Patent Publication Number: US-2009229118-A1

Title: Electronics Assembly Machine with Wireless Communication Nozzle

Description:
COPYRIGHT RESERVATION 
     A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent files or records, but otherwise reserves all copyright rights whatsoever. 
     BACKGROUND 
     Electronics assembly machines, such as pick and place machines, are generally used to manufacture electronic circuit boards. A blank printed circuit board is usually supplied to the pick and place machine, which then picks electronic components from component feeders, and places such components upon the board. The components are held upon the board temporarily by solder paste or adhesive until a subsequent step in which the solder paste is melted, or the adhesive is fully cured. 
     Pick and place machine operation is challenging. Since machine speed corresponds with throughput, the faster the pick and place machine runs, the less costly the manufactured board. Additionally, placement accuracy is extremely important. Many electrical components, such as chip capacitors and chip resistors are relatively small and must be accurately placed on equally small placement locations. Other components, while larger, have a significant number of leads or conductors that are spaced from one another at a relatively fine pitch. Such components must also be accurately placed to ensure that each lead is placed upon the proper pad. Thus, not only must the machine operate extremely fast, but it must also place components extremely accurately 
     Electronics assembly is a critical process. A typical printed circuit board may contain hundreds of individual electronic components each of which has between two and sometimes many individual contact points. If a single pad of a single component is not properly electrically coupled to its respective pad on the circuit board, operation of the entire assembled device may be frustrated. Accordingly, the electronics assembly industry provides significant resources, both in terms of capital equipment and technician time for the process of inspecting assembled printed circuit boards and/or repairing defective boards. Automated optical inspection machines are available that can visually inspect each and every mounted component to help ensure that the assembly step has been performed correctly for every component on the circuit board prior to the permanent fixation of the components upon the board. Permanent fixation of the components upon the board can be in the form of providing the circuit board to a wave solder machine, reflowing solder paste in an oven or curing uncured conductive adhesive. 
     A vast number of variables can affect placement efficacy. Many variables with the respect to the pick and place machine, itself, can affect the ability of the machine to reliably pick a component from a component feeder, accurately sense a position of a component on a nozzle, move the component to a placement location, correct the orientation of the component prior to placement on the circuit board, and/or place the component upon the circuit board. Variables include vacuum strength, actuation timing, machine wear or inaccuracies in each of x, y, and z directions, accuracy of encoders of the pick and place machine in the x, y, and z direction, deviations from flatness of the printed circuit board, pressure of the nozzle upon the board as the component is placed on the workpiece, as well as many other variables. Further, there are a number of variables that can affect placement efficacy which are not related to the pick and place machine itself. For example, the ability of solder paste and/or uncured adhesive to temporarily adhere a placed component may change with temperature, barometric pressure, or even relative humidity. Moreover, different batches of solder paste may have different viscosities and/or may be deposited by a solder paste printing machine differently. Variability in the application of materials such as solder paste and adhesive paste prior to the placement operation can cause these materials to inadvertently come into contact with the placement head causing the vacuum suction line to clog or to improperly adhere the component to the nozzle. Also, a major cause of pick and place errors is setup error, which occurs when an incorrect feeder, program, nozzle or parameter is inadvertently used by the technician responsible in the setup of the machine. 
     To date, the art has responded to the conflicts between the extreme speed of a pick and place machine and the multiplicity of variables affecting placement efficacy with powerful inspection tools. As set forth above, automated optical inspection machines are typically placed after a pick and place machine in order to optically inspect placed components. More recently, optical inspection hardware and techniques have been migrated to the pick and place machine itself such that the placement of each component can be evaluated immediately after the component is placed. However, given that the pick and place machine head often must move in different directions relatively quickly, any mass added to the pick and place machine head will necessarily increase inertia of the pick and place machine head, which increased inertia may decrease overall throughput of the pick and place machine. In addition, adding sensors to the placement will add to the amount of cabling required to be run to the placement head. Since the cabling to the placement head is required to flex during placement head motion, the reliability of the cabling as well as the extra inertia required to move the cable becomes problematic. 
