JPH0619252B2 - Soldering inspection device for printed wiring boards - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a soldering inspection apparatus for a printed wiring board, which inspects a soldering state of a printed wiring board on which circuit elements are mounted, and more specifically, to a printed wiring board soldering inspection apparatus. The present invention relates to a soldering inspection device for a printed wiring board, which inspects a solder bridge generated between lands.

[Prior Art] When soldering a circuit element to a printed wiring board, a solder bridge may occur between lands of the printed wiring board. It is difficult to eliminate such defects, and conventionally, for example, as in JP-A-57-17806, a pattern of a printed wiring board to be inspected is picked up by an industrial television camera and compared with the picked-up image. The normal printed wiring board pattern was displayed on the same TV screen and visually inspected.

Also, as in JP-A-60-256004, there has been known an apparatus for automatically inspecting a soldering state of a printed wiring board for a defect inside by setting a window.

[Problems to be Solved by the Invention] However, in visual inspection, there are many inspection points,
Since the inspection pattern is minute, the bridge may be overlooked. Moreover, since the inspection is performed manually, there are problems that the inspection standard varies depending on the inspector, and that the inspection takes a long time.

As an inspection device that automates the above inspection, for example, a printed wiring board on which circuit elements are mounted is imaged with an industrial television camera, and a soldering inspection window is set for this captured image, and a bridge is installed inside the window. A device for detecting whether or not it has occurred is also proposed. In this way, it is necessary to set the window to accurately predict the position where the bridge is generated in advance, together with a special unique techniques are required for the substrate in that this prediction, an unexpected location in the generator There is a fundamental problem that the bridge which cannot be detected cannot be detected. Further, in order to cope with an unpredictable bridge, it is necessary to set windows all over the board and individually inspect all windows, which requires a lot of time for setting and inspecting the windows.

[Means for Solving the Problems] The present invention made to solve the above problems is to provide a solder bridge that emits light between lands when soldering a circuit element to lands on a printed wiring board. A printed wiring board soldering inspection device for detecting, comprising: land pattern storage means for storing in advance a land pattern obtained by binarizing the land pattern on the printed wiring board; and a printed wiring board on which circuit elements are soldered. A binary image generating means for picking up the image, binarizing the picked-up image and outputting the binary image, and the binary image and the land pattern are superposed, and then the superposed image is enlarged to be a restored image. And a label for each of the isolated land of the restored image and the isolated land of the land pattern to generate a plurality of lands of the land pattern. Image recognition means for recognizing connectivity between lands of the restored image depending on whether or not the label corresponds to the label of the same land of the restored image, and solder for a printed wiring board, comprising: Attached inspection device is the gist.

Here, to store the land pattern in the land pattern storage means, a printed wiring board having no circuit element inserted therein is attached to the inspection apparatus, and the land pattern is read and binarized by the binary image generating means. This is possible by transferring this data to the land pattern storage means. Further, the design data of the printed wiring board may be transferred to the land pattern storage means.

Furthermore, an image pickup device using an image pickup tube, a CCD, or the like can be used to image the printed wiring board in the binary image generating means. Further, the binarization of the captured image output from this imaging device is performed by creating a histogram of the brightness of the pixels of the captured image and binarizing the captured image with a threshold value determined based on this histogram. Can be done by.

Further, the image can be enlarged in the pre-processing means by, for example, a process of setting all the four pixels on the top, bottom, left and right, or the surrounding eight pixels to 1 when the central pixel is 1.

[Operation] The soldering inspection apparatus for a printed wiring board according to the present invention firstly
The value image generating means captures an image of the printed wiring board to which the circuit element is soldered, binarizes the captured image, and outputs a binary image. Next, the preprocessing means superimposes the binary image and the land pattern of the printed wiring board stored in advance in the land pattern storage means, and then the superposed image is enlarged to generate a restored image. Then, the image recognition means labels each of the isolated land of the restored image and the isolated land of the land pattern,
The connectivity between the lands of the restored image is recognized based on whether or not the labels of the plurality of lands of the land pattern correspond to the labels of the same land of the restored image.

[Embodiment] A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a printed wiring board soldering inspection apparatus as an embodiment of the present invention. The inspection apparatus of this embodiment includes an image input system 5 for converting an image of the surface of the printed wiring board 2 to which the circuit element 1 is soldered into an image signal, and a soldering state of the printed wiring board 2 based on the image signal. And an image processing system 7 for recognizing.

