JP2004325338A - Device and method for inspecting printed circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device to precisely detect an appearance defect in a printed circuit board. <P>SOLUTION: This device/method is provided with a conveying means 12 for conveying line-directionally the printed circuit board 1 having a mark line 1b arrayed continuously with rectangular marks having sides CA crossed diagonally with a conveying direction D, a line sensor 13 for image-picking up the board 1 to transmit an inspected image data S1, image processing means 17A, 17B for forming an inspected image V based on the data S1 to extract the mark line 1b as a mark image, a correction means for correcting the inspected image V in response to a measured result of the mark image, and a determination means 17D for comparing an inspected image Vm after the correction with a reference image Vo of the printed circuit board 1 to conduct determination in response to a result therein. The correction means is constituted to measure an inclination of the side CA corresponding to the side CA of the mark image and a change thereof and to correct the two-dimensional inspected image V. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a printed board inspection apparatus and a printed board inspection method for detecting an appearance defect of a printed board.
[0002]
[Prior art]
In the appearance defect inspection of a printed circuit board on which electronic components are mounted or on which electronic components are mounted, the appearance of the printed circuit board is captured as an image, and this image is compared with a regular appearance image to detect a defect based on the difference. An inspection method and an inspection apparatus for performing an inspection by the method have been developed.
As an example of this inspection apparatus, there is an apparatus in which a printed circuit board is moved by a transporting means with respect to a fixedly arranged line sensor to capture an image, and a two-dimensional appearance image of the printed circuit board is obtained and inspected (see Patent Document 1). .
[0003]
Also, in this example, in order to improve the problem that the image captured by the speed modulation when moving the printed circuit board expands and contracts in the movement direction, an expansion / contraction amount detection mark is formed on the printed circuit board and the image is captured. The moving speed of the substrate is controlled so as to match the expansion / contraction amount detection mark of the image and the reference expansion / contraction amount detection mark stored in advance.
[0004]
[Patent Document 1]
JP-A-2-40540
[Problems to be solved by the invention]
By the way, the pattern of the printed board may be formed with an inclination with respect to the outer shape of the board or a reference portion, or the pattern may be displaced in a direction orthogonal to a moving direction at the time of inspection.
These are all regarded as defects (defective) in recent high-density mounting. However, conventional methods and apparatuses measure the intervals of pattern marks provided at equal intervals in the moving direction and determine a reference interval. The inclination and the displacement of the pattern and the components mounted on the pattern could not be accurately detected.
[0006]
In addition, if the speed modulation during the movement of the substrate occurs finely, the conventional method and apparatus average the speed modulation generated between the pattern marks without detecting it, so that especially the fine pattern and the component mounting on the fine pattern If the state had a defect, it could not be reliably detected.
[0007]
Therefore, in these cases, there is a problem that the detected image cannot be reliably corrected, and the appearance defect cannot be accurately detected in comparison with the reference image.
[0008]
Therefore, an object of the present invention is to provide a printed circuit board inspection apparatus and a printed circuit board inspection method capable of accurately detecting appearance defects in a printed circuit board pattern and component mounting state.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has the following configuration as means.
That is, claim 1 is a printed circuit board inspection apparatus for inspecting the appearance of a printed circuit board 1, wherein the printed circuit board 1 has a mark array 1 b on the surface in which marks ABC having a predetermined shape are continuously arranged in one direction. Transport means 12 for transporting the printed circuit board 1 in the direction, a line sensor 13 for one-dimensionally capturing the printed board 1 while transporting the printed board 1 and transmitting the captured image data S1, and transmitting the captured image data S1 to 2 Image processing means 17A and 17B for forming a two-dimensional two-dimensional image to be inspected V and extracting the image of the mark sequence 1b as a mark image from the two-dimensional image to be inspected V, and measuring and processing the extracted mark image A correcting means for correcting the two-dimensional image to be inspected V according to the result, and an image of a surface serving as a reference of the printed circuit board 1 is previously stored as a reference image V0. The storage unit 16 retrieves the reference image V0 stored in the storage unit 16 from the storage unit 16 and compares the reference image V0 with the corrected two-dimensional inspection image Vm. Determining means 17D for determining the presence or absence of an appearance defect;
The mark ABC is a square having a side CA obliquely intersecting with the direction D. The correction unit 17C is configured to determine the inclination of the image of the side corresponding to the side CA in the mark image with respect to the direction D and the change in the inclination. A printed circuit board inspection apparatus is configured to measure and correct the two-dimensional inspection image V according to the measurement result.