     Other attempts at improving the placement efficacy have centered on the operation of the nozzle used to perform the pick and place operation. For example, U.S. Pat. Nos. 5,742,396 and 6,393,336 provide an apparatus detecting a clogged nozzle. U.S. Pat. No. 6,100,922 provides a nozzle that is shaped to assist in the illumination of the picked component. U.S. Pat. No. 5,064,235 provides an apparatus that extends the function of the pick and place nozzle to test the conductance of the picked component. 
     Providing the electronics assembly industry with additional data relative to pick and place machine operation, and/or placement efficacy without requiring significant increases in placement head inertia, or significant retrofitting efforts, would represent a significant benefit. 
     SUMMARY 
     A pick and place machine for placing components upon a workpiece includes a placement head, a robotic system and at least one detachable nozzle. The robotic system is configured to generate relative movement between the placement head and the workpiece. The detachable nozzle is coupled to the placement head and includes wireless communication circuitry. A detachable nozzle having wireless communication abilities is also disclosed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic view of a Cartesian pick and place machine with which embodiments of the invention can be practiced. 
         FIG. 2  is a diagrammatic plan view of a turret pick and place machine with which embodiments of the invention can be practiced. 
         FIG. 3  ( 3   a - 3   c ) is a diagrammatic view of a detachable nozzle having wireless communication in accordance with an embodiment of the present invention. 
         FIG. 4  is a diagrammatic view of nozzle identification in accordance with an embodiment of the present invention. 
         FIG. 5  is a diagrammatic view of a nozzle exchange reservoir in accordance with an embodiment of the present invention. 
         FIG. 6  is a diagrammatic view of a power module of a detachable nozzle having wireless communication in accordance with an embodiment of the present invention. 
         FIG. 7  is a diagrammatic view of wireless communication module of a detachable nozzle having wireless communication in accordance with an embodiment of the present invention. 
         FIG. 8  is a diagrammatic view of measurement circuitry of a detachable nozzle having wireless communication in accordance with an embodiment of the present invention. 
         FIG. 9  is a diagrammatic view of a detachable nozzle having wireless communication in accordance with another embodiment of the present invention. 
         FIG. 10  is a diagrammatic view of output circuitry of a detachable nozzle having wireless communication in accordance with an embodiment of the present invention. 
         FIG. 11  is a diagrammatic view of still another detachable nozzle having wireless communication in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
       FIG. 1  is a diagrammatic view of an exemplary Cartesian pick and place machine  201  with which embodiments of the present invention are applicable. Pick and place machine  201  receives a workpiece, such as circuit board  203 , via transport system or conveyor  202 . Placement head  206  then obtains one or more electrical components to be mounted upon circuit board  203  from component feeders (not shown) and moves in x, y and z directions to place the component in the proper orientation at the proper location upon circuit board  203 . Placement head  206  may include multiple nozzles  208 ,  210 ,  212  to pick multiple components. Some pick and place machines may employ a placement head that moves over a stationary camera to image the components) in order to ascertain component location and orientation upon each nozzle. Placement head  206  may also include a downwardly looking camera  209 , which is generally used to locate fiducial marks upon circuit board  203  such that the relative location of placement head  206  with respect to circuit board  203  can be readily calculated. 
       FIG. 2  is a diagrammatic view of an exemplary rotary turret pick and place machine  10  with which embodiments of the present invention are also applicable. Machine  10  includes some components that are similar to machine  201  and like components are numbered similarly. For turret pick and place machine  10 , circuit board  203  is loaded via a conveyor onto an x-y stage (not shown). Attached to main turret  20  are nozzles  210  that are disposed at regular angular intervals around the rotating turret. During each pick and placement cycle, turret  20  indexes an angular distance equal to the angular distance between adjacent placement nozzles  210 . After turret  20  rotates into position and circuit board  203  is positioned by the x-y stage, a placement nozzle  210  obtains a component from a component feeder  14  at a defined pick point  16 . During this is same interval, another nozzle  210  places a component onto circuit board  203  at a preprogrammed placement location  106 . Additionally, while turret  20  pauses for the pick and place operation, upward looking camera  30  acquires and image of another component, which provides alignment information for that component. This alignment information is used by pick and place machine  10  to position circuit board  203  when placement nozzle  210  is positioned several steps later to place the component. After the pick and place cycle is complete, turret  20  indexes to the next angular position and circuit board  203  is repositioned in x-y direction(s) to move the placement location to position which corresponds to the placement location  106 . 
