KR20020071107A - Vision apparatus for screen printer and vision inspecting method using therewith - Google Patents

Abstract

PURPOSE: A vision apparatus for screen printer and vision inspection method using the same is provided to effectively inspect the state of cream solder deposited at the PCB, while automatically washing the screen in accordance with the state of the screen. CONSTITUTION: A vision apparatus comprises a CCD camera(11) having an optical axis which is set in a horizontal direction; a hollow block(12) installed at the front surface of the CCD camera, and which has an open top and an open bottom; a first prism(25) installed within the hollow block, and which reflects, in the direction opposite to the CCD camera, the image introduced from the top of the block, and reflects, toward the camera, the image introduced from the bottom of the block; a mirror(28) arranged at the first prism, and which reflects the light reflected by the first prism, toward the CCD camera through the first prism; and a first illumination unit installed on the first prism and a second illumination unit installed underneath the first prism. The second illumination unit includes a first illuminator(21), a second prism(26) for reflecting the light generated from the first illuminator down to the block, and a third illuminator(23) arranged underneath the hollow block.

Description

Vision apparatus for screen printer and vision inspection method using therewith

The present invention relates to a vision inspection apparatus for a screen printer and an inspection method using the same, and more particularly, a vision apparatus capable of performing two-dimensional vision inspection while simultaneously aligning a screen and a printed circuit board in a screen printer, and using the same It is about a test method.

In general, a screen printer is a device for applying a cream solder to a printed circuit board, by applying a cream solder to the printed circuit board in a state in which a screen having a predetermined pattern of holes is in close contact with the printed circuit board. It is an apparatus which prints a cream solder on a predetermined shape on it. In general, a printed circuit board matches a pattern of a printed circuit board and a screen in a screen printer device in a mutually aligned state, and when a predetermined cream solder application is completed and discharged out of the screen printer, the solder is applied correctly on the printed circuit board. We will work to check whether or not. In addition, the screen printer operates the screen cleaning device to clean the bottom of the screen as the cream solder remains on the screen in the process of repeatedly applying the cream solder. Usually, this may be done automatically or repeatedly by visual inspection by an operator depending on the number and time of solder application.

In addition, according to the prior art, the equipment for inspecting the normality of the solder coating is usually used a vision inspection device, and the inspection is generally performed by placing the device downstream of the screen printer. In other words, the printed circuit board after the application of the cream solder in the screen printer is moved to the vision device through the conveyor, and it is checked whether the cream solder is correctly applied in the vision device. The operation of the screen printton with a separate vision device is as follows.

When the printed circuit board is introduced into the screen printer, the reference position mark on the printed circuit board and the reference position mark on the screen are respectively recognized to align the printed circuit board and the screen. When the printed circuit board and the screen are aligned with each other, the printed circuit board on the conveyor rises and sticks to the screen, and then cream solder is applied. After that, the printed circuit board is lowered and the substrate is discharged. The discharged substrate is introduced into the vision apparatus to perform a predetermined vision inspection. That is, it is checked whether the cream solder is correctly applied.

The vision device of the screen printer as described above is composed of a device for performing a cream solder application operation and a device for performing a vision inspection. In addition, although the inspection apparatus is driven by the same control device as the screen printer, there is a disadvantage that the configuration of the apparatus is enlarged and complicated. In order to overcome this disadvantage, a vision device may be incorporated into a screen printer. However, in such an example, a controller for controlling the vision device may be separately configured, and a driving unit for driving the vision device may be complicated, resulting in expensive equipment. have.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an improved screen printer vision apparatus for performing two-dimensional vision inspection.

Another object of the present invention is to provide a vision apparatus in which a quick vision inspection operation can be performed.

It is another object of the present invention to provide a vision device capable of performing alignment of a screen and a printed circuit board in a screen printer and inspecting the state of the screen and the application of the cream solder on the printed circuit board.

Another object of the present invention to provide a screen automatic cleaning method according to the state of the screen.

Another object of the present invention is to provide a vision inspection method of a screen printer.

1 is a schematic front view of a vision inspection apparatus of a screen printer according to the present invention.

2A and 2B are a plan view and a side view of FIG. 1.

Figure 3 is a flow chart showing a cream solder application procedure using the vision inspection device of the screen printer according to the present invention.