Here, on the printed wiring board 2 to be inspected, as shown in FIG. 2, the lead wire 12 of the circuit element 1 is inserted into the land 10 of the printed wiring board 2 and fixed by the solder 14. The inspection apparatus of the present embodiment detects a solder bridge formed between the lands 10.

In FIG. 1, first, the image input system 5 is the printed wiring board 2
Of the illuminating device 21 arranged obliquely below the printed wiring board 2 to surround the printed wiring board 2 and the illuminating device 21. An industrial TV camera 26 provided above the window 24.

The diffuse reflection plate 23 shields ambient light and reflects the light from the lighting device 21 to generate uniform diffused light.
Irradiate the surface of. Then, the reflected light from the printed wiring board 2 enters the imaging lens 27 of the industrial television camera 26 through the window 24. The industrial television camera 26 converts the image on the printed wiring board 2 into an image signal and outputs it to the image processing system 7.

Next, the image processing system 7 binarizes the image signal to form a binary image, and a binarization unit 31 and a restored image which is an image to be inspected by performing predetermined image processing on the binary image. And a processing unit 35 for recognizing the connectivity between the lands based on the restored image. Also,
A histogram creation unit 38 is provided as a block that determines a threshold value when the image signal is binarized in the binarization unit 31, and the land of the printed wiring board 2 used for the processing in the preprocessing unit 33 and the processing unit 35. The land pattern storage unit 40 is provided as a block for storing the shape pattern (hereinafter, referred to as a land pattern).

The histogram creation unit 38 creates a histogram of pixel brightness, then determines a threshold value for binarizing the image signal, and outputs the threshold value to the binarization unit 31. Two large peaks corresponding to the brightness of the solder and non-solder in the image appear on the histogram. To determine the threshold, find the valley between these peaks. (A so-called mode method) or the like can be used.

The binarizing unit 31 binarizes the image signal based on the threshold value output from the histogram creating unit 38 and generates a binary image.

The preprocessing unit 33 includes a binary image and land pattern storage unit 40.
After overlapping with the land pattern of, the superimposed image is enlarged to generate a restored image.

The processing unit 35 recognizes the connectivity between the lands by comparing the restored image and the land pattern.

Next, the processing executed in the inspection apparatus will be described based on the flowchart shown in FIG.

First, in step S100, the land pattern of the printed wiring board 2 is input to the land pattern storage unit 40. Specifically, the process of inputting the design data of the land pattern of the printed wiring board 2 or the process of mounting the printed wiring board 2 in which the circuit element 1 is not inserted into the inspection device and imaging the land pattern is performed. . This process does not have to be performed every time and may be performed when the type of the printed wiring board 2 to be inspected is changed.

Next, in step S110, the printed wiring board 2 to be inspected is mounted, the surface of the printed wiring board 2 is captured by the industrial television camera 26, and an image signal corresponding to the captured image is input to the image processing system 7.

Then, in step S120, the image signal is binarized based on the threshold value output from the histogram creation unit 38 to generate a binary image.

Then, in step S130, the binary image and the land pattern are superimposed on each other and then enlarged to generate a restored image.

Here, the process of generating the restored image will be described with reference to FIG. As shown in the figure, it is assumed that a bridge 202 is formed between the lands 201 in the binary image 200 output from the binarizing unit 31. In this case, the pattern missing 203 and the bridge 2 are formed inside the land 201.
A disconnection 204 of 02 may occur. This omission 203
The cut 204 is caused because the solder is not flat as shown in FIG. 2 and the reflected light from the inclined portion does not enter the industrial television camera 26 depending on the inclination angle.

In step 130, the binary image 200 and the land pattern 210 stored in the land pattern storage unit 40 are first superposed, and subsequently the superposed image is enlarged. For example, when the central pixel is 1, the image is enlarged by a process of setting all 4 pixels on the top, bottom, left and right, or the surrounding 8 pixels to 1, etc. Therefore, the pattern omission 203 is removed by superimposing the images, and the cutting 204 of the bridge 202 is performed by enlarging the images.
A reconstructed image 220 in which is reconnected is generated.

Next, in step 140, the isolated area of the restored image is recognized. That is, as shown in FIG. 5B, the existence of the isolated area is checked for each scanning line of the restored image 220, and the isolated area labeled (labeled) is cut out. Fifth
In the restored image 220 of FIG.
5 are labeled 1 to 5 respectively, and five isolated areas are recognized.

