Abstract:
A mounter head is provided for a surface mounting apparatus which is capable of easily controlling a pitch of a mounting device as well as preventing backlash when the device is mounted on a printed circuit board. The mounter head includes a rack block having a rack for moving up and down by means of a pinion rotated by a driving source; a nozzle shaft installed at one side of the moving unit; a nozzle secured to the lower end of the nozzle shaft for sucking a device to be mounted; and a driving source installed corresponding to each nozzle shaft for rotating each nozzle.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a mounter head for a surface mounting apparatus which is capable of easily controlling a pitch of the surface mounting apparatus as well as preventing backlash when the apparatus is mounted on a printed circuit board. 
     2. Description of the Prior Art 
     Electric and electronic products have been developing rapidly with high density, small size and variety. Development of surface mounting technology using a surface mounting apparatus for manufacturing a Printed Circuit Board (PCB) has also developed rapidly. 
     The surface mounting apparatus is a very important component of the surface mounting assembly apparatus for mounting a surface mounting device to the PCB and is supplied with the surface mounting device from a device supplier, which feeds it to a mounting position on the PCB and mounts it on the PCB. 
     The surface mounting apparatus can be divided by function into high-speed apparatus and general-use apparatus. The high-speed apparatus can accomplish a high-speed mounting operation because it is constructed to assemble many devices in a short period of time. Therefore, it has the advantage that it can be utilized for mass production. However, its mounting precision may be reduced. 
     Meanwhile, the general-use apparatus can accomplish a high-precision mounting operation because it is constructed to function with many devices. Therefore, it has the advantage that it can be utilized for medium or small production. However, productivity may be reduced because of the low-speed mounting operation. 
     A surface mounting apparatus comprises a feeder (referring to “a tape feeder” as below) for supplying a device to be mounted, an X-Y gentry for determining a working position, a conveyor for carrying a PCB and a head for picking up, in regular sequence, a device from the feeder and for mounting the device on the PCB. In general, the surface mounting apparatus serves to mount an electronic device on the PCB and can be called a mounter. More detailed structure for the mounter is as follows. 
     The mounter comprises a base assay, a conveyor installed at an upper portion of the base assay for feeding a PCB, a feeder for supplying a device or a chip to be mounted on the PCB, a mounter head assay for mounting each device supplied from the feeder, a vision part for acknowledging and correcting the position of the device, and an X-Y gentry installed with the vision part and the mounter head for determining the position of the table. 
     Meanwhile, the mounter head assay comprises driving means for driving the mounter head, a suction nozzle for directly sucking the device, nozzle fixing means for fixing the sucked device, and a nozzle exchanging apparatus for exchanging the nozzle. 
     The mounter head is constructed to rotate about a R-axis 360 degrees, as shown by arrow R in FIG. 1, to control the rotation angle of the device sucked by the nozzle and along a Z-axis, as shown by arrow Z in FIG. 1, for moving up and down to suck the device by the nozzle The suction nozzle of the mounter head is installed on the nozzle shaft and is rotatable by 360 degrees. The nozzle shaft is rotated on the R-axis by the driving means and is moved up and down on the Z-axis by the pinion and the rack by other driving means. 
     However, the conventional mounter head provides one driving means for rotation pf each of the nozzle shafts about the R-axis. Each nozzle shaft is rotated about the R-axis after the driving motor is connected to the nozzle shaft by a belt. That is, although the first nozzle shaft, which is connected to the driving means correctly receives the rotation angle from the driving means, errors often occur in the rotation of the second, third, and fourth nozzles due to backlash caused by belt slip and the distance between the respective nozzle and the belt. Therefore, the rotating angle of the nozzle shaft can be precisely controlled, thereby causing the device not to be correctly sucked or mounted when the surface mounting device is mounted on the PCB. 
     Therefore, the conventional surface mounting apparatus has the problem of inefficient mounting and the device thus may not work properly. 
     Further, the surface mounting device can be divided into a semiconductor device being supplied from a tape feeder and a semiconductor devices being supplied from a tray feeder. 
     That is, in case of a semiconductor device supplied from a tape feeder, the surface mounting device is supplied with devices from supply rolls. Each roll is disposed at a predetermined distance therefrom, thereby having the same pitch. Accordingly, each nozzle can suck only one device at a time. 
     FIG. 1 shows the structure of a mounter head of a conventional surface mounting apparatus filed by Yamaha in Japan and issued as U.S. Pat. No. 5,377,405. The surface mounting apparatus of FIG. 1 comprises a carriage, a plurality of picker device  124 , sensing means  122 , and a driving source  120 . 
