JPH02157610A - Packaging state inspecting method - Google Patents

Abstract

PURPOSE:To inspect the packaging state of a component with high accuracy without being affected by the wiring pattern of a wiring board where the component is packaged by projecting such light that the wiring pattern on the wiring board is illuminated higher than the density level of a part to be inspected and a shadow formed by main illustration light is not erased. CONSTITUTION:The circuit board 1 receives light slantingly from above by 1st and 2nd lighting means 3a and 4a, an image pickup device 2 picks up an image, and only image data on the picked-up image which reaches certain density level is stored in an image memory 7a. Then the lighting means 3b and 4b project light on the circuit board 1 from symmetrical positions and image data is stored in the image memory 7b. At this time, when the images in the image memories 7a and 7b are picked up, the light which makes the wiring pattern 13 on the circuit board 1 illuminate with higher than the specific density level and does not erase the shadow formed by the main illumination light is projected. Thus, the density difference between both images which are picked up is computed to easily remove the wiring pattern and the packaging state of the component is inspected with high accuracy.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a method called "oblique light shading method" used in a component mounting state inspection device for inspecting the state of components mounted on a board. This invention relates to an improved mounting state inspection method.

(Prior Art) As a mounting state inspection method used in a conventional component mounting state inspection apparatus for inspecting the state of components mounted on a board, a method called "oblique light shading method" is used.

This "oblique light shading method" irradiates light from diagonally above the board to be inspected to create a shadow on the components mounted on the board to be inspected.
By taking an image of the board to be inspected from above, an image including shadows of components is obtained. From this image, the first image is obtained by modulating the density level of a portion other than that required for the inspection so as not to affect the inspection.

The illumination is performed so that a shadow is generated from the opposite direction to the board to be inspected from the first image obtained here, that is, the board to be inspected is illuminated from a position relative to when the first image is captured. By taking an image of the board to be inspected from above, an image including shadows of components is obtained. This image is modulated in the same way as the first image to obtain a second image.

An image of the density difference between the first image and the second image is calculated. At this time, since the first image and the second image are modulated so as not to affect the inspection except for the density level of the part necessary for the inspection, the image of the part other than the inspection target is calculated as a density difference image. It will be removed in due course.

In this way, the shadow of the mounted component is detected from the density difference image in which the image of the portion other than the part to be inspected is removed, and the mounting state of the component on the board to be inspected is inspected from the state of this shadow.

(Problems to be Solved by the Invention) In the above-mentioned "oblique light shadow method", it is difficult to separate the noise detected on the wiring pattern provided on the board to be inspected from the shadow of the mounted component. Ta. Therefore, noise in this wiring pattern can cause problems such as incorrectly detecting normally mounted parts as rotated and mounted, or conversely determining that parts mounted in an abnormal state are normal. was occurring.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inspection method capable of highly accurate inspection of the mounting state of a component, which is not affected by the wiring pattern of a board on which the component is mounted.

[Structure of the Invention] (Means for Solving the Problems) Light is irradiated from diagonally above a component mounted on a board to be inspected, a first image is captured from above the board to be inspected, and the captured image is A first image storage step in which a portion having a density level other than that of the portion to be inspected is modulated and stored, and a position where light is irradiated onto the substrate to be inspected in this first image storage step irradiate the board to be inspected with light from a symmetrical position, take a second image from above the board to be inspected, and use the captured image to detect a portion having a density level outside the density level range of the part to be inspected. a second image storage step of modulating and storing; the first image storage step and the second image storage step;
and an inspection step of calculating the difference in density level between the two images stored by the image storage step and detecting the shadow of the mounted component from this difference image to inspect the mounting state of the component on the board to be inspected. In the mounting state inspection method, the wiring pattern provided on the substrate to be inspected is illuminated at a predetermined density level or higher during image capturing in the first image storage step and the second image storage step. , and a mounting state inspection method that irradiates light that does not erase shadows caused by the light emitted by the main illumination.

(Function) Noise on the wiring pattern of the board becomes a problem when inspecting the mounting state of high-precision components. Therefore, a light is placed at a position where the entire wiring pattern is illuminated at a predetermined concentration or higher, noise generation is eliminated, and then the concentration level of the portion other than the portion to be inspected is modulated.

