JPH1058649A - Recognizing method for solder paste and screen printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for recognizing solder paste for constituting a solder paste inspecting unit of a low cost by accurately recognizing the paste. SOLUTION: The method for recognizing solder paste printed on a board distinctly from other element on the board comprises the steps of imaging the board by a camera while emitting a light to the board to obtain a planar image of the board, edge extracting the image to obtain an edge information image, and executing the image by expanding and contracting to solidly coat a solder paste region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recognizing a solder paste for soldering an electronic component to a substrate, and a screen printing machine equipped with a solder paste inspection device employing the method.

[0002]

2. Description of the Related Art Various solder paste recognition methods have been proposed for inspecting the area and position of a solder paste screen-printed on a substrate. As an example, there are a method using a difference in luminance and a method using a slit light by a laser (light cutting method). In the former recognition method, the board is imaged with a camera while irradiating the board with light, and the solder paste and elements other than the solder paste are identified from the obtained image by changes in luminance information. The method is to irradiate a slit light by a laser from directly above the substrate, image the substrate with a camera from an oblique position, and recognize the solder paste by using the fact that the slit light appears to be bent by the thickness of the solder paste It is something to do.

[0003]

Among the conventional solder paste recognition methods described above, in the former method, there are cases where the color of the substrate material is various and the difference between the luminance of the substrate material and the luminance of the solder paste is small. However, in this case, it is difficult to accurately distinguish the solder paste from the substrate. In addition, a solder leveler may be applied to the copper foil of the board so that the solder can be easily applied.However, since the solder leveler is a molten solder, it has the same silver color as the solder paste. And solder paste are very difficult to distinguish. In addition, the latter method requires a special illuminating device to irradiate slit light, and has a problem that an inspection device is expensive.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to accurately recognize a solder paste and to configure a solder paste inspection apparatus at a low cost. It is to provide a method.

Another object of the present invention is to provide a screen printer equipped with an accurate and inexpensive solder paste inspection device.

Another object of the present invention is to provide a screen printer capable of obtaining a printed circuit board having a high-quality solder paste with little printing deviation or chipping.

[0007]

According to one aspect of the present invention, there is provided a method for recognizing a solder paste printed on a substrate by distinguishing it from other elements on the substrate. A step of obtaining a planar image of the substrate by imaging the substrate with a camera while irradiating the substrate with light; a step of performing an edge extraction process on the planar image to obtain an edge information image; Applying an expansion process and a compression process to the image to paint out the solder paste area.

According to a second aspect of the present invention, there is provided a substrate supporting table, an illuminating device disposed above the substrate supporting table and irradiating light to a substrate mounted on the substrate supporting table, and the substrate supporting table. A camera arranged above the table and imaging the board, and a planar image of the board obtained by imaging the board with the camera while irradiating light to the board after screen printing by the illumination device. An image processing means for performing an edge extraction process, performing an expansion process and a compression process on the obtained edge information image to fill a solder paste area, and determining whether the area and position of the solder paste area filled by the image processing means are good or bad. A screen printing machine comprising:

According to a third aspect of the present invention, in the second aspect of the present invention, the substrate is periodically imaged by the camera while irradiating the substrate after screen printing with light by the illumination device, The obtained planar image of the board is processed by the image processing means, and the quality and the area of the solder paste area of the board are determined by the determination means.