4A to 4E are schematic views illustrating a phenomenon that may occur when cream solder is applied on a printed circuit board.

5A and 5B are schematic diagrams illustrating a phenomenon that may occur when cream solder remains on a screen.

<Brief Description of Major Codes in Drawings>

11. Camera 12. Block

13. Lighting installation 14. Hollow part

21. First lighting unit 22. Second lighting unit

23. 3rd lighting unit 24. 4th lighting unit

In order to achieve the above object, in accordance with the present invention, the optical camera is set in the horizontal direction; A hollow block installed at the front of the CD camera and having an upper portion and a lower portion opened; Is installed inside the hollow block, the first prism for reflecting the image flowing from the top of the block in the opposite direction of the CD camera, the image flowing from the bottom of the block toward the camera and ; A mirror installed at one side of the first prism and reflecting light reflected by the first prism toward the CD camera through the first prism and first lighting means installed at an upper portion of the first prism; Provided is a vision device for a screen printer having a; second lighting means installed under the first prism.

According to one feature of the invention, the first lighting unit disposed on the lower side of the first prism on one side of the inside of the hollow block; A second prism installed under the vertical portion of the first prism so as to reflect light of the first lighting portion to the lower portion of the block; It is further provided with a third lighting means for illuminating in the lateral direction and located below the hollow block.

According to another feature of the invention, the third lighting means is a lighting installation unit installed in the lower portion of the block; A second lighting unit is arranged in the lighting installation unit in a multi-layered manner as a circle toward an illumination object.

According to another feature of the invention, the second lighting means further includes a third lighting unit which is installed under the block and is installed between the first lighting unit and the second lighting unit.

In addition, according to the present invention, the step of obtaining the reference data for the center position and area of the cream solder by imaging and binarizing the printed circuit board on which the application of the cream solder was normally performed; Obtaining comparative data on the center position and area of the actual cream solder by imaging and binarizing the printed circuit board on which the actual cream solder application was performed; And comparing the reference data and the comparison data with each other to determine whether the cream solder is normally applied. The vision inspection method of the screen printer is provided.

According to another feature of the invention, if the area of the cream solder forming the comparison data is larger or smaller than the area forming the reference data, it is determined that the cream solder is excessive or insufficient.

In addition, according to another feature of the present invention, if the center position of the cream solder forming the comparison data is spaced apart from the center position forming the reference data, it is determined that the cream solder is released.

According to another feature of the present invention, an edge is arbitrarily set on the outside of the portion where the application of the cream solder is normally performed, and if the cream solder forming the comparison data infringes the edge, it is determined as a short circuit of the cream solder.

According to the present invention, further comprising the steps of: imaging the screen; Obtaining reference data for the position and area of the aperture of the screen by binarizing the scratched image; Imaging the screen after binarizing the solder solder application to obtain a comparison data for the center position and area of the cream solder remaining on the fraud screen; And comparing the reference data and the comparison data with each other to determine whether the cream solder remains on the screen.

Hereinafter, with reference to an embodiment shown in the accompanying drawings the present invention will be described in more detail.

1 is a schematic front view of a vision device of a screen printer according to an exemplary embodiment of the present invention, and FIGS. 2A and 2B are plan and side views of FIG. 1.

Referring to Fig. 1, the CCD camera 11 is arranged so that the optical axis is set in the horizontal direction. The hollow block 12 is fixed to the front of the CCD camera 11. The inside of the block 12 is formed in a hollow shape, whereby the top and the bottom are opened. A first prism 25 is installed at a portion corresponding to the center of the hollow portion 14 formed in the block 12, and a mirror 28 is installed at one side of the first prism 25. The mirror 28 is adjustable through the mirror adjusting unit 27. The mirror adjusting part includes a fastening part for fixing the adjusting part to the hollow block and adjusting means for finely adjusting the angle of the mirror part. For example, the fastening part is a fastening screw labeled 29a in Fig. 2b, and the adjusting means is an adjusting screw labeled 29b in Fig. 2b. This is a means for matching each image coming from the top and bottom at the time of manufacturing the vision device to the same optical axis in one camera. The first prism 25 and the mirror may transfer an image of the object placed on the upper portion of the block 12 by mutual cooperation to the CCD camera 11. That is, the image of the object disposed above the block 12 is reflected by the first prism 12 at an angle of 90 degrees to the mirror 28, and is reflected by the mirror 28 again to reflect the first prism 12. ) Will be facing the camera (11). Typically the object placed on top of block 12 is a screen in a screen printer.

