JPH01219548A - Substrate inspecting device - Google Patents

Abstract

PURPOSE:To inspect a soldering part at a high speed with simple circuit constitution while the measurement accuracy is held constant by picking up an image of components of a printed board, extracting brightness information on the periphery of the soldering part, and finding a frequency distribution of brightness. CONSTITUTION:The soldered components 2 are lighted by a ring lighting equipment 4 and their image is picked up by a CCD camera 5, whose video signal is A/D-converted 6 and stored 7. Only an image of the periphery of the soldering part 3 is extracted 8 from a memory 7 by using data for the package arrangement of the components 2 according to the positions or brightness values, etc., within a constant range. The images (brightness value) are inputted to a brightness frequency calculating circuit 9 in order and classified by brightness level to find the frequency distribution of the brightness values, thereby outputting the frequencies of the respective grades. An integral frequency calculating circuit 11 integrates the frequencies of the respective grades of brightness in order to find an integral frequency distribution. This integral frequency value is compared with a reference value stored in a memory 13 by a comparator 13 to find the difference. It is decided 15 whether or not the soldering part 3 is normal from whether or not the output value (subtraction result) of the comparator 14 is within variance at the time of the setting of the reference value of a normal part.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a board inspection device for inspecting components soldered on a printed circuit board.

BACKGROUND OF THE INVENTION Conventionally, inspection of parts soldered on a printed circuit board to determine whether the parts are good or bad has relied on visual inspection by humans. That is, as shown in FIG. 4, regarding a component 42 soldered on a printed circuit board 41, an operator 43 determines whether the soldering is good or not based on the brightness of a portion 44 and its vicinity 46. I was checking for defects. In FIG. 4, (,) shows a top view of the soldered portion, and (b) shows a cross-sectional view of the same.

Problems to be Solved by the Invention However, as products become smaller and lighter, components on printed circuit boards are also becoming smaller and more densely packaged. Under these circumstances, it goes without saying that Iruma has to maintain high inspection accuracy while inspecting the soldering condition of very small parts, and that it is a difficult task to continuously inspect for a long time. There are limits to visual inspection as well, such as a decline in performance.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention includes an imaging means for taking an image of a component illuminated by an illumination means, and after A/D converting a luminance signal from the imaging means, storing this luminance information. a soldering part image extraction circuit for extracting luminance information near the soldered part; a luminance frequency calculation circuit for calculating the luminance frequency distribution; It consists of a discrimination circuit.

Function The present invention extracts brightness information near the soldered part and automatically determines whether the soldered part is good or bad based on the frequency distribution of the brightness, thereby eliminating the need for visual inspection of the soldered part. This saves labor and performs inspections at high speed without reducing accuracy.

Embodiment FIG. 1 is a block diagram showing a first embodiment of the substrate inspection apparatus of the present invention. In FIG. 1, 1 is a printed circuit board, 2 is a component soldered to the printed circuit board 1, 3 is the soldering part, 4 is a ring illuminator that illuminates the component 2, and 6 is a video camera that images the component 2. Camera (COD camera)
, 6 is the image (luminance) of part 2 captured by video camera 6
An A/D converter that converts the signal into 8-bit digital image information; 7 is an image memory that stores the image information converted by the A/D converter 6; 8 is a component 2 from the image memory 7;
0 is a solder part image extraction circuit that extracts brightness information in the vicinity of the soldered part 3; 9 is a brightness frequency calculation circuit that calculates a frequency distribution using the extracted brightness information in the vicinity of the soldered part. Reference numeral 10 denotes a defective determination circuit that determines whether the soldered portion 3 is good or bad based on the brightness frequency distribution output from the brightness frequency calculation circuit 9, and 11 is a cumulative frequency calculation circuit that calculates the cumulative frequency from the brightness frequency distribution. , 12 is a cumulative frequency comparison circuit, 13 is a memory in which a reference value for quality judgment is set, 14 is a comparator, 16
1 is a solder defect determination circuit, and 16 is a determination display circuit.

The operation will be explained below.

A component 2 soldered onto a printed circuit board 1 by a soldering part 3 is illuminated by a ring illuminator 4, and an image of the illuminated component 2 is captured by a CCD camera 6.

At this time, the distance between the ring light and the parts is approximately sown, CO
The field of view of D camera '6 was set to approximately 30n angle. The relationship between the brightness of the ring illumination and the aperture of the camera was set so that the brightest point on the screen did not exceed the maximum sensitivity of the CCD camera 6.

The video signal captured by the CCD camera 6 is converted into an 8-bit k/
Digital images in the range of 0 to 265 with D converter e (
brightness value) and stored in the image memory 7. From the stored images, use data for component mounting and placement (for example, mount data for two-dimensional placement from a chip mounter) to position only the image (30 x 30 pixels) near the soldering area or within a certain range. The solder part image extraction circuit 8 extracts the solder part image from the brightness value and the like. The extracted images (brightness values) are sequentially input to the brightness frequency calculation circuit 9, where they are classified into 64 classes based on brightness level, and the frequency distribution of brightness values near the soldered area is determined.
Output the frequency of each class.

