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 pump is mounted to a moving assembly or gantry for moving the dispensing pump 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 pump is moved along the co-planar horizontal X axis and Y axis directions until the dispensing pump is located over the desired location. The dispensing pump is then lowered along the perpendicularly oriented vertical Z axis direction until a nozzle/needle of the dispensing pump and dispensing system is at an appropriate dispensing height over the substrate. The dispensing pump 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 pump is typically controlled to dispense lines of material as the dispensing pump is moved in the X and Y axes along the desired path of the lines. For some types of dispensing pumps, such as jetting pumps, the Z axis movement prior to and subsequent to a dispense operation may not be required.

The production rate of such dispensing systems, in some cases, may be limited by the rate at which a particular dispensing pump can accurately and controllably dispense dots or lines of material. In other cases, the production rate of such systems may be limited by the rate at which parts can be loaded into and out of the machine. In still other cases, the production rate of such systems may be limited by process requirements, such as the time required to heat a substrate to a particular temperature, or the time required for a dispensed material to flow, as in underfill applications.

During the manufacture of electronic circuit assemblies, sometimes referred to as printed circuit board assemblies, production requirements often exceed the throughput capabilities of a single dispensing system. To overcome the throughput limitations of a single dispensing system, various strategies are applied to improve the production process, often by enabling multiple operations to be performed in parallel. For example, <CIT>, <CIT>,<CIT> and <CIT>, are each directed to systems and or methods for simultaneously dispensing material with a dispensing system having multiple dispensing units. The systems and methods disclosed in these patents teach adjusting a spacing between adjacent dispensing units by using an adjustable bracket or by controlling the relative X-Y position of one dispensing pump relative to another either prior to or during dispensing operations. Such systems are versatile and can be well suited to a variety of dispensing applications. However, the mechanical and electrical complexities of such systems may be impractical or costly when applied to three or more dispensing pumps.

<CIT> discloses an example of a method and system for dispensing a substance onto a substrate. <CIT> relates to a paste dispenser and method of controlling the same. <CIT> relates to a paste applying apparatus. <CIT> relates to a dual applicator fluid dispensing methods and systems.

In the production of electronic assemblies for markets such as high-volume consumer goods, electronic circuit boards are often fabricated with multiple instances of a particular circuit present on one circuit board. A single printed circuit panel might, for example, have four identical circuit patterns displaced at uniform intervals. The repeating pattern of multiple circuits lends itself well to simultaneous dispensing on two or more circuits at once. Depending on the distance between patterns, it may be impractical to place two dispensing pumps close enough to dispense on adjacent circuits, such as dispensing first on circuits #<NUM> & #<NUM>, then #<NUM> & #<NUM>. However, the same advantage can be realized by dispensing first on #<NUM> & #<NUM>, then on #<NUM> & #<NUM>. It will be observed, however, that any rotation of the substrate in the X-Y plane will result in a change in the relative X-Y location of the two patterns being dispensed. As such, the relative spacing between the two (or more) dispensing pumps must be adjusted to match the spacing of the substrate if two or more patterns are to be dispensed simultaneously and accurately. Alternatively, the substrate can be rotated to match the array of dispensing pumps.

It is a goal of the present disclosure to facilitate the parallel dispensing operations of multiple dispensing pumps in a scalable and practical manner.

The invention is defined by a method of dispensing material using a dispensing system in accordance with claim <NUM>, and by a dispensing system in accordance with claim <NUM>.

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 multiple dispensing pumps that are configured to simultaneously dispense on multiple electronic substrates.

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.

<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. The dispensing system <NUM> includes an array of dispensing units, for example, 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 the array of dispensing units can include more than two dispensing units shown and described throughout the disclosure.

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 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 pumps, including, but not limited to, auger, piston and jetting pumps.

In one embodiment, an array of two or more dispensing pumps is mounted to a common bracket or support assembly to form an assembled array of dispensing pumps, hereinafter referred to as a dispensing pump array or a pump array. The relative spacing between individual dispensing pumps of the dispensing pump array is adjusted, either manually or automatically, to match the relative spacing between the substrate patterns to be dispensed upon. The dispensing pump array is attached to a mechanism that is capable of rotating the dispensing pump array in the X-Y plane relative to the X-Y axes of the positioning system. The dispensing pump array may or may not be positioned vertically by a Z axis, which in turn is positioned in an X axis and Y axis position relative to one or more electronic substrates by a gantry drive system.