     The surface mounting apparatus having the above construction is operated so that the sensing means  122  senses the devices so as to simultaneously pick up the electronic devices. However, in the conventional apparatus, driving means and peripheral apparatus for moving the mounter head are not provided. That is, each mounter head is constructed to be simultaneously moved by the driving source  120 . Therefore, the conventional nozzle installed at the mounter head simultaneously moves corresponding to the pitch of the surface mounting device supplied to the feeder. However, in the case of a tray feeder in which the device size inserted therein to is different, respectively, a small device inserted into the tray may have a narrow pitch. Further, because a larger-sized device has a wider pitch it is very difficult to suck the device using the conventional nozzle. 
     Because the nozzle is designed to have the same pitch, it works well with a supply of same pitch devices. However, productivity deteriorates when devices having a different pitch device are supplied. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been invented to solve the above problems and it is an object of the present invention to provide a mounter head for a surface mounting apparatus in which the precision of the R-axis rotation is increased by providing a driving means for rotating the nozzle shaft so that the device is correctly sucked and mounted. 
     Another object of the present invention is to provide a mounter head for a surface mounting apparatus which is capable of being applied to a tray feeder having therein a supply of same pitch devices, as well as to a tray feeder having therein a supply of devices each having a different pitch. 
     To accomplish the above objects, the present invention provides a mounter head for a surface mounting apparatus comprising a rack block having a rack which is movable up and down by a pinion rotated by a driving source, a nozzle shaft installed at one side of a moving means, a nozzle secured to a lower end of the nozzle shaft for sucking a device to be mounter, and a driving source installed corresponding to each nozzle shaft for rotating each nozzle. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and aspects of the invention will become apparent from the following description of embodiments with reference to the accompanying drawings in which: 
     FIG. 1 shows a structure of a mounter head of conventional surface mounting apparatus: 
     FIG. 2 is a perspective view showing a structure of a mounter head for a surface mounting apparatus according to the present invention; and 
     FIG. 3 is a side view showing a structure of a mounter head for a surface mounting apparatus according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The mounter head of a surface mounting apparatus according to the present invention is, as shown in FIGS. 2 and 3, constructed so that a fixing block  12  is disposed extending transversely and a moving block  14  is disposed to move in left and right directions along the fixing block  12 , as indicated by arrow A in FIG. 2. A right plate  16  is disposed at the front portion of the moving block  14 . 
     The plate  16  is, at a front left side thereof, provided with a support plate  18 . The support plate  18  is, at a front portion thereof, provided with a camera  100  for informing a user of the position of a device to be mounted on the PCB  52 . Furthermore, the plate  16  is, at a front right upper portion thereof, provided with a bracket  22  secured thereto. A driving motor  20  is mounted on the bracket  22  and extends transversely to the right of the bracket  22 . The driving motor  20  is provided with a belt pulley  24 . The driving motor  20  is, at a lower portion thereof, provided with a ball screw nut  31  to move in the left and right directions. The ball screw nut  31  can move in the left and right directions because the ball screw  28  is coupled to the belt pulley  26 . 
     The plate  16 , at a right portion thereof, extends parallel to a moving plate  36 , as shown in FIG. 3, which is secured to the ball screw nut  30  inserted on the ball screw  28 . The plate  16  and the moving plate  36  are, at a rear portion thereof, provided with LM blocks  32  and  34 , respectively, which are coupled to the X-axis frame  10  to slidingly move in the left and right directions, the direction of Arrow A in FIG.  2 . 
     Meanwhile, the pulley  24  disposed at one side of the motor  20  and the pulley  26  disposed at one side of the ball screw nut  31  are connected to the belt  60 . The pulleys  24  and  26  are rotated by driving the motor  20 , thereby rotating the ball screw  28 . The plate  16 , is at a lower portion thereof, provided with a pair of rack blocks  54  each formed with a rack  50  at one side. The rack blocks  54  are disposed adjacent to one another. The rack  50  is configured to engage with pinion  48 . When the pinion  48  is rotated by a driving source  48   a  the rack block  54  coupled to the pinion  48  via the rack  50  moves up and down. 
     The rack blocks  54  are, at a lower end thereof, provided with a first nozzle shaft  41  and a second nozzle shaft  43 , respectively, which are provided with a first nozzle  40  and a second nozzle  42 , respectively. The first nozzle shaft  41  and the second nozzle shaft  43  are, at center portions thereof, provided with a driving motor  56 , which rotates the first nozzle shaft  41  and the second nozzle shaft  43 , respectively, thereby rotating the first nozzle  40  and the second nozzle  42 , respectively. 
