Abstract:
A component pick and place head includes a frame; a pick-up head mounted on the frame; the pick-up head being movable from a first position in which a component is picked-up by the pick-up head to a second position in which a position of the component that has been picked up by the pick-up head is ascertained; the pick-up head being actuatable from a retracted configuration to an extended configuration for picking up the component; a first actuator for actuating the pick-up head at the first position from the retracted configuration to the extended configuration; and a second actuator at the second position for actuating the pick-up head at the second position from the retracted configuration to the extended configuration.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a method and apparatus for ensuring proper positioning of an electronic component in a system for mounting the electronic component on a circuit board.  
           [0003]    2.Description of Related Art  
           [0004]    In the description of the background of the present invention that follows reference is made to certain structures and methods, however, such references should not necessarily be construed as an admission that these structures and methods qualify as prior art under the applicable statutory provisions. Applicants reserve the right to demonstrate that any of the referenced subject matter does not constitute prior art with regard to the present invention.  
           [0005]    As used herein, the term “component position correcting” refers to correcting both the angular orientation of a component as well as the X-Y positioning of the component. Of course, in some cases only one of the angular orientation of the component or the X-Y positioning of the component will require adjustment.  
           [0006]    Many types of equipment exist today for mounting electronic components on a circuit board, such as a printed circuit board. One such type of equipment includes a pick and place head that has one or more pick-up heads mounted thereon. Each pick-up head includes a spindle. At one end of the spindle is located a device for picking up the component. Such pick-up devices might include a vacuum nozzle or some other type of mechanical grabbing system. At the other end of the spindle is some type of actuating mechanism. The actuating mechanism moves the spindle from a retracted position to an extended position. In operation, the pick-up head is moved to a pick-up position above the component to be picked-up. When the pick-up head is in the pick-up position, the actuating mechanism is actuated so as to extend the spindle so that the pick-up device contacts and grabs the component. The actuating mechanism then moves the spindle to its retracted position so that the selected component may be withdrawn from the surface on which it rests. After the spindle is retracted, the pick-up head can be moved to another location so that the component can be placed at its intended location.  
           [0007]    Due to the increased miniaturization of the components, and the miniaturization of the contact points on each component, it is important to ensure that the component is properly positioned before it is deposited at its intended location. Accordingly, at some point between the pick-up and the depositing of the component, the pick-up head must interact with a positioning system to ensure the proper positioning of the component.  
           [0008]    In the past, such positioning may have been accomplished with a mechanical process in which the component was literally moved with respect to the pick-up head so that the component is properly positioned with respect to the pick-up head. More recently, the positioning is effected with a visual inspection system. Specifically, at some point after the component has been picked up by the pick-up head, the spindle is moved to a location adjacent a camera or imaging system. If it is determined that the component is angularly misaligned with respect to its intended placement, a system may be used to rotate the spindle to ensure proper angular orientation of the component.  
           [0009]    On the other hand, if it is determined that the component is misaligned on the pick-up head with respect to X, Y positioning, the extent of misalignment is noted, and the pick-up head is moved accordingly when delivering the component to the intended location. Specifically, a control system notes the exact location of the component with respect to the pick-up head, and uses this information to properly place the component at the intended location.  
           [0010]    After the component is grabbed by the pick-up head, the spindle is retracted so that the pick-up head can be moved without contacting other components. Some prior art systems, particularly those which include the vision system camera on the pick and place head, have performed the positioning analysis when the spindle is in a retracted position. However, when the component is deposited at the intended location, the spindle is extended. An inherent feature of the spindle assemblies is that when the spindle moves from the retracted position to the extended position, some shifting of the spindle and/or pick-up nozzle may occur. In other words, it is difficult to make a spindle assembly that is so precise in operation that there is no change in position of the pick-up nozzle as the spindle moves from the retracted position to the extended position, and vice versa.  
           [0011]    Thus, in the above-mentioned prior art systems, even if the positioning of the component is exactly accomplished, as the spindle moves from the retracted position to the extended position, some shifting of the component may occur due to errors in the spindle movement. Because the positioning was effected when the spindle was in the retracted position, the changes in positioning of the component as the spindle moves from the retracted position to the extended position cannot be easily anticipated or compensated. Accordingly, such systems may result in inexact placement of the component, even though precise positioning was initially performed.  
           [0012]    Some systems utilize a preprocessing analysis to calibrate the spindles. In such a system, the pick-up head is run through a complete cycle, wherein a vision system monitors each spindle as it moves from a retracted position to an extended position. The vision system monitors the extent of wobble or misalignment that occurs with regard to each spindle as it moves from the retracted position to an extended position, and records this information. Then, during routine processing, the recorded information concerning the wobble or misalignment of the spindle, is used to adjust each spindle during processing to minimize the extent of misalignment as the spindle moves from the retracted position to an extended position.  
