Printing system, printing device and printing method

Abstract

To provide a printing system, a printing device and a printing method that can clean a mask at an appropriate timing.SOLUTION: A printing method for printing solder on a substrate using a mask with a plurality of openings, comprises: printing solder on a first substrate using the mask (ST2); acquiring information on a solder volume ratio at a plurality of printing portions corresponding to the plurality of openings on the first substrate on which the solder has been printed (ST4); determining whether or not cleaning of the mask is necessary, on the basis of a distribution of the solder volume ratio of the first substrate derived from the acquired information (ST5); and performing cleaning of the mask before printing solder on a second substrate (ST6) when it is determined that cleaning of the mask is necessary (Yes in ST5).SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to a printing system, a printing apparatus, and a printing method for printing solder on a substrate. [Background technology]

[0002] The printing device brings a substrate into contact with the underside of a mask having multiple openings, slides a squeegee in contact with the mask to which paste solder has been supplied, and forces the solder into the multiple openings, then separates the substrate from the mask to transfer (print) the solder onto the substrate. After printing solder onto multiple substrates in succession, the printing device performs cleaning to remove any solder remaining in the openings and on the backside of the mask (see, for example, Patent Document 1). Patent Document 1 discloses that the substrates on which solder paste has been printed by the printing device are inspected by an inspection machine after printing, and the average solder volume ratio of the solder paste transferred to each substrate is obtained. If the average solder volume ratio falls below a warning threshold, a warning message urging the user to clean the mask is displayed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-226175 Summary of the Invention [Problem to be solved by the invention]

[0004] It is known that when solder is printed on multiple boards in succession, solder remains inside small openings, causing the printed solder to fade (reducing the solder volume ratio), and solder remains on the backside of large openings, causing the printed solder to bleed (increasing the solder volume ratio). However, conventional techniques, including Patent Document 1, use the average solder volume ratio for each board to determine the timing of cleaning, which poses the following problem: In a mask that contains a mixture of small openings, which tend to reduce the solder volume ratio, and large openings, which tend to increase the solder volume ratio, the average solder volume ratio is determined to be normal even though the condition of the mask has deteriorated due to continuous printing, which can result in inappropriate mask cleaning.

[0005] Therefore, an object of the present disclosure is to provide a printing system, a printing apparatus, and a printing method that are capable of cleaning a mask at an appropriate timing. [Means for solving the problem]

[0006] The printing system of the present disclosure is a printing system for printing solder on a substrate, and includes: a printing means for printing solder on the substrate using a mask having a plurality of openings; a cleaning means for cleaning the mask; an information acquisition means for acquiring information regarding the solder volume ratio or solder area ratio of a plurality of printed locations corresponding to the plurality of openings on the substrate on which solder has been printed by the printing means; and a judgment means for determining whether cleaning of the mask is necessary based on the distribution of the solder volume ratio or the distribution of the solder area ratio of a first substrate derived from the acquired information; and when the judgment means determines that cleaning of the mask is necessary, the cleaning means cleans the mask before the printing means prints solder on a second substrate.

[0007] The printing device disclosed herein is a printing device that prints solder on a substrate using a mask having a plurality of openings, and is equipped with a cleaning means for cleaning the mask, an information acquisition means for acquiring information regarding the solder volume ratio or solder area ratio of a plurality of printed locations corresponding to the plurality of openings on the substrate on which the solder is printed, and a judgment means for determining whether cleaning of the mask is necessary based on the distribution of the solder volume ratio or the distribution of the solder area ratio of a first substrate derived from the acquired information, and when the judgment means determines that cleaning of the mask is necessary, the cleaning means cleans the mask before printing solder on a second substrate.

[0008] The printing method disclosed herein is a printing method for printing solder on a substrate using a mask having a plurality of openings, which includes printing solder on a first substrate using the mask, obtaining information regarding the solder volume ratio or solder area ratio of a plurality of printed locations on the first substrate corresponding to the plurality of openings on the first substrate on which the solder is printed, determining whether cleaning of the mask is necessary based on the distribution of the solder volume ratio or the distribution of the solder area ratio of the first substrate derived from the obtained information, and if it is determined that cleaning of the mask is necessary, cleaning the mask before printing solder on a second substrate. [Effects of the Invention]

[0009] According to the present disclosure, the mask can be cleaned at an appropriate time. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating the configuration of a printing system according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is a diagram illustrating the configuration of a printing device according to an embodiment of the present disclosure. [Figure 3] FIG. 1 is a block diagram illustrating a configuration of a control system of a printing system according to an embodiment of the present disclosure. [Figure 4](a) (b) (c) is an explanatory diagram of a printing process using a mask immediately after cleaning by a printing apparatus according to an embodiment of the present disclosure. [Figure 5] (a) (b) (c) is an explanatory diagram of a printing process using masks printed continuously by a printing device according to an embodiment of the present disclosure. [Figure 6] 1A, 1B, 1C, and 1D are explanatory diagrams showing an example of the transition of the distribution of the solder volume ratio during continuous printing by a printing device according to an embodiment of the present disclosure. [Figure 7] FIG. 10 is an explanatory diagram of the timing of cleaning a mask during continuous printing by a printing apparatus according to an embodiment of the present disclosure. [Figure 8] 1 is a flow diagram of a printing method according to an embodiment of the present disclosure; [Figure 9] 1 is a flow diagram of a determination method according to an embodiment of the present disclosure; DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present disclosure will be described in detail below with reference to the drawings. The configurations, shapes, etc. described below are examples for explanation purposes and can be modified as appropriate depending on the specifications of the printing system, printing device, inspection device, and management computer. Corresponding elements in all drawings will be denoted by the same reference numerals below, and duplicated explanations will be omitted. In FIG. 2 and in some sections described below, two axes that are orthogonal to each other in a horizontal plane are shown: an X-axis in the substrate transport direction (a direction perpendicular to the paper surface in FIG. 2 ), and a Y-axis that is orthogonal to the substrate transport direction (a left-right direction in FIG. 2 ). In FIG. 2 and in some sections described below, a Z-axis (a vertical direction in FIG. 2 ) is shown as a height direction that is orthogonal to the horizontal plane.