Then, in step 150, the restored image 220 and the land pattern 210 stored in the land pattern storage unit 40.
((FIG. 5 (a)) is compared with the land pattern 210.
The areas corresponding to the lands 211 to 216 are the restored image 22.
When 0, it is determined whether or not it is isolated. In this case, it is difficult to perform accurate detection simply by comparing the number of lands of the land pattern 210 and the number of isolated areas of the restored image 220. This is because an extra isolated region may exist in the restored image 220 due to the influence of noise or the like. Therefore, in the present embodiment, the label numbers corresponding to the lands 211 to 216 of the land pattern 210 (the label numbers 1 to 5 attached to the isolated areas 221 to 225 of the restored image 220) are checked to find a plurality of lands. The method of determining that the lands are connected when they correspond to the same label number is used.

In FIGS. 5A and 5B, the lands 212 and 213 of the land pattern 210 correspond to the same label number 2 in the restored image 200, so it is determined that these lands are connected.

In this case, in step S160, an inspection result indicating that the printed wiring board 2 to be inspected has a bridge and is defective is output.

On the other hand, when all the areas corresponding to the lands of the land pattern 210 are isolated in the restored image 220, it is determined that the printed wiring board 2 to be inspected is a non-defective product in step S170. The inspection result indicating is output.

As described above, the soldering inspection apparatus for a printed wiring board according to the present embodiment restores the land pattern of the printed wiring board, which is stored in advance, and the binary image obtained by imaging the printed wiring board. Since the image is used, for example, even if the reflected light does not enter the industrial television camera 26 at the inclined portion of the solder on the land and it is recognized as 0 in the binary image, that is, the dark portion without solder, The pattern of the stored lands restores this part like a solder, so that the bridge can be accurately detected.

Moreover, even when the bridge is very thin or inclined and the reflected light does not enter the industrial television camera 26 and is cut by the binary image, the image is enlarged and the connection is restored again. It is possible to detect thin bridges and bridges with complicated shapes.

Therefore, according to this embodiment, the solder bridge generated on the printed wiring board can be automatically and accurately inspected.

[Effects of the Invention] As described above, according to the present invention, the bridge generated on the printed wiring board can be automatically inspected, and the precision and speed of the inspection can be increased.

Moreover, the binary image of the printed wiring board to which the circuit elements are soldered and the land pattern are superposed and then enlarged to generate a restored image, and the isolated land is labeled so that a plurality of land patterns can be labeled. The connectivity between the lands of the restored image is recognized depending on whether the labels of the individual lands correspond to the labels of the same lands of the restored image. Therefore,
It is possible to detect a bridge that does not know where it will occur over the entire area of the printed wiring board, and it is not necessary to have a unique technique such as experience of setting a window, and there is no trouble of setting a window.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a soldering inspection apparatus for a printed wiring board as an embodiment of the present invention, FIG. 2 is a sectional view of the printed wiring board, FIG. 3 is a flowchart showing an inspection process, and FIG. Explanatory drawing showing the generation processing of the restored image, FIG. 5 (a)
(B) is an explanatory view of a process of recognizing the connectivity between lands. 1 ... Circuit element 2 ... Printed wiring board 10 ... Land 14 ... Solder 26 ... Industrial camera 31 ... Binarization unit 33 ... Preprocessing unit 35 ... Processing unit 40 ... Land pattern storage unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihiro Mori 1-1, Showa-cho, Kariya city, Aichi Prefecture Nihon Denso Co., Ltd. Sozo Co., Ltd. Inspector Yasuko Eto (56) References JP-A 61-293658 (JP, A) JP-A 61-293659 (JP, A)

Claims (1)

[Claims] 1. A soldering inspection device for a printed wiring board, which detects a bridge of solder that emits light between lands when soldering a circuit element to a land on the printed wiring board. Land pattern storage means for storing in advance a land pattern obtained by binarizing the land pattern of No. 2, and a binary value for imaging the printed wiring board to which the circuit element is soldered, binarizing the captured image and outputting the binary image. Image generating means, preprocessing means for superimposing the binary image and the land pattern, and enlarging the superimposed image to generate a restored image; isolated land of the restored image and the land pattern Each of the isolated lands is labeled and whether or not the labels of a plurality of lands in the land pattern correspond to the labels of the same land in the restored image. Therefore, an image recognition means for recognizing the connectivity between the lands of the restored image, and a soldering inspection apparatus for a printed wiring board, comprising: