JP4873093B2 - Screen printing device - Google Patents

Description

  The present invention relates to a screen printing apparatus, and more particularly to a screen printing apparatus in which a workpiece is superimposed on the lower surface of a screen to print a paste-like substance on the surface of the workpiece.

  When assembling an electronic circuit device, the electronic component is mounted on a circuit board. Here, a substrate made of an insulating material is used as the circuit substrate. A copper foil is bonded to the surface of the substrate, and a predetermined wiring pattern is formed by etching. Then, an electronic component is mounted thereon, and the electrodes and terminals of the electronic component are soldered to the connection lands of the circuit board wiring pattern.

  Cream solder is used for soldering the electrodes of the electronic components and the circuit board connection lands as described above. That is, the cream solder is printed and attached to a predetermined position on the surface of the circuit board on which the wiring is provided by a screen printing method. And it mounts in the state which positioned the electronic component on it. Then, the circuit board on which the electronic components are mounted is gently introduced into the reflow furnace. The cream solder is melted by the heat in the reflow furnace, whereby the electrodes of the electronic components are soldered to the connection lands on the circuit board. Therefore, when manufacturing an electronic circuit, a screen printing apparatus for applying cream solder on a circuit board by a screen printing method is required.

  In general, the screen printing apparatus is an apparatus for printing cream solder on a land of a substrate through a pattern made of holes provided in a screen, and requires the following units. That is, a squeegee unit for pushing the cream solder into the screen pattern, a cleaning unit for cleaning the cream solder remaining on the back side of the screen and the pattern, a camera unit for detecting the alignment mark provided on the substrate and recognizing the position of the substrate, It is composed of a positioning table or the like that fixes a substrate on which the printing is performed and positions each of the X axis direction, the Y axis direction, the Z axis direction, and the θ axis direction. The present application relates to an improvement of such a solder paste printer.

Japanese Patent Laid-Open No. Hei 4-236487 JP-A-5-185580

  In such a screen printing apparatus, after the positioning table rises and the substrate comes into close contact with the back surface of the screen, the squeegee slides on the screen and pushes the cream solder through the pattern formed on the screen, thereby the cream solder on the substrate. Print. The squeegee that has moved a predetermined distance through the portion of the screen where the plurality of holes are formed starts to rise after stopping. However, when the squeegee rises, a force that pulls the screen upward acts due to the viscosity of the cream solder. Therefore, when the squeegee is raised, the screen moves up and down and vibrates.

  Further, even when the substrate after printing is separated from the screen, so-called plate separation, a force that pulls the screen downward acts due to the viscosity generated between the cream solder in the holes of the screen and the side surfaces of the holes. Therefore, the screen is deformed downward by this force. Such relative movement between the substrate and the screen causes a decrease in printing accuracy such as misalignment, chipping, cracking, and deformation of the cream solder printed on the substrate pattern. As described above, in the conventional screen printing apparatus, when the squeegee is lifted or the plate is removed from the substrate, the force acting due to the viscosity of the cream solder deforms the screen, which causes a problem that the printing accuracy is lowered. .

  The invention of the present application has been made in view of such problems, and printing is performed by eliminating the deformation and vibration of the screen that occurs when the squeegee is lifted from the screen or when the work is separated from the screen. It is an object of the present invention to provide a screen printing apparatus in which accuracy is improved.

  A main invention of the present application is a screen printing apparatus in which a workpiece is superimposed on a lower surface of a screen and a paste-like substance is printed on the surface of the workpiece, and the workpiece can be moved up and down so as to overlap the lower surface of the screen. A positioning unit; a squeegee that moves on the screen to print the paste-like substance; and guides that are perpendicular to the moving direction of the squeegee and are located on both sides of the positioning unit. In a finished state, the squeegee stops at a position off the work on the screen, and the printing pressure of the squeegee at that time is received by guides on both sides, and the work is separated from the screen by the positioning unit. The squeegee is raised later.

  Here, the surface of the workpiece may be set slightly higher than the upper surfaces of the guides on both sides. The surface of the workpiece may be set higher by 0.03 to 1.0 mm than the upper surfaces of the guides on both sides. Further, the downward deformation of the screen when the work is lowered by the positioning unit may be restricted by the guides on both sides. Further, one of guides positioned on both sides of the positioning unit in a direction perpendicular to the moving direction of the squeegee may be movable with respect to the other, and the work may be clamped from both sides.

