JP2018024121A - Screen printing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screen printing apparatus, in which viscous materials are sequentially printed on a substrate in two screen printing parts, and the occurrence of a printing failure due to an adhesion of the viscous material to a mask is suppressed.SOLUTION: A screen printing apparatus comprises: a first screen printing part 3A equipped with a small part mask 6 and a first squeegee unit 4A for performing a first printing process upon a substrate 5; a second screen printing part 3B equipped with a large part mask 7 and a second squeegee unit 4B for performing a second printing process upon the substrate subjected to said first printing process; and a mask recognition camera 24 or a substrate recognition camera 15 for imaging the designated point which has been designated in advance as the estimated position of a solder paste. By detecting the presence or absence of the stick of the solder paste on the basis of the image of said designated point of the large part mask 7 or the substrate 5, it is decided whether or not the printing failure has occurred.SELECTED DRAWING: Figure 13

Description

  The present invention relates to a screen printing apparatus that sequentially prints a viscous material on a substrate in two screen printing units.

  2. Description of the Related Art Screen printing apparatuses that apply a viscous material such as solder paste on a printed board using a mask having a pattern opening are known. In the screen printing apparatus, contamination of the mask becomes a problem. When the solder paste adheres to the surface of the mask facing the substrate, the solder paste is printed at an unintended position on the substrate, causing a printing failure.

  Patent Document 1 discloses a screen printing apparatus that detects a stain on the back surface (substrate facing surface) of a mask and performs a cleaning process on the mask when the stain is detected. In this apparatus, an image of the back surface of the mask is taken, and the presence or absence of solder paste that wraps around the back surface of the mask is detected from the image. When the solder paste is detected, the mask back surface is cleaned. Patent Document 2 also discloses a screen printing apparatus that captures an image of the back surface of a mask in order to detect clogging of a pattern opening.

JP 2000-309089 A Japanese Patent Laid-Open No. 5-229109

  In some types of screen printing apparatuses, solder paste may be sequentially printed on a substrate in two screen printing units. For example, first, a first printing process for printing a solder pattern for a small component on a substrate using a thin mask is performed, and then a substrate for a large component using a thick mask is performed on the substrate after the first printing process. There is a sequential printing type screen printing apparatus that performs a second printing process for printing a solder pattern. In this type of screen printing apparatus, when an inappropriate first printing process is performed, a solder paste is printed on a portion that should not be printed on the substrate, and in the second printing process, the solder paste is applied to the back surface of the mask. May adhere. In this case, there arises a problem that the subsequent second printing process is hindered, that is, a defective substrate is generated.

  An object of the present invention is to provide a screen printing apparatus that can suppress the occurrence of printing defects due to adhesion of viscous material to a mask in a screen printing apparatus that sequentially prints viscous material on a substrate in two screen printing units. There is to do.

  A screen printing apparatus according to an aspect of the present invention includes a first mask and a first printing unit, a first screen printing unit that performs a first printing process for screen printing a viscous material on a substrate, a second mask, A second screen printing section that includes a second printing section and that performs a second printing process for screen printing a viscous material on the substrate on which the first printing process has been performed; and the first printing process or the second printing process. Based on the image acquired by the imaging unit and an image acquired by the imaging unit, whether or not the viscous material exists at the specified point A determination unit for determining.

  According to this screen printing apparatus, the imaging unit images the designated point as the predicted adhesion position of the viscous material. The estimated adhesion position is, for example, a location where the viscous material adheres when an assumed erroneous printing process is performed, or a location where the viscous material adheres when a regular printing process is performed. It is. And the determination part determines whether the said viscous material exists in a designated point. Based on the presence or absence of the viscous material at the designated point, it is possible to grasp whether an erroneous printing process or a regular printing process has been performed. Therefore, it is possible to take various measures for preventing the occurrence of printing defects based on the determination result of the determination unit.

  In the screen printing apparatus, the designated point is a specific position on the back surface of the second mask, and the imaging unit is configured to image the specific position of the second mask after the second printing process. desirable.

  According to this screen printing apparatus, the determination unit can determine whether or not the viscous material is attached to the back surface of the second mask. For example, when the first printing process is performed in a state where the first mask is not attached to the regular position, the positions of the print pattern by the first printing process on the substrate and the escape pattern provided in the second mask are The viscous material adheres to the back surface of the second mask (the surface facing the substrate). In addition, the attachment mistake of the first mask generally occurs when the first mask is reversed and attached to the regular position, and when the mistake occurs, it is predicted where the viscous material will adhere to the second mask. it can. Therefore, it is possible to detect an error in the first printing process by detecting the adhesion of the viscous material to a specific position on the back surface of the second mask, and it is possible to prevent the occurrence of subsequent printing defects.

  In this case, the cleaning unit further includes a cleaning unit that cleans the back surface of the second mask, and the cleaning unit detects the second mask when the determination unit determines that the viscous material is present on the back surface of the second mask. It is desirable to clean the back side.

  According to this screen printing apparatus, the viscous material attached to the back surface of the second mask is removed by the cleaning unit. Therefore, in the subsequent second printing process, it is possible to prevent the viscous material from adhering to the unintended portion of the substrate from the second mask.

  In the above screen printing apparatus, the designated point is a specific position of the substrate on which the first printing process has been performed, and the imaging unit is configured to image the specific position of the substrate after the first printing process. It is desirable.

  According to this screen printing apparatus, the imaging unit images a specific position of the substrate after the first printing process. As a result, it is possible to confirm whether or not the first printing process has been properly executed.

  The screen printing apparatus further includes a print control unit that controls operations of the first printing process and the second printing process, and the specific position of the substrate is attached to the viscous material in the regular first printing process. The print control unit may stop the execution of the second printing process when the determination unit determines that the viscous material is present at the non-normal position at a predetermined non-normal position that cannot be obtained. desirable.

  According to this screen printing apparatus, when the adhesion of the viscous material to the irregular position of the substrate is detected, the second printing process is stopped. Factors that cause the viscous material to adhere to the non-regular position include a mounting error of the first mask and a substrate positioning error when the substrate is moved from the first screen printing unit to the second screen printing unit. When such a mistake occurs, the print control unit stops the execution of the second printing process, so that it is possible to prevent the occurrence of printing defects.

  The screen printing apparatus further includes a print control unit that controls operations of the first printing process and the second printing process, and the specific material is attached to the specific position of the substrate in the normal first printing process. Preferably, the print control unit stops the execution of the second printing process when the determination unit determines that the viscous material does not exist at the normal position.

  According to this screen printing apparatus, the second printing process is stopped when the adhesion of the viscous material to the regular position of the substrate is not detected. Factors that prevent the viscous material from adhering to the normal position include a mounting error of the first mask and a positioning error of the substrate when the substrate is moved. When such a mistake occurs, the print control unit stops the execution of the second printing process, so that it is possible to prevent the occurrence of printing defects.

  In this case, the apparatus further includes a substrate transport unit that transports the substrate from the first screen printing unit to the second screen printing unit, the imaging unit is disposed in the first screen printing unit, and the print control unit includes: In order to stop the execution of the second printing process, it is preferable that the conveyance of the substrate from the first screen printing unit to the second screen printing unit by the substrate conveying unit is stopped.

