JPH06331564A - Inspection apparatus of solder bonded part - Google Patents

Abstract

PURPOSE:To realize the inspection apparatus, of a solder bonded part, which can inspect the solder bonded part of every shape by installing an illumination means by which the brightness of reflected light is changed according to the inclination angle of a reflecting position. CONSTITUTION:A ring-shaped light source 41 and a diffusing plate 42 are combined, and an illumination means 4 is constituted. In the illumination means 4, irradiation light from the ring-shaped light source 41 is incident from the edge of the diffusing plate 42, the incident light is totally reflected and diffusion-reflected on the inner face of the diffusing plate 42, and the brightness of light radiated to the outside from the diffusing plate 42 is attenuated along the length direction of the diffusing plate. A solder bonded part is irradiated with light radiated from the inner circumferential face of the diffusing plate 42 out of light advancing in this manner. At this time, the brightness of reflected light which is reflected by the solder bonded part and which advances to the length direction of the diffusing plate is changed continuously according to the inclination angle of a reflecting position. When the image of the reflected light is picked up by an image sensing means 5, light and shade information on a picked-up image is used as information on the inclination angle. Consequently, the three-dimensional shape of the solder bonded part is detected on the basis of the light and shade information, and it is judged whether a defect exists or not in the solder bonded part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder joint inspection device for detecting whether or not a solder joint is defective by detecting the external shape of the solder joint formed on a printed circuit board. Is.

[0002]

2. Description of the Related Art Some conventional solder joint inspection devices use an illuminating device. That is, a plurality of illuminations with different irradiation angles are provided, the combination of the illuminations that are turned on is changed according to the shape of the solder joint that is the surface to be inspected, or each illumination is turned on in a time-sharing manner, and in each lighting state. An image of the solder joint portion displayed was photographed, and the three-dimensional shape of the solder joint portion was detected from the photographed image. And
Based on the detected three-dimensional shape, it is determined whether or not there is a defect in the solder joint. Such an inspection apparatus is disclosed in, for example, Japanese Patent Application Laid-Open No. 61-293657 and Japanese Patent Application Laid-Open No. 1-21954.
No. 7, Japanese Patent Laid-Open No. 1-282410, No. 2-
No. 67949, Japanese Patent Laid-Open No. 3-103706, and the like.

However, in the case of a relatively irregular shape such as a solder joint, an infinite number of combinations of lightings are required. Therefore, in the above-mentioned conventional example, the solder joint having a limited shape is used. Only applicable.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and is provided with an illumination means in which the brightness of reflected light continuously changes according to the tilt angle of the reflection position. Accordingly, it is an object of the present invention to realize a solder joint inspection device capable of inspecting solder joints of any shape.

[0005]

SUMMARY OF THE INVENTION The present invention is a solder joint inspection device for visually inspecting a solder joint formed on a printed circuit board for defects. The solder joint inspection device has a ring-shaped light source and a diffusion plate. The diffuser plate has a cylindrical shape and is arranged inside the ring-shaped light source. The light emitted from the ring-shaped light source is incident from the end surface of the diffuser plate, and the incident light is totally reflected on the inner surface of the diffuser plate. And diffusely reflect the light emitted from the diffuser plate to the outside to attenuate the brightness along the length direction of the diffuser plate, irradiate the light emitted from the inner peripheral surface of the diffuser plate to the solder joint portion, and solder. Lighting means for continuously changing the brightness of the reflected light reflected by the joint portion and traveling in the length direction of the diffuser plate according to the inclination angle of the reflection position, and solder receiving the reflected light traveling in the length direction of the diffuser plate An image pickup means for picking up a reflected light image of the joint part and an image picked up by this image pickup means Detecting a three-dimensional shape of the solder joint,
A solder joint inspection device, comprising: a determination unit that determines the presence or absence of a defect in the solder joint based on the detected shape.

[0006]

