JPH0629861B2 - Wiring pattern detection device on printed circuit board - Google Patents

Description

TECHNICAL FIELD The present invention erroneously detects at least scratches and discoloration on a wiring pattern and a thin film residual defect between the wiring patterns in a printed circuit board having a wiring pattern formed on a base material. The present invention relates to a wiring pattern detection device on a printed circuit board that detects a defect in a wiring pattern with high reliability without performing the above.

[Conventional technology]

For example, in order to detect the presence or absence of a defect in a wiring pattern formed on the surface of a printed circuit board or the like, a reflection type detection device as shown in FIG. 1 has been generally used conventionally.

The conventional wiring pattern detection apparatus includes a high-intensity light source 11 for irradiating a wiring surface 2 of a printed circuit board (or a ceramic substrate) 1 with light 31, a condenser lens 21, a half mirror 23, and the wiring surface 2 described above. The detector 13 for detecting the reflected light 45 from and the imaging lens 25 for forming a wiring pattern image on the detector 13 are provided from the wiring pattern 3 on the wiring surface 2 of the printed circuit board 1. Compared with the reflected light 45, the reflected light from the surface of the base material 4 is closer to the dark level, so that this is utilized to perform binarization to detect the wiring pattern.

[Problems to be Solved by the Invention]

FIG. 2 shows an example of a printed circuit board which is a symmetrical object.
The wiring pattern 3 is formed on the wiring surface 2 of the base material 4.

In the printed circuit board 1 of this example, a normal scratch 5 and a discolored portion 7 are formed as a wiring pattern on the wiring pattern 3, and residual copper 6 is proudly present in the wiring pattern.

The cross section AA passing through the scratch 5 is shown in FIG. 3 (a), the cross section BB passing through the residual copper 6 is shown in FIG. 3 (b), and the cross section CC passing through the discolored portion 7 is shown.
Sections are shown in FIG. 3 (c), respectively.

The conventional wiring pattern detector shown in FIG.
When the printed circuit board 1 having a defect as shown in the figure is inspected, it is erroneously detected as a disconnection although the scratches 5 and the discolored portion 7 have a wiring pattern and are functionally normal. Further, although the residual copper 6 is a defect that short-circuits the patterns, the surface of the residual copper looks dark so that it cannot be detected as a defect.

The state of erroneous detection by the conventional device (FIG. 1) described above is
Next, FIG. 4 will be described. The horizontal axis of this figure shows the position, and the vertical axis shows the voltage photoelectrically converted by the detector 13. The voltage V ₀ indicates the level of the through hole 8, that is, the dark level, the voltage V ₁ indicates the level of the base material 4, the voltage V ₂ indicates the level of the wiring pattern 3, and the voltage V ₃ indicates the saturation level of the detector 13. The voltage VT indicates the threshold level. As for the scratch 5, as shown in FIG. 4 (a), the abnormally strong specular reflection light from the scratch 5 enters the detector 13, and the detector 13 reaches the saturation voltage V ₃ to cause the blooming phenomenon to cause A '. The position is a voltage that goes up and down with respect to the threshold level VT and is detected as an abnormality. As shown in FIG. 4 (c), the discoloration portion 7 has a low light reflectance of the discoloration portion 7, so that the threshold level VT is lower than the voltage V ₂ corresponding to the original wiring pattern 3. Only the voltage V ₅ is obtained and the position of C ′ is erroneously detected as if the wiring pattern 3 does not exist, that is, if the wiring is broken. Copper 6
As shown in FIG. 3 (b), since the thickness is smaller than that of the normal wiring pattern 3 and the surface reflectance is low, the voltage is lower than the voltage V ₂ corresponding to the original wiring pattern 3 and the threshold voltage is low. Only the voltage V ₄ lower than the level VT is obtained, and the position of B ′ is detected as if the residual copper 6 does not exist.

Further, in the case of a so-called solder pattern in which the surface of the wiring pattern 3 is made of bright solder plating, abnormally strong specular reflection light that shines vividly enters the detector 13 because of the luster, so that the scratch 5 exists on the wiring pattern 3. A phenomenon similar to the case occurs, and although the printed circuit board 1 is normal, it is detected as an abnormality, so that there is a problem that the conventional pattern detection device as shown in FIG. 1 cannot accurately detect the pattern. It was

An object of the present invention is to solve the above-mentioned problems of the prior art in a printed circuit board having a wiring pattern formed on a base material,
The negative pattern of the wiring pattern is detected by the binary image signal without detecting the defect or the discoloration on the wiring pattern as an abnormality and the thin film residual defect which is a defect as the printed circuit board is not overlooked to detect the defect of the wiring pattern. An object of the present invention is to provide a wiring pattern detection device on a printed circuit board that can be detected with high reliability.