[0010]
In order to solve the above problems, the present invention has the following procedure as means.
That is, the second aspect of the present invention forms a mark array 1b on the surface of the printed circuit board 1 to be inspected as a mark array 1b in which the square marks ABC are continuously arranged in one direction obliquely crossing one side CA of the square. The board 1 is conveyed in the above direction, and during this conveyance, an image of the front surface of the printed circuit board 1 is captured by the line sensor 13 and the data of the image is sent out as the image data S1 to be inspected. A two-dimensional two-dimensional inspection image V is formed from the data S1, and an image of the mark sequence 1b is extracted from the two-dimensional inspection image V as a mark image, which corresponds to the one side CA in the extracted mark image. The inclination of the image of the side with respect to the direction D and the change in the inclination are measured, and the two-dimensional inspection image V is corrected according to the measurement result. Comparing the image V0 of the surface of the printed circuit board set as a quasi-image, a printed circuit board inspection method and performing presence judgment of appearance defects according to the comparison result.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram for explaining a printed circuit board to be inspected in an embodiment of the printed circuit board inspection method of the present invention,
FIG. 2 is a diagram for explaining an embodiment of the printed circuit board inspection method of the present invention,
FIG. 3 is another diagram illustrating an embodiment of the printed circuit board inspection method of the present invention.
FIG. 4 is a diagram showing a configuration of an embodiment of the printed circuit board inspection apparatus of the present invention,
FIG. 5 is a diagram for explaining correction in the embodiment of the printed board inspection method of the present invention.
[0012]
First, a printed board inspection apparatus of the present invention and a printed board to be inspected by the apparatus will be described with reference to FIGS. The following description is for the case of detecting a defect such as a pattern on a printed circuit board before mounting electronic components, but the same applies after mounting electronic components.
[0013]
First, a printed circuit board to be inspected will be described.
In FIG. 1A, a land 1c for mounting electronic components and a wiring pattern (not shown) are formed on the surface of the printed board 1 in a later step.
Further, a pair of positioning marks 1a is formed near the diagonal of this surface.
Further, a synchronous mark row 1b is formed in which marks of right triangles ABC are continuously arranged along the transport direction D in which the substrate is transported at the time of inspection.
[0014]
FIG. 1B shows details of one triangle ABC (hereinafter, referred to as a unit mark Δ) of the synchronization mark row 1b.
[0015]
The unit mark Δ has a first side (bottom side) AB having a length L on a line segment P1-P2 along the transport direction D and a second side B- orthogonal to the line segment P1-P2. A triangle formed by C and a third side CA intersecting the second side BC at an interior angle θ.
It is preferable that the length L of the first side is set to 2 mm to 5 mm and the internal angle θ is set to 30 ° to 60 °. However, the size of the component to be mounted, the area on the substrate that can be occupied by the synchronization mark, or the conveyance The optimum L and θ can be set based on the speed and the like.
[0016]
The positioning mark 1a and the synchronization mark row 1b are formed in a color having a higher luminance than the base color of the printed circuit board 1 so that it can be easily extracted in image processing described later.
If the image can be extracted, the image may be differentiated by another method. For example, the image may be formed to have a color different in saturation from the base color of the printed circuit board 1 or to have a different reflectance.
[0017]
Next, the overall configuration of the printed board inspection apparatus of the present embodiment will be described with reference to FIG.
