Patent Publication Number: US-2015075721-A1

Title: Screen printer and component mounting line

Description:
BACKGROUND 
     1. Technical Field 
     An aspect of the present invention relates to a screen printer for forming paste prints on boards using a mask formed with patterns. Another aspect of the invention relates to a component mounting line including the screen printer. 
     2. Background Art 
     There is a screen printer which performs, in parallel, screen printing operations for forming prints of paste such as solder on plural kinds of boards and successively supplies resulting boards to a two-lane component mounter (i.e., a component mounter equipped with two board conveying lanes) installed on a downstream side. JP-A-2009-070867 describes a screen equipped with two printing units. Each of the printing units includes a board holding unit and a mask and performs a screen printing operation. However, the screen printer becomes large, and cost is increased. JP-A-2011-143640 describes a screen printer including a single printing unit. The printing unit includes a mask having two pattern-formed areas each of which has a pattern formed therein. The screen printer further includes a board holding unit which holds a board and which is movable under the mask such that the board selectively contacts one of the two pattern-formed areas, whereby screen printing operations are performed using the respective patterns. 
     SUMMARY 
     However, even in the above-described screen printer having two pattern-formed areas for a component mounter on a downstream process side, the screen printer requires two print heads: one for printing using a first pattern and the other for printing using a second pattern. Therefore, the structure of the screen printer becomes complex. Further, because of the two print heads, they waste a larger amount of paste than a screen printer with a single print head, and cost is increased in this respect. 
     An object of an aspect of the present invention is to provide a screen printer and a component mounting line which can perform printing operations on plural kinds of boards in parallel with a simple configuration while enabling reduction of the amount of paste wasted. 
     A first aspect of the present invention provides a screen printer including: a mask having a first area formed with a first pattern and a second area formed with a second pattern such that the first area and the second area are arranged in an arrangement direction; a board holding/moving mechanism which is movable in the arrangement direction under the mask, and which includes a board holding unit which holds a board so as to allow the board to selectively contact one of the first area and the second area by moving the board holding unit; and a print head which forms a past printing on the board through the mask, and which is movable on the mask in the arrangement direction, wherein when a paste print is formed on the board contacting the first area by using the first pattern, the print head moves in the arrangement direction from a start position located between the first area and the second area to the first area and then returns to the start position, and wherein when a paste print is formed on the board contacting the second area by using the second pattern, the print head moves in the arrangement direction from the start position to the second area and then returns to the start position. 
     A second aspect of the present invention provides the screen printer according to the first aspect further including: a board carry-in unit which is movable in the arrangement direction, and which transfers a board carried in from an upstream machine to the board holding/moving mechanism; and a board carry-out unit which is movable in the arrangement direction, and which receives the board on which a paste print has been formed by the print head from the board holding/moving mechanism and carries out the board to a downstream machine. 
     A third aspect of the present invention provides a component mounting line including: the screen printer according to the first or second aspect; and a component mounter which mounts a component on the board on which the paste print has been formed by the screen printer; wherein the component mounter includes a first board conveying lane and a second board conveying lane which are arranged in the arrangement direction, wherein the first board conveying lane carries in the board on which the paste print has been formed using the first pattern, and wherein the second conveying lane carries in the board on which the paste print has been formed using the second pattern. 
     A fourth aspect of the present invention provides the screen printer according to the first aspect further including: a board carry-in unit which is movable in the arrangement direction, and which transfers a board carried in from an upstream machine to the board holding/moving mechanism, and a board carry-out unit which receives the board on which the paste print has been formed by the print head from the board holding/moving mechanism, and which carries out the board to a downstream machine, wherein the board holding/moving mechanism is movable among a first position corresponding to the first area, a second position corresponding to the second area, and a third position which is located between the first position and the second position and at which the board is received from the board carry-in unit and transferred to the board carry-out unit. 
     A fifth aspect of the present invention provides a component mounting line including: the screen printer according to the first or fourth aspect; and a component mounter which mounts a component on the board on which the paste print has been formed by the screen printer; and wherein the component mounter includes a board conveying lane which carries in the board on which the paste print has been formed by using the first pattern and the board on which the paste print has been formed by using the second pattern. 
     In the aspects of the present invention, a paste print is formed as the print head reciprocates between the first or second area and the start position located between the first area and the second area on the mask. The single print head serves as both of a print head for printing with the first pattern and printing with the second pattern. Consequently, it is possible to perform, with a simple configuration, printing on plural kinds of boards in parallel so as to correspond with the two-lane component mounter installed on a downstream side. Furthermore, since the print head reciprocates, that is, moves from the start position located between the first area and the second area and returns to the original position (start position), residual paste can be used for the next printing irrespective of whether printing has been performed using the first pattern or the second pattern. Therefore, the amount of paste wasted is reduced and hence the cost can be reduced accordingly. Still further, since the paste on the mask is returned to a region between the first area and the second area on the mask when a printing operation has been completed, printing operations can be started immediately even if different kinds of boards are carried in in random order (i.e., a printing operation can be started immediately irrespective of whether a board contacts the first area or the second area). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a general configuration of a component mounting line according to a first embodiment of the present invention; 
         FIG. 2  is a plan view of a screen printer which forms a part of the component mounting line according to the first embodiment; 
         FIG. 3  is a side view of the screen printer according to the first embodiment; 
         FIG. 4  is a plan view of a mask provided in the screen printer according to the first embodiment; 
         FIGS. 5A and 5B  are partial sectional views of the screen printer according to the first embodiment; 
         FIG. 6  is a block diagram of a control system of the screen printer according to the first embodiment; 
         FIGS. 7A to 7E  are operation diagrams of the screen printer according to the first embodiment; 
         FIGS. 8A and 8B  are operation diagrams of the screen printer according to the first embodiment; 
         FIGS. 9A and 9B  are operation diagrams of the screen printer according to the first embodiment; 
         FIGS. 10A and 10B  are operation diagrams of the screen printer according to the first embodiment; 
         FIGS. 11A and 11B  are operation diagrams of the screen printer according to the first embodiment; 
         FIG. 12  shows a general configuration of a component mounting line according to a second embodiment of the present invention; 
         FIG. 13  is a plan view of a screen printer which forms a part of the component mounting line according to the second embodiment; 
         FIGS. 14A to 14C  are partial plan views of the screen printer according to the second embodiment; and 
         FIGS. 15A to 15F  are operation diagrams of the screen printer according to the second embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     First Embodiment 
       FIG. 1  shows a component mounting line  1  according to a first embodiment of the invention. The component mounting line  1 , which is to manufacture component-mounted boards by mounting a component  3  on each board  2 , includes a screen printer  5  for forming, by screen printing, paste layers Pst such as solder layers on electrodes  2   a  of each board  2  supplied from one of board supply units  4  and a component mounter  6  for mounting a component  3  on each board  2  on which paste layers Pst have been formed by the screen printer  5 . In the component mounting line  1  according to the first embodiment, each board  2  flows left to right in  FIG. 1  (in the left to right direction as viewed by an operator OP). This direction in a horizontal plane is defined as the positive X-axis direction. The direction that is perpendicular to the X-axis direction in the horizontal plane is defined as the Y-axis direction, and the top-bottom direction is defined as the Z-axis direction. In the first embodiment, the left side and the right side in the paper surface of  FIG. 1  are the upstream (process) side and the downstream (process) side of the flow of a board  2 , respectively. 
     As shown in  FIGS. 2 and 3 , the screen printer  5  is equipped with a board holding/moving mechanism  12  on a stage  11 . A mask  13  which is formed with patterns (a first pattern PT 1  and a second pattern PT 2  shown in  FIG. 4 ) according to which prints should be formed on boards  2  is disposed over the board holding/moving mechanism  12 . A carry-in conveyor  14  as a board carry-in unit for transferring a board  2  that is carried in from another, upstream machine (in the first embodiment, one of the board supply units  4 ) to the board holding/moving mechanism  12  is disposed on the stage  11  upstream of the board holding/moving mechanism  12  in the flow of a board  2  (i.e., on the left side in the paper surface of  FIG. 1 ). A carry-out conveyor  15  as a board carry-out unit for receiving a board  2  from the board holding/moving mechanism  12  and carrying it out to another, downstream machine (in the first embodiment, component mounter  6 ) is disposed on the stage  11  downstream of the board holding/moving mechanism  12  in the flow of a board  2  (i.e., on the right side in the paper surface of  FIG. 1 ). The screen printer  5  is also equipped with a print head  17  which is disposed over the mask  13  and moved by a print head moving mechanism  16 , a paste supply syringe  18  which is integral with the print head  17 , and a camera unit  20  which is disposed under the mask  13  and moved by a camera moving mechanism  19  in a horizontal plane. 
     As shown in  FIG. 3 , the board holding/moving mechanism  12  of the screen printer  5  includes a board holding unit  21  for holding a board  2  and a board holding unit moving mechanism  22  for moving the board holding unit  21 . The board holding unit  21  is equipped with an elevation plate  31  which serves as a base, a pair of conveyors  33  (also see  FIG. 2 ) which are attached to conveyor support members  32  which extend upward from the elevation plate  31 , a support member  35  which is elevated and lowered over the elevation plate  31  by an elevation motor  34  which is attached to the elevation plate  31 , and a pair of clampers  37  (also see  FIG. 2 ) which are disposed over the respective conveyors  33  and opened and closed in the Y-axis direction by a clamper drive motor  36 . The conveyors  33  convey, in the X-axis direction, a board  2  received from the carry-in conveyor  14  and positions it at a prescribed clamping position. The support member  35  supports, from below, the board  2  that has been positioned at the clamping position. The clampers  37  clamp, in the Y-axis direction, the board  2  being supported by the support member  35  when pressed against its side surfaces that are opposed to each other in the Y-axis direction. Of the two clampers  37  which are arranged in the Y-axis direction, the one located on the side of the operator OP (on the right side in the paper surface of  FIG. 3  which is defined as the front side) is called a front clamper  37 F and the other one opposite to the operator OP (on the left side in the paper surface of  FIG. 3  which is defined as the rear side) is called a rear clamper  37 R. 
     As shown in  FIG. 3 , the board holding unit moving mechanism  22  includes an XYθ table mechanism  41  for moving a base table  41   d  in a horizontal plane by causing a Y table  41   a , an X table  41   b , and a θ table  41   c  which are stacked on the stage  11  to move relative to each other and a second elevation motor  42  for elevating and lowering the elevation plate  31  (i.e., the entire board holding unit  21 ) relative to the base table  41   d . The board holding unit moving mechanism  22  moves the board holding unit  21  which holds a board  2  (clamped by the dampers  37 ) in a horizontal plane by means of the XYθ table mechanism  41  and elevates and lowers it by means of the second elevation motor  42 . 