  According to this screen printing apparatus, when a problem occurs in the first printing process, the substrate is not transported to the second screen printing unit. Therefore, it is possible to take measures against printing defects promptly.

  In the screen printing apparatus, the first mask has a predetermined first thickness and includes a predetermined first pattern opening, and the second mask has a second thickness that is thicker than the first thickness. And having a predetermined second pattern opening and an escape recess provided at a position corresponding to the first pattern opening.

  According to this screen printing apparatus, the present invention can be applied to a sequential printing type screen printing apparatus in which the first printing process for small parts and the second printing process for large parts are performed. That is, the printing pattern by the first printing process is not avoided by the escape recess of the second mask, and it is possible to prevent the occurrence of printing failure due to the viscous material adhering to the second mask.

  In the above screen printing apparatus, the first and second screen printing units each have an independent device configuration, and are arranged between the first screen printing unit and the second screen printing unit, and are accessible by an operator. It can be set as the structure further equipped with the connection conveyor which conveys the said board | substrate in a state.

  According to this screen printing apparatus, the first printing process is completed, and the operator can take out the substrate being transported on the connection conveyor. When returning the substrate to the connection conveyor, a mistake may be made in which the mounting direction of the substrate is mistaken. However, according to the present invention, such a mistake can be detected and a printing failure can be prevented from occurring in the second printing process.

  According to the present invention, in the screen printing apparatus that sequentially prints the viscous material on the substrate in the two screen printing units, it is possible to suppress the occurrence of printing defects due to the adhesion of the viscous material to the mask.

FIG. 1 is a plan view of a screen printing apparatus according to an embodiment of the present invention. FIG. 2 is a schematic side view of the screen printing apparatus in the Y direction. FIG. 3 is a schematic side view of the screen printing apparatus in the X direction. FIG. 4 is a longitudinal sectional view showing an example of a mask. FIG. 4A shows a mask for small parts, and FIG. 4B shows a mask for large parts. FIG. 5 is a schematic diagram illustrating a sequential printing operation. FIG. 6 is a schematic diagram illustrating a sequential printing operation. FIG. 7 is a schematic diagram illustrating a sequential printing operation. FIG. 8 is a schematic diagram showing a sequential printing operation. FIG. 9 is a schematic diagram illustrating a sequential printing operation. FIG. 10 is a schematic diagram illustrating a sequential printing operation. FIG. 11 is a schematic diagram illustrating an example of sequential printing failure. FIG. 12 is a block diagram showing an electrical configuration of the screen printing apparatus. FIG. 13 is a flowchart showing a first embodiment of the operation of the screen printing apparatus. FIG. 14 is a flowchart showing a second embodiment of the operation of the screen printing apparatus. FIG. 15 is a flowchart showing a third embodiment of the operation of the screen printing apparatus. FIG. 16 is a schematic diagram for explaining a fourth embodiment of the operation of the screen printing apparatus. FIG. 17 is a schematic diagram for explaining a fifth embodiment of the operation of the screen printing apparatus. FIG. 18 is an explanatory diagram of printing misalignment in the fifth embodiment.

[Overall structure of screen printing device]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 is a plan view of a screen printing apparatus 100 according to an embodiment of the present invention, FIG. 2 is a schematic side view of the screen printing apparatus 100 in the Y direction, and FIG. 3 is a schematic side view of the X direction. is there. In the present embodiment, a screen printing apparatus 100 that performs mask printing of a solder paste on the upper surface of a printed board (hereinafter referred to as a board 5) is illustrated. That is, in this embodiment, the viscous material is a solder paste.

  As shown in FIG. 1, the screen printing apparatus 100 receives a substrate 5 from a loader LD at a carry-in position En on the upstream side in the transport direction (right side in the X direction), performs a screen printing process on the substrate 5, and performs the transport direction. The substrate 5 is unloaded from the unloading position Ex on the downstream side (left side in the X direction) to the downstream apparatus M. In addition, the conveyance direction of the board | substrate 5 is a X direction, and the direction orthogonal to a X direction in a horizontal surface is a Y direction. Further, the vertical direction perpendicular to the X and Y directions is the Z direction. The downstream device M is a component mounting device that mounts various electronic components on the substrate 5 on which a solder paste is printed, for example.

  The screen printing apparatus 100 includes a base 1, a substrate work table 2 that holds and conveys the substrate 5, and a first screen printing unit 3A and a second screen printing unit 3B that perform screen printing of solder paste on the substrate 5. I have. The first screen printing unit 3A performs a first printing process of screen printing a solder paste on the substrate 5 through the first printing table 30A including the small component mask 6 (first mask) and the small component mask 6. A first squeegee unit 4 </ b> A (first printing unit). The second screen printing unit 3B is soldered to the substrate 5 on which the first printing process has been performed via the second printing table 30B having the large component mask 7 (second mask) and the large component mask 7. A second squeegee unit 4B (second printing unit) for performing a second printing process for screen-printing the paste. Further, the screen printing apparatus 100 incorporates a control unit 90 (see FIG. 12) to be described later for performing operation control of each unit described below.

  The base 1 is disposed in the lower part of the screen printing apparatus 100 and supports each apparatus included in the screen printing apparatus 100. The substrate work table 2 is arranged on the base 1, receives the substrate 5 at the carry-in position En, and supports and fixes the substrate 5 sequentially facing the first and second print tables 30A and 30B during the printing work, It has a function of carrying out the printed substrate 5 from the carry-out position Ex. The second loader LD may be juxtaposed in the Y direction, and the second substrate work table 2 may be arranged on the base 1 in the Y direction.

  The substrate work table 2 includes a movable table 21 movable in the Y direction, a transport conveyor 22, a clamp unit 23, a mask recognition camera 24 (imaging unit), and a cleaning unit 25 (cleaning unit) disposed on the movable table 21. Including. The conveyor 22 includes a pair of conveyor rails that extend in the conveying direction (X direction). The clamp unit 23 is a mechanism for moving the substrate 5 on the conveyor 22 in the X direction while holding the substrate 5 so as to be able to perform a printing operation in a state of being spaced upward from the conveyor 22. The mask recognition camera 24 is attached to the clamp unit 23. The cleaning unit 25 is disposed on the movable table 21.

  The movable table 21 is supported by the guide rail 11 disposed on the base 1 so as to extend in the Y direction so as to be movable in the Y direction. The movable table 21 is moved in the Y direction on the guide rail 11 by a table driving mechanism. Specifically, the movable base 21 is moved in the Y direction by a screw shaft 12 extending in the Y direction and a servo motor 13 that rotationally drives the screw shaft 12. The range of movement of the movable base 21 in the Y direction is set so that it can be moved to a position directly below the first and second printing tables 30A and 30B.

  The conveyor 22 includes a pair of conveyor rails that extend over substantially the entire length of the screen printing apparatus 100 in the X direction. By making the position of the conveyor 22 coincide with the Y-axis coordinates of the carry-in position En and the carry-out position Ex, the board 5 can be carried in and out. One of the pair of conveyor rails of the conveyor 22 can be moved in the Y direction on the movable table 21. For this reason, according to the size of the board | substrate 5 conveyed, the conveyor width (interval between conveyor rails) can be changed.

  The clamp unit 23 is a movable unit arranged so as to hold the pair of conveyor rails of the transport conveyor 22 from both outer sides in the Y direction. The clamp unit 23 is movable in the X direction on the guide rail 51a by an X-axis moving mechanism 51 (see FIG. 2) provided on the movable base 21. That is, the clamp unit 23 is movable in the X direction along the transport conveyor 22. The width of the clamp unit 23 in the Y direction can be changed according to the conveyor width of the transport conveyor 22.

  The clamp unit 23 includes a clamp mechanism 52 for holding and fixing the side of the substrate 5 and a support mechanism 53 for lifting and supporting the substrate 5 on the transport conveyor 22. As shown in FIG. 3, the clamp mechanism 52 includes a fixed clamp portion 52 a disposed along the Y2 direction side of the substrate 5 and a movement disposed along the Y2 direction side of the substrate 5. And a clamp portion 52b. The moving clamp part 52b can be moved in a direction approaching the fixed clamp part 52a by driving an air cylinder (not shown), so that the clamp mechanism 52 sandwiches the substrate 5 on the conveyor 22 from both sides in the Y direction. Can be clamped. The clamp is released by operating the air cylinder in the reverse direction.

  The support mechanism 53 includes a plurality of backup pins 53a and an elevating mechanism 53b that moves the backup pins 53a up and down. The backup pin 53 a is erected on the lower side of the substrate 5 and has a pin tip portion that contacts the lower surface of the substrate 5. The elevating mechanism 53b raises the backup pin 53a to bring the tip of the pin into contact with the lower surface of the substrate 5, and further lifts and supports the substrate 5 on the conveyor 22. When the substrate 5 lifted by the support mechanism 53 is gripped by the clamp mechanism 52, the substrate 5 is fixedly held in a state of being separated upward from the transport conveyor 22. Thereby, it is possible to perform screen printing work on the substrate 5 on the substrate work table 2.

  The mask recognition camera 24 is composed of a CCD area sensor or the like, and is attached to the outside of the clamp unit 23 in the Y1 direction with the imaging direction facing upward. For this reason, the mask recognition camera 24 can move in the Y direction as the substrate work table 2 moves, and can move in the X direction as the clamp unit 23 moves. The mask recognition camera 24 has a mask recognition mark attached to the lower surface side of the screen mask (small component mask 6 and large component mask 7 described later) held in the first and second screen printing units 3A and 3B. Take an image from below. From the image data obtained by this imaging, the position and orientation of the screen mask are recognized.

  The cleaning unit 25 is a cleaner for the screen mask. The cleaning unit 25 includes a cleaning head including a pad that is in contact with the substrate contact surface (lower surface) of the screen mask and a suction nozzle that performs negative pressure suction through the pad. With the cleaning head in contact with the substrate contact surface of the screen mask, the substrate work table 2 and the screen mask are relatively moved (slid) in the Y direction to adhere to the substrate contact surface and the pattern opening. The solder paste is removed. The cleaning head can be moved up and down with respect to the substrate work table 2 and is retracted to a lowered position that is not in contact with the screen mask except during mask cleaning.

  In addition to the above-described original role, in one embodiment of the present invention, the mask recognition camera 24 designates the screen mask (in this embodiment, the large component mask 7) designated in advance as a solder paste expected position. Also plays the role of imaging points. The cleaning unit 25 cleans the screen mask when it is determined that the solder paste is present at the designated point. These points will be described in detail later.

  A pair of frame structures 14 are erected on the base 1. The pair of frame structures 14 extend over the substrate work table 2 in the Y direction and are arranged at predetermined intervals in the X direction. Each frame structure 14 has a gate structure, and a pair of legs 14a extending upward from the vicinity of both ends in the Y direction of the base 1 and beams connecting the upper ends of the legs 14a in the horizontal direction. Part 14b.

  Two substrate recognition cameras 15 (see FIG. 3) are fixedly installed on the lower surface side of the frame structure 14 (beam portion 14b) on the upstream side (right side in FIG. 1) across the substrate work table 2. Has been. The board recognition camera 15 is a camera for imaging the board 5 on the board work table 2. The substrate recognition camera 15 is composed of a CCD area sensor or the like, and is installed with the imaging direction facing downward. The substrate recognition camera 15 images a substrate recognition mark (not shown) attached to the upper surface of the substrate 5. From the image data obtained by this imaging, the position and orientation of the substrate 5 held by the clamp unit 23 are recognized.

  In addition to this function, the board recognition camera 15 also plays a role of imaging a designated point of the board 5 designated in advance as a solder paste adhesion predicted position in another embodiment of the present invention. The designated point is a position where the solder paste adheres in the regular printing process or a position where the solder paste cannot adhere in the regular printing process. These points will be described in detail later.

  The first printing table 30 </ b> A is supported on both sides in the X direction by a pair of guide rails 33 a provided on the pair of frame structures 14, and is disposed at a position above the substrate work table 2. The first printing table 30A is movable in the Y direction along the guide rail 33a extending in the Y direction, and is movable in the vertical direction (Z direction). Similarly, the second printing table 30B is also supported by the guide rail 33a and is movable in the Y direction. Each of the first and second printing tables 30A and 30B includes a substantially rectangular mask fixing member 31 to which the screen mask is detachably assembled, a mask lifting mechanism 32 for moving the mask fixing member 31 up and down (moving in the Z-axis direction), and The mask fixing member 31 is rotated around the Z axis and has a pair of mask drive mechanisms 33 for moving in the Y direction.

  The small component mask 6 is assembled to the mask fixing member 31 of the first printing table 30A. FIG. 4A is a longitudinal sectional view schematically showing an example of the small component mask 6. The small component mask 6 has a predetermined first thickness t1 and includes a predetermined small pattern opening 61 (first pattern opening). The small pattern opening 61 is a minute opening perforated with a pattern corresponding to, for example, an electronic component of 0402 size or a small electronic component such as a BGA having a ball pitch of 0.4 mm. The first thickness t1 is set to a thickness suitable for the small electronic component. A suitable first thickness t1 is, for example, 70 μm. By performing screen printing using the small component mask 6, a solder pattern corresponding to the small pattern opening 61 is printed on the surface of the substrate 5. The height of the solder pattern is the same as the first thickness t1, or slightly lower than the first thickness t1 due to gravity acting on the solder pattern.

  On the other hand, the large component mask 7 is assembled to the mask fixing member 31 of the second printing table 30B. FIG. 4B is a longitudinal sectional view schematically showing an example of the large component mask 7. The large component mask 7 has a second thickness t2 that is thicker than the first thickness t1, and is provided at a position corresponding to a predetermined large pattern opening 71 (second pattern opening) and a small pattern opening 61. An escape recess 72 is provided. The large pattern opening 71 is a relatively large opening perforated with a pattern corresponding to a large electronic component such as a shield case. The second thickness t2 is set to a thickness suitable for the large electronic component. A suitable second thickness t2 is, for example, 130 μm. By performing screen printing using the large component mask 7, a solder pattern corresponding to the large pattern opening 71 is printed on the surface of the substrate 5. The height of this solder pattern is the same as the second thickness t2 or slightly smaller than the second thickness t2.