This device has a transport driving device 11 and a transport table 12a, and transports the printed circuit board 1 in the transport direction D, and detects a position of the transported printed circuit board 1 and sends out a detection signal S4. Sensor 15, a detecting unit 17 for determining the presence or absence of an appearance defect of the printed circuit board 1, and a one-dimensional image of the surface of the printed circuit board 1 which is fixed to the inspection apparatus by fixing means (not shown), and the image data signal S1 And a board position detection sensor 14 that detects a positioning mark 1a serving as a reference position of the printed circuit board 1 and sends the position to the detection unit 17 as position information S2. A storage unit 16 that sends the stored image data signal S3 of the regular printed circuit board to the detection unit 17 and a line based on the detection signal S4 from the detection sensor 15 And a line sensor control unit 18 sends a control signal S5 for controlling the fetching operation of the capacitors 13.
[0018]
The detection unit 17 described above includes a two-dimensional image forming unit 17A that creates a two-dimensional image V by integrating and developing the one-dimensional image data signal S1 sent from the line sensor 13, and converts the two-dimensional image V into two-dimensional images. A binarization extraction unit 17B for performing a binarization process to extract an image of a synchronization mark string 1b portion; a regular synchronization mark string included in a regular printed circuit board image V0 sent from the storage unit 16; The correction unit 17C compares the synchronization mark string 1bv extracted in 17B and corrects the two-dimensional image V according to the result, and the two-dimensional image Vm corrected by the correction unit 17C and the image V0 of the regular printed circuit board. And a determination unit 17D for determining the presence or absence of a defect by comparing the above.
[0019]
A printed board inspection method for inspecting a printed board using the printed board inspection apparatus of the present embodiment having such a configuration will be described in detail below.
[0020]
The printed circuit board 1 to be inspected is set on the transfer table 12a of the board transfer section 12, and is transferred in the transfer direction D by driving the board driving device 11 (see FIG. 4).
When the printed circuit board 1 is transported to a predetermined position, a detection sensor 15 disposed at a predetermined position on the lower surface side detects the printed circuit board 1 and sends out a detection signal S4 to the control unit 18.
[0021]
The control unit 18 sends a control signal S5 to the line sensor 13 based on the detection signal S4 so that the line sensor 13 starts capturing an image.
Further, as the printed board 1 is transported, the board position detection sensor 14 detects the positioning mark 1a and sends out the position information signal S2 to the detection unit 17.
[0022]
On the other hand, the one-dimensional image data S1 including the synchronization mark sequence 1b is transmitted to the detection unit 17 from the line sensor 13 that has started capturing by the control signal S5.
Based on the image data S1, the two-dimensional image forming unit 17A of the detecting unit 17 forms a two-dimensional image V, and the binarizing extracting unit 17B synchronizes the two-dimensional image V using a well-known binarizing method. The mark sequence 1b is extracted, and information on the extracted synchronization mark sequence 1bv is sent to the correction unit 17C.
[0023]
The speed at which the printed circuit board 1 is transported varies minutely due to variations in the characteristics of the drive motor, slippage of drive components such as a belt used for drive, backlash and backlash of the drive mechanism, and the like.
Therefore, the formed two-dimensional image V is an image that expands and contracts in the transport direction according to the speed modulation, and the extracted synchronization mark sequence 1bv is a regular right triangle as shown in FIG. Instead, the shape is changed according to the velocity modulation as shown in FIG. In particular, this velocity modulation appears as the magnitude of the inclination of the hypotenuse of the triangle and its change.
[0024]
Accordingly, the correction unit 17C calculates the inclination of the hypotenuse with respect to the conveyance direction and the rate of change of the inclination to detect the conveyance speed and its change, and corrects the two-dimensional image V so as to offset the expansion and contraction in the conveyance direction. I do.
[0025]
A method for obtaining the inclination of the hypotenuse will be described with reference to FIG.