  In a preferred embodiment of the invention included in the present application, the squeegee that has slid on the screen is separated from the substrate located under the screen in the configuration related to the order of the separating operation of the squeegee and the substrate with respect to the screen at the end of printing. At this time, the printing pressure of the squeegee is received by the guides of the two substrates that respectively guide the both ends in the width direction of the substrate, and then the substrate descends with respect to the screen to cause separation of the plate. Immediately after the substrate starts to move downward, the screen is deformed downward by the guides on both sides of the substrate, so that the cream solder printed on the land of the substrate leaves the screen, that is, from the hole of the screen. This is a cream solder printing device that allows the squeegee to rise after the cream solder is completely removed from the pattern.

  The workpiece may be a circuit board. The pasty substance may be cream solder.

  In the above aspect, after the squeegee slides and performs printing, the substrate leaves the screen in a state where the squeegee stops without rising at a position away from the substrate. At this time, the printing pressure of the squeegee is applied to both sides. The screen is also received by the guide, and the deformation of the screen is also received by the guide, so that the substrate can be separated while maintaining a parallel posture with respect to the screen, thereby enabling high-precision printing without printing misalignment. .

  According to the main invention of the present application, since the squeegee stops at a position away from the work after the printing accompanying the movement of the squeegee is completed, and the printing pressure of the squeegee at that time is received by the guides on both sides, the work is The screen is prevented from being deformed when the plate is separated from the screen, and the paste-like substance printed on the work is prevented from shifting during the separation.

It is a front view which shows the whole structure of a screen printing apparatus. It is a side view of the screen printing apparatus. It is a front view which shows the fundamental structure of a screen printing apparatus. It is the same side view. It is a front view which shows the structure of the positioning unit of a board | substrate. It is a front view which shows the same principle structure. It is a side view which shows the structure for correction | amendment of the curvature of a board | substrate. It is a front view which shows the operation | movement of correction | amendment of the curvature of a board | substrate. It is the same side view. It is a principal part front view of the state which finished printing. It is the principal part side view. It is a side view which shows the operation | movement of carrying in and positioning of the board | substrate to the lower side of a screen. It is a top view of a board | substrate. It is a front view which shows the image recognition of a board | substrate. It is a disassembled perspective view which shows the support structure of a squeegee. It is the principal part front view. It is the principal part side sectional drawing.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 and 2 show a front view and a side view of the screen printing apparatus, and FIGS. 3 and 4 show a front view and a side view showing the principle of such an apparatus. The outline of the screen printing apparatus will be described with reference to these drawings.

  The screen printing apparatus includes a support base 10 that stands upright on the back side. On the support base 10, there are guide rails 11, 12 extending in the vertical direction on the lower front surface with a predetermined interval therebetween, and the carriage 13 can be moved by these guide rails 11, 12. I support it. The carriage 13 supports a camera unit 14, and the image recognition camera 15 is supported by the camera unit 14. The image recognition camera 15 is for performing image recognition of a substrate to be described later.

  A further carriage 18 is supported by the pair of guide rails 11 and 12. A cleaning unit 19 is supported on the carriage 18. The cleaning unit 19 is for cleaning the lower surface of the screen, which will be described later, with a cleaning tape 20 as shown in FIG. The cleaning tape 20 is fed from the feed roller 21 of the cleaning unit 19, and the cleaning tape 20 that has finished cleaning is taken up by the take-up roller 22.

  A screen 25 is disposed above the movement range of the camera unit 14 and the cleaning unit 19. The screen 25 is stretched in a state where its four sides are fixed by a frame body 26. The frame body 26 is fixed to a predetermined position of the printing apparatus by the mounting frame 27.

  A pair of squeegees 31 and 32 are disposed on the screen 25. The squeegees 31 and 32 are supported by support bodies 33 and 34, respectively, and the support bodies 33 and 34 are supported by air cylinders 35 and 36, respectively.

  A pair of laterally extending guide rails 37, 38 are arranged on the upper surface side of the support base 10, and a carriage 39 is movably supported by these guide rails 37, 38. Yes. The carriage 39 moves the squeegees 31 and 32 in the lateral direction.

  Next, a positioning device for positioning the substrate constituting the workpiece on the lower side of the screen 25 will be described. FIG. 5 shows a specific configuration of the positioning device, and FIG. 6 shows its principle diagram. As shown in FIGS. 5 and 6, this apparatus includes a base 43, and four Z-axis guides 44 are provided upright on the base 43. The lower Z-axis table 45 is supported by the Z-axis guide 44 so as to be movable in the Z-axis direction, that is, the vertical direction. The Z-axis table 45 is pushed up by a rod 47 of an air cylinder 46 attached to the lower side of the base 43 and is moved up and down by a Z-axis guide 44. The upper movement position is restricted by a stopper 48 provided on the Z-axis guide 44.

  A Y-axis table 51 is mounted on the Z-axis table 45, and an X-axis table 52 is mounted on the Y-axis table 51. A θ-axis table 53 is mounted on the X-axis table 52. A mounting plate 54 is mounted on the θ-axis table 53.

  Four Z-axis guides 55 are arranged on the mounting plate 54 so as to extend upward, and the Z-axis table 56 is supported by these guides 55 so as to be movable up and down. The motor (not shown) and the ball screw 58 of the Z-axis table 56 are interlocked with each other so that the Z-axis table 56 is moved up and down. A substrate mounting jig 60 is mounted on the Z-axis table 56, and the substrate 61 is sucked and held by the substrate mounting jig 60. As a result, the positioning unit 50 of the substrate 61 is disposed below the screen 25.

  Next, the mechanism for holding the substrate 61 provided on the mounting plate 54 will be described. On the mounting plate 54, supports 65 and 66 are provided on both sides thereof. A fixed guide 67 is fixed to the upper end of the left support 65 as shown in FIG. On the other hand, a movement guide 69 is attached to the upper end of the right support 66 via a base 68. Further, the conveyor belt 70 is supported by these guides 67 and 69.

  As shown in FIGS. 6 and 11, the support members 65 and 66 are provided with arms 73 and 74 that extend laterally, respectively, and presser claws 77 are provided on these arms 73 and 74 via support members 75 and 76. , 78 are provided. As will be described later, these presser claws 77 and 78 are configured to press both sides in the width direction of the substrate 61 introduced onto the positioning device from above.

  As shown in FIG. 5, a carry-in conveyor 81 and a discharge conveyor 82 are disposed on the upstream side and the downstream side of the conveyor belt 70 supported by the fixed guide 67 and the moving guide 69, respectively. 70, the substrate 61 is introduced onto the substrate mounting jig 60 of the positioning unit 50, and is discharged by the discharge conveyor 82 after the printing is finished.

  As shown in FIG. 7, a cylinder 85 is attached to the lower part of the camera unit 14 including the image recognition camera 15 so as to face downward. The rod of the cylinder 85 constitutes a correction pin 86, and as shown in FIGS. 10 and 11, the central portion of the upper surface of the substrate 61 placed on the substrate mounting jig 60 is formed by the correction pin 86. The warp of the substrate 61 is corrected by pressing.

  As described above, the screen printing apparatus of the present embodiment includes the screen 25 and is fixed by the mounting frame 27 via the frame body 26. A substrate 61 is disposed immediately below the screen 25 and is fixed by a substrate mounting jig 60 mounted on a positioning unit 50 that can move in the X-axis direction, the Y-axis direction, the Z-axis direction, and the θ-axis direction. (See FIGS. 1 and 3).

  As shown in FIGS. 1 to 4, a camera unit 14 is attached to the carriage 13, and an image recognition camera 15 is mounted on the camera unit 14. Although the carriage 13 is not shown here, it is configured to be driven via a servo motor and a ball screw. The carriage 13 is supported on a support base 10 by a pair of upper and lower guide rails 11 and 12 extending in the lateral direction. With such a configuration, space saving and rigidity are improved.

  In addition, the guide rails 11 and 12 guide the carriage 18 on which the cleaning unit 19 is mounted. That is, here, the guide rail of the carriage 18 of the cleaning unit 19 is shared with the guide rails 11 and 12 of the camera unit 14.

  On the screen 25, a squeegee unit including squeegees 31 and 32 is disposed. That is, it has a pair of squeegees 31 and 32, and each can be moved up and down by air cylinders 35 and 36 separately. These squeegees 31 and 32 are mounted on a carriage 39, and the carriage 39 is moved by a motor and a ball screw (not shown). The guide mechanism for moving the carriage 39 is two upper and lower guide rails 37 provided on the support base 10 and extending in the horizontal direction, and has the same configuration as the guide mechanism of the camera unit 14.

  As shown in FIGS. 5 and 6, the positioning unit 50 arranged on the lower side of the screen 25 and positioning the substrate 61 is configured to carry the substrate 61 thereon by a carry-in conveyor 81. 5 and 6 show a state in which the substrate 61 is carried and placed on the substrate mounting jig 60. FIG. The substrate 61 carried in by the carry-in conveyor 81 is delivered by the conveyor belt 70 and stopped on the substrate mounting jig 60 by a stopper (not shown).