According to a fourth aspect of the present invention, there is provided a first moving mechanism for moving in the direction of the X-axis extending in the horizontal direction, a second moving mechanism for moving in the direction of the Z-axis extending in the vertical direction, and in the horizontal plane. A substrate support table having a rotation mechanism for rotating the substrate support table, an illumination device arranged above the substrate support table and irradiating light to a substrate placed on the substrate support table, and an illumination device above the substrate support table. Screen supporting means having a moving mechanism for moving in the direction of the Y axis extending in the horizontal direction, and disposed between the substrate supporting table and the screen supporting means, and in the directions of the X axis and the Y axis. A first imaging means which is movable and has a camera for imaging the substrate, and is arranged above the screen supporting means and is movable in the X-axis and Y-axis directions and is supported by the screen supporting means; A second image pickup unit having a camera for picking up an image of the screen, and before performing the screen printing on the substrate, the first image pickup unit picks up the image of the substrate to recognize the position of the substrate. The position of the screen by recognizing the position of the screen, calculating a displacement between the substrate and the screen from the obtained position information of the substrate and the screen, and a first moving mechanism of the substrate support table. And a control mechanism for driving the moving mechanism of the screen support means to correct the displacement, and a first or second imaging of the substrate while irradiating the substrate after screen printing with light by the illumination device. Means for performing edge extraction processing on the planar image of the substrate obtained by imaging by the means, and performing expansion processing and compression processing on the obtained edge information image. Image processing means for filling the solder paste region of the substrate Te, is characterized in that it comprises a determining means for determining the quality of the area and position of the solder paste region filled by the image processing means.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, when the determining means determines that the position of the solder paste area is not present, (1) A moving mechanism, a rotating mechanism, and a moving mechanism of the screen supporting means are driven to correct a positional shift between the substrate and the screen.

According to a sixth aspect of the present invention, in the fourth or fifth aspect of the present invention, the substrate is periodically irradiated with light by the illuminating device while the substrate after the screen printing is irradiated with the light. Imaging by the first or second imaging means,
The obtained planar image of the board is processed by the image processing means, and the quality and the area of the solder paste area of the board are determined by the determination means.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a front view of a main part of a screen printing machine equipped with a solder paste inspection device adopting the solder paste recognition method of the present invention, FIG. 2 is a view taken along line AA of FIG. 1, and FIG. 4 is a block diagram of a solder paste inspection device mounted on the screen printing machine of FIG.

As shown in FIG. 1, the screen printing machine includes a substrate support table 2 installed on a base 1, a screen support means 3 disposed above the substrate support table 2, and a substrate support table. A first imaging unit 4 arranged between the screen supporting unit 2 and the screen supporting unit 3 for imaging the substrate P placed on the substrate supporting table 2;
A second imaging unit 5 that is arranged above the screen and captures an image of the screen S supported by the screen supporting unit 3;
, A supply conveyor 7 for supplying the substrate P onto the substrate support table 1, a discharge conveyor 8 for discharging the substrate P from the substrate support table 1,
A display device 9 (see FIG. 3) for visually observing images captured by the imaging unit 4 and the second imaging unit 5, and an inspection device (see FIG. 4) for inspecting the area and position of the solder paste printed on the substrate P ) And a control means 10 for controlling the substrate support table 2, the screen support means 3, the first imaging means 4, the second imaging means 5, the print head 6, the supply conveyor 7, the discharge conveyor 8, the display 9, and the inspection device (FIG. 4).

The substrate support table 2 is provided with a first moving mechanism 11 for moving in the direction of the X-axis extending in the horizontal direction (the left-right direction in FIG. 1), and is provided on the first moving mechanism 11 so as to be positioned in a horizontal plane. A rotating mechanism 12 for rotating, a second moving mechanism 13 provided on the rotating mechanism 12 for moving in a Z-axis direction extending in a vertical direction, and a second moving mechanism 13
It includes a substrate support plate 14 provided thereon, and a transport mechanism (not shown) provided on the upper surface of the substrate support plate 14 and transporting the substrate P in the X-axis direction. The substrate P
Are provided with two position recognition marks (not shown).

The screen support means 3 is provided with a screen support frame 15 for supporting the lower surface of the peripheral portion of the screen S, and a screen presser disposed above the screen support frame 15 for pressing the peripheral portion of the screen S against the screen support frame 15. A cylinder 16 and a moving mechanism 17 for moving in the Y-axis direction (see FIG. 2) extending in the horizontal direction are provided. It should be noted that two position recognition marks (not shown) are provided on the upper surface of the screen S.

