JPH07110549B2 - Positioning method and structure for printing screen and substrate - Google Patents

Description

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

(Summary of the Invention) The present invention relates to a method and structure for aligning a printing screen and a substrate in a screen printing apparatus for printing a paste such as cream solder on a substrate, in which the screen side alignment portion is the center of the half-etched portion. Through holes are formed in the portions and transparent members are arranged in those portions, and the alignment mark on the substrate side can be seen through the through holes, and the boundary of the transparent members. Even if the paste adheres to the portion, it does not fall on the outline of the through hole portion, and the alignment between the printing screen and the substrate can always be performed with high accuracy.

(Prior Art) A first conventional example will be described with reference to FIGS. 4 to 6. 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 constructed 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, at the actual printing position, the mark 4 on the screen 1 is recognized by the image processing device having one image pickup device (TV camera). That is, the image pickup device (TV camera) moves and picks up images of the marks 4 respectively located at the two corners of the screen 1, and the image signal obtained by the image pickup is processed by the image processing device to determine the position of the marks 4. recognize.

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) The image pickup device (TV camera) has a mark 4 on the screen side.
In order to image the two of the substrate and the board-side alignment mark 11, the positions must be grasped by moving the screen twice, and the screen 1 and the board 10 are displaced by the amount of misalignment of the positioning of the imaging device (TV camera). The position of shifts.

(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. The positional deviation due to the variation in the opportunity accuracy directly affects the 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. 7 and 8. 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 is processed by the image processing apparatus including the two image pickup devices (TV cameras) 16. The position of the substrate side alignment mark 11 is recognized through the side alignment hole 15, and the aiming point (mark center point) of the alignment mark 11 and the reference point of the alignment hole 15 (hole center point The reference point and the reference point are operated by operating an XY-θ table (a table that is movable not only in the X and Y directions but also in the rotational direction in the horizontal plane) 17 on which the substrate 10 is positioned and mounted. Correct so that and match. As a result, the reference position of the XY-θ table 17 is determined.

After that, the image pickup device (TV camera) 16 is moved in parallel to the board recognition position shown by the virtual line in FIG. 8, and the paste is applied with a squeegee to the board 10 on the left side in FIG. The screen printing operation is performed by expanding the screen. FIG. 8: The image pickup device (TV camera) 16 at the substrate recognition position R of the virtual line aligns the next substrate 10 on the XY-θ table 17 which has been translated by the same distance as the image pickup device (TV camera). The image for the marking mark 11 is picked up and compared with the position of the first positioning mark 11 on the substrate 10 by the image processing device, and the XY-θ table is eliminated so that there is no deviation between them.
Operate 17 to perform 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 makes it possible to accurately perform the alignment between the screen and each substrate at the actual printing position by devising the structure of the alignment portion of the printing screen, and perform the printing operation as it is. It is an object of the present invention to provide a method and a structure for aligning a printing screen and a substrate capable of executing the above.

(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 through hole is provided in the central portion of the portion, and a transparent member is arranged in the half-etched portion and the through hole to form a screen side alignment portion, and the through hole is formed with the printing screen stacked on the substrate. The alignment mark on the substrate side is detected through a portion, and the reference point of the through hole and the aiming point of the alignment mark are matched.

Further, the alignment structure of the printing screen and the substrate of the present invention, the alignment mark is provided on the substrate, a half etching portion is provided on the paste supply side surface of the printing screen, and the center portion of the half etching portion is provided. A screen side alignment portion is formed by providing a through hole portion and disposing a transparent member in the half etching portion and the through hole portion.

(Operation) In the present invention, a half etching portion is provided on the paste supply side surface of the printing screen, a through hole portion is provided in the central portion of the half etching portion, and a transparent member is provided in the half etching portion and the through hole portion. Since they are arranged to form the screen side alignment part, even if the paste adheres to or enters the boundary of the transparent member (outer edge of the half-etched part) due to the screen printing operation, the contour of the through hole part has no effect. I do not receive it. Therefore, for each board, the board-side alignment mark is imaged by the image pickup device (TV camera) through the through-hole of the screen-side alignment section, and the screen-side through-hole and board-side alignment for the image signal from this imaging The deviation from the mark can be recognized by the image processing device, and the deviation can be corrected. Then, printing can be continued while maintaining the alignment of the substrate and the screen.

(Embodiment) An embodiment of a method for aligning a printing screen and a substrate and a structure 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, a circular half-etched portion 21 is formed on the surface of the printing screen 1 made of stainless steel or the like on the paste supply side, and a circular through-hole portion 22 having a diameter smaller than that of the half-etched portion 21 is formed. Are formed concentrically in the central part of the. 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 paste by the screen printing operation, and the subsequent alignment operation becomes impossible. Half etching part 21 through hole
What was provided around 22 is that screen printing is performed so that the paste position does not reach the circular contour of the through hole 22 even if the paste adheres or enters the boundary between the transparent member 23 and the screen upper surface during screen printing. This is because the accurate contour of the through hole portion 22 is always maintained even if repeated.