The correction unit 17C measures the coordinates (Xk1, Yk1) and (Xk2, Yk2) of points K1 and k2 where the GG line where the synchronization mark Δ is orthogonal to the transport direction D intersects the oblique side CA and the bottom side AB. . Then, the distance K between the intersections is obtained from the Y component, and the time change of this K is calculated as the speed.
Accordingly, the speed obtained from the mark Δ in FIG. 2A is represented in a substantially rectangular shape with a constant period as shown in FIG. 2B.
[0026]
Therefore, for example, when a synchronization mark having a distorted oblique side subjected to velocity modulation as shown in FIG. 5B is extracted, the inclination of the oblique side, that is, the velocity, is detected as shown in FIG. 5C.
Of course, if the hypotenuse is a straight line, the speed is constant, and the greater the inclination of the hypotenuse, the greater the speed. The expansion and contraction of the formed two-dimensional image V in the transport direction is corrected according to the speed and the change in the speed.
[0027]
Also, the allowable speed change range that does not affect the defect evaluation is set as Rmax and Rmin, and the two-dimensional image V can be corrected when the range is exceeded.
Further, the upper limit and the lower limit of the large speed change range may be set to R1max and R2min, and the drive device may be controlled so as to stop the device as an abnormal operation when the range is exceeded. An example of this setting is shown in FIGS. 3 (a) and 3 (b).
FIG. 3A shows a case where the speed is stable, and FIG. 3B shows a case where the speed is unstable and a part of the speed is an abnormal value exceeding R1max.
[0028]
The above description of the correction is for correcting the expansion and contraction in the transport direction when the synchronization mark is parallel to the transport direction. However, this mark is actually tilted with respect to the transport direction due to misalignment during mark formation. You may have.
For this reason, it is necessary to correct the above-described speed and its change including the inclination of the synchronization mark row with respect to the transport direction.
Therefore, as described above, the correction unit 17C is configured to obtain the position of the extracted synchronization mark row 1bv in the direction orthogonal to the transport direction as coordinates, and also detect the inclination of the extracted mark row with respect to the transport direction D. .
[0029]
For example, in FIG. 1, the correction unit 17C synchronizes with the coordinate system in which the transport direction D is the X coordinate axis from the coordinates (X1, Y1) and (X2, Y2) of, for example, both ends P1 and P2 of the synchronization mark row 1b. The inclination TL of the mark row 1b is obtained as follows: TL = (Y2-Y1) / (X2-X1).
The two-dimensional image Vm formed in the two-dimensional image forming unit 17A is subjected to the above-described expansion and contraction correction in the transport direction and the inclination correction according to the TL value together, so that the two-dimensional image Vm should be compared with the normal image with higher accuracy. A two-dimensional image can be obtained.
[0030]
Next, a method for determining whether or not a printed circuit board to be inspected has a defect will be described. Specifically, based on the above-described correction method, the position of a specific part of the printed circuit board 1 to be inspected is obtained, and the position is compared with the position on the image data of a regular printed circuit board where the part should be. Do with. This will be described with reference to FIG.
[0031]
For example, assuming that the L value of the unit mark Δ of the synchronization mark row 1b is 10 in the X direction and a part P3 where the distance X0 = 25 from a predetermined reference position is to be inspected as shown in FIG. ), The X value at which the area M (hatched portion) becomes 5 is determined in the right direction of the figure from the section where X = 20, and is set as the position Xp of the part P3 on the inspection target substrate.
Then, the presence or absence of a defect is determined based on whether or not the difference between Xp and X0 falls within a preset allowable range.
Therefore, according to the above-described method, since the position of the portion to be compared and inspected can be continuously and accurately obtained in consideration of the speed modulation and the inclination with respect to the transport direction, the accuracy of detecting a defect is greatly improved.
[0032]
The embodiments of the present invention are not limited to the above-described configuration, and may be modified without departing from the gist of the present invention.
[0033]
For example, in the above-described embodiment, the line sensor is fixed and the substrate side is moved, but the substrate may be fixed and the line sensor may be moved.