Systems constructed and arranged in accordance with embodiments of the present disclosure may be configured to use two or more theta-driven pump arrays on a common gantry drive system. When two pump arrays are used on one dispense system, an X-Y adjustment mechanism may be used to adjust the relative spacing between the two pump arrays. If more than two pump arrays are utilized on one system, then multiple X-Y adjustment mechanisms may be used to adjust the relative spacing between the pump arrays.

Prior to production operation of a dispensing system, certain setup steps should be performed. For example, referring to <FIG>, a dispensing pump array, generally indicated at <NUM>, is shown to have two dispensing pumps, indicated at <NUM> and <NUM>. Also an electronic substrate, generally indicated at <NUM>, includes four identical patterns 48A ("Pattern <NUM>"), 48B ("Pattern <NUM>"), 48C ("Pattern <NUM>") and 48D ("Pattern <NUM>"), each pattern having a known point A and a known point B. The electronic substrate <NUM> further includes a first fiducial mark F1, a second fiducial mark F2 and a third fiducial mark F3. A method of performing simultaneous dispensing on the electronic substrate <NUM> includes determining a spacing interval or pitch between each of the four patterns 48A, 48B, 48C and 48D. This pitch may be measured from a sample electronic substrate, or the data may be known from design data.

For example, in the shown embodiment, the pitch can be measured from the known points A, B on the patterns 48A, 48B, 48C and 48D of the electronic substrate <NUM>. Specifically, the pitch can be measured between the known points A-A or the known points B-B between adjacent patterns on the substrate <NUM>, e.g., between patterns 48A and 48B. The latter of these two methods of determining pitch is often preferable, as the design data may be more accurate than measurements taken from the particular electronic substrate that may have its own particular variations from an ideal or perfect electronic substrate. Once the pattern pitch is known, a spacing S between the dispensing pumps <NUM>, <NUM> of the dispensing pump array <NUM> is adjusted accordingly to achieve a predetermined distance. In this example, the dispensing pump spacing S has been adjusted to twice the pattern pitch.

This arrangement may be more practical to attain than setting the dispensing pump spacing S to one pattern pitch interval, particularly if the pattern pitch is close to or less than a width of a dispensing pump. The process of adjusting the pump-to-pump spacing S may be accomplished either manually or automatically, and may include calibration of the actual dispense position of each dispensing pump <NUM>, <NUM> relative to a machine vision system, such as vision system <NUM>, sometime referred to as "teaching a camera-to-nozzle offset.

Additional setup steps include creating a program or process recipe that specifies the amount and location of material to be dispensed on each pattern 48A, 48B, 48C and 48D of the electronic substrate <NUM>. The information for generating this process recipe may be determined from design data or it may be "taught" from a particular electronic substrate. The process recipe further may include instructions for alignment sensing and calibration (e.g., when and where to perform "Z-sense" calibration of the surface height), weight calibration (e.g., how and when to monitor and calibrate the output of the dispensing pump), temperature control (e.g., wait until the electronic substrate has been in the heat zone for <NUM> seconds before commencing dispensing), timing of the dispense operations (e.g., wait <NUM> seconds after this deposit before doing that deposit), etc..

Once the machine (dispensing system) and program setup steps are complete, production operation of the machine may commence as follows. An electronic substrate is loaded into position in the dispense system. Typical mechanisms for loading electronic substrates include, but are not limited to, conveyor systems that may use one or more conveyor lanes.

Referring now to <FIG>, a machine vision system, e.g., vision system <NUM> shown in <FIG>, is used to locate the electronic substrate <NUM>, typically accomplished by capturing images of alignment features, such as the fiducial marks F1, F2 and F3, and then analyzing the images to determine the position (in X-Y and theta) of the electronic substrate. Once the rotational angle of the electronic substrate <NUM> is calculated, the dispensing pump array <NUM> is then rotated in theta to match the angle of the electronic substrate. In other words the alignment of the first dispensing pump <NUM> and the second dispensing pump <NUM> of the dispensing pump array <NUM> is aligned or parallel to the alignment of the patterns 48A, 48B, 48C and 48D of the electronic substrate <NUM>. In prior systems, such as the system disclosed in <CIT>, the adjustment of second dispensing pump <NUM> relative to the first dispensing pump <NUM> is accomplished with an X-Y adjustment mechanism. This approach works well for a system having of two dispensing pumps.

