JP4910880B2 - Screen printing method - Google Patents

Description

The present invention relates to a screen printing how to print a paste such as a solder paste or conductive paste on the substrate.

  In mounting an electronic component, a solder paste is applied to the surface of the substrate prior to mounting the electronic component on the substrate. As a solder application method, a screen printing method is widely used, and after the printing process, a printing inspection for inspecting the printing state of the solder paste is performed. This print inspection is to determine whether or not the solder paste is correctly printed on the printed part by picking up an image of the substrate after screen printing with a camera and performing image recognition processing on the image pickup result. Inspection results are output for inspection items such as “bleeding” that is excessively large in the print amount and “bleed” that protrudes outward from the print range and “blur” that is excessively small in the print target portion.

These inspections are generally performed by comparing inspection quantities such as a print area calculated by image recognition processing with a preset inspection threshold value, and pass / fail judgment is made with the inspection threshold as a boundary. The Along with this, for the predetermined inspection items, the calculated inspection quantities are used for purposes other than the pass / fail judgment, for example, the necessity of feedback for changing the operation parameter by judging the tendency of the specific item of the printing state. (See Patent Document 1).
JP 2002-19071 A

  By the way, the tendency of occurrence of printing defects in screen printing often depends on the local state of the mask plate, and if any abnormality occurs in the state of the mask plate, the same tendency is observed at the same location on the substrate after printing. Are detected continuously. However, in the conventional screen printing, including the example shown in the above-mentioned prior art document, the cleaning operation for the entire mask plate is performed even when a printing defect due to some abnormality in the mask plate is detected. Only feedback information for instructing is issued, and a measure for appropriately dealing with a printing defect locally generated is not always performed. As described above, in the conventional screen printing apparatus, it is impossible to effectively deal with printing defects that occur locally and continuously, which is a cause of a decrease in print quality.

The present invention is to effectively prevent the printing failure that occurs locally continuous, and an object thereof is to provide a screen printing how that can ensure the print quality.

In the screen printing method of the present invention, the substrate is brought into contact with the mask plate provided with the pattern holes, the paste is supplied onto the mask plate, and the squeegee is slid, whereby the paste is applied to the substrate through the pattern holes. A screen printing method for printing, wherein a printing inspection is performed on a printed state of a paste on a printed substrate, in which an inspection item includes “faint” in which an amount of printing at an area to be printed is excessively small, and a predetermined inspection is performed on the inspection item A print inspection process that outputs a determination result based on a threshold value, and a case where, based on the determination result, it is determined that a print defect having a large degree due to the state of the pattern hole is continuously occurring in the same part. imaging the lower surface of the mask plate, the pattern holes in the mask plate by performing the recognition processing of the data captured A mask inspection process for inspecting the state and identifying a cleaning required site that needs cleaning, and displaying the cleaning required site on the screen and instructing it. Clean by work.

According to the present invention, the printing state of the paste in the substrate after printing, based-out the inclusive of print inspection determination result to the inspection item quantity printing the "blurring" of the under-the printing target site, the state of the pattern holes When it is determined that printing defects with a high degree of occurrence are continuously occurring in the same part, the lower surface of the mask plate is imaged, and the pattern hole state in the mask plate is inspected by performing recognition processing of the captured data. Then, the site requiring cleaning is specified, the site requiring cleaning is indicated on the screen, and the machine operator manually cleans the site requiring cleaning according to this display, thereby continuously locally. In this way, it is possible to effectively prevent printing defects that occur and to ensure printing quality.

  Next, embodiments of the present invention will be described with reference to the drawings. 1 is a front view of a screen printing apparatus according to an embodiment of the present invention, FIG. 2 is a side view of the screen printing apparatus according to an embodiment of the present invention, and FIG. 3 is a screen printing apparatus according to an embodiment of the present invention. FIG. 4 is an explanatory view of the structure of the cleaning unit of the screen printing apparatus according to the embodiment of the present invention. FIG. 5 is an explanatory view of the operation of the cleaning unit of the screen printing apparatus according to the embodiment of the present invention. FIG. 7 is a block diagram showing the configuration of the control system of the screen printing apparatus according to the embodiment of the present invention, and FIG. 7 is an explanatory diagram of the mask cleaning operation in the screen printing method of the embodiment of the present invention.

