Screen printing apparatus and screen printing method

Abstract

To provide a screen printing apparatus and a screen printing method capable of continuing a printing operation without degrading the print quality even when a paste has solidified.SOLUTION: A screen printing apparatus that performs a printing operation in which a paste Pst supplied onto the upper surface of a mask 14 is scraped by a squeegee 34 and the paste Pst is transferred to a substrate KB, measures the elapsed time from the time when one printing operation ends until the preparation for the next printing operation begins, changes control parameters of the squeegee to control parameters that provide lower fillability of the paste Pst into a pattern opening 14H than during the execution of the printing operation and executes a pre-printing rolling operation that rolls the paste Pst when it is detected that the elapsed time exceeds a predetermined reference time at the start of preparation for the next printing operation, and then returns the control parameters to the original control parameters to execute the next printing operation.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a screen printing apparatus and a screen printing method for transferring a paste onto a substrate through a mask having pattern openings formed therein. [Background technology]

[0002] The screen printing device performs a printing operation in which a substrate as a printing target is placed on the lower surface of a mask in which pattern openings are formed, and the squeegee is controlled to scrape up the paste supplied to the upper surface of the mask, thereby transferring the paste to the substrate through the pattern openings. In the screen printing device, the printing operation is repeatedly and continuously performed, but since the paste has thixotropy, it will solidify if the elapsed time between the end of one printing operation and the start of the next printing operation is longer than a certain time. Therefore, when the printing operation is resumed from a state in which the paste has solidified, the squeegee movement speed is reduced so that the paste is slowly filled into the pattern openings in order to avoid a situation in which a sufficient amount of paste is not filled into the pattern openings, resulting in the production of defective substrates (see, for example, Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-1555 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, as described above, when the printing operation is resumed after the paste has solidified, if a sufficient amount of paste is not filled into the pattern openings even if the squeegee movement speed is reduced, the amount of paste transferred to the board is insufficient, the print quality is reduced, and the board may become a defective product. Even if the board is not a defective product, a record remains that the printing operation was performed at a squeegee movement speed different from normal, so that the board with an insufficient amount of transferred paste may be treated as a board with insufficient print quality in product traceability.

[0005] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a screen printing apparatus and a screen printing method that are capable of continuing printing operations without deteriorating print quality even when the paste has solidified. [Means for solving the problem]

[0006] The screen printing apparatus of the present invention includes a printing operation control unit that performs a printing operation in which a substrate is placed below a mask having pattern openings formed therein, and the operation of a squeegee is controlled using control parameters to scrape up paste supplied to the upper surface of the mask, thereby transferring the paste to the substrate through the pattern openings, and a timing unit that measures the elapsed time from when one printing operation is completed to when preparation for the next printing operation is started. When the printing operation control unit detects that the elapsed time measured by the timing unit exceeds a predetermined reference time at the time when preparation for the next printing operation is started, the printing operation control unit changes the control parameters from a first control parameter corresponding to the execution of the printing operation to a second control parameter that reduces the filling of the paste into the pattern openings compared to when the printing operation is executed, and executes a pre-printing rolling operation in which the paste on the mask is rolled by controlling the squeegee with the changed second control parameter, and then returns the control parameters to the first control parameters and executes the next printing operation.

[0007] The screen printing method of the present invention includes a printing step of placing a substrate below a mask having pattern openings formed therein, and controlling the operation of a squeegee with control parameters to perform a printing operation in which paste supplied to the upper surface of the mask is scraped up and transferred to the substrate through the pattern openings, and a timing step of measuring the elapsed time from when one printing step is completed to when preparation for the next printing step is started. When it is detected that the elapsed time measured in the timing step exceeds a predetermined reference time at the time when preparation for the next printing step is started, the control parameter is changed from a first control parameter corresponding to the execution of the printing operation to a second control parameter in which the filling property of the paste in the pattern openings is lower than that in the execution of the printing step, and a pre-printing rolling step is performed in which the squeegee is controlled with the changed second control parameter to roll the paste on the mask, and then the control parameter is returned to the first control parameter and the next printing step is executed. Effect of the Invention

