Patent Description:
There are several types of dispensing systems used for dispensing precise amounts of liquid or paste for a variety of applications. One such application is the assembly of integrated circuit chips and other electronic components onto circuit board substrates. In this application, automated dispensing systems are used for dispensing dots of liquid epoxy or solder paste, or some other related material, onto printed circuit boards. Automated dispensing systems are also used for dispensing lines of underfill materials and encapsulants, which may be used to mechanically secure components to the printed circuit board. Exemplary dispensing systems described above include those manufactured and distributed by Illinois Tool Works Electronic Assembly Equipment (ITWEAE), with offices at Hopkinton, Massachusetts.

In a typical dispensing system, a dispensing unit is mounted to a moving assembly or gantry for moving the dispensing unit along three mutually orthogonal axes (x-axis, y-axis, and z-axis) using servomotors controlled by a computer system or controller. To dispense a dot of liquid on a printed circuit board or other substrate at a desired location, the dispensing unit is moved along the co-planar horizontal x-axis and y-axis directions until the dispensing unit is located over the desired location. The dispensing unit is then lowered along the perpendicularly oriented vertical z-axis direction until a nozzle/needle of the dispensing unit and dispensing system is at an appropriate dispensing height over the substrate. The dispensing unit dispenses a dot of liquid, is then raised along the z-axis, moved along the x- and y-axes to a new location, and is lowered along the z-axis to dispense the next liquid dot. For applications such as encapsulation or dispensing of underfill as described above, the dispensing unit is typically controlled to dispense lines of material as the dispensing unit is moved in the x- and y-axes along the desired path of the lines. For some types of dispensing units, such as jetting pumps, the z-axis movement prior to and subsequent to a dispense operation may not be required.

In designing a dispensing unit or head, accurate placing of viscous material on the substrate is desired. Reduction of vibration is of particular interest.

One aspect of the present disclosure is directed to a dispensing system for dispensing viscous material on an electronic substrate. In one embodiment, the dispensing system comprises a frame, a support coupled to the frame, the support being configured to receive and support an electronic substrate during a dispense operation, a dispensing unit assembly configured to dispense viscous material, and a gantry coupled to the frame, the gantry being configured to support the dispensing unit assembly and to move the dispensing unit assembly in x-axis and y-axis directions. The dispensing unit assembly includes a support bracket secured to the gantry, a movable bracket rotatably coupled to the support bracket configured to enable the rotation of the movable bracket with respect to the support bracket about a first axis, a dispensing unit rotatably coupled to the movable bracket configured to enable the rotation of the dispensing unit with respect to the movable bracket about a second axis generally perpendicular to the first axis, and a mass dampener assembly coupled to the movable bracket, the mass dampener assembly being configured to reduce vibration of the dispensing unit during operation.

Embodiments of the dispensing system further may include the mass dampener assembly having a mass dampener coupled to the movable bracket by at least one isolator. The mass dampener assembly further may include a mounting plate configured to mount the mass dampener to the movable bracket. The mass dampener further may include at least one bumper configured to prevent at least one side wall of the mass dampener from engaging the movable bracket. The mass dampener assembly may be approximately <NUM>% to <NUM>% by weight of the dispensing unit. The mass dampener assembly may be approximately <NUM>% by weight of the dispensing unit assembly. The movable bracket may be configured to rotate with respect to the support bracket up to an entire <NUM> degrees and the dispensing unit is configured to rotate with respect to the movable bracket up to an entire <NUM> degrees. The gantry may include a z-axis drive mechanism coupled to the dispensing unit to provide z-axis movement of the dispensing unit. The gantry further may include a beam configured to move in a y-axis direction, and a carriage coupled to the beam, with the carriage being configured to move in an x-axis direction. The carriage includes the z-axis mechanism to provide the z-axis movement of the dispensing unit. The support bracket may be L-shaped in construction having a first portion coupled to the gantry and a second portion that extends perpendicularly from the first portion, with the first portion of the support bracket being secured to the z-axis drive mechanism to provide the z-axis movement of the dispensing unit. The dispensing system further may include a vision system coupled to one of the frame and the gantry to capture at least one image of the electronic substrate. The dispensing system further may include a controller configured to control dispensing unit assembly, the gantry and the vision system to perform a dispense operation on the electronic substrate.

