DUAL APPLICATOR FLUID DISPENSING METHODS AND SYSTEMS

Abstract

Methods of dispensing fluid are disclosed. A first applicator is positioned above a first dispense site at a first dispense region of a first electronic substrate by moving the first applicator using a primary positioner. A second applicator is simultaneously positioned above a first dispense site at a second dispense region of the first electronic substrate by moving the second applicator together with the first applicator using the primary positioner and moving the second applicator relative to the first applicator using a secondary positioner. It is then determined that the first or the second dispense region is misaligned relative to the other of the first or the second dispense region. Fluid is dispensed from the first applicator while moving the first applicator using the primary positioner to form a first fluid pattern at the first dispense region and fluid is simultaneously dispensed from the second applicator while moving the second applicator using the primary positioner and the secondary positioner.

Claims

1. A method for dispensing fluids by a dual dispensing system, the method comprising: obtaining one or more images of a first substrate and a second substrate; providing, based on the one or more images, instructions to a gantry, the gantry comprising i) a primary positioner that carries a first applicator and includes a surface and ii) a secondary positioner that carries a second applicator and is coupled to the primary positioner at the surface; actuating, by the primary positioner, the first applicator, in accordance with a first movement provided by the instructions; dispensing, while the primary positioner actuates the first applicator, a first fluid from the first applicator at a first dispensing region of the first substrate; actuating, by the secondary positioner, the second applicator in accordance with a second movement provided by the instructions, wherein the second movement causes the second applicator to move relative to the first applicator; and dispensing, while the second positioner actuates the second applicator, a second fluid from the second applicator at a second dispensing region of the second substrate, wherein the second fluid is dispensed from the second applicator simultaneously with the first fluid from the first applicator.

2. The method of claim 1, wherein the secondary positioner comprises a base plate that couples to the surface.

3. The method of claim 1, further comprising adjusting, while dispensing the first fluid, a first height of a first dispensing tip of the first applicator based on a first layout of the first substrate.

4. The method of claim 3, further comprising adjusting, while dispensing the second fluid, a second height of a second dispensing tip of the second applicator based on a second layout of the second substrate, wherein the first layout is different from the second layout.

5. The method of claim 1, further comprising: determining, based on the obtained one or more images, a tilt of the first substrate; and providing the instructions to automatically actuate, by the primary positioner, a height of the first applicator based on the tilt.

6. The method of claim 5, further comprising: determining, based on the obtained one or more images, a misalignment of the first substrate; and providing the instructions to automatically actuate, by the primary positioner, a position of the first applicator based on the misalignment.

7. The method of claim 1, further comprising: determining a contour of the second substrate; and providing the instructions to automatically actuate, by the secondary positioner, a height of the second applicator based on the contour.

8. A method for dispensing fluids by a dual dispensing system, the method comprising: obtaining one or more images of a first substrate and a second substrate; identify, based on the one or more images, a first location of a first substrate and a second location of a second substrate; performing a height sensing operation to determine i) a first height of the first substrate relative to an XY plane and ii) a second height of the second substrate relative to the XY plane; providing, based on the first location and the second location, first instructions to a gantry, the gantry comprising i) a primary positioner that carries a first applicator and ii) a secondary positioner that carries a second applicator; and based on the first instructions: actuating, by the primary positioner, the first applicator over the first substrate and dispensing a first fluid from the first applicator, and actuating, by the secondary positioner, the second applicator over the second substrate and dispensing a second fluid from the second applicator, wherein in response to the first height being different from the second height, providing second instructions, configured to adjust, using the secondary positioner, one of a first dispensing tip of the first applicator and a second dispensing tip of the second applicator.

9. The method of claim 8, wherein the second instructions cause the secondary positioner to move relative to the primary positioner.

10. The method of claim 9, wherein the second instructions cause the secondary positioner to move simultaneously with the primary positioner.

11. The method of claim 8, wherein the first height indicates a tilt to the first substrate.

12. The method of claim 11, wherein the first instructions automatically actuate at least one of the primary positioner and the secondary positioner to adjust for the tilt.

13. The method of claim 11, wherein: performing the height sensing operation comprises determining i) a third height of the first substrate relative to the XY plane, the third height indicating a contour of the first substrate, and in response to the third height, providing third instructions, configured to adjust, using the secondary positioner, the first dispensing tip based on the tilt and the contour.

14. The method of claim 8, wherein performing the height sensing operation comprises determining, using a height sensor coupled to one of the primary positioner and the secondary positioner, the first height and the second height.

15. A method for dispensing fluids by a dual dispensing system, the method comprising: obtaining one or more images of a first substrate and a second substrate; identify, based on the one or more images, a first location of a first substrate and a second location of a second substrate; providing first instructions to a first plurality of drive mechanisms, wherein the first plurality of drive mechanisms is configured to actuate a primary positioner in a first direction, a second direction, and a third direction, wherein the first direction, the second direction, and the third direction are orthogonal to each other, and wherein the primary positioner carries a first applicator; providing second instructions to a second plurality of drive mechanisms, wherein the second plurality of drive mechanisms is configured to actuate a secondary positioner in the first direction, the second direction, and the third direction, wherein the secondary positioner carries a second applicator; in response to determining the first substrate comprises a tilt, actuating, by the first plurality of drive mechanisms, the primary positioner to adjust for the tilt while dispensing a first fluid, from the first applicator, onto the first substrate; and in response to determining the second substrate comprises a contour, actuating, by the second plurality of drive mechanisms, the secondary positioner to adjust for the contour while dispensing a second fluid, from the second applicator, onto the second substrate.

16. The method of claim 15, further comprising actuating, by the second plurality of drive mechanisms, the secondary positioner relative to the primary positioner thereby actuating the second applicator relative to the first applicator.

17. The method of claim 16, further comprising actuating, by the second plurality of drive mechanisms, the secondary positioner simultaneously with the primary positioner thereby actuating the second applicator simultaneously with the first applicator.

18. The method of claim 15, wherein: the tilt comprises an incline, and the first plurality of drive mechanisms adjusts a dispense height of the first applicator based on the tilt.

19. The method of claim 15, further comprising determining, using a camera, the tilt or the contour.

20. The method of claim 19, further comprising determining, using a height sensor, the tilt or the contour.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention.

[0018] FIG. 1 is a top elevational view showing a carrier tray containing a plurality of substrates each aligned in proper, centered orientations.