           [0013]    However, such a system may not provide enough precision or accuracy for modem needs. Accordingly, a more precise system is necessary if higher levels of precision are desired.  
         OBJECTS AND SUMMARY  
         [0014]    It is an object of the present invention to provide a system that is fast and efficient for positioning each component as it is deposited at its intended location.  
           [0015]    It is also an object of the present invention to provide a system that is able to properly position a component with respect to its intended location, while taking into account any eccentricity or irregularities caused by movement of the spindle as the spindle moves from its retracted position to its extended position.  
           [0016]    According to the present invention, one embodiment of a component pick and place head includes a frame; a pick-up head mounted on the frame; the pick-up head being movable from a first position in which a component is picked-up by the pick-up head to a second position in which a position of the component that has been picked up by the pick-up head is ascertained; the pick-up head being actuatable from a retracted configuration to an extended configuration for picking up the component; a first actuator for actuating the pick-up head at the first position from the retracted configuration to the extended configuration; and a second actuator at the second position for actuating the pick-up head at the second position from the retracted configuration to the extended configuration.  
           [0017]    According to the present invention, another embodiment of a component pick and place head includes a plurality of nozzles actuatable between a retracted configuration and an extended configuration; and a cam surface adjacent a travel path of the plurality of nozzles and adjacent a camera of a vision system; the cam surface arranged so as to actuate each of the plurality of nozzles to the extended configuration as the each of the plurality of nozzles is adjacent the camera of the vision system.  
           [0018]    According to the present invention, a method of picking and placing a component includes the steps of extending a spindle on a pick-up head from a retracted position to an extended position; picking up a component with the spindle while the spindle is in the extended position; retracting the spindle to the retracted position; moving the pick-up head with the component on it to a component position ascertation position; extending the spindle to the extended position; ascertaining a position of the component at the component position ascertation position while the pick-up head and the component are at the component position ascertation position; and depositing the component at a component deposition position. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    [0019]FIG. 1 is a front elevational schematic view of a pick and place head according to the present invention.  
         [0020]    [0020]FIG. 2 is a side elevational view of a pick-up head according to the present invention.  
         [0021]    [0021]FIG. 3 is sectional view of the pick-up head and a portion of an activating mechanism according to the present invention.  
         [0022]    [0022]FIG. 4 is a front elevational view of a cam according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]    In the electronics industry, robotic systems are used to pick up a component from one location and deliver the component with a high degree of accuracy to an intended location so that the component can be soldered or otherwise attached to a circuit board, such as a printed circuit board. Such systems are sometimes referred to as pick and place machines.  
         [0024]    In a pick and place machine, a pick and place head may include a plurality of pick-up heads, each of which are used to pick up one or more of the components for delivery to the intended location. FIG. 1 is a schematic view of a pick and place head  10  according to the present invention, on which is mounted a plurality of pick-up heads  16 , only one of which is actually shown in the drawing.  
         [0025]    The pick and place head  10  illustrated in the FIG. 1 includes a circular frame  14  that is fixed to an electric motor for rotating the frame  14  about its axis. The plurality of pick-up heads  16  (only one of which is shown) is secured to the outer circumference of the circular frame  14 .  
         [0026]    The pick and place head  10  is mounted on a conventional translating mechanism which enables the pick and place head  10  to be moved in the X, Y axes. The pick and place head  10  also includes some type of vision system (not shown) to detect fiducial markings at or near the intended location so that the pick-up head  16  can be placed with high precision with respect to the intended location. The pick and place head  10  includes an actuating mechanism  30  located at a lower portion thereof. The pick-up head also includes a camera  18 , which is part of a vision system, at another location thereof for positioning a component that has been picked up by the pick-up nozzle on a spindle.  
         [0027]    [0027]FIGS. 2 and 3 illustrate a pick-up head  16  for use with the present invention. The pick-up head  16  includes a spindle  34 , and the spindle  34  includes a pick-up device, such as a vacuum nozzle  44 , for grabbing component  45  to be placed.  
         [0028]    The spindle  34  is slidable within a receiving bore  42 . A flanged or enlarged head  38  at one end of the spindle  34  is intended to be contacted by the activating system  30 . A spring  35  is arranged concentrically with respect to the spindle  34  so as to exert a biasing force between the underside of the head  38  and a fixed portion of the pick-up head  16 .  