From the state of the frequency distribution output from the brightness frequency calculation circuit 9,
The defect determination circuit 1o determines whether the soldered part is good or bad, and the judgment display circuit 15 displays whether the soldered part is good or bad, and the soldered part image extraction circuit 8 again extracts an image of the next inspection component.
Continue inspection and judgment.

Among the above operations, the defect determination circuit 10 will be explained in more detail. The defect determination circuit 10 includes a cumulative frequency calculation circuit 1
1 and a cumulative frequency comparison circuit 12. The cumulative frequency calculation circuit 11 sequentially cumulatively adds the frequencies of each luminance class output from the luminance frequency calculation circuit 9 to obtain a cumulative frequency distribution. A cumulative frequency comparison circuit 12 compares the cumulative frequency distribution with a standard value for determining pass/fail and determines whether the product is good or bad.

Next, the output results from the cumulative frequency calculating circuit 11 are shown in FIG. In Fig. 2, the horizontal axis is classified into 64 classes,
The vertical axis represents the cumulative frequency of brightness output corresponding to the class. This cumulative frequency calculation circuit 11 determines whether the soldering part is good or not.
Characteristics of defects can be clearly distinguished. That is, the second
As shown in the figure, if the image is of the back of the soldered part,
Since there are many parts with high brightness, the cumulative frequency distribution is as shown by the solid line 21. However, in the case of an image of a defective soldered part, there are many parts with dark brightness, so that the cumulative frequency distribution is as shown by the broken line 2o. In this way, it is possible to distinguish between good and bad soldered parts based on the state of the cumulative frequency distribution.

Based on the output of the cumulative frequency calculating circuit 11, the cumulative frequency comparing circuit 12 determines whether the soldered portion is good or bad. Cumulative frequency comparison circuit 1
In the case of the present embodiment, the comparator 14 first compares and subtracts the cumulative frequency value of each class outputted from the cumulative frequency calculation circuit 11 with a reference value set in the memory 13. Note that the reference value is set in advance for each class as a cumulative luminance value for an image of the back side of the soldered portion serving as the reference.

Then, in the solder defect determination circuit 16, the output value of the comparator 14 (
It is determined whether the soldered part is good or bad based on whether the subtraction result) is within the variation when setting the reference value on the back side. In this way, the luminance frequency calculation circuit 9, the cumulative frequency calculation circuit 11, and the cumulative frequency comparison circuit 12 clearly distinguish the shape of the luminance cumulative frequency distribution between good and defective as shown in FIG. /Defects can be determined. Although the comparison and subtraction of the cumulative frequency values in the comparator 14 may be performed for all classes of the frequency distribution, in order to shorten the calculation time, As shown in FIG.
It is preferable to compare in about 10 to 20 classes from the viewpoint of inspection speed and inspection accuracy.

Furthermore, the number of classes into which luminance is classified does not limit the present invention in any way, but from the viewpoint of inspection speed and inspection accuracy,
The number of classes is preferably about 10 to 200.

As described above, in this embodiment, the quality/deficiency inspection of soldered parts, which had previously relied on visual inspection, can be performed using the illuminator 4 and the video camera 6.
With the configuration of the brightness frequency calculation circuit 9 and the like, it can be executed automatically, and the inspection can be continued for a long time and at high speed with constant accuracy.

Note that the ring illuminator 4 and CCD camera 5 used in this embodiment do not limit the present invention in any way, and other illuminators or video cameras may be used.

In the defect determination circuit 1o, the frequency distribution output from the brightness frequency calculation circuit 9 is exchanged with a cumulative frequency distribution in the cumulative frequency calculation circuit 11 and compared with a reference value. The shape of the frequency distribution may be directly compared with a reference value, and the determination of good/bad can be made in the same way.

A second embodiment of the present invention will be described below.

FIG. 3 shows a block configuration of a board inspection apparatus according to a second embodiment of the present invention. In FIG. 3, the cumulative frequency comparison circuit 12 of the defect determination circuit 1o is composed of a cumulative frequency addition circuit 31, a reference value memory 32, a comparator 33, and a solder defect determination circuit 34. Since the configuration is the same as that shown in FIG. 1, the same reference numerals as in FIG. 1 are given and the explanation will be omitted, and the operation of the defect determination circuit 10 will be explained below. First, the frequency distribution of the luminance information of the image of the soldered portion outputted from the luminance frequency calculation circuit 9 is converted into a cumulative frequency distribution by the cumulative frequency calculation circuit 11a. Based on the shape of the converted cumulative frequency distribution, the cumulative frequency comparison circuit 12 determines whether it is good or bad.

