Screen printer

Abstract

To perform mixing processing sufficiently without being affected by an area of an extra region of a screen mask.SOLUTION: A screen printer 1A includes: a mixing mechanism part which mixes solder without moving the solder along a mask 6; and a main control unit 101 which executes mixing processing when printing processing is interrupted. The mixing mechanism part includes: a scraper unit 70 including a scraper 72, a sheet T disposed along the upper surface of the scraper 72, a stopper 82, and a sheet moving mechanism 75 which moves the sheet T; and a lifting mechanism 84 etc. which moves the unit 70. The main control unit 101 executes an operation for scooping the solder from the mask 6 onto the scraper 72, a mixing operation for moving the sheet T continuously with the scooped solder placed in contact with the stopper 82, and an operation for reversing the moving direction of the sheet T to return the solder from the scraper 72 to the mask 6.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a screen printing apparatus for printing (applying) a coating material such as cream solder onto a substrate such as a printed circuit board.

Background Art

[0002] A screen printing apparatus for printing (applying) a coating material such as cream solder onto a substrate such as a printed circuit board is known. The screen printing apparatus prints the coating material onto the substrate through an opening (mask opening) formed in a screen mask while moving the coating material on the screen mask superposed on the substrate with a squeegee.

[0003] The coating material used has a viscosity suitable for printing. When the viscosity decreases, printing defects such as blurring occur, significantly degrading the print quality. Therefore, when the printing process is interrupted for a period exceeding a certain time, a kneading process is performed to move the coating material with a squeegee using the surplus area of the screen mask, that is, the peripheral area where the mask opening is not formed. This is a countermeasure to suppress the deterioration (viscosity reduction) of the coating material (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, since the area of the surplus area of the screen mask is not very large, there is naturally a limit to moving the coating material, and there are many cases where sufficient kneading processing cannot be performed.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a screen printing apparatus capable of performing a kneading process better without being affected by the area of the surplus region of the screen mask.

Means for Solving the Problems

[0007] In order to solve the above problems, a screen printing apparatus according to an aspect of the present invention is a screen printing apparatus that executes a printing process of printing a coating material on a substrate through an opening formed in the screen mask by moving the coating material along the upper surface of the screen mask superposed on the substrate by a squeegee, and includes a kneading mechanism unit capable of executing a kneading process of kneading the coating material without moving it along the screen mask, and a control unit that controls the kneading mechanism unit to execute the kneading process when the printing process is interrupted.

[0008] According to this screen printing apparatus, since it is provided with a kneading mechanism unit capable of executing a kneading process of kneading the coating material without moving it along the screen mask, even when the area of the surplus region of the screen mask is narrow, it is possible to sufficiently knead the coating material. Note that "kneading the coating material without moving it along the screen mask" specifically means kneading the coating material without moving it along the upper surface of the screen mask from a certain position on the upper surface of the screen mask to a different position on the upper surface.

[0009] Specifically, the kneading mechanism unit includes a plate-shaped scraper, a sheet disposed along the upper surface of the scraper, a stopper disposed to face the upper surface of the sheet at a predetermined position spaced apart from the tip of the scraper, and a sheet driving unit that moves the sheet along the scraper. The kneading mechanism unit also includes a unit driving unit that moves the scooping unit. The control unit, during the kneading process, approaches the scooping unit to the screen mask and moves the sheet in a first direction from the side of the tip toward the side of the stopper, thereby scooping up the coating material from the tip of the scraper onto the sheet. Then, while making the scooped coating material abut against the stopper, the control unit continuously moves the sheet in the first direction to knead the coating material. Next, by moving the sheet in a second direction opposite to the first direction, the control unit performs a returning operation of returning the coating material from the scraper onto the screen mask, and these operations are configured to be executed in order.

[0010] According to the configuration of this screen printing apparatus, by the scooping-up operation, the coating material is scooped up from the screen mask onto the scraper. Specifically, the coating material is scooped up onto the scraper via the sheet. Then, when the kneading operation is executed, the coating material is kneaded. That is, with the coating material abutting against the stopper, as the sheet continuously moves in the first direction, the coating material rotates (rolls) while abutting against the stopper. According to this configuration, since the coating material is kneaded on the scraper, it is possible to sufficiently knead the coating material without being affected by the area of the surplus region of the screen mask.

[0011] In this case, at least the contact surface of the stopper with the coating material may be subjected to a low-friction treatment.

[0012] According to this configuration, it is possible to suppress the adhesion of the coating material to the stopper. Thereby, the kneading (rotation) of the coating material is promoted.

[0013] Further, as another specific configuration, the squeegee includes a flat pressing surface for pressing the coating material, the kneading mechanism unit supports the squeegee so as to be displaceable, and the control unit, during the kneading process, contacts the pressing surface with the surface of the coating material on the screen mask, and while changing the angle and height of the pressing surface along the surface with the coating material as the center, the squeegee may be configured to execute a kneading operation of reciprocatingly moving the squeegee along the screen.

[0014] According to this configuration, during the kneading process, with the pressing surface of the squeegee in contact with the surface of the coating material, the squeegee reciprocates along the screen while changing the pressing surface along the surface with the coating material as the center. By moving the squeegee in this way with the squeegee (pressing surface) in contact with the surface of the coating material, the coating material rotates (rolls) in that case. Therefore, also with this configuration, it is possible to sufficiently knead the coating material without being affected by the area of the surplus region of the screen mask.

Advantages of the Invention

[0015] According to the screen printing apparatus of the present invention described above, it is possible to perform the kneading process better without being affected by the area of the surplus region of the screen mask.

Brief Description of the Drawings

[0016]

Figure 1

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[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0018] [First Embodiment] FIG. 1 is a schematic configuration diagram (side view) of a screen printing apparatus 1A according to the first embodiment of the present invention. In the figure, XYZ rectangular coordinates are shown to clarify the direction relationship. The X direction is the horizontal direction, the Z direction is the vertical direction, and the Y direction is the direction orthogonal to both the X direction and the Z direction.

[0019] The screen printing apparatus 1A (hereinafter abbreviated as the printing apparatus 1A) includes a printing operation unit 2A that performs printing processing on a substrate P such as a printed circuit board, and a mask storage unit 2B that is disposed adjacent to the X1 side (one side in the X direction / the right side in FIG. 1). The mask storage unit 2B stores a screen mask for replacement.

[0020] The printing operation unit 2A is provided with a mask holding unit 3, a substrate holding unit 4, and a printing unit 5.