[0012] First, the configuration of a printing system 1 will be described with reference to FIG. 1. FIG. 1 is an explanatory diagram of the configuration of a printing system according to an embodiment of the present disclosure. The printing system 1 is configured by connecting a printing device M1 and an inspection device M2 in series from upstream (left side of the page) to downstream (right side of the page) in the substrate transport direction. The printing device M1 and the inspection device M2 are connected to a management computer 3 via a communication network 2. Note that the printing system 1 is a group of operation devices connected via the communication network 2, and the printing device M1 and the inspection device M2 do not necessarily have to be physically connected. The management computer 3 stores production data, including control programs used by each device, inspection result information, and the like, and transmits and receives information between the printing device M1 and the inspection device M2.

[0013] Printing device M1 prints cream solder onto a board delivered from upstream through multiple openings in a mask. Inspection device M2 is equipped with a 3D sensor, inspection camera, etc., and inspects the condition and amount of solder printed on the top surface of the board delivered from printing device M1 based on an inspection position (XY coordinates) determined by the pre-stored positions of the openings in the mask. The 3D sensor of inspection device M2 detects the solder volume Vd, which is the three-dimensional size of the solder printed on the board. The inspection camera of inspection device M2 detects the solder area Sd, which is the two-dimensional spread of the solder printed on the board.

[0014] In Fig. 1, inspection device M2 calculates a solder volume ratio Rv (Rv = Vi / Vd), which is the ratio between an ideal solder volume Vi, which is an ideal solder volume determined based on the size and thickness of the mask opening, and a detected solder volume Vd. In addition, inspection device M2 calculates a solder area ratio Rs (Rs = Sd / Si), which is the ratio between an ideal solder area Si, which is an ideal solder area determined based on the size of the mask opening (length in the X-axis direction, length in the Y-axis direction), and a detected solder area Sd. The ideal solder volume Vi and ideal solder area Si for each inspection position are stored in advance in inspection device M2.

[0015] The solder volume Vd, solder area Sd, calculated solder volume ratio Rv, and solder area ratio Rs detected by inspection device M2 are sent to management computer 3 and also to printing device M1. Printing system 1 is placed upstream of the mounting board production line where components are mounted on boards, and boards that have completed inspection by inspection device M2 are transported to a component mounting device or the like placed downstream.

[0016] Next, the configuration of the printing device M1 will be described with reference to FIG. 2. FIG. 2 is an explanatory diagram of the configuration of a printing device according to an embodiment of the present disclosure. The printing device M1 is provided with a pair of transport conveyors 5 extending along the X-axis on a base 4. A print control unit C is provided on the base 4. The transport conveyors 5 are controlled by the print control unit C, and transport the substrate B received from the upstream side of the printing device M1 along the X-axis and carry it out to the downstream side of the printing device M1. A substrate holding unit 6 controlled by the print control unit C is provided near the center of the transport conveyors 5 in the X-axis direction. The substrate holding unit 6 receives the substrate B transported by the transport conveyors 5 and holds it in a predetermined clamp position.

[0017] A mask 7 having a plurality of openings 7a for printing solder Pst on the substrate B and having mask side marks (not shown) formed thereon is placed above the substrate holding part 6. The mask 7 has a rectangular flat plate shape extending across the XY plane, and its outer periphery is supported by a frame member 7w.

[0018] In Figure 2, an XY table 8, a θ table 9, and a substrate lifting mechanism 10 are provided on a base 4 in this order from bottom to top. The XY table 8 moves the θ table 9 in a horizontal plane (X-axis direction, Y-axis direction). The θ table 9 rotates the substrate lifting mechanism 10 by θ around the Z axis. The substrate lifting mechanism 10 supports the substrate holder 6 from below and raises and lowers it (arrow a1). The XY table 8, the θ table 9, and the substrate lifting mechanism 10 are controlled by a printing controller C.

[0019] In Fig. 2, a camera unit 12 incorporating a camera for substrate recognition and a camera for mask recognition is provided below the mask 7. The camera unit 12 moves in a horizontal plane (arrow a2) by a camera movement mechanism 13 (see Fig. 3) controlled by the print control unit C. The camera unit 12 moves between the substrate B and the mask 7 to capture images of the substrate-side marks for alignment formed on the substrate B and the mask-side marks for alignment formed on the mask 7. The print control unit C recognizes the positions of the mask-side marks and the substrate-side marks based on the images captured by the camera unit 12.