     As shown in  FIG. 4 , the mask  13  has a flat, rectangular shape extending in the XY plane and its outer circumferential portion is supported by a frame member  13   w . To enable screen printing for two kinds of boards  2 , a first pattern-formed area (a first area) R 1  in which a first pattern PT 1  is formed and a second pattern-formed area (a second area) R 2  in which a first pattern PT 2  is formed are arranged in the Y-axis direction (an arrangement direction in a horizontal plane). Reference is also made to  FIGS. 5A and 5B . 
     As shown in  FIG. 2 , the carry-in conveyor  14  can be moved by a carry-in conveyor moving mechanism  14   a  in the Y-axis direction (in the arrangement direction of the first pattern-formed area R 1  and the second pattern-formed area R 2  of the mask  13 ). As shown in  FIG. 1 , two board supply units  4  are disposed upstream of the screen printer  5  so as to be arranged in the Y-axis direction. Moved in the Y-axis direction by the carry-in conveyor moving mechanism  14   a , the carry-in conveyor  14  can receive a board  2  from either of the two board supply units  4  and can transfer a board  2  to the board holding unit  21  whether it is located under the first pattern-formed area R 1  or the second pattern-formed area R 2 . As shown in  FIG. 2 , the carry-out conveyor  15  can be moved by a carry-out conveyor moving mechanism  15   a  in the Y-axis direction, whereby the carry-out conveyor  15  can receive a board  2  from the board holding unit  21  whether it is located under the first pattern-formed area R 1  or the second pattern-formed area R 2 . 
     As shown in  FIG. 2 , a pair of board-side marks  2   m  are formed in each board  2  at diagonal positions (only one pair of board-side marks  2   m  are shown in  FIG. 2 ). A pair of mask-side marks  13   m  are formed in each of the first pattern-formed area R 1  and the second pattern-formed area R 2  of the mask  13  so as to correspond to the pair of board-side marks  2   m  (also see  FIG. 4 ). If a board  2  being held by the board holding unit  21  is brought into contact with the mask  13  by elevating the board holding unit  21  by the second elevation motor  42  with the pair of board-side marks  2   m  registered with the pair of mask-side marks  13   m  of the first pattern-formed area R 1  in a plan view, a state is established that the electrodes  2   a  on the board  2  are registered with the first pattern PT 1  of the mask  13  (see  FIG. 5A ). Likewise, if a board  2  being held by the board holding unit  21  is brought into contact with the mask  13  by elevating the board holding unit  21  by the second elevation motor  42  with the pair of board-side marks  2   m  registered with the pair of mask-side marks  13   m  of the second pattern-formed area R 2  in a plan view, a state is established that the electrodes  2   a  on the board  2  are registered with the second pattern PT 2  of the mask  13  (see  FIG. 5B ). In this manner, in the first embodiment, the board holding/moving mechanism  12  moves the board holding unit  21  which is holding a board  2  and is disposed under the mask  13  so as to be movable in the arrangement direction (the arrangement direction of the first pattern-formed area R 1  and the second pattern-formed area R 2 ), whereby the board  2  is brought into contact with a selected one of the first pattern-formed area R 1  and the second pattern-formed area R 2 . 
     As shown in  FIGS. 5A and 5B , in the first embodiment, a region of the mask  13  where the rear clamper  37 R comes into contact with the mask  13  when a board  2  is brought into contact with the first pattern-formed area R 1  of the mask  13  and a region of the mask  13  where the front clamper  37 F comes into contact with the mask  13  when a board  2  is brought into contact with the second pattern-formed area R 2  of the mask  13  are in the same region Rm which is located between the first pattern-formed area R 1  and the second pattern-formed area R 2 . Therefore, irrespective of whether a board  2  is brought in contact with the first pattern-formed area R 1  or the second pattern-formed area R 2 , one clamper  37  (i.e., one of the front clamper  37 F and the rear clamper  37 R) is located in the region Rm between the first pattern-formed area R 1  and the second pattern-formed area R 2 . 
     As shown in  FIGS. 2 and 3 , the print head  17  is equipped with two squeegees  52  which are disposed under a movable base  51  extending in the X-axis direction so as to be opposed to each other in the Y-axis direction. The print head moving mechanism  16  includes two print head moving ball screws  16   a  which extend in the Y-axis direction, penetrate through and are screwed into left and right end portions of the movable base  51 , respectively, and two print head moving motors  16   b  for rotationally driving the two respective print head moving ball screws  16   a . When the two print head moving ball screws  16   a  are rotated in synchronism with each other by the two print head moving motors  16   b , the movable base  51  is moved in the Y-axis direction. The two squeegees  52  are elevated and lowered individually under the movable base  51  by respective squeegee elevation cylinders  53  which are provided on the movable base  51 . Of the two squeegees  52  arranged in the Y-axis direction, the one located on the side of the operator OP (i.e., on the right side in the paper surface of  FIG. 3 ) is called a front squeegee  52 F and the other one opposite to the operator OP (on the left side in the paper surface of  FIG. 3 ) is called a rear squeegee  52 R. 