         [0029]    A gear mechanism  54  is provided to adjust the angular orientation of the spindle  34  and the component  44  held thereby. The gear mechanism  54  is driven by a motor  58  through a drive train  56 .  
         [0030]    The activating assembly  30  includes an arm  48  that is pivotably mounted about a shaft  50 . At one end of the arm  48 , a contacting surface is provided which makes contact with the head  38  of the spindle  34 . At the opposite end of the arm  48 , a driving lever (not shown) is attached in order to pivot the arm  48  back and forth about the shaft  50 . The activating mechanism is fixed to a lower portion of the frame  14  of the pick and place head  10 . However, other types of activating mechanisms can be used with the present invention, instead of the disclosed activating mechanism.  
         [0031]    In operation, a translating mechanism (not shown) moves the pick and place head  10  to a location above a component to be picked up. The actuating mechanism  30  then actuates the spindle  34  in the pick-up head  16  to the actuating position, wherein the spindle  34  is extended down until the pick-up nozzle contacts and picks up the component  45 . The actuating mechanism  30  then enables the spindle  34  to be retracted.  
         [0032]    In one embodiment, the spring  35  biases the spindle  34  to a retracted position. Accordingly, the actuating mechanism  30  merely depresses the head  38  at one end of the spindle  34 , opposite the pick-up nozzle  44 , in order to extend the spindle  34 . Reference numeral  38 A shows the head of the spindle in its retracted position, and  38 B shows the head of the spindle in its extended position. In order to retract the spindle  34 , the actuating mechanism merely withdraws away from the spindle  34 , enabling the spring  35  to move the spindle  34  to its retracted position. However, it should be noted that the present invention is not limited to any particular type of actuating mechanism or pick-up head. Thus, the present invention may have applicability to other systems using different types of pick-up heads and/or activating mechanisms.  
         [0033]    After the component  45  has been picked up, and the spindle  34  is retracted, the pick and place head  10  is then moved to another location to pick up another component with another pick-up head  16 . At this time, the circular frame  14  is rotated incrementally so that a different pick-up head is in the lowermost or activating position. The activating mechanism  30  then activates the spindle in the next pick-up head to extend the spindle so that it may pick up the next component, as described above with respect to the first pick-up head and the first component. The process is repeated until as many as components as needed or as can fit on the pick and place head  10  are picked up.  
         [0034]    Prior to depositing the components at their intended locations, the components are positioned with respect to their intended location. In a preferred embodiment of the present invention, the positioning is accomplished with a vision system  18 . In the embodiment, the vision system  18  includes two different cameras  20 ,  22 . Such vision systems capable of positioning the components are well known in the industry, and the details thereof are omitted from this specification.  
         [0035]    As the circular frame  14  of the pick and place head  10  rotates, each pick-up head incrementally moves in a circular path around the pick and place head  10 . In order to ensure a highly accurate positioning, the pick and place head  10  interacts with each pick-up head  16 , as the pick-up head  16  passes in front of the vision system  20 , so as to extend the spindle  34 . In one embodiment of the present invention, the spindle  34  is extended by passing the spindle  34  over a cam  28  or a bulge in a stationary part of the pick and place head  10 . Specifically, as the spindle  34  passes over the cam portion, the cam engages the spindle  34 , and urges the spindle  34  against the biasing force of the spring  35  so that the spindle  34  is extended.  
         [0036]    [0036]FIG. 4 is a front elevational view of the cam  28 . The cam  28  includes a bulge or large portion at point A. At point B, the cam  28  is narrower. The cam  28  also includes a cut-out portion  32  at a lower portion thereof. The activating mechanism  30  fits within the cut-out portion  32 .  
         [0037]    Ideally, the cam  28  will extend the spindle  34  the same distance as the spindle is extended when the component  44  is delivered to the intended location. However, for purposes of simplicity, an average extension distance is determined, and the cam is constructed so as to extend each spindle  34  the average distance used. Thus, although each spindle  34  may not be extended to the exact position in which it will be extended when the component  44  is deposited, the differences between the exact position and the position extended by virtue of the cam are not large enough to cause any significant errors. In a preferred embodiment, it is assumed that the average extension distance is 11 millimeters. Accordingly, the bulge or cam shape portion of the pick and place head  10  is intended to extend the spindle 11 millimeters.  
         [0038]    In an alternative embodiment of the present invention, instead of using a cam  28  to extend the spindles  34  in front of the vision system  20 , a second activating system, similar to the aforedescribed activating system  30  at the lower portion of the pick and place head  10 , may be used to extend the spindle  34  in front of the vision system  20 .  
         [0039]    Although the present invention has been described in connection with exemplary embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without departing from the spirit and scope of the invention as defined in the appended claims.