  The board mounting jig 60 is mounted on the upper Z-axis table 56, and is guided by the four Z-axis guides 55 so as to be movable in the Z-axis direction. A ball screw 58 and a motor (not shown) are provided for moving the Z-axis table 56, thereby constituting an elevating mechanism for the upper Z-axis table 56.

  A mounting plate 54 that supports the Z-axis guide 55 is mounted on a θ-axis table 53, and this table 53 moves in the rotational direction. Here, the driving device for the θ-axis table 53 is not shown, but it may be constituted by, for example, a cylinder or a motor provided with a rotating shaft or a rotating table with a driving device. An X-axis table 52 is disposed below the X-axis table 52 and is moved by a drive mechanism using a motor and a ball screw so as to be movable in the X-axis direction. A Y-axis table 51 is disposed on the lower side, and a drive mechanism using a motor and a ball screw is provided so as to be movable in the Y-axis direction.

  A Z-axis table 45 is arranged below the Y-axis table 51 and guided in the Z-axis direction by four guide shafts 44. On the table 45, the Y-axis table 51, the X-axis table 52, θ The shaft table 53 and the Z-axis table 56 are all movable in the Z-axis direction. The lower Z-axis table 45 is driven by a cylinder 46 to move up and down.

  With the configuration as described above, the positioning unit 50 as a whole can move in the X-axis, Y-axis, Z-axis, and θ-axis directions, and the Z-axis direction includes two axes. This constitutes a 5-axis positioning unit 50.

  In particular, the screen printing apparatus of the present embodiment employs a configuration in which the uppermost Z-axis table 56 is driven by a motor (not shown) and a ball screw 58, and the lower Z-axis table 45 is driven by a cylinder 46. Therefore, the positioning unit 50 that is compact and has high rigidity can be obtained.

  The substrate 61 introduced onto the substrate mounting jig 60 of the positioning unit 50 is positioned directly below the screen 25 and is regulated by guides 67 and 69 from both sides in the width direction. . These guides 67 and 69 support the conveyor belt 70, and the conveyor belt 70 is positioned below both ends of the substrate 61 to be introduced. And press claws 77 and 78 are arranged on both sides of the guides 67 and 69, respectively. These presser claws 77 and 78 are for pressing both ends of the substrate 61 in the width direction from above.

  When the positioning unit 50 on which the substrate 61 is placed is raised, the substrate 61 is pressed against the lower surface of the screen 25 as shown in FIG. Here, the right guide 69 is configured to be movable in the width direction of the substrate 61, and the substrate 61 is pressed against and fixed to the fixed guide 67 on the opposite side. The guides 67 and 69 on both sides are mounted on a mounting plate 54 on the θ-axis table 53. Here, a conveyor belt 70 is provided on the guides 67 and 69. These conveyor belts 70 have a guide composed of a plurality of rollers, and are conveyor belts driven by a motor. Such a conveyor belt 70 is attached to the lower surfaces of the guides 67 and 69 on both sides.

  The substrate mounting jig 60 for mounting and holding the substrate 61 is provided with a number of vacuum suction holes on the surface. The substrate mounting jig 60 is mounted on the upper Z-axis table 56.

  When the squeegees 31 and 32 shown in FIG. 10 are moved in such a state that the substrate 61 is pressure-bonded to the lower surface of the screen 25 as described above, a printing operation is performed. That is, when the squeegees 31 and 32 slide on the screen 25, the cream solder is stirred and printing is performed. Here, a pair of squeegees 31 and 32 is provided, and the two substrates 61 are printed by alternately using the two squeegees 31 and 32 by reciprocation.

  Prior to such printing, the warpage of the substrate 61 is corrected by the mechanism shown in FIG. In FIG. 7, the screen 25 is fixed to the main body via a frame body 26. Then, the substrate 61 is introduced below the screen 25 by the conveyors 81 and 70. An air cylinder 85 including a warp correction pin 86 for correcting the warp of the substrate 61 is attached to the camera unit 14 together with the image recognition camera 15 and supported by the carriage 13 so as to be rotatable in the X-axis direction. Yes.

  Pressing claws 77 and 78 for pressing the substrate 61 shown in FIG. 7 from the upper portions on both sides thereof are located on both sides of the conveyor belt 70, and are rotatably supported via hinges 91 and 92. The fixed sides of the presser claws 77 and 78 are supported by sliding plates 95 and 96 that are movable in the Y-axis direction, respectively. The presser claws 77 and 78 are pressed in the closing direction, that is, downward by a tension spring, and are opened and closed by air cylinders 93 and 94.