[0008] According to the present invention, even if the paste has solidified, the printing operation can be continued without deteriorating the print quality. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a side view of a screen printing apparatus according to a first embodiment of the present invention. [Diagram 2] FIG. 1 is a plan view of a screen printing apparatus according to a first embodiment of the present invention. [Diagram 3] 1A and 1B are side views of a squeegee unit included in a screen printing apparatus according to a first embodiment of the present invention. [Figure 4] FIG. 1 is a block diagram showing a control system of a screen printing apparatus according to a first embodiment of the present invention. [Diagram 5] 5A and 5B are side views illustrating the operation of a squeegee unit included in the screen printing apparatus according to the first embodiment of the present invention. [Figure 6]5A and 5B are side views illustrating the operation of a squeegee unit included in the screen printing apparatus according to the first embodiment of the present invention. [Figure 7] A flowchart showing the flow of a screen printing operation performed by the screen printing apparatus according to the first embodiment of the present invention. [Figure 8] FIG. 11 is a side view of a screen printing apparatus according to a second embodiment of the present invention. [Figure 9] FIG. 11 is a side view of a squeegee unit included in a screen printing apparatus according to a second embodiment of the present invention. [Figure 10] 13A and 13B are side views illustrating the operation of a squeegee unit included in a screen printing apparatus according to a second embodiment of the present invention. [Figure 11] 13A and 13B are side views illustrating the operation of a squeegee unit included in a screen printing apparatus according to a second embodiment of the present invention. [Figure 12] FIG. 11 is a side view of a screen printing apparatus according to a third embodiment of the present invention. [Figure 13] FIG. 11 is a side view of a squeegee unit included in a screen printing apparatus according to a third embodiment of the present invention. [Figure 14] 13A and 13B are side views illustrating the operation of a squeegee unit included in a screen printing apparatus according to a third embodiment of the present invention. [Figure 15] 13A and 13B are side views illustrating the operation of a squeegee unit included in a screen printing apparatus according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (Embodiment 1) FIG. 1 shows a screen printing apparatus 1 according to a first embodiment of the present invention. The screen printing apparatus 1 is an apparatus that carries in and positions a substrate KB, prints a paste Pst such as solder on an electrode pattern (not shown) provided on the upper surface of the substrate KB, and carries the substrate out. For the sake of convenience in the first embodiment, the direction in which the substrate KB is transported (the left-right direction as seen from the worker OP) is defined as the X direction, and the direction perpendicular to the X direction in the horizontal plane (the front-back direction as seen from the worker OP) is defined as the Y direction. The up-down direction is defined as the Z direction. Furthermore, in the Y direction, the front side as seen from the worker OP is defined as the front, and the back side as seen from the worker OP is defined as the rear.

[0011] 1, a substrate holder 13 is provided on a base 11 of a screen printing apparatus 1 via a substrate holder moving mechanism 12 consisting of an XYZ table mechanism or the like. A mask 14 is provided above the substrate holder 13 in a horizontal position, and a squeegee unit 15 is disposed above the mask 14.

[0012] 1, the substrate holding unit 13 includes two front and rear conveyors 21, a lifting base 22, a lifter 23, a support unit 24, and two front and rear clampers 25. The two conveyors 21 are arranged opposite each other in the Y direction (front-rear direction), and carry in a substrate KB sent from outside in the X direction (left-right direction) and position it at a predetermined working position.

[0013] The two conveyors 21 each extend in the X direction (left-right direction) and are arranged parallel to each other at a fixed interval in the Y direction (front-back direction). The two conveyors 21 run in the same direction in synchronization, support both ends of the substrate KB supplied from the outside, carry it in in the X direction, and position it at a predetermined work position. In addition, the conveyors 21 carry the substrate KB from the work position to the outside after the screen printing work is completed.

[0014] The lifting base 22 is made of a plate-like member extending along the XY plane, and is located between the two conveyors 21. The lifting base 22 is moved in the X, Y, and Z directions by the substrate holder moving mechanism 12.

[0015] The lifter 23 is attached to the lifting base 22. The lifter 23 raises and lowers (moves in the Z direction) the lower support unit 24 relative to the lifting base 22.

[0016] 1, the support unit 24 includes a base 24a, which is a block-shaped member extending along the XY plane, and a plurality of support pins 24b attached to the upper surface of the base 24a. When the support unit 24 is raised by the lifter 23 with the board KB positioned at the working position by the conveyor 21, the upper ends of the plurality of support pins 24b come into contact with the lower surface of the board KB in the process, and the support unit pushes up the board KB while maintaining that state.

[0017] The two front and rear clampers 25 are provided at the upper ends of two clamper support parts 22S that extend upward from the front and rear ends of the lift base 22. The two clampers 25 are each movable in the Y direction (in the direction approaching or moving away from each other) and clamp and hold the substrate KB supported by the support unit 24 from the sides (front-rear direction).

[0018] 2, the mask 14 is made of a plate-like member and has a rectangular shape. The periphery of the mask 14 is supported by a rectangular frame 14W. In the center of the mask 14, pattern openings 14H are formed in an arrangement corresponding to the electrode pattern of the substrate KB.

[0019] 3(a) and (b), the squeegee unit 15 includes a unit base 31 that is provided so as to be movable in the Y direction, and two squeegee lift cylinders (front squeegee lift cylinder 32A and rear squeegee lift cylinder 32B) provided on the unit base 31. The piston rod 32R of the front squeegee lift cylinder 32A and the piston rod 32R of the rear squeegee lift cylinder 32B each extend below the unit base 31, and a squeegee 34 is attached to the lower end of these two piston rods 32R via a link mechanism 33. The squeegee 34 includes a front squeegee 34A located on the near side (front) as viewed from the operator OP, and a rear squeegee 34B located on the far side (rear) as viewed from the operator OP. The front squeegee 34A has a shape that is inclined so that it approaches the near side from the far side as it goes downward, and the rear squeegee 34B has a shape that is inclined so that it moves away from the near side to the far side as it goes downward. The squeegee unit 15 is freely movable in the Y direction (arrow E shown in FIGS. 1 and 2) by a squeegee unit moving mechanism 15M constituted by a ball screw mechanism or the like.

