurality of rotational stator layers 132, alternating with a plurality of rotor layers 134. The rotational stator layers 132 are attached together along the other edges as described in connection with FIG. 10. The rotor layers 134 are attached together along the inner edges as described in connection with FIG. 10. The die-handling head 105 is attached to the rotor layers 134.

[0078] As described above, in one embodiment, a semiconductor die 106 is attached to the die-handling head 105 by the vacuum introduced through vacuum tube 107.

[0079] In another embodiment, a semiconductor die 106 is attached to the die-handling head 105 via polymer coating on the surface of 105.

[0080] In another embodiment, a plurality of slots 140 and corresponding flanges 142 are used for added stability.

[0081] The control box 108 sends a first category of electrical signals to the x/y-translation layers 133 to move linearly in x and y with respect to the x/y-stator layers 131, thereby causing the die-handling head 105 and the die 106 to move correspondingly in x and y. The control box 108 sends a second category of electrical signals to the rotor layers 134 to cause them to be angularly displaced about the Z axis, thereby causing the die-handling head 105 and the die 106 to be correspondingly angularly displaced.

[0082] In FIG. 1B, a perspective rendering of some of the actuator stage components of FIG. 1A is shown, including the die handling head 105, the x/y linear stage 102, the rotational stage 104, the flange 142, and the vacuum tube 107.

[0083] FIG. 1C shows an exploded view of the various layers discussed in relation to FIG. 1A. The x/y linear stator layers 131 and the x/y translation layers 133 form the x/y linear stage 102 of FIG. 1A. The rotational stator layers 132 and the rotor layers 134 form the rotational stage 104 of FIG. 1A. A few layers are illustrated for clarity. In actual embodiments, the number of actuating layers will be determined by the application requirement.

[0084] Alternative configurations can be built to provide equivalent movement of the semiconductor die in-plane, for example, one rotational stage, with one linear stage, with a second rotational stage; or one single-axis linear stage, with a second single-axis linear stage oriented in a different direction, with a rotational stage; etc.

[0085] FIG. 2A is a vertical section of one embodiment of a functional cell of an electro-fluidic transport substrate 201 in accordance with an embodiment of the present invention. FIG. 2B is an enlarged view of the right end corner of the droplet 204 of FIG. 2A.

[0086] The transport substrate functional cell is composed of a rotor/translation layer 202, where a conductive liquid droplet 204 is anchored to a well 208 either physically or chemically. The conductive liquid droplet 204 is surrounded by another immiscible non-conductive liquid 205, and is free to glide across the hydrophobic surface layer or finish 206 of the stator layer 203. The conductive liquid droplet 204, the surrounding liquid 205, and the hydrophobic layer 206 are chosen such that electro-wetting effect is possible. As a voltage is applied across the interface between the conductive liquid droplet 204 and the hydrophobic layer 206, it changes the contact angle between the conductive liquid droplet 204, the non-conductive liquid 205, and the hydrophobic layer 206.

[0087] In another embodiment, the liquid droplet 204 is non-conductive, while the surrounding liquid 205 is conductive, in which case the voltage is applied across the surrounding liquid 205 and the hydrophobic layer 206.

[0088] In another embodiment, the liquid droplet 204 is surrounded by air or an inert gas 205.

[0089] The stator layer 203 has embedded electrodes 207. The liquid droplet 204 is connected to an electrode 211, either via direct contact or capacitive coupling somewhere along the droplet outside the cross-sectional view. The control box 108 regulates the amount of charge in each of the embedded electrode 207 and the liquid droplet 204 via the electrode 211. Each electrode forms a capacitor with the liquid droplet across the dielectric 210, as shown in FIG. 2B, a close-up view of the right-hand corner of the droplet 204. The relative position of the liquid droplet and the electrode determines the capacitance. It is the highest when the electrode is entirely under the droplet, and reduces in value as the droplet only partially covers the electrode. The capacitance (C), together with the charges on the electrode (Q), determine the voltage across that electrode and the water droplet (V), according to V=Q/C.

[0090] The equivalent circuit of the electrodes and the capacitors they form with the droplet 204 is shown in FIG. 2C. In one embodiment, the liquid droplet 204 is grounded, and three of the electrodes are provided charges Q1, Q2, and Q3, as in FIG. 2A. The position of the droplets with respect to the electrodes results in the electrodes forming capacitances C1, C2, and C3 with respect to the ground, leading to voltages V1, V2, and V3 at the respective electrodes. In the example illustrated in FIG. 2A, V1 is larger than V3, resulting in a smaller contact angle on the right-hand side as compared to the left-hand side of the droplet 204, leading to a net force moving the droplet 204 and the rotor layer 202 to the right, as indicated by the arrow pointing to the right.

[0091] FIG. 3A illustrates the mechanism of position control for a functional cell of the electro-fluidic transport substrate 201 of FIG. 2A. The liquid droplet 204 touches the stator dielectric surface 206 on top of an array of electrodes. The left liquid-dielectric interface is on top of electrode 303. The right liquid-dielectric interface is on top of electrode 301. The contact angle of the droplet of liquid 204 with the stator dielectric surface 206 is determined by the voltages across these two electrodes to the liquid droplet, respectively, as given by the equations (1), (2), (3) in FIG. 3A. .sub.ws is the surface tension between liquid 204 and dielectric surface 206. It is related to .sub.ws0, the surface tension without applied voltage, by equation (1). C is the capacitance per unit area at the interface. V is the applied voltage. .sub.wo is the surface tension between liquid 204 and liquid 205. .sub.os is the surface tension between liquid 205 and dielectric 206. Higher voltage leads to smaller contact angle as in equation (3). If the contact angles on the left side and the right side are different, there is a net force from the surface tensions, pushing the droplet toward the side with the smaller contact angle, which is also the side with the higher voltage.

