JP3038107B2 - Soldering inspection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art When automatically soldering a printed wiring board on which electronic components are mounted, it is necessary to inspect whether a solder defect or a lack of solder has occurred. As these inspection methods, a visual inspection or an automatic inspection is used.

[0003] Visual inspection is the simplest method and is often used because of its low cost. However, since visual inspection relies on the visual perception of workers, if work is continued for a long period of time, reliability will decrease due to fatigue, and if the number of soldered parts to be inspected is large or the inspection target is small, solder defects will be missed There is fear.

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

[0005]

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

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned disadvantages and to improve a solder shape and a solder shape when soldering.
It is an object of the present invention to provide a method for automatically inspecting the quality of a quantity and a missing part of a chip part, in which the data processing amount is reduced to shorten the processing time and thereby improve the inspection efficiency.

[0007]

In order to achieve the above object, the present invention is constituted, for example, as described in claim 1. Description will be made with reference to the reference numerals of the embodiments described below.
The soldered printed circuit board 5 is illuminated from above and imaged, and the brightness of the pixels in the predetermined inspection area is binarized to obtain binarized line data (FIGS. 6A to 6E). preset reference value consisting of one compared to (7 reference data) the exclusive oR of the zero value or 1 value over all the binarized line data said predetermined inspection area (FIG 7XOR Data) is obtained, and when the obtained exclusive OR contains one value, it is determined that the soldering is defective.

[0008]

The binarized data in a predetermined inspection area, that is,
Since the inspection is performed using the one-dimensional data, the data processing amount and the processing time are significantly reduced, the inspection efficiency is improved, and when there is one value in the result of obtaining the exclusive OR, it is determined to be defective. Therefore, when soldering over the entire inspection area, it is easy to determine the shape of the solder , the quality of the solder , and the missing parts of the chip components .
For example, it 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 a soldering inspection method according to the present invention, which comprises an illumination section 1, an XY table section 6, an imaging section 3, and a control section 8.

The illumination unit 1 includes an LED 2 that is turned on / off by a control signal output from an imaging 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 section 6 includes a printed wiring board 5
And based on the control signal output from the XY controller 13 in the control unit 8,
Is positioned at a predetermined position.

The imaging section 3 is a CCD controlled by a control signal output from an imaging controller 12 of the control section 8.
The camera 7 includes an image pickup device, and 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 using grayscale pixels and supplies the luminance signal to the memory 14. CP
U15 converts the luminance signal in the memory 14 into the image processing unit 10
To perform a binarization process on the luminance signal, and furthermore, the binarized data and reference data (stored in the memory 14 in advance).
Is transferred to the determination unit 11.

The judging section 11 compares the binarized data with the reference data to check the quality of the soldering. CPU15
Displays the inspection result on the CRT 17.

A description will now be given, with reference to FIGS. 2 to 7, of a soldering quality inspection according to the present invention.

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

FIG. 3 is an explanatory diagram of an image obtained by imaging the printed wiring board 5 to be inspected. Since the reflected light from the solder portion 18 is not incident on the camera 7, it is darkly imaged. 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 is determined in advance by the memory 14 of the controller 8.
The information is stored according to the type and model of the board.

FIG. 4 shows the inspection area 20 converted into numerical data 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”. FIG.
(A) shows the line luminance data (indicated by reference numeral 22).
Is shown in a graph.

Next, the line luminance data 22 is binarized by comparing it with a threshold value 21. The threshold value 21 determines the lightness and darkness, 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. 5 (b) shows the binarized data. Exclusive OR of such binarized data and reference data 23 (using good soldering data as shown in FIG. 5 (c)) is used. (Exclusive OR) (FIG. 5)
(D)). The reference data 23 is also obtained and stored in the memory 14 before the start of the inspection.

FIG. 5 (e) is an explanatory diagram showing the pass / fail judgment work, and is based on whether "one value" (H) data exists in the judgment area 25 defined by the judgment lines 24a and 24b. Do. The determination lines 24a and 24b are preferably set to be equal to those of the good soldering data or set somewhat wider. In addition, in the case of FIG.
Since data is included, soldering is defective.

FIG. 6 is an explanatory diagram showing patterns that can occur during soldering and their binarized data. The patterns are as follows: unsolder (a) with no solder at all, too little solder with a small amount of solder (b), appropriate amount of solder with an appropriate amount of solder (c), and excessive solder with too much solder (d) And five patterns of missing parts (e) in which chip components are not mounted.

FIG. 7 uses FIG. 6C as reference data,
The result when exclusive OR with the binarized data of (a) to (e) is obtained is shown. Patterns other than (c) have a “1 value” in the determination area, so that any pattern can be determined to be defective.

In this embodiment, as described above, one-dimensional data, which is line luminance data, is determined and compared with reference data for determination, so that determination is made using two-dimensional data in the prior art. On the other hand, the processing data amount is reduced as compared with the above, and the processing time, that is, the inspection time is reduced. Therefore, it is suitable for soldering inspection of printed wiring boards mass-produced. Further, since the exclusive OR of the one-dimensional data and the reference data is determined, 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 standards become stricter.

[0027]

According to the first aspect of the present invention, the amount of processing data can be reduced, the inspection time can be shortened, and the quality of soldering can be accurately determined over the entire predetermined inspection area. . Therefore, when soldering printed wiring boards mass-produced ,
It is possible to optimally inspect the quality of the solder and the missing parts of the chip parts .

[0028]

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram showing a principle of reflection of illumination light presupposed in a soldering inspection method according to the present invention.

FIG. 3 is an explanatory diagram illustrating an image obtained by imaging a printed wiring board to be inspected by the apparatus of FIG. 1;

FIG. 4 is an explanatory diagram showing a case where the inspection area in FIG. 3 is quantified 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 during soldering and their binarized data.

FIG. 7 is a timing chart showing an exclusive OR of the binarized data and the reference data in FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Illumination part 2 LED 3 Imaging part 4 Chip component 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

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01B 11/24 G01N 21/88 H05K 3/34

Claims (1)

(57) [Claims] 1. A method according to claim 1, Illuminate and image the soldered printed circuit board from above, b. Binarizing the luminance of the pixels in the predetermined inspection area to obtain binarized line data; c. The exclusive OR calculated by comparison with a preset reference value consisting of one of the 0 value or a 1 value over all the binarized line data said predetermined inspection area, d. When the obtained exclusive OR contains one value, it is determined that the soldering is defective.