[0020] 3(a) and (b), the height and inclination (inclination around an axis along the X-direction) of the squeegee 34 can be changed by adjusting the downward projection length of the piston rod 32R of each of the front squeegee lift cylinder 32A and the rear squeegee lift cylinder 32B from the standby position (FIG. 1) where the entire squeegee 34 is in a horizontal position. In detail, the squeegee 34 can be brought into a forward lowered position by making the projection length of the piston rod 32R of the front squeegee lift cylinder 32A longer than the projection length of the piston rod 32R of the rear squeegee lift cylinder 32B (FIG. 3(a)). Conversely, the squeegee 34 can be brought into a rear lowered position by making the projection length of the piston rod 32R of the rear squeegee lift cylinder 32B longer than the projection length of the piston rod 32R of the front squeegee lift cylinder 32A (FIG. 3(b)).

[0021] When the squeegee 34 is in a forward-lowering position (FIG. 3(a)), the lower end of the front squeegee 34A can be brought into contact with the upper surface of the mask 14, allowing the front squeegee 34A to scrape up the paste Pst. In this case, the print head 15 (squeegee 34) is moved from the front to the rear. When the squeegee 34 is in a rear-lowering position (FIG. 3(b)), the lower end of the rear squeegee 34B can be brought into contact with the upper surface of the mask 14, allowing the rear squeegee 34B to scrape up the paste Pst. In this case, the print head 15 (squeegee 34) is moved from the rear to the front.

[0022] As described above, by adjusting the downward protruding length of the piston rod 32R of each of the front squeegee lifting cylinder 32A and the rear squeegee lifting cylinder 32B, the squeegee 34 can be placed in a forward-lowered or rear-lowered position. Furthermore, by fine-tuning the protruding lengths of these two piston rods 32R, the attack angle of the front squeegee 34A in the forward-lowered position can be set to a desired value, and the attack angle of the rear squeegee 34B in the rear-lowered position can be set to a desired value.

[0023] Here, the attack angle (symbolized as Θ) refers to the angle formed between paste scraping surface 34M of front squeegee 34A and the horizontal plane (upper surface of mask 14) when squeegee 34 is in a forward lowered position as shown in Fig. 3(a). Alternatively, it refers to the angle formed between paste scraping surface 34M of rear squeegee 34B and the horizontal plane (upper surface of mask 14) when squeegee 34 is in a rear lowered position as shown in Fig. 3(b). In this way, the two squeegee lifting cylinders (front squeegee lifting cylinder 32A and rear squeegee lifting cylinder 32B), which are means for changing the inclination of squeegee 34, function as an attack angle setting mechanism that sets (changes) attack angle Θ of squeegee 34 with respect to mask 14.

[0024] 4, the control device 40 provided in the screen printing apparatus 1 includes a printing operation control unit 41 and a storage unit 42. The printing operation control unit 41 controls the operation of each unit constituting the screen printing apparatus 1. Specifically, it controls the transport and positioning operation of the substrate KB by the conveyor 21, the lifting and lowering operation of the support unit 24 by the lifter 23, the clamping operation of the substrate KB by the two front and rear clampers 25, and the movement operation of the substrate holding unit 13 in the XYZ directions by the substrate holding unit movement mechanism 12. The printing operation control unit 41 also controls the setting operation of the attack angle Θ of the squeegee 34 by the front squeegee lifting and lowering cylinder 32A and the rear squeegee lifting and lowering cylinder 32B, and the movement operation of the squeegee unit 15 by the squeegee unit movement mechanism 15M.

[0025] The storage unit 42 stores an execution program for the screen printing operation executed by the printing operation control unit 41. The printing operation control unit 41 reads the execution program for the screen printing operation from the storage unit 42 and controls the operation of each unit. As a result, each unit operates according to the execution program, and the screen printing apparatus 1 executes a printing operation of printing the paste Pst on the substrate KB through the mask 14.

[0026] In a printing operation, first, the conveyor 21 is operated to carry in the board KB and position the board KB at the working position. Once the board KB is positioned at the working position, the lifter 23 lifts the lower support unit 24. As the lower support unit 24 rises, it lifts the board KB and moves it away from the conveyor 21. Once the board KB has moved away from the conveyor 21, the clamper 25 clamps the board KB. When the board KB is clamped by the clamper 25, the top surface of the board KB and the top surface of the clamper 25 are located at the same height.

[0027] Once the clampers 25 have clamped the substrate KB, the substrate-holding-part moving mechanism 12 raises the entire substrate holding part 13, bringing the upper surface of the substrate KB into contact with the lower surface of the mask 14. When the substrate KB comes into contact with the lower surface of the mask 14, the upper surfaces of the two clampers 25 also come into contact with the lower surface of the mask 14 (FIG. 1).

[0028] When the upper surface of the substrate KB comes into contact with the lower surface of the mask 14, the squeegee unit 15 performs a rolling operation by moving the squeegee 34 over the mask 14 to scrape and roll the paste Pst on the mask 14. The rolling operation is performed with the paste Pst supplied to the upper surface of the mask 14. Therefore, if the paste Pst has not been supplied to the upper surface of the mask 14 (or if there is insufficient paste Pst), the paste Pst is supplied in advance. The paste Pst is supplied manually by an operator OP, or automatically by a paste supplying device (not shown).