In the present invention as described above, the illumination means is constructed by combining the ring type light source and the diffusion plate. In this illumination means, the light emitted from the ring-shaped light source is incident from the end surface of the diffusion plate,
The incident light is totally and diffusely reflected on the inner surface of the diffusion plate,
The brightness of the light emitted from the diffusion plate to the outside is attenuated along the length direction of the diffusion plate. Of the light traveling in this way, the light emitted from the inner peripheral surface of the diffusion plate is applied to the solder joint. At this time, the brightness of the reflected light reflected by the solder joint portion and traveling in the length direction of the diffuser plate continuously changes according to the inclination angle of the reflection position. When this reflected light image is picked up by the image pickup means, the gradation information of the picked-up image becomes the tilt angle information. Therefore, the three-dimensional shape of the solder joint is detected based on the grayscale information, and the presence or absence of a defect in the solder joint is determined.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. Figure 1
FIG. 1 is a schematic configuration diagram of an embodiment of the present invention. In FIG. 1, 1 is a printed circuit board, and 2 is a mounted component mounted on the printed circuit board 1. The mounting component 2 is bonded to the printed circuit board 1 by soldering, and the solder bonding portion is an inspection target. Reference numeral 3 denotes an XY drive table on which the printed board 1 is placed and which moves and positions the printed board 1 in a two-dimensional direction along the board surface. Reference numeral 4 denotes an illuminating unit arranged above the printed circuit board 1, which includes a ring-shaped light source 41 and a diffusion plate 42.
Consists of. The diffusion plate 42 has a cylindrical shape and is arranged inside the ring-shaped light source 41. Ring light source 4
1 and the central axis of the diffuser plate 42 coincide with each other. The light from the ring-shaped light source 41 enters the diffusion plate 42, is reflected in the diffusion plate 42, and then is emitted to the outside. The emitted light is applied to the solder joint. Reference numeral 5 denotes a camera as an image pickup means, which is arranged above the illumination means 4 and picks up a reflected light image of the inspection target. An inspection processing system control unit 6 detects a three-dimensional shape of the solder joint from the image captured by the camera 5,
The presence or absence of a defect in the solder joint is determined from the detected three-dimensional shape. The inspection processing control unit 6 includes an A / D converter 61,
The image memory 62, the image processing unit 63, and the image determination unit 64 are provided, and the presence or absence of defects is determined using these. The determination unit referred to in the claims corresponds to the inspection processing control unit 6. 7
Is a drive system control section, which is an illumination control section 71 for controlling the drive of the illumination means 4 and X of the XY drive table.
X-axis drive unit 72 for controlling movement in the Y direction and the Y direction, respectively
And a Y-axis drive unit 73.

FIG. 2 and FIG. 3 are views showing a concrete configuration example of the apparatus of FIG. FIG. 3 is an enlarged view of an X portion surrounded by a chain double-dashed line in FIG. 2 and 3, the same parts as those in FIG. 1 are designated by the same reference numerals. Hereinafter, the same applies in the drawings. Figure 2
3, an optical fiber 412 is drawn in the ring light guide 411, and light from a light source (not shown) such as a halogen lamp is guided by the optical fiber 412 and transmitted to the ring portion of the ring-shaped light source 41. . In the ring portion, the light emitting surface of the optical fiber 412 is arranged so as to face the center. Optical fibers having the light emitting surface as the center are arranged along the circumferential direction of the ring. The diffusion plate 42 is made of, for example, an acrylic pipe, and chamfers the inner edge of the end face to form a primary diffusion surface 421. The light emitted from the light emitting surface of the optical fiber 412 is the primary diffusion surface 421.
The ring-shaped light source 4 so that it hits the inside of the diffusion plate 42.
The first ring portion is inscribed in the ring light guide 411. The central axes of the ring-shaped light source 41, the diffusion plate 42 and the camera 5 coincide with each other, and the substrate surface of the printed circuit board 1 is orthogonal to these central axes.

The operation of the apparatus thus configured will be described. First, the operation will be described with reference to FIG. The positions of the illumination means 4 and the camera 5 are fixed. By moving the XY drive table 3 under the control of the drive system control unit 7, the printed circuit board 1 is positioned so that the solder joint to be inspected is directly below the lighting unit 4. After the positioning is completed, the camera 5 captures an image of the solder joint, the inspection processing control unit 6 recognizes the three-dimensional shape of the solder joint from the captured image, and determines whether there is a defect in the solder joint based on a predetermined condition.

The detection principle that characterizes the present invention will now be described. 4 to 6 are explanatory diagrams of the detection principle.
In FIG. 4, reference numeral 8 denotes a cylindrical surface illumination, and the diffusion plate 4 of the present invention.
Equivalent to 2. Reference numeral 9 denotes a specular spherical surface, which corresponds to the solder joint surface 11 of the present invention. Light whose radiation intensity continuously changes in the height direction of the cylindrical surface as shown in FIG. 5 is emitted from the cylindrical illumination 8 to the specular spherical surface 9. At this time,
Of the light reflected by the specular spherical surface 9, the light traveling in the height direction of the cylindrical surface takes a different optical path depending on the irradiation angle of the irradiation light that is the source of the reflected light. This is because the reflected light traveling in the height direction of the cylindrical surface has a different reflection position on the spherical surface 9 if the irradiation angle of the irradiation light that is the basis of the reflection light is different. The inclination angle Θ shown in the figure is an angle formed by the tangent line of the spherical surface and the horizontal line at the reflection position. Each reflected light traveling in the height direction of the cylindrical surface has a different inclination angle Θ of the reflection position. Therefore, when the reflected light traveling in the height direction of the cylindrical surface is observed right above the specular spherical surface 9, the brightness of the light flux has a value corresponding to the inclination angle Θ. The relationship between the luminance Φ of the light flux and the inclination angle Θ is as shown in FIG. 6, for example.