Further, the problem can be solved by calculating the density difference image between the modulated first and second images and removing the wiring pattern when binarizing the image.

Therefore, we decided to illuminate the wiring pattern provided on the board to be inspected at a level higher than the density level of the part to be inspected, and to irradiate the wiring pattern with light that would not erase the shadows caused by the light emitted by the main illumination.

In fact, such a thing is possible, but when we investigate the cause of noise in the wiring pattern, we find that the entire surface of the wiring pattern is polished so that the solder joins well with the wiring pattern, and fine particles are removed. It was found that the irregularities of the lever tended to cause noise. If these fine irregularities are not added to the wiring pattern, the density of the wiring pattern will be higher than the density level of the area to be inspected even under normal lighting, and it will be removed when calculating the density difference image. It is.

However, in reality, because of these fine irregularities, the irradiated light is diffused and the density level is lowered to within the density level of the area to be inspected.

Therefore, this time, we reversely utilized the fine irregularities of this wiring pattern to eliminate the shadows caused by the main illumination from the direction where the wiring pattern is likely to reflect light toward the imaging device installed above the board to be inspected. I decided to let in a certain amount of light.

First, regarding the direction of illumination, the wiring pattern is polished in a constant direction with respect to the entire board to be inspected.

From a direction perpendicular to this polishing direction to the substrate to be inspected at a low angle (the angle of conventional illumination to create a shadow is about 45 degrees, this illumination If the light is incident at an angle that is less than half the illumination angle of normal illumination, the light will be specularly reflected in the upward direction where the imaging means is provided. The wiring pattern can be easily removed by calculating the difference in density between the first image and the second image captured while irradiating with such illumination.

However, even if the light is actually illuminated from such a direction, if the shadows generated on the part by the conventional illumination process are erased, calculating and calculating the density difference image will have no effect. Therefore, the light emitted from this direction must be weak enough not to erase the shadows created on the parts by the conventional illumination process.

This varies depending on the wavelength of conventional illumination and the distance from the substrate to be inspected, but it is sufficient if the brightness of the light irradiated onto the substrate to be inspected is about one-tenth that of normal illumination.

(Example) An example of a component mounting state inspection apparatus using the method of the present invention will be described below.

FIG. 1 is a schematic diagram of the component mounting state inspection apparatus of this embodiment. An imaging device (2), first illumination means (3a), (3b), and second illumination means (4a), (4b) are provided above a circuit board (1) that is a board to be inspected. .

The first illumination means (3a), (3b) are arranged at an angle of 45 degrees with respect to the vertical direction of the circuit board (1) as shown in FIG. The circuit board (1) is arranged so that light is incident on the circuit board (1) at an angle of 45 degrees. On the other hand, the second illumination means (4a),
(4b) is at an angle of 20 degrees perpendicular to the circuit board (1) as shown in Figure 2, and further in the polishing direction of the circuit board (1) to the left and right as shown in Figure 3. It is arranged so that light is incident at an angle perpendicular to arrow A.

The output of this imaging device (2) is sequentially converted to an A/D conversion circuit (5)
, image memory (7a), (7) via the gradation conversion circuit (6).
b) connected so as to be stored. This image memory (
A subtraction circuit (8) is connected so that the data can be read from each of 7a) and (7b), and the calculation result of the binarization circuit (9) is connected so that the calculation result can be sent to the binarization circuit (9). is connected to the arithmetic control circuit (10) so that it can be transmitted. The arithmetic control circuit (lO) is an A/D conversion circuit (5),
A subtraction circuit (8), a lighting switching circuit (11), and a display device (12) are connected so as to be controllable. Note that the lighting switching circuit (11) is connected to the first lighting means (3a) and (3b).
and the second illumination means (4a) and (4b) are connected so that lighting can be switched, and the display device (12) displays data sent to the arithmetic control circuit (10) as an image. A connection has been made.

Next, the present invention will be explained in detail using the apparatus of this embodiment.

