JPH0666534A - Soldering appearance inspection method - Google Patents

Abstract

PURPOSE:To control blinking of each ring-shaped light source speedily, transmit obtained image information speedily, and achieve a high-resolution detection. CONSTITUTION:Ring-shaped light sources 20a,..., 20c are placed in three steps at the upper part of a part to be inspected, at the same time a black and white camera 22 is laid out, each light source is allowed to blink at different timings successively, the image information obtained at each lighting timing is stored at corresponding frame memories 26a,..., 26, and then it is judged whether soldering is proper or not according to the image characteristics. In each ring- shaped light source, a number of light emitting diodes 32 are aligned in a downward channel-shaped cover material 30. An interlace scanning system is adopted. the ring-shaped light source lights up only at a half cycle where odd/even image pick-up times are superposed for exposing to the black and white camera, and then the odd/even image pick-up signal is transferred to a frame memory during a next one cycle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an optical pseudo three-dimensional soldering appearance inspection method. More specifically, it is obtained by lighting a plurality of ring-shaped light sources in a time-division manner and at each lighting timing. The present invention relates to a method of efficiently transferring and storing image information from a camera to a corresponding frame memory, and determining the quality of soldering from those image features. This inspection technique is useful for automatically determining the quality of the soldered state of the electronic component mounted on the printed wiring board.

[0002]

2. Description of the Related Art Various technologies have already been proposed for automatically inspecting the quality of the soldered state of electronic components mounted on a printed wiring board. Regarding the optical automatic soldering appearance inspection apparatus, it is said that a pseudo three-dimensional illumination system that can inspect from a three-dimensional (pseudo three-dimensional) viewpoint is predominant at present. Typical examples thereof include a time division illumination type and a color illumination type.

In the time-division illumination system, a plurality of stages of ring-shaped illumination means arranged in a dome shape are sequentially turned on / off to switch the illumination angle to illuminate a soldering portion, and an image is taken by an industrial television camera to perform image processing. (For example, JP-A-61-1
See Japanese Patent No. 293657). Here, as the illuminating means, a configuration is adopted in which a large number of optical fiber cables are attached to a dome-shaped holder for each stage, and a halogen lamp serving as a light source is arranged for each stage at the other end of the optical fiber cable. . Then, by blinking the light from the halogen lamp, a ring-shaped illumination light is projected on each stage. The images obtained at different lighting timings are stored in the frame memories respectively, and necessary image processing is performed to determine the quality of the soldered portion.

In the color illumination system, a color 3 which is composed of three ring-shaped light emitting bodies which emit red light, green light and blue light.
The soldering area is illuminated with a color ring illuminator, and a reflected light image is captured for each hue by a color television camera (see, for example, Japanese Patent Laid-Open No. 1-282410). In this case, the light amount is adjusted so that white light is obtained when the lights from the respective light emitters are combined. Therefore, it is not necessary to perform time-division control, and detection can be performed separately at the same timing.

[0005]

In the case of the conventional time division illumination system, it is time consuming and impractical to optically switch the ring-shaped illumination light by the halogen lamp. Further, in the normal method, it takes time to transmit image information to three frame memories per screen, and it is not possible to meet the current needs for speeding up. Incidentally, the time required for photographing by this method was on the order of seconds.

When a color single-plate CCD camera is used as a television camera in a color illumination system, the CCD cell portion is divided into three colors, so that the actual resolution is reduced to about half that of a monochrome camera. To do. Even if a three-color CCD is used, it is difficult to adjust the physical phase of the three-color CCD, and it is very difficult to obtain a resolution equivalent to that of a monochrome camera.

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, to control the blinking of each ring-shaped light source at high speed, to transmit the obtained image information at high speed, and to detect with high resolution. It is to provide a soldering appearance inspection method.