  The relief recess 72 is recessed on the substrate contact surface (lower surface) side of the large component mask 7. The position corresponding to the above-mentioned small pattern opening 61 refers to the substrate 5 on which the solder pattern for small components is formed by screen printing using the small component mask 6 and the same substrate 5 using the large component mask 7. This means a position where the small component solder pattern faces the large component mask 7 when screen printing is additionally performed (sequential printing). The depth t3 of the relief recess 72 is set to be larger than the first thickness t1 of the small component mask 6. The XY size of the relief recess 72 is set to a size that can surround the solder pattern forming portion for the small component.

  For this reason, when the plate of the large component mask 7 is sequentially printed on the substrate 5 after the first printing process using the small component mask 6, the small component formed by the small component mask 6 is obtained. Therefore, the large solder mask 7 and the solder pattern are kept in a non-contact state. By performing the second printing process using the large component mask 7 in this state, the solder pattern for the large component is printed on the substrate 5 in addition to the solder pattern for the small component.

  The mask elevating mechanism 32 is a mechanism for elevating the mask fixing member 31. The mask elevating mechanism 32 supports the mask fixing member 31 and moves the mask fixing member 31 up and down by a guide, a screw shaft, and a Z-axis motor that drives the screw shaft (not shown). The mask elevating mechanism 32 is supported at both ends in the X direction on a pair of guide rails 33a.

  The pair of mask drive mechanisms 33 includes a pair of guide rails 33a and screw shafts 33b extending in the Y direction, and two Y-axis motors 33c that respectively drive the pair of screw shafts 33b. Respectively. The pair of mask drive mechanisms 33 can drive the mask lifting mechanism 32 in the Y direction independently from both sides in the X direction. If both of the pair of mask drive mechanisms 33 are driven at a constant speed, the mask fixing member 31 can be moved in the Y direction in parallel with the mask elevating mechanism 32. On the other hand, if there is a difference in driving amount between the pair of mask drive mechanisms 33, the mask fixing member 31 together with the mask elevating mechanism 32 can be rotated in the horizontal plane (in the XY plane).

  With the above mechanism, the first and second printing tables 30A and 30B can be moved to arbitrary positions in the Y direction within the movement range to perform printing on the substrate 5, and hold the small component mask 6 Alternatively, it is possible to perform detailed alignment (Y-direction position and inclination in the horizontal plane) in the XY plane of the large component mask 7. The alignment of the position in the X direction is performed by adjusting the movement of the clamp unit 23. At the time of printing, the first and second printing tables 30A and 30B are moved down in the Z2 direction by the mask elevating mechanism 32 to perform a plate aligning operation to bring the masks 6 and 7 into contact with the upper surface of the substrate 5, and after printing, Z1 A plate separating operation is performed in which the masks 6 and 7 are separated from the upper surface of the substrate 5 by moving upward.

  The first squeegee unit 4A is supported by the central portion of the movable beam 42 extending in the X direction, and is disposed above the first printing table 30A. The second squeegee unit 4B is supported at the center of the other movable beam 42 and is disposed above the second printing table 30B. The first and second squeegee units 4A and 4B each have a squeegee 41 (see FIG. 2) that reciprocates in the Y direction while pressing the solder paste against the upper surfaces of the masks 6 and 7, and a squeegee 41 during printing. And an unillustrated elevating mechanism for elevating the mask, and a mask 6 and an unillustrated squeegee angle variable mechanism for changing the inclination direction and angle of the squeegee 41 with respect to the mask 7.

  The movable beam 42 is movably supported on a pair of guide rails 43 provided on the upper surfaces of the pair of frame structures 14 so as to extend along the Y direction. The movable beam 42 is moved in the Y direction by a screw shaft 44 and a squeegee shaft motor 45 provided in the frame structure 14 and extending in the Y direction. Each squeegee 41 performs a printing operation by sliding the upper surfaces of the masks 6 and 7 in the Y direction as the first and second squeegee units 4A and 4B move in the Y direction as the movable beam 42 moves. . The first squeegee unit 4A performs the first printing process on the substrate 5 using the first printing table 30A provided with the small component mask 6. After the first printing process, the second squeegee unit 4B performs the second printing process on the same substrate 5 using the second printing table 30B including the large component mask 7. Hereinafter, the procedure of such sequential printing will be illustrated.

[Procedure for sequential printing]
5 to 10 are schematic diagrams showing sequential printing operations by the first and second screen printing units 3A and 3B in time series. In the sequential printing, first, the first screen printing unit 3 </ b> A executes a first printing process in which a small component solder pattern 6 is screen printed on the substrate 5 using the small component mask 6. As shown in FIG. 5, the substrate work table 2 moves the substrate 5 directly below the small component mask 6 held by the mask fixing member 31 of the first printing table 30A. A squeegee 41 holding a solder pool Sd, which is a lump of solder paste, is in contact with the upper surface of the small component mask 6.

  Subsequently, as shown in FIG. 6, the mask raising member 32 lowers the small component mask 6 together with the mask fixing member 31, and performs a plate aligning operation in which the small component mask 6 is brought into contact with the upper surface of the substrate 5. At this time, the squeegee 41 is also lowered. The squeegee 41 slides in the right direction (Y direction) on the small component mask 6 while pressing the solder pool Sd against the upper surface of the substrate 5. As a result, a small pattern Sd1 corresponding to the small pattern opening 61 of the small component mask 6 is printed on the upper surface of the substrate 5 (first printing process).

  Thereafter, as shown in FIG. 7, a plate separating operation for separating the small component mask 6 upward from the upper surface of the substrate 5 is performed in the first screen printing unit 3 </ b> A. The squeegee 41 is also raised at the same time. The substrate 5 for the first printing process is moved to the second screen printing unit 3B. That is, the substrate work table 2 moves the substrate 5 on which the small pattern Sd1 is printed directly below the large component mask 7 held by the mask fixing member 31 of the second print table 30B. A squeegee 41 holding a solder pool Sd is in contact with the upper surface of the large component mask 7.

  Subsequently, a plate aligning operation of the large component mask 7 is performed. FIG. 8 shows a state in which the large component mask 7 is lowered together with the mask fixing member 31 by the mask lifting mechanism 32 of the second printing table 30 </ b> B, and the large component mask 7 is brought into contact with the upper surface of the substrate 5. . During the plate matching, the small pattern Sd1 previously printed on the substrate 5 is accommodated in the escape recess 72. As described above with reference to FIG. 4, the relationship between the first thickness t1 of the small component mask 6 and the recess depth t3 of the escape recess 72 is t1 <t3, so that the small pattern Sd1 is in contact with the large component mask 7. Never do.

  After that, the squeegee 41 slides leftward (Y direction) on the large component mask 7 while pressing the solder pool Sd against the upper surface of the substrate 5. Thereby, a large pattern Sd2 corresponding to the large pattern opening 71 of the large component mask 7 is additionally printed on the upper surface of the substrate 5 (second printing process). Thereafter, as shown in FIG. 10, a plate separating operation for separating the large component mask 7 upward from the upper surface of the substrate 5 is performed in the second screen printing unit 3B.