Another aspect of the present disclosure is directed to a method of dispensing viscous material on an electronic substrate. In one embodiment, the method comprises: delivering an electronic substrate to a dispense position; capturing at least one image of the electronic substrate; analyzing the at least one image of the electronic substrate to determine a position of the electronic substrate; and performing a dispense operation by rotating a dispensing unit coupled to a support bracket by a movable bracket. The movable bracket is rotatably coupled to the support bracket and configured to enable the rotation of the movable bracket with respect to the support bracket about a first axis. The dispensing unit is rotatably coupled to the movable bracket and configured to enable the rotation of the dispensing unit with respect to the movable bracket about a second axis generally perpendicular to the first axis. The dispensing unit includes a mass dampener assembly coupled to the movable bracket, with the mass dampener assembly being configured to reduce vibration of the dispensing unit during operation.

Embodiments of the method further may include the mass dampener assembly having a mass dampener coupled to the movable bracket by at least one isolator. The mass dampener assembly further may include a mounting plate configured to mount the mass dampener to the movable bracket. The mass dampener further may include at least one bumper configured to prevent at least one side wall of the mass dampener from engaging the movable bracket. The mass dampener assembly may be approximately <NUM>% to <NUM>% by weight of the dispensing unit. The mass dampener assembly may be approximately <NUM>% by weight of the dispensing unit assembly. The movable bracket may be configured to rotate with respect to the support bracket up to an entire <NUM>-degrees and the dispensing unit is configured to rotate with respect to the movable bracket up to an entire <NUM> degrees. The method further may include moving the dispensing unit in a z-axis direction.

Various embodiments of the present disclosure are directed to viscous material dispensing systems, devices including dispensing systems. Embodiments disclosed herein are directed to techniques for dispensing material on an electronic substrate by a dispensing system having a dispensing unit that is configured to tilt and rotate to dispense material onto the electronic substrate and to eliminate unwanted vibration during the dispensing process.

For the purposes of illustration only, and not to limit the generality, the present disclosure will now be described in detail with reference to the accompanying figures. This disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The principles set forth in this disclosure are capable of other embodiments and of being practiced or carried out in various ways. Any references to examples, embodiments, components, elements or acts of the systems and methods herein referred to in the singular may also embrace embodiments including a plurality, and any references in plural to any embodiment, component, element or act herein may also embrace embodiments including only a singularity. References in the singular or plural form are not intended to limit the presently disclosed systems or methods, their components, acts, or elements. The use herein of "including," "comprising," "having," "containing," "involving," and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. References to "or" may be construed as inclusive so that any terms described using "or" may indicate any of a single, more than one, and all of the described terms. In addition, in the event of inconsistent usages of terms between this document and documents incorporated herein by reference, the term usage in the incorporated reference is supplementary to that of this document; for irreconcilable inconsistencies, the term usage in this document controls.

<FIG> schematically illustrates a dispensing system, generally indicated at <NUM>, according to one embodiment of the present disclosure. The dispensing system <NUM> is used to dispense a viscous material (e.g., an adhesive, encapsulent, epoxy, solder paste, underfill material, etc.) or a semi-viscous material (e.g., soldering flux, etc.) onto an electronic substrate <NUM>, such as a printed circuit board or semiconductor wafer. The dispensing system <NUM> may alternatively be used in other applications, such as for applying automotive gasketing material or in certain medical applications or for applying conductive inks. It should be understood that references to viscous or semi-viscous materials, as used herein, are exemplary and intended to be non-limiting. In one embodiment, the dispensing system <NUM> includes first and second dispensing units, generally indicated at <NUM> and <NUM>, respectively, and a controller <NUM> to control the operation of the dispensing system. It should be understood that dispensing units also may be referred to herein as dispensing pumps and/or dispensing heads. Although two dispensing units are shown, it should be understood that a single dispensing unit or multiple dispensing can be employed.