A circular alignment mark (fiducial mark) 11 is formed on the upper surface of the substrate 10 with copper foil or the like.

An image pickup device (TV camera: CCD camera or the like) 25 included in the image processing device 30 having the configuration shown in FIG. 3 is arranged above the screen 1, and the screen 1 is arranged on the substrate side alignment mark 11
A ring illuminator 26 is provided to illuminate the. The irradiation range W of the ring illuminator 26 is set to be a sufficiently larger area than the screen side alignment section 20.

Although illustration is omitted, the screen-side alignment section 20 is located at two corners of the screen 1, and the board-side alignment marks 11 are also located at two corners of the board 10. It is assumed that the mutual intervals of the circular through holes 22 of the alignment section 20 and the mutual intervals of the circular marks 11 are set to be equal to each other.

As shown in FIG. 3, the image processing device 30 includes an image pickup device (TV camera) 25 for picking up an image in the visual field including the screen side alignment portion 20 and the board side alignment mark 11, and an image pickup device (TV camera). 2 more image signals (luminance signals representing light and dark)
The image signal processing unit 31 for performing the binarization process, the image memory 32 for storing the image information after binarization process, and the reference points of the circular through-holes 22 provided at two locations based on the image information in the image memory 32 (for example, Correction amount (ΔX, ΔY, Δθ) of the XY-θ table 35 on which the substrate 10 is positioned and mounted by recognizing the deviation between the center point) and the aiming point (for example, the center point) of the circular positioning mark 11 Calculation unit for calculating and correcting the XY-θ table
It has 33 and.

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 circular through hole portion 22 of the alignment portion 20 on the screen side in which the substrate-side alignment mark 11 is overlapped on the substrate in advance.
To be optically transparent. Then, both the circular through hole portion 22 and the circular positioning mark 11 are picked up by an image pickup device (TV camera) 25 to capture an image.

The image seen from above the screen side alignment section 20 is the second
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 imaging device (TV camera) 25 can capture the circular contour of the circular alignment mark 11 and the circular contour of the circular through hole 22, and the center point of the circular through hole 22 and the circular alignment mark 11 can be taken. Can be recognized on the image processing device 30 side, and the XY-θ table 35 is operated using the correction amount (ΔX, ΔY, Δθ) of the XY-θ table based on the recognition result. And the center point of the circular through hole portion 22 and the center point of the alignment mark 11 are aligned. Then, the screen printing operation is performed while maintaining this state.

The distance P between the lower end of the image pickup device (TV camera) 25 and the upper surface of the screen is, for example, about 80 mm, whereas the through hole 22
The distance Q between the half-etched portion 21 where the mark is formed and the upper surface of the substrate is 0.4 mm or less, and the distance Q is minute compared to the depth of field of the camera optical system, and the through hole can be formed without changing the focal length on the camera side. It is obvious that the image of the part 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.

During screen printing, the imaging device (TV camera) 25 is moved to the retracted position so as not to hinder the movement of the squeegee spreading the paste on the screen. 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) After accurately aligning the substrate and the printing screen, the screen printing operation can be performed without moving the both, and the printing position shift 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 when printing is started by a new screen, but also the screen side alignment portion and the substrate side alignment mark can be image-recognized for each substrate to perform accurate alignment. Even if the screen is displaced, this displacement can be corrected.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a method and structure for aligning a printing screen and a substrate according to the present invention, and FIG. 2 is a perspective view of a screen-side alignment portion viewed from the camera side in the embodiment, and FIG. FIG. 4 is a block diagram showing an example of an image processing apparatus used in the embodiment, FIG. 4 is a plan view showing a first conventional example,
5 is a front view of the same, FIG. 6 (A) is a plan view showing a screen side mark used in the first conventional example, FIG. 6 (B) is the same sectional view, and FIG. 7 shows a second conventional example. A sectional view and FIG. 8 are operation explanatory views 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 ... Imaging device (TV camera), 26 illuminator, 30 Image processing device, 35
…… XY-θ table.

Claims (2)

[Claims] 1. A half-etched portion is provided on a surface of a printing screen on which a paste is supplied, a through-hole portion is provided in a central portion of the half-etched portion, and a transparent member is arranged in the half-etched portion and the through-hole portion. The alignment mark on the substrate side is detected through the through hole portion in a state where the screen side alignment portion is formed and the printing screen is superposed on the substrate, and the reference point of the through hole portion and the alignment mark are used. A method for aligning a printing screen and a substrate, wherein the aiming point of the mark is matched. 2. An alignment mark is provided on a substrate, a half-etching portion is provided on a surface of a printing screen on a side where a printing paste is supplied, and a through hole portion is provided at a central portion of the half-etching portion. A structure for aligning a printing screen and a substrate, wherein a transparent member is disposed on the portion and the through hole to form a screen side alignment portion.