JPH07120233A - Method for inspecting soldering - Google Patents

Abstract

PURPOSE:To shorten the process time and improve the inspection efficiency by obtaining binarized data from pixel brightness in the inspection area of a printed wiring board soldered. CONSTITUTION:A lighting part 1 is provided with an LED 2 which is turned on/off by an imaging controller 12, and it lights a printed wiring board 5 to be inspected set on an X-Y table part 6. The X-Y table part 6 holds the board 5 and, based on the control signal from an X-Y controller 13, positions it in a specified place. An imaging part 3 images the board 5 with a CCD camera 7 controlled by the controller 12. The imaging signal is converted into brightness signal according to gray-level pixels by an A/D converter 9, and the stored (14) brightness signal is binarized by a picture processing part 10. The binarized data, together with reference data stored in the memory 14, is transferred to a decision part 11 by a CPU 15. The decision part 11 compares them together for inspection of defective/nondefective of soldering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soldering inspection method, and more particularly to a method for inspecting the solderability of electronic components (chip components) soldered on a printed wiring board.

[0002]

2. Description of the Related Art In the case of automatically soldering a printed wiring board on which electronic components are mounted, it is necessary to inspect whether or not there is a defective solder or a lack of solder. As these inspection methods, visual inspection or automatic inspection is used.

Visual inspection is often used because it is the simplest method and is inexpensive. However, visual inspection relies on the visual sense of workers, so if work is continued for a long time, fatigue will reduce reliability, and if there are a large number of soldered parts to be inspected or if the inspection target is small, you will miss solder defects. There is a fear.

As a solution to this problem, an automatic inspection method has recently been used. As an automatic inspection method, for example, as proposed in Japanese Patent Laid-Open No. 2-278105, illumination is performed from above the solder surface, the reflected light is imaged by a TV camera, and the inspection is performed by the bright and dark areas of the captured image. is doing.

[0005]

However, in the case of the prior art, since the area, that is, the two-dimensional data is used for the inspection, the amount of data to be processed is large, and the processing time is long and the inspection efficiency is poor. It was Therefore, it was not always sufficient for inspection of mass-produced products.

Therefore, an object of the present invention is to eliminate the above-mentioned inconvenience, and to reduce the data processing amount and the processing time in the method of automatically inspecting the soldering, thereby improving the inspection efficiency. To provide.

[0007]

In order to achieve the above object, the present invention provides, for example, as described in claim 1.
The soldered printed wiring board is illuminated from above and imaged, and the binarized line data is obtained by binarizing the brightness of the pixels in a predetermined inspection area, and at least the position of 0 or 1 It is configured to judge whether the soldering is good or bad.

[0008]

Since the inspection is performed by using the binarized data, that is, the one-dimensional data, the data processing amount and the processing time are significantly reduced and the inspection efficiency is improved, which is more suitable for mass-produced products.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram of an apparatus for carrying out the soldering inspection method according to the present invention, which comprises an illuminating section 1, an XY table section 6, an image pickup section 3 and a control section 8.

The illumination unit 1 is provided with an LED 2 which is turned on / off by a control signal output from the image pickup controller 12 of the control unit 8, and is an inspection target set on the XY table unit 6 by the LED 2. The printed wiring board 5 is illuminated.

The XY table portion 6 is a printed wiring board 5
On the basis of the control signal output from the XY controller 13 in the control unit 8
To position it in place.

The image pickup unit 3 is a CCD controlled by a control signal output from the image pickup controller 12 of the control unit 8.
Is provided with a camera 7, which picks up an image of the printed wiring board 5 and supplies an image pickup signal to the A / D converter 9.

The A / D converter 9 converts the image pickup signal into a luminance signal by means of a grayscale pixel and supplies it to the memory 14. CP
The luminance signal in the memory 14 is transferred to the image processing unit 10 by U15.
To perform binarization processing of the luminance signal, and the binarized data and reference data (stored in the memory 14 in advance)
Is transferred to the determination unit 11.

The determination unit 11 compares the binarized data with the reference data to inspect the quality of soldering. CPU15
Causes the CRT 17 to display the inspection result.

The quality inspection of soldering according to the present invention will be described below with reference to FIGS. 2 to 7.

FIG. 2 is a view showing the principle of reflection of illumination light, in which a chip component 4 is soldered to a printed wiring board 5. When the illumination light 19 is applied from above the substrate, the substrate 5
And the reflected light from the chip component is reflected upward. On the other hand, the light irradiated onto the solder portion 18 is reflected in an oblique direction because the solder surface has an inclination angle. In this invention, the quality of soldering is inspected by using such a principle.

