Abstract:
The cycle time for mounting electronic components supplied from a tray can be shortened. An electronic component feeder ( 16 ) for mounting electronic components has a plurality of height levels (L 1 , L 2 , and L 3 ) and can move tables ( 19, 20, 21 ) horizontally at the respective levels (L 1 , L 2 , and L 3 ). A plurality of conveyers ( 22, 23, 24 ) are provided for the respective tables to move them to a pickup stage (A) from a standby stage (B). Transfer head ( 13 ) includes nozzles ( 14   a,    14   b,    14   c ) for attracting electronic components by suction, and an upward-downward moving mechanism which moves the nozzles in accordance with the height level of each tray on the pickup stage (A). Since the trays are arranged at the different height levels at the pickup stage position, the conveyers can be moved independently and the transfer heads can individually move the nozzles between the position at which each nozzle picks up electronic components and another position at which the nozzle does not interfere with the pickup operation. Movement of a necessary tray from and to the pick up stage position can be performed quickly without being hindered by an other tray and, as a result, the cycle time for mounting electronic components can be shortened.

Description:
FIELD OF THE INVENTION 
     The present invention relates to mounting electronic components using more than one nozzle provided on a transfer head for picking up electronic components placed on more than one vertically-staged tray, and transferring and mounting them onto a substrate. 
     BACKGROUND OF THE INVENTION 
     At present, a common type of electronic component mounting equipment picks up a selection of electronic components supplied via an electronic component feeder by vacuum suction of a transfer head nozzle and transfers and mounts them onto a substrate. There are various types of feeders which supply electronic components to the nozzle of the transfer head, and one type employs a tray. 
     An electronic component feeder of the prior art which employs this tray is explained next. 
     FIG. 13 shows a side view of an electronic component feeder of the prior art. In FIG. 13, a magazine  1  houses a tray  2  which stores more than one electronic component aligned lengthwise and crosswise in vertical multiple stages. A certain in/out level  3  is specified in the conventional electronic component feeder, and the magazine  1  is raised or lowered by elevation means  4  to move the tray  2  to this in/out level  3  for moving the tray  2  to a subsequent pickup stage  6  next. In/out means  5  is for ejecting the tray  2  at the in/out level  3  from the magazine  1  to the pickup stage  6 , or to return the tray  2  on the pickup stage  6  to the magazine  1 . 
     When the tray  2  required to be on the pickup stage  6  (refer to the tray  2  represented by a dotted line) is ejected, a nozzle  8  of a transfer head  7  lowers toward the tray  2 , and an electronic component P on the tray  2  is picked up by suction at the tip of the nozzle  8 . The electronic component P, shown by a dotted line, is then transferred and mounted onto a substrate  9 , for example, a printed circuit board. 
     With the above electronic component feeder of the prior art, however, a long time is required to replace the tray  2  positioned on the pickup stage  6 , resulting in a longer feeding cycle time, which in turn lowers productivity. The reasons are as follows. For replacing the tray  2  shown by the dotted line in FIG. 13 with the tray  2   x  in the magazine  1 , the following series of operations cannot be avoided: 
     (1) the in/out means  5  returns the tray  2  from the pickup up stage  6  to the magazine  1 ; 
     (2) the elevation means  4  raises the magazine  1  to set the tray  2   x  to the in/out level  3 ; and 
     (3) the in/out means  5  ejects the tray  2   x  set to the in/out level  3  to the pickup stage  6 . 
     SUMMARY OF THE INVENTION 
     The present invention provides a method and equipment for mounting electronic components which enables the shortening of feeding cycle time, and which also allows the high speed transfer and mounting of electronic components onto a substrate. 
     The electronic component mounting equipment of the present invention comprises a positioning unit for positioning a substrate, an electronic component feeder for supplying electronic components, and a transfer head which moves between the electronic component feeder and the positioning unit for transferring and mounting supplied electronic components onto a positioned substrate. The abovementioned electronic component feeder comprises tray holders for holding a tray storing more than one electronic component, a frame support having more than one vertical stage for the tray holders so as to move each tray holder horizontally at each height level, and more than one in/out means moving mechanism disposed for the tray holders for transferring each tray holder from a standby stage to a pickup stage. The abovementioned transfer head comprises a nozzle for suctioning electronic components and a vertical movement mechanism for moving the nozzle in accordance with a height of each tray on the pickup stage. 
     The electronic component mounting method of the present invention is to move electronic components stored on a tray to the pickup stage, pick up an electronic component using the nozzle of the transfer head, and mount it on the substrate. In this method, more than one level for ejecting and returning the tray to and from the pickup stage is provided with a certain interval in the vertical direction. The tray is ejected at each level for positioning the tray on the pickup stage, and the electronic component on the tray is then picked up with the nozzle to be mounted on the substrate. 
     The electronic component mounting method of the present invention further picks up electronic components on the trays set at more than one vertical level of the pickup stage with more than one vacuum suction nozzle provided on the transfer head, and transfers and mounts the electronic component onto a substrate positioned with the positioning unit. The transfer head is moved over the trays disposed on the plurality of vertical stages, and electronic components are picked up in order from the upper tray to the lower tray by moving more than one nozzle vertically in order. When one nozzle is lowered for picking up an electronic component, other nozzles which do not pick up electronic components also lower together. 
     The electronic component mounting equipment as configured above operates as follows. 
     Each tray can be independently ejected to and returned from the pickup stage at different levels. The nozzle of the transfer head also moves vertically in response to the level of the tray positioned on the pickup stage by the vertical movement mechanism. This allows prompt setting up of the required tray at the pickup stage as required for picking up the electronic component with the nozzle to immediately mount it on the substrate. In other words, the present invention enables the saving of time required for elevating the magazine and ejecting or returning the tray after elevation, which is unavoidable with the electronic component mounting equipment of the prior art. Accordingly, the mounting cycle time can be reduced. 
     Moreover, by providing more than one level with a certain interval in the vertical axis for ejecting or returning the tray at each level to and from the pickup stage, the ejection or returning operation of a required tray can be promptly executed without interfering with other trays, also resulting in a reduction of the mounting cycle time. Furthermore, by disposing the transfer head over the trays disposed in more than one vertical stage, electronic components are picked up in order from the upper to the lower trays by the vertical movement of more than one nozzle. Those nozzles which do not pick up electronic components also lower together with the nozzle which lowers to pick up electronic components. This allows the reduction of the cycle time required for picking up electronic components on the tray by moving the nozzle vertically and the cycle time required for moving the nozzle over the substrate and then moving vertically again to mount the electronic component on the substrate. Thus, electronic components on the tray can be mounted on the substrate at high speed with good operability. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective of electronic component mounting equipment in accordance with an exemplary embodiment of the present invention. 
     FIG. 2 is a perspective of a part of the electronic component mounting equipment of the present invention. 
     FIG. 3 is a section view of the electronic component mounting equipment of the present invention. 
     FIG. 4 is a perspective of a transfer head of the electronic component mounting equipment of the present invention. 
     FIGS.  5 A- 5 D explain a first example of processes of an electronic component mounting method of the present invention. 
     FIGS.  6 A- 6 C explain a second example of processes of the electronic component mounting method of the present invention. 
     FIGS. 7,  8 ,  9 ,  10 ,  11 , and  12  explain a third example of processes of the electronic component mounting method of the present invention. 
     FIG. 13 is a side view of an electronic component feeder of the prior art. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An exemplary embodiment of the present invention is explained with reference to drawings. 
     One exemplary embodiment of electronic component mounting equipment of the present invention is explained with reference to FIGS. 1 to  4 . In FIG. 1, arrows X, Y, and Z indicate directions. A conveyor  11  is provided over a long distance in the X direction on a top face of a base  10  for transporting a substrate  12  and functioning as a substrate positioning unit for positioning the substrate  12  at a specified position. A transfer head  13  comprises more than one nozzle, for picking up electronic components with vacuum suction at their tips. The transfer head  13  is horizontally movable in X and Y directions on the base  10  by an X table  19 A and a Y table  19 B. An electronic component monitoring unit  40  is disposed at the side of the conveyor  11 . A transfer direction of the substrate  12  by the conveyor  11  is the X direction. 
     An electronic component feeder  16  is for supplying electronic components. A frame  17  of the electronic component feeder  16  is fixed to the base  10 . The electronic component feeder  16  is disposed with a side toward the conveyor  11 , and comprises a pickup stage A, which is an area for picking up an electronic component by suction with a nozzle of the transfer head  13 , a standby stage B at the center, and a refill stage C which is disposed at the opposite side of the pickup stage A for refilling electronic components by replacing an empty tray with another tray. A cover  18  is provided over the standby stage B. A parts feeder  15  is for supplying electronic components which are not provided in trays (e.g. a tape feeder and a tube feeder). 