  The lower sliding plate 95 of the left presser claw 77 is supported by the mounting plate 54 of the positioning unit 50 via the support 66. On the other hand, the lower sliding plate 96 of the right claw 78 is supported by the support 66, and this support 66 is supported on the sliding plate 98 movable in the Y-axis direction.

  Next, the support structure of the squeegees 31 and 32 that slide on the screen 25 and print cream solder will be described. As shown in FIGS. 15 to 17, the squeegee 31 is attached to the support 33 via a connecting bracket 106 and a squeegee holder 107. The squeegee 31 attached to the squeegee holder 107 is pressed by the pressing plate 108 from the opposite side.

  Small locking notches 111 are formed on the lower end side of the support 33 and on both sides in the width direction. Further, a concave portion 112 is formed on the lower end side of the support body 33 at a substantially central portion in the width direction. Further, a pair of female screw holes 113 are formed on the lower end side of the support 33 and on the front side thereof so as to be positioned on both sides of the recess 112.

  On the other hand, the connecting bracket 106 has an insertion hole 116 on its upper surface, and hook levers 117 are arranged on both sides of the insertion hole 116, respectively. The hook lever 117 has a claw 118 at its tip, and the claw 118 is locked to the locking notch 111 of the support 33.

  Further, the connecting bracket 106 has a pair of notches 119 on the front side thereof, and a final fastening screw 120 that passes through these notches 119 is screwed into the female screw hole 113 of the support 33. Thus, the connecting bracket 106 is fixed in a state of being connected to the lower end of the support 33.

  The squeegee holder 107 includes a protrusion 123 protruding upward at an intermediate position in the length direction, that is, a position corresponding to an intermediate portion in the width direction of the squeegee 31, and an insertion hole 124 is formed in the protrusion 123. An insertion hole 125 is formed in the coupling bracket 106 corresponding to the insertion hole 124. The pin 126 is assembled so that these insertion holes 124 and 125 may be inserted. A ball bearing 127 is interposed between the pin 126 and the insertion hole 125 of the connecting bracket 106. An equalizing mechanism for the squeegee 31 attached to the squeegee holder 107 is achieved by such a rotating mechanism. Note that end plates 130 made of synthetic resin are fixed to both ends of the squeegee holder 107 in the length direction.

  Next, the operation of the screen printing apparatus having such a configuration will be described. First, the overall outline of the operation of this printing apparatus will be described. When the substrate 61 does not exist on the conveyor belt 70 shown in FIG. 5, the Y-axis table 51 and the X-axis table 52 of the positioning unit 50 operate. The upper part of the positioning unit 50 moves to the carry-in conveyor 81 side. Then, the carry-in conveyor 81 and the conveyor belt 70 are operated to introduce the substrate 61 onto the conveyor belt 70 and stop at a predetermined position, and the conveyor 70 also stops. FIG. 5 shows a state in which the substrate 61 is stopped at this position.

  Next, the upper Z-axis table 56 is raised by a motor and a ball screw 58 (not shown) to lift the substrate 61 from the conveyor 70. Thereafter, the substrate 61 is fixed and the warp is corrected. These operations will be described later. After correcting the warp of the substrate 61 and fixing the substrate 61 to the substrate mounting jig 60 of the positioning unit 50, the camera unit 14 is moved along the guide rails 11 and 12 by the carriage 13, and the image recognition camera 15 is moved to the substrate 61. The alignment mark on the substrate 61 is recognized.

  In conjunction with such detection of the alignment mark on the substrate 61 by the image recognition camera 15, the control unit drives the X-axis table 52, the Y-axis table 51, and the θ-axis table 53 to correct the positional deviation of the substrate 61. Thereafter, the air cylinder 46 is actuated to raise the entire positioning unit 50 and move it upward to a position where the substrate 61 contacts the lower surface of the screen 25.

In this state, the squeegees 31 and 32 slide on the screen 25 to print cream solder. After a series of printing operations is completed, the upper Z-axis table 56 is moved downward by the ball screw 58, whereby the substrate 61 is released from the screen 25. Thereafter, the lower Z-axis table 45 is lowered by the air cylinder 46. Next, the suction fixing of the substrate 61 by the substrate mounting jig 60 is released. Thereafter, the X-axis table 52 and the Y-axis table 51 are driven, the positioning unit 50 is moved to the discharge conveyor 82 side, the conveyor belt 70 and the discharge conveyor 82 are moved together, and the substrate 61 is moved by the discharge conveyor 82. Discharge.