[0019] FIG. 2 is a top elevational view showing a carrier tray containing a plurality of substrates each rotated or translated from their centered orientations.

[0020] FIG. 3 is a top elevational view similar to FIG. 2, showing a substrate tilted relative to a horizontal XY plane.

[0021] FIG. 3A is a side cross-sectional view taken along line 3A-3A of FIG. 3, showing the substrate tilted relative to the horizontal XY plane.

[0022] FIG. 4 is an isometric schematic view of a dual applicator dispensing system according to an embodiment of the invention.

[0023] FIG. 5 is an isometric schematic view similar to FIG. 3, showing a secondary positioner disassembled from a primary positioner.

[0024] FIG. 6 is a top elevational view of the dispensing system of FIG. 4, further showing a parts carrier tray in which the substrates are each rotated or translated from their centered orientations.

[0025] FIG. 7 is a top elevational view of first and second substrates of FIG. 6, showing positions of first and second applicator dispense tips prior to dispensing first and second fluid patterns.

[0026] FIG. 8 is a top elevational view similar to FIG. 7, showing positions of the applicator dispense tips after dispensing first portions of the fluid patterns.

[0027] FIG. 9 is a top elevational view similar to FIG. 7, showing positions of the applicator dispense tips after dispensing second portions of the fluid patterns.

[0028] FIG. 10 is a top elevational view similar to FIG. 7, showing positions of the applicator dispense tips after dispensing third portions of the fluid patterns.

[0029] FIG. 11 is a top elevational view similar to FIG. 7, showing positions of the applicator dispense tips after dispensing fourth portions of the fluid patterns.

[0030] FIG. 12A is an isometric view showing a substrate that is tilted relative to an XY plane, and a corresponding dispense height path along which an applicator moves while dispensing onto the tilted substrate.

[0031] FIG. 12B is an isometric view showing a substrate that is contoured relative to the XY plane, and a corresponding dispense height path along which an applicator moves while dispensing onto the contoured substrate.

[0032] FIG. 13A is side elevational view showing first and second dispense regions provided on first and second substrates that are each uniquely tilted and contoured relative to the XY plane, and a unique dispense height path corresponding to each dispense region.

[0033] FIG. 13B is a side elevational view showing first and second dispense regions provided on a single contoured substrate, and a unique dispense height path corresponding to each dispense region.

[0034] FIGS. 14A and 14B present a flow diagram illustrating steps of a method for simultaneously dispensing at first and second dispense regions.

DETAILED DESCRIPTION

[0035] Turning to FIGS. 4 and 5, an exemplary dual applicator fluid dispensing system 30 for dispensing viscous fluids at a plurality of dispense regions, such as independent substrates A, B, C, D held in a carrier tray 32, is shown schematically. While only four substrates A-D are shown herein, arranged in a rectangular configuration in corresponding pockets 33a, 33b, 33c, 33d, the carrier tray 32 may be adapted to carry any desired number of substrates arranged in any desired configuration. Alternatively, the multiple dispense regions may be distinct regions of a single substrate, as discussed above. In this regard, while dispense regions are primarily exemplified herein as multiple independent substrates, it will be appreciated that, alternatively, dispense regions may be part of single common substrate, for example as shown in FIG. 13B. In one embodiment, the dispense regions may be part of a panelized substrate, such as a panelized circuit board (not shown).

[0036] The carrier tray 32 may be positioned on a conveyor belt (not shown), which may be operated to deliver the carrier tray 32 to a position generally beneath the dispensing system 30 such that the substrates A-D carried therein may be dispensed upon by the dispensing system 30. Alternatively, the carrier tray 32 may be positioned on any other suitable platform, such as a stationary table or pedestal, located generally within an operating perimeter of the dispensing system 30. The dual dispensing system 30 includes a first fluid applicator 34 mounted to a primary positioner 36 and a second fluid applicator 38 mounted to a secondary positioner 40. The secondary positioner 40 is coupled to and movable by the primary positioner 36. The positioners 36, 40 collectively define a gantry 42 for positioning the first applicator 34 for dispensing at a first dispense region and the second applicator 38 for simultaneously dispensing at a second dispense region, as described in greater detail below.

[0037] The dual dispensing system 30 defines a global origin O and three mutually orthogonal global axes X, Y, and Z. The primary positioner 36 is movable in directions parallel to the global X, Y, and Z axes, denoted generally by x.sub.1, y.sub.1, and z.sub.1, respectively, and corresponding directional arrows. Similarly, the secondary positioner 40 is also movable in directions parallel to the global X, Y, and Z axes, denoted generally by x.sub.2, y.sub.2, and z.sub.2, respectively, and corresponding directional arrows.

[0038] The primary positioner 36 includes a pair of opposed x.sub.1 supports 44a and 44b aligned parallel with the X axis and shown generally as longitudinal beams. The x.sub.1 supports 44a, 44b are each provided with an x.sub.1 bearing 46a and 46b, respectively, shown as linear bearings, for enabling x.sub.1 linear movement of the applicators 34, 38 parallel to the X axis. The primary positioner 36 further includes a transversely oriented y.sub.1 support 48 aligned parallel with the Y axis and shown generally as a lateral beam. The y.sub.1 support 48 is provided with a pair of y.sub.1 bearings 50a and 50b, shown as linear bearings, for enabling y.sub.1 linear movement of the applicators 34, 38 parallel to the Y axis. The y.sub.1 support 48 is movably coupled to the x.sub.1 supports 44a, 44b through a pair of opposed legs 52a and 52b, which engage and are slidable along the x.sub.1 bearings 46a, 46b, respectively, for x.sub.1 movement. The primary positioner 36 further includes a y.sub.1 carriage 54 having a lower XY surface that engages and is slidable along the y.sub.1 bearings 50a, 50b for y.sub.1 movement. The y.sub.1 carriage 54 has a YZ surface (i.e., a surface lying in the YZ plane) to which is attached a vertically oriented z.sub.1 support 56, aligned parallel with the Z axis and shown generally in the form of a plate. The z.sub.1 support 56 includes a pair of vertically oriented z.sub.1 bearings 58a and 58b, shown as linear bearings, for enabling z.sub.1 linear movement of the applicators 34, 38 in a direction parallel to the Z axis. As shown, the z.sub.1 bearings 58a, 58b may be provided on adjacent XZ and YZ surfaces, respectively, of the z.sub.1 support 56. A z.sub.1 carriage 60, shown in the form of an L-shaped bracket, has a first leg 62a and a second leg 62b that engage and are slidable along the z.sub.1 bearings 58a, 58b, respectively, for z.sub.1 movement. A first applicator mounting mechanism 64 may be coupled to the second leg 62b and may be configured to releasably support the first applicator 34, as described in greater detail below.