     An outline of the internal structure of the electronic component feeder  16  is explained with reference to FIG.  2 . As shown in FIG. 2, the electronic component feeder  16  of the exemplary embodiment of the present invention has three tables, which are a first table  19 , a second table  20 , and a third table  21  from the bottom. The first table  19  is connected to a first conveyor  22 , the second table  20  to a second conveyor  23 , and the third table  21  to a third conveyor  24 . The first conveyor  22  is driven independently by a first motor  25 , the second conveyor  23  by a second motor  26 , and the third conveyor  24  by a third motor  27 . Accordingly, the first table  19 , second table  20 , and third table  21  can be independently taken in and out in the direction shown by arrows N 1 , N 2 , and N 3 . The first table  19 , second table  20 , and third table  21  are equivalent to a tray holder for holding the tray, and the first conveyor  22 , second conveyor  23 , and third conveyor  24  are equivalent to the in/out means. 
     Detailed structure of the electronic component feeder  16  of the exemplary embodiment of the present invention is explained with reference to FIG.  3 . As shown in FIG. 3, a first stage  17   a , second stage  17   b , and third stage  17   c  are provided on the upper part of the frame  17 , and they are stepped downward from the center to the outside. A slider S fixed to the bottom face of the first table  19  is fitted in slidable fashion to the first guide  28  fixed to the first stage  17   a . In the same way, the second table  20  and the third table  21  are supported in slidable fashion respectively by the second guide  29  fixed to the second stage  17   b  and the third guide  30  fixed to the third stage  17   c . A first tray  31  stores the first electronic component  32  and is placed on the first table  19 , a second tray  33  stores the second electronic component  34  and is placed on the second table  20 , and a third tray  35  stores the third electronic component  36  and is placed on the third table  21 . Here, in each tray placed on each table, the first tray  31  is positioned at the first level L 1 , which is the bottom stage, the second tray  33  is positioned at the second level L 2 , which is the middle stage, and the third tray  35  is positioned at the third level L 3 , which is the top stage. The level L 0  is a monitoring level for electronic components (to be explained later). 
     The side of the second table  20  is bent vertically downward at the outside of the first table  19 , and then bent perpendicularly towards the frame  17  at the bottom of the first table  19 , reaching the slider S. In other words, the side of the second table  20  detours around the first table  19  and bends towards the center of the frame so that the structure of the electronic component feeder  16  can be made more compact by minimizing the width of the second table  20 . With the same intention, the side of the third table  21  is designed to detour around the second table  20 , and is bent towards the center of the frame  17  to reach the slider S. 
     Next, the structure of the transfer head  13  and a monitoring unit  40  is explained with reference to FIG.  4 . The transfer head  13  comprises a first nozzle  14   a , second nozzle  14   b , and third nozzle  14   c  which move vertically and independently from each other. As explained later, they pick up the first electronic component  32 , second electronic component  34 , and third electronic component  36 , respectively, by suction, and transfer and mount them on the substrate  12 . 
     The first nozzle  14   a , second nozzle  14   b , and third nozzle  14   c  have the same vertical movement mechanism. These nozzles comprise a head frame  51 , a feeding screw  52  which is vertically held by the head frame  51 , a z-axis motor  53  which is mounted onto the upper part of the head frame  51  for rotating the feeding screw  52 , a nut  54  which is hinged to the feeding screw  52 , and moves vertically when the feeding screw  52  is rotated, a nozzle shaft  55  vertically provided on the nut  54 , and a round back plate  56  attached to the nozzle shaft  55 . The nozzle shaft  55  rotates by an angle θ when driven by a head motor  57  and a belt  58 . Accordingly, when the z-axis motor  53  rotates clockwise or counterclockwise, the nut  54  moves upward or downward along the feeding screw  52 , and the first nozzle  14   a , second nozzle  14   b , and third nozzle  14   c  move upward or downward. When the head motor  57  rotates, the nozzle shaft  55  rotates by angle θ for correcting the horizontal rotation angle of the electronic component picked up by suction at the tip of the first nozzle  14   a , second nozzle  14   b , and third nozzle  14   c.    