Specifically, in one embodiment, the dispensing unit gantry <NUM> may be configured to include a beam that extends between two side rails. The beam is configured to move in a Y axis direction along the side rails to achieve Y axis movement of the dispensing pump array <NUM>. X axis movement of the dispensing pump array <NUM> is achieved by a carriage device mounted on the beam. Specifically, the carriage device supports the dispensing pump array <NUM> and is configured to move along a width of the beam in the X axis direction to move the dispensing units over desired locations of the substrate <NUM> positioned on the base <NUM> of the dispenser <NUM>. In a certain embodiment, movement of the dispensing unit gantry <NUM> (i.e., movement of the beam and the carriage device) in the X-Y plane may be achieved by employing ball screw mechanisms driven by respective motors or other linear motion drive components as is well known in the art.

The dispensing pump <NUM> and the dispensing pump <NUM> are coupled to the carriage device by a linear bearing secured to the carriage device. In one embodiment, the dispensing pump <NUM> is fixedly secured to the linear bearing and the dispensing pump <NUM> is coupled to the linear bearing by an automatic adjustment mechanism. It should be understood that the dispensing pump <NUM> may be fixed to the linear bearing and the dispensing pump <NUM> may be coupled to the automatic adjustment mechanism, or both dispensing pumps <NUM>, <NUM> may be coupled to the automatic adjustment mechanism, and fall within the scope of the present disclosure. In a certain embodiment, the dispensing pump <NUM> and the dispensing pump <NUM> can be offset from one another a distance, with the automatic adjustment mechanism being configured to adjust the distance by moving the second dispensing unit a relatively small distance in the X axis and Y axis directions. In another embodiment, the mounting assemblies associated with the dispensing pumps <NUM>, <NUM> are each configured to enable Z axis movement of the dispensing pumps.

Once configured, the controller of the dispensing system (e.g., controller <NUM> of dispensing system <NUM>) is configured to perform a simultaneous dispense operation on at least two identical patterns of the electronic substrate <NUM> with the dispensing pumps <NUM>, <NUM> of the dispensing pump array <NUM>. Specifically, with reference to the arrangement shown in <FIG>, the dispensing pump array <NUM> is moved to position the first dispensing pump <NUM> over the first location A of pattern 48A and to position the second dispensing pump <NUM> over the first location A of pattern 48C. During a dispense operation, the dispensing pump array <NUM> is moved to simultaneously position the first dispensing pump <NUM> over the second location B of pattern 48A and the second dispensing pump <NUM> over the second location B of pattern 48C, and material is dispensed from the first and second dispensing pumps of the dispensing pump array onto patterns 48A, 48C of the electronic substrate. In some embodiments, during dispensing, the first dispensing pump <NUM> is lowered toward the pattern 48A and the second dispensing pump <NUM> is lowered toward the pattern 48C. The lowering of the first dispensing pump <NUM> and the second dispensing pump <NUM> of the dispensing pump array <NUM> can occur simultaneously.

Similarly, to dispense on pattern 48B and pattern 48D of the electronic substrate <NUM>, the dispensing pump array <NUM> is moved to position the first dispensing pump <NUM> over the first location A of pattern 48B and to position the second dispensing pump <NUM> over the first location A of pattern 48D. During a dispense operation, the dispensing pump array <NUM> is moved to simultaneously position the first dispensing pump <NUM> over the second location B of pattern 48B and the second dispensing pump <NUM> over the second location B of pattern 48D, and material is dispensed from the first and second dispensing pumps of the dispensing pump array onto patterns 48B, 48D of the electronic substrate.

In the present disclosure, the dispensing pumps <NUM>, <NUM> of the dispensing pump array <NUM> are aligned to the electronic substrate <NUM> with a single rotational degree of freedom. Referring to <FIG>, for dispensing systems in which multiple electronic substrates <NUM> and multiple pump arrays <NUM> are utilized, the same alignment process is used to align each of the pump arrays with each of the corresponding electronic substrates. Where multiple pump arrays <NUM> are used, each may be rotated at different angles to one another to match the target electronic substrates 46A, 46B, as the electronic substrates could also be orientated at different angles when positioned in the electronic substrate support system. In the case of multiple dispensing pump arrays <NUM> thus aligned to electronic substrates at different angles, the X-Y adjustment mechanism may be used to dynamically adjust the relative spacing between the dispensing pump arrays during the various dispense operations, as the relative spacing between corresponding features on each of the multiple electronic substrates <NUM> will vary depending on the locations of the features within the electronic substrate.

As clearly shown in <FIG>, the dispense paths from A to B on a first electronic substrate 46A are not parallel to the corresponding dispense paths from A to B on a second electronic substrate 46B. The divergence between these two paths dictates that a distance between the two dispensing pump arrays 40A, 40B must be adjusted during the dispense move to ensure that each dispensing pump array remains properly aligned with the desired path on the electronic substrates 46A, 46B.

