JPH07121576B2 - Positioning method and device for printing screen and substrate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and apparatus for aligning a printing screen and a board in a screen printing apparatus for printing a paste such as cream solder on the board.

(Summary of the Invention) The present invention relates to a method and apparatus for aligning a printing screen and a substrate in a screen printing apparatus for printing a paste such as cream solder on a substrate. By devising it, the corresponding alignment marks on the substrate side can be seen through for each substrate, and one image pickup means can be attached to the XY table to image multiple screen side alignment parts. In addition, the squeegee paste application operation on the printing screen is retractable so as not to interfere with the paste application operation, so that the screen and the substrate can be aligned at the actual printing position.

(Prior Art) A first conventional example will be described with reference to FIGS. 7 to 9. In these figures, the printing screen 1 is a sheet of stainless steel or the like, has a printing pattern (a pattern for screen printing formed by punching holes) and a half-etched portion 2, and the half-etched portion 2 has a colored resin. Three
The screen side mark 4 is formed by embedding (for example, black resin) as shown in FIG. The positional relationship between the print pattern and the half-etched portion 2 is accurately defined. The printing screen 1 is stretched and fixed to a screen frame 5, and the screen frame 5 is supported by a screen slide rail 6 so as to be movable in parallel. On the other hand, an alignment mark (fiducial mark) 11 is formed of copper foil or the like on the substrate 10 placed on the table. Here, the screen-side mark 4 is located at two corners of the screen 1, and similarly, the substrate-side alignment mark 11 is also located at two corners of the substrate 10. , The mutual intervals of the marks 11 are set to be equal to each other. The marks 4 and 11 are provided at two positions so that the shift in the rotational direction between the screen 1 and the substrate 10 can be detected and corrected.

In the case of the first conventional example, first, the screen 1
The mark 4 above is recognized by an image processing apparatus equipped with one TV camera as an image pickup means. That is, the TV camera moves and takes an image of the marks 4 respectively located at two corners of the screen 1, and the image processing device processes the image signal obtained by the imaging to recognize the position of the mark 4.

Since the alignment mark 11 on the substrate cannot be recognized as it is, the screen 1 is moved by the screen slide rail 6 to expose the substrate surface, and the alignment mark 11 on the substrate 10 is detected. The relative position between 4 and the substrate side alignment mark 11 is confirmed on the image processing apparatus side. If there is a deviation in the relative position, the substrate 10 or the screen 1 is moved and corrected to correct the relative positional relationship between the screen 1 and the substrate 10.

In the case of the alignment method according to the first conventional example, the following problems occur.

(1) In order for the TV camera to take images of the screen side mark 4 and the board side alignment mark 11, two movements have to be performed to grasp the respective positions, and there is a deviation in the positioning of the TV camera. Only the screen 1 and the substrate 10 are displaced from each other.

(2) After the image of the screen side mark 4 is taken, the screen frame 5 temporarily retracts the positioning mark 11 on the substrate for detection, and again moves to the actual printing position during printing. Deviation causes relative deviation with the alignment mark 11 on the substrate side.

Due to the existence of these problems (1) and (2), the actual position of the screen-side mark 4 and the in-substrate alignment mark 11 is not aligned even if the actual correction work is performed. Misalignment due to variations in mechanical accuracy directly affects printing accuracy. Further, since the screen frame 5 is largely moved, it takes a long time to recognize the screen and the substrate side mark and correct the position, which causes a problem that the takt time of the apparatus becomes long.

The second conventional example will be described with reference to FIGS. 10 and 11. In these figures, the printing screen 1 is formed with the printing pattern and the positioning holes 15 at the same time.
10 side alignment mark (fiducial mark)
The diameter of the hole 15 is larger than that of the alignment mark 11 so that the hole 11 can be detected through the alignment hole 15. Here again, the screen side holes 15 are located at the two corners of the screen 1, and similarly the alignment marks 11 on the substrate side are also located at the two corners of the substrate 10, so It is assumed that the space and the space between the marks 11 are set to be equal to each other.