[0092] In the example illustrated in FIG. 3A, the droplet 204 is in equilibrium with the contact angles being the same on the left and the right interfaces. As in FIG. 2A, let us designate the capacitance attributable to the presence of liquid 204 above electrode 303 as C3, and the voltage across electrode 303 to the droplet 204 as V3, with Q3 designating the charge on the C3 capacitor. Similarly, let us designate the capacitance attributable to the presence of liquid 204 above electrode 301 as C1, and the voltage across electrode 301 to the droplet 204 as V1, with Q1 designating the charge on the C1 capacitor. Therefore, the voltage across electrode 303 to the droplet 204, V3=Q3/C3, is equal to the voltage across electrode 301 to the droplet 204, V1=Q1/C1. The capacitance is roughly proportional to the overlap between the droplet and the electrode. If the droplet 204 is moved to the right by a distance x while the charges are maintained on the electrodes 301 and 303, the capacitance C3 is reduced, because less liquid 204 overhangs electrode 303, leading to an increase in V3. At the same time, the capacitance C1 increases, leading to a reduction in V1. From the previous discussion, it is clear that there is now a restoring force F pushing the droplet back to the left, until the equilibrium position is attained once more with V1 equal to V3.

[0093] The droplet 204 is in equilibrium when V1=V3, which can also be written as Q1/C1=Q3/C3. Since the capacitances C1 and C3 are correlated by the position of the droplet 204 on the dielectric surface 206, the equilibrium position is determined by the charge ratio Q1/Q3. The accuracy of the position is determined by the accuracy of this charge ratio.

[0094] In related embodiment, a mixed voltage/charge control can be applied, in which the controller box 108 regulates voltage at one side of the droplet 204, for example V1, and regulates charge at the other side of the droplet, for example Q3. In this case, as discussed in the previous paragraph, the rightward movement of the droplet will reduce the capacitance C3, and thus increase V3=Q3/C3, so as to provide a restoring force as V3 deviates from V1.

[0095] FIGS. 3B, 3C, 3D, 3E, and 3F illustrate an example of position control, in accordance with an embodiment of the present invention, using an external capacitance switching arrangement. In this embodiment, the charge regulation is accomplished by connecting an external capacitor in parallel with one of the phases. For example, in reference to FIG. 3B, let the initial configuration be such that electrode 301 is grounded, and electrodes 302 and 303 are connected to the voltage source with value of V0, so the droplet sits on top of electrodes 302 and 303 in FIG. 3B. The capacitor C3 has its maximum capacitance value of C0. Therefore, the charge on capacitor C3 is given by Q3=C3V3=C0V0. To cause the droplet 204 to move, electrode 303 is first disconnected from the voltage source, and then connected to an external capacitor with capacitance value of C4 and zero charge. The effect of this action is to connect capacitor C3 in parallel with capacitor C4. (These actions can be effectuated by suitable configuration of the control box 108, as illustrated in FIG. 3C.) Part of the charge on capacitor C3 will move to the external capacitor C4 to equilibrate voltages of these two capacitors, leading to a new V3 that is lower than the original value of V0. Next, V1 is disconnected from ground and connected to voltage source V0. (Also effectuated by suitable configuration of the control box 108, as illustrated in FIG. 3D.) This action will cause the force to move the droplet. since V3 is lower than V1. Capacitance C3 drops as the droplet moves until V3 is equal to V1. The end condition is therefore given by C0V0/(C4+C3)=V0, or C3=C0C4, as illustrated in FIG. 3E. By choosing the capacitance value C4 of the external capacitor, the final value of C3 can be determined, and so is the position of the droplet 204. The trajectories of V1 and V3 in response to the control changes described in this example are illustrated in FIG. 3F.

[0096] FIG. 3G illustrates an example of position control using a voltage source to set phase charges directly, in accordance with an embodiment of the present invention. In this example, voltages of various phases (V1, V2, V3) are controlled by the control box 108. The phase associated with voltage V3 is shown in more detail where phase electrode 303 may be disconnected from voltage source V3, via an electronic switch or isolator 350. Electrode 303 is connected with measurement capacitor C4. The charge on the electrode 303 can be tuned by varying V3 when 350 is connected. Once 350 is disconnected, V1 can be varied to pull droplet 204 to different positions, subject to C3=(Q3(V1V3)C4)/V1. C3 being capacitively connected to V4 via C4 also allows it to be measured and monitored.

[0097] There may be static friction associated with the liquid-stator interface. This static friction can result in an offset of the position as compared to what the charge ratio would suggest absent static friction. This offset can be compensated. It can also be measured via a position measurement system.

[0098] FIG. 4 is a vertical section of a system 401, in accordance with an embodiment of the present invention, using a combination of a plurality of functional cells, of the type shown in FIGS. 2A, 2B, 2C and 3, in a manner to provide a single layer of a larger system, where the forces from each of the droplets are combined to make a stronger actuator. The droplets 204 are anchored to the rotor/translation layer 202, and are separated by N microns between them. In one embodiment, N is 40. The droplets 204 slide on top of the stator layer 203 with the embedded electrodes. In one embodiment, the electrodes are organized into four phases, P1, P2, P3, P4. The electrodes of each phase are charged and discharged together. The droplets 204 are surrounded by the other liquid 205.

[0099] FIG. 5 is a vertical section of a stack of layers, in accordance with an embodiment of the present invention, wherein each layer is of the type shown in FIG. 4, and stacked in the same orientation as each other layer. In this configuration, each layer 506 has a top surface 503 where the droplets 504 contact and slide against, on top of embedded electrodes. The layer 506 has a bottom surface 502 with wells where the droplet 204 are anchored to. In this embodiment, each layer 506 with its anchored droplets 204 slides against the next layer either in the same direction which increases the speed of movement, or in alternating directions which increase the total force output of the electro-fluidic transport substrate 501. The droplets 204 are surrounded by the other liquid 205.

[0100] FIG. 6 is a vertical section of a stack of layers, in accordance with an embodiment of the present invention, wherein each layer is of the type shown in FIG. 4, and stacked with adjacent pairs which are oriented back-to-back. In this configuration, the electro-fluidic transport substrate 601 is composed of two types of layersthe rotor/translation layer 602 where both top and bottom surfaces have wells where droplets 204 are anchored in, and the stator layer 603 where both top and bottom surfaces have embedded electrodes and are in contact with droplets 204. The droplets 204 are surrounded by the other liquid 205.