     The monitoring unit  40  is configured to house a line sensor  42  inside a box  41 . The longer side of the line sensor  42  is provided along the Y axis, and a slit  43  is opened corresponding to the line sensor  42  at the upper face of the box  41 . The transfer head  13  moves perpendicularly (along the X axis) to the direction of the line sensor  42  (y axis) over the slit  43 . The first nozzle  14   a , second nozzle  14   b , and third nozzle  14   c  are arranged in a line along the X axis. Accordingly, the first electronic component  32 , second electronic component  34 , and third electronic component  36 , picked up by suction at the tip of each nozzle, traverse the line sensor  42  as the transfer head  13  linearly moves along the X axis. This enables continuous high speed monitoring of these electronic components to detect any deviation in the x, y, and θ directions. 
     Next, a first example of an electronic component mounting method in the exemplary embodiment of the present invention is explained. 
     FIGS.  5 A- 5 D explain processes of a first example of the electronic component mounting method. As shown in FIG. 5A, the first tray  31 , second tray  33 , and third tray  35  are placed on the standby stage B. Next, in FIG.5B, the first tray  31 , second tray  33 , and third tray  35  are moved to the pickup stage A at once before the transfer head  13  reaches the pickup stage A. Then, at the third level L 3 , the first nozzle  14   a  picks up the third electronic component  36  from the third tray  35  on the top stage. 
     After completing the pickup operation at the third level L 3 , the third tray  35  immediately returns to the standby stage B as shown in FIG.  5 C. After the third tray  35  returns, the second nozzle  14   b  immediately picks up the second electronic component  34  from the second tray  33  at the second level L 2 , and mounts it on the substrate  12 . Here, the present invention saves the time spent for elevating the magazine or ejecting the next tray to the pickup stage A as required with the electronic component mounting equipment of the prior art, enabling a reduction of the electronic component mounting time. 
     After completing the pickup operation for the second tray  33 , the second tray  33  is immediately returned to the standby stage B as shown in FIG.  5 D. The first electronic component  32  on the first tray  31  positioned at the first level L 1  is then picked up. When the second tray  33  at the standby stage B becomes empty, the second tray  33  is moved to the refill stage C (shown by a chain line), and the tray is refilled by replacing it with a new tray full of second electronic components  34 . The electronic components  36 ,  34 , and  32  can be mounted onto the substrate  12  after picking up all of them. 
     Next, a second example of the electronic component mounting method in the exemplary embodiment of the present invention is explained. 
     FIGS.  6 A- 6 C explain processes of the second example of the electronic component mounting method. In this example, trays are not required to be returned to the standby stage B as in the first example explained above. The trays can be switched with only a small returning operation. Specifically, the first tray  31 , second tray  33 , and third tray  35  are first aligned as show in FIG. 6A, and the first nozzle  14   a  picks up the third electronic component  36  from the third tray  35 . Next, the third tray  35  is returned relative to the first tray  31  and second tray  33  over double the length of the alignment pitch of the electronic components, and the transfer head  13  is moved only for the length of the electronic component alignment pitch for picking up the second electronic component  34  from the second tray  33  with the second nozzle  14   b . As shown in FIG. 6C, the second tray  33  is returned over the same distance as the third tray  35  so that only the first tray  31  protrudes from the second tray  33  and the third tray  35 . The first electronic component  32  is then picked up from the first tray  31  with the third nozzle  14   c.    
     Then, the transfer head  13  is moved over the substrate  12 , and the third electronic component  36 , second electronic component  34 , and first electronic component  32  that have been picked up are mounted onto the substrate  12 . In this way, the stroke for returning the second tray  33  and third tray  35  can be minimized to the degree required to avoid interfering with pickup of the first electronic component  32  from the first tray  31  on the lowest stage, enabling a shortening of the time required for mounting electronic components. 
     A third example of the electronic component mounting method in the exemplary embodiment of the present invention is explained next. 
     FIGS. 7 to  12  explain processes of the third example of the electronic component mounting method, showing the sequence of operations. Specifically, as shown in FIG. 7, the first tray  31 , second tray  33 , and third tray  35  are taken out from the standby stage B to the pickup stage A. Here, the first level L 1  of the first tray  31  on the lowest stage is completely leveled or approximately leveled to the monitoring level L 0  for electronic components and the upper face level of the substrate  12  (electronic component mounting level). The reason is explained later. 
     As shown in FIG. 7, the transfer head  13  is moved over the pickup stage A. At first, the first nozzle  14   a , second nozzle  14   b , and third nozzle  14   c  are set to the highest level, and only the third nozzle  14   c  is first lowered and raised to pick up the third electronic component  36  in the third tray  35  at the top stage by suction. 