In the case of the second conventional example, first, the screen 1 and the substrate 10 are overlapped at the actual printing position before the step of repeating the printing operation, and the screen side alignment is performed by the image processing apparatus including the two TV cameras 16. The position of the board side alignment mark 11 is recognized through the use hole 15 and the alignment mark 11
The deviation between the aiming point (center point of the mark) and the reference point (center point of the hole) of the positioning hole 15 is added to the XY-θ table (X, Y directions) on which the substrate 10 is positioned and placed. The table 17 which is movable also in the rotation direction in the horizontal plane is operated to correct the aiming point and the reference point so that they coincide with each other. As a result, the reference position of the XY-θ table 17 is determined.

After that, the TV camera 16 is moved in parallel to the substrate recognition position shown by the phantom line in FIG. 11, and the paste is spread with a squeegee on the substrate 10 on the left side in FIG. The operation will be performed. FIG. 11: The TV camera 16 at the board recognition position R of the virtual line picks up an image of the alignment mark 11 of the next board 10 on the XY-θ table 17 which is translated by the same distance as the TV camera, and an image is obtained. The processing apparatus compares the position of the first alignment mark 11 on the substrate 10 and operates the XY-θ table 17 to eliminate the displacement between the two, thereby performing the alignment operation.

(Problems to be Solved by the Invention) By the way, in the case of the second conventional example, the alignment mark 11 on the substrate side is passed through the alignment hole 15 on the screen side.
Is detected only for the first substrate received on the XY-θ table 17 before the screen printing process, and for the second and subsequent substrates, alignment is performed at a substrate recognition position R that is different from the actual printing position. Only the mark 11 for use is recognized. Therefore, if the screen 1 is displaced by some reason while the screen printing operation is being repeated, the displacement is directly the displacement of the printing position with respect to the substrate surface.

It should be noted that the alignment hole 15 on the screen side is provided for each substrate.
Detecting the alignment mark 11 on the substrate side through is impossible because the paste adheres to the alignment hole 15 on the screen side once the screen printing operation is performed.

A technique similar to the second conventional example is disclosed in JP-A-62-196776. This Japanese Patent Application Laid-Open No. 62-196776 also sees the recognition mark through the hole of the mask, and when applied to a screen printing apparatus, once the screen printing operation is performed, the paste still adheres to the hole of the mask. is there.

In view of the above points, the present invention devises the structure of the alignment portion of the printing screen, and provides the XY table with the image pickup means for picking up the image of the alignment portion, thereby aligning the screen and each substrate. And an apparatus for aligning a printing screen and a substrate, in which the printing operation can be executed as it is by accurately retracting the imaging means so as not to interfere with the screen printing operation. The purpose is to provide.

(Means for Solving the Problems) In order to achieve the above object, a method for aligning a printing screen and a substrate of the present invention is such that a half-etching portion is provided on the paste supply side surface of the printing screen and the half-etching is performed. A transparent member for covering the through hole is provided at the center of the screen portion, and a transparent member for covering the through hole is fixed to at least the half-etched section to form the screen side alignment section at a plurality of locations. Positioning marks corresponding to the holes are provided on the substrate side, and each of the through holes and the through holes in the state where the printing screen is superposed on the substrate by one image pickup means provided on the XY table. Each alignment mark is imaged through the lens, and the deviation between the reference point of the through hole and the aiming point of the alignment mark is detected from the image signal of the image pickup means. However, the relative positional relationship between the printing screen and the substrate is corrected so that the reference point of the through hole and the aiming point of the alignment mark match.

Further, in the alignment device for a printing screen and a substrate of the present invention, a half-etched portion is provided on the surface of the printing screen on the printing paste supply side, and a through-hole portion is provided in the central portion of the half-etched portion. A transparent member that covers the hole is fixed to at least the half-etched portion to form screen-side alignment portions at a plurality of locations, and alignment marks corresponding to the plurality of location alignment portions are provided on the substrate side. One image pickup means is provided in the XY table in which the position alignment portion of the location is included in the movement range and the retreat position other than the printing screen is also the movement range.

