JPH03192800A - Component mounting recognition method for printed board - Google Patents

Abstract

PURPOSE:To realize an automatic mounting check through a simple lighting equipment, to reduce a product in cost, and to enable the mounting check device concerned to be easily maintained and controlled in quality by a method wherein the image of a board obliquely illuminated is picked up by a camera provided in a vertical direction, and the positional data of component electrodes are measured. CONSTITUTION:A board 10 is mounted on an X-Y table 20 and positioned so as to enable a check object to be located in the visual field of an image pick-up camera 40. In this case, the camera 40 is installed just above the board 10. The board 10 is obliquely illuminated by an oblique lighting device 30, the board is discriminated from the component electrode in the image data through a lightness difference between them basing on the light scattering characteristic difference between the board 10 and the component electrode, the positional data of the component electrode is measured, and a component is checked in mounting state. By this setup, an automatic mounting check of a component can be realized through a simple lighting equipment, a product can be reduced in cost, and the mounting check device concerned can be easily maintained and controlled in quality.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an inspection method that can be used for mounting inspection of components mounted on a printed circuit board.

<Conventional technology> In the manufacturing process of printed circuit boards, electronic components are mounted on the printed circuit board and soldered to form circuits. Misalignment may occur, resulting in a defective board.

In the past, in addition to human visual inspection of component mounting, automated mounting inspection methods included a light cutting method that irradiated a slit light from an oblique direction, and a method that irradiated the component with laser light and measured the amount of reflected light. .

<Problems to be Solved by the Invention> However, human visual inspection has problems such as reduced inspection accuracy due to fatigue, difficulty in quality control, and increased product costs due to labor costs.

In automatic inspection, optical cutting methods using slit light and methods using laser light have problems such as increased costs due to the use of expensive parts in the optical system, and difficult adjustments and maintenance due to the complicated mechanism. Ta.

The present invention was devised in view of the above circumstances, and enables automatic component mounting inspection using cylindrical lighting equipment without using the slit light or laser light, thereby reducing product costs and equipment efficiency. The objective is to provide a new method for recognizing component mounting on printed circuit boards that is easy to maintain and control quality and has high accuracy.

<Means for Solving the Problems> The inspection method according to the present invention is a method for recognizing the mounting state of components mounted on a printed circuit board, and is a method for recognizing the mounting state of components mounted on a printed circuit board, in which a board image illuminated from an oblique direction is displayed on the board surface. An image is captured by an imaging camera installed vertically, and the substrate and component electrodes on the imaged data are distinguished by differences in brightness based on differences in the diffusion characteristics of illumination light between the substrate and component electrodes, and position data of the component electrodes is measured. It is characterized by inspecting the mounting state of components.

<Operation> The substrate 10 is mounted on the XY table 20 and positioned so that the inspection target is within the field of view of the imaging camera 40. In this case, the imaging camera 40 is installed directly above the substrate 10.

The oblique illumination 30 performs oblique illumination on the substrate IO.

Based on the difference in the diffusion characteristics of illumination light between the substrate 10 and the component electrodes, the substrate and component electrodes on the imaged data are distinguished by the difference in brightness, the position data of the component electrodes is measured, and the mounting state of the component is inspected.

<Example> Hereinafter, an example according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of an inspection apparatus using the present invention.

In FIG. 1, 10 is a substrate to be inspected, 20 is an X-Y table for moving and positioning the substrate 10, 30 is an oblique illumination illumination that irradiates the substrate 10 with uniform white light from diagonally horizontally, and 40 is vertically An imaging camera takes an image of the substrate surface from above in the direction, and 50 is an image processing determination unit that processes the image taken by the imaging camera 40.

FIG. 2 is a schematic diagram when light is irradiated from an oblique direction onto a board and components. In FIG. 2, 60 is the board IO
For example, it is a square chip component mounted on top of a square chip.

FIG. 3 is an image taken by the imaging camera 40 of the board shown in FIG. 2, and 70 is a land provided on the top surface of the board.

The procedure of the method of the present invention will be explained below.