[0039] The secondary positioner 40 is coupled to the primary positioner 36 and enables x.sub.2, y.sub.2, and z.sub.2 movements of the second applicator 38 relative to the primary positioner 36 and the first applicator 34 mounted thereon. The secondary positioner 40 includes a y.sub.2 support 70 which may act as a base plate and may be rigidly coupled at a YZ surface to the first leg 62a of the z.sub.1 carriage 60 of the primary positioner 36. The y.sub.2 support 70 may include a pair of y.sub.2 bearings 72a and 72b, shown as linear bearings, which may be positioned adjacent to each other on an opposed YZ surface of the y.sub.2 support 70. The y.sub.2 bearings 72a, 72b are aligned parallel with the Y axis to enable y.sub.2 movement of the second applicator 38 relative to the primary positioner 36. The secondary positioner 40 further includes a z.sub.2 support 74, shown generally as a plate. A YZ surface of the z.sub.2 support 74 may engage and be slidable along the y.sub.2 bearings 72a, 72b for y.sub.2 movement. An opposed YZ surface of the z.sub.2 support 74 may include a pair of z.sub.2 bearings 76a and 76b, shown as linear bearings, which are aligned parallel with the Z axis to enable z.sub.2 movement of the second applicator 38 relative to the primary positioner 36.

[0040] A z.sub.2 carriage 78, shown generally in the form of a plate, may include a YZ surface that engages and is slidable along the z.sub.2 bearings 76a, 76b for z.sub.2 movement. An x.sub.2 support 80 may be rigidly coupled to an XZ surface of the z.sub.2 carriage 78, in a perpendicular orientation. Alternatively, the x.sub.2 support 80 and the z.sub.2 carriage 78 may be formed integrally. The x.sub.2 support 80 may include an x.sub.2 bearing 82, shown as a linear bearing, that is aligned parallel with the X axis to enable x.sub.2 movement of the second applicator 38 relative to the primary positioner 36. A second applicator mounting mechanism 84 may engage and be slidable along the x.sub.2 bearing 82 for x.sub.2 movement, and may be configured to releasably support the second applicator 38, as described in greater detail below.

[0041] The first and second applicator mounting mechanisms 64, 84 may be configured to receive and releasably engage the first and second applicators 34, 38, respectively. For example, the applicator mounting mechanisms 64, 84 may each include a quick-disconnect feature (not shown) that enables proper alignment with the corresponding applicator 34, 38 through one or more projections and mating recesses. U.S. Pat. No. 6,214,117 and EP Patent No. 1 165 250 B1, the disclosures of which are hereby incorporated by reference herein, show prior art examples of quick disconnect mechanisms for mounting applicators to mechanisms for moving the applicators.

[0042] The first and second applicators 34, 38 may be of any preferred type suitable for a user's intended application, such as an air-operated needle valve or jet of the types made available by Nordson ASYMTEK of Carlsbad, Calif., for example. As shown best in FIGS. 4 and 5, each applicator 34, 38 may be in the form of a pneumatically operated jetting valve such as a model DJ 9000 valve available from Nordson ASYMTEK. As shown, each applicator 34, 38 may include a corresponding fluid reservoir 86, 88 for storing viscous fluid, an actuator 90, 92, for jetting, or dispensing, viscous fluid from a dispensing tip 94, 96 for application to a substrate A-D positioned beneath the dispensing tip 94, 96. An example of a suitable dispenser is shown in U.S. Pat. No. 8,578,729, the disclosure of which is hereby incorporated by reference herein. As discussed above, the viscous fluid may be any solder paste, underfill material, adhesive, or encapsulant, for example.

[0043] Movement of the primary and secondary positioners 36, 40 may be preferably accomplished through a series of controllable, powered drive mechanisms. More specifically, each direction of movement x.sub.1, y.sub.1, z.sub.1, x.sub.2, y.sub.2, and z.sub.2 may be powered by at least one corresponding powered drive mechanism. As shown, a pair of x.sub.1 drive mechanisms 100a and 100b may operate in parallel to power x.sub.1 movement along the x.sub.1 bearings 46a, 46b, respectively, and may be provided internally within or adjacent to the legs 52a, 52b, respectively. Alternatively, x.sub.1 movement may be powered by a single drive mechanism (not shown). A y.sub.1 drive mechanism 102 may power y.sub.1 movement along the y.sub.1 bearings 50a, 50b and may be provided internally within or adjacent to the y.sub.1 carriage 54, as shown. A z.sub.1 drive mechanism 104 may power z.sub.1 movement along the z.sub.1 bearings 58a, 58b and may be provided adjacent to an external XZ surface of the z.sub.1 support 56, as shown. A y.sub.2 drive mechanism 106 may power y.sub.2 movement along the y.sub.2 bearings 72a, 72b and may be provided adjacent to an external XZ surface of the y.sub.2 support 70, as shown. A z.sub.2 drive mechanism 107 may power z.sub.2 movement along the z.sub.2 bearings 76a, 76b and may be provided adjacent to an external upper XY surface of the z.sub.2 carriage 78, as shown. An x.sub.2 drive mechanism 108 may power x.sub.2 movement along the x.sub.2 bearing 82 and may be provided adjacent to an external YZ surface of the second applicator mounting mechanism 84, as shown.

[0044] In one embodiment, the drive mechanisms 100a, 100b, 102, 104, 106, 107, 108 may include stepper motors. Alternatively, the drive mechanisms 100a, 100b, 102, 104, 106, 107, 108 may include any other suitable electric, pneumatic, or hydraulic drive adapted to movement with a high degree of accuracy, repeatability, and stability. Additionally, the drive mechanisms 100a, 100b, 102, 104, 106, 107, 108 may include any additional mechanical drive elements suitable for moving the positioners 36, 40. For example, in one embodiment (not shown) the drive mechanisms 100a, 100b, 102, 104, 106, 107, 108 may include stepper motors each having an output shaft connected with a flexible drive coupling to a lead screw. The lead screw may rotate with the motor and engages a threaded or toothed element mounted on a corresponding support to actuate movement along a corresponding linear bearing. The drive mechanisms 100a, 100b, 102, 104, 106, 107, 108 may be mounted at any suitable locations within the dispensing system 30 different from those shown and described herein.