(Operation) In the present invention, the half-etching portion is provided on the paste supply side surface of the printing screen, the through-hole portion is provided in the central portion of the half-etching portion, and at least the transparent member that covers the through-hole portion is at least the half. Since a plurality of screen side alignment parts are fixed to the etching part, even if the paste adheres to or enters the boundary of the transparent member (outer edge of the half etching part) due to the screen printing operation, the through hole The contour of the part is not affected. For this reason, a substrate-side alignment mark is imaged by a single TV camera as an image capturing means through a plurality of through-holes in the screen-side alignment portion of each substrate, and an image signal obtained by this image capture is used for each screen-side aperture. The image processing device recognizes the deviation between the position and the board side alignment mark,
Positional deviation can be corrected.

Also, by providing one TV camera on the XY table, it is possible to capture images of multiple screen-side alignment parts and substrate-side alignment marks, and paste coating on the printing screen. When the squeegee for use moves, the TV camera can be set to the retracted position. Therefore, after aligning the printing screen and the substrate, the screen printing operation can be continued as it is.

(Embodiment) An embodiment of a printing screen / substrate alignment method and apparatus according to the present invention will be described below with reference to the drawings.

An embodiment of the present invention will be described with reference to FIGS. In these figures, X- is displayed on the base 40 of the screen printing device.
The Y-θ table 35 is installed, and the XY-θ table 35 is installed.
A substrate support plate 42 is mounted on the top of the substrate via an elevating part 41 so as to be vertically movable. Then, the substrate 10 is positioned and placed on the substrate support plate 42.

The screen frame 5 that supports the printing screen 1 made of stainless steel or the like is held on the side of the apparatus frame 43 that is erected on the base 40. The screen frame 5 shown in FIG. 2 is the actual printing position, and the right virtual line position is the standby (replacement) position. A squeegee 44 for applying a paste such as cream solder is supported above the printing screen 1 so as to be vertically movable and movable in the X direction. However, in both FIGS. 1 and 2, the substrate 10 and the squeegee 44 are in the lowered and raised positions (standby positions) before printing.

An XY table supported above by the device frame 43
One TV camera 25 as an image pickup means is attached to 45. The TV camera 25 is for picking up images of the alignment parts 20 provided at two corners of the printing screen 1 as shown in FIG.

The structure of each screen side alignment section 20 is shown in FIGS. 4 and 5. That is, the printing screen 1
Circular half-etched part 21 on the paste supply side of
Further, a circular through hole portion 22 having a diameter smaller than that of the half-etched portion 21 is concentrically formed in the central portion of the half-etched portion 21. Then, a transparent member 23 such as resin or glass is fixedly integrated with the half-etched portion 21 and the through hole portion 22 to form a screen side alignment portion 20.
Here, the transparent member 23 is provided because without the transparent member, the half-etched portion 21 and the through-hole portion 22 are filled with the paste by the screen printing operation, and the subsequent alignment operation becomes impossible. The half-etched portion 21 is provided around the through-hole portion 22 because the paste position is set to the circular contour of the through-hole portion 22 even if the paste adheres to or enters the boundary between the transparent member 23 and the screen upper surface during screen printing. This is so that the correct contour of the through-hole portion 22 is always maintained even if the screen printing is repeated, without applying it. Of course, the positional relationship between the print pattern formed on the screen 1 and the through holes 22 is accurately defined.

On the upper surface of the substrate 10, circular alignment marks (fiducial marks) 11 corresponding to the screen-side alignment portions 20 are formed of copper foil or the like.

As described above, the TV camera 25, which is supported by the XY table 45 so as to be movable in the X and Y directions, is arranged above the screen 1, and the TV camera 25 has the image processing structure shown in FIG. It serves as an image pickup means for inputting an image in the device 30. A ring illuminator 26 is provided on the TV camera 25 side to illuminate the screen 1 and the board-side alignment mark 11. The illumination range W of the ring illuminator 26 is set to be a sufficiently larger area than the screen side alignment section 20.