[0029] The printing operation control unit 41 alternately brings the two squeegees 34 arranged at the front and rear into contact with the mask 14 and moves them in the Y direction, thereby moving the paste Pst back and forth between two areas (hereinafter referred to as "clamper contact areas") on the mask 14 where the upper surfaces of the two clampers 25 are in contact. For this reason, the paste Pst is supplied to one of the two clamper contact areas on the mask 14. Here, it is assumed that the paste Pst is first supplied to the front clamper contact area.

[0030] Prior to performing the rolling operation, the printing operation control unit 41 sets the control parameters for controlling the operation of the squeegee 34 (specifically, the attack angle Θ and the movement speed V of the squeegee 34) to the first control parameters corresponding to the execution of the printing operation. The first control parameters are control parameters suitable for printing the paste Pst through the pattern opening 14H of the mask 14, and are control parameters that allow a sufficient amount of paste Pst to be filled into the pattern opening 14H of the mask 14 by the rolling operation, thereby transferring a sufficient amount of paste Pst to the electrode pattern of the substrate KB. Hereinafter, the attack angle Θ of the squeegee 34 when the control parameters are set to the first control parameters is referred to as the "attack angle Θ1 during printing operation," and the movement speed V of the squeegee 34 when the control parameters are set to the first control parameters is referred to as the "movement speed V1 during printing operation."

[0031] After setting the control parameters to the first control parameters, the printing operation control unit 41 sets the attack angle Θ of the squeegee to be used in the rolling operation from among the front squeegee 34A and the rear squeegee 34B (hereinafter referred to as the "used squeegee 34U") to the "attack angle during printing operation Θ1". Here, the "used squeegee 34U" is the front squeegee 34A when the paste Pst is supplied to the front clamper contact area, and is the rear squeegee 34B when the paste Pst is supplied to the rear clamper contact area. Here, as described above, the paste Pst is supplied to the front clamper contact area first, so the first used squeegee 34U is the front squeegee 34A.

[0032] As described above, the attack angle Θ of the squeegee in use 34U is set by adjusting the downward projection length of the piston rod 32R of each of the front squeegee lifting cylinder 32A and the rear squeegee lifting cylinder 32B. The attack angle Θ1 during printing operation is set to a value between 58 and 60°, for example.

[0033] After setting the attack angle Θ of the squeegee 34U in use to the attack angle Θ1 during printing operation, the printing operation control unit 41 lowers the squeegee 34U in use by the front squeegee lifting cylinder 32A and the rear squeegee lifting cylinder 32B. Then, when the lower end of the squeegee 34U in use comes into contact with the upper surface of the mask 14, the lowering operation of the squeegee 34U in use is stopped (FIG. 5(a)).

[0034] When the lower end of the used squeegee 34U comes into contact with the upper surface of the mask 14 and the downward movement of the used squeegee 34U is stopped, the printing operation control unit 41 causes the squeegee unit moving mechanism 15M to move the squeegee unit 15 in the Y direction at the printing operation movement speed V1 (arrow E1 shown in FIG. 5(a)). At this time, the direction in which the squeegee unit 15 is moved is rearward if the used squeegee 34U is the front squeegee 34A, and is forward if the used squeegee 34U is the rear squeegee 34B.

[0035] When the squeegee 34U in use is moved in the Y direction (rearward) as described above, the paste Pst on the mask 14 is rolled rearward and moves from the front clamper contact area to the rear clamper contact area. During this time, the paste Pst fills the pattern openings 14H of the mask 14 and is transferred to the electrode pattern of the substrate KB. This rolling operation is performed with the control parameters set to first control parameters suitable for the printing operation, so that a sufficient amount of paste Pst fills the pattern openings 14H of the mask 14 and a sufficient amount of paste Pst is transferred to the electrode pattern of the substrate KB.

[0036] Once the paste Pst has been transferred to the electrode pattern of the substrate KB by the rolling operation, the substrate-holding-part moving mechanism 12 lowers the substrate-holding part 13 to separate the substrate KB from the mask 14 (so-called plate separation). Once the substrate KB has been separated from the mask 14, the conveyor 21 is activated to transport the substrate KB to the outside. This completes the printing operation for one substrate KB.

[0037] As described above, after the front squeegee 34A performs a rolling motion in which it moves backward in one printing operation, the rear squeegee 34B performs a rolling motion in which it moves forward in the next printing operation (arrow E2 shown in FIG. 5(b)). In this manner, the screen printing apparatus 1 alternately brings the two squeegees (front squeegee 34A and rear squeegee 34B) arranged in front and behind into contact with the mask 14 and moves them in the Y direction, repeating the printing operation to successively produce boards KB on which the paste Pst is printed.

[0038] As described above, the screen printing apparatus 1 repeatedly executes printing operations, and if the time that has elapsed since the end of one printing operation exceeds a predetermined reference time, it is determined that the paste Pst on the mask 14 has solidified. Then, if it is determined that the paste Pst has solidified, the next printing operation is not performed (the printing operation is resumed) while the paste Pst is in the solidified state, but the solidified paste Pst is softened before the next printing operation is performed. This will be explained below.

[0039] The control device 40 provided in the screen printing apparatus 1 includes a timing unit 43 as shown in Fig. 4. The timing unit 43 is made up of a timer, and measures the elapsed time from when one printing operation by the printing operation control unit 41 ends to when preparation for the next printing operation starts (i.e., the time during which the paste Pst is not moved on the mask 14).