It should be noted that while rotation angles as shown have been greatly exaggerated for the purposes of clarity, even very small rotation angles on the order of a milliradian (Mrad) or less can result in lateral offsets which left uncorrected, can be detrimental to the dispensing process.

In one embodiment of the present disclosure, a substrate conveyor is configured to load a substrate carrier containing two or more electronic substrates. The two or more electronic substrates may each be at their own angles of rotation, for which separate angular alignment may be required.

In another embodiment of the present disclosure, a substrate conveyor loads and unloads electronic substrates to and from two or more distinct dispense locations. For example, a first electronic substrate is loaded to a first dispense location, and a second electronic substrate is loaded to a second dispense location. The machine vision system is then used to locate each of the two electronic substrates for subsequent dispensing.

In an alternate embodiment of the present disclosure, an electronic substrate may be rotated to be in alignment with the dispensing pump array <NUM>. A significant advantage of this approach is that the theta adjustment mechanism does not need to be carried about by the X-Y motion system as part of the moving payload. Specifically, the base <NUM> of the dispenser <NUM> can be manipulated to position the electronic substrate <NUM> instead of adjusting the positions of the dispensing pumps <NUM>, <NUM> of the dispensing pump array <NUM>. The dispensing pumps <NUM>, <NUM> can be fixed with respect to one another, and the base <NUM> of the dispenser <NUM> can be configured to move in the X axis and the Y axis directions to rotate and otherwise position the base in a desired position prior to performing a dispensing operation with the dispensing pump array <NUM>. One such mechanism for adjusting a substrate support can be found in <CIT>.

Specifically, in one embodiment, the base <NUM> includes the table, which functions with a support to support the electronic substrate <NUM> in a dispense position. The table is configured to move so as to align the electronic substrate <NUM> disposed on the support with the dispensing pump array <NUM> by the vision system <NUM>. In one embodiment, the table includes four ball bearings that are adapted to ride on top of machined surfaces provided on top of the frame <NUM> of the dispenser <NUM>. The dispenser <NUM> includes three movement mechanisms to move the table so that the electronic substrates <NUM> are moved into alignment. The movement mechanisms can be identical in construction, in which the first and third movement mechanisms are configured to move the table in the Y axis direction and the second movement mechanism is configured to move the table in the Y axis direction. The first and third movement mechanisms can be spaced apart from one another with the second movement mechanism disposed in between in a direction transverse to the direction of the first and third mechanisms. The arrangement is such that the movement of the table of the base <NUM> in the X axis and Y axis directions, as well as the rotation of the table, is achieved under the control of the controller <NUM> by manipulating the movement mechanisms to rotate the base to a desired position.

In another alternate embodiment of the present disclosure, two or more electronic substrates may be independently rotated to be in alignment with the dispensing pump arrays.

Claim 1:
A method of dispensing material using a dispensing system comprising:
a frame and a support coupled to the frame;
a dispensing pump array (<NUM>) including a first dispensing pump (<NUM>) and a second dispensing pump (<NUM>) mounted to a common bracket, the second dispensing pump (<NUM>) being spaced from the first dispensing pump (<NUM>) a predetermined distance;
a gantry (<NUM>) coupled to the frame, the gantry (<NUM>) being configured to move the dispensing pump array (<NUM>) in X axis and Y axis directions, and to rotate the dispensing pump array (<NUM>);
the method comprising the step of:
delivering an electronic substrate (<NUM>) to a dispense position, the electronic substrate having at least two identical patterns (48A, 48B) and at least two fiducial marks (F1, F2);
the method characterized by the steps of:
capturing at least one image of the at least two fiducial marks (F1, F2) provided on the electronic substrate (<NUM>);
analyzing the at least one image to determine a position of the electronic substrate (<NUM>) in X axis, Y axis and theta directions;
calculating a rotational angle of the electronic substrate (<NUM>);
rotating a dispensing pump array (<NUM>) to match the rotational angle of the electronic substrate; and
performing a simultaneous dispense operation on the at least two identical patterns (48A, 48B) with the dispensing pump array,
wherein rotating the dispensing pump array (40A) includes adjusting the second dispensing pump (<NUM>) relative to the first dispensing pump (<NUM>) with a mechanism that is capable of rotating the dispensing pump array (<NUM>) in the X-Y plane relative to the X-Y axes of the gantry (<NUM>);
and wherein performing a simultaneous operation on the at least two identical patterns (48A, 48B) comprise simultaneously dispensing material from the first and second dispensing pumps (<NUM>, <NUM>) on respective first locations of a first pattern (48A) and a second pattern (48B) of the at least two identical patterns.