     As shown in  FIGS. 2 and 3 , the camera unit  20  is equipped with an upper field shooting camera  20   a  whose field of view is located above and a lower field shooting camera  20   b  whose field of view is located below. A camera unit moving mechanism  19  for moving the camera unit  20  in a horizontal plane is equipped with a Y-axis table  19   a  which extends in the Y-axis direction over the stage  11 , an X-axis table  19   b  which extends in the X-axis direction and is moved on the Y-axis table  19   a , and a movable plate  19   c  which is moved on the X-axis table  19   b . Attached to the movable plate  19   c , the camera unit  20  is moved in a horizontal plane when the X-axis table  19   b  is moved in the Y-axis direction relative to the Y-axis table  19   a  and the movable plate  19   c  is moved in the X-axis direction relative to the X-axis table  19   b.    
     Stored with paste Pst inside, the paste supply syringe  18  discharges paste Pst downward. As shown in  FIGS. 2 and 3 , the paste supply syringe  18 , which is attached to the movable base  51 , can be moved in the Y-axis direction together with the squeegees  52  when the movable base  51  is moved in the Y-axis direction. The paste supply syringe  18  can also be moved in the X-axis direction on the movable base  51 . The paste supply syringe  18  can move freely in a horizontal plane as a result of a movement of the movable base  51  in the Y-axis direction and a movement of the paste supply syringe  18  itself in the X-axis direction, whereby the paste supply syringe  18  can supply paste Pst to any region on the mask  13 . The paste supply syringe  18  supplies paste Pst to the region Rm between the first pattern-formed area R 1  and the second pattern-formed area R 2  in a shape that extends in the extending direction (X-axis direction) of the squeegees  52 . 
     As shown in  FIG. 6 , a control device  60  of the screen printer  5  controls an operation of moving the carry-in conveyor  14  in the Y-axis direction which is performed by the carry-in conveyor moving mechanism  14   a , an operation of carrying in a board  2  which is performed by the carry-in conveyor  14 , an operation of moving a board  2  to the clamping position which is performed by the conveyors  33 , an operation of elevating or lowering the support member  35  which is performed by the first elevation motor  34 , an operation of causing the clampers  37  to clamp a board  2  which is performed by the clamper drive motor  36 , an operation of moving the board holding unit  21  in a horizontal plane which is performed by the XYθ table mechanism  41 , an operation of elevating or lowering the board holding unit  21  which is performed by the second elevation motor  42 , an operation of moving the carry-out conveyor  15  in the Y-axis direction which is performed by the carry-out conveyor moving mechanism  15   a , and a control of carrying out a board  2  which is performed by the carry-out conveyor  15 . The control device  60  also controls an operation of moving the print head  17  in the Y-axis direction which is performed by the print head moving mechanism  16 , an operation of elevating or lowering each squeegee  52  which is performed by the associated squeegee elevation cylinder  53 , an operation of discharging paste Pst which is performed by the paste supply syringe  18 , and an operation of moving the camera unit  20  in a horizontal plane which is performed by the camera unit moving mechanism  19 . 
     Referring to  FIG. 6 , the upper field shooting camera  20   a  shoots the mask-side marks  13   m  formed in the first pattern-formed area R 1  of the mask  13  and mask-side marks  13   m  formed in the second pattern-formed area R 1  of the mask  13  under the control of the control device  60 . The lower field shooting camera  20   b  shoots the board-side marks  2   m  of a board  2  which is being held by the board holding unit  21 , under the control of the control device  60 . Both of image data taken by the upper field shooting camera  20   a  and image data taken by the lower field shooting camera  20   b  are input to the control device  60  and subjected to image processing in an image processing unit of the control device  60 . The control device  60  calculates positions of the respective mask-side marks  13   m  and positions of the respective board-side marks  2   m  on the basis of resulting images (shooting results) of the mask-side marks  13   m  and the board-side marks  2   m.    
     As shown in  FIG. 2 , the front side (opposed to the operator OP) of the stage  11  is provided with an operating panel  61  with a display device to be manipulated by the operator OP. The operating panel  61  is connected to the control device  60  (see  FIG. 6 ). Through the operating panel  61 , the operator OP can perform every manipulation relating to the screen printer  5  and acquire various kinds of information relating to the screen printer  5 . 
     Next, a procedure according which the screen printer  5  performs a screen printing operation will be described with reference to  FIGS. 7A to 11B . When a board  2  is to be output from one of the two board supply units  4 , the control device  60  controls the carry-in conveyor moving mechanism  14   a  so that it moves the carry-in conveyor  14  to such a position that it is opposed to the board supply unit  4  that is going to output the board  2 . The control device  60  causes the carry-in conveyor  14  to receive the board  2  that is output from the board supply unit  4 , and controls the XYθ table mechanism  41  so that it moves the board holding unit  21  to a position (first position) that is located under the first pattern-formed area R 1  or a position (second position) that is located under the second pattern-formed area R 2  (see  FIG. 7A ). Whether the board holding unit  21  should be moved to the first position or the second position is determined by the kind of the board  2  (i.e., the arrangement of the electrodes  2   a ). The board holding unit  21  is moved to the first position if the arrangement of the electrodes  2   a  corresponds to the first pattern PT 1 , and to the second position if the arrangement of the electrodes  2   a  corresponds to the second pattern PT 2 .  FIG. 7A  shows a state in which the board holding unit  21  is placed at the first position. 