[0101] FIG. 7 is a vertical section of a stack of a plurality of layers, in accordance with another embodiment of the present invention, again wherein each layer is of the type shown in FIG. 4, and wherein the spatial frequency of electrodes is different in each layer and configured to provide vernier adjustment of position. Two electro-fluidic transport substrate layers (as shown in FIG. 4) are stacked on top of each other. The top electro-fluidic transport substrate 702 has a pitch (distance from droplet to droplet) of N2, whereas the bottom electro-fluidic transport substrate 701 has a pitch of N1. The electro-fluidic transport substrate 701 has a stator layer 703, and a motion layer 704. The electro-fluidic transport substrate 702 has a stator layer 705, and a motion layer 706. The stator layer 702 is attached to the motion layer 704. When N1 is not equal to N2, a finer resolution given by N3 equal to the greatest common divider of N1 and N2 can be achieved for the system. For example, if N1=40 um, and N2=39 um, then 1 um step can be achieved by moving the electro-fluidic substrate 701 one step forward and the electro-fluidic transport substrate 702 one step backward.

[0102] Another way to achieve an effect similar to that accorded by the configuration of FIG. 7 is to have the droplets pitch be slightly different from an integer multiple of the electrode pitch.

[0103] FIG. 5, FIG. 6 and FIG. 7 show alternative embodiments of how a plurality of layers of the electro-fluidic transport substrate can be stacked in the Z direction.

[0104] FIGS. 8A and 8B are diagrams of linear and circular patterns, respectively, of the array of electrodes in an electro-fluidic transport substrate, in accordance with embodiments of the invention. We have mentioned above that an actuator in accordance with an embodiment of the present invention utilizes a set of electro-fluidic transport substrates, disposed on the base layer, wherein each of the substrates has an array of electrodes. In FIG. 8A and FIG. 8B, are illustrated alternative embodiments of this array, and therefore how the unit cells of the electro-fluidic transport substrate can be arranged in the X-Y plane. In FIG. 8A, the translation layer 801 is displayed with the droplets 802 arranged in a linear fashion. These are matched with stator with embedded electrodes also arranged in the linear fashion to form linear actuators to achieve translation of the head of the transport substrate. In FIG. 8B, the rotor layer 803 is displayed with the droplets 804 arranged in a circular pattern. These are matched with stator layer with embedded electrodes also arranged in a circular pattern, to achieve rotation of the head of the transport substrate.

[0105] FIGS. 9A and 9B are top views of an x/y stator layer 131 and an x/y translation layer 133, respectively, of the type shown in FIG. 1A-C, in accordance with embodiments of the invention. Referring to FIG. 9A, x/y-stator layer 131 includes four embedded electrode arrays 903 arranged around central opening 904. Along three edges of x/y stator layer 131 are thick regions 902, which are used to (i) bond a plurality of x/y-stator layers 131 together, e.g., as shown in FIG. 9D, (ii) bond an x/y-stage to the base assembly 103 of FIG. 1A, and (iii) connect electrode arrays 903 to external power and control circuits.

[0106] Referring to FIG. 9B, x/y-translation layer 133 includes four droplet arrays 913, each array positioned to align with a corresponding set of electrode arrays 903 to form an electro-fluidic transport substrate. The center of the x/y-translation layer 133 includes center thick region 915 defining opening 914. Along one edge of x/y translation layer 133 is second thick region 912. The center thicker region 915 fits within opening 904 of x/y-stator layer 131. Center thick region 915 and second thick region 912 are used to bond a plurality of x/y-translation layers 133 together, and to bond x/y-stage translation layers to a payload.

[0107] FIG. 9C is a top view of a set of x/y translation layers 133 interleaved with a set of x/y stator layers 131, in accordance with embodiments of the invention. FIG. 9D is a vertical section of the set of x/y translation layers 133 interlaced with the set of x/y stator layers 131 shown in FIG. 9C, in accordance with embodiments of the invention. Thicker regions 902, 912 and 915 serve to connect individual layers and connect to the base assembly 103 substrate and a payload, respectively, while allowing relative motion between the x/y stator layers 131 and x/y translation layers 133. In describing motion achieved by the translation layer 133 in relation to the stator layer 131, we refer to left/right motion in FIG. 9C as along the x-axis of the x/y plane and up/down motion in FIG. 9C as along the y-axis of the x/y plane. Two electrode arrays 903 of x/y stator layer 131 (shown at the top and bottom of FIG. 9A) move translation-layer 133 left and right with respect to stator layer 131. Two electrode arrays 903 of x/y stator layer 131 (shown at the left and right of FIG. 9A) move translation-layer 133 up and down. In some embodiments, an axle connects translation layers 133 via central opening 914.

[0108] FIGS. 10A and 10B are top views of an x/y stator layer and an x/y translation layer, respectively, assembled in an alternate configuration of the push-pull system of FIGS. 9A and 9B, in accordance with another embodiment of the invention. In FIGS. 10A and 10B, the interactions between electrode arrays and droplet arrays are configured to achieve motion along the x-axis and y-axis in a manner wherein the axes are swapped in relation to the motion achieved in FIGS. 9A and 9B. In other embodiments, any combination of electrode arrays can be configured to move along either the x-axis or the y-axis, and additional electrodes arrays and droplet arrays can be added to a corresponding layer.

[0109] The figures in this application are illustrative and are not intended to show dimensions to scale.

[0110] FIGS. 11A, 11B, and 11C are views corresponding to FIGS. 9A, 9B, and 9C, respectively, but in this case showing an embodiment of the rotational stage layers. The stator layer 132 is illustrated in FIG. 11A in a top view, showing a circular array of embedded electrodes 1103 arranged around a central opening 1104. Along the outer edge is a thicker region 1102 used to bond a plurality of stator layers 132 together, and for bonding the rotational stage to the base layer, and for connecting electrodes 1103 to external power and control circuits. The rotor layer 134 is illustrated in FIG. 11B in a top view, having a droplet array 1113 arranged to match the electrode array 1103 to form an electro-fluidic transport substrate. The center of the rotor layer 134 has a thicker region 1115 with an opening 1114. The thicker region 1115 fits within the opening 1104 in the stator layer 132. The thicker region 1115 is used to bond a plurality of rotor layers together, and for bonding the rotational stage to payloads. The assembled configuration with the rotor layers 134 interlaced with the stator layers 132 is illustrated in FIG. 11C in a vertical section. Thicker regions 1102 and 1115 serve to connect the individual layers and connect to substrate and payload, while allowing relative motion between the stator layers 132 and the rotor layers 134.