[0045] As presented above, the secondary positioner 40 is coupled to the primary positioner 36 and thus the x.sub.1, y.sub.1, and z.sub.1 movements of the primary positioner 36 are transferrable to the secondary positioner 40 and the second applicator 38 mounted thereon. The secondary positioner 40 enables additional movements x.sub.2, y.sub.2, and z.sub.2 relative to the primary positioner 36, which movements may be relatively fine in comparison to the corresponding x.sub.1, y.sub.1, and z.sub.1 movements performed by the primary positioner 36. Accordingly, in one embodiment, the secondary positioner 40 is movable with ranges of motion that are less than corresponding ranges of motion of the primary positioner 36. More specifically, the primary positioner may have a range of motion in each of the directions parallel to the X axis, the Y axis, and the Z axis (i.e., x.sub.1, y.sub.1, and z.sub.1 movements). Similarly, the secondary positioner 40 may have a range of motion in each of the directions parallel to the X axis, the Y axis, and the Z axis (i.e., x.sub.2, y.sub.2, and z.sub.2 movements). The ranges of motion of the secondary positioner 40 may be smaller than the corresponding ranges of motion of the primary positioner 36. In this manner, the primary positioner 36 may perform a primary movement to move the first applicator 34 and the second applicator 38, the primary movement defined by any one or combination of x.sub.1, y.sub.1, and z.sub.1 movements and having a magnitude. Simultaneously, the secondary positioner 40 may perform a secondary movement relative to the primary positioner 36 to move the second applicator 38 relative to the first applicator 34, the secondary movement defined by any one or combination of x.sub.2, y.sub.2, and z.sub.2 movements and having a magnitude that is less than the magnitude of the primary movement.

[0046] Accordingly, the first applicator 34 may be positioned with the primary positioner 36, and the second applicator 38 may be jointly positioned by the primary positioner 36 and the secondary positioner 40. More specifically, the first applicator 34 and the second applicator 38 are both positionable with y.sub.1, and z.sub.1 movements. The second applicator 38 is additionally positionable with x.sub.2, y.sub.2, and z.sub.2 movements made relative to the primary positioner 36. Thus, the structural configuration of the dispensing system 30 enables the second applicator 38 to be moved relative to the first applicator 34 in directions parallel to the X, Y, and Z axes. Thereby, the first and second applicators 34, 38 may simultaneously dispense first and second fluid patterns onto first and second substrates, respectively, where the fluid patterns are substantially identical in size and shape and where the substrates are misaligned relative to each other. As described above, the fluid patterns may include one or more lines, arcs, dots, combinations thereof, and/or any other configuration of continuously or intermittently dispensed fluid.

[0047] The primary positioner 36 and the secondary positioner 40 are independently controllable with at least one controller (not shown), such as a computer. Preferably, the controller is configured to instruct the x.sub.1, y.sub.1, and z.sub.1 movements of the primary positioner 36, and to simultaneously instruct the x.sub.2, y.sub.2, and z.sub.2 movements of the secondary positioner 40 by controlling the drive mechanisms 100a, 100b, 102, 104, 106, 107, 108. In this manner, the primary positioner 36 is controllable such that the first applicator 34 may be properly positioned relative to and dispense at a first dispense region, such as substrate A. Simultaneously, the secondary positioner 40 is independently controllable such that the second applicator 38 may be properly positioned relative to and dispense at a second dispense region, such as substrate B. As discussed in greater detail below, the positioners 36, 40 are controllable to account for misalignment between a first dispense region and a second dispense region, such as substrates A and B, for example.

[0048] Having just described a dispensing system that is novel in structure, methods of simultaneously dispensing at first and second dispense regions will now be described. The methods are described herein with reference to substrates A, B, C, D shown in FIGS. 6-11. As discussed above, persons skilled in the art will appreciate that the dispensing methods described herein may be adapted for simultaneously dispensing at any two dispense regions of a plurality of dispense regions with the dispensing system 30. For example, first and second dispense regions may be part of a single substrate, such as a panelized substrate.

[0049] The dispensing system 30 may first identify the location and orientation of each substrate A, B, C, D in the XY plane relative to a global origin O, based on the positions of at least two reference fiducials 110a, 110b provided on each substrate A-D. For example, with reference to substrate A, the two fiducials 110a, 110b may be provided at opposing corners of an upper XY surface of the substrate A. While shown herein as an “x” enclosed by a circle, the fiducials 110a, 110b may be any identifiable mark such as a letter, number, dot, or pattern, for example. In this manner, the dispensing system 30 may determine whether each substrate is rotated and/or translated in the XY plane relative to a corresponding reference position defined with respect to origin O.

[0050] The dual dispensing system 30 includes a camera 112 for identifying the reference fiducials 110a, 110b. The camera 112 may be mounted to the gantry 42 at any suitable location, such as a portion of the secondary positioner 40, as shown in FIG. 6. For fiducial identification, the gantry 42 may be controlled to move the camera 112 along a pre-programmed path based on expected locations of the fiducials 110a, 110b in the XY plane. In one mode, the gantry 42 may be controlled to sequentially pause at the expected location of each fiducial 110a, 110b so that the camera 112 may capture a visual image of a fiducial 110a, 110b during each pause. In another mode, the gantry 42 may be controlled to continuously move and the camera 112 may capture visual images of the fiducials 110a, 110b during movement. Based on the images of the fiducials 110a, 110b captured by the camera 112, the controller may then determine the actual position of each substrate A, B, C, D in the XY plane.

[0051] The dual dispensing system 30 further includes a height sensor 114 for performing height sensing operations, which includes measuring the position of each substrate A-D along the Z axis, relative to the XY plane. The height sensor 114 may be a non-contact laser sensor, or alternatively may be a contact mechanical sensor. In operation, the gantry 42 may be controlled to move the height sensor 114 along a pre-programmed path for measuring the position each substrate A-D along the Z axis. These measurements, referred to herein as Z height measurements, enable the controller to determine for each substrate A-D a proper height along the Z axis, referred to as a dispense height, to which the dispensing tip 94, 96 of the first or second applicator 34, 38 should be lowered for dispensing fluid onto the substrate A-D. In this manner, the system 30 may ensure a proper dispense gap between the dispensing tips 94, 96 and the corresponding substrates A-D while dispensing.