[0021] The substrate holding unit 4 includes an upper unit 4A and a lower unit 4B. The upper unit 4A holds the substrate P during printing operations, and includes a conveyor 20 for conveying the substrate P, a substrate support mechanism 22 for lifting and supporting the substrate P from the conveyor 20, and a substrate clamping mechanism 24 for clamping the substrate P lifted from the conveyor 20. The conveyor 20, the substrate support mechanism 22, and the clamping mechanism 24 are operated by actuators such as motors and air cylinders. The substrate P is carried onto the conveyor 20 from the upstream side in the Y direction (the back side in the direction orthogonal to the plane of FIG. 1), and is held in a state of being positioned in the upper unit 4A by the respective mechanisms 22 and 24. After the printing process, the positioning state of the substrate P is released, and it is carried out by the conveyor 20 to the downstream side in the Y direction (the front side in the direction orthogonal to the plane of FIG. 1).

[0022] The lower unit 4B moves the substrate P positioned in the upper unit 4A together with the upper unit 4A. Although detailed drawings are omitted, the lower unit 4B includes a table and a table drive mechanism operated by the actuator that displaces the table in the X, Y, Z, and R directions. Note that the R direction is the rotational direction around the Z axis.

[0023] The upper unit 4A is fixed on the table of the lower unit 4B. With this configuration, the substrate holding unit 4 is configured to be able to move the substrate P in each of the X, Y, Z, and R directions.

[0024] The mask holding unit 3 is disposed above the substrate holding unit 4. The mask holding unit 3 holds a screen mask 6 (hereinafter abbreviated as mask 6). The mask 6 is rectangular in plan view (rectangular or square), and includes a mask body 60 made of a thin metal plate in which printing openings (mask openings) are formed, and a frame body 62 made of metal (for example, aluminum) that holds the peripheral portion of the mask body 60. In the following description, unless otherwise specified, when referring to the mask 6, it refers to the mask body 60.

[0025] The mask holding unit 3 includes a pair of guide members 30 that extend parallel to each other in the X direction with a space therebetween in the Y direction, a mask clamping device (not shown) that clamps the mask 6 with respect to the pair of guide members 30, and a spacing variable mechanism (not shown) for changing the spacing between the pair of guide members 30. The mask clamping device and the spacing variable mechanism are operated by the actuator.

[0026] Each guide member 30 is a member having an L-shaped cross section including a support portion 30a that supports the mask 6 (frame body 62) and a guide portion 30b that restrains the screen mask 6 from the outside in the Y direction, and is formed of a metal material such as stainless steel.

[0027] The mask clamping device is provided on each guide member 30 and includes a clamping plate and the actuator that drives the clamping plate to move forward and backward in the Z direction. The mask clamping device fixes the mask 6 to the guide member 30 by sandwiching the mask 6 (frame body 62) between the support portion 30a of the guide member 30 and the clamping plate.

[0028] The spacing variable mechanism is a screw feed mechanism, and changes the spacing between the pair of guide members 30 by relatively moving one side of the pair of guide members 30 in the Y direction with respect to the other side by the actuator.

[0029] The printing unit 5 is movably provided above the mask holding unit 3. The printing unit 5 mainly moves the solder paste along the upper surface of the mask 6. The solder paste is an example of the coating material of the present invention, that is, a semi-fluid having conductivity and viscosity.

[0030] The printing unit 5 is provided so as to be movable in the X direction by the unit drive mechanism 10. The unit drive mechanism 10 includes a rail 12 that extends in the X direction and supports the printing unit 5 movably, a screw shaft 14 that is provided in parallel with the rail 12 and is screwed into a nut member (not shown) of the printing unit 5, and a motor 15 that drives the screw shaft 14. That is, when the screw shaft 14 is rotationally driven by the servo motor 15, the printing unit 5 moves in the X direction along the rail 12.

[0031] As shown in FIG. 1, the rail 12 and the screw shaft 14 extend from the end portion on the X2 side (the other side in the X direction / the left side in FIG. 1) of the printing operation unit 2A to the middle portion of the mask storage unit 2B. Accordingly, the printing unit 5 can move in the X direction from the end portion on the X2 side of the printing operation unit 2A to the middle portion of the mask storage unit 2B.

[0032] The printing unit 5 is further equipped with a squeegee 16, a squeegee drive mechanism 17, a mask slider 18, a distance sensor 19, and a solder transfer unit 7.

[0033] The squeegee 16 is a rectangular plate member elongated in the Y direction and having a flat pressing surface 16a for pressing the solder paste (hereinafter abbreviated as solder). The squeegee 16 reciprocates in the X direction integrally with the printing unit 5. The solder moves in the X direction along the upper surface of the mask 6 by being pressed by the squeegee 16 through the pressing surface 16a.

[0034] The squeegee drive mechanism 17 is actuated by the actuator to rotate the squeegee 16 about an axis extending in the Y direction and move it up and down (move in the Z direction). By the operation of the squeegee drive mechanism 17, the squeegee 16 moves to a position where it can slide on the mask 6 (the position shown by the two-dot chain line in FIG. 1) and a position where it retracts above the mask 6 (the position shown by the solid line in FIG. 1), and the posture is changed as shown in FIG. 2 during the forward movement and the reverse movement so that the pressing surface 16a faces the front in the traveling direction.

[0035] The mask slider 18 is a mask engaging device for moving the mask 6 between the printing operation unit 2A and the mask storage unit 2B. The mask slider 18 includes a pin 18a extending in the Z direction and a pin driving unit 18b such as an air cylinder that drives the pin 18a to move forward and backward in the Z direction. The pin 18a, by the operation of the pin driving unit 18b, has its tip (lower end) lower than the upper surface of the frame 62 of the mask 6 supported by the guide member 30 and higher than the upper surface of the mask body 60, at a predetermined protruding position (lowering position), and is displaced to a retracted position (raising position) where it has retreated above the mask 6 from this position. That is, the mask slider 18 moves the mask 6 in the X direction as the printing unit 5 moves by hooking the pin 18a on the frame 62. In FIG. 1, the mask slider 18 with the pin 18a displaced to the retracted position is shown.

[0036] On the other hand, in the mask storage unit 2B, a mask stocker 40 in which a plurality of masks 6 can be taken in and out and a lifting mechanism 44 (see FIG. 8) for moving the mask stocker 40 up and down (moving in the Z direction) are arranged. The mask stocker 40 has upper and lower storage portions 42a, 42b (sometimes referred to as the first storage portion 42a and the second storage portion 42b), and two types of masks 6 with different mask opening patterns are stored in these storage portions 42a, 42b.

[0037] In the following description, the mask 6 stored in the upper storage portion 42a may be referred to as the first mask 6A, and the mask 6 stored in the lower storage portion 42b may be referred to as the second mask 6B.