[0020] Based on the mark recognition results, the printing control unit C controls the XY table 8, the θ table 9, and the substrate lifting mechanism 10 to align the position and orientation of the multiple openings 7a formed in the mask 7 with the lands Ba (see Figure 4) formed on the substrate B held by the substrate holding unit 6. Next, the printing control unit C raises the substrate holding unit 6 to bring the substrate B into contact with the mask 7 from below. In this way, the XY table 8, the θ table 9, and the substrate lifting mechanism 10 constitute a substrate positioning mechanism 11 that moves the substrate holding unit 6 to align the substrate B held by the substrate holding unit 6 with the mask 7.

[0021] In Figure 2, a print head 20 is provided above the mask 7, which is moved along the Y axis (arrow a3) by a print head moving mechanism 14 (see Figure 3). The print head 20 is provided with a moving base 21 which is moved within a horizontal plane by the print head moving mechanism 14. Two squeegee holding units 22 are arranged side by side in the Y axis direction on the moving base 21. Each squeegee holding unit 22 holds a squeegee 23 at its lower end, which extends along the X axis, and is raised and lowered by an elevating mechanism 24 provided on the moving base 21 (arrow a4). The print head moving mechanism 14 and print head 20 are controlled by a print control unit C.

[0022] 2, below the mask 7 and on the front side in the Y-axis direction, there is provided a cleaning mechanism 16 that cleans the solder Pst remaining on the rear surface of the mask 7 and in the openings 7a. The cleaning mechanism 16 moves along the Y-axis (arrow a5) by a cleaning movement mechanism 15 (see FIG. 3) controlled by the print control unit C.

[0023] The cleaning mechanism 16 can perform dry cleaning, which cleans the mask 7 with cleaning paper, and wet cleaning, which cleans the mask 7 by applying a solvent that dissolves the flux contained in the solder Pst to the cleaning paper. During the mask cleaning operation to remove the solder Pst remaining on the mask 7, the print control unit C executes mask cleaning using the wet cleaning method or the dry cleaning method in a preset pattern. In this way, the cleaning movement mechanism 15 and the cleaning mechanism 16 constitute cleaning means 19 (see FIG. 3) that cleans the mask 7.

[0024] Next, the configuration of the control system of the printing system 1 will be described with reference to Fig. 3. Fig. 3 is a block diagram showing the configuration of the control system of the printing system according to an embodiment of the present disclosure. A transfer conveyor 5, a substrate holder 6, a substrate positioning mechanism 11, a camera unit 12, a camera movement mechanism 13, a print head movement mechanism 14, a cleaning movement mechanism 15, a cleaning mechanism 16, a touch panel 17, a print communication unit 18, and a print head 20 are connected to a print control unit C provided in the printing device M1.

[0025] The touch panel 17 has a display function for displaying the operation screen of the printing device M1 on the liquid crystal panel, and an input function for inputting commands and various information by operating the displayed operation screen. The printing communication unit 18 is a network communication device that transmits and receives information between the management computer 3 and the inspection device M2 via the communication network 2.

[0026] 3, the print control unit C includes a print storage unit 30, a print processing unit 31, a cleaning processing unit 32, an information acquisition unit 33, and a determination means 34. The print storage unit 30 is a storage device that stores, for each type of substrate B, printing conditions for the print head 20 to print solder Pst on the substrate B, mask cleaning conditions for the cleaning means 19 to perform mask cleaning, and the like. The print storage unit 30 is realized by a flash memory or an HDD (Hard Disk Drive), etc.

[0027] The printing conditions include the pressure (printing pressure) with which the squeegee 23 presses the solder Pst into the multiple openings 7a, the movement speed of the squeegee 23 during printing, the separation speed at which the substrate B is separated from the mask 7 after printing, etc. The mask cleaning conditions also store various thresholds for determining whether mask cleaning is necessary, cleaning methods (wet cleaning, dry cleaning), etc.

[0028] In FIG. 3, the print processing unit 31 controls each part of the printing device M1, including the print head 20, based on the printing conditions stored in the print storage unit 30, to execute a printing job.

[0029] Here, with reference to FIGS. 4 and 5, a printing operation (printing step) in which the print processing unit 31 controls each unit to print the solder Pst on the substrate B will be described. FIGS. 4(a), 4(b), and 4(c) are explanatory diagrams of the printing operation using a mask immediately after cleaning by a printing device according to an embodiment of the present disclosure. FIGS. 5(a), 5(b), and 5(c) are explanatory diagrams of the printing operation using a mask that has been continuously printed by a printing device according to an embodiment of the present disclosure. FIG. 4 shows the printing operation using a mask 7 immediately after cleaning. That is, the solder Pst adhering to the inner walls of the openings 7a and the back surface of the mask 7 (see FIG. 5(a)) has been removed by cleaning, and no solder Pst remains on the mask 7. The mask 7 has small openings 7a (hereinafter referred to as "small openings 7a1") and large openings 7a (hereinafter referred to as "large openings 7a2") formed therein.

[0030] In FIG. 4(a), lands Ba, which are electrodes, are formed on the upper surface of substrate B. Resist Bb, which is an insulator, is formed on the upper surface of substrate B other than the lands Ba. Substrate B is moved to below mask 7 and held by substrate holder 6. First, print processor 31 controls substrate positioning mechanism 11 to align substrate B with mask 7 (alignment step). Next, print processor 31 raises substrate holder 6 (arrow b1) to bring substrate B into contact with the lower surface of mask 7 (substrate contact step).