  When performing the printing operation as described above, the substrate 61 is fixed on the positioning unit 50, and the warp of the substrate 61 is corrected to perform clamping. This operation will be described with reference to FIG. In FIG. 12A, the substrate 61 is introduced by the conveyor 70 to a position almost directly below the screen 25. That is, the substrate 61 is moved to the lower side of the screen by the belts 70 on both sides. At this time, guides 67 and 68 are positioned on both sides of the substrate 61, respectively. The conveyor belt 70 is supported by these guides 67 and 68. In addition, press claws 77 and 78 are positioned outside the guides 67 and 68, respectively.

  Here, FIG. 12A shows a state in which the substrate 61 is carried into the printing apparatus, and thereafter various operations before printing are sequentially performed. In FIG. 12B, the right guide 68 advances to the left, and the substrate 61 on the belt 70 is clamped from the left and right directions so as to press against the guide 67 on the opposite side of the substrate 61. At this time, the presser claw 78 advances in the same direction.

  Next, as shown in FIG. 12C, the presser claws 77 and 78 on both sides rise, and then move in the width direction of the substrate 61 so as to be close to each other, thereby moving to the upper positions at both ends of the substrate 61. At that position, the presser claws 77 and 78 are stopped. Next, as shown in FIG. 12D, the board mounting jig 60 is raised and presses the presser claws 77, 78 waiting on the upper side of the upper surface of the board 61 on both sides. After this, the upper Z-axis table 56 rises. Immediately after this operation, the substrate mounting jig 60 fixes the substrate 61 by vacuum suction.

  Next, as shown in FIG. 12E, the presser claws 77 and 78 on both sides are temporarily moved upward and then moved to the side, and then lowered to release the restraint of the substrate 61 by these presser claws 77 and 78. In this state, the camera unit 14 is introduced between the substrate 61 and the screen 25, and the alignment mark on the substrate 61 is recognized by the image recognition camera 15. In addition, the camera unit 14 is provided with an air cylinder 85 having a correction pin 86 as shown in FIG. 7, and the air cylinder 85 is operated to move a predetermined position of the substrate 61 downward by the correction pin 86. By pressing, the warp of the substrate 61 is corrected, and the adhesion to the substrate mounting jig 60 is improved.

  In general, the substrate 61 introduced into the printing apparatus often has a warp. If the cream solder is printed as it is on the substrate 61 with warping, accurate printing is difficult. Further, the pattern holes of the screen 25 and the lands of the substrate 61 cannot be accurately aligned at the time of plate alignment. If there is warping, the substrate 61 moves in the X-axis direction or the Y-axis direction with respect to the screen 25 when the plate is separated, causing the cream solder printed on the land of the substrate 61 to shift, drop, or crack. Easy to cause problems.

  However, such a problem is solved by correcting the warp of the substrate 61 as described above. Thereafter, the position of the substrate 61 is corrected by the positioning unit 50 moving in the X-axis direction, the Y-axis direction, and the θ-axis direction. Thereafter, as shown in FIG. 12F, the lowermost Z-axis table 45 is moved upward by the cylinder 46, and the substrate 61 is brought into close contact with the lower surface of the screen 25 to perform printing.

  Next, the image recognition operation of the substrate 61 performed prior to printing will be described. In FIG. 14, the screen 25 is fixedly disposed via the attachment frame 27 in a state where the screen 25 is stretched on the frame body 26. And the squeegee 31 is arranged so that it may move on this. Here, the substrate 61 on which image recognition is performed is introduced below the screen 25 in a state of being fixed to the substrate mounting jig 60 of the positioning unit 50. That is, the substrate 61 carried into the printing apparatus is fixed to the substrate mounting jig 60 and positioned at a position almost directly below the screen 25.

  Here, in order to perform high-precision printing, the image recognition camera 15 needs to recognize an image of two alignment marks on the substrate 61. The alignment marks are provided at positions separated from each other on the diagonal lines on the surface of the substrate. For this purpose, the image recognition camera 15 is moved in the X-axis direction and the Y-axis direction before printing to recognize the alignment marks. Do.

  Here, the data fetched from the camera 15 is processed, and position correction amounts of the substrate 61 relative to the screen 25 in the X-axis direction, Y-axis direction, and θ-axis direction are calculated. The position correction amount data is taken into the control device and processed, whereby the X-axis table 52, Y-axis table 51, and θ-axis table 53 of the positioning unit 50 are operated to correct the substrate 61. As a result, the substrate 61 is moved to an accurate position with respect to the screen 25.

  In particular, the screen printing apparatus according to the present embodiment is characterized in that an image recognition camera is provided between the screen 25 and the substrate 61 with respect to the substrate 61 almost directly below the screen 25 as shown in FIGS. 15 is moved by the carriage 13 in the X-axis direction and the Y-axis direction to recognize the alignment mark on the substrate 61.

  As a result, compared with the case where the camera 15 or the substrate 61 is moved at a position away from the screen 25 in the horizontal direction to recognize the alignment mark on the substrate 61, the space in the horizontal plane direction is greatly reduced. It becomes possible to realize a significant downsizing of the printing apparatus. Further, since the moving amount is small, the positioning unit 50 can be downsized at the same time.

  As described above, in the screen printing apparatus of the present embodiment, the image recognition camera 15 is in a state in which the substrate 61 carried into the apparatus is fixed on the substrate mounting jig 60 of the positioning unit 50 after a predetermined operation. The alignment mark set in advance on the substrate 61 is recognized by moving in the X-axis direction and the Y-axis direction. Thereafter, the camera unit 14 having the image recognition camera 15 returns to the right position shown in FIGS. 1 and 3, that is, the origin position and stops so as not to interfere when the positioning unit 50 is raised.

  In this way, the deviation between the pattern provided on the screen 25 and the land provided on the substrate 61 by image recognition is calculated in the three directions of the X-axis direction, the Y-axis direction, and the θ-axis direction. Then, the positioning unit 50 moves in the X-axis direction, the Y-axis direction, and the θ-axis direction by the calculated deviation amount, thereby correcting the positional deviation. After this, the positioning unit 50 further moves up and stops at the position where the substrate 61 contacts the lower surface of the screen 25. Thereafter, the squeegees 31 and 32 slide on the screen 25, and the cream solder is printed on the substrate 61.

  In this manner, the squeegees 31 and 32 slide on the screen 25 in a state where the upper surface of the substrate 61 is pressed against the lower surface of the screen 25, whereby the cream solder is printed on the substrate 61. Thereafter, the squeegee 31 stops at a position deviated to the right from the substrate 61 as shown in FIG. The squeegee 31 applies an appropriate printing force to the screen 25 when sliding on the screen 25. Therefore, in a state where the squeegee 31 is removed from the substrate 61 to the right and stopped, the force applied to the screen 25 by the squeegee 31 is received by the guides 67 and 69 on both sides shown in FIG.

  At this time, as shown in FIG. 10, the screen 25 is in a state of being bent downward by a minute amount. Note that the amount of deflection in the height direction of the screen 25 at this time is set to about 0.1 mm, for example. The setting of the bending amount can be arbitrarily adjusted by the gap between the upper surface of the substrate 61 and the upper surfaces of the guides 67 and 69 on both sides when the substrate 61 is raised in the Z-axis direction, that is, the vertical direction by the positioning unit 50. It is.

  As shown in FIG. 10, in a state where the squeegee 31 is separated from the substrate 61 and stopped on the screen 25, the upper Z-axis table 56 is lowered by a motor and a ball screw 58 (not shown), thereby The substrate 61 is moved downward together with 60 to release the plate from the screen 25.

  The screen 25 is pulled downward by this separating operation. The main reason is that the cream solder that has entered the hole of the screen 25 is printed on the land on the surface of the substrate 61, and the cream solder moves down the screen 25 due to the viscosity generated on the side surface of the hole of the pattern of the screen 25. By pulling. Since the force that pulls down the screen 25 generated at the time of separating the plate is received by the upper surfaces of the guides 67 and 69, the amount of downward deflection of the screen 25 can be suppressed to a very small amount. . After such plate separation, the squeegees 31 and 32 are raised by the air cylinders 35 and 36.

  Such plate separation operation makes it possible to minimize and minimize the movement and vibration of the screen 25 during plate separation after cream solder is printed on the land portion of the substrate 61. This enables high-accuracy screen printing of cream solder on the substrate 61.