[0008]

According to the present invention, a plurality of ring-shaped light sources are arranged so that the incident angles are different from each other with respect to a soldering portion, and a television camera is arranged so as to face the soldering portion. A soldering visual inspection method that sequentially turns on and off the light source at different timings in time, stores the image information obtained at each lighting timing in the corresponding frame memory, and determines the quality of soldering from those image features. is there. In the present invention, in the above configuration, the ring-shaped light source has a structure in which a large number of light-emitting diodes are arranged in a ring shape, the television camera is a CCD single-plate black-and-white camera, and an interlace scanning system is adopted for image pickup. The ring-shaped light source is turned on and the monochrome camera is exposed only for a half cycle in which the odd screen image capturing time and the even image capturing time are superimposed, and the odd screen image capturing signal and the even screen image capturing signal are transferred to the frame memory during the next one period. And, there is a feature in that point.

Preferably, three types of ring-shaped light sources whose diameters increase in order are arranged in the upper, middle and lower stages so that the central axes coincide with each other, and a black and white camera is installed on the central axis. Each of the ring-shaped light sources uses a device having a structure in which a large number of light emitting diodes are closely aligned downward in a channel-shaped cover member having an open lower end.

[0010]

The ring light source consisting of an array of a large number of light emitting diodes can be blinked electrically at high speed. In addition, the pixel resolution is improved by using a monochrome camera. Furthermore, the odd screen image capturing time and the even image capturing time of the camera are deviated by a half cycle, but by utilizing the overlapping of the half cycle and turning on the ring-shaped light source at the common timing, the CCD on the same condition Exposed on odd / even scan screen. Further, the image pickup signal at that time can be divided into odd / even image signals and output during the next one cycle, and the image signal transfer time is about 0.
It is reduced to 13 seconds.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic block diagram of a soldering appearance inspection apparatus used in the present invention. Three types of ring-shaped light sources 20a, 20b, 20 having diameters that increase in order are provided above the electronic component 12 mounted on the printed wiring board 10 that is the object to be inspected.
c are arranged in the upper, middle, and lower stages so that their central axes coincide with each other, and one black and white camera 22 is further arranged on the central axes. The image signal from the monochrome camera 22 is sent to the corresponding frame memories 26a, 26b and 26c for three images via the image processor 24. Further, the turning on / off operation of each of the ring-shaped light sources 20a, ..., 20c is synchronized with the image pickup operation by the monochrome camera 22,
It is controlled by the switching control circuit 28. Here, each of the ring-shaped light sources 20a, ..., 20c has a structure in which a large number of light-emitting diodes 32 are arranged in close proximity in a row downward in a channel-shaped cover member 30 having an open lower end.

One of the features of the present invention is that the array of a large number of light emitting diodes 32 is used as the light source and the monochrome camera 22 is used as the television camera. The reason for using the monochrome CCD black-and-white camera 22 is that the number of pixels is large and the resolution is advantageous. Further, the reason why the light emitting diodes are used for the ring-shaped light sources 20a, ..., 20c is that the response is fast and the structure is simplified.

The irradiation / inspection state of this apparatus is shown in FIG. First, only the upper ring-shaped light source 20a is turned on, an image at that time is captured by the monochrome camera 22, and the image information is stored in the corresponding frame memory 26a. Next, only the ring-shaped light source 20b in the middle stage and only the ring-shaped light source 20c in the lower stage are sequentially turned on, and the corresponding frame memories 26b, 26b,
The image information is stored in 26c. At this time, a representative image of the soldering portion 34 of the lead of the electronic component (LSI) 12 which is the object to be inspected is shown in FIG. From the left of the drawing, an upper light source image, a middle light source image, and a lower light source image. Image processing of these pieces of image information will determine the quality of the soldered portion.

Another feature of the present invention is that the imaging operation and the light source blinking operation are efficiently synchronized to shorten the imaging time. For the signal of the camera image, the interlace scanning (shown in FIG. 4) method, which has a good image quality with respect to the image information amount, is generally adopted. As shown in FIG. It is divided into screens of even scanning lines and transferred alternately. From FIG. 5, the time for imaging one screen is the odd screen imaging time (O1, ...) Or the even screen imaging time (E1,
...) It takes 2/60 seconds by itself, but it takes 3/60 seconds because both have to be combined to form a complete screen. Further, the odd screen image signals (o1, ...) Are transferred after the odd screen image pickup time, and the odd screen image signals (e1, ...) Are transferred after the even screen image pickup time. In general terms, the upper light source is turned on to capture the upper light source image in 3/60 seconds, then the light source is switched to the middle light stage and the middle light source image is taken from the next complete cycle. Finally, the light source is switched to the lower stage, and the lower stage light source image is taken from 9/60 seconds, and the three images are finished. 12 by the time the signal is completely transferred
/ 60 seconds (0.2 seconds).

