JP2003237031A - Alignment device for screen printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alignment device for screen printing capable of accurately aligning a substrate plate and a screen at a high speed. <P>SOLUTION: The alignment apparatus is constituted so as to align the substrate plate 3 and the screen 4 for applying screen printing to the substrate plate 3 by utilizing the alignment marks 34 and 35 of both of them and provided with a projection part 6 for projecting a laser beam 5 on the predetermined region containing the alignment mark 35 of the screen 4, an image pickup part 11 for picking up the image of the predetermined region obtained by the reflection of the laser beam 5, a drive device 20 for driving at least either one of the substrate plate 3 and the screen 4 and a control unit 13 for controlling the operation of the drive device 20 so as to align the respective alignment marks 34 and 35 of the substrate plate 3 and the screen 4 on the basis of the signal from the image pickup part 11. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alignment device for screen printing.

[0002]

2. Description of the Related Art In a screen printing method, an alignment mark provided on a screen mask is aligned with a position of an alignment mark provided on a surface of a substrate as an object to be printed so as not to cause misalignment of printing overlap. Need to be adjusted with high precision.

Conventionally, such alignment has been performed manually. The operator compares the alignment marks provided on the substrate and the screen mask with a magnifying glass of about 25 times, judges the presence or absence of the deviation, and performs the alignment. Therefore, the finish quality of printing depends on the skill of the worker.

As another method, an alignment device using a CCD camera is known. With this device,
The alignment mark is imaged by moving the CCD camera. Image processing is performed on the imaged alignment mark to identify the center of gravity of the alignment mark. The displacement between the center of gravity of the alignment mark provided on the base and the center of gravity of the alignment mark provided on the screen mask is specified, and alignment is performed.

Although not a positioning method, a method using a photoelectric sensor or a laser photoelectric switch is known as a method for detecting the position of a product flowing through a line. For example, a photoelectric sensor detects the passage or reflection of light and determines only the presence or absence of an object. This confirms the passage of the product flowing in the line. Further, in the laser type photoelectric switch, by detecting a slight change in the reflection of the laser, the presence or absence of the meandering of the sheet is determined, the etching line on the transparent glass is counted, and the joint between thin sheet materials is specified.

[0006]

In recent years, with the improvement of pigments and the like, high-definition screen printing using a screen has been attempted. Specifically, the conventional resolution of 150 to 20
100 μm resolution for 0 μm (line and space)
Screen printing of less than μm has been attempted.

However, the use of the above-mentioned alignment method causes various inconveniences. For example, the manual work described above has a problem in accuracy because it depends on the skill of the worker. In the method using the CCD camera, it takes time to move the camera, perform image processing, and the like. In particular, the screen is made of gauze, and the printing surface is a transparent portion and is transparent, while the printing ink impermeable surface has a peculiarity that the density of the silk thread is high and it is opaque. Therefore, there is a limit to the accuracy of the image captured by the CCD camera, and in order to improve the accuracy, it is necessary to narrow the field of view of the CCD camera and move it over a wide range, or to perform high-precision image processing. It takes a long time to align. Further, the position detection method using a photoelectric sensor or a laser photoelectric switch does not have a configuration that can be used for alignment.

Therefore, it is an object of the present invention to provide an alignment apparatus capable of accurately aligning a substrate and a screen at high speed.

[0009]

The alignment apparatus of the present invention will be described below. In addition, in order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are added in parentheses, but the present invention is not limited to the illustrated forms.

In the alignment apparatus (1) of the present invention, an object to be printed (3) and a screen (4) for screen printing on the object to be printed are provided on the object to be printed and the screen, respectively. Alignment mark (34,
35) is an alignment device for aligning each other using a projection unit (6, 12) for projecting a laser beam (5) on a predetermined region of the screen including the alignment mark (35), and the laser beam. An image pickup section (11) for picking up an image of the predetermined area obtained by reflection of the image and outputting a signal corresponding to the obtained image;
A drive unit (20) for driving at least one of the object to be printed and the screen, and the driving unit (20) so that the respective alignment marks of the object to be printed and the screen match based on a signal from the imaging unit. The above-mentioned problem is solved by including a control means for controlling the operation of the means.