(2) Mount the substrate 10 on the XY table 20 and position it so that the object to be inspected is within the field of view of the imaging camera 40. In this case, the imaging camera 40 is installed directly above the substrate 10.

(2) The substrate 10 is illuminated obliquely by the oblique illumination 30.

(2) Distinguish the board and component electrodes on the image data based on the difference in brightness based on the difference in the diffusion characteristics of illumination light between the board 10 and the component electrodes, measure the position data of the component electrodes, and inspect the mounting state of the component.

The board surface consists of a land part that is a contact point with the electrode part of the component, a wiring pattern, and a board part without wiring.The land part is usually pre-coated with solder or soldered to prevent soldering defects. It is in the state of copper foil, and there is a protective film on the surface to protect the wiring pattern in areas other than the land area, so both have reflective characteristics close to mirror surfaces.

On the other hand, since the light from the oblique illumination 30 is irradiated onto the substrate surface from a direction close to the horizontal direction, most of the irradiated light is reflected in the opposite direction, and the imaging camera 40 which is perpendicular to the substrate surface is reflected.
There is very little light entering.

The component surface is composed of a body part made of plastic, etc., and an electrode part. Therefore, the body part has light reflection characteristics close to a mirror surface, and even if it has diffusion characteristics, the surface color is dark, and the electrode part has light reflection characteristics. However, it also has the property of diffusing light, and the surface color is bright, close to white, so much of the diffused light from the electrode section enters the imaging camera 40.

FIG. 3 shows an image taken of the board/component that is obliquely illuminated in this way. As can be seen from FIG. 3, the shaded areas are areas where much light enters the imaging camera 40 and have high brightness, and the other areas are areas with low brightness. That is, as can be seen from FIG. 3, since the electrode portion of the component appears bright and the other parts appear dark, the image processing judgment unit 50 binarizes the image based on the brightness level and calculates the center of gravity position of the high brightness part. This allows the position of the electrode section to be measured and inspected.

The inspection method of the present invention is not limited to the above embodiment.

In other words, as an example of determination, the center position of the electrode on the land is not on the land, or the position of the component is calculated based on the average of the center positions of all the electrodes of the component, and the determination is made based on the amount of position deviation from the predetermined position. There are two methods: one method to determine the area of the electrode on the land, and another method to determine it based on the area of the electrode on the land. Although square chip parts have been described as turning, the same inspection as described above is also possible for molded parts, ICs, and the like.

Regarding equipment examples, the camera and image processing judgment unit need only be able to recognize changes in brightness regardless of whether it is black and white or color, and oblique lighting can be round if it is lighting that emits light almost uniformly in the diagonal horizontal direction. In addition to fluorescent lamps, a light source that combines straight tube fluorescent lamps in a square shape, or a method that uniformly irradiates light from a halogen lamp using a ring fiber or the like may be used.

<Effects of the Invention> As explained above, according to the present invention, components can be automatically mounted using simple lighting equipment without using a light cutting method that irradiates slit light or a method that irradiates laser light onto components. Inspection has become possible, and it has become possible to provide a new method for recognizing component mounting on printed circuit boards that is highly accurate, reduces product costs, facilitates equipment maintenance, and quality control.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an inspection device using the present invention, Fig. 2 is a schematic diagram of a case where light is irradiated from an oblique direction to a board and components, and Fig. 3 is an image of the board shown in Fig. 2. An image captured by the camera 40 is used. lO...Printed circuit board 20...X-Y table 30...Oblique illumination 40...Imaging camera 50...Image processing determination section 60...Square chip parts 70... ···land

Claims (1)

[Claims] (1) A method for recognizing the mounting state of components mounted on a printed circuit board, in which an image of the board illuminated from an oblique direction is captured by an imaging camera installed perpendicularly to the board surface, and the board and components are A print that is characterized by distinguishing the substrate and component electrodes on imaged data by differences in brightness based on differences in the diffusion characteristics of illumination light of the electrodes, and inspecting the mounting state of the component by measuring position data of the component electrodes. A method for recognizing component mounting on a board.