  As described above, according to the screen printing apparatus 100 capable of performing sequential printing, a pattern opening for solder paste printing required for one substrate 5 is provided with a small pattern of the small component mask 6 having different thicknesses. The printing process is performed separately for the opening 61 and the large pattern opening 71 of the large component mask 7. As a result, a small pattern Sd1 and a large pattern Sd2 that are solder patterns having an aspect ratio (solder height / solder bottom area, ie, mask thickness / opening area) corresponding to the component size are formed on the surface of the substrate 5, respectively. be able to. Alternatively, different viscous materials can be printed (for example, printing with a solder paste and an adhesive) by changing the viscous materials used in the first and second screen printing units 3A and 3B.

[Causes of printing defects in sequential printing]
Sequential printing has the above-mentioned advantages, but printing defects occur due to performing two printing processes, the first printing process and the second printing process, on one substrate 5. Sometimes. One of them is a screen mask mounting direction error. FIG. 11 is a schematic diagram illustrating an example of sequential printing failure due to a mask mounting error. Here, the case where the small component mask 6 is attached to the mask fixing member 31 of the first screen printing unit 3A in the state where the mounting direction is inverted by 180 ° with respect to the normal direction is illustrated. In general, the screen mask has a rectangular shape in plan view, and the operator does not mistake the mounting direction by 90 °, but the screen mask may be mounted reversed by 180 °.

  When the first printing process is performed in this state, the small pattern Sd1 is not printed at a predetermined normal position on the substrate 5, but at a non-normal position corresponding to the inverted small pattern opening 61. . When the substrate 5 with such a small pattern Sd1 is transferred to the second screen printing unit 3B and plate-matching with the large component mask 7 is performed for the second printing process, the solder paste of the small pattern Sd1 becomes large. It adheres to the lower surface of the component mask 7. That is, since the position of the relief recess 72 of the large component mask 7 and the small pattern Sd1 on the substrate 5 is not aligned, the small pattern Sd1 and the lower surface of the large component mask 7 come into contact with each other.

  When such a mask mounting error occurs, it is a matter of course that the substrate 5 on which the small pattern Sd1 has been printed at the non-regular position becomes defective in printing. In addition to this, the solder paste adhered to the large component mask 7 is transferred to the substrate 5 to be printed after the substrate 5, thereby inducing a further printing failure substrate 5. It will end up.

  A similar problem can occur due to an error in the loading direction of the substrate 5. The first screen printing unit 3A and the second screen printing unit 3B each have an independent device configuration, and an operator can temporarily take out the substrate 5 between the printing units for the purpose of inspection or visual confirmation. There is a case. In this case, when the operator re-inserts the taken-out substrate 5 into the printing line, the input direction may be wrong. A possible error is that the substrate 5 is re-inserted in a state where the substrate is inverted by 180 ° with respect to the normal input direction. Even in such a case, it becomes the same as the embodiment shown in FIG. 11, and the solder paste of the small pattern Sd1 adheres to the lower surface of the large component mask 7. In the present embodiment, a screen printing apparatus 100 that suppresses such printing defects is provided.

[Electrical configuration of screen printing device]
FIG. 12 is a block diagram showing an electrical configuration of the screen printing apparatus 100. In addition to the substrate recognition camera 15 and the mask recognition camera 24 described above, the screen printing apparatus 100 includes a sensor 81, a substrate transport motor 82, a work table drive unit 83, a cleaning drive unit 84, a clamp drive unit 85, a mask drive unit 86, A squeegee driving unit 87 and a control unit 90 (printing control unit) are provided.

  In the present embodiment, the substrate recognition camera 15 and the mask recognition camera 24 functioning as an imaging unit, in addition to the original substrate recognition and mask recognition imaging, are executed in the first and second screen printing units 3A and 3B. Then, a designated point designated in advance is imaged as the expected position of the solder paste adhesion resulting from the second printing process.

  As a specific example, the board recognition camera 15 disposed in the first screen printing unit 3A has a normal position where the solder paste adheres to the board 5 after the first printing process in the normal printing process, or In this printing process, an image of a non-regular position where the solder paste cannot adhere is imaged. The substrate recognition camera 15 arranged in the second screen printing unit 3B is configured to detect the normal position of the substrate 5 introduced into the second screen printing unit 3B after the first printing process or the substrate 5 after the second printing process, or The non-regular position is imaged. The mask recognition camera 24 images a specific position on the back surface of the small component mask 6 after the first printing process or a specific position on the back surface of the large component mask 7 after the second printing process. The specific position is a designated point where the solder paste is expected to adhere when an attachment error of the masks 6 and 7 or an insertion error of the substrate 5 occurs.

  The sensor 81 acquires information necessary for controlling the screen printing apparatus 100, such as a sensor for measuring environmental conditions such as a temperature sensor and a humidity sensor, a position sensor, and a pressure sensor. The substrate transport motor 82 is a drive source for driving the belt conveyor provided in the transport conveyor 22. By driving the substrate transport motor 82, the transport conveyor 22 transports the substrate 5 in the X direction.

  The work table drive unit 83 is a drive source for the substrate work table 2 and includes an X-axis servo motor 831, a Y-axis servo motor 832, and a Z-axis servo motor 833. The X-axis servomotor 831 corresponds to the above-described X-axis moving mechanism 51 that moves the clamp unit 23 in the X direction. The Y-axis servo motor 832 corresponds to the servo motor 13 that moves the movable base 21 in the Y direction. The Z-axis servomotor 833 is a drive source for the elevating mechanism 53b of the support mechanism 53 that elevates the substrate.

  The cleaning drive unit 84 is a drive source of the cleaning unit 25, and includes a mechanism that generates a suction force to the suction nozzle of the cleaning head, a mechanism that raises and lowers the cleaning head, and the like. Note that the movement of the cleaning unit 25 in the Y direction depends on the Y-axis servomotor 832.

  The clamp drive unit 85 is a drive source that moves the moving clamp unit 52b of the clamp unit 23 between a position where the side of the substrate 5 is pressed and the substrate 5 is clamped and a position where the clamp is released. . The clamp drive unit 85 is an air cylinder, for example.

  The mask driving unit 86 moves the small component mask 6 in the first printing table 30A and the large component mask 7 in the second printing table 30B in the Y direction and the Z direction, respectively, and rotates around the Z axis. It is a drive part for. The mask drive unit 86 corresponds to the mask lifting mechanism 32 and the mask drive mechanism 33 described above.

  The squeegee drive unit 87 is a drive source that moves the movable beams 42 of the first and second squeegee units 4A and 4B in the Y direction, and includes the squeegee shaft motor 45 described above. The squeegee driving unit 87 further includes an elevating mechanism that raises and lowers the squeegee 41 and a squeegee angle variable mechanism that adjusts the tilt angle of the squeegee 41.

  The control unit 90 includes a microcomputer or the like, and comprehensively controls the operation of the screen printing apparatus 100, that is, the first and second print processing operations described above. The control unit 90 is functionally executed by a predetermined program, so that the imaging control unit 91, the image processing unit 92, the arithmetic processing unit 93 (determination unit), the conveyance control unit 94, the work table control unit 95, and the cleaning control are functionally performed. It operates so as to have a section 96, a clamp control section 97, a mask control section 98, and a squeegee control section 99.