The dispensing system <NUM> may also include a frame <NUM> having a base or support <NUM> for supporting the electronic substrate <NUM>, a dispensing unit gantry <NUM> movably coupled to the frame <NUM> for supporting and moving the dispensing units <NUM>, <NUM>, and a weight measurement device or weigh scale <NUM> for weighing dispensed quantities of the viscous material, for example, as part of a calibration procedure, and providing weight data to the controller <NUM>. A conveyor system (not shown) or other transfer mechanism, such as a walking beam, may be used in the dispensing system <NUM> to control loading and unloading of electronic substrates to and from the dispensing system. The gantry <NUM> can be moved using motors under the control of the controller <NUM> to position the dispensing units <NUM>, <NUM> at predetermined locations over the electronic substrate. The dispensing system <NUM> may include a display unit <NUM> connected to the controller <NUM> for displaying various information to an operator. There may be an optional second controller for controlling the dispensing units. Also, each dispensing unit <NUM>, <NUM> can be configured with a z-axis sensor to detect a height at which the dispensing unit is disposed above the electronic substrate <NUM> or above a feature mounted on the electronic substrate. The z-axis sensor is coupled to the controller <NUM> to relay information obtained by the sensor to the controller.

Prior to performing a dispensing operation, as described above, the electronic substrate, e.g., the printed circuit board, must be aligned or otherwise in registration with a dispensing unit of the dispensing system. The dispensing system further includes a vision system <NUM>, which, in one embodiment, is coupled to a vision system gantry <NUM> movably coupled to the frame <NUM> for supporting and moving the vision system. In another embodiment, the vision system <NUM> may be provided on the dispensing unit gantry <NUM>. As described, the vision system <NUM> is employed to verify the location of landmarks, known as fiducials, or components on the electronic substrate. Once located, the controller can be programmed to manipulate the movement of one or more of the dispensing units <NUM>, <NUM> to dispense material on the electronic substrate.

Systems and methods of the present disclosure are directed to dispensing material onto an electronic substrate, e.g., a printed circuit board. The description of the systems and methods provided herein reference exemplary electronic substrates <NUM> (e.g., printed circuit boards), which are supported on the support <NUM> of the dispensing system <NUM>. In one embodiment, the dispense operation is controlled by the controller <NUM>, which may include a computer system configured to control material dispensing units. In another embodiment, the controller <NUM> may be manipulated by an operator. The controller <NUM> is configured to manipulate the movement of the vision system gantry <NUM> to move the vision system so as to obtain one or more images of the electronic substrate <NUM>. The controller <NUM> further is configured to manipulate the movement of the dispensing unit gantry <NUM> to move the dispensing units <NUM>, <NUM> to perform dispensing operations.

Embodiments of the present disclosure are directed to a strain wave gear drive assembly that is configured to tilt and rotate a dispensing unit of a dispensing system. offer alternative and competitive means to accurately dispense simultaneously on one or more electronic substrates or two or more patterns associated with a single electronic substrate. The methods disclosed herein further support the use of various types of dispensing units, including, but not limited to, auger, piston and jetting pumps.

Referring to <FIG> and <FIG>, a dispensing system is generally indicated at <NUM>. As shown, the dispensing system <NUM> includes a frame <NUM> configured to support the major sub-assemblies of the dispensing system. The dispensing system <NUM> further includes a gantry system, generally indicated at <NUM>, which is configured to move in x-axis and y-axis directions. The dispensing system <NUM> further includes a dispensing unit assembly, generally indicated at <NUM>, which is supported by the gantry system <NUM>. <FIG> illustrates the dispensing system <NUM> having the dispensing unit assembly <NUM> and <FIG> illustrates the dispensing system <NUM> with the dispensing unit assembly removed. As shown, the dispensing unit assembly includes a single dispensing unit <NUM>. A conveyor system (not shown) may be used in the dispensing system <NUM> to control loading and unloading of substrates, e.g., electronic substrate <NUM>, to and from a support <NUM> of the dispensing system. The gantry system <NUM> can be moved using motors under the control of a controller, in a manner similar to controller <NUM> of dispensing system <NUM>, in the x-axis and y-axis directions to position the dispensing unit assembly <NUM> at predetermined locations over the electronic substrate.

