JPH0331219B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a pattern detection method for a printed wiring board, and in particular, for a printed wiring board having a wiring pattern on two upper and lower sides, detecting the short,
The present invention relates to a pattern detection method for a printed wiring board for inspecting disconnections, irregularities, etc.

[Prior art]

Since a pattern is usually two-dimensional, it is common to treat it as a two-dimensional pattern when detecting it.
Conventionally, in pattern detection of printed wiring boards,
Methods such as detecting a pattern by capturing the transmitted light or reflected light from the substrate, or detecting the pattern by using the difference in the intensity of reflected light between the pattern and the base material are adopted. However, if the printed wiring board is thick or has multiple layers, it is impossible to detect the pattern using transmitted light. Therefore, it is necessary to utilize reflected light. However, in cases where the pattern is uneven or uneven, the intensity of reflected light varies greatly, making accurate pattern detection difficult.

Therefore, the present applicant previously wrote in "Pattern Detection Method for Printed Wiring Board" (Japanese Patent Application No. 146425-1982),
The conductive wiring pattern on the printed wiring board is irradiated with light from diagonally and from above, and the surface area of the conductive wiring pattern is detected by imaging the light reflected upward from the wiring pattern by the irradiated light. We are proposing a method. This makes it possible to correctly detect the shape of a pattern that has a sloped area with wide lateral sides, but it also has the disadvantage that there are scratches and stains on the pattern surface and its periphery, which are detected as defects. It was hot. This point will be further explained.

FIG. 1 is a sectional view of an inner layer pattern of a printed circuit board, which has wiring patterns on both sides, which is the object of the present invention. In the figure, reference numeral 1 indicates an inner layer pattern, in which an upper surface pattern 1a and a lower surface pattern 1b made of a conductive material are formed on the upper and lower surfaces of a thin substrate 2 of about 0.2 mm in thickness and made of a glass epoxy material. A multilayer printed circuit board is constructed by stacking a plurality of inner layer patterns 1 as shown in the figure, but since the above-mentioned pattern defects sometimes exist on the front and back surfaces of each inner layer pattern 1, optical We have to do pattern detection and remove it.

FIG. 2 is a diagram for explaining the pattern detection method previously proposed by the applicant, in which the inner layer pattern 1
The upper surface part is equipped with a semi-transparent mirror 5 that reflects the light P from the illumination source in the right angle direction, a condensing lens 3, and an imager 4 for capturing a pattern. At the same time, the pattern 1a is irradiated with the light Q from an oblique direction, and the pattern 1a is focused on the lens 3.
The pattern imager 4 forms an image, detects the pattern using the pattern imager 4, and outputs the detected signal 6 to the processing circuit.

According to the configuration shown in Figure 2, there are problems such as the need to detect patterns on the front and back sides separately and the fact that there are multiple light irradiation directions. Therefore, as shown in Figure 3, transmitted illumination light R is used. , inner layer pattern 1
It is also possible to irradiate from the bottom surface, but in this case, the bottom surface pattern will be reflected in addition to the top surface pattern.
Unable to detect patterns on the top surface only. Figure 4 shows
This is a waveform diagram of the detection signal 6 obtained by the method shown in FIG. 3, in which the portion corresponding to the upper surface pattern 1a is clearly imaged as black, but the portion corresponding to the lower surface pattern 1b is darker than the upper surface pattern 1a. It is clearly detected as black. According to the transmitted illumination method, the patterns on the upper surface and the lower surface are detected at the same time, so the problem remains that the upper surface pattern in the portion hidden by the lower surface pattern cannot be inspected. Also,
Since the bottom pattern is blurred, stable pattern inspection cannot be performed.

[Purpose of the invention]

The object of the present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a printed circuit board having wiring patterns on both sides of the board without being affected by the surface condition such as discoloration of the wiring pattern. It is an object of the present invention to provide a pattern detection method for a printed wiring board, which enables accurate and stable detection of a wiring pattern without being affected by the wiring pattern.

[Summary of the Invention] That is, in order to achieve the above-mentioned object, the present invention provides illumination light beams from one side of a substrate having wiring patterns formed on both sides from at least four directions oblique to the direction perpendicular to the substrate surface. The light is irradiated so that it enters the board from both sides of the wiring pattern on the one side, that is, so as not to hit the wiring pattern on the one side, and is transmitted while being scattered within the board (due to the light scattering effect). A pattern detection method for a printed wiring board, characterized in that a light image emitted from the other side of the board is captured by an imaging means, and only the wiring pattern provided on the other side of the board is detected as a negative pattern image. be.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 5 to 8. FIG. 5 is a diagram when a substrate having wiring patterns on both upper and lower surfaces is irradiated with light for pattern detection, and upper surface patterns 1a and 1b are formed on the upper and lower surfaces of the substrate 2. In FIG. On the lower surface side where the lower surface pattern 1b is wired, the irradiation light S can be obliquely irradiated at an angle θ from a position where the lower surface pattern 1b is not irradiated. As a result, if transmitted light is detected on the upper surface of the substrate 2, no light is detected at all because the upper part of the upper surface pattern 1a is blocked, but nothing on the substrate between the upper surface patterns 1a is blocked. Since there is no object, the incident light S is diffusely reflected inside the inner layer pattern 1, and the light is outputted to the upper surface as light S'. That is, the sixth
As shown in the waveform diagram in the figure, the detection signal 6 captured by the imager and outputted includes the upper surface pattern 1a.
The portion of the lower surface pattern 1b is detected as a low voltage level, and the portion of the lower surface pattern 1b is detected as a high voltage level. In order to reliably detect this level difference,
A binarization level Va is set, and only the upper surface pattern can be accurately detected depending on whether it is lower or higher than the level Va.