The present invention also employs the interlace scanning method, but the image signal transfer method is different from that in the case of FIG. FIG. 6 shows the operation timing according to the present invention. The imaging times of the odd-numbered image scanning cells and the even-numbered image scanning cells on the area CCD of the monochrome camera are shifted by a half cycle, but the remaining half cycles are overlapped and are common. By lighting the light emitting diodes at this common timing, exposure can be performed on the odd / even scanning screen under the same conditions.

First, half of the odd screen image pickup time remains off, and the upper ring light source 20a is provided between Aa from the start of the even screen image pickup time to the end of the odd screen image pickup time.
Lights up. The image pickup signal at this time is an odd scan image signal,
Output at the timing of the even scan image signal. Since the time when the light source is off is dark, the light amount of the image charged in the CCD is a value that can be almost ignored, and most of the image pickup signals are when the upper ring-shaped light source 20c is turned on. Then B
The ring-shaped light source 20b in the middle stage is turned on between -b, and an image is taken by the middle-stage light source. Finally, the lower ring-shaped light source 20c is turned on between C and c to obtain an image by the lower light source. During this time, there is no need to forgo the unnecessary exposure time, and the time required to capture the three images is 8/60 seconds (about 0.13 seconds).

Although the ring-shaped light sources are arranged in three stages in the above embodiment, they may be arranged in two stages or four stages.

[0018]

As described above, according to the present invention, by combining a plurality of light sources in which a large number of light emitting diodes are arranged and a monochrome camera, blinking switching of each light source can be performed at high speed, and pixel resolution is high. High quality images can be obtained. Moreover, in the present invention, since the blinking operation of each light source and the image exposure time of the CCD cell are efficiently synchronized, the photographing time can be greatly shortened. For example, in the case of 3 images, it takes about 0.13 seconds, which is sufficient. Image signals can be transferred at a speed that can be used practically.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an example of a soldering appearance inspection device used in the present invention.

FIG. 2 is an explanatory diagram of the illumination / inspection operation.

FIG. 3 is an explanatory diagram of an image of a soldered portion by each light source.

FIG. 4 is an explanatory diagram showing a relationship between a camera image and scanning lines.

FIG. 5 is an output sequence diagram of a camera image.

FIG. 6 is an explanatory diagram of operation timings of image pickup and image signal transfer according to the present invention.

[Explanation of symbols]

 10 Printed Wiring Board 12 Electronic Components 20a, 20b, 20c Ring Light Source 22 Monochrome Camera 24 Image Processor 26a, 26b, 26c Frame Memory 28 Switching Control Circuit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location // H05K 3/34 W 9154-4E

Claims (2)

[Claims] 1. A plurality of ring-shaped light sources are arranged so that the incident angles are different with respect to the soldering portion, and a TV camera is arranged so as to face the soldering portion. In the method of sequentially turning on / off the light, storing the image information obtained at each lighting timing in the corresponding frame memory, and judging the quality of soldering from those image features, in the ring-shaped light source, a large number of light-emitting diodes are ringed. The TV camera is a black and white CCD single-panel camera, and the interlaced scanning method is used for imaging, and the ring-shaped light source is used only for a half cycle in which odd screen image capturing time and even image capturing time are superimposed. Soldering characterized by lighting and exposing to a black-and-white camera, and transferring the odd screen image pickup signal and the even screen image pickup signal to the frame memory during the next one cycle Appearance inspection method. 2. Three types of ring-shaped light sources whose diameters increase in order are arranged so that their central axes coincide with each other.
A device having a structure in which a black-and-white camera is installed on the lower axis and a black-and-white camera is installed on the central axis, and each of the ring-shaped light sources has a structure in which a large number of light-emitting diodes are closely aligned downward in a channel-shaped cover member having an open lower end Item 1. The soldering appearance inspection method according to Item 1.