[Means for Solving the Problems]

The present invention, in order to achieve the above object, a laser light source,
Fluorescence excitation light selection / irradiation means for selecting fluorescence excitation light of a wavelength having a large fluorescence excitation ability from the light emitted from the laser light source and irradiating the surface of a printed board on which a wiring pattern is formed on a base material substantially vertically. And a scanning means for relatively two-dimensionally scanning the fluorescent excitation light and the printed circuit board, and a substrate of the printed circuit board excited by the fluorescent excitation light selectively irradiated by the fluorescent excitation light selecting / irradiating means. Is received and guided by the fluorescent light emitted from the printed circuit board, and is inclined with respect to the vertical irradiation optical axis so that specular reflection light of the excitation light from the surface of the printed circuit board does not enter, and is symmetrical with respect to the vertical irradiation optical axis. And a fluorescent light collecting optical system arranged in a plurality of directions, and the light guided by the fluorescent light collecting optical system is shielded from reflected light due to excitation light from the surface of the printed circuit board to emit light from the base material of the printed circuit board. Means for separating the fluorescent light, a detector for detecting the fluorescent light separated by the separating means and converting it into a signal, and a print detected by the scanning means by being two-dimensionally scanned. Binarization to detect the image signal of fluorescence generated from the substrate of the substrate with a desired threshold value and detect at least scratches and discoloration on the wiring pattern and thin film residual defects between the wiring patterns at the same dark level as the wiring pattern. Circuit, and detects a negative pattern of a wiring pattern without erroneously detecting at least scratches and discoloration on the wiring pattern and residual thin film defects between the wiring patterns by a binarized image signal obtained from the binarization circuit. It is a wiring pattern detection device on a printed circuit board, which is configured to be obtained. Further, the present invention is characterized in that, in the wiring pattern detecting device on the printed circuit board, the fluorescence focusing optical system is configured by an optical fiber bundle.

[Action]

With the above configuration, a laser beam is irradiated almost perpendicularly to a printed circuit board having a wiring pattern formed on the base material, and weak fluorescence generated by being excited by the base material can be intensified. The fluorescent light condensing optical system is tilted with respect to the vertical irradiation optical axis so that the specularly reflected light reflected from it does not enter, and is arranged symmetrically with respect to the vertical irradiation optical axis in a plurality of directions to collect the fluorescent light. The fluorescence is not generated in the optical system itself, and only the weak fluorescent image can be separated by the separating means so that at least scratches and discoloration on the wiring pattern and thin film residual defects between the wiring patterns are made to be the same dark level as the wiring pattern. As a result, a negative image of a wiring pattern is detected by binarizing a signal of a fluorescent image generated from a substrate of a printed circuit board detected by a detector with a desired threshold value. Ri without erroneously detecting the thin residual defects between scratches and discoloration, as well as the wiring pattern on the wiring pattern, a defect of the wiring pattern can be detected with high reliability.

〔Example〕

An embodiment according to the present invention will be described below with reference to FIGS.

As shown in FIG. 7, in a printed board 1 having a wiring pattern 3 formed on a base material 4, a printed board for obtaining a negative pattern of the wiring pattern by detecting an image of fluorescence generated from the base material 4 containing an organic substance. As shown in FIG. 5, for example, the above wiring pattern detecting device has a fluorescence excitation laser beam 34 having a wavelength of 300 nm to 460 nm.
A laser light source 16 for irradiating the laser beam, a beam expander 17 for expanding the fluorescence excitation laser beam 34 emitted from the laser light source 16, and a rotating mirror 18 for deflecting and scanning the fluorescence excitation laser beam expanded by the beam expander 17. And a scanning for irradiating the surface of the printed circuit board 1 having the wiring pattern 3 formed on the substrate 4 with the fluorescence excitation laser beam reflected and scanned by the rotating mirror 18 so that the spot light is irradiated almost vertically. The surface of the printed circuit board 1 so as to efficiently collect and guide the fluorescence generated by the lens 19 and, as shown in the drawing, excited by the fluorescent excitation laser spot light from the substrate 4 containing the organic substance of the printed circuit board 1 to the detector. Tilted with respect to the vertical irradiation optical axis by the scanning lens 19 so that the regular reflection light of the excitation light from
Further, an optical fiber bundle 20 formed by bundling a large number of optical fibers arranged in a plurality of directions symmetrically with respect to the vertical irradiation optical axis.
And a filter that cuts (shields) the excitation light mainly diffused and reflected on the surface 2 of the wiring pattern of the printed circuit board 1 and the surface of the base material 4 and enters the optical fiber bundle 20, and transmits only the fluorescence generated from the base material 4. 24 and the filter 2
And a photomultiplier 15 which is a detector for receiving the fluorescence transmitted through 4 and converting it into a signal.