     When the board holding unit  21  has been moved to the first position or second position, the control device  60  controls the carry-in conveyor moving mechanism  14   a  so that it moves the carry-in conveyor  14  that has received the board  2  to a position corresponding to the first position or the second position (see  FIG. 7B ). More specifically, the carry-in conveyor  14  is moved to the position corresponding to the first position or second position if the board holding unit  21  is placed at the first position, and to the position corresponding to the second position if the board holding unit  21  is placed at the second position.  FIG. 7B  shows a state in which the carry-in conveyor  14  is placed at a position opposing the first position. 
     When the board holding unit  21  has been moved to the position corresponding to the first position or the second position, the control device  60  causes the carry-in conveyor  14  and the conveyors  33  of the board holding unit  21  to operate in link with each other so that the board  2  is put into the board holding unit  21  and positioned at the clamping position (see  FIG. 7C ). Then the control device  60  controls the first elevation motor  34  so that it elevates the support member  35  to support the board  2  from below and lift up the board  2  from the conveyors  33  (indicated by arrow A 1  in  FIG. 8A ). In this state, the control device  60  controls the clamper drive motor  36  so that the clampers  37  clamp and hold the board  2  (indicated by arrows B 1  in  FIG. 8A ). 
     When the board  2  has been held by the board holding unit  21 , the control device  60  controls the camera unit moving mechanism  19  to move the camera unit  20  and causes the upper field shooting camera  20   a  to shoot the mask-side marks  13   m . The upper field shooting camera  20   a  shoots the mask-side marks  13   m  of the first pattern-formed area R 1  if the board  2  is to be brought into contact with the first pattern-formed area R 1 , and shoots the mask-side marks  13   m  of the second pattern-formed area R 2  if the board  2  is to be brought into contact with the second pattern-formed area R 2 . When the mask-side marks  13   m  have been shot, the control device  60  causes the lower field shooting camera  20   b  to shoot the board-side marks  2   m.    
     When the mask-side marks  13   m  and the board-side marks  2   m  have been shot, the control device  60  controls the board holding/moving mechanism  12  on the basis of positions of the mask-side marks  13   m  and the board-side marks  2   m  obtained by the shooting so that it brings the board  2  into contact with the mask  13  in the manner described above (indicated by arrow C 1  in  FIG. 8B ). As a result, a state is established that the electrodes  2   a  of the board  2  are registered with the pattern (first pattern PT 1  or second pattern PT 2 ) of the mask  13  (see  FIG. 8B ). 
     When the board  2  has been brought into contact with the mask  13 , the control device  60  checks, using a paste amount checking device (not shown), whether a sufficient amount of paste Pst exists in the region Rm (where the front clamper  37 F or the rear clamper  37 R is in contact with the mask  13 ) located between the first pattern-formed area R 1  and the second pattern-formed area R 2 . If judging that a sufficient amount of paste Pst does not exist in the region Rm, the control device  60  causes the paste supply syringe  18  to supply paste Pst to the region Rm. 
     If judging that a sufficient amount of paste Pst exists in the region Rm between the first pattern-formed area R 1  and the second pattern-formed area R 2  (if paste Pst has just been supplied additionally from the paste supply syringe  18 , a resulting amount of paste Pst is checked), the control device  60  causes the squeegees  52  to squeegee the paste Pst. In the squeegeeing, the control device  60  controls the print head moving mechanism  16  so that it moves the movable base  51  in the Y-axis direction and thereby reciprocates the print head  17  across (i.e., slides the squeegees  52  on) the first pattern-formed area R 1  or the second pattern-formed area R 2 . As a result of the squeegeeing, the paste Pst is raked on the mask  13  and passes through the pattern of the mask  13 . A paste print is thus formed on the board  2 . 
     To form a paste print on the board  2  using the first pattern PT 1  by squeegeeing, first, the rear squeegee  52 R is lowered from over the region Rm between the first pattern-formed area R 1  and the second pattern-formed area R 2  until its bottom end comes into contact with the mask  13  in the region Rm where the rear clamper  37 R is in contact with the mask  13 . Then the rear squeegee  52 R is moved forward (indicated by arrow D 1  in  FIG. 9A ) with the above contact position (in the region Rm) as a movement start position. When the rear squeegee  52 R has reached a position over the front clamper  37 F as a result of sliding on the first pattern-formed area R 1  of the mask  13 , the rear squeegee  52 R is elevated and the front squeegee  52 F is lowered until its bottom end comes into contact with the mask  13  over the front clamper  37 F is in contact with the mask  13 . Then the front squeegee  52 F is moved backward (indicated by arrow D 2  in  FIG. 9B ) from the above contact position. When the front squeegee  52 F has returned to the movement start position over the rear clamper  37 R as a result of sliding on the first pattern-formed area R 1  of the mask  13 , the front squeegee  52 F is elevated and a standby state is established. 
     On the other hand, to form a paste print on the board  2  using the second pattern PT 2  by squeegeeing, first, the front squeegee  52 F is lowered from over the region Rm between the first pattern-formed area R 1  and the second pattern-formed area R 2  until its bottom end comes into contact with the mask  13  in the region Rm where the front clamper  37 F is in contact with the mask  13 . Then the front squeegee  52 F is moved backward (indicated by arrow D 3  in  FIG. 10A ) with the above contact position as a movement start position. When the front squeegee  52 F has reached a position over the rear clamper  37 R as a result of sliding on the second pattern-formed area R 2  of the mask  13 , the front squeegee  52 F is elevated and the rear squeegee  52 R is lowered until its bottom end comes into contact with the mask  13  over the rear clamper  37 R is in contact with the mask  13 . Then the rear squeegee  52 R is moved forward (indicated by arrow D 4  in  FIG. 10B ) from the above contact position. When the rear squeegee  52 R has returned to the movement position over the front clamper  37 F as a result of sliding on the second pattern-formed area R 2  of the mask  13 , the rear squeegee  52 R is elevated and a standby state is established. 
     As described above, in the screen printer  5  according to the first embodiment, when a print of paste Pst should be formed on a board  2  that is in contact with the first pattern-formed area R 1  using the first pattern PT 1 , the print head  17  is operated so as to reciprocate across the first pattern-formed area R 1  in the Y-axis direction, that is, to move from a movement start position that is a position in the region Rm between the first pattern-formed area R 1  and the second pattern-formed area R 2  on the mask  13  and return to the movement start position. When a print of paste Pst should be formed on a board  2  that is in contact with the second pattern-formed area R 2  using the second pattern PT 2 , the print head  17  is operated so as to reciprocate across the second pattern-formed area R 2  in the Y-axis direction, that is, to move from the above movement start position and return to the movement start position. 
     When a print of paste Pst has been formed on the board  2  by causing paste Pst to pass through the pattern of the mask  13  by reciprocating the squeegees  52 , the control device  60  controls the second elevation motor  42  so that it lowers the elevation plate  31  (indicated by arrow C 2  in  FIG. 11A ) and thereby separates the board  2  from the mask  13  (plate releasing; see  FIG. 11A ). Thus, the screen printing operation for the one board  2  is completed. 
     Upon completion of the screen printing of the one board  2 , the control device  60  controls the clamper drive motor  36  so that it opens the clampers  37  (indicated by arrows B 2  in  FIG. 11B ) and controls the first elevation motor  34  so that it lowers the support member  35  (indicated by arrow A 2  in  FIG. 11B ), whereby the board  2  is placed on the conveyors  33  (see  FIG. 11B ). Then, the control device  60  causes the carry-out conveyor  15  to be placed at a position opposing the board holding unit  21  (see  FIG. 7D ), and causes the conveyors  33  and the carry-out conveyor  15  to operate in link with each other so that the board  2  is carried out from the screen printer  5  to another, downstream machine (component mounter  6 ) (see  FIG. 7E ). When the board  2  has been carried out, the control device  60  judges whether there exists another board  2  to be subjected to screen printing. If judging that there exists another board  2  to be subjected to screen printing, the control device  60  has the other board  2  carried in using the carry-in conveyor  14 . If judging that there is no board  2  to be subjected to screen printing, the control device  60  finishes the process. 
     In the above-described screen printing operation, a print of paste Pst is formed on a board  2  as the print head  17  reciprocates across the first pattern-formed area R 1  or the second pattern-formed area R 2  starting from the movement start position that is in the region Rm between the first pattern-formed area R 1  and the second pattern-formed area R 2  on the mask  13 . Therefore, for example, paste Pst exits at the movement start position (i.e., the start position of a reciprocation) not only when a print of paste Pst is to be formed on another board  2  using the pattern PT 1  after a print of paste Pst has been formed on a board  2  but also when a print of paste Pst is to be formed on another board  2  using the pattern PT 2 . Therefore, wasteful use of the paste Pst on the mask  13  can be avoided and hence the amount of paste Pst that is discarded wastefully can be reduced. Furthermore, since the paste Pst on the mask  13  is returned to the region Rm between the first pattern-formed area R 1  and the second pattern-formed area R 2  on the mask  13  when a printing operation has been completed, printing operations can be started immediately even if different kinds of boards  2  are carried in in random order (i.e., a printing operation can be started immediately irrespective of whether a board  2  is brought into contact with the first pattern-formed area R 1  or the second pattern-formed area R 2 ). 
     As shown in  FIG. 1 , the component mounter  6  is a two-lane component mounter equipped with two board conveying lanes. The component mounter  6  is equipped with two board conveying lanes  72 , that is, a first board conveying lane  72   a  and a second board conveying lane  72   b , disposed on a stage  71 , plural parts feeders  73  as parts supply units, and two mounting heads  75  which is moved by a head moving mechanism  74  which is an XY robot. The first board conveying lane  72   a  receives, from the carry-out conveyor  15 , a board  2  on which a paste print has been formed by the screen printer  5  using the first pattern PT 1  and carries it in. The second board conveying lane  72   b  receives, from the carry-out conveyor  15 , a board  2  on which a paste print has been formed by the screen printer  5  using the second pattern PT 2  and carries it in. Each of the first board conveying lane  72   a  and the second board conveying lane  72   b  positions a board  2  that has been received from the screen printer  5  at a prescribed position. Each of the two mounting heads  75  picks up a component  3  supplied from the associated parts feeder  73  and mounts it on the board  2  that has been positioned by the associated one of the first board conveying lane  72   a  and the second board conveying lane  72   b . When the mounting of the component on the board  2  has been completed, the board conveying lane  72  that positioned the board  2  is operated, whereby the board  2  is carried out to the outside (a downstream machine). 
     As described above, in the screen printer  5  according to the first embodiment, a print of paste Pst is formed as the print head  17  reciprocates across the first pattern-formed area R 1  or the second pattern-formed area R 2  starting from the movement start position that is in the region Rm between the first pattern-formed area R 1  and the second pattern-formed area R 2  on the mask  13 . And the single print head  17  serves as both of a print head for printing with the first pattern PT 1  and printing with the second pattern PT 2 . This makes it possible to perform, in parallel, with a simple configuration, printing on plural kinds of boards  2  to accommodate the component mounter  6  on the downstream process side. Furthermore, since the print head  17  reciprocates, that is, moves from the movement start position that is in the region Rm between the first pattern-formed area R 1  and the second pattern-formed area R 2  and returns to the original position (movement start position), residual paste Pst can be used for the next printing irrespective of whether printing has been performed using the first pattern PT 1  or the second pattern PT 2 . Therefore, the amount of paste Pst wasted is reduced and hence the cost of printing operations can be reduced accordingly. Still further, since the paste Pst on the mask  13  is returned to the region Rm between the first pattern-formed area R 1  and the second pattern-formed area R 2  on the mask  13  when a printing operation has been completed, printing operations can be started immediately even if different kinds of boards are carried in in random order (i.e., a printing operation can be started immediately irrespective of whether a board  2  is brought into contact with the first pattern-formed area R 1  or the second pattern-formed area R 2 ). 
     In the screen printer  5  according to the first embodiment, the carry-in conveyor  14  (board carry-in unit) which receives a board  2  that has been conveyed from outside the screen printer  5  and transfers it to the board holding/moving mechanism  12  and the carry-out conveyor  15  (board carry-out unit) which receives a board  2  on which a print of paste Pst has been formed by the print head  17  from the screen printer  5  and carries it to outside the screen printer  5  are each disposed so as to be movable in the Y-axis direction (i.e., the arrangement direction of the first pattern-formed area R 1  and the second pattern-formed area R 2  in the screen printer  5 ). Therefore, it suffices to employ only one carry-in conveyor  14  and only one carry-out conveyor  15 , which also contributes to the simplification of the configuration. 
     Second Embodiment 
     Next, a second embodiment of the invention will be described.  FIG. 12  shows a component mounting line  101  according to the second embodiment of the invention. Similar to the component mounting line  1  according to the first embodiment, the component mounting line  101  includes a screen printer  105  and a component mounter  106 . In  FIGS. 12 and 13 , constituent elements of the screen printer  105  having the same ones in the screen printer  5  according to the first embodiment are given the same reference symbols as the latter. In  FIG. 12 , constituent elements of the component mounter  106  having the same ones in the component mounter  6  used in the first embodiment are given the same reference symbols as the latter. 
     The screen printer  105  according to the second embodiment is configured basically in the same manner as the screen printer  5  according to the first embodiment, and different from the latter in the following points. In the screen printer  105  according to the second embodiment, the board holding unit  21  can be placed at an intermediate position (see  FIG. 14C ) between the first position (see  FIG. 14A ) located under the first pattern-formed area R 1  and the second position (see  FIG. 14B ) located under the second pattern-formed area R 2 , as well as at the first position and the second position. The board holding unit  21  receives a board  2  from the carry-in conveyor  14  at the intermediate position. The board  2  is then clamped by the clampers  37  and moved to the first position or the second position, where the board  2  is brought into contact with the mask  13 . 
     As shown in  FIG. 12 , the component mounter  106  used in the second embodiment is a one-lane component mounter which is equipped with only one board conveying lane  172  which is disposed at a position corresponding to the intermediate position of the screen printer  105 . Therefore, as shown in  FIG. 13 , the carry-out conveyor  15  is fixed at a position corresponding to the intermediate position. Irrespective of whether screen printing has been performed at the first position or the second position, the board holding unit  21  is necessarily moved to the intermediate position and transfers the board  2  to the carry-out conveyor  15 . The carry-out conveyor  15  carries out the board  2  received from the board holding unit  21  to the board conveying lane  172  of the component mounter  106 . The component mounter  106  carries in the board  2  with the board conveying lane  172  and mounts a component  3  on the board  2  by means of the mounting heads  75 . 
     As described above, in the screen printer  105  according to the second embodiment, the board holding unit  21  can be moved selectively to the first position corresponding to the first pattern-formed area R 1 , the second position corresponding to the second pattern-formed area R 2 , or the intermediate position which is located between the first position and the second position and serves as a board reception/output position where a board  2  is received from the carry-in conveyor  14  (board carry-in unit) and transferred to the carry-out conveyor  15  (board carry-out unit). 
     Next, a procedure according which the screen printer  105  performs a screen printing operation will be described with reference to  FIGS. 15A-15F . When a board  2  is to be output from one of the two board supply units  4 , the control device  60  causes the carry-in conveyor  14  to be moved to such a position as to be opposed to the board supply unit  4  that is going to output the board  2  (see  FIG. 15A ). The control device  60  causes the carry-in conveyor  14  which has received the board  2  to such a position as to be opposed to the board holding unit  21  located at the intermediate position (see  FIG. 15B ), causes the board  2  to be carried in to the board holding unit  21  by having the carry-in conveyor  14  and the conveyors  33  of the board holding unit  21  (located at the intermediate position) to operate in link with each other (see  FIG. 15C ), and causes the board  2  to be positioned at the clamping position and clamped (held) by the clampers  37 . 
     When the board  2  has been held by the board holding unit  21 , the control device  60  causes the board holding unit  21  to be moved to the first position or the second position (see  FIG. 15D ). Then the control device  60  causes the board  2  to be brought into contact with the mask  13  according to the same procedure as in the first embodiment through shooting of the mask-side marks  13   m  and the board-side marks  2   m  by the camera unit  20 .  FIG. 15D  shows a state that the board holding unit  21  is placed at the second position. 
     When the board  2  has been brought into contact with the mask  13 , the control device  60  causes squeegeeing of paste Pst using the print head  17 . In the screen printer  105  according to the second embodiment, as in the screen printer  5  according to the first embodiment, the print head  17  is operated in the following manner. To form a print of paste Pst on the board  2  being in contact with the first pattern-formed area R 1  using the first pattern PT 1 , the print head  17  starts from a movement start position which is a position in the region Rm located on the mask  13  between the first pattern-formed area R 1  and the second pattern-formed area R 2 , reciprocates across the first pattern-formed area R 1  in the Y-axis direction, and returns to the movement start position (see  FIGS. 9A and 9B ). On the other hand, to form a print of paste Pst on the board  2  being in contact with the second pattern-formed area R 2  using the second pattern PT 2 , the print head  17  starts from a movement start position which is a position in a region Rm located on the mask  13  between the first pattern-formed area R 1  and the second pattern-formed area R 2 , reciprocates across the second pattern-formed area R 2  in the Y-axis direction, and returns to the movement start position (see  FIGS. 10A and 10B ). 
     When a print of paste Pst has been formed on the board  2  by causing paste Pst to pass through the pattern of the mask  13 , the control device  60  causes the board  2  to be separated from the mask  13  (plate releasing) according to the same procedure as in the first embodiment and causes the board holding unit  21  to be moved to the intermediate position (see  FIG. 15E ). Then the control device  60  causes the board  2  to be placed on the conveyors  33 , causes the board  2  to be transferred to the carry-out conveyor  15  by having the conveyors  33  and the carry-out conveyor  15  to operate in link with each other (see  FIG. 15F ), and causes the carry-out conveyor  15  to carry out the board  2  to the board conveying lane  172 , according to the same procedure as in the first embodiment. 
     The component mounter  106  receives (takes in) a board  2  on which printing has been performed by the screen printer  105  using the first pattern PT 1  or the second pattern PT 2 , from the carry-out conveyor  15  by means of the board conveying lane  172 . The board conveying lane  172  positions the received board  2  at a prescribed position. Each of the two mounting heads  75  picks up a component  3  which is supplied by the parts feeders  73  and mounts the component  3  on the board  2  which has been positioned by the board conveying lane  172 . In this operation, a control device (not shown) of the component mounter  106  judges a kind of the received board  2  (i.e., whether printing has been performed on it using the first pattern PT 1  or the second pattern PT 2 ) and causes the mounting heads  75  to mount a component  3  that is suitable for the kind of the received board  2  (board-mixed mounting). Upon completion of the mounting of the component  3  on the board  2 , the control unit activates the board conveying lane  172  to carry out the board  2  to the outside (a downstream process). 
     As described above, also in the screen printer  105  according to the second embodiment, the print head  17  forms a print of paste Pst on the board  2  by starting from the movement start position in the region Rm which is located between the first pattern-formed area R 1  and the second pattern-formed area R 2  and reciprocates across the first pattern-formed area R 1  or the second pattern-formed area R 2 . That is, the single print head  17  serves as both of a print head for printing using the first pattern PT 1  and a print head for printing using the second pattern PT 2 . As such, the screen printer  105  according to the second embodiment provides the same advantage as that of the component mounting line  101  according to the first embodiment, in which parallel printing on plural kinds of boards that are compatible with the component mounter  106  installed downstream can be realized with a simple configuration. 
     Furthermore, since the print head  17  reciprocates, that is, starts from the movement start position in the region Rm which is located between the first pattern-formed area R 1  and the second pattern-formed area R 2  and returns to the original position (movement start position), residual paste Pst can be used for the next printing irrespective of whether printing has been performed using the first pattern PT 1  or the second pattern PT 2 . Therefore, the amount of paste Pst wasted is reduced and hence the cost of printing operations can be reduced accordingly, which is also the same advantage as provided by the component mounting line  101  according to the first embodiment. Still further, since the paste Pst on the mask  13  is returned to the region Rm which is located between the first pattern-formed area R 1  and the second pattern-formed area R 2  on the mask  13  when a printing operation has been completed, printing operations can be started immediately even if different kinds of boards are carried in in random order (i.e. a printing operation can be started immediately irrespective of whether a board  2  is brought into contact with the first pattern-formed area R 1  or the second pattern-formed area R 2 ). This is also the same advantage as provided by the component mounting line  101  according to the first embodiment. 
     The two-lane component mounter  6  used in the first embodiment can increase the board manufacturing efficiency of the component mounting line  1  as a whole because component mounting is performed independently in the two lanes. On the other hand, the component mounter  106  according to the second embodiment allows the component mounting line  101  as a whole to perform low-cost board manufacture that is suitable for manufacture of boards in small numbers and space saving because the one-lane component mounter  106  performs board-mixed mounting in the single lane. It becomes possible to accommodate various board manufacturing modes as mentioned above by determining whether to use a two-lane component mounter or a one-lane component mounter and use the screen printer  5  according to the first embodiment and the screen printer  105  according to the second embodiment while selecting between them properly. 
     The embodiments of the invention provides a screen printer and a component mounting line which can perform printing operations on plural kinds of boards in parallel with a simple configuration while enabling reduction of the amount of paste wasted.