According to the alignment apparatus of the present invention, the deviation of the alignment mark is specified based on the image obtained by the reflection of the laser beam. The laser beam has a strong directivity, and its output and beam diameter can be easily adjusted. Therefore, while projecting a laser beam with a beam diameter corresponding to the size of the mesh of the screen, the image obtained by the reflection of the laser beam is used to reflect the reflectance of the material to be printed, the reflectance of the wire and resin forming the screen, and the alignment mark. By performing the analysis based on the difference in the reflectance of the, the alignment can be performed with high accuracy.

In the alignment apparatus of the present invention, the projection unit includes a light source (6) for generating a laser beam,
Optical system for scanning laser beam from the light source (12)
And the imaging unit is provided with a camera (11) installed toward the predetermined region, and the laser beam is scanned by the optical system, so that the camera obtains by reflection of the laser beam. An image of the predetermined area may be captured.

In this case, since the image of the area including the alignment mark is picked up by scanning the laser beam,
High-speed alignment is possible without the need to move the camera. The optical system is a polygon mirror, F
A θ lens, a lens array, a galvanometer mirror, a multi-laser laser, or the like may be used, or these may be combined.

The alignment apparatus of the present invention comprises means (16) for storing information on the initial position of the drive means relating to the alignment between the printing medium and the screen, and the control means means for the information on the initial position. Drive the driving means based on the
After that, the drive means is driven based on the signal from the image pickup section to align the printing medium and the screen with the second precision higher than the first precision. May be. The screen has an opaque portion, and unless the entire alignment mark on the substrate is hidden by the opaque portion of the screen and an image cannot be captured, the amount of deviation and the direction of the deviation cannot be specified. Therefore, by driving the driving means in advance based on the information of the initial position to roughly align the printing medium and the screen to such an extent that the alignment marks of both are at least partially overlapped, the entire alignment mark of the substrate is screened. Avoid the state of being hidden by the impermeable part of. After this,
It is possible to perform the alignment with high accuracy by specifying the displacement amount and the displacement direction of the alignment mark based on the signal from the imaging unit and driving the driving unit. With such coarse positioning, since the area containing the alignment mark is limited to some extent at the stage of projecting the laser beam, it is possible to narrow the range of projecting the laser beam on the screen and perform high-speed alignment. You can

In the alignment apparatus of the present invention, the beam diameter of the laser beam from the light source may be set smaller than the mesh of the screen. In this case, by discriminating between the laser beam reflected by the wire and the laser beam reflected by passing through the mesh, it is possible to identify the deviation of the alignment mark with an accuracy equal to or smaller than the size of the mesh, and The accuracy can be increased.

[0016]

1 is a diagram showing the overall configuration of an alignment apparatus 1 according to an embodiment of the present invention. As shown in this figure, the alignment apparatus 1 includes a fixed base 2. A substrate 3 as an object to be printed is arranged above the fixed base 2, and a screen 4 is arranged above the substrate 3 so as to maintain a predetermined distance from the substrate 3. In order to align the substrate 3 and the screen 4 with the alignment device 1,
A drive device 20 for moving at least one of the substrate 3 and the screen 4, for example, the substrate 3, is provided.
The driving device 20 drives the substrate 3 in two axial directions that are parallel to the surface of the screen 4 and are orthogonal to each other, and a rotational axis direction around an axis line that is orthogonal to the surface of the screen 4 to drive the substrate 3.
And the screen 4 can be positioned. Such a driving device 20 can use various known configurations such as a combination of an XY stage and a rotary table. The driving device 20 may be replaced by the substrate 3 or the substrate 3
In addition to this, the screen 4 may be driven for positioning.

The alignment apparatus 1 includes a laser 6 as a light source for generating a laser beam 5, a reflecting mirror 7 for reflecting the laser beam 5 from the laser 6 in a predetermined direction, and a driving source for driving the reflecting mirror 7. As a motor 8
A collimating lens 9 for converting the laser beam 5 from the reflecting mirror 7 into parallel light; a reflecting mirror 10 for reflecting the laser beam 5 from the collimating lens 9 toward the screen 4; And a CCD camera 11 that receives the reflected laser beam 5 and outputs a video signal. Reflecting mirror 7 and collimating lens 9
And the reflecting mirror 10 are schematic illustrations of an optical system, and hereinafter, these may be collectively referred to as an optical system 12.

The alignment apparatus 1 has a CPU 13 composed of a microprocessor. The CPU 13 has
A ROM 14 in which a program for controlling basic operations such as a start-up process of the alignment apparatus 1 is recorded, a RAM 15 for providing a work area for the CPU 13, and various programs and data necessary for executing alignment in the alignment apparatus 1. The external storage device 16 in which is recorded, the laser drive device 17 for driving the laser, the motor drive device 18 for driving the motor 8, and the image processing for converting the video signal from the CCD camera 11 into image data. The unit 19 is connected. The laser driving device 17 is C
Based on the instruction from the PU 13, the laser driving device 17 is driven to generate the laser beam 5 having a predetermined output for a predetermined time. The motor driving device 18 controls the rotation of the motor 8 to drive the reflecting mirror 7 based on an instruction from the CPU 13. Thereby, the laser beam 5 from the laser 6 can be scanned at a predetermined speed toward a predetermined range of the screen 4 via the optical system 12. The image processing unit 19
The image data generated based on the video signal from the CCD camera 11 is output to the CPU 13. The CPU 13 identifies the deviation between the alignment mark provided on the substrate 3 and the alignment mark provided on the screen 4 based on the image data. The misalignment of alignment marks
It is specified as a deviation in the two axis directions parallel to the surface of the screen 4 and orthogonal to each other, and a deviation in the rotation axis direction about an axis line orthogonal to the surface of the screen 4. That is, the direction of displacement specified here coincides with the driving direction of the substrate 3 by the driving device 20. Then, the control amount of each axis of the drive device 20 is determined in accordance with the identified deviation amounts in the three directions.

2A and 2B are enlarged views showing a region of the screen 4 onto which the laser beam 5 is projected. FIG. 2A is a top view and FIG. 2B is a side view. Screen 4
It has a net 31 in which the wire 30 is woven as warp and weft, and a film 32 made of a photosensitive resin or the like. The wire rod 30 is
For example, it is formed of fibers such as silk or metal such as stainless steel. The density of the net 31 is, for example, a wire diameter of 40 μm and a distance between wire rods in the same direction of 25 μm. Membrane 32
Forms a non-printing area that does not allow ink to pass through the screen 4, and the printing area is formed by providing a void portion in the film 32. Therefore, the print pattern formed by the film 32 is printed on the substrate 3 by passing the ink through the mesh 33 of the mesh 31 in the print area.

An alignment mark 34 is provided on the substrate 3. The alignment mark 34 is provided, for example, by printing a predetermined shape such as a diamond shape on the substrate 3.
Further, the size of the alignment mark 34 is, for example, the entire width is 5 if it is the wire diameter and the interval between the wire materials described above.
The size is mm. The alignment mark 35 is provided on the screen 4 by forming a void portion having the same shape as the alignment mark 34 in the film 32. For this reason, the substrate 3 is provided from above the screen 4 through the mesh 33.
The laser beam 5 can be projected on the alignment mark 34. The alignment marks 34 and 35 are provided so as to accurately overlap each other when the substrate 3 and the screen 4 are aligned at a predetermined position. Therefore, the laser beam 5 having a smaller beam diameter than the mesh 33 is projected from above the screen 4, and the image obtained by the reflected laser beam 5 is based on the difference in the reflectance of the wire 30, the film 32, the substrate 3, and the alignment mark 34. It is possible to perform the alignment by performing the analysis and specifying the deviation between the alignment marks 34 and 35. Here, it is desirable to select the material of the alignment mark 34 so that the reflectance of the alignment mark 34 is higher than the reflectance of the substrate 3. The alignment mark 34 may be formed by providing the substrate 3 with a recess.

FIG. 3 is a flow chart showing the procedure of the alignment process executed by the CPU 13. When the substrate 3 is loaded between the fixed base 2 and the screen 4, the CPU 13 executes the processing shown in FIG. In this process, the CPU 13
The drive device 2 drives the movable part (not shown) of the drive device 20 to a predetermined initial position based on the information related to the initial position of the drive device 20 recorded in the external storage device 16.
0 (step S1). Assuming that the screen 4 is set at the correct design position with respect to the fixed base 2 and the substrate 3 is accurately set at the design position with respect to the drive unit 20, the initial position is set to the respective initial position. It is set as a drive position of the substrate 3 when the alignment marks 34 and 35 are correctly overlapped. Actually, since there is an error in the mounting position of the screen 4 and the carrying-in position of the substrate 3 into the drive device 20, it is rare that the alignment marks 34 and 35 are correctly overlapped by simply driving the drive device 20 to this initial position. However, if the error is within an appropriate range, the alignment mark 34,
The screen 4 and the substrate 3 are aligned with such an accuracy (first accuracy) that at least a part of 35 is overlapped.

In step S2, the laser driving device 17 is instructed to start the generation of the laser beam 5 having a predetermined output from the laser 6. In step S3, the reflecting mirror 7
The motor drive device 18 is instructed to drive the motor 8 which is the drive source of the laser beam to scan the laser beam 5. The range in which the laser beam 5 is scanned is a predetermined range including the alignment mark 35, and this range is set based on the alignment accuracy in step S1. As the positioning accuracy in step S1 is increased, the range in which the laser beam 5 is scanned can be reduced, and the positioning speed can be increased. Furthermore, since the field of view of the CCD camera 11 can be narrowed, the alignment marks 34 and 35 can be imaged with high accuracy. In step S4, it is determined whether or not the scanning is completed, and if it is completed, the image data from the image processing unit 19 is subjected to image processing such as edge enhancement processing, contrast enhancement processing, and binarization processing (step S5). ). As a result, the alignment marks 34, 35 are reduced while reducing the data amount of the image data.
The accuracy of deviation detection can be improved. When the edge enhancement processing is performed, the alignment marks 34, 3
By detecting a part of the image of No. 5, it becomes possible to easily process at high speed. In step S6, the amount of misalignment of the alignment marks 34 and 35 in the three-axis directions described above is specified based on the image-processed data. Since the alignment marks 34 and 35 are rhomboids having anisotropy, it is possible to specify all the deviation amounts and directions in the triaxial directions from the relationship between the sides of the rhombus. Further, due to the deformation of the areas and shapes of the alignment mark 34 and the alignment mark 35, the amount of deviation in the axial direction orthogonal to the surface of the screen 4 and the amount of deviation in the rotational axis direction about the axis parallel to the surface of the screen 4 are used. May be specified. In step S7, a drive instruction is given to the drive device 20 based on the specified displacement amount to execute the alignment. The positioning accuracy at this time is higher than that in step S1 (second accuracy).

In the above embodiment, the diamond-shaped alignment marks 34 and 35 are exemplified, but the alignment marks may have any shape as long as the CPU 13 can specify the deviation amount based on the image captured by the CCD camera 11. For example, an alignment mark composed of straight lines or curved lines such as a cross shape may be used. The alignment mark may have a polygonal shape other than a rhombus, a circular shape, a regular shape, or an irregular shape. Further, the present invention is not limited to the example in which the deviation amount is specified based on only one pair of alignment marks, and the deviation amount may be specified by using two or more pairs of alignment marks.

In the present embodiment, the CPU 13 executes the program stored in the external storage device 16 so that
Although it functions as control means for controlling the driving means, the control means may be realized by a hardware circuit in which logic circuits are combined. The image processing in step S5 is performed by the CPU.
The image processing dedicated circuit different from the circuit 13 may be used. For example, the image processing unit 19 may execute the image processing of step S5.

In the present embodiment, the movable part of the drive device 20 is driven to a predetermined position based on the information related to the initial position of the drive device 20 which is recorded in the external storage device 16 in advance (step S1 in FIG. 3). Although the alignment device has been exemplified, the information related to the initial position may be appropriately set and updated. Another embodiment for appropriately setting and updating the information related to the initial position will be described below.

As shown in FIG. 4, an alignment apparatus 1 according to another embodiment is provided on a fixed base 2 and is capable of abutting the substrate 3 with pins 50, 50, the pins 50, 50 and an alignment mark 35. And a CCD camera 51 capable of imaging 35. In addition, the alignment apparatus 1 of FIG. 4 includes a transfer device for loading and unloading the substrate 3 with respect to the fixed base 2, and a screen drive device for moving the screen 4 with respect to the substrate 3. Illustration thereof is omitted. The other components of the alignment device such as the drive device 20 for moving the substrate 3 are
It is similar to the alignment apparatus 1 shown in FIG. In addition to the CCD camera 11, the image processing unit 19 includes a CCD camera 51.
To drive.

FIG. 5 is a CP of the alignment apparatus 1 of FIG.
It is a flowchart which shows the procedure of the alignment process which U13 performs. In this process, the CPU 13 instructs the carrying device (not shown) to carry in the substrate 3 until the substrate 3 abuts the pins 50, 50 (step S20).
Next, information related to the initial position of the screen 4 is stored in the RAM.
It is determined whether it is set to 15 (step S2
1). If it is determined that the data is not held, the CCD 51
Is driven to instruct the image processing unit 19 to capture the reference position (for example, the position of the pin 50) on the fixed base 2 and the alignment mark 34, and based on the image data from the image processing unit 19. Pin 50 and alignment mark 3
The distances with respect to 4 in the x direction and the y direction are specified (step S22).

Next, the screen driving device is instructed to dispose the screen 4 at a predetermined position above the substrate 3 (step S23). In step S24, the CCD 51
Is driven to instruct the image processing unit 19 to image the pin 50 and the alignment mark 35, and based on the image data from the image processing unit 19, the pin 50 and the alignment mark 35 with respect to the x direction and the y direction. Specify each distance. In step S25, the distance between the pin 50 and the alignment mark 34 in the x direction and the y direction, and the distance between the pin 50 and the alignment mark 35 in the x direction and the y direction.
Based on the distance in the direction, the alignment mark 3
The amount of deviation between 4 and the alignment mark 35 is specified. Next, the shift amount is set in the RAM 15 as information relating to the initial position of the screen 4. When it is determined in step S21 that the information related to the initial position is set, steps S22 to S26 are skipped.

In step S27, the screen driving device is instructed to move the screen 4 by the displacement amount set in the RAM 15. This step is substantially equal to step S1 in FIG. 3, and corresponds to the process of aligning the screen 4 and the substrate 3 with the so-called first precision.

Next, as in steps S2 to S6 of FIG. 3, the laser driving device 17 is driven and the image processing section 19 is driven to specify the amount of deviation between the alignment marks 34 and 35 (step S28). In step S29, it is determined whether or not the shift amount exceeds a predetermined reference level, for example, whether or not the alignment marks 34, 35 are shifted so that the alignment mark 34 of the substrate 3 cannot be observed through the alignment mark 35 of the screen 4. To judge. If it is determined that the difference is within the reference level, the process for alignment is executed based on the shift amount (step S3).
0). Step S30 corresponds to the process of step 7 of FIG. When it is determined in step S29 that the reference level is exceeded, the initial position information in the RAM 15 is reset (step S31), and then the process returns to step S21 to acquire the information related to the initial position again. Step S3
After the alignment of 0 is completed, the printing process is performed, and then the process of FIG. 5 is restarted from the time when the next substrate 3 is loaded.