In one embodiment, as shown in <FIG> and <FIG>, the gantry system <NUM> may be configured to include a left-hand side rail <NUM>, a right-hand side rail <NUM>, and a beam <NUM> that extends between the two side rails. The beam <NUM> is configured to move in a y-axis direction along the side rails <NUM>, <NUM> to achieve y-axis movement of the dispensing unit assembly <NUM>. The gantry system <NUM> further includes a carriage <NUM> that is coupled to the beam <NUM> and configured to move along a length of the beam to provide x-axis movement of the dispensing unit assembly <NUM>. Specifically, the carriage <NUM> supports the dispensing unit assembly <NUM>, and is configured to move along the length of the beam in the x-axis direction to move the dispensing unit <NUM> over desired locations of the electronic substrate <NUM> positioned on the support <NUM> of the dispensing system <NUM>. In a certain embodiment, movement of the gantry system <NUM> (i.e., movement of the beam <NUM> and the carriage <NUM>) in the x-y plane may be achieved by employing ball screw mechanisms driven by respective motors as is well known in the art.

In one embodiment, an exemplary dispensing system described herein may embody Camalot® dispensing systems sold by ITWEAE of Hopkinton, Massachusetts.

The dispensing unit assembly <NUM> is configured to move the dispensing unit <NUM> in a z-axis direction by a z-axis drive mechanism <NUM>, which is shown in <FIG>. The amount of z-axis movement may be determined by measuring the distance between the tip of a needle (not shown) of the dispensing unit <NUM> and the electronic substrate <NUM>. When moving, the dispensing unit <NUM> may be positioned at a nominal clearance height above the electronic substrate <NUM>. The clearance height may be maintained at a relatively consistent elevation above the electronic substrate <NUM> when moving from one dispense location to another dispense location. Upon reaching a predetermined dispense location, the z-axis drive mechanism <NUM> lowers the dispensing unit <NUM> to the electronic substrate <NUM> so that dispensing of material on the electronic substrate may be achieved.

Still referring to <FIG> and <FIG>, the dispensing unit <NUM> is moved over the electronic substrate <NUM> in such a manner to perform a dispense operation with the dispensing unit. However, prior to dispensing, the position of the electronic substrate <NUM> with respect to the dispensing unit <NUM> is determined so that accurate dispensing may take place. Specifically, in one embodiment, the carriage <NUM> can be configured to include an optical element or camera that is designed to take an image of the electronic substrate <NUM>. Although the camera is described to be mounted on the carriage <NUM>, it should be understood that the camera may be separately mounted on the beam <NUM> or on an independent gantry. The camera may be referred to herein as a "vision system" or an "imaging system. " To align the electronic substrate <NUM> with the dispensing unit <NUM> and gantry system <NUM>, images of at least two fiducials provided on the electronic substrate <NUM> are taken by the camera. If the electronic substrate <NUM> is out of position, the gantry system <NUM> may be manipulated to account for the actual position of the electronic substrate. In one embodiment, the camera may be calibrated to determine a camera-to-needle offset distance for the dispensing unit <NUM>.

In another embodiment, vision alignment and clearance height sensing can be achieved with a laser or another calibrated distance measurement device.

A dispensing system typically has a dispensing unit oriented vertically and thus perpendicular to a horizontally fixtured substrate. In some applications, it is advantageous to tip the dispensing unit <NUM> away from the vertical to deposit the material being dispensed in a location that would otherwise be inaccessible from the vertical orientation. As the tilted dispensing unit <NUM> is articulated to various desired orientations, it may also be advantageous to change not only the angle of the dispensing unit from the vertical, but also the direction in which the dispensing unit is tilted, perhaps to deposit material at the bottom edge of a part along more than one side.

As will be appreciated by those familiar with moving structures, the mechanisms utilized to tilt and rotate the dispensing unit <NUM> add mass and reduce the structural stiffness, since any added mechanism introduces addition compliance. As the supported mass is increased and the stiffness of the structure is reduced, the natural frequency of the assembly is lowered. Accordingly, it is incumbent upon the designer to provide the necessary degrees of freedom with a minimum of added mass and as stiff as structure as possible. Moreover, given the construction, unwanted vibration is a natural consequence to the mass added with a tilt and rotate design.