The filter 24 is the wiring pattern 3 of the printed circuit board 1.
Is a separating means for shielding the reflected light in the wavelength range of the excitation laser light 32 which is mainly diffused on the surface 2 of the above, and transmitting and separating only the fluorescence excited by the base material 4, for example, shown in FIG. As described above, the yellow filter Y50 is generally called, which reflects light having a wavelength of 500 nm or less and transmits fluorescence having a wavelength of 500 nm or more.

The filter 2 is guided by the optical fiber bundle 24.
The fluorescence emitted from the base material 4 that has passed through 4 is imaged on the light-receiving surface of the photomultiplier 15, and by the scanning of the fluorescence excitation laser spot light by the rotating mirror 18 and the scanning of the printed board 1 traveling. Two-dimensionally scanned and printed from the photomultiplier 15 to the printed circuit board 1.
The image signal of the negative pattern of the wiring pattern 3 is obtained.

That is, the fluorescence excitation laser beam 34 having a limited wavelength in which fluorescence is easily emitted from the base material 4 is emitted from the laser light source 16, expanded by the beam expander 17, and expanded by the beam expander 17. The rotating mirror 18
While deflecting and scanning the surface of the printed circuit board 1 in a predetermined direction, the scanning lens 19 makes spot light to irradiate the surface of the printed circuit board 1. Then, the fluorescent excitation laser spot light excites the base material 4 containing the organic substance to generate fluorescence, and the wiring pattern 3 on the base material does not generate fluorescence. The excitation light specularly reflected by the surface of the printed circuit board 1 returns substantially vertically, and the optical fiber bundle 20
Will not be incident on. On the other hand, the fluorescence generated from the base material 4 and the light diffusedly reflected on the surface of the printed board 1 are collected by the optical fiber bundle 20 as the combined light 44, and the transmittance of the light in the wavelength region of the fluorescence excitation laser light is 0%. Then, it is detected by the photomultiplier 15 which is a detector through the filter 24 which transmits only fluorescence.

Therefore, two-dimensional scanning is performed by scanning the fluorescent excitation laser spot light by the rotating mirror 18 and scanning by the traveling of the printed circuit board 1 to obtain an image signal of the negative pattern of the wiring pattern 3 of the printed circuit board 1 from the photomultiplier 15. To be

As described above, since it functions as a wiring pattern detecting device on the printed circuit board for detecting the fluorescence generated from the base material 4, the normal scratches 5 or the like as the wiring pattern existing on the wiring pattern 3 shown in FIG. There is no influence of the discoloration part 7,
Further, even if the wiring pattern has gloss, the negative pattern of the wiring pattern can be detected without any problem. Further, when residual copper (thin film residual defect) 6 having a small reflectance is present on the surface of the base material 4 as shown in FIG. 2, the fluorescence emitted from the base material 4 is blocked, and the fluorescence of that portion is detected. However, the dark level is almost the same as that of the wiring pattern portion, and it is detected as having a defect because it is different from the reference wiring pattern. These states will be described below with reference to FIG. 8 showing the detection results. That is, in FIG. 8, as in FIG. 4, the horizontal axis indicates the position, and the vertical axis indicates the voltage photoelectrically converted by the photomultiplier 15 as the detector. The voltage V ₀ indicates the level of the through hole 8, that is, the dark level, the voltage V ₆ indicates the dark level of the wiring pattern, the voltage V ₇ indicates the bright level of the base material 4, and the voltage VT is a threshold value that is a desired threshold value. Indicates the level. In addition, each figure of (a), (b), (c) of FIG.
Similar to FIGS. (A), (b), and (c), the photomultiplier 15 as a detector captured each of the scratch 5, the residual copper 6, and the discolored portion 7 shown in FIGS. 2 and 3, respectively. It shows a detection result. The wound 5, as shown in Figure 8 (a), since the fluorescence is not detected, the position of the A 'becomes a dark level voltage V _6, is normally detected as a wiring pattern is lower than the threshold level VT . With respect to the discoloration 7, as shown in Figure 8 (c), the position of C 'because fluorescence is not detected becomes a dark level voltage V _6, is normally detected as a wiring pattern is lower than the threshold level VT It For residual copper 6, see Fig. 8.
As (b), the position of the so fluorescence is not detected B 'becomes a dark level voltage V _6, is lower than the threshold level VT, is detected as an abnormal By differs from the reference wiring patterns, copper remaining The existence of 6 will be recognized.