When the circuit board (1) on which the circuit components are mounted is placed, the arithmetic control circuit (10) operates the lighting switching circuit (11) to switch the first and second lighting means (3a) and (
4a) and sends a command to the imaging device (2) to take an image of the circuit board (1). The image captured by the imaging device (2) is sent to the A/D conversion circuit (5), digitized, and sent to the tone conversion circuit (6).The tone conversion circuit (6) displays the image on the screen for inspection. In order to extract only the necessary parts, upper and lower limits are set for the density level of the image, and only image data with density levels between these are extracted.This is based on the input image density as shown in the graph of Figure 5. All parts whose density level is higher than the upper limit a are output as density a, and all parts whose density is lower than the lower limit of the input image density level are outputted as density.The thus output image data is stored in the image memory (7a ). A part of the image including the part to be inspected of this image data is shown in FIG. This prevents its occurrence.

Subsequently, the arithmetic control unit (10) operates the illumination switching circuit (11), and the other side (3b) of the first illumination means,
(4b) is turned on, and this image data is stored in the image memory (7b) in the same manner as described above. A part of the image at this time is shown in FIG. 4(b).

The subtraction circuit (8) calls the two image data stored in the image memories (7a) and (7b) in this way, and calculates image data of the density difference between the two image data.

At this time, the density difference image is such that when the first and second images are irradiated with light from the second illumination means (4a) and (4b) onto the wiring pattern, it is specularly reflected in the direction of the imaging device. By doing so, the concentration of the wiring pattern (13) becomes higher than b. Therefore, the difference between these two images is calculated via a modulation circuit (6). The image data at this time is shown in Figure 4 (c
).

In this way, the calculation result of the subtraction circuit (8) is transferred to the binarization circuit (9).
), and this binarization circuit (9) binarizes the density between the shadow and the circuit board at an intermediate level of I/bevel.In this way, the wiring pattern (13) that is brighter than the shadow is easily created by setting the binarization level. This allows only the shadows of the components mounted on the circuit board (1) to be recognized.

The arithmetic and control circuit (io) which has received the binarized density difference image data inspects and recognizes the presence or absence of mounted components, positional deviations, inclinations, incorrect mounting of components, etc. from the received image data. This recognition result is displayed on the display device (12).

Note that in this example, the second illumination was set in a direction perpendicular to the polishing direction of the substrate, but this is because the polishing direction was two-dimensional, and even if the polishing direction of the substrate was undefined, the main It is only necessary to illuminate the wiring pattern from a position where the wiring pattern is reflected toward the imaging device at a predetermined concentration or higher, with light that does not erase the shadows caused by the illumination on the mounted components on the board to be inspected.

[Effects of the Invention] As described above, when the present invention is used to inspect the mounting state of components mounted on a board to be inspected, it is possible to remove noise on the wiring pattern, which has been an obstacle to conventional inspections, and to perform stable inspection. Inspection becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an embodiment of a component mounting state inspection apparatus using the method of the present invention, FIGS. Fourth
FIG. 5 and FIG. 5 are explanatory diagrams for showing the same effect. 9...Binarization circuit, 11...Lighting switching circuit, 13...Wiring pattern. 10... Arithmetic control circuit. 12...Display device,

Claims (1)

[Claims] Light is irradiated from diagonally above a component mounted on a board to be inspected, a first image is taken from above the board to be inspected, and the part that has a density level other than the density level of the part to be inspected is determined from the taken image. a first image storage step of modulating and storing the image; and a first image storage step of irradiating light onto the substrate to be inspected from a position symmetrical to the position where the substrate to be inspected was irradiated with light in this first image storage step. a second image storage step of capturing a second image from above the substrate to be inspected, modulating and storing a portion having a density level outside the density level range of the inspection target portion from the captured image; 1 image storage process and 2nd image storage process
and an inspection step of calculating the difference in density level between the two images stored by the image storage step and detecting the shadow of the mounted component from this difference image to inspect the mounting state of the component on the board to be inspected. In the mounting state inspection method, the wiring pattern provided on the substrate to be inspected is illuminated at a predetermined density level or higher during image capturing in the first image storage step and the second image storage step. , and a method for inspecting a mounting state, characterized by irradiating light that does not erase shadows caused by light emitted by main illumination.