It goes without saying that the shape of the synchronization mark is not limited to a triangle, and the same effect can be obtained as long as the shape has a side oblique to the transport direction.
Alternatively, the line AB for obtaining the inclination may be provided independently of the synchronization mark row, and the synchronization mark may be formed in a rhombus shape.
Although the setting of L and θ has been described above, it is particularly preferable that θ be set to 45 ° at a regular transport speed in the two-dimensional image V to be formed since the speed change can be grasped most accurately.
[0034]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to detect the appearance defect of the pattern of the printed circuit board or the component mounting state with high accuracy without being affected by the modulation of the transport speed or the displacement other than the transport direction. Get.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a printed circuit board to be inspected by an embodiment of a printed circuit board inspection apparatus according to the present invention.
FIG. 2 is a diagram illustrating an embodiment of a printed circuit board inspection method according to the present invention.
FIG. 3 is another diagram illustrating an embodiment of the printed board inspection method of the present invention.
FIG. 4 is a diagram showing a configuration of an embodiment of a printed circuit board inspection apparatus of the present invention.
FIG. 5 is a diagram illustrating correction in an embodiment of the printed circuit board inspection method of the present invention.
[Explanation of symbols]
1 Printed circuit board 1a Positioning mark 1b Synchronous mark (row)
1bv (extracted) synchronization mark 1c land 11 transport drive unit 12 substrate transport unit 12a transport table 13 line sensor 14 substrate position detection sensor 15 detection sensor 16 storage unit 17 detection unit 17A two-dimensional image forming unit 17B binarization extraction unit 17C Correction unit 17D Judgment unit ABC Mark D Transport direction L Length (at the bottom) V (Formed) 2D image Vm (Corrected) 2D image V0 (Stored) Printed board image S1, S3 image Data signal S2 Position information S4 Detection signal θ Inner angle Δ Unit synchronization mark P1, P2 End point Rmax, Rmin Upper limit, lower limit R1max, R1min (of large speed change range) Upper limit, lower limit TL slope

Claims (2)

A printed circuit board inspection device for inspecting the appearance of a printed circuit board,
Conveying means for conveying a printed circuit board having a mark array in which marks of a predetermined shape are continuously arranged in one direction formed on the surface in the direction,
A line sensor that one-dimensionally images the printed board while transporting the printed board and sends out the imaged data,
Image processing means for forming a two-dimensional two-dimensional image to be inspected from the transmitted image data and extracting an image of the mark train as a mark image from the two-dimensional image to be inspected;
Correction means for measuring the extracted mark image and correcting the two-dimensional image to be inspected according to the result;
Storage means for storing in advance a reference surface image of the printed circuit board as a reference image,
Determining means for extracting the reference image stored in the storage means from the storage means, comparing the reference image with the corrected two-dimensional image to be inspected, and determining presence / absence of an appearance defect according to the result; With
The mark is a rectangle having a side oblique to the direction,
The correction unit measures an inclination of the image of the side corresponding to the side of the mark image with respect to the direction and a change in the inclination, and corrects the two-dimensional inspection image according to the measurement result. A printed circuit board inspection device characterized by comprising. Forming square marks on the surface of a printed circuit board to be inspected as a mark row continuously arranged in one direction oblique to one side of the square;
Transporting the printed circuit board in the direction,
During this conveyance, an image of the surface of the printed circuit board is taken by a line sensor and the data of the image is transmitted as image data to be inspected,
Forming a two-dimensional two-dimensional inspection image from the transmitted inspection image data and extracting an image of the mark sequence from the two-dimensional inspection image as a mark image;
Measuring an inclination of the image of the side corresponding to the one side in the extracted mark image with respect to the direction and a change in the inclination,
Correcting the two-dimensional inspection image according to the measurement result,
A method of inspecting a printed circuit board, comprising: comparing the corrected two-dimensional image to be inspected with an image of the surface of the printed circuit board set in advance as a reference image, and determining whether there is an appearance defect based on the comparison result.

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