The first lighting unit 21 is installed above the hollow part of the block 12. In the first lighting unit 21, a plurality of light emitting diodes are preferably arranged in a circular shape. The first lighting unit 21 is used to illuminate an object disposed above the block 12. The illumination by the first lighting unit 21 is evenly spread on the object by the diffusion plate 28 provided thereon.

On the other hand, the second prism 26 is installed in the hollow portion of the block 12 at the vertical lower portion of the first prism 25. In addition, a second lighting unit 60 is installed at one side of the second prism 26. Illumination by the second illumination unit 60 is for vertically illuminating the object and is reflected downward by the second prism 26, thereby illuminating the object disposed below the block 12. Therefore, the second lighting unit 60 is intensively disposed at the portion where the reflection of the illumination light through the second prism 26 is maximized, and is installed in a multi-layer in the vertical direction on the side of the camera 11 as shown in the drawing. It is desirable to be. In another example, it may be arranged on the opposite side of the camera 11, in which case the desired purpose can be achieved by setting the reflection direction of the second prism 26 differently.

The lower part of the block 12 is provided with an illumination installation portion 13 as a horizontal illumination means for illuminating the object, that is, the side of the applied cream solder. The lighting installation unit 13 has a shape of a dome as shown in the drawing, and a third lighting unit 23 is installed inside the lighting installation unit 13. In addition, a fourth lighting unit 24 for illuminating an intermediate portion of the vertical illumination and the horizontal illumination is provided. In general, when the vision device scratches each image to align the screen and the printed circuit board, all of the second, third, and fourth lighting units do not need to operate, and only one operation may be performed. Do. The second, third and fourth lighting units are provided with three-stage illumination to perform a two-dimensional inspection of the state of the applied cream solder. The third lighting unit 23 is a light emitting diode, and as shown in the drawing, it is preferable to form a multilayer in a vertical direction and be installed in a circular shape on a plane. In addition, the fourth lighting unit 24 is a light emitting diode, and is installed near the center of the block 12 as shown in the figure.

The object disposed below the block 12 is typically a printed circuit board. The image of the printed circuit board passes through the second prism 26 installed in the hollow portion 14 of the block, and may be reflected by the first prism 25 to face the camera 11.

The vision device of the screen printer having the above configuration is installed so as to be inserted between the screen disposed above and the printed circuit board disposed below the screen printer. As is known, in a screen printer, the screen is supported by a screen fixing device capable of rotation and plane coordinate movement, and the printed circuit board can be lifted up and down by the conveyor by reaching the vertical lower portion of the screen fixing device. The vision device according to the present invention is installed to be inserted or detached between the screen fixing device and the lifting device of the printed circuit board.

Hereinafter, the operation of the vision device according to the present invention will be schematically described with reference to FIG. 3 in relation to the overall operation of the screen printer.

With the screen secured by the screen fixing device, when the printed circuit board reaches the vertical lower portion of the screen by the conveyor (step 31), the vision device may display the screen and the printed circuit to mutually align the screen and the printed circuit board. Reference marks on the substrate are sequentially recognized (step 32). In order to recognize the reference mark of the screen, the illumination of the first illumination unit 21 is activated and the illumination of the second to fourth illumination units 22, 23, 24 is not activated. In this case, the reference mark image of the screen disposed on the upper portion of the block 12 is perpendicularly reflected by the first prism 25, reflected by the mirror 28, and passed through the first prism 25. It is picked up by the camera 11. On the other hand, in order to recognize the reference mark of the printed circuit board, the illumination of the second to fourth illumination unit 22, 23, 24 is operated without the illumination of the first illumination unit 21. The illumination of the second illumination unit 22 illuminates the lower printed circuit board by the orthogonal reflection by the second prism 26, and the illumination of the third and fourth illumination units 23, 24 is directly the printed circuit. The substrate is illuminated. The reference mark image of the printed circuit board disposed under the block 12 with the aid of the illumination passes through the second prism 26 and is reflected by the first prism 25 so that the imaging by the camera 11 is performed. It becomes possible.