[0038] The lifting mechanism 44 is operated by the actuator and selectively arranges either the first storage portion 42a or the second storage portion 42b at a predetermined mask exchange height position facing the guide member 30 in the X direction. The mask exchange height position is a position where it is possible (to take in and out) to move the mask 6 in the X direction between the guide member 30 and each of the storage portions 42a, 42b. FIG. 1 shows a state where the second storage portion 42b is arranged at the mask exchange height position and the second mask 6B is arranged in the printing operation unit 2A (guide member 30).

[0039] The solder transfer unit 7 is a unit for transferring solder from the mask 6 before replacement to the mask 6 after replacement during mask replacement, and for performing a kneading process of kneading the solder when the printing process is interrupted. In this example, the solder transfer unit 7 and the mechanism for moving it (such as the unit drive mechanism 10) correspond to the "kneading mechanism part" of the present invention.

[0040] FIG. 3 is a schematic configuration diagram of the solder transfer unit 7 in a side view. As shown in FIGS. 1 and 3, the solder transfer unit 7 includes a scraper unit 70 for scooping up solder from the mask 6, and a lifting mechanism 84 for lifting and lowering (moving in the Z direction) the scraper unit 70 with respect to the frame of the printing unit 5. The lifting mechanism 84 is operated by the actuator. In this example, the scraper unit 70 corresponds to the "scooping-up unit part" of the present invention, and the unit drive mechanism 10 and the lifting mechanism 84 correspond to the "unit drive part" of the present invention.

[0041] The scraper unit 70 has a scraper 72 for scooping up solder from the mask 6. The scraper 72 is a plate-like member that is elongated in the Y direction and rectangular in a plan view, and has a flat upper surface 72a and a lower surface 72b. The upper surface 72a is inclined so as to rise from the tip 72c (the end on the X2 side) to the rear end 72d (the end on the X1 side) of the scraper 72.

[0042] The scraper unit 70 includes a housing 73 connected to the lifting mechanism 84, and the scraper 72 is supported by the housing 73 via a plate-like support frame 74 having a thickness in the X direction. Specifically, the support frame 74 is provided so as to extend downward from the housing 73, and the rear end 72d of the scraper 72 is fixed to the lower end portion of the support frame 74.

[0043] The scraper unit 70 has a belt-like sheet T disposed along the scraper 72 and the support frame 74, and a sheet moving mechanism 75 (corresponding to the "sheet drive part" of the present invention) for moving the sheet T in its longitudinal direction.

[0044] The sheet moving mechanism 75 includes first and second drive rollers 76A and 76B around which a sheet T is wound, and first to third guide rollers 77 to 79. Each of the rollers 76A, 76B, and 77 to 79 is rotatably provided about an axis extending in the Y direction.

[0045] The first drive roller 76A is rotatably supported by the housing 73 at a position spaced apart from the support frame 74 toward the X1 side, and the second drive roller 76B is rotatably supported by the housing 73 above the first drive roller 76A. The first drive roller 76A and the second drive roller 76B are each driven by a motor (not shown).

[0046] The first to third guide rollers 77 to 79 are all driven rollers that are driven as the sheet T moves. The first guide roller 77 is disposed adjacent to the support frame 74 on the X1 side thereof and is rotatably supported by the housing 73. The second guide roller 78 is disposed above and close to the rear end 72d of the scraper 72 and is rotatably supported by a frame (not shown) of the scraper unit 70. The third guide roller 79 is rotatably supported by the housing 73 above the support frame 74 and at a position on the X2 side of the second drive roller 76B.

[0047] As shown in FIG. 3, the sheet T is fed out from the first drive roller 76A, passed over the first guide roller 77 and the rear end 72d of the scraper 72, folded back from the lower surface 72b side to the upper surface 72a side at the front end 72c of the scraper 72, passed over the second and third guide rollers 78 and 79, and then wound around the second drive roller 76B.

[0048] That is, the sheet T can be switched between a state where it is fed out from the first drive roller 76A and wound up by the second drive roller 76B (a state of forward driving of the sheet T) and a state where it is fed out from the second drive roller 76B and wound up by the first drive roller 76A (a state of reverse driving of the sheet T) by switching the rotational driving directions of the first drive roller 76A and the second drive roller 76B between forward and reverse.

[0049] The sheet moving mechanism 75 is provided with an encoder 80. The encoder 80 includes an encoder disk 80a that rotates together with the third guide roller 79, and an encoder sensor 80b that detects the rotational position of the encoder disk 80a. The detection result by the encoder sensor 80b is transmitted to a control device 100 described later, and the control device 100 obtains the moving amount of the sheet T and the like based on this detection result.

[0050] The scraper unit 70 further includes a stopper 82. The stopper 82 is a member that regulates the movement of solder during the kneading process of solder described later. The stopper 82 is a plate-shaped member having a rectangular cross-section with a thickness in the X direction. The stopper 82 is fixed to a frame (not shown) of the scraper unit 70 at a position adjacent to the X2 side of the second guide roller 78 in a state where its lower end surface faces the upper surface 72a of the scraper 72 with a gap therebetween. The gap between the upper surface 72a of the scraper 72 and the stopper 82 is set to a dimension as close as possible to the thickness of the sheet T and that allows the movement of the sheet T. That is, the aforementioned sheet T is stretched across the second guide roller 78 along the upper surface 72a of the scraper 72 through the gap between the upper surface 72a and the lower end surface of the stopper 82. Note that the stopper 82 may be detachably fixed to the frame of the scraper unit 70. In this case, a configuration can be adopted in which the stopper 82 is detachably held by a clamp mechanism operated by an actuator such as an air cylinder.

[0051] The surface on the X2 side of the stopper 82 is a regulating surface 82a (contact surface) that regulates the movement of the solder and is formed flat. The stopper 82 is inclined toward the X2 side with respect to the normal line of the upper surface 72a of the scraper 72 such that the regulating surface 82a and the upper surface 72a of the scraper 72 form an acute angle. Note that the regulating surface 82a may be subjected to a low-friction treatment such as Teflon (registered trademark) processing to suppress, for example, the adhesion of solder.

[0052] The distance sensor 19 detects the distance to the object facing the upper surface of the mask 6 from above and outputs it to the control device 100 described later. The distance sensor 19 is used to measure the position and shape (roll shape) of the solder on the upper surface of the mask 6. That is, the distance sensor 19 scans the upper surface of the mask 6 as the printing unit 5 moves in the X direction, and the control device 100 acquires the position, width in the X direction, and height in the Z direction of the solder based on the result.

[0053] The printing apparatus 1A includes a control device 100 as shown in FIG. 1. The control device 100 is composed of a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and peripheral devices, and includes a main control unit 101 (corresponding to the control unit of the present invention), a drive control unit 102, a storage unit 103, an input / output control unit 104, etc. as its functional configuration.

[0054] The main control unit 101 comprehensively controls the operation of the printing apparatus 1A. The main control unit 101 controls the operations of each part of the printing apparatus 1A, such as the mask holding unit 3, the substrate holding unit 4, the printing unit 5, and the solder transfer unit 7, via the drive control unit 102 according to a program, production plan information, production substrate data, etc. stored in advance in the storage unit 103 to execute the printing process and the kneading process described later, and also executes arithmetic processing necessary for various processes and operations. In this example, this main control unit 101 corresponds to the "control unit" of the present invention.

[0055] The input / output control unit 104 is an interface that controls the input / output of signals between various actuators such as the motor 15 and various sensors such as the distance sensor 19 and the control device 100.

[0056] Next, the operation control of the printing apparatus 1A by the main control unit 101 will be described based on the flowcharts of FIGS. 4 and 5 with reference to FIGS. 6 to 10.

[0057] FIG. 4 is a flowchart showing the operation control of the printing apparatus 1A by the main control unit 101. When the operation control of the printing process by the main control unit 101 starts, the main control unit 101 executes the printing operation based on the flowchart of FIG. 5 (step S1). FIG. 5 is a flowchart of a subroutine (printing operation).

[0058] First, the main control unit 101 determines whether or not the substrate P has been carried into the printing apparatus 1A based on a signal input from a sensor (not shown) (step S11). If it is determined that the substrate has been carried in, the main control unit 101 determines whether or not a timer (described later) has counted the set time (step S12). If the timer has not counted the time, the main control unit 101 turns off the timer (step S13) and executes the printing process for the substrate P (step S14). That is, after the main control unit 101 holds the substrate P carried into the machine by the substrate holding unit 4, it overlays the substrate P on the lower surface of the mask 6. Next, the squeegee 16 is brought into contact with the upper surface of the mask 6 so that the pressing surface 16a of the squeegee 16 and the upper surface of the mask 6 form a predetermined angle (attack angle). In this state, the squeegee 16 is moved from the X1 side toward the X-axis 2 side or from the X-axis 2 side toward the X1 side. By this operation, while moving the solder supplied on the upper surface of the mask 6 by the squeegee 16, the solder is applied (printed) to the substrate P through the mask opening.

[0059] When the printing is completed, the main control unit 101 separates the substrate P downward from the mask 6. Thereby, the printing process for the substrate P is completed.

[0060] When the printing process is completed, the main control unit 101 turns on the timer (step S15). After carrying out the substrate P after the printing process outside the machine (to the apparatus in the subsequent process) (step S16), it further determines whether or not a predetermined number of productions have been completed (step S17). For example, the total number of substrates P in one production lot is set as the predetermined number. If it is determined here that the production of the predetermined number has not been completed, the main control unit 101 transfers the process to step S11. On the other hand, if it is determined that the production of the predetermined number has been completed, the main control unit 101 ends the control of the printing operation and transfers the process to the process of step S3 in FIG. 4.

[0061] On the other hand, in the process of step S11, if it is determined that the substrate P has not been loaded into the printing apparatus 1A, the main control unit 101 determines whether or not the timer has counted the set time (step S20). If it is determined here that the timer has not counted the set time, the main control unit 10 transfers the process to step S11. On the other hand, if it is determined that the time has been counted, the main control unit 10 turns off the timer, executes the kneading process of the solder, then turns on the timer (steps S21 to S23), and then transfers the process to step S11. The kneading process of the solder is an operation of forcibly rotating (rolling) the solder in order to prevent the deterioration (viscosity reduction) of the solder. This point will be described later.

[0062] Also, in the process of step S12, if it is determined that the timer has counted the set time, the main control unit 101 turns off the timer, executes the kneading process of the solder (steps S18, S19), and then transfers the process to step S14.

[0063] Returning to FIG. 4, when the process of step S1 (printing operation) is completed, the main control unit 101 determines whether or not there is a model change, that is, whether or not there is a change in the production product type (step S3). If it is determined that there is a model change, the main control unit 101 controls the printing unit 5, the solder transfer unit 7, the unit drive mechanism 10, the elevating mechanism 44, etc., and executes the solder scooping-up operation (step S5), the mask exchange operation (step S7), and the solder return operation (step S9) in this order.

[0064] The solder scooping-up operation is an operation of scooping up and removing solder from the mask 6 in use prior to mask replacement. The mask replacement operation is an operation of replacing the mask 6 in use with the mask 6 after model change, that is, another mask 6 stored in the mask stocker 40. The solder returning operation is an operation of returning the solder scooped up from the mask 6 before replacement onto the mask 6 after replacement.

[0065] FIG. 6 is an explanatory diagram of the solder scooping-up operation. First, the main control unit 101 scans the solder S on the mask 6 with the distance sensor 19 by moving the printing unit 5 in the X direction. Thereby, the position of the solder S is detected.

[0066] Next, based on the detected position information of the solder S, the main control unit 101 arranges the scraper unit 70 so that the scraper 72 is positioned at a position slightly separated from the solder S on the mask 6 toward the X1 side. Specifically, as shown in FIG. 6(a), with the tip 72c of the scraper 72 facing the solder S, the scraper 72 is brought into contact with the upper surface of the mask 6 via the sheet T. Thereafter, the main control unit 101 sets the sheet T to the forward driving state. That is, the sheet T is in a state of being fed out from the first driving roller 76A and wound around the second driving roller 76B. In this state, as shown by the solid arrow in FIG. 6(a), the sheet T moves from the tip 72c toward the rear end 72d along the upper surface 72a of the scraper 72 (in the "first direction" of the present invention).

[0067] Next, as indicated by the dashed-dotted arrow in FIG. 6, the main control unit 101 moves the scraper 72 forward toward the X2 side. As a result, when the tip 72c of the scraper 72 reaches the position of the solder S, as shown in FIG. 6(b), as the sheet T moves, the solder S on the mask 6 moves onto the upper surface 72a of the scraper 72 through the sheet T. That is, the solder S is scooped up onto the upper surface 72a of the scraper 72. When the solder S is scooped up onto the upper surface 72a of the scraper 72, the main control unit 101 stops the movement of the sheet T and then moves (retracts) the solder S together with the scraper 72 above the mask holding unit 3. Thereby, the solder scooping operation is completed.

[0068] When the solder scooping operation is completed, the main control unit 101 executes a mask exchange operation. FIGS. 8 and 9 are explanatory diagrams of the mask exchange operation. Here, as shown in FIG. 1, an operation of exchanging the second mask 6B set on the guide member 30 with the first mask 6A in the mask stocker 40 will be described.

[0069] First, the main control unit 101 moves the printing unit 5 so that the pin 18a of the mask slider 18 is positioned on the X2 side of the second mask 6B and arranges the pin 18a at the protruding position at that location (FIG. 8(a)).

[0070] Next, after the main control unit 101 releases the clamping state of the second mask 6B by the mask holding unit 3, it moves the printing unit 5 toward the mask storage unit 2B. That is, the pin 18a is hooked on the second mask 6B, and the second mask 6B is moved in the X direction together with the printing unit 5 (FIG. 8(b)). Thereby, the second mask 6B is transferred from the mask holding unit 3 to the second storage unit 42b of the mask stocker 40.

[0071] Next, the main control unit 101 lowers the mask stocker 40 so that the first storage unit 42a of the mask stocker 40 is arranged at the mask exchange height position, that is, so that the second storage unit 42b of the mask stocker 40 faces the guide member 30 in the X direction (FIG. 8(c)). At this time, the pin 18a of the mask slider 18 is arranged at the retracted position.

[0072] When the first storage unit 42a is arranged at the mask replacement height position, the main control unit 101 moves the first mask 6A in the first storage unit 42a to the mask holding unit 3. Specifically, the printing unit 5 is moved so that the pin 18a of the mask slider 18 is located inside the frame body 62 of the first mask 6A. After the pin 18a of the mask slider 18 is arranged at the protruding position there (Fig. 9(a)), the printing unit 5 is moved from the mask storage unit 2B toward the printing operation unit 2A. Thereby, the pin 18a is hooked on the frame body 62 from the inside of the first mask 6A, and the first mask 6A is moved together with the printing unit 5 to the position of the mask holding unit 3 (Fig. 9(b)). Thereafter, the mask 6 is fixed to the guide member 30 by a mask clamping device (not shown), and the pin 18a of the mask slider 18 is arranged at the retracted position. Thereby, the mask replacement operation is completed.

[0073] When the mask replacement operation is completed, the main control unit 101 executes a solder return operation. Fig. 7 is an explanatory diagram of the solder return operation.

[0074] First, the main control unit 101 causes the scraper 72 that scooped up the solder S in the process of step S5 to abut on the upper surface of the mask 6 after replacement via the sheet T as shown in Fig. 7(a).

[0075] Next, the main control unit 101 sets the sheet T to the backward driving state. That is, the state where the sheet T is fed out from the second driving roller 76B and wound around the first driving roller 76A. In this state, as shown by the solid line arrow in Fig. 7(a), the sheet T moves from the rear end 72d toward the front end 72c (the "second direction" of the present invention) along the upper surface 72a of the scraper 72. In addition, the main control unit 101 moves the scraper 72 to the X1 side as shown by the dashed-dotted line arrow in Fig. 7. Thereby, as shown in Fig. 7(b), the solder S moves from the upper surface 72a of the scraper 72 onto the mask 6.

[0076] As shown in FIG. 7(c), when the solder S has completely moved from the upper surface 72a of the scraper 72 onto the mask 6, the main control unit 101 stops the movement of the sheet T and then moves (retracts) the scraper 72 upward. Thereby, the solder return operation is completed.

[0077] When the solder return operation is completed, the main control unit 101 shifts the process to step S1. The above is a series of operation controls by the main control unit 101.

[0078] During the process of step S1 described above, the printing process of the substrate P may be interrupted due to troubles in other equipment (equipment in the previous process) or urgent maintenance. In this case, if the solder on the mask 6 is left unattended for a long time, the solder will deteriorate (decrease in viscosity), which may cause printing defects such as blurring.

[0079] In the printing apparatus 1A, in order to prevent such deterioration of the solder, when a certain time (timer set time) has elapsed after the previous printing process or after the previous kneading process (Yes in steps S12 and S20 of FIG. 5), the main control unit 101 executes the kneading process of the solder (steps S19 and S22 of FIG. 5). The kneading process of the solder is, as described above, an operation of forcibly rotating (rolling) the solder to prevent the viscosity deterioration of the solder.

[0080] Specifically, the main control unit 101 controls the solder transfer unit 7 and the unit drive mechanism 10 to move the solder on the mask 6 to the upper surface 72a of the scraper 72. The operation control at this time is the same as the control of the solder scooping-up operation (step S5 of FIG. 4) described above with reference to FIGS. 6(a) to (c). That is, the main control unit 101 abuts the scraper 72 against the upper surface of the mask 6 via the sheet T with the tip 72c of the scraper 72 facing the solder S, and advances the scraper unit 70 to the X2 side while driving the sheet T forward. Thereby, the solder S on the mask 6 is moved to the upper surface 72a of the scraper 72 via the sheet T.

[0081] When the solder S moves (is lifted up) onto the upper surface 72a of the scraper 72, the main control unit 101 continues the forward driving state of the sheet T for a further set time (kneading time). In this case, the sheet T may be temporarily stopped and then redriven after the solder S has moved onto the upper surface 72a of the scraper 72, or may be continuously driven without being stopped.

[0082] As a result, the solder S moves from the tip 72c side of the scraper 72 toward the rear end 72d side and abuts against the regulating surface 82a of the stopper 82. In a state where the solder S abuts against the regulating surface 82a like this, when the movement of the sheet T is continued, as shown in FIG. 10, the solder S is kneaded. That is, as indicated by the arrow in FIG. 10, the solder S rotates (rolls). In this case, when the low-friction treatment is applied to the regulating surface 82a, adhesion of the solder S to the regulating surface 82a is suppressed and rotation of the solder S is promoted.

[0083] After the main control unit 101 has driven the sheet T forward for the set time, in other words, after kneading the solder S for the set time, it moves the solder S from the upper surface 72a of the scraper 72 onto the mask 6. The operation control at this time is the same as the control of the solder return operation (step S9 in FIG. 4) described above using FIGS. 7(a) to (c). That is, the main control unit 101 causes the scraper 72 to abut against the upper surface of the mask 6 via the sheet T, and while driving the sheet T in reverse, moves the scraper 72 to the X1 side. Thereby, the solder S is moved from the upper surface 72a of the scraper 72 onto the mask 6. In this case, since the low-friction treatment such as Teflon (registered trademark) processing is applied to the regulating surface 82a of the stopper 82, adhesion of the solder S to the stopper 82 is suppressed.

[0084] When the solder moves (is returned) from the upper surface 72a of the scraper 72 onto the mask 6, the main control unit 101 moves (retracts) the scraper 72 above the mask holding unit 3. Thereby, the kneading process of the solder is completed.

[0085] [Effect] As described above, in the aforementioned printing apparatus 1A, when the printing process of the substrate P is interrupted for a certain period of time due to troubles in other equipment (equipment in the previous process) or sudden maintenance, etc., a kneading process for forcibly rotating (rolling) the solder is executed. Therefore, the solder on the mask 6 is not left unattended for a long time, and deterioration of the solder is prevented.

[0086] Moreover, in the aforementioned printing apparatus 1A, a solder transfer unit 7, which is equipment for scooping up and holding the solder from the mask 6 during mask replacement, is used. The solder on the mask 6 is moved (scooped up) onto the upper surface 72a of the scraper 72 of this solder transfer unit 7, and the solder S is kneaded on this scraper 72. Therefore, the solder S can be kneaded without being affected by the size of the surplus area of the mask 6. In this case, by changing the moving speed and moving amount of the sheet T by controlling the sheet moving mechanism 75, the kneading mode (rotation speed, rotation amount) of the solder can be changed based on parameters such as the type of solder and the total interruption time of the printing process. Therefore, compared with a conventional printing apparatus that kneads the solder by moving the solder with a squeegee within a small surplus area on the mask surface, it is possible to perform the kneading process of the solder S better.

[0087] In particular, in the above printing apparatus 1A, a stopper 82 is provided facing the upper surface 72a of the scraper 72, and the solder is kneaded (rotated) by bringing the solder into contact with this stopper 82 (regulation surface 82a) as the sheet T moves. Therefore, it is possible to execute the kneading process of the solder with a relatively simple configuration in which the stopper 82 is added to the existing equipment (that is, the solder transfer unit 7).

[0088] Note that in the aforementioned printing apparatus 1A, the main control unit 101 is configured to execute the kneading operation of the solder when the printing operation is interrupted for a certain period (the set time of the timer). In addition, the kneading process of the solder S may also be executed during the mask replacement operation. That is, after the solder is scooped up from the mask 6 by the solder transfer unit 7, the kneading process of the solder may be executed until the solder is returned to the mask 6 after replacement.

[0089] [Second Embodiment] Next, the screen printing apparatus 1B according to the second embodiment of the present invention will be described. Since the basic configuration of the screen printing apparatus 1B (hereinafter abbreviated as the printing apparatus 1B) according to the second embodiment is the same as that of the printing apparatus 1A of the first embodiment shown in FIG. 1, the detailed structure of the parts common to the printing apparatus 1A of the first embodiment will be omitted or simplified here, and the differences from the printing apparatus 1A of the first embodiment will be mainly described.

[0090] In the printing apparatus 1B of the second embodiment, the specific content of the kneading process of the solder in step S25 of FIG. 5 described above, that is, the solder kneading process, is different from that of the printing apparatus 1A of the first embodiment as described below.

[0091] In the printing apparatus 1A of the first embodiment, the solder transfer unit 7 was used for the solder kneading process. In contrast, the printing apparatus 1B of the second embodiment is configured to knead the solder on the mask 6 by the squeegee 16. That is, in the printing apparatus 1B of the second embodiment, the solder transfer unit 7 has only the function of transferring the solder from the mask 6 before replacement to the mask 6 after replacement. Therefore, the scraper unit 70 is not provided with the stopper 82 described above.

[0092] The content of the kneading process in step S25 in the printing apparatus 1B of the second embodiment is as follows. First, the main control unit 101 controls the unit drive mechanism 10 to move the printing unit 5 in the X direction, and the distance sensor 19 scans the solder on the mask 6, thereby measuring the position and shape (roll shape) of the solder. The solder is assumed to be in the surplus area of the mask 6, that is, outside the area (X1 side) where the mask opening is formed.

[0093] When the measurement is completed, the main control unit 101 controls the printing unit 5 and the unit drive mechanism 10 based on the measurement results, and in a posture where the pressing surface 16a faces the X2 side and is perpendicular to the mask 6, the squeegee 16 is brought into contact with the upper surface of the mask 6 at a position away from the solder S toward the X1 side, and as shown in Fig. 11(a), the squeegee 16 is moved to a position where the pressing surface 16a contacts the solder S from the X1 side. Note that Fig. 11 is an operation explanatory diagram of the kneading process in the second embodiment. In this Fig. 11 and Fig. 12 described later, for convenience, the solder S is shown large with respect to the squeegee 16.

[0094] Thereafter, as shown in Figs. 11(b) to (g), the main control unit 101 executes a forward movement operation (the operation of the solid line arrow in Fig. 11) of moving the squeegee 16 along the mask 6 toward the X2 side while gradually changing the angle and height of the pressing surface 16a along the surface of the solder S (the roll-shaped surface) around the solder S so that the state where the pressing surface 16a contacts the surface of the solder S is maintained.

[0095] When the forward movement operation is completed, specifically, as shown in Fig. 11(g), when the squeegee 16g is moved to a posture where the pressing surface 16a faces the X1 side and is perpendicular to the mask 6, the main control unit 101 executes a reverse movement operation (the operation of the dashed line arrow in Fig. 11), which is an operation opposite to the forward movement operation. That is, from the state shown in Fig. 11(g), the squeegee 16 is moved along the mask 6 toward the X1 side while gradually changing the angle and height of the pressing surface 16a along the surface of the solder S around the solder S so that the state where the pressing surface 16a contacts the surface of the solder S is maintained.

[0096] FIG. 12 shows the locus of squeegee 16 in the above-described forward movement operation and reverse movement operation. When the squeegee 16 is moved such that the pressing surface 16a follows the surface of the solder S, that is, the roll-shaped surface (a surface with a substantially arc-shaped cross section), due to the friction with the pressing surface 16a, the surface layer of the solder S moves together with the pressing surface 16a, and as a result, rotation (rolling) occurs in the solder S. That is, rotation occurs in the solder S on the spot. Specifically, as indicated by the solid-line arrow in FIG. 12, during the forward movement operation, the solder S rotates counterclockwise (counterclockwise in FIG. 12), and during the reverse movement operation, as indicated by the dashed-line arrow, the solder S rotates clockwise. Thereby, the solder S is kneaded.

[0097] When the main control unit 101 repeats the above-described forward movement operation and reverse movement operation a set number of times, the operation is stopped and the squeegee 16 is raised. Thereby, the kneading process of the solder is completed.

[0098] In the above description, the main control unit 101 starts the forward movement operation of the squeegee 16 with the pressing surface 16a in contact with the solder S from the X1 side, but the forward movement operation of the squeegee 16 may be started with the pressing surface 16a in contact with the solder S from the X2 side.

[0099] Also in the case of the printing apparatus 1B of the second embodiment as described above, when the printing process of the substrate P is interrupted for a certain period of time, a kneading process for forcibly rotating (rolling) the solder is executed. Therefore, the solder on the mask 6 is not left unattended for a long time, and deterioration of the solder is prevented.