     Embodiments of the present invention generally provide an electronics assembly machine having at least one detachable nozzle that communicates wirelessly. The use of wireless communication facilitates automatic picking of the wireless nozzle from a nozzle exchange reservoir; using the wireless nozzle by virtue of one or more wireless communication signals; and finally replacing the wireless nozzle back into a nozzle exchange reservoir. As used herein, a wireless communication signal includes any signal sent from or to the wireless nozzle without the use of electrical conductors. Examples of wireless communication include radio-frequency (RF) communication, optical communication, and even pneumatic communication. 
     Utilization of detachable nozzles in electronics assembly machines is known. For example, U.S. Pat. Nos. 4,831,721, 5,201,696 and 6,422,489 provide an apparatus for the replacement of vacuum nozzles. While it is preferred that embodiments of the present invention be generally embodied within a detachable nozzle assembly that can be automatically picked from a nozzle exchange reservoir, utilized, and replaced, it is also contemplated that embodiments of the present invention can be practiced with a nozzle that is manually engaged and/or disengaged to a pick and place machine&#39;s placement head. The manner in which the detachable nozzle is coupled to the pick and place machine placement head can also vary. For example, a vacuum, electromagnetism, and/or electromechanical clamping, or any combination thereof can be used to retain the detachable nozzle. 
       FIGS. 3   a  and  3   b  show a diagrammatic view of detachable nozzle  400  in accordance with an embodiment of the present invention. Nozzle  400  includes nozzle body  401  coupled to engagement portion  402 . Engagement portion  402  can take any suitable physical form that can be configured to engage and disengage with a pick and place machine&#39;s placement head. Preferably, portion  402  is configured so that nozzle  400  can be automatically attached and detached to/from a pick and place machine placement head. The vacuum used to pick up the component is supplied by the pick and place head  206  and is transferred to the tip of the nozzle  405  through an opening  407  that runs the length of nozzle  405 . Also, extending from nozzle body  401  is an electronics housing  403  that is configured to be the same shape as a passive reflector found on current state of the art pick and place nozzles to provide background illumination for upward looking alignment cameras. 
       FIG. 3   c  shows the internal configuration of electronics housing  403 . The nozzle electronics housing  403  contains identification module  404 , power module  406 , communication module  408 , controller  410  and input circuitry  412  mounted on a printed circuit board (PCB)  413 . Through PCE  413 , the power module  406  is operably coupled to communication circuitry  408 , controller  410 , and input circuitry  412 . Additionally, controller  410  is coupled to communication module  408  and input circuitry  412 . 
     Controller  410  preferably includes a microprocessor and that is configured to execute a plurality of instructions stored in memory disposed within controller  410  or coupled thereto. Additionally, memory can be used to store information related to one or more input signals obtained by nozzle  400 . In this manner, nozzle  400  is able to store information related to its operation within a pick and place machine. 
       FIG. 4  is a diagrammatic view of identification  404  in greater detail. Specifically, identification  404  is disposed within, or coupled to, nozzle body  401  can include any suitable identification that identifies individual nozzle  400 , the capabilities and/or requirements of nozzle  400 , or any other suitable information relative to nozzle  400 . The physical form in which identification  404  is embodied can vary as well. For example, identification  404  can simply take the form of written indicia. Additionally, and preferably, identification  404  is machine readable identification. For example, machine readable identification can include barcode information  414 , and/or radio frequency identification (RFID) information  416 . RFID tags are a known technology with which information between a non-powered RFID tag and an RFID reader can be exchanged when the reader is brought into relatively close proximity to the RFID tag. Thus, it is contemplated that an RFID reader and/or barcode reader be provided with, or integrated with a placement head of a pick and place machine such that the pick and place machine can learn information about nozzle  400  simply by brining the placement head into the proximity of nozzle  400 . Thus, as will be described in greater detail below, individual detachable nozzles can be tailored to specific functions and their identification  404  can provide an indication of their individual requirements and/or abilities. 