[0052] As shown in FIG. 6, the substrates A-D may lie generally parallel to the XY plane, and thus a single height measurement for each substrate A-D may be sufficient. Alternatively, one or more of the substrates A-D may be tilted relative to the XY plane (see, e.g., FIGS. 3A, 12A) such that the substrate is positioned at various points along the Z axis. In such case, the height sensor 114 may be operated to measure multiple heights of the tilted substrate and thereby map the tilt along the Z axis. Similarly, multiple Z height measurements may also be collected for a substrate having a surface, onto which fluid is to be dispensed, that is contoured relative to the XY plane and along the Z axis (referred to herein as a “contoured substrate,” and similar variations thereof), as shown in FIGS. 12B-13B. As described in greater detail below, the multiple Z height measurements collected for a tilted and/or contoured substrate may then be used by the controller to determine z.sub.1 or z.sub.2 movements that the primary positioner 36 or the secondary positioner 40 must actively perform during dispensing in order to accommodate the tilted orientation of the substrate or its contoured surface. The camera 112 and height sensor 114 may be integrated into a single system operable by the controller for collecting fiducial information and height measurements for each of the substrates A-D to be dispensed upon.

[0053] Based on the information gathered by the controller during the fiducial locating and height sensing operations described above, the primary and secondary positioners 36, 40 may be operated to simultaneously position the first applicator 34 relative to a first substrate and the second applicator 38 relative to a second substrate. The first applicator 34 may then dispense a first fluid pattern onto the first substrate while the second applicator 38 simultaneously dispenses a second, identical fluid pattern onto the second substrate. The positioners 36, 40 are automatically movable while dispensing to actively correct for any positional misalignment of one of the substrates relative to the other. These positioning and dispensing steps may be performed with respect to any two of the substrates A-D, for example, which are each rotated and/or translated along the X and Y axes relative to each of the other substrates A-D, as shown in FIGS. 6-11.

[0054] FIGS. 7-11 show a series of steps in which the first applicator 34 is positioned relative to substrate A and dispenses a fluid pattern 116 thereon. Simultaneously, the second applicator 38 is positioned relative to substrate B and dispenses a substantially identical fluid pattern 118 thereon. Substrates A and B are shown each misaligned from their respective centered positions within their respective pockets 33a, 33b (see, e.g., FIG. 2). The geometric centers of the pockets 33a, 33b in the XY plane are represented by crosshairs. As shown, substrate A is rotated from its centered position relative to the X and Y axes, while substrate B is translated from its centered position along the X and Y axes. Accordingly, substrates A and B are rotated and translated relative to each other with respect to the X and Y axes. As described below, the second applicator 38 is movable in the XY plane relative to the first applicator 34 while dispensing to thereby actively and automatically correct for misalignments of the substrates A, B in the XY plane.

[0055] As shown, the first and second applicator dispensing tips 94, 96 are each represented in FIGS. 7-11 by a pair of concentric phantom circles. The shapes of the fluid patterns 116, 118 to be dispensed are represented by directional arrows forming generally rectangular outlines about the perimeters of components 120a, 120b provided on the substrates A, B. Accordingly, FIGS. 7-11 simulate dispensing of an adhesive underfill material which is dispensed along the edge of a component, such as a flip chip having a grid of solder balls on its underside which are positioned on corresponding matching contact pads on the substrate, with the underfill material flowing under the chip and around the solder balls to secure the flip chip to the substrate. Persons of ordinary skill in the art will appreciate that the positioners 36, 40 and the applicators 34, 38 mounted thereon may be controlled to dispense fluid patterns of any other desired shape and at any other desired region of one or more substrates or other similar workpieces. For example, as discussed above, the fluid patterns may include one or more lines, arcs, dots, combinations thereof, and/or any other configuration of continuously or intermittently dispensed fluid.

[0056] Referring to FIG. 7, the controller may command the primary positioner 36 to execute x.sub.1 and y.sub.1 movements to thereby position the first applicator dispensing tip 94 to overlie a first dispense site 122 on substrate A. Simultaneously, the controller may command the secondary positioner 40 to execute x.sub.2 and y.sub.2 movements relative to the primary positioner 36 to thereby position the second applicator dispensing tip 96 over a corresponding first dispense site 124 on substrate B. The controller may then command the primary positioner 36 to execute downward z.sub.1 movement to thereby advance the first and second dispensing tips 94, 96 simultaneously toward their proper dispense heights, as determined during the height sensing operation described above. If the controller determines, through the height sensing operation, that substrates A and B are each positioned at the same location along the Z axis, the first and second dispensing tips 94, 96 may be positioned at the same dispense height through z.sub.1 movement of the primary positioner 36. If the controller determines, through the height sensing operation, that substrates A and B are positioned at different locations along the Z axis, the controller may additionally command the secondary positioner 40 to execute z.sub.2 movement relative to and simultaneously with the z.sub.1 movement of the primary positioner 36. Thereby, the first and second dispensing tips 94, 96 may be simultaneously positioned at their proper, respective dispensing heights. The dispensing system 30 may now dispense onto substrates A and B.

[0057] As shown in FIG. 8, the first applicator 34 and its dispensing tip 94 may be moved by the primary positioner 36 to dispense a first leg 116a of fluid pattern 116. Simultaneously, the second applicator 38 and its dispensing tip 96 may be moved by the secondary positioner 40 relative to the primary positioner 36 and the first applicator 34 to dispense a first leg 118a of fluid pattern 118. More specifically, the controller may command the primary positioner 36 to execute x.sub.1 and y.sub.1 movements, and further command the secondary positioner 40 to simultaneously execute corrective x.sub.2 and y.sub.2 movements relative to the primary positioner 36. The controller may issue such commands based on the known locations and orientations of the substrates A, B in the XY plane as determined by the controller during the fiducial identification process described above. In this manner, the dispensing system 30 may automatically and actively adjust positioning of the first and second applicators 34, 38 while dispensing to correct for local rotation of substrates A and B.

[0058] As shown in FIG. 9, the first applicator 34 and its dispensing tip 94 may be moved by the primary positioner 36 to dispense a second leg 116b of fluid pattern 116. Simultaneously, the second applicator 38 and its dispensing tip 96 may be moved by the secondary positioner 40 relative to the primary positioner 36 and the first applicator 34 to dispense a second leg 118b of fluid pattern 118. More specifically, the controller may command the primary positioner 36 to execute x.sub.1 and y.sub.1 movements, and further command the secondary positioner 40 to simultaneously execute corrective x.sub.2 and y.sub.2 movements relative to the primary positioner 36 while dispensing to correct for the local rotation of substrates A and B.

[0059] As shown in FIG. 10, the first applicator 34 and its dispensing tip 94 may be moved by the primary positioner 36 to dispense a third leg 116c of fluid pattern 116. Simultaneously, the second applicator 38 and its dispensing tip 96 may be moved by the secondary positioner 40 relative to the primary positioner 36 and the first applicator 34 to dispense a third leg 118c of fluid pattern 118. More specifically, and as similarly performed when dispensing the first legs 116a, 118a, the controller may command the primary positioner 36 to execute x.sub.1 and y.sub.1 movements, and simultaneously the controller may command the secondary positioner 40 to execute corrective x.sub.2 and y.sub.2 movements relative to the primary positioner 36 to correct for the local rotation of substrates A and B.

[0060] As shown in FIG. 11, the first applicator 34 and its dispensing tip 94 may be moved by the primary positioner 36 to dispense a fourth leg 116d of fluid pattern 116. Simultaneously, the second applicator 38 and its dispensing tip 96 may be moved by the secondary positioner 40 relative to the primary positioner 36 and the first applicator 34 to dispense a fourth leg 118d of fluid pattern 118, thereby completing the fluid patterns 116, 118. More specifically, and as similarly performed when dispensing the second legs 116b, 118b, the controller may command the primary positioner 36 to execute x.sub.1 and y.sub.1 movements, and simultaneously the controller may command the secondary positioner 40 to execute corrective x.sub.2 and y.sub.2 movements relative to the primary positioner 36 to correct for the local rotation of substrates A and B.

[0061] One or both of the substrates A, B may be tilted relative to the XY plane, as demonstrated by substrate 130 in FIG. 12A. As described above, the height sensor 114 may be operated to collect multiple height measurements of a tilted substrate along the Z axis, and these measurements may then be conveyed to the controller. As shown in FIG. 12A, the controller may then determine a dispense height path P that varies in height along the Z axis and along which a corresponding dispensing tip 94, 96 may be moved in order to maintain a constant and accurate dispense gap G between the tip 94, 96 and the tilted substrate 130. Thus, if the substrate B of FIGS. 7-11, and its corresponding component 120b, had a tilt like that shown for substrate 130, in addition to making the x.sub.2 and y.sub.2 corrections as described above, the secondary positioner 40 would make corrective z.sub.2 movements relative to the primary positioner 36, while dispensing, to correct for the tilt of substrate B with respect to substrate A. In this manner, the system 30 may accurately dispense a fluid pattern, such as pattern 118, onto the tilted substrate. Consequently, as shown in FIG. 12A, corrective z.sub.2 movements would be made along the Z axis such that the dispensing tip 96 travels in a plane substantially parallel to the tilted substrate.

[0062] A similar process may be performed where one or both of the substrates A, B is contoured relative to the XY plane, along the Z axis, as demonstrated by substrate 132 in FIG. 12B, which could be a warped substrate, for example. In particular, the system may collect multiple Z height measurements corresponding to a contoured substrate. As shown in FIG. 12B, the system 30 may then determine a corresponding dispense height path P that varies in height along the Z axis and along which a corresponding dispensing tip 94, 96 may be moved in order to maintain a constant and accurate dispense gap G between the tip 94, 96 and the contoured substrate 132. The process described above with respect to the tilted substrate shown in FIG. 12A may also be applied to contoured substrates. For example, if the substrate B shown in FIGS. 7-11 had a contour like that shown for substrate 132, in addition to making the x.sub.2 and y.sub.2 corrections as described above, the secondary positioner 40 would also make corrective z.sub.2 movements relative to the primary positioner 36, while dispensing, to correct for the contour of substrate B with respect to substrate A. In this manner, the system 30 may accurately dispense a fluid pattern, such as fluid pattern 118, onto the contoured substrate. Consequently, as shown in FIG. 12B, corrective z.sub.2 movements would be made along the Z axis such that the dispensing tip 96 travels along a path that substantially conforms to the contoured substrate.

[0063] As demonstrated by substrates 134 and 136 in FIG. 13A, two substrates being dispensed upon, for example substrates A and B, may each be uniquely tilted and contoured relative to the XY plane and relative to each other, and corresponding dispense height paths P1 and P2 may be determined by the system 30 based on the detected Z height measurements. In another embodiment, instead of using a height sensor, electronic data defining the tilt and/or contour of a substrate may be entered into the system 30 by a user. Such electronic data may then be used to determine a dispense height path.

[0064] In another embodiment (not shown), first and second substrates may be arranged such that they are not rotated relative to each other in the XY plane, and each substrate is provided with the same tilt and/or contour relative to the XY plane such that the substrates are not uniquely tilted or contoured relative to each other. In such case, the dispense height paths determined by the system 30 for the substrates may be substantially identical, and the secondary positioner 40 need not make corrective movements relative to the primary positioner 36 during dispense. In other words, the first and second applicators may remain stationary relative to each other while moving together along X, Y, and Z to simultaneously dispense on the first and second substrates.

[0065] With reference to substrates A and B of FIGS. 6-11, a first scenario, also described above, may arise in which substrate A is generally planar and lies parallel to the XY plane, and substrate B is tilted relative to the XY plane and/or includes a contoured surface, as demonstrated by substrates 130 and 132 of FIGS. 12A and 12B. In such case, the controller may determine a dispense height path for tilted and/or contoured substrate B based on height measurements collected during the height sensing operation discussed above. Then, while the first applicator 34 is moved in the XY plane to dispense onto substrate A and the second applicator 38 is simultaneously moved in the XY plane to dispense onto substrate B, the controller may command the secondary positioner 40 to simultaneously execute z.sub.2 movements relative to the primary positioner 36. Thereby, the second dispensing tip 96 is movable along the pre-determined dispense height path while the second applicator 38 dispenses onto tilted and/or contoured substrate B. In this manner, the dispensing system 30 may automatically and actively adjust the positioning of the second applicator 38 along the Z axis to correct for tilt and/or contour of substrate B relative to the XY plane.

[0066] In a second scenario, substrate A may be tilted and/or contoured relative to the XY plane, as demonstrated by substrates 130 and 132 of FIGS. 12A and 12B, while substrate B is generally planar and lies parallel to the XY plane. In such case, the controller may determine a dispense height path for tilted and/or contoured substrate A in a manner as described above. Then, while the first applicator 34 is moved in the XY plane to dispense onto tilted and/or contoured substrate A, the controller may command the primary positioner 36 to simultaneously execute z.sub.1 movements. Thereby, the first dispensing tip 94 is movable along the pre-determined dispense height path while the first applicator 34 dispenses onto tilted and/or contoured substrate A. Simultaneously, the second applicator 38 is moved in the XY plane to dispense onto substrate B, and the controller may command the secondary positioner 40 to execute z.sub.2 movements relative to the primary positioner 36, the z.sub.2 movements being substantially opposite of the z.sub.1 movements made by the primary positioner 36. Thereby, the second dispensing tip 96 may be maintained at a constant, pre-determined dispense height corresponding to substrate B while the second applicator 38 dispenses onto part B.

[0067] In a third scenario, both substrates A and B may be tilted and/or contoured relative to the XY plane. By way of example with reference to FIG. 13A, substrate A may correspond to substrate 134 and substrate B may correspond to substrate 136. In this regard, substrate A may be provided with a first tilt and/or a first contour that is unique to substrate A, and substrate B may be provided with a second tilt and/or a second contour that is unique to substrate B. The controller may determine a first dispense height path P1 corresponding to tilted and/or contoured substrate A and a second dispense height path P2 corresponding to tilted and/or contoured substrate B, in a manner as described above. Then, while the first applicator 34 is moved in the XY plane to dispense onto substrate A, the controller may command the primary positioner 36 to simultaneously execute z.sub.1 movements. Thereby, the first dispensing tip 94 is movable along the first dispense height path P1 to maintain a first dispense gap G1, while the first applicator 34 dispenses onto substrate A. Simultaneously, while the second applicator 38 is moved in the XY plane to dispense onto tilted and/or contoured substrate B, the controller may command the secondary positioner 40 to execute z.sub.2 movements relative to the primary positioner 36 to correct both for the z.sub.1 movements executed by the primary positioner 36 and the unique tilt and/or contour of substrate B. Thereby, the second dispensing tip 96 is movable along the second dispense height path P2 to maintain a second dispense gap G2, while the second applicator 38 dispenses onto substrate B. In this manner, the first applicator 34 may accurately dispense onto a uniquely tilted and/or contoured first substrate and simultaneously the second applicator 38 may accurately dispense onto a uniquely tilted and/or contoured second substrate.

[0068] In an alternative embodiment similar to the third scenario described above, the first and second applicators 34, 38 may simultaneously dispense first and second fluid patterns at first and second dispense regions, respectively, that are each distinct regions of a single common substrate. For example, as shown in FIG. 13B, the primary positioner 36 may execute z.sub.1 movements to move the first applicator 34 along a first dispense height path P1 at a first uniquely contoured dispense region of substrate 138. Thereby, a first dispense gap G1 associated with the first dispense region may be maintained while dispensing. Simultaneously, the secondary positioner 40 may execute z.sub.2 movements to move the second applicator 38 along a second dispense height path P2 at a second uniquely contoured dispense region of the substrate 138. Thereby, a second dispense gap G2 associated with the second dispense region may be maintained while dispensing. In various embodiments, the first and second dispense gaps G1, G2 may be the same or they may be different.

[0069] In a fourth scenario, substrates A and B may both be generally planar and lie parallel to the XY plane but positioned at different distances along the Z axis relative to the XY plane. For example, substrate A may lie in the XY plane, while substrate B is spaced above the XY plane. In such case, neither substrate A nor B is tilted or contoured relative to the XY plane, and thus active correction along the Z axis during dispense is not required by either applicator 34, 38. The controller may determine an appropriate dispense height for each substrate A, B in the manner described above. Prior to dispensing, the controller may command the primary positioner 36 to execute z.sub.1 movement to lower the first dispensing tip 94 to its corresponding dispense height along the Z axis above substrate A. Simultaneously, the controller may command the secondary positioner 40 to execute z.sub.2 movement relative to the primary positioner 36 to lower the second dispensing tip 96 to its corresponding dispense height along the Z axis above substrate B. The controller may then command the primary positioner 36 to move the first and second applicators 34, 38 together in the XY plane so that they may simultaneously dispense first and second fluid patterns onto substrates A and B, respectively, while maintaining the corresponding dispense heights for the applicators 34, 38.

[0070] In view of the disclosure above, persons of ordinary skill in the art will appreciate that the dispensing system 30 is capable of executing x.sub.1, y.sub.1, and z.sub.1 movements with the primary positioner 36 and simultaneously executing x.sub.2, y.sub.2, and z.sub.2 movements with the secondary positioner 40. Moreover, these movements are executable while the first applicator 34 dispenses at a first dispense region, such as a first substrate, and the second applicator 38 simultaneously dispenses at a second dispense region, such as a second substrate. In this manner, the dispensing system 30 is controllable to automatically and actively adjust positioning of the first and second applicators 34, 38 while dispensing to correct for misalignment of first and second substrates being dispensed upon.

[0071] FIGS. 14A and 14B present a flow diagram illustrating steps of a method 200 according to one embodiment of the invention for simultaneously dispensing at first and second dispense regions in a manner consistent with the disclosure above. The method 200 may be performed with dispensing system 30 or any suitable variation thereof, for example. The referenced dispense regions are denoted “DR.” As described above, the first and second dispense regions may be first and second substrates, or they may be distinct first and second regions of a single substrate, such as a panelized circuit board. The referenced first and second applicators are denoted “A1” and “A2,” and may be mounted to and movable by primary and secondary positioners, respectively, such as positioners 36 and 40 of dispensing system 30 disclosed above.

[0072] At step 202, the dispensing system first identifies reference fiducials associated with each of the plurality of dispense regions, for example in the manner described above. In one embodiment, each dispense region may be provided with its own set of corresponding reference fiducials. In another embodiment, multiple dispense regions may be associated with a single set of reference fiducials, for example where the dispense regions are regions of a single substrate. At step 204, the system then determines the location and orientation (i.e., the position) of each dispense location in the XY plane defined by the system, based on the identified reference fiducials. At step 206, the system then collects Z height measurements for the dispense regions through height sensing. As described above, such height sensing may include collecting multiple height measurements for dispense regions that are tilted and/or contoured relative to the XY plane. For example, such height sensing may include collecting multiple height measurements of a path along which fluid is to be dispensed, the path encompassed by a dispense region. Alternatively, as described above, the system may consult surface contour data entered by a user for providing the Z heights.

[0073] At step 208, the system may select first and second dispense regions from the plurality of dispense regions, and assign a first applicator A1 for dispensing a first fluid pattern at the first dispense region and a second applicator A2 for dispensing a second fluid pattern at the second dispense region. At step 210, the system then assesses, for each of the selected first and second dispense regions, whether the dispense region is tilted and/or contoured relative to the XY plane, along the Z axis. If the dispense region is not tilted or contoured, the system may proceed to step 212 and determine a proper dispense height for the applicator assigned to the dispense region, based on a single Z height previously measured for the dispense region, as described above. Alternatively, at step 214, where the dispense region is tilted and/or contoured relative to the XY plane, the system may determine a corresponding dispense height path based on multiple Z heights that were previously measured for the dispense region or otherwise provided by external data entered by a user, as described above. For example, where each dispense region is uniquely tilted and/or contoured (see FIGS. 13A and 13B), the system may determine a unique dispense height path corresponding to each dispense region. At step 216, the system may then adjust, as appropriate, the control algorithms associated with an applicator assigned to a tilted and/or contoured dispense region to account for tilt and/or contour of the surface that will be dispensed upon. For example, the control algorithms of an applicator assigned to a tilted and/or contoured dispense region may be adjusted so that the applicator selectively dispenses fluid from a proper height or heights dependent on the dispense height path while moving in directions having X and Y components of movement, to dispense a fluid pattern.

[0074] At steps 218a and 218b, the system positions the first applicator in the XY plane above a first dispense site at the first dispense region. Simultaneously, the system may move the second applicator relative to the first applicator in the XY plane to position the second applicator above a first dispense site at the second dispense region. At step 220, the system then simultaneously lowers the first and second applicators along the Z axis to their respective dispense heights, as determined above in steps 210-214. If a dispense region is tilted and/or contoured, its applicator may be lowered to an initial dispense height positioned within the dispense height path. At step 222, the first and second applicators are controlled to start dispensing fluid at the respective dispense regions positioned below.

[0075] Starting at step 224, the first and second applicators are moved along the X, Y, and/or Z axes to dispense the first and second fluid patterns, respectively, according to whether either of the first and second dispense regions is tilted and/or contoured relative to the XY plane, and/or rotated in the XY plane relative to the other dispense region (i.e., locally rotated). At step 226, if neither dispense region is tilted or contoured and there is no local rotation, the system may proceed to step 228 and move the first and second applicators together in the XY plane to dispense the first and second fluid patterns. For example, such may be accomplished with the primary positioner 36 of dispensing system 30 through x.sub.1 and y.sub.1 movements. Through step 228, the second applicator need not be moved relative to the first applicator while dispensing, because the dispense regions are neither tilted nor contoured relative to the XY plane, nor rotated relative to each other in the XY plane. In alternative to step 228, if the dispense regions are rotated relative to each other in the XY plane, the system proceeds to steps 230a and 230b. At steps 230a and 230b, the system moves the first applicator in the XY plane, for example with primary positioner 36, to dispense the first fluid pattern at the first dispense region. Simultaneously, the system moves the second applicator relative to the first applicator in the XY plane, for example with secondary positioner 40, to dispense the second fluid pattern at the second dispense region. Thereby, the system may actively correct for local rotation while dispensing.

[0076] In an alternative to step 226, if the first dispense region and/or the second dispense region is tilted and/or contoured relative to the XY plane, the system may proceed to step 232. Through step 232, the system moves the first and second applicators according to whether the first and second dispense regions are rotated relative to each other in the XY plane (i.e., locally rotated). If the dispense regions are not locally rotated, the system may proceed to steps 234a and 234b. At steps 234a and 234b, the system may move the first and second applicators together in the XY plane, as indicated in step 234a, for example with primary positioner 36, to dispense the first and second fluid patterns without relative movement between the applicators in XY. Simultaneously, as indicated in step 234b, the system may move the first applicator and/or the second applicator in Z along a corresponding dispense height path (determined in step 214) to account for tilt and/or contour of a corresponding dispense region relative to the XY plane.

[0077] In alternative to steps 234a and 234b, if the dispense regions are locally rotated in addition to at least one of them being tilted and/or contoured, the system may proceed to steps 236a, 236b, and 236c. At step 236a, the first applicator is moved in the XY plane, for example with primary positioner 36, to dispense the first fluid pattern at the first dispense region. Simultaneously, at step 236b, the second applicator is moved relative to the first applicator in the XY plane, for example with secondary positioner 40, to dispense the second fluid pattern at the second dispense region. Simultaneously, at step 236c, the first applicator and/or the second applicator is moved in Z along a corresponding dispense height path to account for tilt and/or contour of a corresponding dispense region relative to the XY plane.

[0078] At step 238, upon completion of dispensing the first and second fluid patterns, the first and second applicators may be raised back up along the Z axis to their pre-dispense heights, for example. At step 240, the system may evaluate whether there are additional fluid patterns to be dispensed, for example at third and fourth dispense regions. If there remains additional dispensing to be performed, the system may return to step 208, as indicated by symbol B. If all dispensing is complete, the system may end its dispensing operations.

[0079] Methods of dispensing have been described above in connection with specified orientations of first and second dispense regions and corresponding movements of first and second applicators for simultaneously dispensing at the first and second dispense regions. However, persons skilled in the art will appreciate that the methods described may be adapted as appropriate to simultaneously dispense at any two dispense regions. For example, where the first dispense region and/or the second dispense region is uniquely tilted and/or contoured relative to the XY plane, the system may move the first applicator and the second applicator independently along X, Y, and/or Z while dispensing to simultaneously dispense a first fluid pattern at the first dispense region and a second fluid pattern at the second dispense region.

[0080] While the present invention has been illustrated by the description of specific embodiments thereof, and while the embodiments have been described in considerable detail, it is not intended to restrict or in any way limit the scope of the appended claims to such detail. The various features discussed herein may be used alone or in any combination. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope or spirit of the general inventive concept.