The operation of the present invention to which such a detection principle is applied will be described with reference to FIGS. 2 and 3. The light emitted from the optical fiber 412 in the ring light guide 411 enters the diffusion plate 42 inscribed therein and is further irradiated on the primary diffusion surface 421. The light reflected by the diffusing surface is diffused and reflected by the secondary diffusing surface 422 using the diffusing plate 42 as a medium, and part of the light is emitted from the boundary surface between the inner surface and the outer surface of the diffusing plate 42 to the outer world. Here, the light that has not been emitted to the outside world is totally reflected inside the diffusion plate 42, diffused and reflected again on the secondary diffusion surface 422, and a part thereof is emitted to the outside world. By repeating this, the brightness of the light emitted to the outside world is continuously attenuated as the distance from the light incident position of the diffusion plate 42 increases. Thereby, from the inner peripheral surface of the diffusion plate 42, light having different irradiation angles and intensities is emitted along the length direction of the diffusion plate 42. In FIG. 2, the light emitted from the optical path A to the solder joint portion 11 has an inclination angle α.
The light reflected from the optical path B is reflected vertically upward on the slope of the above, and the light emitted from the optical path B is reflected vertically upward on the slope of the inclination angle β. Since the reflection position of each light is different, the optical path of each reflected light is different. That is, the reflected light traveling vertically upward has a brightness corresponding to the inclination angle of the reflection position. Therefore, the brightness information of the reflected light is the tilt angle information. By capturing such reflected light with the camera 5, the three-dimensional shape of the solder joint portion 11 is detected.

Although the embodiments have been described mainly for the case where the inspection is performed after soldering the surface mount components by reflow, the same hardware configuration is used and only the software for the image pickup determination is prepared exclusively. ,
It can also be applied to inspection of the application state of cream solder, visual inspection of flow solder for discrete parts, etc.
In the inspection of the application state of the cream solder, spherical solder particles are targeted, and in the visual inspection of the flow solder, the fillet portion of the flow solder is targeted, and the feature recognition is efficiently performed from the grayscale image showing the three-dimensional shape. be able to. Also, the captured image with contrast corresponding to the three-dimensional shape,
Since feature extraction is easy for human vision, it is also effective to use it as an illumination image pickup means for visual inspection of solder joints and the like.

[0013]

According to the present invention, the following effects can be obtained. By the illumination means which is a combination of a ring-shaped light source and a cylindrical diffusion plate, reflected light whose brightness continuously changes according to the angle of the three-dimensional inclined surface to be inspected can be obtained. In the captured image obtained by capturing this reflected light, the grayscale information becomes the angle information of the inclined surface. Therefore, by associating the grayscale information with the angle information, it becomes possible to recognize a three-dimensional solid shape even with two-dimensional information. Since the change in the brightness of the reflected light with respect to the inclination angle of the reflection position is continuous, it is possible to inspect solder joints of any shape. In the conventional example, multiple lights were turned on in a time-sharing manner,
In the present invention, time-divisional lighting is not required and one image capturing is sufficient. As a result, the present invention has a higher inspection speed than the conventional example. Further, the lighting state of the illumination of the present invention is one form, and control of the combination of lighting as in the conventional example is unnecessary. A glossy flux may be present on the surface of the printed circuit board. When irradiation light in a direction orthogonal to the substrate surface is applied to a printed circuit board having flux, the irradiation light is reflected by the flux and returns along a path in the direction opposite to the irradiation light. In the present invention, since the reflected light of the light that is obliquely applied to the image pickup surface is imaged, the reflected component of the flux is rarely mixed in the reflected light for image pickup. Therefore, when recognizing an image, it becomes difficult to be influenced by the disturbance due to the flux.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing a specific configuration example of the device of FIG.

FIG. 3 is a diagram showing a specific configuration example of the apparatus of FIG.

FIG. 4 is an explanatory diagram of a detection principle.

FIG. 5 is an explanatory diagram of a detection principle.

FIG. 6 is an explanatory diagram of a detection principle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printed circuit board 11 Solder joint part 2 Mounting component 4 Illumination means 41 Ring type light source 42 Diffusion plate 5 Camera 6 Inspection processing system control part

Claims (1)

[Claims] 1. A solder joint inspection device for visually inspecting a solder joint formed on a printed circuit board for defects, comprising a ring-shaped light source and a diffusion plate, wherein the diffusion plate has a cylindrical shape. It is arranged inside the ring-shaped light source, receives the light emitted from the ring-shaped light source from the end surface of the diffuser, and totally reflects and diffuse-reflects the light incident on the inner surface of the diffuser from the diffuser. The brightness of the light emitted to the outside is attenuated along the length direction of the diffusion plate, the light emitted from the inner peripheral surface of the diffusion plate is applied to the solder joint, and is reflected by the solder joint to be diffused. An illumination unit that continuously changes the brightness of the reflected light traveling in the length direction of the solder according to the tilt angle of the reflection position, and an image of the reflected light of the solder joint is received by receiving the reflected light traveling in the length direction of the diffuser plate. And the three-dimensional shape of the solder joint from the image captured by this imaging means. An apparatus for inspecting a solder joint, comprising: a determination unit that detects and detects the presence or absence of a defect in the solder joint based on the detected shape.