After recognition of the reference mark ends, mutual alignment is performed (step 33). Alignment is typically done by rotating or planar motion of the screen. That is, the screen fixing device rotates or plane moves the screen. After alignment (or even before alignment) the vision device must be withdrawn between the printed circuit board and the screen (step 34). The withdrawal of this vision device is intended to prevent interference between the printed circuit board and the screen in the future.

When the alignment is finished, the printed circuit board is raised, thereby bringing the screen and the printed circuit board into close contact with each other (step 35). Next, application of the cream solder is performed (step 36), and the printed circuit board is lowered again (step 37). After the printed circuit board is lowered, the vision device is inserted again between the printed circuit board and the screen (step 38).

The vision apparatus images the bottom surface of the screen where the application of the cream solder is finished and the top surface of the printed circuit board (step 39). At this time, the imaging operation for the upper screen and the lower printed circuit board can be performed in the same manner as in imaging the above reference mark (step 32).

In imaging of the surfaces, if the cream solder remains on the bottom surface of the screen, it must be post-processed to perform the desired cleaning process. This cleaning process must be performed separately from the regular cleaning, which avoids the negative effects of residual cream solder on the subsequent application process. This does not perform automatic screen cleaning according to the number of application of the cream solder or the time of operation, but the cleaning is performed according to the actual screen state, thereby reducing the unnecessary cleaning step. In addition, when the cream solder coating state on the printed circuit board is poor, the printed circuit board is treated as defective. The printed circuit board treated as defective is discharged unlike the normal path through a separate transfer mechanism. Typically, the substrate that is determined to be defective is discharged by another path from a conveyor installed downstream of the screen printer. That is, when the defective substrate arrives at the conveyor installed on the downstream side of the screen printer, the conveyor lowers the conveyor by 90 degrees by the lifting means and rotates 90 degrees to discharge the substrate. The conveyor again reverses and rises to wait for the next inflow of the printed circuit board. And when it is determined that the application state of the cream solder is determined to be normal, it is discharged to the normal path and moved to the next processing step (step 40).

Next, a method of inspecting the application state of the cream solder on the surface of the printed circuit board will be described.

4A to 4D are diagrams illustrating a phenomenon that may occur when cream solder is applied to a surface of a printed circuit board.

4A shows a cream solder application state in a steady state. That is, imaging is performed by setting the inspection area 41 using the vision device as described above, where the area and the position of the pad 43 where the cream solder is applied, the area of the actual cream solder 42 and , The position is a match.

4B shows that the area of the cream solder 42 is smaller than the area of the pad 43. This is a lack of cream solder. 4C shows that the area of the cream solder 42 is larger than the area of the pad 43. This is an excess of cream solder. 4D is a case where the cream solder 42 is pushed to one side to invade the boundary portion of the pad 43. 4E shows a state in which a short circuit occurs due to the formation of the connection part 45 between the neighboring cream solders 42.

Various types of cream solder application conditions on the printed circuit board as described above are determined through the following process. First, so-called binarization is performed by imaging a printed circuit board on which a normal cream solder is applied with a vision device. Binarization simplifies the image of the printed circuit board surface by dualizing it with and without cream solder. That is, when the portion to which the cream solder is applied is shown in white, the other portion is expressed in black.

Next, the center position and area of the cream solder coated portion are calculated and set based on such data. The center position and area data of this reference become a criterion for judgment in the subsequent actual imaging operation, and this data is input in advance to the control unit. In addition, in FIG. 4A, a predetermined area is arbitrarily set outside the inspection area 41, and data for the same is also input. The data related to this outer portion serves as a criterion for determining a short circuit as shown in Fig. 4E.

The cream solder on the printed circuit board applied during the actual screen printing operation is processed through the process of imaging and binarization as described above to obtain data on its area and center, and the data is stored in the reference data. Are compared. That is, if the area of the actually applied cream solder is smaller or larger than the reference area, it is determined that the cream solder is insufficient or excessive as shown in Figs. 4B and 4C. On the other hand, if the center of the cream solder actually applied is out of the reference center is a departure state of the cream solder as shown in Figure 4d. In addition, as mentioned above, when the cream solder is invaded to the edge set arbitrarily on the outer side of the inspection area 41, it is determined as a short circuit as shown in FIG. 4E.

5A and 5B schematically illustrate a phenomenon that may occur due to residual cream solder on the bottom surface of the screen.