The first imaging means 4 includes a camera 18 and a moving mechanism 19 for moving the camera 18 in the X-axis direction and the Y-axis direction.
And an illumination device 20 (see FIG. 4) for irradiating the substrate P with light. Further, the second imaging means 5 includes a camera 21
And a moving mechanism 22 for moving the camera 21 in the X-axis direction
And a lighting device (not shown) for irradiating the substrate P with light. The camera 21 is supported by a moving mechanism 24 (described later) of the print head 6 movably in the Y-axis direction.

The print head 6 includes a squeegee 23 for applying a printing paste provided at a lower portion, a moving mechanism 24 for moving in the Y-axis direction, and a vertical moving mechanism 25 for moving the squeegee 23 in the Z-axis direction. And

The supply conveyor 7 moves the substrate support table 2 in the X-axis direction so that the substrate support table 2 is moved.
When the supply conveyor 7 is driven in this state, the transport mechanism of the substrate support table 2 is interlocked.

The discharge conveyor 8 moves the substrate support table 2 in the X-axis direction so that the substrate support table 2 is moved.
When the discharge conveyor 8 is driven in this state, the transport mechanism of the substrate support table 2 is interlocked.

As shown in FIG. 4, the solder paste inspection apparatus includes an image processing means 26 and a discriminating means 27. The image processing means 26 and the discriminating means 27 include a CPU, a RAM,
It is constituted by a microcomputer including a ROM. The image processing means 26 controls the substrate P after screen printing.
The substrate P is placed in the first position while irradiating light to the
A planar image of the substrate P obtained by imaging with the camera 18 of the imaging means 4 is received from the camera 18 and subjected to edge extraction processing. Since the solder paste is composed of a group of solder balls having a diameter of several tens of μm, an edge information image in which many edges are extracted can be obtained. On the other hand, since there is no solder ball group in the solder leveler or the substrate material, such a large number of edges are not extracted. Then, the image processing means 26 performs expansion processing and compression processing on the edge information image and paints out the solder paste area.

Generally, when two straight lines having a gap of n pixels are expanded and compressed n times, the space between the two straight lines is filled. The number of times of expansion and compression required to fill the solder paste area differs depending on the material of the solder paste, and this number is input to the image processing means 26 before screen printing on the substrate P. The procedure will be described below. The sample board on which the solder paste of the same material as the solder paste to be inspected is printed is imaged by the camera 18 of the first image pickup means 4 while irradiating the sample board with light by the illuminating device 20 and image processing means is obtained. The edge extraction processing is performed by 26, and the obtained edge information image is displayed on the display 9. The operator operates the operation unit 31 (described later) while looking at the display 9 to repeatedly perform the expansion process and the compression process, thereby painting the solder paste area. By this, the number of times of the expansion processing and the compression processing required for filling the solder paste area can be determined, and the operator can determine the number of the expansion processing and the compression processing.
Is input to the image processing means 26 via the.

The determination means 27 calculates the area of the solder paste area by counting the number of pixels of the solder paste area painted out by the image processing means 26, and further calculates the center of gravity of the solder paste area. Is calculated. Then, the determination means 27
Compares the information with the area information and the position information stored in the RAM in advance, and determines pass / fail based on whether or not the difference is equal to or less than an allowable value.

In FIG. 3, reference numeral 28 denotes a housing,
Numerals 29 and 30 denote gull-wing type doors for opening and closing openings (not shown) provided on the front and rear surfaces of the housing 28. Also, an operation unit 3 for the operator to operate the screen printing machine is provided on the upper front surface of the housing 28.
1 is provided.

Next, the operation of the screen printing apparatus configured as described above will be described. First, before performing screen printing on the substrate P, the camera 18 of the first imaging unit 4 and the camera 21 of the second imaging unit 5 are aligned.

When the substrate P is placed on the supply conveyor 7,
A photo sensor (not shown) detects this, and a substrate stopper (not shown) is lowered to hold the substrate P so as not to move during transportation. Next, the substrate support table 2 moves to the left and is connected to the supply conveyor 7. The supply conveyor 7 is driven, and the substrate P is conveyed toward the substrate support table 2 in conjunction with the conveyance mechanism of the substrate support table 2.
When the substrate P reaches a predetermined position on the substrate support table 2,
The supply conveyor 7 stops. Then, after the substrate P is positioned by a known positioning mechanism (not shown), the substrate support table 2 moves rightward and returns to the original position (hereinafter, referred to as the origin position).