[0040] Here, "when the printing operation ends", which is the start of the measurement of the elapsed time by the timer 43, can be, for example, when the rolling operation by the squeegee 34 ends (when the movement of the squeegee in the Y direction is stopped). Alternatively, it can be when the squeegee 34 is lifted by the two squeegee lift cylinders (front squeegee lift cylinder 32A and rear squeegee lift cylinder 32B) and returns to the above-mentioned standby position (FIG. 1). Also, "when preparation for the next printing operation begins", which is the end of the measurement of the elapsed time by the timer 43, can be, for example, when the substrate KB held by the substrate holding unit 13 comes into contact with the lower surface of the mask 14 by the substrate holding unit moving mechanism 12.

[0041] The "reference time" to be compared with the elapsed time measured by the timer 43 is the time from when the movement (rolling motion) of the paste Pst on the mask 14 stops to when the paste Pst is considered to start solidifying. This reference time is usually set to a time between 10 and 30 minutes. The value of the reference time is stored in the memory 42.

[0042] When the printing operation control unit 41 detects that the elapsed time measured by the timer unit 43 exceeds a predetermined reference time at the time of starting preparation for the next printing operation after finishing one printing operation, the printing operation control unit 41 changes the control parameters from the first control parameters corresponding to the execution of the printing operation to the second control parameters. The second control parameters are control parameters that reduce the filling property of the paste Pst in the pattern openings 14H compared to the execution of the printing operation. Then, the printing operation control unit 41 controls the squeegee 34 with the changed second control parameters to execute an operation of rolling and softening the paste Pst on the mask 14 (pre-printing rolling operation), and then returns the control parameters to the first control parameters to execute the next printing operation.

[0043] The above pre-printing rolling operation is different from the printing operation in that it is not intended to fill the pattern openings 14H with the paste Pst on the mask 14 and transfer the paste Pst to the substrate KB, but rather to soften the solidified paste Pst by rolling it on the mask 14. Hereinafter, the attack angle Θ of the squeegee 34 (squeegee 34U used) when the control parameter is set to the second control parameter will be referred to as the "attack angle Θ2 during pre-printing rolling operation," and the moving speed V of the squeegee 34 (squeegee unit 15) when the control parameter is set to the second control parameter will be referred to as the "moving speed V2 during pre-printing rolling operation."

[0044] The printing operation control unit 41 sets the attack angle Θ2 during the pre-printing rolling operation to a value greater than the attack angle Θ1 during the printing operation (Θ2>Θ1. For example, Θ2=70°). This is because the larger the attack angle Θ of the squeegee 34, the less the amount of paste Pst that is transferred to the substrate KB through the pattern opening 14H of the mask 14. This makes it possible to minimize the effect of the pre-printing rolling operation on the subsequent printing operation.

[0045] Furthermore, the printing operation control unit 41 sets the pre-printing rolling operation movement speed V2 to a value greater than the printing operation movement speed V1 (V2>V1). This is because the greater the movement speed V of the squeegee 34, the less the amount of paste Pst that is transferred to the substrate KB through the pattern openings 14H of the mask 14 can be. This makes it possible to minimize the effect of the pre-printing rolling operation on the subsequent printing operation.

[0046] When performing pre-printing rolling operation, the printing operation control unit 41 sets the attack angle Θ of the squeegee 34U in use to the attack angle Θ2 during pre-printing rolling operation, abuts the lower end of the squeegee 34U in use on the upper surface of the mask 14, and then moves the squeegee unit 15 (i.e., the squeegee 34U in use) in the Y direction at the pre-printing rolling operation movement speed V2 (FIG. 6(a)). At this time, the direction in which the squeegee unit 15 is moved is rearward when the squeegee 34U in use is the front squeegee 34A, and is forward when the squeegee 34U in use is the rear squeegee 34B.

[0047] When the pre-printing rolling operation is performed by moving the squeegee 34U in use as described above, the paste Pst solidified on the mask 14 is rolled by the squeegee 34U in use, softens, and returns to its original state. In this pre-printing rolling operation, the paste Pst rolled on the mask 14 does not fill the pattern opening 14H very much, and is hardly transferred to the substrate KB. For this reason, the pre-printing rolling operation has almost no effect on the subsequent printing operation (the first printing operation after the printing operation is resumed) in terms of filling the pattern opening 14H with the paste Pst (and therefore the transfer of the paste Pst to the substrate KB). Therefore, by returning the control parameters to the first control parameters after the pre-printing rolling operation is completed and performing the printing operation, the printing operation can be continued without considering the fact that the paste Pst has temporarily solidified.

[0048] In a configuration such as the screen printing apparatus 1 in embodiment 1 described here, in which the squeegee unit 15 has two squeegees 34 and the two squeegees 34 are alternately brought into contact with the mask to repeat the printing operation, when the printing operation control unit 41 detects that the elapsed time exceeds the reference time, it first performs a pre-printing rolling operation with one of the two squeegees 34 (front squeegee 34A and rear squeegee 34B) (Figure 6(a)), and then performs the printing operation with the other of the two squeegees 34 (Figure 6(b)).