Further, in the printed circuit board 1, even in the case where the surface 2 of the wiring pattern 3 is made of bright solder plating, so-called solder pattern, detecting fluorescence of the portion of the base material 4 in FIG. 2 has been described in detail above. Since there is no difference from the embodiment, the wiring pattern can be accurately detected.

[Effects of the Invention] As described in detail above, according to the present invention, a printed circuit board having a wiring pattern formed on a base material is irradiated with laser light substantially perpendicularly and is excited by the base material. The fluorescent condensing optical system can be tilted with respect to the vertical irradiation optical axis so that weak fluorescence can be strengthened, and further, specular reflection light reflected from the surface of the printed circuit board does not enter, and with respect to the vertical irradiation optical axis. The fluorescent light condensing optical system itself is arranged symmetrically in a plurality of directions so as to eliminate the generation of fluorescence, and at least the weak fluorescent image can be separated by the separating means so that at least scratches and discoloration on the wiring pattern and wiring The thin film residual defect between the patterns is set to the same dark level as the wiring pattern, and as a result, the signal of the fluorescence image generated from the substrate of the printed circuit board detected by the detector is binarized with a desired threshold value By detecting the negative pattern of the wiring pattern, it is possible to detect wiring pattern defects with high reliability without erroneously detecting scratches and discoloration on wiring patterns and thin film residual defects between wiring patterns. Play.

[Brief description of drawings]

FIG. 1 is a side view of a conventional wiring pattern detecting device, FIG. 2 is a plan view of a printed circuit board, and FIG. 3 (a) is A- of FIG.
Sectional view A, FIG. 3B is a sectional view taken along line BB in FIG. 2, and FIG.
(c) is a cross-sectional view taken along the line CC of FIG. 2, and FIGS. 4 (a), (b), and (c) are diagrams showing the detection results of the conventional wiring pattern detection device, FIG. 5, and FIG. 6, respectively. FIG. 7 is a diagram showing characteristics of filters and the like used in the embodiment of the present invention, FIG. 7 is a side view showing an embodiment of a wiring pattern detecting device on a printed circuit board of the present invention, and FIGS. 8 (a) and 8 (b). , (c) are diagrams showing detection results in the embodiment shown in FIG. 7, respectively. 1 ... Printed circuit board, 3 ... Wiring pattern, 4 ... Base material, 5 ...
Scratches, 6 ... residual copper (thin film residual defects), 7 ... discolored part, 8 ... through hole, 15 ... photomultiplier, 16 ... laser light source, 17 ... beam expander, 18 ... rotating mirror, 19 ... scanning lens, 20… optical fiber bundle, 24… filter.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-56-82544 (JP, A) JP-A-53-45180 (JP, A) "How to use a microscope" 5th edition, Masao Ishizawa, Katsumi Tanaka, Nobu Leather tassel P165-169

Claims (2)

[Claims] 1. A laser light source and fluorescent excitation light of a wavelength having a large fluorescence excitation ability are selected from light emitted from the laser light source, and are substantially perpendicular to a surface of a printed circuit board having a wiring pattern formed on a base material. Fluorescence excitation light selection and irradiation means for irradiation,
Scanning means for relatively two-dimensionally scanning the fluorescent excitation light and the printed circuit board, and excitation from the fluorescent excitation light selectively irradiated by the fluorescent excitation light selecting / irradiating means to generate from the substrate of the printed circuit board. Receives and guides the emitted fluorescence,
And tilted with respect to the vertical irradiation optical axis so that the regular reflection light of the excitation light from the surface of the printed circuit board does not enter,
In addition, a fluorescent light condensing optical system is arranged symmetrically with respect to the vertical irradiation optical axis, and light reflected by the excitation light from the surface of the printed circuit board is shielded from the light guided by the fluorescent light condensing optical system. A separating means for separating the fluorescence emitted from the base material of the printed circuit board, a detector for detecting the fluorescence separated by the separating means and converting it into a signal, and two-dimensional scanning by the scanning means. , The image signal of the fluorescence generated from the substrate of the printed circuit board detected by the detector is binarized by a desired threshold value, and at least scratches and discoloration on the wiring pattern and thin film residual defects between the wiring patterns are the same as those of the wiring pattern. A binarization circuit for detecting a dark level and detecting at least scratches and discoloration on wiring patterns and between wiring patterns by a binarized image signal obtained from the binarization circuit. Without erroneously detecting the thin residual defects, the wiring pattern detection device on the printed circuit board, characterized by being configured to obtain detect the negatives pattern of a wiring pattern. 2. The wiring pattern detecting device on a printed circuit board according to claim 1, wherein the fluorescence focusing optical system is composed of an optical fiber bundle.