[0111] FIG. 12A is an exploded perspective view of an embodiment including a plurality of actuator stages 101 of the type shown in FIG. 1B, here arranged in a grid, to a plurality of dies to be placed simultaneously, forming a die-placement system. Each actuator stage 101 is attached to substrate 1201 via its x/y linear stage 102. Top cover 1203 attaches to the top of the substrate 1201 with matching vacuum connection 1204 for each actuator stage 101.

[0112] FIG. 12B is a cut-away view of the embodiment of FIG. 12A, revealing layer arrangements of two actuator stages, in accordance with embodiments of the invention.

[0113] Different configurations of the die-handling head are possible. In another embodiment, the die placement system shown in FIGS. 12C, 12D, and 12E, the actuator stage 101 has one head extension on the top of die-handling head 1215 for vacuum connection. The actuator stage 101 has a x/y linear stage 102 and a rotational stage 104, and a die attachment head 105, in the same manner as shown in FIG. 1B. There is a position plate 1216 which sits in the slot 1231 of the substrate plate after assembly. There is a second position plate 1217 which sits in the slot 1232 of the substrate plate after assembly. In this embodiment, the actuator stage 101 is supported by a plurality of supporting plates.

[0114] The actuator layers are enclosed by a plurality of supporting plates. In one embodiment, the actuator stage 101 is attached to plate 1223. The plate 1221 is attached to the bottom of 1223, and the position plate 1217 is attached to the bottom of the die handling head 1215. The plate 1222 is attached to the bottom of 1221, and the die attachment head 105 is attached to the bottom of the position plate 1217. The position plate 1216 is attached to the top of the die handling head 1215. The plate 1224 is attached to the top of the plate 1223, completing the assembly of the die placement system.

[0115] FIG. 13 is a schematic showing an actuator stage 101 with a control box 108 configured to measure capacitances of the actuator stage to determine the position of a translation layer relative to a corresponding stator layer, in accordance with embodiments of the invention. As a droplet slides over an embedded electrode of an array, the capacitance of the capacitor formed between the electrode and the droplet changes depending on the amount of overlap. By measuring this capacitance, the amount of overlap, and therefore the position of the moving translation layer relative to its corresponding stator layer can be determined. In one embodiment, a capacitance measurement is performed on position-driving electrodes using an AC signal with a frequency higher than that of the control signals used to regulate the amount of charge, or voltage on the electrodes. In another embodiment, a capacitance measurement is performed on dedicated position-measurement electrodes and associated droplets. In one embodiment, control box 108 measures three sets of capacitances, with electrode phases 1303 associated with movement along one of the x-axis and the y-axis of a linear stage, electrode phases 1304 associated with movement along the other one of the x-axis and y-axis of the linear stage, and electrode phases 1305 associated with angular rotation of a rotational stage.

[0116] FIG. 14 shows a component die with alignment fiducials on a facet facing the substrate, wherein these fiducials are used to position the die with respect to the actuator stage in accordance with an embodiment of the present invention. Component die 106 has alignment fiducials 1402 on the facet 1403 to be bonded with a substrate. The actuator stage 101 has alignment fiducials 1405. Die position camera 1406 takes pictures of the actuator stage 101 with component die 106 so that fiducials 1402 and 1405 are in the same pictures, and are used to calculate the position of the component die 106 with respect to the actuator stage 101. In another embodiment, a plurality of die position cameras are used to take pictures of various groups of fiducials. The calculated position of the component die 106 is used to move the actuator stage to position the die to the desired position.

[0117] As illustrated in FIG. 15, in one embodiment, alignment fiducials 1501 on the die placement system 1502 and alignment fiducials 1503 on the substrate 1504 are used to align the die placement system to the substrate. In one embodiment, the die placement system 1502 is transparent to the substrate alignment camera 1505 at the positions of the alignment fiducials 1501 and 1503. The substrate alignment camera takes pictures so that fiducials 1501 and 1503 are in the same pictures, and are used to calculate the position of the die placement system 1502 with respect to the substrate 1504. In another embodiment, the die placement system 1502 is transparent in near IR wavelengths. The calculated position shift is used to shift the die placement system with respect to the substrate, as described below in connection with FIG. 17.

[0118] In another embodiment, the position shift is added to the measured position shift between component dies and actuator stage as described in connection with FIG. 14 and corrected by the actuator stage.

[0119] FIG. 16 shows an embodiment in which a plurality of linear stages are stacked on top of each other in a long-range linear motion stage 1601 to achieve a higher speed movement over a distance. The stage 1601 has a stator layer 1602, upon which is attached a stage-1 layer 1603 with a top half configured as a translation layer forming an electro-fluidic transport substrate with the stator layer 1602. The bottom half of the layer 1603 is configured as a stator layer, upon which is attached a stage-2 layer 1604 with the same top and bottom configuration as 1603, with an overall shorter length. Similarly, a stage-3 layer 1605 is attached to layer 1604, and a stage-4 layer 1606 is attached to layer 1605. The bottom half of layer 1606 is configured with a die-handling head, which picks up a payload semiconductor die 1607. In one embodiment, the substrate 1602 is more than 300 mm long. In one embodiment, all stages move to the right with respect to the previous one at their nominal velocity, moving the die 1607 through the configuration shown in 1608 to the final configuration shown in 1609. The semiconductor die 1607 is moved from one end of 1601 to the other end with a velocity equal to the sum of the nominal velocities of all stages.

[0120] FIG. 17 is a side view of a die placement system 1702 receiving component dies 1704 from component feeder 1703 and moving via global gantry system 1701 to allow placement of component dies 1704 on substrate/wafer 1710 in accordance with one embodiment of the invention. Global gantry system 1701 comprises an x/y gantry control 1731 and a z gantry control 1732. Global gantry system 1701 can use a multi stage actuator system, such as described in FIG. 16, and can also use conventional electromagnetic and piezo-electric drivers. In one embodiment, control box 1720 is configured to control global gantry system 1701. In FIG. 17, die placement system 1702 is shown attached to z gantry control 1732. In other embodiments, die placement system 1702 is attached to x/y gantry control 1731 or to an intermediary between global gantry system 1701 and die placements system 1702.

[0121] Die placement system 1702 receives component die 1704 onto empty actuator stage 101 from component feeder 1703. In one embodiment, after placing a component die 1704 onto actuator stage 101, component feeder 1703 picks up the next component die from component die supply tray 1707. In one embodiment, after each placement, die placement system 1702 is shifted to present the next empty actuator stage 101 to component feeder 1703. In other embodiments, component feeder 1703 is shifted to the next position on die placement system 1702. As the die placement system 1702 is shifted, the die position camera 1706 (equivalent to, and used herein interchangeably with, die position camera 1406) provides picture or video feed by which can be determined the die's position and orientation with respect the die placement system 1702, such as described in FIG. 14. Optionally, the die position camera 1706 is implemented with a system utilizing a set of cameras to monitor positioning of a set of dies 1704, wherein the set of dies may include many members. The control box 1720 uses the picture or video information to help position the component dies 1704 properly with respect to the die placement system. Wafer/substrate 1710 is disposed on top of chuck/stage 1712. Substrate alignment camera 1711 (equivalent to, and used herein interchangeably with, substrate alignment camera 1505) aids in the alignment of the die placement system 1702 with the substrate wafer 1710, as described in connection with FIG. 15. In one embodiment, a plurality of fiducials on die placement system 1702 are checked against the matching fiducials on the wafer/substrate 1710 to produce a position shift map. There may be a plurality of sets of fiducials on the substrate wafer, to help positioning component dies in different regions of the wafer/substrate. Additional displacements detected by the substrate alignment camera 1711 are corrected by the global gantry system 1701. When component dies 1704 are in the correct place over wafer/substrate 1710, the z gantry control 1732 lowers the dies onto the wafer/substrate.

[0122] In a related embodiment, the component die supply tray 1707 is configured to be loaded with dies in a manner to correspond with physical positions occupied by the dies after they been removably attached to the head of the die placement system 1702. Die supply tray 1707 may have features designed to retain die in a manner that corresponds to the physical positions they are expected to occupy when they are removably attached to actuators of die placement system 1702. Such features may include small depressions or wells, or small ridges or pins to help retain the dies into position. When the component die supply tray 1707 is configured in this manner, and the component die supply tray 1707 has been populated with dies in a plurality of the positions, then, when the head of the die placement system 1702 has been maneuvered above the die supply tray 1707, the head can be used to pick up all these dies simultaneously without recourse to the separate component feeder 1703. In this manner, the dies can be loaded efficiently into the heads of the die placement system, which can then be used to efficiently place the loaded dies onto the corresponding wafer/substrate.

[0123] FIG. 18 is a side view of a die placement system 1702 illustrated here (i) receiving component dies 1704 from the multi-chip-transfer-module 1803; (ii) aligning the dies 1704 with imaging feedback provided by the multi-imager-module 1806; and (iii) bonding the dies 1704 to the target substrate/wafer 1710 with the target-bonding-module 1812, all in accordance with an embodiment of the invention. Global gantry system 1701 is used to position the multi-chip-transfer-module 1803 to pick up a plurality of chips from the component die supply tray (transport carrier) 1707, which is configured to be loaded with dies in a manner to correspond with physical positions occupied by the dies after they have been removably attached to the head of the die placement system 1702. The multi-chip-transfer-module 1803 is then positioned to place the dies 1704 onto the die placement system 1702, before returning to its initial position to be ready for picking up the next set of dies from the next transport carrier 1707. Next, the multi-imager-module 1806 is positioned over the die placement system 1702 to capture a set of images or a set of videos by which can be determined the position and orientation of each die with respect to the die placement system 1702. The control box 1720 uses the picture or video information to help position the component dies 1704 properly with respect to the die placement system 1702. Thereafter, the multi-imager-module 1806 returns from its position over the die placement system 1702. Next, the target-bonding-module 1812 with wafer/substrate 1710 disposed thereon, moves over to align with the die placement system 1702, with displacement feedback from the substrate alignment camera 1711 and corrected by the global gantry system 1701. When component dies 1704 are in the correctly aligned over wafer/substrate 1710, the z-gantry control 1832 lowers the wafer/substrate onto the dies.

[0124] The die-placement system 1702, as shown in FIG. 17 and FIG. 18, may also employ a plurality of conventional drive systems in place of actuator stage 101. Multi-chip-transfer-module 1803 may similarly employ a plurality of conventional drive systems plus vacuum chucks to hold the plurality of die, or it may use a plurality of actuator stages. Such a conventional drive system may use electromagnetic drives and/or piezo-electric drives to provide high precision position correction in the horizontal plane and/or angular position correction. The achievable density with conventional drive systems is expected to be lower than that of actuator stage 101, yet may nonetheless provide a throughput gain over single-die placement systems. An example of conventional drive systems providing high-precision position correction in single-die-placement system is disclosed in U.S. Publication No. 2021/0195816, which is hereby incorporated by reference for its disclosure of drive systems.

[0125] FIG. 19 is a flow-chart of a command sequence that may be executed by control box 1720 to cause performance of the die placement steps illustrated in FIG. 17. At operation 1901, control box 1720 initializes all actuator stage 101 positions before die placement and moves die placement system 1702 and component feeder 1707 into position. At operation 1902, control box 1720 sets index parameter #i to 1. At operation 1903, control box 1720 causes component feeder 1703 to place die 1704 onto first actuator stage 101. At operation 1904, control box 1720 causes imager/camera 1706 to measure displacement of die 1704 placed on stage #i in x, y, and angle as, x.sub.i, y.sub.i, .sub.i, respectively. At operation 1905, control box 1720 causes component feeder 1703 to place a next die 1704 onto stage #i+1. Operation 1905, the measurement of the displacement of the die 1704 to actuator stage 101 according to FIG. 14 may be executed in parallel with operation 1904, the placement of the next die 1704 onto the next actuator stage 101 by component feeder 1703. At operation 1907, it is checked if a last die has been placed. If no, parameter #i is incremented at operation 1906, and operations 1904 and 1905 are run again. If yes, displacement of the last die 1704 against a last actuator stage is measured at operation 1908. At operation 1909, control box 1720 causes die placement system 1702 to align with substrate holder 1712. At operation 1910, measurement of displacement of actuator stages 101 to target position on substrate 1710 may be performed by one or more of imager/camera 1711. At operation 1911, position correction required for each die 1704 may be simultaneously provided by corresponding actuator stage 101. At operation 1912, control box 1720 causes die placement system 1702 to move toward the substrate 1710, to bond all dies 1704 onto the substrate 1710.