Embodiments of the dispensing system <NUM> of the present disclosure accomplish this goal by incorporating a very compact and highly integrated rotary actuator, such as those available from Harmonic Drive of Beverly, Massachusetts, that includes a motor, a strain-wave harmonic reduction gear box and a very stiff rotary cross-roller bearing. The high level of integration in the strain-wave gear-box actuator serves to minimize added mass and compliance. The strain-wave gear-box further has the benefit of extremely low backlash. Also, the integrated motor, bearing and gear-box assembly serves to minimize the number of parts that must be purchased, assembled and tested.

Referring to <FIG>, the dispensing unit assembly <NUM> includes a drive assembly configured to support the dispensing unit <NUM>, which is shown in an operational position in <FIG>. The dispensing unit assembly <NUM> can be removed from the components of the dispensing unit assembly configured to support the dispensing unit. As shown, the dispensing unit assembly <NUM> includes a support bracket <NUM> having an L-shaped construction in which a first portion <NUM> of the support bracket is secured to the z-axis drive mechanism <NUM> of the carriage <NUM> and a second portion <NUM> that extends perpendicularly from the first portion. The dispensing unit assembly <NUM> further includes a movable bracket <NUM> that is rotatably coupled to the support bracket <NUM> at the second portion <NUM> of the support bracket by a first strain wave gear system <NUM>. In the shown embodiment, the movable bracket <NUM> is configured to rotate with respect to the support bracket <NUM> about a generally vertical axis A.

The movable bracket <NUM> includes a second strain wave gear system <NUM> that is configured to support the dispensing unit <NUM>. The second strain wave gear system <NUM> may include a mounting plate that is configured to receive and support the dispensing unit <NUM> when the dispensing unit is in its operational position. The second strain wave gear system <NUM> is configured to rotate and tilt the dispensing unit <NUM> to a desired position during a dispense operation about an axis B, which is generally perpendicular to axis A. In one embodiment, the first strain wave gear system <NUM> is similarly if not identically constructed as the second strain wave gear system <NUM>.

It should be understood that the orientation of the movable bracket <NUM> with respect to the support bracket <NUM> about axis A and the orientation of the dispensing unit <NUM> with respect to the movable bracket can be varied to accommodate a particular application. For example, the movable bracket <NUM> can be rotatably coupled to the support bracket <NUM> about a generally horizontal axis and the dispensing unit can be rotatably coupled to the movable bracket about a generally vertical axis.

Embodiments of the present disclosure are directed to a system and a method of dampening the vibration of a cantilevered load on the gantry driven dispensing unit <NUM>. In some embodiments, loads on the dispensing unit <NUM> may cause sustained vibration which is detrimental to the performance of the dispensing unit. These vibrations can be of large enough magnitude and/or for a duration which will affect the accurate placement of dispensed material and required settle times which in turn negatively affect overall cycle time.

One object of the system and method of the present disclosure is to provide reduce vibration on the dispensing unit <NUM> such that accurate dispense placement is obtained with minimal settling time.

Embodiments of the dampener systems and methods disclosed herein may be used as in multiple application of cantilevered load on the dispensing unit <NUM> of the automated dispensing system <NUM>.

Embodiments of the mass dampener systems and methods disclosed herein provide improved dispense placement accuracy and reduced settle times. Also, such systems and methods allow very close proximity dispensing without reduced chance of touching a component through vibration.

Referring to <FIG>, while there are known methods to address vibration by employing vibration damping and mass dampeners within machinery, with dispensing systems used to dispense viscous material, the application a mass dampener assembly, generally indicated at <NUM>, is provided to reduce the vibration of the dispensing unit <NUM> during operation of the dispensing unit. In one embodiment, the mass dampener assembly <NUM> is mounted to the cantilevered articulating (movable) bracket <NUM>. The mass dampener assembly <NUM> is configured to alleviate dispensed material inaccuracies due to the attached dispensing unit <NUM> by means of the cantilevered mounting system. Although the cantilevered mounting system being used herein may be a source of the unwanted vibration, the provision of the mass dampener system <NUM> is provided in the application in order for other features of the dispensing system <NUM> to work properly.