FIG. 3 is an explanatory view of an image obtained by picking up an image of the printed wiring board 5 to be inspected. Since the reflected light from the solder portion 18 does not enter the camera 7, it is captured darkly. Reference numeral 20 indicates an inspection area. Inspection area 2
0 is determined by the soldering position of the chip component to the printed wiring board 5, and the memory 14 of the control unit 8 is preset.
It is memorized in the inside according to the board type and model.

FIG. 4 shows the inspection area 20 digitized by the number of pixels (x, y) to obtain luminance data. The resolution is 0 to 255. The luminance data is averaged or added in the x direction (shown in FIG. 3). The average value or the added value is hereinafter referred to as "line luminance data". Figure 5
(A) of the line luminance data (indicated by reference numeral 22)
Is shown as a graph.

Next, the line luminance data 22 is compared with the threshold value 21 and binarized. The threshold value 21 determines the brightness, and is appropriately set at the start of the inspection depending on the place where the inspection is performed or the brightness of the inspection image.

FIG. 5B shows the binarized data, and the exclusive OR of the binarized data and the reference data 23 (using the good soldering product data as shown in FIG. 5C) is used. Calculate exclusive OR (Fig. 5)
(D)). The reference data 23 is also obtained and stored in the memory 14 by the start of the inspection.

FIG. 5 (e) is an explanatory diagram showing the quality judgment work, which is based on whether or not "one value" (H) data exists in the judgment area 25 defined by the judgment lines 24a and 24b. To do. The determination lines 24a and 24b are preferably set to be equal to or slightly wider than those of the good soldering product data. In the case of (e) of FIG.
Soldering is defective because the data is included.

FIG. 6 is an explanatory diagram showing patterns that can occur during soldering and binarized data thereof. As patterns, unsoldered solder (a) without any solder, excessive solder with a small amount of solder (b), appropriate amount of solder with proper amount of solder (c), and excessive solder with excessive amount of solder (d) Then, there are five possible patterns of the missing item (e) in which the chip component is not mounted.

In FIG. 7, (c) of FIG. 6 is used as reference data,
The result when obtaining the exclusive OR with the binarized data of (a) to (e) is shown. In the patterns other than (c), since "1 value" exists in the determination area, it can be determined that all are defective.

In this embodiment, as described above, the one-dimensional data, which is the line luminance data, is obtained and compared with the reference data to make the determination. Therefore, the determination is made by using the two-dimensional data in the prior art. However, the amount of processed data is reduced, and the processing time, that is, the inspection time is shortened. Therefore, it is suitable for soldering inspection of mass-produced printed wiring boards. Furthermore, since the exclusive OR of the one-dimensional data and the reference data is obtained for the determination, the quality of the soldering can be accurately determined.

In the above, the inspection standard can be changed by raising or lowering the threshold value 21. If the threshold value is lowered, the inspection standard becomes stricter.

[0027]

According to the first aspect of the present invention, the amount of processed data can be reduced and the inspection time can be shortened. Therefore, it is possible to provide an optimum inspection method for soldering inspection of mass-produced printed wiring boards.

According to the second aspect, the quality of the soldering can be accurately determined.

[Brief description of drawings]

FIG. 1 is a block diagram generally showing an apparatus for carrying out a soldering inspection method according to the present invention.

FIG. 2 is an explanatory diagram showing the principle of reflection of illumination light, which is a prerequisite for the soldering inspection method according to the present invention.

FIG. 3 is an explanatory diagram illustrating an image obtained by capturing an image of a printed wiring board that is an inspection target with the apparatus of FIG.

FIG. 4 is an explanatory diagram showing the inspection area of FIG. 3 digitized by the number of pixels to obtain luminance data.

FIG. 5 is an explanatory diagram showing an operation of binarizing luminance data and obtaining an exclusive OR with reference data.

FIG. 6 is an explanatory diagram showing patterns that can occur in soldering and binarized data thereof.

7 is a timing chart showing exclusive OR of the binarized data and the reference data of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Illumination part 2 LED 3 Imaging part 4 Chip parts 5 Printed wiring board 6 XY table part 7 Camera 8 Control part 9 A / D conversion part 10 Image processing part 11 Judgment part 12 Imaging controller 13 XY controller 14 Memory 15 CPU 17 CRT 18 Solder part 19 Illumination light 20 Inspection area 21 Threshold value 22 Line luminance data 23 Reference data 25 Judgment area

Claims (2)

[Claims] 1. A soldered printed wiring board is illuminated from the upper side to be imaged, and the brightness of pixels in a predetermined inspection area is binarized to obtain binarized line data. A soldering inspection method characterized by determining the quality of soldering from at least one of the positions. 2. The soldering inspection method according to claim 1, wherein the binarized line data is compared with a reference value, and the exclusive OR is obtained to determine the quality of the soldering.