JPS6168676A - Test method of packaged printed board part - Google Patents

Abstract

PURPOSE:To test defects such as packaging dislocation by coating a printed board with a material obtained by mixing a solder resist with a fluorescent material or applying a paint mixed with a fluorescent material after coating a solder resist. CONSTITUTION:A printed board 1 to be tested is fixed with a jig 2 on a test stand 3, and ultraviolet light is irradiated thereon from a ultraviolet light lamp 4. The image of said printed board 1 formed with fluorescence generated by said ultraviolet light is picked up by a television camera 5, inputted and processed in a picture processing circuit 6. A printed board 8 is constituted with a substrate main body 10 and a fluorescence mixed solder resist 11 coated thereon. It is assumed that a ultraviolet light beam 12 is irradiated on the upper surface of the printed board 1 to be tested. At this time since a part 9 does not exist, at the part where said resist 11 is exposed the mixed fluorescence absorbs the ultraviolet light beam 12 to emit a fluorescence 13.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention involves inputting an image of a printed circuit board to be inspected using an imaging means such as a television camera, and determining the shape of a mounted component using an image processing means such as an electronic circuit or a microprocessor. -Relates to a method for inspecting printed board mounted components that measures position, orientation, etc. and inspects for defects such as mounting misalignment.

[Prior art and its problems]

Conventionally, this type of printed board inspection method uses visible light as illumination light, and the reflected light of this illumination light on the printed board is imaged and converted into electrical signals with a television camera, etc., and the signal level of the board components and the signal of the component parts are By using electronic circuits, microprocessors, etc., to recognize the difference between the
A method is known in which the position and orientation are measured and determined to be acceptable if the position and orientation are within a predetermined tolerance range, and otherwise determined to be defective.

In order to measure the position and orientation of a component mounted on a printed board using this method, it is essential to recognize the boundary between the component part and the board part, that is, the outer shape of the component. Therefore, images must be taken with a television camera or the like under conditions such that the difference between the brightness level of the component part and the brightness level of the board component is as large as possible, that is, the contrast is good. However, the contrast of the target printed board under visible light is significantly poor depending on the parts. Therefore,
When the signal level difference between the board part and the component part is small, the boundary between the board part and the component part is unclear, making it difficult to measure the position and orientation of the part. For example, printed boards that are subject to this type of printed board inspection often have green solder resist applied to the board, but the difference between this signal level and the signal level of black components is extremely small. It was not possible to distinguish between the two, and therefore it was extremely difficult to measure the position and orientation of the black component.

The above-mentioned reasons are a bottleneck in automatic visual inspection of printed board mounted components, and as a result, the current situation has been to rely on visual inspection by testers, which has become a serious problem in terms of quality control of printed boards.

[Purpose of the invention]

In view of the above-mentioned drawbacks, it is an object of the present invention to provide a printed board component mounting inspection method that can measure the position and orientation of any component.

[Key points of the invention]

The gist of the present invention is to utilize the fluorescent action of a fluorescent agent due to ultraviolet rays as a means for improving the contrast of parts that have poor contrast under visible light.

In other words, when a fluorescent agent is mixed with solder resist and applied to a printed circuit board, and after parts are mounted, ultraviolet rays are irradiated.
The board parts emit visible fluorescence and have a high brightness, while the component parts do not emit fluorescence and have a low brightness. Therefore, good contrast can be obtained due to this brightness difference.

Therefore, by capturing this image with a television camera, the external shape of the component can be clearly recognized and defects such as mounting position deviation can be inspected. Furthermore, the same effect as described above can be obtained even when a paint containing a fluorescent agent is applied to the top surface of a normal solder resist.

[Embodiments of the invention]

A first embodiment of the invention is shown in FIG. The printed board 1 to be inspected is fixed to an inspection table 3 by a jig 2, and is irradiated with ultraviolet light from an ultraviolet lamp 4. An image of the printed board 1 to be inspected formed from the fluorescence emitted by the ultraviolet rays is captured by a television camera 5, and is input to an image processing circuit 6 and processed. The irradiation part is surrounded by a shielding plate 7 and is protected from ambient light.
The image processing circuit 6 has a configuration well known in the field of pattern recognition, and binarizes the image signal from the television camera 5 using a darkness value of a predetermined level, quantizes it, and stores it in a memory. The quality of the pattern imaged by the television camera 5 is determined by comparing the obtained information with previously stored information.