Referring to FIG. 5A, this shows a state where the cream solder 53 is spread around the through hole 52 formed on the screen 51. In this state, the through hole 52 is maintained in the open state, but a lot of cream solder 53 is spread on the surface of the screen 51 around the through hole 52.

Referring to FIG. 5B, this shows a state where the cream solder 53 directly blocks the through hole 52 formed on the screen 51. Since the cream solder 53 is blocking the through hole 52, if the cleaning is not performed, the normal cream solder may not be applied in a subsequent process.

The cream solder state on the screen as described above is determined through the following process. First, so-called binarization is performed by imaging with a vision device a screen on which no cream solder is attached. For example, through the binarization, the through hole 52 of the screen appears in black, and the screen surface that does not appear in white. The area and position of the binarized through hole 52 are input to the controller as reference data.

After the actual cream solder coating operation is completed, the screen surface is imaged and binarized. At this time, the portion of the cream solder is separated and binarized. For example, the part of cream solder is shown in black, the remainder is shown in white, and the area and position data are calculated | required.

Next, by comparing the reference data for the screen through and the comparative data for the cream solder with each other, it can be determined whether the cream solder is blocking the screen through as shown in FIG. 5B. In addition, if the cream solder has violated the edge of the screen aperture outside the controller input arbitrarily set, it can be determined as the bleeding state of the cream solder as shown in Fig. 5A.

The vision apparatus of the screen printer and the inspection method using the same according to the present invention can be easily installed in the screen printer to effectively inspect the screen and the function of the screen and the printed circuit board and the condition of the cream solder on the printed circuit board. There is an advantage that it can. In addition, by performing the screen inspection and screen cleaning according to the state there is an effect of preventing unnecessary screen cleaning work.

Although the present invention has been described with reference to one embodiment shown in the accompanying drawings, this is merely exemplary, and those skilled in the art may various modifications and other equivalent embodiments therefrom. You will understand. Therefore, the true scope of the invention should be defined only by the appended claims.

Claims (9)

A CD camera whose optical axis is set in a horizontal direction; A hollow block installed at the front of the CD camera and having an upper portion and a lower portion opened; Is installed inside the hollow block, the first prism for reflecting the image flowing from the top of the block in the opposite direction of the CD camera, the image flowing from the bottom of the block toward the camera and ; A mirror installed at one side of the first prism and reflecting light reflected by the first prism toward the CD camera through the first prism and first lighting means installed at an upper portion of the first prism; And a second lighting means installed under the first prism. The method of claim 1, wherein the second lighting means, A first lighting unit disposed below the first prism at one side of the hollow block; A second prism installed under the vertical portion of the first prism so as to reflect light of the first lighting portion to the lower portion of the block; And a third lighting unit positioned below the hollow block and configured to laterally illuminate the hollow block. The method of claim 2, The second lighting means is a lighting installation unit installed in the lower portion of the block; And a second lighting unit arranged in multiple layers as a circle toward the lighting object in the lighting installation unit. The method of claim 2, The second lighting unit is a vision device of the screen printer, characterized in that it further comprises a third lighting unit which is installed in the lower portion of the block and is installed between the first lighting unit and the second lighting unit. Obtaining reference data on the center position and area of the cream solder by imaging and binarizing the printed circuit board on which the cream solder application is normally performed; Obtaining comparative data on the center position and area of the actual cream solder by imaging and binarizing the printed circuit board on which the actual cream solder application was performed; And, Comparing the reference data and the comparison data with each other to determine whether or not the normal application of the cream solder; Vision inspection method of a screen printer comprising a. The method of claim 5, And if the area of the cream solder forming the comparison data is larger or smaller than the area forming the reference data, it is determined that the cream solder is excessive or insufficient. The method of claim 5, And if the center position of the cream solder forming the comparison data is spaced apart from the center position forming the reference data, determining that the cream solder is detached. The method of claim 5, And an edge is arbitrarily set on the outside of the portion where the application of the cream solder is normally applied, and when the cream solder forming the comparison data infringes the edge, a short circuit of the cream solder is determined. Imaging the screen; Obtaining reference data for the position and area of the aperture of the screen by binarizing the scratched image; Imaging the screen after binarizing the solder solder application to obtain a comparison data for the center position and area of the cream solder remaining on the fraud screen; And, And comparing the reference data with the comparison data to determine whether the cream solder remains on the screen.