Next, the camera 18 of the first image pickup means 4 moves in the X-axis direction and the Y-axis direction to pick up two position recognition marks on the substrate P. The image is stored in a recognition board (not shown) of the control means 10. The control unit 10 recognizes the position of each position recognition mark from the image stored on the recognition board, and stores the position in the memory.

Next, the camera 18 and the screen supporting means 3 are retracted in the horizontal direction, and the substrate supporting table 2 is raised.
When the substrate P reaches the printing position, the substrate support table 2 stops. The camera 21 of the second imaging means 5 moves in the X-axis direction and the Y-axis direction to capture two position recognition marks on the substrate P, and the images are stored on the recognition board. Control means 1
0 recognizes the position of each position recognition mark from the image stored in the recognition board and compares the obtained position information with the position information obtained by the first imaging means 4 stored in the memory. The difference between the two is calculated. This shift is camera 1
8 and the camera 21 and the substrate support table 2
This is caused by distortion of the second moving mechanism 12 that moves in the axial direction. The control means 10 calculates the amount of movement of the camera 18 for eliminating this deviation, moves the camera 18, and stores the position as a new reference position of the camera 18 in the memory. Then, the camera 18 retreats, the substrate support table 2 moves down to the origin position, the screen 3 returns to the printing position, and the camera 18 returns to the reference position.

Next, a case where screen printing is actually performed on the substrate P will be described. First, the camera 18 of the first imaging unit 4 moves in the X-axis direction and the Y-axis direction to capture two position recognition marks on the substrate P, and the images are stored in the control unit 1.
0 is stored in the recognition board. Then, the control means 10 recognizes the position of each position recognition mark from the image stored in the recognition board, and the position information is stored in the memory. Also,
The camera 21 of the second imaging means 5 moves in the X-axis direction and the Y-axis direction to capture two position recognition marks on the screen printing machine S, and the images are stored in the recognition board. Then, the control means 10 recognizes the position of each position recognition mark from the image stored in the recognition board, and compares the obtained position information with the position information of the position recognition mark of the substrate P stored in the memory. The shift between the substrate P and the screen S is calculated.

The control means 10 calculates the amount of movement of the substrate support table 2 and the screen support means 3 for correcting this displacement, and based on the obtained values, the moving mechanism 11 and the rotating mechanism 12 of the substrate support table 2 The motor of the moving mechanism 17 of the screen supporting means 3 is driven to drive the substrate P and the screen S.
Is corrected.

Next, the cameras 18 and 21 of the first and second imaging means 4 and 5 are retracted, and the substrate support table 2 is raised.
When the substrate P reaches the printing position, it stops. Then, the print head 6 is lowered, the squeegee 23 slides along the upper surface of the screen S, and the solder paste is printed on the substrate P. When printing is completed, the substrate support table 2 is lowered,
When it reaches the home position, it temporarily stops, moves rightward, and is connected to the discharge conveyor 8. Then, the positioning mechanism for positioning the substrate P is released, the discharge conveyor 8 is driven, and the transfer mechanism of the substrate support table 2 is interlocked with the discharge conveyor 8 to transfer the substrate P toward the discharge conveyor 8. Substrate P
Reaches a predetermined position on the discharge conveyor 8, the discharge conveyor 8 stops. Then, the substrate support table 2 returns to the origin position.

Thereafter, the discharge conveyor 8 is driven, and the substrate P is transported to a chip mounter (not shown). After the electronic components are attached, the substrate P is transported into a furnace, and the electronic components are soldered. On the other hand, the substrate support table 2 is connected to the supply conveyor 7 and receives the next substrate P from the supply conveyor 7. Then, the above steps are repeated, and screen printing is performed on the substrate P.

In this screen printing machine, the inspection device inspects the solder paste printed on the substrate P at predetermined intervals. The cycle is set based on the number of printed boards, time, and the like. A procedure in which the inspection device inspects the solder paste will be described with reference to the flowchart of FIG.