The process of image formation in the first embodiment of the present invention will be explained with reference to FIG. As shown in FIG. 2(a), the printed board 1 to be inspected consists of a printed board 8 and parts 9 (actually, there are a plurality of parts) mounted on the top surface of the printed board 8. moreover,
The printed circuit board 8 is composed of a circuit board body 10 and a fluorescent agent-containing solder resist 11 coated on its upper surface according to the present invention. . Assume that the upper surface of the printed board 1 to be inspected is now irradiated with ultraviolet rays 12. At this time, in the exposed portion of the solder resist 11 containing a fluorescent agent because the component 9 is not present, the incorporated fluorescent agent absorbs the ultraviolet rays 12 and emits fluorescent light 13. On the other hand, since there is no fluorescent agent on the surface of the component 9, no fluorescent light is emitted, and only the ultraviolet rays 12 are reflected. Next, when this image is scanned with an ordinary television camera 5 (shown in FIG. 1), the reflected ultraviolet rays 12 are not affected, but only the fluorescent light 13 is affected. Therefore, as shown in FIG. 2(b), the waveform of the image signal 14 corresponding to the cross section of FIG. Become. Therefore, if a certain threshold value 15 is set and the image signal is binarized depending on whether it is higher or lower than this level, a binary image as shown in Fig. 2(C) can be obtained.
A value signal 16 is obtained. If the binarization is performed over all scanning lines, a two-dimensional binary image 17 is obtained as shown in FIG. In Figure 3, the shaded area is the part to be inspected for one day (
(corresponding to component 9), and the others indicate the board portion 19.

In the binary image 17 of FIG. 3, a regular part part 20 is stored in advance in the image processing circuit 6 in correspondence with the part to be inspected part 18, and the more the two parts match, the more the part 9 It can be determined that it has been implemented correctly. Therefore, for example, when the area of the overlapping portion of both parts is S, and the preset minimum mold area is Sa+in, if S≧S rain then it is set as good, otherwise it is set as bad. This determination process is performed by the image processing circuit 6 shown in FIG.

The second embodiment of the present invention differs from the first embodiment in that an ultraviolet lamp 4 irradiates ultraviolet rays, a television camera 5 images the trends caused by the ultraviolet rays, and an image processing circuit 6 processes the images. Similarly, as shown in FIG. However, the method of applying the fluorescent agent is different from that in the first embodiment, and this method of application is shown in FIG.

In FIG. 4, the printed board 1 to be inspected is composed of a printed board 8 and a component 9 mounted on its upper surface. moreover,
The printed circuit board 8 is made up of a circuit board body 10, a solder resist 21 applied to its upper surface, and a fluorescent paint 22 applied to its upper surface.

That is, in the first embodiment, a fluorescent agent is added to the solder resist, but in the second embodiment, a fluorescent paint 22 is separately applied on top of the conventional solder resist 21.

Therefore, the image forming process is the same as in the first embodiment except that the fluorescent agent added to the fluorescent paint 22 emits fluorescent light. The imaging and processing process is also shown in Figure 2 (b
)(c) Since it is the same as that shown in FIG. 3, the explanation will be omitted.

〔Effect of the invention〕

In this invention, a fluorescent agent is mixed with the solder resist and applied to the printed circuit board, or a paint containing a fluorescent agent is applied after the solder resist is applied, so when UV rays are irradiated after the components are mounted, the board parts are exposed and become brighter. Therefore, the component part does not emit light and has a low brightness, and this difference in brightness provides good contrast. Therefore, by capturing this image with a television camera or the like, the external shape of the component can be clearly recognized and its position and orientation can be measured, making it possible to inspect defects such as mounting position deviation.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2(a) is a sectional view showing the process of image formation in the first embodiment of the present invention, and FIG. 2(b) is a sectional view showing the process of image formation in the first embodiment of the present invention. The image signal waveform of the corresponding cross section, the binarized signal waveform of the image signal in Fig. 2 (C) and G*' (b), Fig. 3 is a conceptual diagram showing the binarized image of the printed board, and Fig. 4 FIG. 7 is a cross-sectional view showing the process of image formation in a second embodiment of the present invention. 1. Printed board to be inspected 2. Jig, 3. Inspection table,
4. Ultraviolet light, 5. TV camera,
6... Image processing circuit, 7... Shielding plate, 8
・・Printed circuit board, 9・・Parts, 10・・
Substrate body, 11...Solder resist containing fluorescent agent, 12
...Ultraviolet light, 13..Fluorescence, 14..Image signal, 15..Threshold value 16..Binary signal,
17...Binary image, 18...Part to be inspected, 1
9... Board part 20... Regular parts part, 21... Solder resist, 22... Fluorescent paint.

Claims (1)

[Claims] 1) A printed circuit board to be inspected on which a component is mounted is imaged, and the image signal is processed by an image processing means to measure the position, orientation, etc. of the mounted component, thereby detecting the deviation of the mounting position, etc. A printed board component mounting inspection method for detecting defects in a printed circuit board, in which a fluorescent agent is applied onto the printed circuit board, and after the component is mounted, the printed board to be inspected is imaged by irradiation with ultraviolet rays, and the fluorescent agent is detected by an image processing means. A printed board component mounting inspection method characterized by recognizing the outer shape of a mounted component and measuring its position, orientation, etc. based on the difference in brightness between a board part coated with a chemical agent and a mounted component part. 2) A method for inspecting printed board component mounting according to claim 1, characterized in that a fluorescent agent is blended into a solder resist and applied onto the printed circuit board. 3) A printed board component mounting inspection method according to claim 1, characterized in that a paint containing a fluorescent agent is applied to the upper surface of a solder resist applied to a printed board. Board component mounting inspection method.