In the cumulative frequency comparison circuit 12, first, the cumulative frequency calculation circuit 11
A cumulative frequency adding circuit 3 outputs the cumulative frequency of each class from a.
1 adds them all and outputs the total value.

A comparator 33 compares and subtracts the total value from a reference value set in the memory 32. Note that the reference value is set in advance as an average value obtained by adding and totaling the cumulative frequencies of brightness for images of the back side of a plurality of soldered parts.

Finally, the solder defect determination circuit 34 determines whether the soldered portion is good or defective based on whether the output value (subtraction result) of the comparator 33 falls within the variation when setting the reference value on the back side. In this way, the cumulative frequency addition circuit 31 calculates the diagonal area (O
A value corresponding to the area of area BC) is calculated, and in the case of a defective part, a value equivalent to the area of area 0ABO is calculated and output.

As described above, in this embodiment, the cumulative frequency addition circuit 31
By providing this, the difference in shape due to good/bad frequency distribution can be represented by a numerical value corresponding to the area of the cumulative frequency distribution, and it is possible to more clearly distinguish between good and bad, which is similar to the first embodiment. Get the effect.

Effects of the Invention As described above, according to the present invention, an illumination means, an imaging means, a means for A/D converting and storing a luminance signal from the imaging means, a solder part image extraction circuit, and a luminance frequency calculation circuit are provided. and a defect determination circuit. With a relatively simple circuit configuration, soldered parts can be inspected at high speed and with constant measurement accuracy without relying on human visual inspection, resulting in significant automation of inspection and improved work efficiency. effect can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a board inspection apparatus according to the first embodiment of the present invention, FIG. 2 is a diagram showing calculation results of the cumulative frequency calculation circuit of FIG. 1, and FIG. FIG. 4(a) is a block diagram of the circuit board inspection apparatus in the embodiment of the present invention, and FIG. 4(b) is a top view of the soldered part in the conventional visual inspection.
) is a longitudinal sectional view of the same. 1... Printed circuit board, 2... Parts, 3... Soldering part,
4...Illuminator, 6...CCD camera, 6...A/D converter, 7...Image memory, 8...Solder part image extraction circuit, 9...Brightness frequency calculation circuit, 10...Failure determination Circuit, 11. Cumulative frequency calculation circuit, 12.. Cumulative frequency comparison circuit, 13.. Memory, 14.. Comparator, 31.. Cumulative frequency addition circuit. Name of agent: Patent attorney Toshio Nakao Haga 1st person
1 Figure 2 Figure 3

Claims (6)

[Claims] (1) An illumination means for illuminating components placed and soldered on a printed circuit board, an imaging means for imaging the components illuminated by the illumination means, and quantization of an image signal output from the imaging means. an A/D converter; storage means for storing image information converted by the A/D converter;
a solder part image extraction circuit that extracts brightness information near the soldered part of the component from the image information; a brightness frequency calculation circuit that calculates a frequency distribution of the extracted brightness information in the vicinity of the soldered part; A board inspection device comprising: a defect determination circuit that determines whether the soldered portion is good or defective based on the frequency distribution of brightness output from the frequency calculation circuit. (2) A defect determination circuit includes a comparator that compares the brightness frequency output from the brightness frequency calculation circuit with a standard value for determining pass/fail, and determines whether the soldered part is good or bad based on the output of the comparator. 2. The board inspection apparatus according to claim 1, further comprising a solder defect determination circuit. (3) a cumulative frequency calculation circuit in which the defect determination circuit calculates a cumulative distribution of brightness frequencies output from the brightness frequency calculation circuit;
2. The board inspection apparatus according to claim 1, further comprising a cumulative frequency comparison circuit that determines whether a soldered portion is good or bad based on the cumulative frequency distribution of luminance output from the cumulative frequency calculation circuit. (4) The cumulative frequency comparison circuit includes a comparator that compares the cumulative luminance value output from the cumulative frequency calculation circuit with a reference value preset for pass/fail determination, and a solder from the output of the comparator. 4. The board inspection apparatus according to claim 3, further comprising a solder defect determination circuit for determining whether the attached portion is good or defective. (5) a cumulative frequency addition circuit in which the cumulative frequency comparison circuit adds the cumulative frequency of luminance output from the cumulative frequency calculation circuit;
It is comprised of a comparator that compares the addition result, which is the output of the cumulative frequency addition circuit, with a reference value for pass/fail judgment, and a solder defect judgment circuit that judges whether the soldered part is good or bad from the output of the comparator. 4. The board inspection apparatus according to claim 3, wherein: (6) The board inspection apparatus according to any one of claims 2, 4, and 6, wherein the reference value for quality determination is calculated and set in advance using brightness information in the vicinity of the non-defective soldered part.