When the substrate support table 2 on which the substrate P after printing has been completed returns to the origin position, the camera 18 of the first imaging means 4 moves above the substrate P, and the illumination device 20 moves the substrate P
The camera 18 captures an image of the substrate P in this state (step # 10).

The obtained plane image of the substrate P is sent to the image processing means 26, and subjected to edge extraction processing. As described above, since the solder paste is composed of a group of solder balls having a diameter of several tens of μm, an edge information image in which many edges are extracted is obtained (step # 15).

Next, the image processing means 26 performs a predetermined number of expansion processing and compression processing on the edge information image, paints the solder paste area (steps # 20 and # 25), and A binarization process is performed based on the set threshold (step # 30).
Then, the determining means 27 calculates the area of the solder paste by counting the number of pixels in the solder paste area, further calculates the position of the center of gravity of the solder paste area, and thereby calculates the position of the solder paste (step # 3).
5). Then, the determining means 27 calculates a difference between these numerical values and the reference value stored in the memory, and determines whether the difference is within an allowable value (step # 4).
0).

If the determination means 27 determines that the solder paste area is not present, a display indicating NG is displayed on the display device 9 and the processing is interrupted. Further, when the position of the solder paste area is not satisfied, the control means 10 drives the motors of the first moving mechanism 11, the rotating mechanism 12, and the moving mechanism 17 of the screen supporting means 3 of the substrate supporting table 2 to drive the substrate P.
Between the screen and the screen S is corrected.

In the above embodiment, the substrate P on the substrate support table 2 at the origin position (down position) is irradiated with light by the illuminating device 20 of the first image pickup means 4 and the substrate P is illuminated.
Is picked up by the camera 18 of the first image pickup means 4 and the obtained planar image is subjected to image processing to recognize the solder paste. Instead of this, the board at the printing position (elevated position) is used. The substrate P on the support table 2 is imaged by the camera 21 of the second imaging means 5 while irradiating the substrate P with light by the illumination device of the second imaging means 5, and the solder paste is recognized from the obtained planar image. It may be.

In the above embodiment, the cameras 18, 2
1 and the second moving mechanism 13 of the substrate support table 2.
In order to eliminate the displacement between the substrate P and the screen S caused by the distortion of the substrate P, images of the substrate P are taken by the cameras 18 and 21, and the displacement of the obtained position information is calculated. Is changed, the reference position of the camera 21 may be changed instead.
Further, without changing the reference position of the camera, an offset value to be added to the movement amount of the substrate support table 2 and / or the screen support means 3 in order to eliminate the displacement is calculated,
This may be added to the movement amount of the substrate support table 2 and / or the screen support means 3.

[0040]

According to the solder paste recognition method of the first aspect, only the solder paste area including the solder ball group is painted out, so that the solder paste area can be clearly distinguished from the substrate cloth and the solder leveler area. it can. In addition, according to this solder paste recognition method, since a light source that emits special light such as slit light is not required,
A solder paste inspection device can be configured at low cost. If there is an illumination device for photographing the substrate, it can be used.

According to the screen printing machine of the second and fourth aspects, since the solder paste inspection apparatus employs the solder paste recognition method of the first aspect, the solder paste region can be accurately recognized and the cost is low. It is.

According to the third and sixth aspects of the screen printing machine, the quality of the solder paste is periodically determined, so that it is possible to check the distortion of the apparatus due to aging or temperature change, clogging of the screen, and the like. By performing adjustment and maintenance of the screen printing machine based on the above, it is possible to obtain a substrate having a high-quality solder paste with less printing shift and chipping.

According to a fifth aspect of the present invention, when the determining means determines that the position of the solder paste area is not correct, the displacement between the substrate and the screen is corrected. A substrate can be obtained.

[Brief description of the drawings]

FIG. 1 is a front view of a main part of a screen printing machine according to an embodiment of the present invention.

FIG. 2 is a view taken along the line AA of FIG. 1;

FIG. 3 is a right side view of the screen printing machine in FIG.