[0049] However, this is only an example, and when the printing operation control unit 41 detects that the elapsed time exceeds the reference time, it may set the number of repetitions of the pre-printing rolling operation according to the length of the elapsed time measured by the timer unit 43, and perform the pre-printing rolling operation the set number of times in succession before performing the printing operation. In this case, for example, if the elapsed time is less than 10 minutes, the number of pre-printing rolling operations is set to one, if the elapsed time is 10 minutes or more but less than 20 minutes, the number of pre-printing rolling operations is set to two, and if the elapsed time is 20 minutes or more, the number of pre-printing rolling operations is set to three, and after performing the pre-printing rolling operation by alternately bringing the two squeegees 34 into contact with the mask 14 one to three times, the printing operation (the first printing operation after the printing operation is resumed) is performed in the next rolling operation.

[0050] FIG. 7 is a flowchart showing the flow of the screen printing operation performed by the screen printing apparatus 1 in the first embodiment. Based on this flowchart, the flow of control (screen printing method) performed by the printing operation control unit 41 will be described. First, the printing operation control unit 41 sets the control parameters to the first control parameters and starts the printing operation for one board KB (step ST1), and when the printing operation is completed (step ST2), causes the timer unit 43 to start timing (step ST3). Then, when preparation for the next printing operation is started (step ST4), the timer unit 43 stops timing (step ST5), and compares the elapsed time (the elapsed time from the completion of one printing operation to the start of preparation for the next printing operation) measured by the timer unit 43 with the reference time read from the storage unit 42 to determine whether the elapsed time exceeds the reference time (step ST6). If the elapsed time does not exceed the reference time, the process returns to step ST1 to execute the printing operation, and if the elapsed time exceeds the reference time, the process executes the pre-printing rolling operation (step ST7), and then returns to step ST1 to execute (resume) the printing operation.

[0051] Thus, the screen printing method by the screen printing apparatus 1 in the first embodiment includes a printing step (steps ST1 to ST2) of placing the substrate KB below the mask 14 in which the pattern openings 14H are formed, controlling the operation of the squeegee 34 with the control parameters to scrape up the paste Pst supplied to the upper surface of the mask 14, and transferring the paste Pst to the substrate KB through the pattern openings 14H, and a timing step (steps ST3 to ST5) of measuring the elapsed time from the end of one printing step to the start of preparation for the next printing step. Then, when it is detected that the elapsed time measured in the timing step exceeds a predetermined reference time at the time when preparation for the next printing step is started (step ST6), the control parameter is changed from a first control parameter corresponding to the execution of the printing step to a second control parameter that reduces the filling property of the paste Pst in the pattern openings 14H compared to the execution of the printing step. Then, after executing a pre-printing rolling process in which the paste Pst on the mask 14 is rolled by controlling the squeegee 34 with the changed second control parameters (step ST7), the control parameters are returned to the first control parameters and the next printing process is executed (steps ST1 to ST2).

[0052] Thus, the screen printing apparatus 1 in the first embodiment is configured to include a printing operation control unit 41 that performs a printing operation in which the substrate KB, which is a printing object, is placed below the mask 14 in which the pattern openings 14H are formed, and the operation of the squeegee 34 is controlled by the control parameters to scrape up the paste Pst supplied to the upper surface of the mask 14, thereby transferring the paste Pst to the substrate KB through the pattern openings 14H, and a timing unit 43 that measures the elapsed time from the end of one printing operation to the start of preparation for the next printing operation. When the printing operation control unit 41 detects that the elapsed time measured by the timing unit 43 exceeds a predetermined reference time at the time of starting preparation for the next printing operation, the control parameter is changed from a first control parameter corresponding to the execution of the printing operation to a second control parameter that reduces the filling property of the paste Pst in the pattern openings 14H compared to the execution of the printing operation, and a pre-printing rolling operation is performed in which the paste Pst on the mask 14 is rolled by controlling the squeegee 34 with the changed second control parameter, and then the control parameter is returned to the first control parameter to execute the next printing operation.

[0053] Thus, in the screen printing apparatus 1 (screen printing method) in the first embodiment, when the paste Pst on the mask 14 temporarily solidifies, a pre-printing rolling operation is performed only for the purpose of rolling the solidified paste Pst before the next printing operation is performed (resuming), and the solidified paste Pst is softened and restored to its original state. Therefore, according to the screen printing apparatus 1 in the first embodiment, the printing operation can be continued without deteriorating the printing quality. Here, since the pre-printing rolling operation is merely an operation for softening the solidified paste Pst and is not a printing operation (the printing operation is performed after the pre-printing rolling operation), it is not necessary to record the pre-printing rolling operation in the product traceability. Therefore, the board KB on which the pre-printing rolling operation is applied and then the printing operation is performed is not treated as a board KB with insufficient reliability in the product traceability.

[0054] (Embodiment 2) Next, a second embodiment of the present invention will be described. Fig. 8 shows a screen printing apparatus 1A in the second embodiment. The screen printing apparatus 1A in the second embodiment is almost the same as the screen printing apparatus 1 in the first embodiment, except for the configuration of the squeegee unit (referred to as "15A").

[0055] Squeegee unit 15A included in screen printing apparatus 1A in embodiment 2 includes unit base 31 similar to that in embodiment 1, and two squeegee lifting cylinders 132, one at the front and one at the back, provided on unit base 31 (FIGS. 8 and 9). Piston rods 132R of each of the two squeegee lifting cylinders 132 extend below unit base 31, and a squeegee 134 is attached to the lower end of each piston rod 132R via an attack angle setting portion 133.