  First, the structure of the screen printing apparatus will be described with reference to FIG. 1, FIG. 2, and FIG. In FIG. 1, the screen printing apparatus is configured by disposing a screen printing mechanism 13 above a substrate positioning unit 1. The substrate positioning unit 1 is configured by stacking a Y-axis table 2, an X-axis table 3, and a θ-axis table 4, and further combining a first Z-axis table 5 and a second Z-axis table 6 thereon. Yes. The configuration of the first Z-axis table 5 will be described. Similarly, on the upper surface side of the horizontal base plate 4 a provided on the upper surface of the θ-axis table 4, the horizontal base plate 5 a is held up and down by an elevating guide mechanism (not shown). The base plate 5a is moved up and down by a Z-axis lifting mechanism configured to rotationally drive a plurality of feed screws 5c through a belt 5d by a motor 5b.

  A vertical frame 5e is erected on the base plate 5a, and a substrate transport mechanism 8 is held at the upper end of the vertical frame 5e. The substrate transport mechanism 8 includes two transport rails arranged in parallel to the substrate transport direction (X direction—the direction perpendicular to the paper surface in FIG. 1), and both end portions of the substrate 10 to be printed by these transport rails. It supports and conveys. By driving the first Z-axis table 5, the substrate 10 held by the substrate transport mechanism 8 can be moved up and down together with the substrate transport mechanism 8 with respect to a screen printing mechanism 13 described later. As shown in FIGS. 2 and 3, the substrate transport mechanism 8 extends to the upstream side (left side in FIGS. 2 and 3) and the downstream side, and the substrate 10 carried from the upstream side is transported by the substrate transport mechanism 8. Further, the substrate is positioned by the substrate positioning unit 1. Then, the substrate 10 after being printed by a screen printing mechanism to be described later is carried out downstream by the substrate transport mechanism 8.

The configuration of the second Z-axis table 6 will be described. A horizontal base plate 6a is disposed between the substrate transport mechanism 8 and the base plate 5a so as to be movable up and down along a lifting guide mechanism (not shown). The base plate 6a is moved up and down by a Z-axis lifting mechanism configured to rotationally drive a plurality of feed screws 6c through a belt 6d by a motor 6b. On the upper surface of the base plate 6a, there is disposed a substrate lower receiving portion 7 having a lower receiving surface for holding the substrate 10 on the upper surface.

  By driving the second Z-axis table 6, the substrate receiving unit 7 moves up and down with respect to the substrate 10 held by the substrate transport mechanism 8. The substrate receiving portion 7 supports the substrate 10 from the lower surface side when the lower receiving surface of the substrate lower receiving portion 7 contacts the lower surface of the substrate 10. A clamp mechanism 9 is disposed on the upper surface of the substrate transport mechanism 8. The clamp mechanism 9 includes two clamp members 9a that are arranged opposite to each other on the left and right sides, and the substrate 10 is clamped and fixed from both sides by moving the clamp member 9a on one side forward and backward by the drive mechanism 9b.

  Next, the screen printing mechanism 13 disposed above the substrate positioning unit 1 will be described. 1 and 2, a mask plate 12 is extended on the mask frame 11, and the mask plate 12 corresponds to the shape and position of the electrode 10a to be printed on the substrate 10 (see FIG. 3). The pattern hole 12a is provided. A squeegee head 13 a is disposed on the mask plate 12, and the squeegee head 13 a has a configuration in which a squeegee lifting mechanism 15 that lifts and lowers the squeegee 16 on a horizontal plate 14 is disposed. By driving the squeegee lifting mechanism 15, the squeegee 16 moves up and down and comes into contact with the upper surface of the mask plate 12.

  As shown in FIG. 2, a guide rail 27 is disposed in the Y direction on a bracket 26 disposed on the vertical frame 25, and a slider 28 slidably fitted on the guide rail 27 is provided on the plate 14. Connected to both ends. Thereby, the squeegee head 13a is slidable in the Y direction. The plate 14 is horizontally moved in the Y direction by a squeegee moving means comprising a nut 30, a feed screw 29, and a squeegee moving motor (not shown) that rotationally drives the feed screw 29.

  Next, the mask cleaning mechanism for cleaning the lower surface of the mask plate 12 and the camera head unit 17 will be described. In the present embodiment, as a cleaning mechanism, a wiping cleaning unit 18A for performing a cleaning operation by wiping the entire lower surface of the mask plate 12, and a cleaning by suction for a specific portion of the mask plate 12 as a target. A configuration including a suction cleaning unit 18B for performing the operation is adopted.