  The screen printing apparatus for performing screen printing of cream solder in this way includes squeegees 31 and 32 that are equalized by a mechanism as shown in FIGS. That is, the squeegee 31 is attached to the squeegee holder 107, and is pressed and fixed by the presser plate 108 from the back side. The squeegee holder 107 has a rotation mechanism including a pin 126 at a substantially central portion in the length direction, so that the squeegee holder 107 can swing a predetermined angle with respect to the connecting bracket 106. This rotating mechanism uses, for example, a pin 126 and a ball bearing 127, and the squeegee 31 is lightly equalized with respect to the surface of the screen 25.

  Here, the connecting bracket 106 has a pair of hook levers 117 built into the insertion hole 116, and the hook 118 on the tip side of the hook lever 117 is supported by a torsion coil spring as indicated by an arrow in FIG. It is urged to rotate in a direction to engage with the locking notch 111 on the side surface 33.

  The connecting bracket 106 receives the support 33 in an in-row structure in the insertion hole 116, and at this time, the claw 118 of the hook lever 117 is locked to the locking notch 111. . Then, after connecting the connecting bracket 106 and the support 33, the main fastening screw 120 is tightened in the female screw hole 113 of the support 33 through the notch 119 of the connecting bracket 106, thereby connecting the connecting bracket 106 and the support 33. Are fixed and fixed with good reproducibility.

  Although the invention of the present application has been described with reference to the illustrated embodiment, the invention of the present application is not limited to the above-described embodiment, and various modifications are possible within the scope of the technical idea of the invention included in the present application. is there. For example, the above embodiment relates to a printing apparatus for cream solder, but the invention of the present application is widely applicable to printing apparatuses for various other paste-like substances.

  DESCRIPTION OF SYMBOLS 10 ... Support base, 11, 12 ... Guide rail, 13 ... Carriage, 14 ... Camera unit, 15 ... Image recognition camera, 18 ... Carriage, 19 ... Cleaning unit, 20 ... Cleaning tape, 21 ···················································································································································································· 22 Cylinder, 37, 38 ... guide rail, 39 ... carriage, 43 ... base, 44 ... Z axis guide, 45 ... Z axis table, 46 ... air cylinder, 47 ... rod, 48 ... stopper, 50 ... Positioning unit, 51 ... Y-axis table, 52 ... X-axis table, 53 ... θ-axis table, 54 ... Mounting plate, 55 ... Z-axis guide, 56 ... Axis table, 58 ... Ball screw, 60 ... Board mounting jig, 61 ... Board, 65, 66 ... Support, 67 ... Fixed guide, 68 ... Base, 69 ... Movement guide, 70 ... Conveyor belt, 73, 74 ... Arm, 75, 76 ... Support member, 77, 78 ... Presser claw, 81 ... Carry-in conveyor, 82 ... Carry-out conveyor, 85 ... Cylinder, 86 ... Correction pin, 91 , 92 Hinge, 93, 94 Air cylinder, 95, 96 Sliding plate, 98 Sliding plate, 106 Connecting bracket, 107 Squeegee holder, 108 Presser plate, 111 ················································································································· INN 123 ... Projection, 124, 12 5 ... Insertion hole, 126 ... Pin, 127 ... Ball bearing, 130 ... End plate

Claims (7)

In a screen printing apparatus in which a workpiece is superimposed on the lower surface of the screen and a paste-like substance is printed on the surface of the workpiece,
A positioning unit capable of moving up and down to overlap the work with the lower surface of the screen;
A squeegee that moves on the screen and prints the pasty substance;
A conveyor belt for conveying the workpiece;
A pair of guides for supporting the conveyor belt, provided to be located on both sides of the positioning unit along the moving direction of the squeegee;
The squeegee stops at a position off the work on the screen in a state where printing is finished, and the printing pressure of the squeegee at that time is received by the pair of guides, and the positioning unit The screen printing apparatus, wherein the squeegee is raised after the work is separated from the screen. The screen printing apparatus according to claim 1, wherein a surface of the workpiece is set to be slightly higher than an upper surface of the pair of guides. The screen printing apparatus according to claim 2, wherein a surface of the workpiece is set to be 0.03 to 1.0 mm higher than an upper surface of the pair of guides. The screen printing apparatus according to claim 1, wherein deformation of the screen downward when the workpiece is lowered by the positioning unit is restricted by the pair of guides. One of the pair of guides which are perpendicular to the moving direction of the squeegee and located on both sides of the positioning unit is movable with respect to the other, and the workpiece is clamped from both sides. The screen printing apparatus according to claim 1, wherein:   The screen printing apparatus according to claim 1, wherein the work is a circuit board.   The screen printing apparatus according to claim 1, wherein the paste-like substance is cream solder.

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