  The imaging control unit 91 controls the imaging operations of the substrate recognition camera 15 and the mask recognition camera 24. Specifically, the imaging control unit 91 is configured to cause the board recognition camera 15 to take an image of the board recognition mark for the board 5 recognition process. The mask recognition camera 24 is attached to the small part mask 6 and the large part mask 7. An operation for imaging the mask recognition mark is executed. In this embodiment, in addition to this, the imaging control unit 91 performs an operation of causing the board recognition camera 15 to take an image of a designated point of the substrate 5 designated in advance as a solder paste adhesion predicted position, or a designated point of the mask 6 or 7. The operation of causing the mask recognition camera 24 to pick up an image

  The image processing unit 92 performs image processing such as edge detection processing for substrate recognition mark and mask recognition mark shape recognition on the image data acquired by the substrate recognition camera 15 and the mask recognition camera 24. Further, the image processing unit 92 performs image processing for extracting a portion where the solder paste is attached to the image data obtained by imaging the designated point by the board recognition camera 15 and the mask recognition camera 24.

  The arithmetic processing unit 93 performs various arithmetic processes required for controlling the screen printing apparatus 100, situation recognition based on various information acquired by the sensor 81, arithmetic processes for changing control conditions, and the like. In addition to this, the arithmetic processing unit 93 determines whether or not solder paste (viscous material) exists at the designated point based on the image processing result of the image data of the designated point by the image processing unit 92. I do.

  The transport controller 94 controls the substrate transport motor 82 in order to control the substrate transport operation of the substrate 5 by the belt conveyor of the transport conveyor 22. The work table control unit 95 controls the movement operation of the substrate work table 2, the movement of the clamp unit 23, and the lifting / lowering operation by controlling the work table driving unit 83, and positioning the substrate 5 on the masks 6 and 7. Execute an action.

  The cleaning control unit 96 controls the cleaning driving unit 84 to execute a cleaning operation of wiping the back surfaces of the masks 6 and 7 by the cleaning unit 25. In the present embodiment, in addition to the predetermined periodic cleaning operation, when the arithmetic processing unit 93 determines that the solder paste is present at the designated point, the cleaning control unit 96 cleans the back surface of the large component mask 7. Run the action.

  The clamp control unit 97 controls the movement operation of the moving clamp unit 52 b of the clamp unit 23 by controlling the clamp driving unit 85. When the clamp driving unit 85 is an air cylinder, the clamp control unit 97 controls a regulator attached to the air cylinder and controls the thrust of the air cylinder according to a predetermined substrate pressing parameter.

  The mask control unit 98 controls the mask drive unit 86 to execute horizontal movement and vertical movement for alignment of the small component mask 6 and the large component mask 7 with respect to the substrate. The squeegee control unit 99 controls the squeegee driving unit 87 to execute the first and second print processing operations by the squeegee 41 of the first and second squeegee units 4A and 4B.

[First Embodiment of Solder Detection Processing]
FIG. 13 is a flowchart showing a first embodiment of solder detection processing by imaging the designated point by the screen printing apparatus 100. In the first embodiment, a printing failure is assumed due to the small component mask 6 being attached to the mask fixing member 31 of the first screen printing unit 3 </ b> A in a state of being inverted 180 ° with respect to the normal direction. The designated point for checking whether or not the solder paste is present is a specific position on the back surface of the large component mask 7 (second mask), and imaging is performed after the second printing process.

  Assuming the printing failure, the control unit 90 sets a designated point at a specific position on the back surface of the large component mask 7 and teaches this setting to the imaging control unit 91 (step S1). When the first printing process is performed in the first screen printing unit 3A using the small component mask 6 whose mounting direction is inverted by 180 °, the small pattern Sd1 is not inverted by 180 ° with respect to the normal position of the substrate 5. It will be printed at the normal position. Then, when plate alignment of the large component mask 7 is performed on the substrate 5 for the second printing process, it can be expected that the solder paste adheres to a portion facing the non-regular position (predicted adhesion position). ). Such a predicted adhesion position is the specific position, and a designated point is set at the position.

  Subsequently, a printing process for the substrate 5 is performed. The conveyance control unit 94 operates the conveyance conveyor 22 to take in the substrate 5 from the loader LD, and the work table control unit 95 operates the substrate work table 2, whereby the substrate 5 is carried into the first screen printing unit 3 </ b> A. (Step S2).

  Next, the clamp control unit 97, the mask control unit 98, and the squeegee control unit 99 control the clamp drive unit 85, the mask drive unit 86, and the squeegee drive unit 87, respectively. A first printing process is performed (see also step S3 and FIG. 6). As a result, a small pattern Sd 1 corresponding to the small pattern opening 61 of the small component mask 6 is printed on the substrate 5. Here, if the small component mask 6 is properly attached, the small pattern Sd1 is printed at the normal position of the substrate 5 (see FIG. 7). On the other hand, if the small component mask 6 is mounted 180 ° inverted, the small pattern Sd1 is printed at an irregular position on the substrate 5 (see FIG. 11).

  Subsequently, the work table control unit 95 operates the substrate work table 2 to move the substrate 5 to the second screen printing unit 3B (step S4). Then, the clamp control unit 97, the mask control unit 98, and the squeegee control unit 99 control the clamp drive unit 85, the mask drive unit 86, and the squeegee drive unit 87, respectively, so that the second screen printing unit 3B is connected to the substrate 5 by the second. Two printing processes are performed (see also step S5 and FIG. 9). Thereby, in addition to the small pattern Sd1, a large pattern Sd2 corresponding to the large pattern opening 71 of the large component mask 7 is printed on the substrate 5 (see FIG. 10).

  If the first printing process is performed with the properly mounted small component mask 6, the small pattern Sd1 in the second printing process is the relief recess 72 of the large component mask 7 as shown in FIG. Is housed in. On the other hand, if the first printing process is executed with the small component mask 6 attached with being inverted 180 °, the small pattern Sd1 is not accommodated in the escape recess 72. In addition, the solder paste of the small pattern Sd1 adheres to the designated point set in step S1 of the large component mask 7.

  After the second printing process, the imaging control unit 91 causes the mask recognition camera 24 to image the designated point on the back surface of the large component mask 7 (step S6). The image data acquired by the imaging is sent to the image processing unit 92, and image processing for extracting the attached portion of the solder paste in the image is executed. Then, based on the image processing result, the arithmetic processing unit 93 determines whether or not a solder paste exists at the designated point (step S7).

  If it is determined that there is no solder paste at the designated point (NO in step S7), the regular first printing process has been performed on the substrate 5. In this case, the control unit 90 checks whether or not there is a subsequent substrate 5 to be printed (step S8). If there is a subsequent substrate 5 (YES in step S8), the control unit 90 proceeds to step S2. Return and repeat the process.

  On the other hand, if it is determined that the solder paste is present at the designated point (YES in step S7), an attachment error of the small component mask 6 has occurred, and the regular first printing process has not been performed on the substrate 5. become. In this case, the control unit 90 causes the cleaning control unit 96 to perform a cleaning operation. The cleaning control unit 96 controls the cleaning driving unit 84 to execute an operation of cleaning the back surface of the large component mask 7 (step S9). By this cleaning operation, the solder paste attached to the back surface of the large component mask 7 is removed.

  Further, the control unit 90 causes a display panel or audio source (not shown) to notify the occurrence of a printing failure and stops the screen printing apparatus 100 in error (step S10). This is to notify the operator that a printing failure has occurred on the substrate 5 on which the first and second printing processes have been performed immediately before, and to cause the operator to take out the substrate from the screen printing apparatus 100. . After the error process, the screen printing apparatus 100 is restarted, and the process returns to step S2 to continue the process.