As shown in FIG. 3, the screen side alignment section
20 is located at the two corners of the screen 1, but similarly the alignment mark 11 on the device board side is also located at the two corners of the substrate 10, and the circular through-holes 22 of each alignment part 20. It is assumed that the mutual spacing of the circular marks 11 and the mutual spacing of the circular marks 11 are set to be equal.

As shown in FIG. 6, the image processing device 30 is a unit that moves in the X-Y directions to capture images in the visual field including the two screen-side alignment portions 20 and the substrate-side alignment marks 11. Of the TV camera 25, an image signal processing unit 31 for binarizing an image signal (luminance signal representing brightness) from the TV camera, an image memory 32 for storing the image information after the binarization, and an image. The substrate 10 recognizes the deviation between the reference points (for example, the center points) of the circular through holes 22 provided at two locations and the aiming points (for example, the center points) of the circular positioning marks 11 based on the image information of the memory 32. The correction amount (ΔX, ΔY, Δθ) of the positioning-mounted XY-θ table 35 is calculated to obtain XY-
and a calculation control unit 33 that corrects and drives the θ table.

Next, the alignment operation in the case of this embodiment will be described. However, it is assumed that the printing screen 1 is fixed and the substrate 10 is placed on the XY-θ table 35 so that the position can be corrected.

First, the substrate 10 is raised via the elevating part 41 to be superposed on the screen 1, and the substrate side alignment mark 11 is optically overlapped with the circular through hole 22 of the screen side alignment part 20 on the substrate. Set to be transparent. And
Both the circular through hole 22 and the circular alignment mark 11 are displayed on the TV.
Images are captured by the camera 25. This image capture is executed for the two alignment units 20 by moving the TV camera 25 via the XY table 45. Note that the positional relationship between the two alignment units 20 is known, and the amount of movement of the XY table 45 is also known.

The image seen from above the screen side alignment section 20 is the fifth
As shown in the figure, the circular alignment mark 11 such as a copper foil is a bright portion a, the substrate surface seen through the circular through hole portion 22 is a dark portion b, and the outside thereof is a bright portion c on the screen 1 made of stainless steel or the like. Therefore, the TV camera 25 can capture the circular contour of the circular alignment mark 11 and the circular contour of the circular through-hole portion 22, and the center point of the circular through-hole portion 22 and the central point of the circular alignment mark 11 can be obtained. Deviation can be recognized on the side of the image processing apparatus 30, and the XY-θ table 35 is operated by using the correction amount (ΔX, ΔY, Δθ) of the XY-θ table based on the recognition result to make a circular through hole. The center point of the portion 22 and the center point of the alignment mark 11 are aligned.

The TV camera 25 has moved to the retreat position U, which is out of the upper position of the screen 1 as shown in FIG. As described above, the center point of the circular through hole portion 22 on the screen side and the center point of the alignment mark 11 on the substrate side are aligned with each other, and the squeegee 44 is moved to the screen while keeping the alignment state of the substrate 10 and the screen 1. 1 and moves in the X direction by being pressed against this and performing a screen printing operation of spreading a required paste.

The distance P between the lower end of the TV camera 25 and the upper surface of the screen is, for example, about 80 mm, whereas the distance Q between the half-etched portion 21 in which the through hole 22 is formed and the upper surface of the substrate is 0.4 mm or less. Distance Q from the depth of field of the TV camera optical system
Is minute, and the through-hole part does not change the focal length on the TV camera side.
It is clear that images of 22 and the alignment mark 11 can be captured.

The above alignment operation is repeatedly performed every time the substrate is sequentially placed on the XY-θ table, and the screen printing operation is always performed in the alignment state.