       FIG. 5  is a diagrammatic view of nozzle exchange reservoir  470 . The nozzle exchange reservoir is typically located within the pick and place machine  201  within the motion envelope of the pick and place head  206 . The nozzle exchange reservoir  470  typically has several nozzle locating features  472  that hold the nozzles  400  in a known position and orientation. An operator will place the nozzles  400  into these locating features  472  prior to the pick and place operation. During operation, the pick and place head is moved into position over a nozzle  400  and lowered to engage a nozzle  470  for use. Nozzles  470  are exchanged whenever a different size or style of component requires placing, or if the nozzle is damaged or otherwise not functioning properly. 
     In a preferred embodiment of the present invention, electrical contacts  474  are placed in the vicinity of the nozzle locating features  472  so that when a nozzle  470  is placed in the locating feature  472 , the electrical contacts  474  engage with contacts (not shown in  FIG. 5 ) on the electronics housing  403  to provide power to recharge the power source  406 . 
       FIG. 6  is a diagrammatic view of power module  406  in accordance with an embodiment of the present invention. Preferably, module  406  includes battery  418 . More preferably, battery  418  is a rechargeable battery. In this manner, battery  418  can be recharged using electrical contacts  474  whenever nozzle  400  is maintained within its respective nozzle position in the nozzle exchange reservoir  470 . However, embodiments of the present invention can be practiced with non-rechargeable batteries. Power module  406  may also contain photovoltaic cell  420  which, in accordance with known techniques, can generate electricity from electromagnetic illumination. Thus, an illuminator of the pick and place machine can provide additional energy for operation of nozzle  400 . Further still, power module  406  may also, or in the alternative, contain vacuum module  422  that is configured to generate electricity based upon airflow through nozzle  400  in response to vacuum generated by the pick and place machine. Further still other energy storage and/or generation sources can be used within power module  406 , as appropriate. Power module  406  can also include suitable electronic circuitry to condition, regulate, or otherwise adapt electrical power for utilization by other electrical components. 
       FIG. 7  is a diagrammatic view of wireless communication module  408  in accordance with an embodiment of the present invention.  FIG. 7  illustrates that wireless communication module  408  can include one or more different types of wireless communication. For example, wireless communication can include radio-frequency communication  424 . RF communication  424  can be in accordance with any suitable standard including the known Bluetooth standard, the Wireless Fidelity (WiFi) communication standard such as IEEE 802.11b or IEEE 802.11g, or any other later-developed WiFi technologies, such as the smart RFID technologies. Certainly, custom RF communication can be used as well. Custom RF communication can include the utilization of any appropriate frequency, and/or information encoding regimes. 
     Wireless communication module  408  can, in addition or in the alternative, use optical communication techniques. Such optical communication techniques can include the utilization of infrared (IR) communication which is common in devices such as laptop computers and handheld computers. 
       FIG. 8  is a diagrammatic view of input circuitry  412  in accordance with an embodiment of the present invention. Input circuitry  412  can be configured to transducer or otherwise obtain, information relative to any suitable condition, characteristic or parameter of interest within or related to pick and place machine operation. Such parameters can include variables  429  relative to the pick and place machine itself. Such parameters can include information relative to the strength, and clarity of the vacuum  430  required to hold a component on the nozzle. Additionally, machine variables  429  include measurement of acceleration  432  in any suitable direction, such as the x, y, and/or z axis or rotation about the axis of the nozzle. Another important machine variable  429  includes the speed  434  with which the placement head moves. Additionally, yet another machine variable  429  is the positioning  436  of the placement head within the pick and place machine. Another machine variable  429  is any vibration  438  present within the pick and place machine. The utilization of one or more sensors to detect such machine variables  429  allow for the pick and place machine to perform a variety of self diagnostics, and/or determine causes of problems. For example, if a number of defects are produced, the pick and place machine can automatically select a replaceable nozzle  400  having a sensor adapted to sense position  436 . This position sensor can be used to independently verify the position of the placement head to determine if the encoders of the pick and place machine are accurately reporting position of the placement head. 