[0056] The squeegee lift cylinder 132 located at the front moves its piston rod 132R back and forth to lift and lower the front squeegee 134, and the squeegee lift cylinder 132 located at the rear moves its piston rod 132R back and forth to lift and lower the rear squeegee 134. The front and rear squeegees 34 are each moved between a standby position (see the position of the right squeegee 134 in FIG. 9) and a lowered position (see the position of the left squeegee 134 in FIG. 9) lowered from the standby position. When in the lowered position, the squeegee 134 abuts its lower end against the upper surface of the mask 14. The squeegee unit 15A is moved in the Y direction by the squeegee unit moving mechanism 15M, as in the first embodiment.

[0057] 9, the attack angle setting unit 133 is attached to the lower end of the piston rod 132R of the squeegee lifting cylinder 132. The attack angle setting unit 133 is composed of, for example, a motor, and sets (changes) the attack angle Θ of the squeegee 134 (the front squeegee 134 or the rear squeegee 134) by rotating the entire squeegee 134 about a rotation axis extending in the X direction along the upper edge of the squeegee 134.

[0058] In the screen printing apparatus 1A in the second embodiment, the printing operation control unit 41 performs a pre-printing rolling operation on one of the two paste scraping surfaces 134M (the paste scraping surface 134M of the squeegee 134U used) (arrow E1 shown in FIG. 10(a)), and then performs a printing operation on the other of the two paste scraping surfaces 134M (arrow E2 shown in FIG. 10(b)). Then, the time elapsed from the end of one printing operation to the start of preparation for the next printing operation is measured by the timer unit 43 in the same manner as in the first embodiment, and when the preparation for the next printing operation is started, if the elapsed time measured by the timer unit 43 does not exceed the reference time, the printing operation is continued as it is, but if it is detected that the elapsed time measured by the timer unit 43 exceeds the reference time, the printing operation control unit 41 performs a pre-printing rolling operation on one of the two paste scraping surfaces 134M (arrow E1 shown in FIG. 11(a)), and then performs the next printing operation on the other of the two paste scraping surfaces 134M (arrow E2 shown in FIG. 11(b)).

[0059] In the screen printing apparatus 1A of embodiment 2, as in the case of the screen printing apparatus 1 of embodiment 1, when the printing operation control unit 41 detects that the elapsed time measured by the timing unit 43 exceeds a reference time at the time when preparation for the next printing operation begins, it may be configured to set the number of repetitions of the pre-printing rolling operation in accordance with the length of the measured elapsed time, and to perform the pre-printing rolling operation the set number of times in succession before performing the next printing operation.

[0060] (Embodiment 3) Next, a third embodiment of the present invention will be described. Fig. 12 shows a screen printing apparatus 1B in the third embodiment. The screen printing apparatus 1B in the third embodiment is almost the same as the screen printing apparatus 1A in the second embodiment, except for the configuration of the squeegee unit (referred to as "15B").

[0061] The squeegee unit 15B provided in the screen printing apparatus 1B in embodiment 3 differs from the squeegee unit 15A provided in the screen printing apparatus 1A in embodiment 2 in that the squeegee 134 has two paste scraping surfaces 134M that are used by switching the direction of inclination relative to the mask 14 depending on the direction of movement of the squeegee 134 (Figure 13).

[0062] As described above, screen printing apparatus 1B in the third embodiment has two paste scraping surfaces 134M in which one squeegee 134 is used by switching the direction of inclination, and since there is only one squeegee 134 itself, there is also one squeegee lifting cylinder 132 and one attack angle setting unit 133 that sets (changes) the attack angle Θ of squeegee 134. And, both the switching of the direction of the inclination of squeegee 134 with respect to mask 14 and the setting of attack angle Θ are performed by one attack angle setting unit 133 (FIG. 13).

[0063] In the screen printing apparatus 1B in the third embodiment, the printing operation control unit 41 performs a pre-printing rolling operation on one of the two paste scraping surfaces 134M (arrow E1 shown in FIG. 14(a)), and then performs a printing operation on the other of the two paste scraping surfaces 134M (arrow E2 shown in FIG. 14(b)). Then, the timer unit 43 measures the elapsed time from when one printing operation is completed to when preparation for the next printing operation is started, and if the elapsed time measured by the timer unit 43 does not exceed the reference time at the time when preparation for the next printing operation is started, the printing operation is continued as it is, but if it is detected that the elapsed time measured by the timer unit 43 exceeds the reference time, the printing operation control unit 41 performs a pre-printing rolling operation on one of the two paste scraping surfaces 134M (arrow E1 shown in FIG. 15(a)), and then performs the next printing operation on the other of the two paste scraping surfaces 134M (arrow E2 shown in FIG. 15(b)).

[0064] In the screen printing apparatus 1B of embodiment 3, as in the case of the screen printing apparatus 1 of embodiment 1 and the screen printing apparatus 1A of embodiment 2, when the printing operation control unit 41 detects that the elapsed time measured by the timing unit 43 exceeds a reference time at the time when preparation for the next printing operation begins, it may be configured to set the number of repetitions of the pre-printing rolling operation in accordance with the length of the measured elapsed time, and to perform the pre-printing rolling operation the set number of times in succession before performing the next printing operation.