[Second Embodiment of Solder Detection Processing]
FIG. 14 is a flowchart showing a second embodiment of solder detection processing by imaging the designated point by the screen printing apparatus 100. In the second embodiment, an example will be shown in which it is found by imaging a specific position of the substrate 5 that an attachment error of the small component mask 6 similar to that in the first embodiment described above has occurred. Unlike the first embodiment, the imaging timing is after the execution of the first printing process and before the execution of the second printing process.

  Assuming the printing failure, the control unit 90 sets a designated point at a specific position on the surface of the substrate 5 and teaches this setting to the imaging control unit 91 (step S11). As described above, when the first printing process is performed using the small component mask 6 whose mounting direction is reversed by 180 °, the small pattern Sd1 is printed on the non-regular position of the substrate 5 that is reversed by 180 ° with respect to the regular position. Is done. This non-regular position is a position where the solder paste cannot adhere in the regular first printing process. The control unit 90 sets the non-regular position (specific position) as a predicted attachment position as a designated point.

  Subsequently, a printing process for the substrate 5 is performed. The substrate 5 is carried into the first screen printing unit 3A (step S12), and the first printing process is performed on the substrate 5 (step S13). Thereby, the small pattern Sd1 is printed on the substrate 5. If the small component mask 6 is properly attached, the small pattern Sd1 is printed at the normal position of the substrate 5, and if it is attached 180 ° reversed, the small pattern Sd1 is printed at the non-normal position of the substrate 5. Is done. After the first printing process, the substrate 5 is moved to the second screen printing unit 3B (step S14).

  Thereafter, the imaging control unit 91 causes the board recognition camera 15 provided in the second screen printing unit 3B to take an image of the designated point of the board 5 moved to the second screen printing unit 3B (step S15). Based on the image of the designated point acquired by this imaging, the arithmetic processing unit 93 determines whether or not a solder paste exists at the designated point (step S16).

  If it is determined that there is no solder paste at the designated point (NO in step S16), the regular first printing process has been performed on the substrate 5. In this case, the control unit 90 causes the second screen printing unit 3B to execute the second printing process on the substrate 5 (step S17). Thereafter, the control unit 90 confirms whether or not there is a subsequent substrate 5 to be printed (step S18). If there is a subsequent substrate 5 (YES in step S18), the control unit 90 proceeds to step S12. Return and repeat the process.

  On the other hand, if it is determined that the solder paste is present at the designated point (YES in step S18), an attachment error of the small component mask 6 has occurred, and the regular first printing process has not been performed on the substrate 5. become. In this case, the control unit 90 stops the execution of the second printing process. That is, the control unit 90 notifies the occurrence of defective printing and stops the screen printing apparatus 100 in error (step S19).

  According to the second embodiment, it is possible to detect a printing failure before the second printing process for the substrate 5 is performed. Therefore, there is an advantage that it is possible to avoid performing unnecessary second printing processing on the substrate 5 that is already defective and to prevent the solder paste from adhering to the large component mask 7.

[Third embodiment of solder detection processing]
FIG. 15 is a flowchart showing a third embodiment of solder detection processing by imaging the designated point by the screen printing apparatus 100. The third embodiment is an aspect in which a specific position of the substrate 5 is imaged as in the second embodiment, but when the first printing process is executed in a state where the small component mask 6 is properly attached, An example will be shown in which a normal position where solder paste is normally printed is imaged as the specific position (position to be attached). Contrary to the second embodiment, in the third embodiment, the regular position is set as a designated point, and the occurrence of a printing defect is detected when there is no solder paste at the designated point.

  The control unit 90 sets a designated point at a regular position where the small pattern Sd1 is printed when the regular first printing process is performed, and teaches this setting to the imaging control unit 91 (step S21). The substrate 5 is carried into the first screen printing unit 3A (step S22), and the first printing process is performed on the substrate 5 (step S23).

  Thereafter, the imaging control unit 91 causes the board recognition camera 15 provided in the first screen printing unit 3A to take an image of the designated point of the board 5 after the first printing process (step S24). Based on the image of the designated point acquired by this imaging, the arithmetic processing unit 93 determines whether or not a solder paste exists at the designated point (step S25).

  If it is determined that the solder paste is present at the designated point (YES in step S25), the regular first printing process has been performed on the substrate 5. In this case, the control unit 90 moves the substrate 5 to the second screen printing unit 3B (step S26), and further causes the second screen printing unit 3B to execute the second printing process on the substrate 5 (step S27). Thereafter, the control unit 90 confirms whether or not there is a subsequent substrate 5 to be printed (step S28). If there is a subsequent substrate 5 (YES in step S28), the control unit 90 proceeds to step S22. Return and repeat the process.

  On the other hand, when it is determined that the solder paste does not exist at the designated point (NO in step S25), an attachment error of the small component mask 6 occurs, and the regular first printing process is not performed on the substrate 5. It will be. In this case, the control unit 90 stops the execution of the second printing process by stopping the conveyance of the substrate 5 to the second screen printing unit 3B. That is, the control unit 90 notifies the occurrence of defective printing and stops the screen printing apparatus 100 in error (step S29). Thereby, conveyance of the board | substrate 5 to the 2nd screen printing part 3B by the board | substrate work table 2 is stopped. The third embodiment also has an advantage that unnecessary execution of the second printing process can be avoided as in the second embodiment.

[Fourth Embodiment of Solder Detection Processing]
FIG. 16 is a schematic diagram for explaining a fourth embodiment of solder detection processing by imaging a designated point by a screen printing apparatus. The screen printing apparatus shown in FIG. 16 shows an example in which the first screen printing unit 3C and the second screen printing unit 3D each have an independent device configuration, and a connecting conveyor 22A (substrate conveyance unit) is disposed between them. ing.

  The first screen printing unit 3C includes a small component mask 6, a substrate recognition camera 15C, and a mask recognition camera 24C, and the second screen printing unit 3D includes a large component mask 7, a substrate recognition camera 15D, and a mask recognition camera 24D. It has. The connecting conveyor 22A conveys the substrate 5 that has been subjected to the first printing process by the first screen printing unit 3C to the second screen printing unit 3D. Since the connection conveyor 22A conveys the substrate 5 with the substrate 5 exposed to the outside, the operator can access the substrate 5 on the connection conveyor 22A.

  According to the above screen printing apparatus, the first printing process is completed, and the operator can take out the substrate 5 being conveyed on the connecting conveyor 22A. For example, the operator may take out the substrate 5 by stopping the connecting conveyor 22A in order to check the finish of the first printing process. When returning the substrate 5 to the connecting conveyor 22A, a mistake may be made in which the mounting direction of the substrate 5 is mistaken by 180 °. In this case, even if the correct first printing process is performed on the substrate 5, a printing defect occurs in the second printing process in the second screen printing unit 3D. In FIG. 16, the mark “A” on the substrate 5 is inverted between the first screen printing unit 3 </ b> C and the connecting conveyor 22 </ b> A schematically represents a case where the above-described mistake has occurred.

  As a method for detecting a printing defect in this case, the above-described first to third embodiments can be applied. That is, the detection method according to the first embodiment is a method of imaging the large component mask 7 of the second screen printing unit 3D after the second printing process in the second screen printing unit 3D. Specifically, after the second printing process is performed on the board carried into the second screen printing unit 3D from the connecting conveyor 22A, the mask recognition camera 24D causes the large component mask 7 to be imaged. When an error of returning the substrate 5 on the connecting conveyor 22A occurs, the solder paste adheres to the designated point of the large component mask 7. Therefore, it is possible to detect printing defects.

  According to the second and third embodiments, the printing failure detection method is performed by the substrate recognition camera 15D using the substrate recognition camera 15D before the second printing process is performed on the substrate carried from the connecting conveyor 22A to the second screen printing unit 3D. Is a method of imaging. The point to be imaged is a designated point consisting of the above-mentioned non-regular position (second embodiment) or regular position (third embodiment) designated in advance on the surface of the substrate 5. By imaging these designated points, it is possible to detect printing defects caused by the return error.

[Fifth Embodiment of Solder Detection Processing]
FIG. 17 is a schematic diagram for explaining a fifth embodiment of solder detection processing by imaging a designated point by a screen printing apparatus. 17, the screen printing apparatus shown in FIG. 17 has a device configuration in which the first screen printing unit 3C and the second screen printing unit 3D are independent from each other, and a connecting conveyor 22A is arranged therebetween.

  In the first screen printing unit 3C, even when there is no mistake in which the mounting direction of the small component mask 6 is wrong, a printing defect may occur. For example, this is a case where plate matching between the small component mask 6 and the substrate 5 has occurred for some reason. As shown in FIG. 18A, it is assumed that the first printing process is performed in a state where the small component mask 6 is displaced with respect to the substrate 5 and the plates are aligned. In this case, a printing deviation occurs in which the small pattern Sd1 is printed at a position shifted from the original printing position of the substrate 5 by the positional deviation of the mask. In this case, as shown in FIG. 18B, in the second printing process, there is a case in which the small pattern Sd1 is not accommodated in the escape recess 72 of the large component mask 7, and printing failure may occur.

  The first to third embodiments described above can also be applied as a printing defect detection method in this case. That is, the detection method according to the first embodiment is a method of imaging the large component mask 7 of the second screen printing unit 3D after the second printing process in the second screen printing unit 3D. Specifically, after the second printing process is performed on the board carried into the second screen printing unit 3D from the connecting conveyor 22A, the mask recognition camera 24D causes the large component mask 7 to be imaged. When a large printing deviation of the small pattern Sd1 occurs in the first printing process, the solder paste adheres around the large pattern opening 71 of the large component mask 7. Therefore, it is possible to detect printing defects by performing imaging with the periphery of the large pattern opening 71 as the designated point.

  According to the second and third embodiments, the printing failure detection method is performed by the substrate recognition camera 15D using the substrate recognition camera 15D before the second printing process is performed on the substrate carried from the connecting conveyor 22A to the second screen printing unit 3D. Is a method of imaging. The imaged point is the printing position of the small pattern Sd1 on the surface of the substrate 5. By causing the board recognition camera 15D to take an image with this printing position as a designated point, it is possible to detect a printing defect caused by the printing misalignment.

  Alternatively, the printing position of the small pattern Sd1 on the substrate 5 may be imaged by the substrate recognition camera 15C of the first screen printing unit 3C. That is, the substrate 5 after the first printing process is imaged inside the first screen printing unit 3C. Then, when the printing deviation of the small pattern Sd1 is detected by the imaging, the substrate from the first screen printing unit 3C to the second screen printing unit 3D by the connecting conveyor 22A is stopped in order to stop the execution of the second printing process. 5 is stopped. Also according to this aspect, it is possible to detect printing defects in the same manner.

100 Screen Printer 15 Board Recognition Camera (Imaging Unit)
2 Substrate work table 21 Movable base 21
22 Conveyor 22A Connection conveyor (substrate transport unit)
24 Mask recognition camera (imaging part)
25 Cleaning unit (cleaning part)
3A, 3C First screen printing unit 3B, 3D Second screen printing unit 30A First printing table 30B Second printing table 4A First squeegee unit (first printing unit)
4B 2nd squeegee unit (2nd printing part)
5 Substrate 5
6 Mask for small parts (first mask)
61 Small pattern opening (first pattern opening)
7 Mask for large parts (second mask)
71 Large pattern opening (second pattern opening)
72 Relief recess 90 Control unit (printing control unit)
93 Arithmetic processing part (determination part)

Claims (9)

A first screen printing unit including a first mask and a first printing unit, and performing a first printing process for screen printing a viscous material on the substrate;
A second screen printing unit comprising a second mask and a second printing unit, and performing a second printing process for screen printing a viscous material on the substrate on which the first printing process has been performed;
An imaging unit that images a designated point designated in advance as the predicted adhesion position of the viscous material resulting from the first printing process or the second printing process;
A determination unit that determines whether or not the viscous material is present at the designated point based on an image acquired by the imaging unit;
A screen printing apparatus comprising: The screen printing apparatus according to claim 1,
The designated point is a specific position on the back surface of the second mask;
The screen printing apparatus, wherein the imaging unit images the specific position of the second mask after the second printing process. The screen printing apparatus according to claim 2,
A cleaning unit for cleaning the back surface of the second mask;
The said cleaning part is a screen printing apparatus which cleans the back surface of the said 2nd mask, when the said determination part determines with the said viscous material existing in the back surface of the said 2nd mask. The screen printing apparatus according to claim 1,
The designated point is a specific position of the substrate on which the first printing process has been performed;
The screen printing apparatus, wherein the imaging unit images a specific position of the substrate after the first printing process. The screen printing apparatus according to claim 4.
A printing control unit for controlling operations of the first printing process and the second printing process;
The specific position of the substrate is a predetermined non-normal position where the viscous material cannot adhere in the normal first printing process,
The screen printing apparatus, wherein when the determination unit determines that the viscous material is present at the non-regular position, the print control unit stops the execution of the second printing process. The screen printing apparatus according to claim 4.
A printing control unit for controlling operations of the first printing process and the second printing process;
The specific position of the substrate is a predetermined normal position where the viscous material adheres in the normal first printing process,
The screen printing apparatus, wherein when the determination unit determines that the viscous material does not exist at the regular position, the print control unit stops the execution of the second printing process. The screen printing apparatus according to claim 5 or 6,
A substrate transport unit that transports the substrate from the first screen printing unit to the second screen printing unit;
The imaging unit is disposed in the first screen printing unit,
The screen printing apparatus, wherein the print control unit stops conveyance of the substrate from the first screen printing unit to the second screen printing unit by the substrate conveyance unit in order to stop execution of the second printing process. . In the screen printing apparatus of any one of Claims 1-7,
The first mask has a predetermined first thickness and includes a predetermined first pattern opening;
The second mask has a second thickness larger than the first thickness, and includes a predetermined second pattern opening and an escape recess provided at a position corresponding to the first pattern opening. . The screen printing apparatus according to any one of claims 1 to 8,
The first and second screen printing units each have an independent device configuration,
A screen printing apparatus, further comprising a connecting conveyor that is disposed between the first screen printing unit and the second screen printing unit and conveys the substrate in an accessible state by an operator.

Images