[0126] FIG. 20 is a flow-chart of a command sequence that may be executed by control box 1720 to cause performance of the die placement steps illustrated in FIG. 18. At operation 2001, control box 1720 causes multi-chip-transfer-module 1803 to pick up a plurality of chips from component supply tray 1707; and also to initialize all actuator stage positions. At operation 2002, control box 1720 causes transfer-module 1803 to move and place dies 1704 onto actuator stages of die placement system 1702. At operation 2003, control box 1720 causes a plurality of imager-modules 1806 to measure displacement of dies 1704 from corresponding actuator stages 101 as (x.sub.i, y.sub.i, .sub.i) for each #i. At operation 2004, control box 1720 causes target-bonding-module 1812 to position substrate 1710 in position with respect to die-placement-system 1702. At operation 2005, control box 1720 causes a plurality of imagers/cameras 1711 to measure displacement of actuator stages to target positions on substrate 1710 for all stages #i as (u.sub.i, v.sub.i, .sub.i). At operation 2006, control box 1720 causes each actuator stage 101 #i to correct position in x, y, and angle given by (x.sub.i+u.sub.i, y.sub.i+v.sub.i, .sub.i+.sub.i). At operation 2007, control box 1720 causes bonding-module 1812 to place substrate 1710 onto die placement system 1702, to bond all dies 1704 onto substrate 1710. Operations that do not have mutual dependency, such as operation 2004 versus operation 2003, may be executed in any order.

[0127] FIG. 21 is an exemplary illustration of command sequences executed by control box 1720 to cause a position change for a linear stage or a rotational stage. Here, four phases are illustrated for each function, although any number of phases may be utilized as would be apparent to one of ordinary skill in the art. To provide position corrections as described in FIG. 19 and FIG. 20, the control box computes the required displacement step (i) for each actuator stage 101, (ii) for x and y displacements, and (iii) for rotation. For example, a movement of x.sub.i is computed at operation 2101. At operation 2102, the control box computes the required number of unit-steps, and the required partial-step, x.sub.i=NMove-Right+x Partial-Step-Right. The control box executes required movement steps by sending corresponding control voltages and charges according to various subroutines. Here, a number of Move-Right steps at operation 2103 and a Partial-Step-Right step at operation 2104 is illustrated. Optionally, the final position may be confirmed by capacitance measurements and/or visual inspection by imagers/cameras 1711, and additional corrections performed if necessary.

[0128] At operation 2105, the sequences required to Move Left are illustratedat operation 2106, V2 and V3 are set to a positive voltage V0, whereas V1 and V4 are set to 0, pulling droplet 204 onto phases 302 and 303. At operation 2107, V3 and V4 are set to V0, whereas V1 and V2 are set to 0, moving the droplet 204 onto phases 303 and 304. At operation 2108, the droplet is pulled onto phases 304 and 301. At operation 2109, the droplet is pulled onto phases 301 and 302. Cycling through operations 2106 through 2109 moves the droplet progressively to the left in integer steps.

[0129] At operation 2110, the sequences required to Move Right are illustrated. Cycling through operations 2111 through 2114 moves the droplet progressively to the right in integer steps.

[0130] At operation 2115, the sequences required to perform a partial step to the right is illustrate for when the droplet 204 starts on top of phases 302 and 303 as in operation 2116. At operation 2117, control box 1720 configures the charges in phases 301 and 303 to take on the ratio Q1/Q3=x/(1x), where x is the required partial step size between 0 and 1. This will move droplet 204 to increase C1 and reduce C3 until C1/C3=x/(1x). Optionally, at operation 2118, the final position is verified by measured C1/C3, and/or visually measured position, and error signal is used to correct Q1/Q3 until final desired position is achieved.

[0131] Relative ratios between capacitances, such as C1/C3, are used to determine the position for a functional cell of the electro-fluidic transport substrate 201. Precise controls of the ratios of corresponding charges, such as Q1/Q3, are used to control the said position. Comparing the measured capacitance ratios with the expected capacitance ratios from the applied charge ratios, the external force along the motion direction can be measured.

[0132] At the same time, independent of the ratios, the sizes of the capacitances, such as C1, C3, or sum of the capacitances, such as C1+C3, are used to determine the vertical position for the carrier layer with respect to the dielectric layer, averaged over the regions where the capacitances are measured. As the fluidic layer between the carrier layer and the dielectric layer is compressed, leading to a reduction of the z position for the carrier layer, the contact areas of the droplets with the dielectric layer grow, increasing the capacitances; while if the fluidic layer is decompressed, the droplet contact areas shrink, lowering the capacitances.

[0133] Independent of the ratios of charges, precise controls of the charges, such as Q1, Q3, or sum of the charges, such as Q1+Q3, are used to change the vertical position for the carrier layer with respect to the dielectric layer, over the regions where the controlled charges are applied. Increasing charges compresses the fluidic layer; whereas reducing charges decompress the fluidic layer.

[0134] Comparing the measured capacitances with the expected capacitances given the control charges, the external vertical force on the electro-fluidic transport substrate can be measured.

[0135] By defining and considering sectors within the array of electrodes in an electro-fluidic transport substrate, different amounts of vertical position control, and sensing are achieved for different sectors. FIG. 22 is an illustration of a rotational stage layer where four separate sectors are defined, as compared to the single sector design described in FIG. 11A. Sector one (2201) is outlined in a dashed line and is defined by the known and invariant positions of the electrodes associated with that slice-of-pie shaped portion of the stator. Consistent with labeling conventions of FIG. 4, in which representative adjacent electrodes used to adjust the position of the carrier layer are labeled P1, P2, P3 and P4, labels of FIG. 22 begin with an additional first digit to indicate localization of the electrode to a given sector. Thus, representative adjacent electrodes associated of sector 1 are labeled P11, P12, P13 and P14 in FIG. 22, while representative adjacent electrodes associated with sector 2 are labeled P21, P22, P23 and P24 in FIG. 22. Note, the sectors are virtual, since a sector is defined by choice of electrodes to group into that sector. Note also that the representative, adjacent and labeled electrodes do not comprise the entire sector. Only sector 1 is outlined in FIG. 22. FIGS. 23A, 23B, and 23C are illustrations of sensing and controlling vertical displacement and force by defining and considering sectors within the array of electrodes in an electro-fluidic transport substrate. The sectors can be defined by ranges of x and y or r and . Each sector contains multiple groups of electrodes as configured according to previous descriptions of single sector electro-fluidic transport. A group of electrodes are connected together and connected to the controller box. In FIGS. 23A, 23B, and 23C, a base layer having two sectors (2301 and 2302) is shown, each represented for ease of illustration by one droplet. The sectors are not to scale. Alternatively, multiple actuator stages may be used to handle one work-piece, in which case one sector can be on the first actuator stage, and another sector can be on a different actuator stage.

[0136] FIG. 23A shows two sectors with no additional external force on the handling head of the actuator. The capacitance of both sectors is the same and is equal to C.sub.0. The actuator has not moved relative to the workpiece transport substrate.

[0137] In FIG. 23B, an external force (2303) is applied to the top of the device causing uniform compressions of the electro-fluidic transport substrates within the actuator (or, alternatively, actuators) and causing the actuator(s) to move down relative to the workpiece transport system. This uniform compression of the electro-fluidic transport substrates causes the contact area between the droplets and dielectric layer to increase uniformly in the sectors. This leads to an increase in the total capacitance in both sectors C.sub.S1 and C.sub.S2, and C.sub.S1 is equal to C.sub.S2. Measurements of C.sub.S1 and C.sub.S2 are used to i) compute or look-up-via-calibration the net change in total vertical force which gives the external force, and also enables ii) computation or look-up-via-calibration of the vertical displacement from droplet volume conservation. At the same time, in-plane motion can be measured independently by comparing the capacitance of adjacent groups of electrodes within each sector as described earlier.

[0138] In FIG. 23C, external force (2304) is applied asymmetrically to the top of the device, causing nonuniform compression of the electro-fluidic transport substrates within the actuator (or, alternatively, actuators), causing a tilt of the actuator(s) relative to the workpiece transport system. This nonuniform compression of the electro-fluidic substrate causes the contact area between the droplets and dielectric layer to increase nonuniformly in the sectors. This leads to an increase in the total capacitance in both sectors C.sub.S1 and C.sub.S2, and unlike the case of uniform compression, C.sub.S1 is not equal to C.sub.S2. As before, measurements of C.sub.S1 and C.sub.S2 are used to i) compute or look-up-via-calibration the net change in total vertical force in each sector which gives the external forces, and ii) enables computation or look-up-via-calibration of the vertical displacement and tilt from droplet volume conservation. At the same time, in-plane motion can be measured independently by comparing the capacitance of adjacent groups of electrodes within each sector as described earlier.

[0139] In addition, applying different control voltages on the electrodes of each sector leads to different amounts of flattening of the droplets, allowing the height and tilt of the handling head of an actuator stage to be controlled. Any deviation from the anticipated change in capacitances C.sub.S1 and C.sub.S2 can be used to measure any change to the external force on the actuator stage.

[0140] With a rigid handling head, and a one-sector actuator stage, vertical position can be measured and controlled. With a two-sector actuator stage, vertical position and one tilt angle can be measured and controlled. With a 3-sector actuator stage, vertical position and both tilt angles can be measured and controlled. Higher number of sectors allow for measure and control of higher-order deformation, and also to provide measurement redundancy.

[0141] Destination structure 1710 in FIG. 17 may not be completely flat with respect to the workpiece placement system 1702. It is thus useful to be able to make small adjustments to the vertical displacement and tilt of each actuator in the workpiece placement system 1702, as shown in FIG. 24. Three of the individual actuators on this workpiece placement system have compressed fluidic layers as shown in 2401, while the remaining actuator has decompressed fluidic layers as shown in 2402, in accordance with embodiments of the invention.

[0142] FIG. 25 is an illustration of an array of workpieces comprising repeated patterns of workpieces 2501, 2502, 2503, 2504, 2505, and 2506 being positioned and attached using the workpiece placement system 1702. In this example, the workpiece placement system has a 22 array of precision stages (i.e., actuator stages). The desired outcome is shown in step (F), where workpieces of the same and different size and shapes are arranged with periodicity matching that of the precision stage array (array of actuators), while exhibiting inter-workpiece distance smaller than the periodicity of the said array. In each of the six steps from (A) to (F), the system places a set of 4 workpieces in each step, progressively completing the entire array, thus accomplishing placement of workpieces with closer workpiece separation than the spacing of the precision stages themselves. Placing different size workpieces in a mosaic pattern, which repeats according to the spacing of the actuators, results in an inter-workpiece spacing, between workpieces placed at different steps of the process, that is smaller than the spacing between the actuators of the array of actuators of the precision stage, as illustrated in FIG. 25.

[0143] In FIG. 26, two process flows using the workpiece placement system 1702 are described in detail. In step 1A die placement system 1702 receives the dies 1704 from supply tray 1707, with the device side with the alignment fiducials facing down. Two types of multi-imager modules can be used. Optical multi-imager module 1806 can measure fiducials on the surface of devices and substrate but cannot see through the die material. Substrate alignment camera 1711 can use infrared (IR) to measure fiducials through the bulk of the dies, provided that fiducials are not covered by other non-IR transparent material inside the workpieces. In step 1B the dies are aligned to desired locations with imaging feedback provided by the multi-imager module 1806 measuring the fiducials on the workpieces with respect to the fiducials on the placement system. The position can also be determined by the multi-imager module 1806 measuring the fiducials on the dies with respect to a global encoder of the multi-imager module. In step 1C the dies are bonded to the target destination structure 1710, with the alignment provided by the substrate alignment camera 1711. Substrate alignment camera 1711 can also be used to directly provide alignment between an individual die against their corresponding fiducials on the target destination structure and therefore bypass the need of running process step 1B. In the second process flow, dies are placed onto the placement system device-side facing up (step 2A). Alignment is accomplished in step 2B with the imaging feedback from the IR substrate alignment camera. The dies are then bonded to the intermediate structure 2601 in step 2C. In an alternative embodiment, alignment of the dies with the intermediate structure is achieved using a global encoder. Intermediate structure 2601 can be a temporary bonding wafer, which can be transported and inverted with no loss of fidelity of the die positions. Surface cleaning and preparation steps can be performed to the device-side of the dies while they are bonded to the intermediate structure. In step 2D, intermediate structure 2601 is flipped over and dies 1704 are bonded to the target destination structure 1710, with possible alignment feedback as described for step 1C.

[0144] Various embodiments of the present invention may be characterized by the potential claims listed in the paragraphs following this paragraph (and before the actual claims provided at the end of this application). These potential claims form a part of the written description of this application. Accordingly, subject matter of the following potential claims may be presented as actual claims in later proceedings involving this application or any application claiming priority based on this application. Inclusion of such potential claims should not be construed to mean that the actual claims do not cover the subject matter of the potential claims. Thus, a decision to not present these potential claims in later proceedings should not be construed as a donation of the subject matter to the public.

[0145] Without limitation, potential subject matter that may be claimed (prefaced with the letter P so as to avoid confusion with the actual claims presented below) includes: [0146] P1. An actuator stage, for precision positioning of a component, the actuator stage comprising: [0147] a base layer having a set of sectors defining spatial regions of the base layer and a surface defining a z-axis normal to the surface; [0148] a set of electro-fluidic transport substrates, disposed on the base layer, each of the substrates having: [0149] a plurality of sets of electrodes, each set located in a given sector of the base layer; [0150] a dielectric layer, disposed over each set of electrodes and having a hydrophobic surface; [0151] a fluidic layer disposed over the hydrophobic surface and including a first non-conductive fluid and a second conductive fluid, wherein the first and second fluids are immiscible; and [0152] a carrier layer having defined hydrophilic and hydrophobic regions in selected contact with the second conductive fluid and the first non-conductive fluid, respectively, configured in a manner so that appropriate powering of the electrodes effectuates motion of the carrier layer; [0153] wherein, corresponding capacitances are established between the carrier layer and each set of electrodes in a given sector; and [0154] a control port, coupled to the plurality of sets of electrodes, configured to (i) determine a differential between capacitances of at least two of the given sectors, a difference in capacitance indicating a tilt in the carrier layer relative to the base layer and (ii) apply voltages, to at least one set of electrodes, the voltage configured to move the carrier layer so as to (a) change the tilt of the carrier layer relative to the base layer, or (b) change a position of at least one component on the actuator stage with respect to the z-axis. [0155] P2. A method for precision placement of components onto a substrate, the method comprising: [0156] using a component placement system to pick up a first set of components; [0157] configuring the first set into a first desired spatial configuration by adjusting a position of each component of the first set of components; [0158] causing the component placement system to convey the first set of components to a first position over the substrate and to deposit the first set of components, in the first desired spatial configuration, on the substrate at the first position; [0159] using the component placement system to pick up a second set of components; [0160] configuring the second set into a second desired spatial configuration by adjusting a position of each component of the second set of components; and [0161] causing the component placement system to convey the second set of components to a second position over the substrate and to deposit the second set of components, in the second desired spatial configuration, on the substrate at the second position; [0162] wherein a given component of the deposited first set and a given component of the deposited second set are separated by a distance smaller than that of any given component of the first set of components in the first desired spatial configuration or the second set of components in the second desired spatial configuration. [0163] P3. A method for precision placement of a component onto a substrate, the method comprising: [0164] removably attaching the component to the component placement system; [0165] adjusting the position of the component on the component placement system into a desired first position by aligning a first set of fiducials on the component and a second set of fiducials on the component placement system using a first imager configured to image the first and second set of fiducials; and [0166] causing the component placement system to place the component on the substrate at a desired second position by aligning, using a second imager configured to image: [0167] (a) a set of fiducials selected from the group consisting of (i) the first set of fiducials, (ii) the second set of fiducials, and (iii) combinations thereof; and [0168] (b) a third set of fiducials on the substrate. [0169] P4. The method of potential claim P3, wherein at least one of the imagers is an IR imager. [0170] P5. The method of any one of potential claims P3-P4, wherein at least one of the imagers is a visible spectrum imager. [0171] P6. The method of any one of potential claims P3-P5, wherein at least one of the imagers is a multi-imager module. [0172] P7. The method of any one of potential claims P3-P6, wherein the first imager and the second imager are the same imager. [0173] P8. A method for precision placement of a component onto a substrate, the method comprising: [0174] removably attaching the component to the component placement system; [0175] adjusting the position of the component on the component placement system into a desired first position by aligning a first set of fiducials on the component and a second set of fiducials on the component placement system using a first imager configured to image the first and second set of fiducials; [0176] causing the component placement system to place the component onto an intermediate structure; [0177] inverting the intermediate structure; [0178] aligning the component to a desired position on a destination substrate using: [0179] (i) a second imager configured to image the first set of fiducials and a third set of fiducials on the destination substrate; or [0180] (ii) a global encoder; and [0181] causing the intermediate structure to place the component onto the destination substrate at the desired position. [0182] P9. The method of potential claim P8, wherein the intermediate structure is a temporary bonding wafer. [0183] P10. The method of any one of potential claims P8-P9, wherein at least one of the imagers is an IR imager. [0184] P11. The method of any one of potential claims P8-P10, wherein at least one of the imagers is a visible spectrum imager. [0185] P12. The method of any one of potential claims P8-P11, wherein at least one of the imagers is a multi-imager module. [0186] P13. The method of any one of potential claims P8-P12, wherein the first imager and the second imager are the same imager.

[0187] The embodiments of the invention described above are intended to be merely exemplary; numerous variations and modifications will be apparent to those skilled in the art. All such variations and modifications are intended to be within the scope of the present invention as defined in any appended claims