[0065] As described above, in the screen printing apparatus (screen printing method) in the first to third embodiments, the elapsed time from the end of one printing operation to the start of preparation for the next printing operation is measured, and when it is detected that the measured elapsed time exceeds a predetermined reference time at the start of preparation for the next printing operation, the control parameters for controlling the squeegees 34, 134 are changed from the first control parameters corresponding to the execution of the printing operation to the second control parameters that make the filling property of the paste Pst in the pattern openings 14H lower than that during the execution of the printing operation, and a pre-printing rolling operation is executed in which the paste Pst on the mask 14 is rolled by controlling the squeegees 34, 134 with the changed second control parameters, and after the solidified paste Pst is softened, the control parameters are returned to the original control parameters (first control parameters) to execute (resume) the next printing operation. Therefore, even if the elapsed time from the end of one printing operation to the start of preparation for the next printing operation becomes long and the paste Pst solidifies, the printing operation can be continued without deteriorating the print quality.

[0066] Up to this point, the first to third embodiments of the present invention have been described, but the present invention is not limited to the above, and various modifications and the like are possible. For example, in the first to third embodiments described above, the squeegee units 15, 15A, and 15B are configured to be able to perform rolling motion in either direction along the moving direction (Y direction), but the present invention can also be applied to a configuration in which the rolling motion is performed only in one direction along the moving direction. Also, in the above-mentioned embodiments, the substrate on which the paste Pst is printed through the mask 14 is the substrate KB, but the substrate is not necessarily limited to the substrate KB. [Industrial Applicability]

[0067] Provided is a screen printing device and a screen printing method that are capable of continuing a printing operation without deteriorating the print quality even when a paste has solidified. [Explanation of symbols]

[0068] 1,1A,1B Screen printing device 14 Mask 14H pattern opening 15, 15A, 15B Squeegee unit 34,134 Squeegee 34A Front squeegee 34B Rear squeegee 34M, 134M Paste scraping surface 41 Printing operation control unit 43 Timing section 133 Attack angle setting section Θ Angle of attack V Movement speed Pst paste KB substrate (printing material)

Claims

1. a printing operation control unit that executes a printing operation in which a substrate is placed below a mask having pattern openings formed therein, and a squeegee operation is controlled by a control parameter to scrape up paste supplied to an upper surface of the mask, thereby transferring the paste to the substrate through the pattern openings; A timer unit that measures the elapsed time from the end of one printing operation to the start of preparation for the next printing operation, When the printing operation control unit detects that the elapsed time measured by the timing unit exceeds a predetermined reference time at the time preparation for the next printing operation is started, the printing operation control unit changes the control parameter from a first control parameter corresponding to the execution of the printing operation to a second control parameter that reduces the filling of the paste into the pattern openings compared to the execution of the printing operation, performs a pre-printing rolling operation in which the paste on the mask is rolled by controlling the squeegee with the changed second control parameter, and then returns the control parameter to the first control parameter and executes the next printing operation.

2. The screen printing apparatus of claim 1 , wherein an attack angle of the squeegee corresponding to the second control parameter is greater than the attack angle corresponding to the first control parameter.

3. The screen printing apparatus according to claim 1 , wherein a moving speed of the squeegee corresponding to the second control parameter is greater than a moving speed of the squeegee corresponding to the first control parameter.

4. The screen printing device of any one of claims 1 to 3, further comprising: two squeegees; and the printing operation control unit is configured to alternately contact the two squeegees against a mask to repeat the printing operation; and when it is detected that the elapsed time measured by the timing unit exceeds the reference time at the time preparation for the next printing operation begins, a pre-printing rolling operation is performed with one of the two squeegees, and then the next printing operation is performed with the other of the two squeegees.

5. The squeegee has two paste scraping surfaces that are used by switching the direction of inclination relative to the mask depending on the direction of movement, and the printing operation control unit performs one printing operation on one of the two paste scraping surfaces and then performs the next printing operation on the other of the two paste scraping surfaces.When it is detected that the elapsed time measured by the timing unit exceeds the reference time at the time preparation for the next printing operation is started, a pre-printing rolling operation is performed on one of the two paste scraping surfaces, and then the next printing operation is performed on the other of the two paste scraping surfaces. The screen printing device according to any one of claims 1 to 3.

6. 2. The screen printing device according to claim 1, wherein when the printing operation control unit detects that the elapsed time measured by the timing unit exceeds the reference time at the time when preparation for the next printing operation is started, the printing operation control unit sets a number of repetitions of the pre-printing rolling operation according to the length of the measured elapsed time, and performs the pre-printing rolling operation the set number of times in succession before performing the next printing operation.

7. a printing step of placing a substrate below a mask having pattern openings formed therein, and controlling the operation of a squeegee with control parameters to scrape up paste supplied to an upper surface of the mask, thereby transferring the paste to the substrate through the pattern openings; A timing step of measuring an elapsed time from the end of one printing step to the start of preparation for the next printing step, a second control parameter that reduces the filling ability of the paste into the pattern openings compared to when the printing process is performed, and a pre-printing rolling process is performed in which the squeegee is controlled with the changed second control parameter, and then the control parameter is returned to the first control parameter and the next printing process is performed.

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