     The driving motors  56  are, at center portions thereof, each provided with a through-hole, and the first, second, third, and fourth nozzle shafts  41 ,  43 ,  45 , and  47  are, at a center portion thereof, provided with a through-hole (not shown) which communicates with a through-hole formed in the nozzles  40 ,  42 ,  44  and  46 . 
     The moving plate  36  is provided with the third nozzle shaft  45  and the fourth nozzle shaft  47 , which have the same height as the first nozzle shaft  41  and the second nozzle shaft  43 . The moving plate  36  is, a front portion thereof, provided with a pair of rack block  54  configured to move up and down, which are each attached to a rack  50 . The rack  50  engages with the pinion  48 . The pinion  48  is rotated by a driving source and enables the engaging rack  50  to be moved to thereby move the rack block  54  up and down in a direction shown by Arrow B in FIG.  2 . 
     Further, the rack blocks  54  are, at a lower end thereof, provided with the third nozzle shaft  45  and the fourth nozzle shaft  47 , respectively, which are provided with the third nozzle  44  and the fourth nozzle  46 , respectively. The third nozzle shaft  45  and the fourth nozzle shaft  47  are, at center portions thereof, each provided with driving motor  56 . When the driving motor  56  is rotated, the third nozzle shaft  45  and the fourth nozzle shaft  47  are rotated, thereby rotating the third nozzle  44  and the fourth nozzle  46 . 
     The mounter head according to the present invention is constructed so that the first nozzle  40 , the second nozzle  42 , the third nozzle  44 , and the fourth nozzle  46  are disposed at a lower end of the first nozzle shaft  41 , the second nozzle shaft  43 , the third nozzle shaft  45 , and the fourth nozzle shaft  47 , respectively. The first nozzle shaft  41 , the second nozzle shaft  43 , the third nozzle shaft  45  and the fourth nozzle shaft  47  are each disposed on a rack block  54 . The nozzle shafts  41 ,  43 ,  45 , and  47  are, at center portions thereof, provided with a driving motor  56  which rotates the respective nozzle shafts  41 ,  43 ,  45  and  47 . By rotating the nozzle shafts  41 ,  43 ,  45 , and  47 , the nozzles  40 ,  42 , 44 , and  46  disposed, respectively, at lower ends thereof each rotates about its respective axis. 
     The nozzles  40 ,  42 ,  44  and  46  accurately suck the device from a feeder (not shown). When the nozzles  40 ,  42 ,  44  and  46  mount the device on the PCB, the backlash due to a time difference between the respective nozzle axes can be prevented, and at the same time, the device can be mounted in transversal and longitudinal directions and at various angles. 
     Meanwhile, the pulley  24  provided at the driving motor  20  and the pulley  26  provided at the ball screw  28  connected to each other by belt  60 . By rotating the driving motor  20 , the ball screw  28  connected to the belt  60  rotates, thereby moving the plate  36  in the left and right directions. 
     The plate  16  is, at a lower right portion, further provided with a first nozzle assay  102  and a second nozzle assay  104 , which are disposed on the pair of rack blocks  54 . The moving plate  36  is provided with a third nozzle assay  106  and a fourth nozzle assay  108  corresponding to the first nozzle assay  102  and the second nozzle assay  104  of the plate  16 . The first nozzle assay  102 , the second nozzle assay  104 , the third nozzle assay  106 , and the fourth nozzle assay  108  comprise the first nozzle  40 , the second nozzle  42 , the third nozzle  44 , and the fourth nozzle  46 , as well as the first nozzle shaft  41 , the second nozzle shaft  43 , the third nozzle shaft  45 , and the fourth nozzle shaft  47 , and the driving motor  56  corresponding to each nozzle shaft. 
     By rotating the driving motor  20 , the pulleys  24  and  26  connected to the belt  60  rotate. The ball screw  28  is rotated so that the plate  36  is moved along the X-axis frame  10  in a straight line. The distance between the first nozzle assay  102  and the second nozzle assay  104 , and the third nozzle  106  and the fourth nozzle assay  108  becomes larger and the pitch is changed by a predetermined amount corresponding to a pitch of the device being supplied. 
     The above descriptions correspond to the case in which the pitch of the device to be mounted is large. However, by rotating the driving motor  20  in forward and reverse directions, the moving plate  36  provided with the third nozzle assay  106  and with the fourth nozzle assay  108  can move in the left and right directions, thereby easily accommodating a small pitch device. 
     According to the present invention, precision is improved by removing backlash caused by a belt, and a tact time can be shortened because different-sized devices can be easily picked up. Further, because the mounter head can be controlled to suck and pick-up a device having a narrow or large pitch, many devices can be served. 
     Having described specific preferred embodiment of the invention with reference to the accompanying drawings, it is to be understood that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.