As described above, by properly setting and updating the information relating to the initial position, it is possible to perform the initial position alignment within an appropriate error range even when the screen is stretched. Although the screen 4 is aligned with the substrate 3 as a reference in the above example, the substrate 3 may be aligned with the screen 4 as a reference. An absolute reference position is defined separately from the substrate 3 and the screen 4 (for example, the position of the pin 50), and the alignment marks 34 and 35 of the substrate 3 and the screen 4 are positioned at predetermined positions with respect to the reference position. The substrate 3 and the screen 4 may be aligned by driving the substrate 3 and the screen 4 as described above.

[0032]

As described above, according to the alignment apparatus of the present invention, the deviation of the alignment mark is specified based on the image obtained by the reflection of the laser beam. The laser beam has a strong directivity, and its output and beam diameter can be easily adjusted. Therefore, while projecting a laser beam with a beam diameter corresponding to the size of the mesh of the screen, the image obtained by the reflection of the laser beam is used to reflect the reflectance of the material to be printed, the reflectance of the wire and resin forming the screen, and the alignment mark. By performing the analysis based on the difference in the reflectance of the, the alignment can be performed with high accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of an alignment apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged view showing a region of a screen onto which a laser beam is projected.

3 is a flowchart showing a procedure of alignment processing executed by a CPU of the alignment apparatus shown in FIG.

FIG. 4 is a diagram showing another embodiment of the alignment apparatus.

FIG. 5 is a flowchart showing the procedure of another alignment process.

[Explanation of symbols]

1 Alignment device 3 Substrate (printed material) 4 screen 5 laser beam 6 laser 11 CCD camera 12 Optical system 16 External storage means 20 Drive

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2C035 AA01 FB02 FB11 FB16 FB23                       FB36 FB41                 2C250 EB25 EB26                 2F065 AA01 AA07 AA14 AA20 BB02                       DD03 DD06 FF04 FF23 GG04                       HH13 JJ03 JJ08 JJ26 LL12                       LL15 MM16 PP12 QQ04 QQ31                       QQ32 TT08

Claims (4)

[Claims] 1. An alignment apparatus for aligning a printing medium and a screen for screen printing on the printing medium with each other using alignment marks provided on the printing medium and the screen, respectively. A projection unit that projects a laser beam onto a predetermined region of the screen including the alignment mark, and an image of the predetermined region obtained by reflection of the laser beam, and outputs a signal corresponding to the obtained image. An image capturing unit, a driving unit that drives at least one of the print target and the screen, and the alignment marks of the print target and the screen match each other based on a signal from the image capturing unit. An alignment apparatus comprising: a control unit that controls the operation of the drive unit. 2. The projection unit is provided with a light source for generating a laser beam, and an optical system for scanning the laser beam from the light source, and the imaging unit has a camera installed toward the predetermined region. The alignment device according to claim 1, wherein the camera captures an image of the predetermined region obtained by reflection of the laser beam by scanning the laser beam by the optical system. 3. A means for storing information on an initial position of said driving means relating to alignment between said printing medium and said screen, said control means driving said driving means based on the information on said initial position. Then, the printing medium and the screen are aligned with a first accuracy, and then the driving means is driven based on a signal from the imaging unit to move the printing medium and the screen to the first precision. The alignment is performed with a second accuracy higher than the accuracy of 1.
The alignment device described in. 4. The alignment apparatus according to claim 1, wherein a beam diameter of the laser beam on the screen is set to be smaller than a mesh of the screen.