FIG. 4 is a block diagram showing a schematic configuration of a solder paste inspection device.

FIG. 5 is a flowchart showing a procedure for determining the quality of the solder paste by the solder paste inspection device.

[Explanation of symbols]

 2 substrate support table 3 screen support means 4 first imaging means 5 second imaging means 10 control means 11 first moving mechanism 12 rotating mechanism 13 second moving mechanism 17 moving mechanism of screen supporting means 3 18 camera of first imaging means 4 21 camera of second imaging means 5 26 image processing means 27 discriminating means

Claims (6)

[Claims] 1. A method of recognizing a solder paste printed on a substrate by distinguishing the solder paste from other elements on the substrate, wherein the substrate is irradiated with light and an image of the substrate is taken by a camera. A step of obtaining a plane image; a step of performing edge extraction processing on the plane image to obtain an edge information image; and a step of performing expansion processing and compression processing on the edge information image and painting out a solder paste area. A solder paste recognition method characterized by the following. 2. A substrate support table, an illumination device disposed above the substrate support table, for irradiating light to a substrate placed on the substrate support table, and an illumination device disposed above the substrate support table, A camera for imaging the substrate, and performing edge extraction processing on a planar image of the substrate obtained by imaging the substrate with the camera while irradiating the substrate with screen with light by the illumination device. Image processing means for performing expansion processing and compression processing on the obtained edge information image to paint the solder paste area, and determination means for determining whether the area and position of the solder paste area painted by the image processing means are good or bad. Screen printing machine characterized by the above-mentioned. 3. The substrate is periodically imaged by the camera while irradiating the substrate after screen printing with light by the illumination device, and the obtained planar image of the substrate is processed by the image processing means. 3. The screen printer according to claim 2, wherein the determination unit determines whether the area and the position of the solder paste area of the substrate are good or bad. 4. A first moving mechanism for moving in the direction of the X axis extending in the horizontal direction, a second moving mechanism for moving in the direction of the Z axis extending in the vertical direction, and a rotating mechanism for rotating in a horizontal plane. A substrate support table having, an illumination device disposed above the substrate support table and irradiating light to a substrate mounted on the substrate support table; and an illumination device disposed above the substrate support table, and arranged in a horizontal direction. A screen supporting means having a moving mechanism for moving in the direction of the extending Y axis; and being disposed between the substrate supporting table and the screen supporting means, the screen supporting means being movable in the directions of the X axis and the Y axis. A first imaging unit having a camera for imaging; and a first imaging unit disposed above the screen supporting unit, capable of moving in the directions of the X axis and the Y axis, and taking an image of the screen supported by the screen supporting unit. A second imaging means having a camera, prior to performing the screen printing to the substrate, perform position recognition of the substrate by imaging the substrate to the first imaging means,
The second image pickup means picks up the image of the screen to recognize the position of the screen, calculates the displacement between the substrate and the screen from the obtained position information of the substrate and the screen, and calculates the displacement between the substrate and the screen. A first moving mechanism and a rotating mechanism, control means for driving the moving mechanism of the screen supporting means to correct the displacement, and irradiating the substrate after screen printing with light by the illuminating device. An image in which edge extraction processing is performed on a planar image of the board obtained by imaging with the first or second imaging means, expansion processing and compression processing are performed on the obtained edge information image, and a solder paste area of the board is filled. Processing means; determining means for determining whether the area and position of the solder paste area filled by the image processing means are good or bad , Screen printing machine, characterized in that it comprises a. 5. The control means drives a first movement mechanism and a rotation mechanism of the substrate support table and a movement mechanism of the screen support means when the determination means determines that the position of the solder paste area is not present. The screen printing machine according to claim 4, wherein the displacement between the substrate and the screen is corrected. 6. While periodically irradiating the substrate after screen printing with light by the illuminating device, the substrate is imaged by the first or second imaging means, and the obtained planar image of the substrate is obtained by 6. The screen printing machine according to claim 4, wherein the processing is performed by an image processing unit, and the area and position of the solder paste area of the substrate are determined by the determination unit.