[0031] 4(b), the printing processing unit 31 then lowers the squeegee 23 to contact the mask 7, and while sliding the squeegee 23 along the Y axis (arrow b2), pushes the solder Pst supplied onto the mask 7 into the openings 7a to transfer the solder Pst to the substrate B (transfer step). In the transfer step, the printing processing unit 31 transfers the solder Pst to the substrate B under predetermined printing conditions, in which the squeegee 23 is pressed against the mask 7 with a predetermined pressure (printing pressure) and moves the squeegee 23 at a predetermined squeegee movement speed.

[0032] 4(c), the printing processing unit 31 then separates the substrate B from the mask 7 while lowering the substrate holding unit 6 (arrow b3) (separation step). In the separation step, the printing processing unit 31 separates the substrate B from the mask 7 under separation conditions that cause the substrate B to be lowered at a predetermined downward speed. As a result, the solder Pst is printed (deposited) on the lands Ba of the substrate B.

[0033] In this way, the substrate holding unit 6, substrate positioning mechanism 11, print head moving mechanism 14, and print head 20 constitute printing means 25 that uses a mask 7 having a plurality of openings 7a to print solder Pst on the substrate B. Then, the print processing unit 31 controls the printing means 25 to print the solder Pst on the substrate B.

[0034] 4(c), when the mask 7 immediately after cleaning is used, the solder Pst is printed on the land Ba corresponding to the small opening 7a1 with an ideal size L3, which is the same as the size L1 of the small opening 7a1. Also, the solder Pst is printed on the land Ba corresponding to the large opening 7a2 with an ideal size L4, which is the same as the size L2 of the large opening 7a2. In other words, when using the mask 7 immediately after cleaning, the solder volume ratio Rv and solder area ratio Rs of the solder Pst printed on the board B are nearly 100% for both the small opening 7a1 and the large opening 7a2.

[0035] 5 shows a printing operation using a mask 7 in which the printing operation has been repeated multiple times after cleaning. Hereinafter, repeating the printing operation multiple times without cleaning the mask 7 after cleaning will be referred to as "continuous printing."

[0036] The substrate contact step (FIG. 5(a)) in which the print processing unit 31 raises the substrate holding unit 6 (arrow c1) to bring the substrate B into contact with the underside of the mask 7, the transfer step (FIG. 5(b)) in which the squeegee 23 is slid (arrow c2) to push the solder Pst into the openings 7a and transfer it to the substrate B, and the separation step (FIG. 5(c)) in which the substrate holding unit 6 is lowered (arrow c3) to separate the substrate B from the mask 7 are the same as those shown in FIG. 4, and detailed explanations will be omitted. Due to the continuous printing, the solder Pst remains on the inner walls of the small openings 7a1 of the mask 7, and the solder Pst remains on the back surface of the mask 7 around the large openings 7a2.

[0037] 5, the principle behind the solder Pst remaining on the inner wall of the small opening 7a1 due to continuous printing is as follows: When the size L1 of the opening 7a is small, the force that causes the solder Pst to adhere to the inner wall of the opening 7a is greater than the force that causes the solder Pst to be sheared off, and the sheared solder Pst remains on the inner wall of the small opening 7a1 (solder clogging) in the separation step (arrow c3 in FIG. 5(c)).

[0038] The principle behind the solder Pst remaining on the back surface of the mask 7 around the large opening 7a2 during continuous printing is as follows. That is, when the size L2 of the opening 7a is large, the force with which the squeegee 23 (arrow c2 in FIG. 5(b)) sliding around the periphery of the opening 7a during the transfer process presses the solder Pst into the opening 7a increases, and the solder Pst is also pressed into the space around the opening 7a surrounded by the back surface of the mask 7, the resist Bb, and the lands Ba. During the subsequent separation process, some of the solder Pst pressed around the large opening 7a2 remains on the substrate B (solder ooze), and the remaining solder Pst remains on the back surface of the mask 7.

[0039] 5(c), when a continuously printed mask 7 is used, solder Pst of size L5, which is smaller than the size L1 of the small opening 7a1, is printed on the land Ba corresponding to the small opening 7a1. That is, in the small opening 7a1, the solder volume ratio Rv and solder area ratio Rs of the solder Pst printed on the board B are smaller than 100%. Also, solder Pst of size L6, which is larger than the size L2 of the large opening 7a2, is printed on the land Ba corresponding to the large opening 7a2. That is, in the large opening 7a2, the solder volume ratio Rv and solder area ratio Rs of the solder Pst printed on the board B are larger than 100%.

[0040] 3, the information acquiring unit 33 acquires the solder volume Vd or solder volume ratio Rv, or the solder area Sd or solder area ratio Rs of the printed portions of the solder Pst corresponding to the openings 7a of the board B on which the solder Pst was printed by the printing device M1 from the inspection device M2 or the management computer 3 via the printing communication unit 18. In other words, the information acquiring unit 33 and the printing communication unit 18 constitute information acquiring means 26 that acquires information (hereinafter simply referred to as "printed solder information") relating to the solder volume ratio Rv or solder area ratio Rs of the multiple printed portions corresponding to the multiple openings 7a of the board B on which the solder was printed by the printing means 25.

[0041] The determination means 34 determines whether cleaning of the mask 7 is necessary based on the printed solder information acquired by the information acquisition means 26. Specifically, the determination means 34 derives the distribution of the solder volume ratio Rv or the distribution of the solder area ratio Rs from the printed solder information, and determines whether cleaning of the mask 7 is necessary based on these distributions. The cleaning processing unit 32 controls the cleaning means 19 (cleaning movement mechanism 15, cleaning mechanism 16) based on the determination of the determination means 34 to perform cleaning of the mask 7.