     Input circuitry  412  can also include components that are configured to measure environmental variables  450  within or proximate the pick and place machine. Such environmental variables include temperature  452 , pressure  454  (such as barometric pressure), humidity  456 , electromagnetic interference (EMI)  458 , electromagnetic charge (EMC) and/or the presence and quantification of particulates  460 . 
     Input circuitry  412  can also include circuits or modules to test or otherwise inspect components placed by the pick and place machine. Such component testing/inspection  440  can include identification  442  of the components. Such identification can be in the form of optical character recognition (OCR) of indicia on the surface of the components by virtue of an image of the component acquired by nozzle  400 . Additionally, component testing/inspection  440  can include actual electrical testing  444  of the component. Such electrical testing can include the application of a test voltage or current to two or more test pads of the component, or circuit board, in order to determine whether the component, or circuit board, responds appropriately. Further still, component testing/inspection  440  can include placement inspection  446 . Placement inspection  446  can be in the form of a small video camera retained within housing  401  coupled to input circuitry  412 . Images of the component acquired by the video camera can be compared with known good placement images to determine whether the placement of the component under test is correct. Certainly, other image processing techniques or inspection regimes can also be used. Input circuitry  412  can also includes circuits or modules to facilitate testing  448  of the circuit board itself. 
       FIG. 9  is a diagrammatic view of another detachable nozzle with wireless communication abilities in accordance with another embodiment of the present invention. Nozzle  480  bears many similarities to nozzle  400  and like components are numbered similarly. The primary difference between nozzle  480  and nozzle  400  is that nozzle  480  includes output circuitry  482  instead of the input circuitry  412  of nozzle  400 . 
       FIG. 10  is a diagrammatic view of output circuitry  482  in accordance with an embodiment of the present invention. Output circuitry  482  can be configured to deliver any suitable physical interaction to a component or workpiece of the pick and place machine. Such physical interaction can include illumination  484 , which illumination  484  can include visible illumination  486 , x-ray illumination  488 , and/or infrared (IR) illumination  490 . Additionally, physical interaction can include mechanical interaction  496 . Such mechanical interaction  496  can include the delivery of a suitable fluid to the component or circuit board. One example of a suitable fluid may simply be a blast of air to dislodge or otherwise remove debris. Yet another form of mechanical interaction  496  includes component removal  500 . Component removal  500  can include the utilization of high vacuum, and/or mechanical clamping to physically adhere to and lift a component from the circuit board before the solder or adhesive is melted/cured. Still another form of mechanical interaction is the control of the vacuum pressure that is used to pick up the component. As the speed of the pick and place operation increases, it is advantageous to turn the vacuum on and off close to the tip of the nozzle so that the component can be released from the nozzle quickly. Still another form of mechanical interaction  496  includes the selective or isolated curing  502  of solder or adhesive. Yet another form of mechanical interaction  496  is the marking  504  of a component. Marking  504  can simply take the form of the marking of a component that has a failed a particular inspection and should be addressed later in the assembly process by a rework technician. Other forms of marking can include the utilization of inkjet technology to deliver indicia to an exposed surface of the component or circuit board to provide information relative to the electronics assembly operation and/or the component itself. Mechanical interaction  496  can also include deposition  506  of solder paste or adhesive. Thus, in the example given above where a defective component is removed from a circuit board, new or replacement solder paste can be automatically delivered to the location of the removed component to prepare that location for the arrival for a replacement component. As can be appreciated, output module  482  can certainty include other forms of outputs that can direct a physical interaction upon the component, or circuit board. 
       FIG. 11  is a diagrammatic view of yet another detachable nozzle having wireless communication in accordance with an embodiment of the present invention. Nozzle  510  illustrates that embodiments of the present invention can include both input circuitry  412  as well as output circuitry  482 . While it is preferred that embodiments of the present invention generally communicate wirelessly with the pick and place machine, or other suitable external devices, it is also expressly contemplated that at least some of the inputs or sensing performed by the detachable nozzles can be stored in memory  411 , which stored information can later by uploaded from the detachable nozzle when the detachable nozzle is replaced in its storage rack or bin. Accordingly, the physical cooperation between the detachable nozzles in accordance with embodiments of the present invention and their respective charging/retaining cradles not only can provide power to recharge the nozzles, but also communication channels to retrieve the stored data. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.