FIG. 7 shows a specific example of the configuration of the apparatus, in which 7 and 7' are substrates on which patterns to be inspected are formed, each having a pattern of the same shape. 8, 8' are lenses provided correspondingly,
Reference numerals 9 and 9' denote imagers that detect patterns obtained through lenses 8 and 8', and 10 a pattern comparison circuit that compares detection signals 6 and 6' obtained from the imagers 9 and 9'. Further, the substrates 7 and 7' are fixed to a hollow table 11, and a lamp 1 is placed inside this table 11.
2 and 13 are provided so as to illuminate the lower surface of the substrate 7 from an oblique direction. This configuration is also the same for the portion that irradiates the lower surface of the substrate 7'. The table 11 is attached to the X-Y stage 14, and the substrate 7,
Slide along the pattern shape of 7'.
In addition, in FIG. 7, two lamps 12 and 13 are provided as light sources for illuminating the lower surfaces of the substrates 7 and 7', but in reality, as shown in FIG.
The light is irradiated by three lamps 12, 13, 15, and 16.

According to the same configuration, as can be seen from the above explanation, the substrates 7 having wiring patterns of the same shape,
7' is mounted on the perforated surface of the table 11, and the lower surface is irradiated with the lamps 12, 13, 15, 16. In this case, the substrate 7,
7' are aligned with each other, the corresponding parts of the two patterns are detected by the imaging bases 9 and 9', and the 6th pattern is detected.
A detection signal as shown in the figure is obtained. Then, the detection signals 6 and 6' are compared by a pattern comparator 10,
The mismatched portion of the two patterns is called a defect, i.e.
It is determined that there are scratches, dust, etc.

The table 11 slides on the XY stage 14 and inspects the entire wiring pattern of the substrates 7, 7'.

The specific structure of the pattern comparator is disclosed in Japanese Patent Application No. 40328/1983, which has already been filed.

〔Effect of the invention〕

As is clear from the above-described embodiments, in the method for detecting a printed circuit board pattern according to the present invention, when detecting a pattern by transmitting irradiation of a circuit board pattern having wiring patterns on both sides, the lower surface side pattern is detected from the lower surface side of the substrate. Since the pattern is detected by irradiating only the pattern on the top surface of the detection side by irradiating it from an oblique direction without irradiating the light on the surface of the substrate, it is possible to clearly and stably detect only the pattern on the detection side of a board that has wiring patterns on both sides. can be detected. Further, when automatically inspecting a pattern, there is no need to take special precautions to prevent discoloration, scratches, etc. on the pattern surface, which improves the efficiency of the inspection process and is also economical.

[Brief explanation of drawings]

FIG. 1 is a side cross-sectional view of a board with wiring patterns on both sides, which is the object of the present invention, and FIGS.
The figure is an overall schematic configuration diagram of an apparatus for detecting a pattern using the pattern detection method previously developed by the applicant, FIG. 4 is a detection signal waveform diagram when a pattern is detected using the method shown in FIG. The figure is a principle diagram for explaining the pattern detection method according to the present invention, and is a side sectional view of the substrate, FIG. 6 is a detection signal waveform diagram when pattern is detected by the method of FIG. 5, and FIG. FIG. 8 is a partial plan view of FIG. 7. 1... Inner layer pattern, 1a, 1b... Wiring pattern, 2, 7, 7'... Board, 3, 8, 8'... Lens, 4, 9, 9'... Imager, 6... Detection signal ,
10...Pattern comparison circuit, 11...Table,
12, 13, 15, 16...lamp, 14...X
-Y stage.

Claims (1)

[Claims] 1. Illumination light flux enters the substrate from both sides of the wiring pattern on the one side from at least four diagonal directions inclined with respect to the perpendicular direction of the substrate surface from one side of the substrate with wiring patterns formed on both sides. A light image is captured by an image pickup means, and a light image that is scattered and transmitted through the board and then emitted from the other side of the board is used to capture only the wiring pattern provided on the other side of the board as a negative pattern image. A method for detecting a pattern on a printed wiring board, the method comprising: detecting a pattern on a printed wiring board;