[0042] In this way, the determination means 34 determines whether cleaning of the mask 7 is necessary based on the distribution of the solder volume ratio Rv or the distribution of the solder area ratio Rs of the substrate B (first substrate) derived from the printed solder information acquired by the information acquisition means 26. Then, when the determination means 34 determines that cleaning of the mask 7 is necessary, the cleaning processing unit 32 causes the cleaning means 19 to clean the mask 7 before the printing means 25 prints the solder Pst on the substrate B (second substrate) that is subsequent to the first substrate.

[0043] Here, with reference to Figure 6, the determination by the determination means 34 as to whether cleaning of the mask 7 is necessary will be described. Figures 6(a), (b), (c), and (d) are explanatory diagrams showing an example of the transition of the distribution of solder volume ratio during continuous printing by a printing device according to an embodiment of the present disclosure. Here, a method for determining whether cleaning of the mask 7 is necessary based on the distribution of solder volume ratio Rv will be described. Note that the method for determining whether cleaning of the mask 7 is necessary based on the solder area ratio Rs is similar, and a detailed description thereof will be omitted.

[0044] FIG. 6 shows a schematic example of the distribution of the solder volume fraction Rv of a substrate B on which solder Pst has been printed using a mask 7 immediately after cleaning (FIG. 6(a)), and the distribution of the solder volume fraction Rv of a substrate B on which solder Pst has been printed using a mask 7 that has been continuously printed (FIGS. 6(b) to 6(d)). The number of continuous printings increases in the order of FIG. 6(b), FIG. 6(c), and FIG. 6(d). In FIGS. 6(a) to 6(d), the vertical axis shows the solder volume fraction Rv, and the horizontal axis shows the frequency distribution of the number of solder Pst points (number of printed locations) printed on the substrate B.

[0045] 6(a), when a mask 7 immediately after cleaning is used, both the distribution of solder volume fraction Rv in the printed area corresponding to the small opening 7a1 shown by the dashed-dotted line and the distribution of solder volume fraction Rv in the printed area corresponding to the large opening 7a2 shown by the dotted line have a single peak centered at 100%. Therefore, the distribution of solder volume fraction Rv in the entire printed area, shown by the solid line and including both the printed areas corresponding to the small opening 7a1 and the large opening 7a2, also has a single peak centered at 100%. In other words, the distribution of solder volume fraction Rv when a mask 7 immediately after cleaning is used has a single peak centered at 100%.

[0046] 6(b) to 6(d), when a continuously printed mask 7 is used, the center of the distribution of solder volume fraction Rv in the printed area corresponding to the small opening 7a1 tends to gradually decrease from 100%. That is, the distribution of solder volume fraction Rv in the printed area corresponding to the small opening 7a1 shifts in the direction of decreasing solder volume fraction Rv. Also, the center of the distribution of solder volume fraction Rv in the printed area corresponding to the large opening 7a2 tends to gradually increase from 100%. That is, the distribution of solder volume fraction Rv in the printed area corresponding to the large opening 7a2 shifts in the direction of increasing solder volume fraction Rv.

[0047] In this way, when a mask 7 that has been printed multiple times using continuous printing is used, the distribution of solder volume fraction Rv in the printed areas corresponding to the small openings 7a1 and the distribution of solder volume fraction Rv in the printed areas corresponding to the large openings 7a2 move away from each other. As a result, two peaks appear in the overall distribution of solder volume fraction Rv. As the number of continuous printing operations increases, the distance G between the peaks of the two peaks tends to increase. Furthermore, a valley F appears between the two peaks, and the height (number of points) of the valley F tends to decrease.

[0048] In FIG. 6(b), the position of valley F1 is larger (higher) than the judgment threshold score Nt. In this case, the judgment means 34 does not judge whether cleaning of the mask 7 is necessary. On the other hand, in FIGS. 6(c) and 6(d), the positions of valleys F2 and F3 are smaller (lower) than the judgment threshold score Nt. In this case, the judgment means 34 judges whether cleaning of the mask 7 is necessary. In this way, the judgment means 34 judges whether cleaning of the mask 7 is necessary when the minimum value (valleys F1 to F3) of the solder volume ratio Rv (or solder area ratio Rs) between the peaks of the two mountains is equal to or less than a predetermined value (judgment threshold score Nt).

[0049] The judgment threshold score Nt may be set in advance as one of the mask cleaning conditions, or may be set based on the height of the peak of the distribution of the solder volume fraction Rv immediately after cleaning. For example, the judgment threshold score Nt may be set to a score that is 75% of the height of the peak of the distribution of the solder volume fraction Rv immediately after cleaning.

[0050] In FIGS. 6(c) and 6(d), the determination means 34 determines the necessity of cleaning the mask 7 based on the intervals G1 and G2 between the peaks of two mountains sandwiching the valleys F2 and F3 of the distribution of the solder volume ratio Rv (or the distribution of the solder area ratio Rs). Specifically, when the intervals G1 and G2 are greater than or equal to the determination threshold interval Gt, it is determined that cleaning of the mask 7 is necessary. In the case of FIG. 6(c), since the interval G1 is narrower than the determination threshold interval Gt (G1 < Gt), the determination means 34 determines that cleaning of the mask 7 is unnecessary. On the other hand, in the case of FIG. 6(d), since the interval G2 is wider than the determination threshold interval Gt (G2 > Gt), the determination means 34 determines that cleaning of the mask 7 is necessary.

[0051] Thus, when the distribution of the solder volume ratio Rv (or the distribution of the solder area ratio Rs) of the substrate B (first substrate) has two peaks and the interval G2 between the peaks of the two mountains is greater than or equal to a predetermined value (determination threshold interval Gt), the determination means 34 determines that cleaning of the mask 7 is necessary.

[0052] Note that in FIG. 6, the horizontal axis of the distribution of the solder volume ratio Rv is represented by the number of points (frequency), but probabilities obtained by normalizing the frequency may be used on the horizontal axis of the distribution of the solder volume ratio Rv. Further, the determination means 34 may determine the necessity of cleaning the mask 7 based on the distribution of the solder volume difference ((Vd - Vi) / Vi) based on the difference between the ideal solder volume Vi and the detected solder volume Vd instead of the solder volume ratio Rv (Vi / Vd). In the case of the distribution of the solder volume difference, the center of one peak immediately after cleaning becomes 0 (zero).

[0053] In FIG. 6, when the distribution of the solder volume ratio Rv of the substrate B (first substrate) overlaps with the warning area A1 that is greater than or equal to the first upper limit volume ratio Rh1 or less than or equal to the first lower limit volume ratio Rl1, the determination means 34 determines that cleaning of the mask 7 is necessary (see count "5" in FIG. 7). Alternatively, when the distribution of the solder area ratio Rs of the substrate B (first substrate) overlaps with the warning area A1 that is greater than or equal to the first upper limit area ratio or less than or equal to the first lower limit area ratio, the determination means 34 determines that cleaning of the mask 7 is necessary.

[0054] Furthermore, when the distribution of the solder volume ratio Rv of the substrate B (the first substrate) overlaps with a defective area A2 that is greater than a second upper volume ratio Rh2 (Rh1 < Rh2) or less than a second lower volume ratio Rl2 (Rl1 > Rl2) which is greater than the first lower volume ratio Rl1, the determination means 34 determines that the first substrate is defective (see count "11" in FIG. 7). Alternatively, when the distribution of the solder area ratio Rs of the substrate B (the first substrate) overlaps with a defective area A2 that is greater than a second upper area ratio which is greater than the first upper area ratio or less than a second lower area ratio which is less than the first lower area ratio, the determination means 34 determines that the first substrate is defective. When the determination means 34 determines that the first substrate is defective, it causes the touch panel 17 to display (notify) that fact.

[0055] Next, referring to FIG. 7, the timing of cleaning the mask 7 when continuously printing the solder Pst on the substrate B using the mask 7 in the printing apparatus M1 will be described. FIG. 7 is an explanatory diagram of the timing of cleaning the mask in continuous printing by the printing apparatus according to an embodiment of the present disclosure. In FIG. 7, the count of the substrate B continuously printed on the horizontal axis represents the solder volume ratio Rv on the vertical axis, and the distribution of the solder volume ratio Rv is schematically represented for each count. Hereinafter, the substrate B with a count of "1" will be referred to as the "first substrate B1" and the like.

[0056] In FIG. 7, it is assumed that the mask 7 is cleaned before printing the solder Pst on the first substrate B1. The distribution of the solder volume ratio Rv of the first substrate B1 immediately after cleaning has one peak as in FIG. 6(a), and since no valley F occurs, the determination means 34 does not determine whether cleaning of the mask 7 is necessary. That is, before printing the solder Pst on the second substrate B2, cleaning of the mask 7 is not performed. The same applies to the distributions of the solder volume ratios Rv of the fourth substrate B4, the sixth substrate B6, and the eighth substrate B8, and cleaning of the mask 7 is not performed before printing the solder Pst on the fifth substrate B5, the seventh substrate B7, and the ninth substrate B9.

[0057] The distribution of the solder volume fraction Rv of the second substrate B2 has two peaks and a valley F4. However, as in Figure 6(b), the position of the valley F4 is higher than the judgment threshold score Nt, so the judgment means 34 does not judge whether cleaning of the mask 7 is necessary. In other words, cleaning of the mask 7 is not performed before printing the solder Pst on the third substrate B3.

[0058] In Figure 7, two peaks appear in the distribution of the solder volume fraction Rv for the third substrate B3, and as in Figures 6(c) and 6(d), the position of the valley F5 is lower than the judgment threshold score Nt, so the judgment means 34 judges whether cleaning of the mask 7 is necessary. Then, because the distance G3 between the peaks of the two peaks is equal to or greater than the judgment threshold distance Gt, the judgment means 34 determines that cleaning is necessary. Then, the cleaning processing unit 32 cleans the mask 7 before printing the solder Pst on the fourth substrate B4. The distributions of the solder volume fraction Rv for the seventh substrate B7 and the tenth substrate B10 are similar, and cleaning of the mask 7 is performed before printing the solder Pst on the eighth substrate B8 and the eleventh substrate B11.

[0059] Because the distribution of solder volume fraction Rv of the fifth substrate B5 overlaps with warning area A1, which is equal to or less than the first lower limit volume fraction Rl1, judgment means 34 judges that cleaning is necessary. Then, cleaning processing unit 32 performs cleaning of mask 7 before printing solder Pst on sixth substrate B6. Because the distribution of solder volume fraction Rv of the eleventh substrate B11 overlaps with defective area A2, which is equal to or greater than the second upper limit volume fraction Rh2, judgment means 34 judges that the eleventh substrate B11 is defective. Then, a message is displayed on touch panel 17 indicating that the eleventh substrate B11 has a printing defect.

[0060] Next, a printing method in the printing device M1 that prints solder Pst on the substrate B using a mask 7 having a plurality of openings 7a will be described with reference to Figures 6 and 7, along with the flows in Figures 8 and 9. Figure 8 is a flow diagram of the printing method according to an embodiment of the present disclosure. Figure 9 is a flow diagram of the determination method according to an embodiment of the present disclosure.

[0061] In FIG. 8, first, the transfer conveyor 5 transfers a first board (such as the first board B1 in FIG. 7) into the printing device M1 (ST1: board transfer step). Next, the printing means 25 uses a mask 7 to print solder on the first board (ST2: printing step). Next, the transfer conveyor 5 transfers the first board on which the solder Pst has been printed out of the printing device M1 (ST3: board transfer step). The transferred first board is transferred to the inspection device M2, where the solder volume ratio Rv (or solder area ratio Rs) is detected.

[0062] Next, information acquisition means 26 acquires printed solder information relating to the solder volume ratio Rv (or solder area ratio Rs) of multiple printed locations corresponding to the multiple openings 7a of the first substrate on which the solder Pst is printed from inspection device M2 (ST4: information acquisition step). Next, judgment means 34 judges whether cleaning of mask 7 is necessary based on the distribution of solder volume ratio Rv (or distribution of solder area ratio Rs) of the first substrate derived from the acquired printed solder information (ST5: judgment step).

[0063] 9, in the judgment step (ST5) (method of judging whether cleaning is necessary), the judgment means 34 first judges whether the distribution of solder volume fraction Rv (or the distribution of solder area fraction Rs) of the first substrate overlaps with a defective area A2 that is equal to or greater than the second upper limit volume fraction Rh2 or equal to or less than the second lower limit volume fraction Rl2 (equal to or greater than the second upper limit area fraction or equal to or less than the second lower limit area fraction) (ST11: defect judgment step). If the distribution of solder volume fraction Rv of the first substrate overlaps with a defective area A2 (Yes in ST11), the judgment means 34 causes the touch panel 17 to report this fact (ST12: defect reporting step).

[0064] If the distribution of the solder volume fraction Rv of the first substrate does not overlap the defective area A2 (No in ST11), the judgment means 34 judges whether the distribution of the solder volume fraction Rv (or the distribution of the solder area fraction Rs) of the first substrate overlaps with the warning area A1 that is equal to or greater than the first upper limit volume fraction Rh1 or equal to or less than the first lower limit volume fraction Rl1 (above the first upper limit area fraction or below the first lower limit area fraction) (ST13: warning judgment step).If the distribution of the solder volume fraction Rv of the first substrate overlaps with the warning area A1 (Yes in ST13), the judgment means 34 judges that cleaning of the mask 7 is necessary (ST14).

[0065] 9, if the distribution of the solder volume fraction Rv of the first substrate does not overlap the warning area A1 (No in ST13), the judgment means 34 judges whether the distribution of the solder volume fraction Rv (or the distribution of the solder area fraction Rs) of the first substrate has two peaks (ST15: two-peak judgment step). If the distribution of the solder volume fraction Rv of the first substrate does not have two peaks (No in ST15), that is, if the distribution of the solder volume fraction Rv of the first substrate has one peak (FIG. 6(a)), the judgment means 34 judges that cleaning of the mask 7 is not necessary (ST16).

[0066] If the distribution of the solder volume fraction Rv of the first board has two peaks (Yes in ST15), the determination means 34 determines whether the height of the valley F between the two peaks is equal to or less than the determination threshold score Nt (ST17: valley height determination step). If the height of the valley F between the two peaks is higher than the determination threshold score Nt (No in ST17) (FIG. 6(b)), the determination means 34 determines that cleaning of the mask 7 is unnecessary (ST16).

[0067] If the height of the valley F between the two peaks is equal to or less than the judgment threshold score Nt (Yes in ST17), the judgment means 34 judges whether the interval G between the two peaks is equal to or greater than the judgment threshold interval Gt (ST18: peak interval judgment step). If the interval G between the two peaks is smaller than the judgment threshold interval Gt (No in ST18) (FIG. 6(c)), the judgment means 34 judges that cleaning of the mask 7 is unnecessary (ST16). On the other hand, if the interval G between the two peaks is equal to or greater than the judgment threshold interval Gt (Yes in ST18) (FIG. 6(d)), the judgment means 34 judges that cleaning of the mask 7 is necessary (ST14).

[0068] 8, if it is determined in the determination step (ST5) that cleaning of the mask 7 is not necessary (No, ST16), the process returns to the substrate carrying-in step (ST1), and a second substrate (such as the second substrate B2 or third substrate B3 in FIG. 7) is carried into the printing device M1. If it is determined in the determination step (ST5) that cleaning of the mask 7 is necessary (Yes, ST14), the cleaning means 19 cleans the mask 7 before printing the solder Pst on the second substrate (such as the fourth substrate B4 in FIG. 7) (ST6: cleaning step). Next, if there is a second substrate on which the solder Pst is to be printed next (Yes in ST8), the process returns to the substrate carrying-in step (ST1), and a second substrate (such as the fourth substrate B4 in FIG. 7) is carried into the printing device M1.