  As shown in FIG. 1, the cleaning head unit 18 is configured to move in the Y direction integrally with the camera head unit 17 that images the substrate 10 and the mask plate 12. The camera head unit 17 includes a substrate recognition camera 17a for imaging the substrate 10 from above and a mask recognition camera 17b for imaging the mask plate 12 from the lower surface side, and is mounted on the head X-axis table 19. And move integrally in the Y direction. By moving the camera head unit 17 in the X direction and the Y direction to be positioned between the substrate positioning unit 1 and the mask plate 12, recognition of the substrate 10 and recognition of the mask plate 12 can be performed simultaneously.

  In FIG. 2, a guide rail 31 is disposed on the vertical frame 25 in the Y direction, and a slider 32 slidably fitted to the guide rail 31 is coupled to the head X-axis table 19 via a bracket 19a. Yes. As a result, the head X-axis table 19 is slidable in the Y direction. The head X-axis table 19 is horizontally moved in the Y direction by a head Y-axis moving mechanism 20 including a nut 34, a feed screw 33, and a head moving motor (not shown) that rotationally drives the feed screw 33.

  The head X-axis table 19 is equipped with a camera head unit 17 and a suction cleaning unit 18B. By driving the head X-axis table 19, the camera head unit 17 and the suction cleaning unit 18B move integrally in the X direction. To do. The head X axis table 19 and the head Y axis moving mechanism 20 constitute a head moving means for moving the camera head unit 17, the wiping cleaning unit 18A, and the suction cleaning unit 18B. In addition, it may replace with the structure which moves the camera head unit 17 and the suction cleaning unit 18B integrally, and you may make it provide the dedicated moving means to move each separately.

  Next, the printing operation by the screen printing mechanism 13 will be described. First, when the substrate 10 is carried into the printing position by the substrate transport mechanism 8, the second Z-axis table 6 is driven to raise the substrate receiving portion 7 and receive the lower surface of the substrate 10. In this state, the substrate positioning unit 1 is driven to align the substrate 10 with the mask plate 12. Thereafter, the first Z-axis table 5 is driven to raise the substrate 10 together with the substrate transport mechanism 8 to contact the lower surface of the mask plate 12, and then the substrate 10 is clamped by the clamp mechanism 9. Thereby, the horizontal position of the board | substrate 10 is fixed in the squeegeeing by the squeegee head 13a. In this state, the squeegee 16 is slid on the mask plate 12 to which the solder paste as a paste is supplied, so that the solder paste is printed on the substrate 10 through the pattern holes 12a. Next, the structures of the wiping cleaning unit 18A and the suction cleaning head unit 18B will be described with reference to FIGS. As shown in FIG. 3, the wiping cleaning unit 18A includes a paper roll 22A in which unused cleaning paper is wound around a horizontal unit base, a paper roll 22B in which used cleaning paper is wound, and a wiping head 21. The cleaning paper drawn from the paper roll 22 </ b> A is collected by the paper roll 22 </ b> B via the wiping head 21.

  FIG. 4A shows a cross section in the Y direction of the wiping cleaning unit 18A shown in FIG. 3, and the cleaning paper 23 drawn out from the paper roll 22A is guided by a plurality of guide rollers 36, and the wiping head. The sheet 21 is wound around the paper roll 22 </ b> B around the pressing surface on the upper surface of 21. The wiping head 21 can be moved up and down by a head lifting mechanism 35.

  FIG. 4B shows the structure of the suction cleaning unit 18 </ b> B attached to the head X-axis table 19. In FIG. 4B, a suction head 38 is disposed on the base member 37 coupled to the moving plate 19b of the head X-axis table 19 so as to be movable up and down by a lifting mechanism 38a. The upper surface of the suction head 38 is a suction surface that contacts and sucks the lower surface of the mask plate 12, and a vacuum suction source 39 is connected to a suction hole 38 b provided in the suction surface. By driving the vacuum suction source 39, vacuum suction is performed from the suction hole 38b, and cleaning by suction can be performed on the lower surface of the mask plate 12 as a target.