In the above embodiment, the transparent member 23 may be fitted and fixed to at least the half-etched portion 21 so as to cover the through hole portion 22, and may not be fitted inside the through hole portion 22.

Further, the screen-side through hole and the substrate-side mark may have a shape other than a circle, for example, a square or the like.

(Effects of the Invention) As described above, according to the present invention, the following effects can be obtained.

(1) By attaching one image pickup means to an XY table and detecting a plurality of alignment portions on the printing screen side and substrate-side alignment marks that can be seen through from the alignment portions, the substrate and the printing screen are separated. Can be accurately aligned, and the accuracy of the XY table is not related to the alignment accuracy. Moreover, the image pickup means can be prevented from interfering with the squeegee operation for screen printing by moving to a retracted position off the screen, and after the alignment, the screen printing operation can be performed without moving the substrate and the screen at all. Can be continued and the print position deviation can be minimized.

(2) The tact time of the screen printing apparatus can be shortened as compared with the case where the screen is moved to recognize the substrate side mark position as in the above-mentioned first conventional example.

(3) Not only at the start of printing with a new screen, but also with respect to each board, the screen side alignment portion and the board side alignment mark can be image-recognized for accurate alignment, and repeated printing operations can be performed. Even if the screen is displaced, this displacement can be corrected.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of a method and apparatus for aligning a printing screen and a substrate according to the present invention, FIG. 2 is a side view of the same, and FIG. 3 is an alignment portion on the printing screen in the embodiment. FIG. 4 is a front sectional view of the main part of the embodiment, FIG. 5 is a perspective view of the screen side alignment portion viewed from the TV camera side in the embodiment, and FIG. 6 is used in the embodiment. FIG. 7 is a block diagram showing an example of an image processing apparatus, FIG. 7 is a plan view showing a first conventional example, FIG. 8 is a front view showing the same, and FIG. 9 (A) is a screen side mark used in the first conventional example. FIG. 10 is a sectional view showing the same, FIG. 10B is a sectional view showing the second conventional example, and FIG. 11 is an operation explanatory view of the second conventional example. 1 ... Printing screen, 10 ... Substrate, 11 ... Positioning mark, 20 ... Positioning part, 21 ... Half etching part, 22 ... Through hole part, 23 ... Transparent member, 25 ... TV camera, 26 ... illuminator, 30 ... image processing device, 35 ... XY
-Θ table, 44 ... Squeegee, 45 ... XY table.

Claims (3)

[Claims] 1. A half-etching portion is provided on a surface of a printing screen where a paste is supplied, a through-hole portion is provided inside the half-etching portion, and a transparent member for covering the through-hole portion is fixed to at least the half-etching portion. Then, the screen side alignment section is formed at a plurality of locations, and the alignment marks corresponding to the through holes of the plurality of location alignment sections are provided on the substrate side, and one image is provided on the XY table. Means for picking up images of the through holes and the alignment marks through the through holes in a state where the printing screen is overlaid on the substrate by means of the image signal of the image pickup means and the reference point of the through holes. Detecting a deviation between the aiming point of the alignment mark and correcting the relative positional relationship between the printing screen and the substrate to align the reference point of the through hole with the alignment point. Printing screen and method of aligning a substrate, characterized in that to match the aiming point of the mark. 2. The method for aligning a printing screen and a substrate according to claim 1, wherein the image pickup means retracts from the printing screen during a period in which the paste applying squeegee moves on the printing screen. 3. A means for correcting the relative positional relationship between the printing screen and the substrate is provided, a half etching portion is provided on the surface of the printing screen on the side of the printing paste supply, and a through hole is provided inside the half etching portion. And a transparent member covering the through hole is fixed to at least the half-etched portion to form screen-side alignment portions at a plurality of locations, and alignment marks corresponding to the plurality of location alignment portions are provided on the substrate. One image pickup means is provided on the XY table which is provided on the side of the XY table and which includes the plurality of alignment portions in the movement range and also the retreat position other than the printing screen. Alignment device for printing screen and substrate.