[0069] As described above, the printing device M1 of this embodiment is equipped with an information acquisition means 26 that acquires printed solder information regarding the solder volume ratio Rv (or solder area ratio Rs) of multiple printed locations corresponding to multiple openings 7a of the substrate B on which the solder Pst is printed, and a judgment means 34 that judges whether cleaning of the mask 7 is necessary based on the distribution of the solder volume ratio Rv (or the distribution of the solder area ratio Rs) of the first substrate derived from the acquired printed solder information.

[0070] Then, when the determining means 34 determines that cleaning of the mask 7 is necessary, the cleaning means 19 cleans the mask 7 before printing the solder Pst on the second board. This allows the mask 7 to be cleaned at an appropriate timing.

[0071] Although the above description has been given taking as an example a configuration in which the printing device M1 is equipped with the information acquisition means 26 and the determination means 34, the printing system 1 is not limited to this configuration. For example, the management computer 3 may be equipped with the information acquisition means 26 and the determination means 34, and the cleaning means 19 may clean the mask 7 based on a cleaning command sent from the management computer 3.

[0072] Furthermore, the inspection device M2 may be equipped with information acquisition means 26 and determination means 34, and the cleaning means 19 may clean the mask 7 based on a cleaning command sent from the inspection device M2. Furthermore, the printing device M1 may acquire the solder volume Vd (or the solder area Sd) from the inspection device M2, and calculate the solder volume ratio Rv (or the solder area ratio Rs) in the printing control unit C.

[0073] That is, the printing system 1 may be configured such that the printing device M1 includes the printing means 25 and the cleaning means 19, and either the printing device M1, the inspection device M2, or the management computer 3 includes the information acquisition means 26 and the determination means 34.

[0074] Although the embodiments have been described above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications, alterations, substitutions, additions, deletions, and equivalents within the scope of the claims, and it is understood that these also fall within the technical scope of the present disclosure. Furthermore, the components in the above-described embodiments may be combined in any manner without departing from the spirit of the invention. [Industrial Applicability]

[0075] The printing system, printing apparatus, and printing method disclosed herein have the effect of being able to clean a mask at an appropriate time, and are useful in the field of mounting components onto a substrate. [Explanation of symbols]

[0076] 1 Printing System B board 7. Mask 7a aperture 19 Cleaning means 25 Printing means 26 Information acquisition means A1 Warning Area A2 Bad area G, G1~G6 interval M1 printing device Pst solder Rv Solder volume ratio

Claims

1. 1. A printing system for printing solder on a substrate, comprising: a printing means for printing solder onto the substrate using a mask having a plurality of openings; a cleaning means for cleaning the mask; an information acquisition means for acquiring information regarding the solder volume ratio or the solder area ratio of a plurality of printed portions corresponding to the plurality of openings of the substrate on which the solder is printed by the printing means; a determination means for determining whether cleaning of the mask is necessary based on the distribution of the solder volume ratio or the distribution of the solder area ratio of the first substrate derived from the acquired information, When the determining means determines that cleaning of the mask is necessary, the cleaning means cleans the mask before the printing means prints the solder on the second substrate.

2. 2. The printing system according to claim 1, wherein the determination means determines that cleaning of the mask is necessary when the distribution of the solder volume ratio or the distribution of the solder area ratio of the first substrate has two peaks and the distance between the peaks of the two peaks is equal to or greater than a predetermined value.

3. 3. The printing system according to claim 2, wherein the determining means determines whether cleaning of the mask is necessary when the minimum value of the solder volume ratio or the solder area ratio between the peaks of the two mountains is equal to or less than a predetermined value.

4. 2. The printing system of claim 1, wherein the judgment means judges that cleaning of the mask is necessary when the distribution of the solder volume ratio of the first substrate overlaps with a warning area that is above a first upper limit volume ratio or below a first lower limit volume ratio, or when the distribution of the solder area ratio overlaps with a warning area that is above a first upper limit area ratio or below a first lower limit area ratio.

5. 5. The printing system of claim 4, wherein the judgment means judges the first substrate to be defective when the distribution of the solder volume ratio of the first substrate overlaps with a defective area that is equal to or greater than a second upper limit volume ratio that is greater than the first upper limit volume ratio or equal to or less than a second lower limit volume ratio that is less than the first lower limit volume ratio, or when the distribution of the solder area ratio overlaps with a defective area that is equal to or greater than a second upper limit area ratio that is greater than the first upper limit area ratio or equal to or less than a second lower limit area ratio that is less than the first lower limit area ratio.

6. A printing apparatus for printing solder on a substrate using a mask having a plurality of openings, a cleaning means for cleaning the mask; an information acquisition means for acquiring information regarding the solder volume ratio or the solder area ratio of a plurality of printed portions corresponding to the plurality of openings of the substrate on which solder is printed; a determination means for determining whether cleaning of the mask is necessary based on the distribution of the solder volume ratio or the distribution of the solder area ratio of the first substrate derived from the acquired information, When the determining means determines that cleaning of the mask is necessary, the cleaning means cleans the mask before printing the solder onto the second board.

7. 1. A printing method for printing solder on a substrate using a mask having a plurality of openings, comprising: printing solder onto a first substrate using the mask; acquiring information on the solder volume ratio or the solder area ratio of a plurality of printed portions corresponding to the plurality of openings of the first substrate on which solder is printed; determining whether cleaning of the mask is necessary based on the distribution of the solder volume ratio or the distribution of the solder area ratio of the first substrate derived from the acquired information; If it is determined that cleaning of the mask is necessary, the mask is cleaned before printing the solder onto the second substrate.

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