[0100] In particular, in the kneading process of the second embodiment, as described above, the solder is rotated in place. That is, the solder can be kneaded without moving the solder along the mask 6 from one point to a different point on the mask 6. Therefore, even when the surplus area on the upper surface of the mask is relatively small (small), the kneading process of the solder can be sufficiently performed. Therefore, according to the printing apparatus 1B of the second embodiment, compared with the conventional printing apparatus that moves the solder by a squeegee within a small surplus area on the upper surface of the mask, the kneading process of the solder can be performed better.

[0101] Moreover, the above-described solder kneading process can be executed only by a soft change in a printing apparatus provided with a printing unit of the same type as the printing unit 5. Therefore, there is an advantage that it can be applied to existing printing apparatuses relatively easily.

[0102] In the printing apparatus 1B of the second embodiment described above, the printing unit 5 and the unit drive mechanism 10 correspond to the kneading mechanism part of the present invention. [Reference Example] Next, the screen printing apparatus 1C according to the reference example will be described. Since the basic configuration of the screen printing apparatus 1C according to the reference example (hereinafter abbreviated as the printing apparatus 1C) is equivalent to that of the printing apparatus 1A of the first embodiment shown in FIG. 1, here, the detailed structure of the common part with the printing apparatus 1A of the first embodiment will be omitted or simplified, and mainly the differences from the printing apparatus 1A of the first embodiment will be described.

[0103] The printing apparatus 1C of the reference example has a specific configuration for the kneading process that is different from that of the printing apparatus 1A of the first embodiment as described below.

[0104] In the printing apparatus 1A of the first embodiment, the solder transfer unit 7 was used for the kneading process of solder. On the other hand, in the printing apparatus 1C of the reference example, a dedicated mask 6 for kneading solder is provided, and the kneading process of solder is configured to be performed using this dedicated mask. That is, in the printing apparatus 1C of the reference example, the solder transfer unit 7 has only the function of transferring solder from the mask 6 before replacement to the mask 6 after replacement. Therefore, the scraper unit 70 is not provided with the stopper 82 described above.

[0105] The printing apparatus 1C of the reference example includes a kneading mask 6A in the mask stocker 40 as the dedicated mask. For convenience, the mask with the reference numeral 6A in FIG. 1 is described as the kneading mask 6A, and the mask with the reference numeral 6B is described as the production mask 6B. That is, in FIG. 1, the production mask 6B is set in the mask holding unit 3, and the kneading mask 6A is stored in the mask stocker 40.

[0106] The production mask 6B is a normal mask including a mask body 60 in which mask openings are formed. On the other hand, the kneading mask 6A is a mask including a non-porous mask body 60 in which no mask openings are formed. The materials and configurations of both masks 6A and 6B are the same except for the presence or absence of mask openings.

[0107] In the following description, unless otherwise specified, the mask 6 refers to the production mask 6B. Also, the production mask 6B may be abbreviated as mask 6B, and the kneading mask 6A may be abbreviated as mask 6A.

[0108] FIG. 13 is a flowchart showing the operation control of the printing apparatus 1C by the main control unit 101. In the printing apparatus 1C of the reference example, the main control unit 101 controls the operation of the printing apparatus 1C based on the flowchart of FIG. 13 instead of the flowcharts of FIGS. 4 and 5.

[0109] Note that the processes of steps S31 to S43 in the flowchart of FIG. 13 are basically the same as the processes of steps S11 to S23 in the flowchart of FIG. 5 described above, except that the specific kneading process contents in steps S39 and S42 are different.

[0110] That is, the main control unit 101 determines whether the substrate P has been carried into the printing apparatus 1C based on a signal input from a sensor (not shown) (step S31). If it is determined that the substrate has been carried in, the main control unit 101 determines whether the timer has counted the set time (step S32). If not, the timer is turned off (step S33), and the printing process for the substrate P is executed (step S34). When the printing is completed, the main control unit 101 separates the substrate P downward from the mask 6. Thereby, the printing process for the substrate P is completed.

[0111] Thereafter, the main control unit 101 turns on the timer, carries out the substrate P to the outside of the machine (the apparatus in the next process) (steps S35, S36), and determines whether a predetermined number of productions have been completed (step S37). If the main control unit 101 determines here that the production has not been completed, the process proceeds to step S31. On the other hand, if it is determined that a predetermined number of productions have been completed, the process of this flowchart is terminated.

[0112] Note that in the process of step S31, if it is determined that the substrate P has not been carried into the printing apparatus 1C, the main control unit 101 determines whether the timer has counted the set time (step S40). If it is determined that the timer has counted, the timer is turned off, and the solder kneading process is executed based on the flowchart of FIG. 14 (steps S41, S42). Thereafter, the timer is turned on (step S43), and the process proceeds to step S31.

[0113] Also, in the process of step S32, if it is determined that the timer has counted the set time, the main control unit 101 turns off the timer, and after executing the solder kneading process (steps S38, S39), the process proceeds to step S34.

[0114] FIG. 14 is a flowchart of a subroutine (kneading process) for operation control in FIG. 13. The main control unit 101 controls the printing unit 5, the solder transfer unit 7, the unit drive mechanism 10, the lifting mechanism 44, etc., to execute a solder scooping-up operation (step S51), a mask exchange operation (step S53), and a solder return operation (step S55).

[0115] As described above, the solder scooping-up operation is an operation of scooping up and removing solder from the mask prior to mask exchange. The mask exchange operation is an operation of exchanging the mask with another mask stored in the mask stocker 40. The solder return operation is an operation of returning the scooped-up solder onto the mask after exchange.

[0116] These operation controls by the main control unit 101 are basically the same as the operation controls described in the first embodiment with reference to FIGS. 6 to 9. First, the main control unit 101 moves the printing unit 5 in the X direction to scan the solder S on the mask 6 with the distance sensor 19, thereby detecting the position of the solder S.

[0117] Next, based on the detected position information of the solder S, the main control unit 101 arranges the scraper unit 70 so that the scraper 72 is positioned at a position slightly separated from the solder S on the mask 6 toward the X1 side. After setting the sheet T in the forward driving state, the main control unit 101 moves the scraper 72 (scraper unit 70) forward toward the X2 side (FIGS. 6(a) and 6(b)). Accordingly, as the sheet T moves, the solder on the mask 6 is moved onto the upper surface 72a of the scraper 72 via the sheet T, that is, the solder is scooped up onto the upper surface 72a of the scraper 72 (FIG. 6(c)). Thereafter, the main control unit 101 stops the movement of the sheet T and moves (retreats) the solder together with the scraper 72 above the mask holding unit 3. Thereby, the solder scooping-up operation is completed (step S51).

[0118] When the solder scooping-up operation is completed, the main control unit 101 executes a mask exchange operation (step S53). First, the main control unit 101 releases the clamping state of the production mask 6B by the mask holding unit 3, and moves the printing unit 5 to transfer the mask 6B of the mask holding unit 3 to the second storage unit 42b of the mask stocker 40 (Figs. 8(a) and (b)). Next, the main control unit 101 lowers the mask stocker 40 so that the first storage unit 42a of the mask stocker 40 is disposed at the mask exchange height position (Fig. 8(c)), and the kneading mask 6A is moved from the mask stocker 40 to the mask holding unit 3 by the printing unit 5 (Figs. 9(a) and (b)). Thereafter, the mask exchange operation is completed by clamping the mask 6A in the mask holding unit 3.

[0119] When the mask exchange operation is completed, the main control unit 101 executes a solder return operation (step S55). The main control unit 101 causes the scraper 72 that has scooped up the solder to abut against a predetermined position on the upper surface of the exchanged mask 6A via the sheet T (Fig. 7(a)).

[0120] Next, the main control unit 101 sets the sheet T in the backward driving state and moves the scraper 72 to the X-axis 2 side. Thereby, the solder is moved from the upper surface 72a of the scraper 72 onto the mask 6A. That is, the solder is returned onto the 6A (Figs. 7(b) and (c)). Thereafter, the main control unit 101 stops the movement of the sheet T and moves (retracts) the scraper 72 above the mask holding unit 3. Thereby, the solder return operation is completed.

[0121] When the solder return operation is completed, the main control unit 101 executes a kneading operation of the solder S by controlling the printing unit 5 and the unit drive mechanism 10 (step S57).

[0122] Specifically, the main control unit 101 causes the squeegee 16 to contact the upper surface of the mask 6 so that the pressing surface 16a of the squeegee 16 and the upper surface of the mask 6A (mask body 60) form a predetermined angle (attack angle), and moves the squeegee 16 in this state. Thereby, the solder is rotated (kneaded) by moving the solder along the mask 6A with the squeegee 16. In this case, the main control unit 101 moves the squeegee 16 from a position near one end of the mask 6A in the X direction to a position near the other end. In this case, the squeegee 16 may be reciprocated one or more times by switching the traveling direction of the squeegee 16.

[0123] When the kneading operation of the solder S is completed, the main control unit 101 controls the solder transfer unit 7, the unit drive mechanism 10, the elevating mechanism 44, etc., to perform a solder scooping operation (step S59), a mask exchange operation (step S61), and a solder return operation (step S63). That is, after moving the solder S on the mask 6A to the upper surface 72a of the scraper 72, the mask 6A and the mask 6B in the mask stocker 40 are exchanged, and the solder S is returned onto the exchanged mask 6B.

[0124] Thereby, the kneading process of the solder S is completed. Note that the operation control of each of steps S57 to S63 by the main control unit 101 is basically the same as the operation control of each of steps S51 to S55 described above. Therefore, specific descriptions are omitted here.

[0125] Also in the case of the printing apparatus 1C of the above reference example, when the printing operation of the substrate P is interrupted for a certain period of time, a kneading process for forcibly rotating (rolling) the solder is executed. Therefore, deterioration of the solder S can be prevented.

[0126] In this case, particularly in the printing apparatus 1C of the reference example, the production mask 6B in use is replaced with the non-porous kneading mask 6A, and the solder S is moved on the kneading mask 6A by the squeegee 16. Therefore, it is possible to sufficiently knead the solder S using the entire surface of the kneading mask 6A. Accordingly, compared with the conventional printing apparatus that moves and kneads the solder within the surplus area of the mask, the kneading process of the solder S can be performed better.

[0127] In addition, in the above printing apparatus 1C, although one type of production mask 6B is stored in the mask stocker 40, it may be configured to store a plurality of types of production masks 6B. That is, the number (number of stages) of the storage sections of the mask stocker 40 may be three or more. This point is the same for the printing apparatuses 1A and 1B of the first and second embodiments.

Explanation of Reference Numerals

[0128] 1A, 1B, 1C, Screen printing apparatus 2A Printing operation section 2B Mask storage section 3 Mask holding unit 4 Substrate holding unit 5 Printing unit 6, 6A, 6B Screen mask 7 Solder transfer unit 10 Unit drive mechanism 17 Squeegee drive mechanism 40 Mask stocker 70 Scraper unit 72 Scraper 72a Upper surface 72c Tip 72d Rear end 75 Sheet movement mechanism 82 Stopper 82a Regulation surface 100 Control device 101 Main control section

Claims

1. A screen printing apparatus that performs a printing process of printing the coating material onto the substrate through an opening formed in the screen mask by moving the coating material along the upper surface of the screen mask stacked on the substrate by a squeegee, comprising: a kneading mechanism unit capable of performing a kneading process of kneading the coating material without moving it along the screen mask; a control unit that controls the kneading mechanism unit to perform the kneading process when the printing process is interrupted. The screen printing apparatus is characterized by comprising the above.

2. In the screen printing apparatus according to Claim 1, the kneading mechanism unit includes: a scooping unit including a plate-shaped scraper, a sheet disposed along the upper surface of the scraper, a stopper disposed to face the upper surface of the sheet at a predetermined position spaced from the tip of the scraper, and a sheet driving unit that moves the sheet along the scraper; a unit driving unit that moves the scooping unit; and the control unit: during the kneading process, approaches the scooping unit to the screen mask and moves the sheet in a first direction from the side of the tip toward the side of the stopper to scoop the coating material onto the sheet from the tip of the scraper (scooping operation); continuously moves the sheet in the first direction while bringing the scooped coating material into contact with the stopper to knead the coating material (kneading operation); and moves the moving direction of the sheet in a second direction opposite to the first direction to return the coating material from the scraper onto the screen mask (returning operation), and sequentially performs the above operations. The screen printing apparatus is characterized by this.

3. In the screen printing apparatus according to Claim 2, at least the contact surface of the stopper for the coating material is subjected to a low-friction treatment. The screen printing apparatus is characterized by this.

4. In the screen printing apparatus according to Claim 1, the squeegee has a flat pressing surface for pressing the coating material, and the kneading mechanism unit supports the squeegee so as to be displaceable. The control unit executes a kneading operation in which, during the kneading process, while the pressing surface is in contact with the surface of the coating material on the screen mask, the squeegee is reciprocally moved along the screen while changing the angle and height of the pressing surface along the surface with the coating material as the center. A screen printing apparatus characterized by this.

Images