  In the normal state shown in FIG. 5A, in the wiping cleaning unit 18A and the suction cleaning unit 18B, the wiping head 21 and the suction head 38 are both in the lowered state. Then, at the time of mask cleaning for cleaning the lower surface of the mask plate 12, the cleaning operation by the wiping cleaning unit 18A and the suction cleaning unit 18B is performed selectively or in combination. That is, as shown in FIG. 5B, the head lifting mechanism 35 is driven to lift the wiping head 21, and the wiping head 21 is moved to the mask plate 12 in a state where the cleaning paper 23 is pressed against the lower surface of the mask plate 12. Slide against the lower surface of Further, the suction head 38 is raised, the suction surface is pressed against a specific site to be cleaned, and the vacuum suction source 39 is driven to suck from the suction hole 38b.

  Next, the configuration of the control system will be described with reference to FIG. In FIG. 6, the control unit 40 controls each unit described below in an integrated manner. The storage unit 41 stores various data necessary for control processing by the control unit 40 and various data such as control parameters used for operation and calculation control. The display unit 42 is a display device such as a liquid crystal panel, and displays various notifications and warnings. This display item includes a display screen for instructing and displaying on the screen a portion requiring cleaning on the mask plate 12 that requires local cleaning.

  The image recognizing unit 43 performs recognition processing on image data captured by the substrate recognition camera 17a and the mask recognition camera 17b. The print inspection unit 44 recognizes the image data obtained by imaging the substrate 10 after screen printing by the substrate recognition camera 17a, so that the solder paste S is printed on the electrode 10a that is the printing target portion of the substrate 10 after printing. Perform the inspection. That is, by comparing the inspection quantities such as the area of the solder paste calculated by the image recognition unit 43 with the inspection threshold value, “blur” indicating that the print amount is too small at the print target portion, and the print amount is excessive. Items such as “smear” indicating that the solder is printed, and “position misalignment” where the solder is printed at a position deviated from the normal printing range are inspected. That is, the print inspection unit 44 performs a print inspection in which “blur”, which is an excessively small print amount in the print target portion, is included in the inspection items, and outputs a determination result based on a predetermined inspection threshold for these inspection items.

  The mask inspection unit 45 inspects the state of the pattern hole 12a in the mask plate 12 based on the determination result of the print inspection unit 44, and performs a process of specifying a cleaning required site that requires cleaning. That is, when it is determined by the mask inspection unit 45 that printing defects having a high degree due to the state of the pattern hole 12a, such as “smear” or “smudge”, are continuously generated in the same portion, first mask recognition is performed. The camera 17b is moved to the said site | part, and the lower surface of the mask plate 12 is imaged. Next, by causing the image recognition unit 43 to perform recognition processing of the imaging data, it is confirmed whether or not the site is a site requiring cleaning that requires local cleaning.

  Here, when it is confirmed that it is a site requiring cleaning, the site is locally cleaned by the suction cleaning unit 18B. That is, the suction cleaning unit 18B serves as a local cleaning unit that locally cleans a site requiring cleaning. If no local cleaning means is provided, manual cleaning by a machine operator is performed. That is, the display unit 42 displays and instructs the cleaning required site on the screen, and the machine operator cleans the cleaning required site using a work tool such as a suction tool in accordance with this instruction.

  The mechanism control unit 46 controls the operations of the screen printing mechanism 13 and the substrate positioning unit 1 based on programs and control parameters stored in the storage unit 41, and includes a wiping cleaning unit 18A and a suction cleaning unit 18B. The head moving means 48 constituted by the mask cleaning mechanism 47, the head X-axis table 19 and the head Y-axis moving mechanism 20 is controlled.

Next, a print inspection in the screen printing method performed by the screen printing apparatus and a mask cleaning operation executed based on the result of the print inspection will be described with reference to FIG. First, by imaging the substrate 10 after the screen printing by the board recognition camera 17a, the print state of the solder paste on the substrate 10, the printing inspection including the inspection item "blur" of the print amount in printing target site too small And a determination result based on a predetermined inspection threshold is output for the inspection item (print inspection step). In FIG. 7A, in this print inspection process, “slack” is generated in which the solder paste S is printed only on a part of the center of the printing range by the pattern hole 12a on some of the electrodes 10a. An example is shown in which it is output as a determination result that “bleeding” in which the solder paste S protrudes beyond the printing range is generated on the electrode 10a.