In the shown embodiment, the mass dampener assembly <NUM> is a tuned mass dampener utilizing a preselected weight, that includes a mass dampener <NUM> that is mounted on top of a threaded elastomer standoff or isolator <NUM>, with one end of the standoff being rigidly mounted to the bottom of the movable bracket <NUM>, and the other end of the standoff supporting the mass dampener. The preselected weight of the mass dampener <NUM> and the threaded elastomer standoff <NUM> can be altered if the frequency of the sinusoidal vibration is changed due to having different loads.

Referring to <FIG>, a mass dampener assembly of another embodiment is generally indicated at <NUM>. As shown, the mass dampener assembly <NUM> includes a generally U-shaped mass dampener <NUM> that is configured to span and be secured to the bottom of the movable bracket <NUM> and a mounting plate <NUM> that is provided to secure the mass dampener to the movable bracket by suitable fasteners. The mass dampener <NUM> includes two side walls <NUM>, <NUM> that are connected to one another with a bottom wall <NUM>. The mass dampener assembly <NUM> further includes a pair of threaded elastomer standoffs, each indicated at <NUM>, to dampen the connection of the mass dampener <NUM> to the bottom of the movable bracket <NUM>. Further provided are two bumpers, each indicated at <NUM>, one for each side wall <NUM>, <NUM> of the mass dampener <NUM>, to dampen the impact of the side walls of the mass dampener with the bottom of the movable bracket <NUM> when moving the dispensing unit <NUM> quickly. The bumpers <NUM> further prevent sound from occurring during movement of the dispensing unit <NUM>.

Referring to <FIG>, the threaded elastomer standoff <NUM> includes a male threaded portion, which is attached to a threaded opening provided in the bottom of the movable bracket <NUM>. The threaded elastomer standoff <NUM> further includes a female threaded portion, which receives a threaded fastener to secure the mounting plate <NUM> and the mass dampener <NUM> to the bottom of the movable bracket <NUM>. The male threaded portion and the female threaded portion are inserts provided in an elastomeric material.

In one embodiment, the mass dampener assembly <NUM> weighs <NUM> pounds (lbs), which is approximately <NUM>% of the weight of a one-pound dispensing unit <NUM> and approximately <NUM>% of the weight of a two-pound dispensing unit. The <NUM> lbs mass dampener assembly <NUM> is approximately <NUM>% of the weight of the cantilevered weight of the movable bracket <NUM>, the dispensing unit <NUM> and associated parts, which can total between <NUM> to <NUM> lbs. In a certain embodiment, the threaded elastomer standoff <NUM> is configured to releasably secure the mass dampener <NUM> to the movable bracket <NUM> of the dispensing unit assembly. The mass dampener <NUM> of the mass dampener assembly <NUM> is configured so that it does not interfere with the movement of the dispensing unit <NUM> during operation.

Claim 1:
A dispensing system for dispensing viscous material on an electronic substrate, the dispensing system comprising:
a frame;
a support coupled to the frame, the support being configured to receive and support an electronic substrate during a dispense operation;
a dispensing unit assembly configured to dispense viscous material; and
a gantry coupled to the frame, the gantry being configured to support the dispensing unit assembly and to move the dispensing unit assembly in x-axis and y-axis directions,
wherein the dispensing unit assembly includes
a support bracket secured to the gantry,
a movable bracket rotatably coupled to the support bracket configured to enable the rotation of the movable bracket with respect to the support bracket about a first axis,
a dispensing unit rotatably coupled to the movable bracket configured to enable the rotation of the dispensing unit with respect to the movable bracket about a second axis generally perpendicular to the first axis, and
a mass dampener assembly coupled to the movable bracket, the mass dampener assembly being configured to reduce vibration of the dispensing unit during operation,
wherein the mass dampener assembly includes a mass dampener coupled to the movable bracket by at least one isolator.