     Next, as shown in FIG. 8, the third tray  35  returns to the standby stage B, to expose the second tray  33 . The second nozzle  14   b  is then lowered or raised to pick up the second electronic component  34  as shown in FIG.  9 . At this point, the first nozzle  14   a  and third nozzle  14   c , which do not pick up electronic components, are also lowered for the stroke H 1  following the lowering operation of the second nozzle  14   b.    
     Next, as shown in FIG. 10, the second tray  33  is returned to the standby stage B to expose the first tray  31 . The first nozzle  14   a  is lowered or raised to pick up the first electronic component  32 . Here, the second nozzle  14   b  and third nozzle  14   c  which have already picked up electronic components also lower for the stroke H 2  following the lowering operation of the first nozzle  14   a.    
     As explained above, after the third nozzle  14   c , second nozzle  14   b , and first nozzle  14   a  respectively pick up the third electronic component  36 , second electronic component  34 , and first electronic component  32  in order, the transfer head  13  moves over the monitoring unit  40  as shown in FIG. 11 for checking any deviation in the position of the third electronic component  36 , second electronic component  34 , and first electronic component  32  (also refer to FIG.  4 ). 
     In this case, all the electronic components  36 ,  34 , and  32  are positioned at the monitoring level L 0  of the monitoring unit  40  by driving the z-axis motor  53  to lower the first nozzle  14   a , second nozzle  14   b , and third nozzle  14   c . When picking up the last component as shown in FIG. 10, not only the first nozzle  14   a  which picks up the first electronic component  32 , but also the second nozzle  14   b  and third nozzle  14   c  which have already picked up the second electronic component  34  and third electronic component  36 , and not picked up electronic components in the process shown in FIG. 10, are already lowered together with the first nozzle  14   a . Accordingly, the lowering stroke H 3  for lowering the third electronic component  36 , second electronic component  34 , and first electronic component  32  from the first level L 1  to the monitoring level L 0  can be made very short. Thus, the three electronic components  36 ,  34 , and  32  can be continuously monitored at high speed in a well arranged manner for detecting positional deviations in the x, y, and θ directions. It is apparent that this lowering stroke H 3  can be set at  0  by setting the monitoring unit  40  at a somewhat higher level. 
     As shown in FIG. 12, the transfer head  13  then moves over the substrate  12 , and the third nozzle  14   c , second nozzle  14   b , and first nozzle  14   a  lower or rise separately to mount the three electronic components  36 ,  34 , and  32  one by one at specified coordinates on the substrate  12 . Also in this case, since the first nozzle  14   a , second nozzle  14   b , and third nozzle  14   c  are already lowered to the monitoring level L 0 , the low level, as shown in FIG. 11, the lowering stroke H 4  for mounting the electronic components  36 ,  34 , and  32  can be shortened, enabling high-speed mounting. Deviation in the X and Y directions detected by the monitoring unit  40  is corrected by adjusting the movement stroke of the transfer head  13  relative to the X axis and Y axis of the substrate  12 . Deviation in the θ direction is corrected by rotating the nozzle shaft  55  by driving the head motor  57  shown in FIG.  4 . 
     The electronic component mounting equipment of the present invention enables ejection and return of each tray independently to and from the pickup stage at different levels. The nozzle of the transfer head can also be moved vertically in response to the level of each tray positioned on the pickup stage by the vertical movement mechanism so that the required tray can be quickly positioned at the pickup stage at the required time for immediately picking up an electronic component with the nozzle for mounting it on the substrate. In other words, the present invention saves the time required for elevating the magazine and taking in and out the tray after elevation, which was unavoidable with the conventional electronic component mounting equipment, thus shortening the mounting cycle time. 
     The electronic component mounting method of the present invention enables the ejection and return of a required tray promptly without interfering with other trays by providing more than one level with a certain interval in the vertical direction for ejecting and returning trays to and from the pickup stage. As a result, the mounting cycle time can be shortened. 
     Moreover, the electronic component mounting method of the present invention positions the transfer head over the trays disposed at more than one vertical level to pick up electronic components from in order of upper tray to lower tray by moving more than one nozzle vertically in order. In addition, the nozzles which do not pick up electronic components follow the lowering operation of the nozzle which picks up an electronic component so that the cycle time required for picking up an electronic component from the tray by vertically moving the nozzles and the cycle time required for moving the nozzles over the substrate and moving the nozzles vertically again to mount electronic components onto the substrate can be greatly shortened. Accordingly, the present invention allows the mounting of electronic components in trays onto the substrate at high speed and with good operability.