  Next, in response to the determination result, the state of the pattern hole 12a in the mask plate 12 is inspected based on the determination result to identify a cleaning required site that requires cleaning (mask inspection step). That is, as shown in FIG. 7B, the mask recognition camera 17b is moved to the portion of the mask plate 12 corresponding to the electrode position where the above-mentioned “blur” or “bleeding” is detected, and the portion is moved by the mask recognition camera 17b. The pattern hole 12 a is imaged, and then the image data is recognized by the image recognition unit 43. As a result, a clogged state in which the solder paste S adheres firmly in the pattern hole 12a occurs in the pattern hole 12a in which "fading" is detected, and the pattern lower surface of the mask around the pattern hole 12a in which "bleeding" occurs is formed. It is confirmed that the protruding solder paste S is still attached, and it is detected that both are sites requiring cleaning.

  Then, based on the confirmation result of the mask inspection process, a mask cleaning operation is performed. Here, first, as shown in FIG. 7D, the wiping cleaning unit 18A is moved to the vicinity of the pattern hole 12a where the “smudge” has occurred, and the wiping head 21 presses the cleaning paper 23 against the cleaning required site. The protruding solder paste S is wiped off by the cleaning paper 23. Next, as shown in FIG. 7 (e), the suction cleaning unit 18B is moved to the pattern hole 12a where "fading" has occurred, the suction head 38 is pressed from the lower surface side, and suction is performed from the suction hole 38b. The solder paste S firmly adhered in the pattern hole 12a is removed.

  As a result, a reliable cleaning effect can be obtained even for clogging in the pattern hole 12a, which has been difficult to remove by a mask cleaning operation mainly using conventional wiping. Instead of performing automatic mask cleaning by the suction cleaning unit 18B, the display unit 42 displays and instructs the cleaning required site on the screen, and the machine operator manually cleans the required cleaning site according to this display. Also good.

  As described above, in the screen printing shown in the present embodiment, regarding the print state of the paste on the printed substrate, the determination of the print inspection that includes “blur” in which the print amount at the print target portion is too small as the inspection item. Based on the result, the state of the pattern hole in the mask plate is inspected to identify the site requiring cleaning that requires cleaning. As a result, it is possible to effectively prevent printing failures that occur locally and continuously and to ensure printing quality.

  In this embodiment, an example of printing a solder paste as a paste has been shown. However, the application of the present invention is not limited to a solder paste, and a highly viscous fluid such as a conductive paste or a flux is screen-printed. Even in the case of printing, the present invention can be applied.

Screen printing how the present invention is locally continuously effectively prevent printing failure occurs, has the effect that it is possible to ensure print quality, the solder paste to the substrate through the pattern holes It can be used in the field of printing pastes.

1 is a front view of a screen printing apparatus according to an embodiment of the present invention. The side view of the screen printing apparatus of one embodiment of this invention The top view of the screen printing apparatus of one embodiment of this invention Structure explanatory drawing of the cleaning unit of the screen printing apparatus of one embodiment of the present invention Explanatory drawing of operation | movement of the cleaning unit of the screen printing apparatus of one embodiment of this invention The block diagram which shows the structure of the control system of the screen printing apparatus of one embodiment of this invention Explanatory drawing of the mask cleaning operation | movement in the screen printing method of one embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate positioning part 10 Board | substrate 10a Electrode 12 Mask plate 12a Pattern hole 13 Screen printing mechanism 16 Squeegee 17 Camera head unit 18A Wiping cleaning unit 18B Suction cleaning unit 21 Wiping head 38 Suction head S Solder paste

Claims (1)

A screen printing method for printing a paste on a substrate through the pattern hole by bringing the substrate into contact with a mask plate provided with a pattern hole, supplying a paste on the mask plate, and sliding a squeegee. ,
For the printed state of the paste on the printed circuit board, a print inspection is performed in which the inspection item includes “faint” in which the printing amount at the print target portion is too small, and a determination result based on a predetermined inspection threshold is output for the inspection item Based on the print inspection process and the determination result, when it is determined that a printing defect having a large degree due to the state of the pattern hole is continuously occurring in the same part, the lower surface of the mask plate is imaged. A mask inspection process for inspecting the state of the pattern hole in the mask plate by performing recognition processing of the imaged data and identifying a cleaning required site that needs to be cleaned,
A screen printing method characterized in that the cleaning required site is displayed on a screen and instructed, and the cleaning required site is manually cleaned by a machine operator according to the display.

Images